CAUTION: Organs at Work - The Heart

Prologue
The body is made up of atoms and molecules that must follow the laws of nature.  Those laws demand that each of its trillions of cells must have enough energy and different chemicals to live, grow and work properly.  To this end the body has a cardiovascular system that sends blood to the cells to give them what they need.  Previous articles have shown that to have enough blood volume to accomplish this task involves having enough water and sodium in the right places.  Also, to maintain the proper resting membrane potential for heart, nerve and muscle function requires the body to control its potassium as well.  Now we need to look at how the body moves the blood to where it needs to go.  After all, blood has mass and therefore like all matter requires energy to be moved against the natural forces of inertia, friction and gravity.  To follow the rules the body uses the heart to pump blood throughout the cardiovascular system so the cells of the body can get what they need. 

Following the Rules
The heart is a muscular pump that is divided into a right and left side by a wall called the septum.  Each side of the heart consists of a thin-walled upper chamber, called the atrium, and a more muscular lower chamber, called the ventricle.  There are one-way “V” shaped valves that point in the direction of blood flow between the atria and the ventricles and the ventricles and their outflow tracts.  When these valves open they direct blood forward to where it is supposed to go and when they close they prevent it from going backward to where it is not supposed to go.  Deoxygenated blood returns from the body through the main veins to the right atrium and then moves into the right ventricle where it is pumped through the pulmonary artery to the lungs to be oxygenated.  The oxygenated blood from the lungs then returns to the left atrium through the pulmonary veins and then moves into the left ventricle where it is pumped through the aorta to the rest of the body. 

Due to potassium (K+) ions leaking out of the cell more than sodium (Na+) ions the inside of the plasma membrane carries a negative electrical charge while the outside carries a positive one.  This difference in the electrical charge across the plasma membrane is called the resting membrane potential.  Nerve and muscle cells are considered excitable because when adequately stimulated they are able to reverse the polarity of the membrane potential.  This means that the inside of the plasma membrane becomes positive and the outside becomes negative.  This takes place because the stimulus triggers Na+ ions to quickly flood into the cell.  This depolarization signals the nerve cell to release its neurohormone and the muscle cell to contract.  After depolarization takes place the nerve and muscle cells are able to return the membrane potential back to normal by stopping Na+ ions from entering and letting K+ ions leave.   

In general, skeletal muscle cells under voluntary control depolarize and contract after stimulation by neurohormones released from motor nerve cells.  But many of the cells in the heart can depolarize automatically.  This takes place because these heart cells have specialized Na+ ion channels that allow Na+ ions to constantly leak into the cell at a faster rate than regular cells.  The speed at which this Na+ ion leakage into the cell takes place determines how fast the cell will depolarize and cause muscle contraction.  The cells of the sino-atrial node within the right atrium dominate and control the heart rate because their specialized Na+ ions channels leak Na+ ions in faster than any of the other heart cells.  This makes the sino-atrial node the natural pacemaker of the heart.  When they depolarize they send an electrical impulse through the conducting system to the other heart cells which depolarizes them and makes them contract and pump the blood where it needs to go.  It is important to note here that heart muscle contraction is different from skeletal muscle contraction in that its rate of depolarization and strength is related to, not only Na+ ions, but also calcium ions (Ca ++) entering the cell as well.

Systole (contraction) takes up about one-third, and diastole (relaxation), two-thirds of the cardiac cycle.  When the sino-atrial node fires its electrical message passes through the atria and the conducting system to the ventricles and they start to contract.  This begins the systolic phase of the cardiac cycle and as the pressure builds up inside the ventricles the valves between the atria and the ventricles close preventing blood from going back into the atria and soon after the valves to the outflow tracts open.  Blood is then pumped from the right side of the heart through the main pulmonary artery to the lungs and from the left side of the heart through the aorta to the rest of the body.  At the end of the systolic phase the valves between the ventricles and their outflow tracts snap shut to keep the blood in the main pulmonary artery and the aorta from going back into the ventricles.  After the ventricles finish contracting they begin to relax which starts the diastolic phase of the cardiac cycle.  Early in diastole the valves between the atria and the ventricles open to allow the blood returning to the heart from the veins to also flow into the ventricles.  The atria and ventricles slowly fill up with blood during diastole and near its end the sino-atrial node fires.  This electrical message stimulates the atria to contract, pushing more blood into the ventricles.  The signal then moves from the atria through the conducting system to stimulate the ventricles to contract and the cardiac cycle begins all over again.    

See: How the Heart Works - 3D Video

Now that you understand how the heart works, it is important to consider what it must be able to do to keep us alive.  After all, experience teaches that life is a dynamic process and when we work and play hard our heart has to pump faster and harder to give us the energy we need to do what we want to do.  This functional ability of the heart to match our ongoing energy needs would have been the difference between our earliest ancestors eating, or being eaten.  Darwinists seem to consider only how life looks but not how it actually works within the laws of nature to allow for survival.  They assume that just because different organisms have similar structures, they must have all come about only by chance and the laws of nature alone.  In contrast, the experience of human invention shows that when encountering a mechanism that allows something to overcome the laws of nature to continue to function, it is much more reasonable to conclude the presence of intelligent design.  A car moving up a hill must have a mechanism in place (like a driver or cruise control) to provide enough gas to its engine at the right moment to overcome the forces of nature that prevent it from going over the top and continuing on its way.  So too, the body must be able to take control of its heart function to do what it needs to do at the right moment to survive within the laws of nature.  Let’s see how it does it.    

Taking Control
When the body is at complete rest it is like a car that is idling.  The car needs a minimum amount of energy just to keep the pistons in the engine moving while the oil lubricates its moving parts and the anti-freeze circulates to keep everything cool.  The same can be said about the body as well.  Even though its muscles are relaxed and its gastrointestinal system is at rest it still needs a minimum amount of energy to maintain adequate brain, heart, lung, kidney and liver function.  When the driver wants to speed up, she steps on the accelerator, which immediately makes more gas and air go into the engine, releasing more energy, and the car moves faster right away.  So too, when you decide to be more active, your heart speeds up and beats harder to provide your muscles with the energy they need to do what you want to do.  Without this ability for the heart to adequately respond immediately to the body’s energy needs, the survival of our earliest ancestors would have been impossible.   

Gland cells and hormones take several minutes to take effective action, whereas, nerve cells can send signals at about one-third the speed of sound and release neurohormones that take effective action immediately.  The Autonomic Nervous System, controlled by the brain, provides the involuntary mechanisms by which heart function is automatically adjusted to match the energy needs of the body.  At rest the heart is dominated by the parasympathetic division, the rest and digest component.  The parasympathetic nerves send out a neurohormone called acetylcholine which attaches to specific cholinergic receptors in the heart.  One of the effects of acetylcholine is to slow down the entry of Na+ and Ca++ ions into the pacemaker and heart muscle cells.  This helps to reduce the heart rate and the force of muscle contraction.  When the body becomes active or excited, it is the sympathetic division, the flight or fight component, that takes over to make sure the blood supply to the tissues is adequate for what must be done.  Here’s how it works.      

Recall, the first thing you need to take control is to have a sensor that can detect what needs to be controlled.  An increase in physical activity takes place from an increase in skeletal muscle contraction.  And an increase in skeletal muscle contraction causes a local build-up of chemical by-products from the increase in its metabolism.  The body has sensors in the skeletal muscle that detects its rate of contraction and these chemicals.  

Recall, the second thing you need to take control is something to integrate the data by comparing it with a standard, decide what must be done, and then send out orders.  The hypothalamus takes the data from these sensors and from other areas of the brain, and modulates the release of a neurohormone called norepinephrine from the sympathetic nerves and epinephrine from the adrenal glands. 

Recall, the third thing you need to take control is an effector that can do something about the situation.  Norepinephrine and epinephrine attach to specific adrenergic receptors in the heart which causes them to increase the entry of Na+ and Ca++ ions into the pacemaker and heart muscle cells.  This results in an increase in the heart rate and the force of muscle contraction which results in more blood being pumped out of the heart. 

Now that you understand how the body takes control of its heart function, it is important to consider how all of this works in real life.  Just as a car’s performance depends on its engine size and efficiency, so too, medical science knows that to do what it needs to do the body’s heart function must meet certain numerical criteria.  In other words, the heart must be able to pump fast and hard enough to allow the body to survive within the laws of nature.  And by the way, this goes for not only the human body, but also every other organism as well.  Evolutionary biologists are convinced that the intelligent design within nature is only an illusion because they believe that chance and the laws of nature alone are capable of producing these different organ systems within different life forms, the precise mechanisms that control them, and these numbers having come out just right so our earliest ancestors could prey on others rather than being preyed on themselves.  It's a preposterous assumption that requires a very furtive imagination.  See what you think! 

Real Numbers Can Mean Functional Ability and Life
When it comes to the laws of nature, real numbers have real consequences.  Just ask the firefighters trying to put out a three story blaze.  They must spray enough water over it as fast as they can to prevent it from being destroyed.  They do this by using a pump to propel water upwards against its inertia, the friction within the hose and the force of gravity involved in climbing three stories.  Their success depends, not only how much water they apply, but also how fast they get it there.  For, if they have enough water but it takes too long to get there, the fire will destroy the building.  And if they get the water there quickly, but they don’t have enough, then the building will go down in flames.  The right amount of water in the right amount of time is what is needed to put out the fire.  Similarly, since our cells need the right amount of chemicals (like oxygen and glucose) to live and function properly, the body must send enough blood in the right amount of time to the tissues to stay alive.  Not just any amount will do, it has to be the right amount and it has to get there in time.  Modern evolutionary theory claims to explain how the heart and the control mechanisms involved in its function may have come into being but it doesn’t even mention the fact that it has no explanation for how the body knows exactly how much blood flow it needs to be able to survive within the laws of nature.

The amount of blood flow within the circulation depends directly on how much blood the heart can pump within a specific amount of time.  This is measured in liters per minute (L/min) and is called the cardiac output (CO).  Just as a fire pump’s flow capacity will determine how effective it is at putting out fires, so too, the cardiac output will determine how effective the heart is at providing enough blood flow to the tissues to meet the body's energy needs. 

The cardiac output depends on two things; how much blood the heart pumps out each time it pumps and how fast the heart is beating.  The amount of blood pumped out of the heart with each contraction is called the stroke volume (SV) and is measured in milliliters per beat (mL/beat).  The number of times the heart beats within a minute is called the heart rate (HR) and is measured in beats per minute (bpm).  The relationship between the CO and the SV and HR can be expressed as CO = SV x HR.  As this equation shows, the CO is directly related to the SV and HR in that if the SV and the HR increase, so does the CO, and if they decrease so does the CO.  As luck would have it, it would seem that our body inherently understands this relationship and knows exactly what it needs to do stay alive and be competitive within the laws of nature.  Of course, Darwinists claim that this knowledge came about by chance and the laws of nature alone.  Let’s look at the real numbers the body must take into account to survive within the world.

At rest, the amount of blood in the ventricle just before it contracts is about 120 mL and with each contraction it normally pumps out about 60% of its contents.  This means that at rest the normal SV is about 72 mL/beat.  At rest the normal heart rate is about 70 bpm.  Since CO = SV x HR this means that the CO at rest is normally about 5 L/m (72 x 70).  But this has to match up with how much O2 the body needs at rest, which is 250 mL/min. 

Since venous blood contains O2, this means that the tissues cannot extract all of what is available to it in the arterial blood.  In fact, depending on the situation, the tissues are usually able to remove anywhere from 25%- 70% of the available O2.  With the normal amount of red blood cells and hemoglobin, the blood of an average male can carry about 200 mL of O2  per liter.  If his CO at rest is 5 L/min and his blood can carry 200 mL of O2 per liter this means that his body, at rest, can provide his tissues with 1,000 mL of O2 per minute (5 x 200).  Since his body only needs 250 mL/min of O2 at rest, this means that it uses only about 25% of what is available.  When it comes to providing itself with enough O2 at rest, it looks like the body knows what it needs to do to survive within the laws of nature.  But what about when it has to be more active, like running away from danger or running after prey?    

The O2 needs of the body at higher levels of activity are: slow walking, 500 mL/min, quick walking, 1,000 mL/min, moderate jogging, 2,000 mL/min, and fast running (the kind of activity our earliest ancestors would have needed to survive) 3,500 mL/min.  With increasing levels of activity the sympathetic nervous system sends out more and more of its neurohormones.  Their effect on how fast and hard the heart pumps causes a rise in the CO; slow walking, 7 L/min, fast walking, 12 L/min, and moderate jogging, 18 L/min.  But what CO would our earliest ancestors have needed to be able to survive? 

Based on modern medicine’s understanding of how the body actually works, this can be calculated.  We know that their tissues would have needed 3,500 mL/min of O2, their blood normally would have carried 200 mL/min of O2, and the maximum amount of O2 their tissues could have removed was 70%.  By dividing 3,500 by 200 and again by 0.7 we find that their CO would have had to have been at least 25 L/min to perform the kinds of activity needed for survival. 

It just so happens that for normal, non-athletically trained individuals, maximum sympathetic nervous output causes the SV to usually rise to 125 mL/beat and the HR to 200 bpm.  Since CO = SV x HR we can calculate that with maximum activity the CO normally rises to 25 L/m (125 x 200) which matches exactly with what they would have needed to live and be able to reproduce.  So, it would appear that the heart and the system that control its function really do know what they’re doing to keep the body alive. 

The mechanism the body uses with its cardiovascular and autonomic nervous systems to provide its cells with what they need to stay active and work right is irreducibly complex.  There are the sensors, which detect the activity of muscle and the chemical changes within it, the brain, which integrates the data it receives from the sensors and sends out orders for the sympathetic nerves to release the right amounts of norepinephrine and epinephrine, and the pacemaker and myocardial cells, which by way of their specific (adrenergic) receptors receive the orders and make the heart effect the changes needed.  If any one part is missing or not working properly the system fails and the body dies. 

But, just being irreducibly complex is not enough to allow for survival.  The body needs to have an inherent knowledge of what is required to stay alive.  Not just any number will do.  I call this natural survival capacity  because cardiovascular function controlled by the autonomic nervous system must make sure the body has just the right cardiac output to meet the metabolic demands of the body that are imposed on it by the laws of nature.  But what happens when it can't meet these demands?  That's what we'll look at next. 

Real Numbers Can Mean Dysfunction, Debility and Death
The last section showed that, at complete rest, the body needs about 250 mL/min of O2 to keep all of its organs working properly and that any increase in activity requires more.  Slow walking requires 500 mL/min, quick walking, 1,000 mL/min, moderate jogging, 2,000 mL/min, and fast running, 3,500 mL/min of O2.  Since we know that the maximum amount of O2 the tissues can take out of the blood is 70% and that this takes place with maximum activity (CO of 25 L/min) we can figure out what the minimum CO would be for lesser activity levels.  We can do this by multiplying 25 L/min by the ratio of the lower and maximum O2 consumptions.  So, to moderately jog the minimum CO would have to be 25 x 2,000/3500 = 14.3 L/min,  to walk quickly, 7.2 L/min, to walk slowly, CO 3.6 L/min and to stay at rest you would need a minimum CO of 1.8 L/min. 

It is important to note here that these are real numbers that reflect real life and the effects of the laws of nature.  So, no matter what evolutionary biologists tell you about how matter must have organized itself into the complex systems we know are needed for life, medical science can tell you that if you don’t have a CO of 7.2 L/min, you can’t walk quickly, if you don’t have a CO of 3.6 L/min, it would be very difficult for you to walk even slowly, and if you don’t have a CO of at least 1.8 L/min, you are probably dead.  When it came to our earliest ancestors being able to survive within the laws of nature, certain parameters regarding cardiac function had to be met and no amount of imaginary effort can deny this fact.     

Clinical experience teaches that when it comes to real numbers and debility there are generally four categories of heart conditions which on their own, or in combination, can cause the heart to malfunction, something that would have made the survival of our earliest ancestors impossible.  They include; coronary artery disease, valvular disorders, heart failure and electrical disorders.  Finally, it is important to realize that each of these conditions alone or together can result in one of the common final causes of death which is cardiac arrest.  Let's take a look at each of them.

Coronary Artery Disease
Even though the heart pumps blood throughout the body it must also supply adequate blood flow to itself so it can do its job.  After all, the part of the heart that does the pumping is muscle which is called the myocardium.  As the blood flows out of the left ventricle, through the aortic valve, the coronary arteries turn back over the surface of the heart.  These epicardial vessels supply blood to the myocardium.  The laws of nature demand that the coronary arteries be wide enough to accommodate enough blood flow so the heart can do what it needs to do.  As noted previously, at rest, the amount of blood the heart pumps is about 5 L/min.  To meet the metabolic needs of the myocardium when the body is at rest the coronary arteries receive about 250 mL/min of this cardiac output. 

The harder the body works, the harder the myocardium must work, and consequently, the more blood must flow through the coronary arteries to provide enough oxygen and nutrients to meet its metabolic needs.  With increasing levels of activity, going from walking slowly and rising to the maximum required for survival, the cardiac output must increase to about 25 L/min.  As note above, this increase in cardiac output is controlled by the autonomic nervous system which stimulates the heart to pump harder and faster by way of its sympathetic division.  However, with maximum activity levels it is also the sympathetic division that relaxes the muscles surrounding the coronary arteries to more than quadruple the blood flowing through them to over 1,000 mL/min as well.   

Just as a clogged fuel line in a car can reduce the flow of gas and compromise engine function resulting in a loss of power, so too, diminished coronary artery blood flow to any part of the myocardium can compromise the cardiac output resulting in loss of power to the body.  Real numbers have real consequences.  If our earliest ancestors could not provide more than the 1,000 mL/min of blood flow to the myocardium, they never could have survived to reproduce.  How do we know this?  Coronary Artery Disease 

The most common heart condition in developed countries, and what most people think of when they hear someone has heart trouble, is coronary artery disease.  The underlying condition that causes coronary artery disease is called atherosclerosis, commonly referred to as hardening of the arteries.  Coronary atherosclerosis is the formation of hard and thick plaques, mainly consisting of fat, along the inner surface (endothelium) of the coronary arteries.  These plaques not only cause narrowing and obstruction of blood flow, but can also activate the clotting mechanism within the blood.  The gradual or sudden disruption of a plaque from the endothelial surface and the release of chemicals by the blood cells attached to it can result in the formation of a thrombus (clot).  This can further reduce blood flow to the heart muscle which can lead to severe oxygen deprivation causing myocardial ischemia.  If the ischemic injury is sufficient to cause irreversible cell damage, then myocardial tissue death takes place and is called a myocardial infarction, commonly referred to as a heart attack or coronary thrombosis.

As stated above, the laws of nature demand that the coronary arteries be wide enough to accommodate enough blood flow so the heart can do what it needs to do.  When a person with coronary artery disease performs an activity in which the oxygen demands of the heart exceeds what the coronary blood flow can provide then ischemia of the myocardium takes place.  Just as pain is experienced from overworking poorly conditioned skeletal muscles, the body usually feels pain when the heart suffers from myocardial ischemia.  This is called angina pectoris and usually manifests as a severe, tight, squeezing, and constricting pain under the middle of the breast bone (sternum).  The pain may radiate across the chest, to either or both sides of the neck, shoulders, down either or both arms, and to the back and upper abdomen as well.  It is not unusual for it to be accompanied by shortness of breath, sweating, nausea, fluttering of the heart and dizziness as well.  If the activity that provoked the heart and brought on this warning pain is stopped immediately, often the angina will settle without any permanent myocardial damage taking place.  However, clinical experience tells us that a person who has limited coronary blood flow is restricted from performing activities that our earliest ancestors would have had to have been able to do to survive.  In other words, coronary artery disease and its effect on functional capacity allows us to see that certain parameters regarding blood vessel diameter and the coronary blood flow must have been met to allow for survival.

Common sense dictates that to really explain how our earliest ancestors came into being and were able to win the battle for survival requires much more than just pointing out how their DNA made their cardiovascular system and all of their other organs and tissues.  As this has shown, the mere presence of coronary arteries does not fully explain how the heart muscle is able to receive the blood flow it needs to function adequately and provide for the metabolic needs of the body.  What also has to be explained is the simultaneous development of how the body has the knowledge and ability to control its coronary blood flow and cardiac output to meet its different metabolic needs to survive.

See: Coronary Artery Disease (CAD) Animation 

Valvular Disorders
As noted above, there are “V” shaped one-way valves that point in the direction of blood flow between the atria and the ventricles and the ventricles and their outflow tracts.  When the valves open they direct blood forward to where it is supposed to go and when they close they prevent blood from going backward to where it is not supposed to go.  But how do the valves know when to open and close?  Just as blood, because it is matter and has mass, must follow the laws of nature by being pumped throughout the body by the heart, so too, whether the heart valves stay open or closed is also a function of those same laws.  Let’s see how.

Imagine you are trying to get into a saloon through its swinging door and preventing you from doing so on the other side is a heavily muscled bouncer.  What must you do to get inside?  Pressure is defined as “the force per unit area applied in a direction perpendicular to the surface of an object”.  To get into the saloon you must apply more pressure to your side of the swinging door than the bouncer can to his.  When it comes to the heart and how its valves work within the laws of nature it is important to remember that those laws state that the pressure inside a chamber with a given amount of fluid is inversely related to the size of the chamber.  This means that with a given amount of blood inside an atrium or a ventricle, if its volume decreases, the pressure within it increases, and if its volume increases, the pressure within it decreases.  Also, just like in meteorology, where air always moves from an area of higher to lower pressure, so too, when a pathway is available, blood always moves from an area of higher to lower pressure.  Here’s how it all works in real life.          

In the left side of the heart, at the beginning of systole, when the ventricle begins to contract, the pressure within it quickly rises above that of the left atrium, causing the mitral valve to close.  This prevents blood from flowing back into the atrium.  As systole continues, and contraction of the left ventricle peaks, the pressure within it rises above that of the aorta and forces the aortic valve to open.  This allows blood from the left ventricle to flow out of the heart into the systemic circulation.  Then, as blood leaves the left ventricle and it begins to relax, the pressure within it quickly drops below that of the aorta making the aortic valve snap shut to prevent blood from going back into the heart. 

Early in diastole, as the left ventricle relaxes further and venous blood from the lungs returns to the left atrium, the mitral valve opens because the pressure within the left atrium rises above that of the left ventricle.  Throughout diastole the blood returning to the left side of the heart through the pulmonary veins enters the left ventricle through the left atrium by way of the open mitral valve.  The same process takes place in the right side of the heart for the tricuspid and pulmonary valves as well.  With diastole ending and systole beginning, the cardiac cycle starts over again and the heart valves open and close as dictated by the laws of nature.   
    
See: Cardiac Cycle - Systole & Diastole

Just as a clogged fuel line can reduce the flow of gas and compromise engine function, resulting in loss of power to a car, so too, diminished blood flow through any of the heart valves can compromise cardiac output resulting in loss of power to the body.  In addition, just as leaky valves in one or more cylinders of a car engine can cause poor compression and loss of power, so too, leaky heart valves that allow blood to go back in the wrong direction, can reduce the efficiency of cardiac function and result in loss of power to the body.  If our earliest ancestors had any of these heart valve defects they never could have survived to reproduce.  How do we know this?  Valvular Heart Disease

Just like the guy-wires used to stabilize a tent, or the mast of a ship, the mitral valve is attached to muscles anchored in the ventricle to strengthen it.  However, degeneration of the valve or ischemic injury to its supporting muscles can weaken it and when the left ventricle contracts, instead of all of the blood going through the aortic valve into the aorta, some of it goes through the mitral valve back into the left atrium.  This is called mitral regurgitation and it reduces cardiac efficiency and output, particularly during exercise, because only some of the blood goes where it is supposed to go.  People with this condition have fatigue, lack of energy and shortness of breath with limited exertion. 

Anyone who has tried to blow up a balloon can appreciate the effect of obstruction to flow and the kind of force needed to overcome it.  The area of the aortic valve is normally 3-4 cm2.  When degeneration, thickening and hardening of the valve occurs this causes its opening to narrow resulting in aortic stenosis.  The smaller the opening, the harder the left ventricle has to work to pump blood into the systemic circulation.  Severe aortic stenosis occurs when the valve area is less than 1 cm2.  Since blood flow to the systemic circulation is compromised, people with this condition are prone to angina, dizziness and syncope (passing out), weakness and shortness of breath often with very limited activity.

It is important to keep in mind that in addition to mitral regurgitation and aortic stenosis, other less common valve problems, like mitral stenosis and aortic and tricuspid regurgitation can occur as well.  In fact, it is not unusual for one or more of these valve disorders to be present at the same time.  Evolutionary biology only talks about how life looks by comparing the heart valves of different species but not how they must properly work within the laws of nature to allow for survival.

 See: What is Valvular Heart Disease

Heart Failure
Recall, systole makes up one-third and diastole two-thirds of the cardiac cycle.  During the diastolic phase the heart relaxes and the ventricles fill up with blood.  At rest, the volume of blood in the ventricle at the end of diastole (EDV) is usually about 120 mL.  Systole then begins with ventricular contraction and the amount of blood pumped out with each heart beat is called the stroke volume (SV).  The ejection fraction (EF) is the ratio between the SV and EDV, showing what percentage of blood is pumped out of the ventricle with each beat.  The EF is a measure of how well the ventricle contracts.  At rest, the SV is about 72 mL which makes the EF is about 60% (72/120).

At rest the heart rate (HR) is usually about 70 bpm and as noted above, the cardiac output (CO) is the amount of blood flowing out of the heart every minute and can be calculated by the formula: CO = SV x HR.  Using this formula we can see that, at rest, the CO is usually about 5 L/min (72 x 70).  Finally, with extreme levels of activity, the autonomic nervous system causes the heart to pump harder and faster.  With maximum stimulation the EDV and EF can rise so the SV can be about 125 mL and the HR can rise to 200 bpm. This results in a CO of 25 L/min (125 x 200).  Clinical experience teaches that if the heart of our earliest ancestors could not have achieved these high levels of cardiac output they never could have survived to reproduce.  How do we know this?  Heart failure

When the heart cannot meet the metabolic needs of the body it is said to be in heart failure.  This condition can involve either the left or right ventricle, or both at the same time.  Left ventricular failure can also be systolic, with diminished contractility during systole, or diastolic, with reduced relaxation and filling of the ventricle during diastole.  Coronary artery disease, resulting in diminished blood flow and damage to the heart muscle is the commonest cause of systolic heart failure.  The hallmark of this condition is an EF below normal, often with a lower SV, because the myocardium can’t contract well.  Heart muscle thickening brought on by coronary artery disease, hypertension and aortic stenosis are common causes of diastolic heart failure.  This results in stiffening of the ventricular walls which limits how much blood enters the ventricle during diastole which lowers the EDV and the SV as well.  

Clinical experience shows that most people with heart failure can function well at rest.  And for those who have mild heart failure the heart can compensate, by increasing the heart rate and size of the ventricular cavity, allowing for activities like slow walking.  But for people with significant heart failure, increased levels of activity are physically impossible because their CO can’t match their body’s metabolic needs.  In other words, real numbers have real consequences resulting in debility. 

People with heart failure, whether left and/or right, or systolic and/or diastolic, must live relatively sedentary lives.  They are incapable of performing at the high levels of activity that our earliest ancestors would have had to have been able to perform to win the battle for survival.  When trying to explain how human life came into being it would seem that there should be some discussion about how the heart just so happens to have the right amount of ventricular contractility and relaxation to allow its output to meet the metabolic needs of the body no matter what it needs to do to survive. 

See: What is Heart Failure?

Electrical Disorders
As noted above, with increased muscle activity and physical effort the autonomic nervous system stimulates the heart to pump harder and faster so the cardiac output can rise to the occasion.  In fact, clinical experience tells us that our earliest ancestors would have needed a cardiac output of at least 25 L/min to do the things they would have needed to do to survive.  The normal heart, under the influence of the sympathetic nerves, does this by increasing its stroke volume to 125 mL and its heart rate to 200 bpm (125 x 200).   And without wide enough coronary arteries for adequate blood flow to the heart muscle, open enough valves for forward blood flow, tight enough closed valves to prevent backward blood flow and adequate enough ventricular contraction and relaxation for a large enough stroke volume, the cardiac output needed to meet the metabolic needs of our earliest ancestors could never have been achieved.  But there is one more very important component of heart function that must be addressed, the heart’s electrical system.

Recall, at rest, the inside of the plasma membrane has as a negative electrical charge and the outside has a positive one.  This difference between the inside and the outside of the cell is called the resting membrane potential.  Nerve and muscle cells are considered excitable because when properly stimulated they can reverse this situation by allowing sodium (Na+) ions to quickly enter, making the inside positive and the outside negative, in a process called depolarization.  After this, they can return to the resting membrane potential back to the way it was before in a process called repolarization.  

In general, skeletal muscle requires stimulation by a nerve to cause depolarization and muscle contraction.   However, as noted previously, although nerves can modulate how often and how hard the heart contracts, there are cells within the heart that can depolarize on their own without the need for direct nerve stimulation.  In particular, the right atrium houses the sinus node (sino-atrial or SA node) which depolarizes faster than all of the others.  This makes it the natural pacemaker of the heart and, at rest, generally makes the heart contract at 60-100 beats per minute (bpm).  The electrical message from the sinus node stimulates the atria to contract and moves quickly to a junction box that sits between the atria and the ventricles called the atrio-ventricular node (AV node).  The AV node is the electrical wiring that physically connects the atria to the ventricles.  Like the sinus node, the AV nodal tissue can depolarize automatically and generate its own electrical impulse.  But its intrinsic rate is only 40-60 bpm.  Since the sinus node intrinsically has a faster depolarization rate than the AV node, its electrical impulse depolarizes the AV node before it can generate its own impulse.  The AV node slows the electrical impulse by about 1/10 of a second, allowing the atria to contract fully, and then sends the message to specialized conducting tissue.  This tissue then rapidly conducts the electrical impulse to the ventricles so that coordinated contraction and the pumping of blood out of the heart can take place.  Like the sinus and AV nodes, the specialized conducting tissue below the AV node can also automatically depolarize.  However, its intrinsic rate is only 20-40 bpm and so it is normally stimulated from above before it can generate its own impulse.  It is important to note here that this hierarchical set up for impulse formation and conduction is what allows for coordinated ventricular contraction and normal cardiac function.  Let’s see what can happen when the electrical system isn’t working right.     

Normal sinus rhythm is when the sinus node paces the heart at 60-100 bpm and sinus bradycardia is when it paces it at less than 60 bpm.  It is not unusual for a person to have a heart rate of 45-50 bpm at complete rest and even 30-40 bpm during sleep.  However, it is considered clinically significant when the heart rate stays below 45 bpm while awake, and in particular, if it does not increase adequately during physical activity.  This is called a bradyarrhythmia and in the absence of medication or hypothyroidism, is usually due to either a defect in sinus node function (sick sinus syndrome)or a problem with conduction (atrioventricular heart block).  The commonest causes for these conditions are age-related degeneration and coronary artery disease. 

Recall, the normal cardiac output (CO) at rest is about 5 L/min and is directly related to the heart rate (HR), which is usually about 70 bpm.  This means that a bradyarrhythmia of 35 bpm, at rest, would cut the CO in half to 2.5 L/min.  It is possible to live with such a slow heart rate and low cardiac output, as long as you do nothing at all.  Clinical experience shows that most people with significant bradyarrythmias are not able to get their heart rate up fast enough so their cardiac output will allow them to be physically active.  In fact, most people with bradyarrhythmias have problems walking slowly or going up stairs in addition to managing their activities of daily living.  This means that having a bradyarrhythmia would have made it impossible for our earliest ancestors to generate the CO of 25 L/min they would have needed to survive.  This is just another example of how real numbers have real consequences and lead to debility. 

A sinus tachycardia is when the sinus node paces the heart at a rate greater than 100 bpm.  An increase in metabolic needs, resulting in stimulation of the sympathetic nervous system, is the usual cause.  Physical exertion, stress, anxiety, fear, pain, fever, heart failure, hyperthyroidism and low blood pressure are some of the usual culprits.  However, conditions such as poor coronary blood flow, emphysema, hypertension and low serum potassium, can predispose some of the ion channels in the heart tissue to malfunction.  These changes can result in abnormalities of depolarization and repolarization which lead to increased electrical irritability of the atria and the ventricles.  When this happens they can take over the pacing of the heart from the sinus node with unusually rapid heart rates that exceed 100 bpm and are called tachyarrhythmias

The atrial tachyarrhythmias can cause the heart rate to rise to over 200 bpm, significantly reducing the time for relaxation and filling of the ventricles.  Since these fast heart rates occur spontaneously at rest and without exercise-induced sympathetic stimulation, the stroke volume and cardiac output can often drop dramatically.  People with atrial tachyarrhythmias usually feel a flutter in the chest along with weakness, dizziness, chest discomfort, and shortness of breath on limited exertion.  Clinical experience teaches that if our earliest ancestors had had atrial tachyarrhythmias they never could have generated the CO of 25 L/min they would have needed to survive.  But there's more to consider.    

See: Electrophysiology of the Heart

Cardiac Arrest
Evolutionary theory claims to explain how life came into being by describing only how life looks but not how it actually works within the laws of nature to survive.  But we must now consider what actually causes the heart to stop beating (cardiac arrest) and what exactly happens to make the heart suffer cardiac arrest resulting in death?  It's important to realize that although the conditions mentioned so far can predispose a person to die from cardiac arrest, they are not the final event that actually causes it.  Now, if you were trying to figure out how life came into being, wouldn't you think that understanding how the body dies of cardiac arrest would be an important place to start?  Like knowing all the different ways a car can “die” and then working backwards to figure out how to prevent them from happening?  If you think about it, that's exactly how the control systems in the body are set up: to prevent not only respiratory but also cardiac arrest. 

A cardiac arrest is the sudden stoppage of effective cardiac output where the heart is no longer able to provide enough blood flow to sustain life.  Clinical assessment will show that the person is unconscious and unresponsive to tactile stimulation and not breathing because the brain does not have enough blood flow for it to work properly.  Also, a pulse will not be palpable and no heart sounds will be heard because the heart is not pumping blood effectively enough. 

There are basically three different conditions that can cause cardiac arrest.  One is called asystole, (flat-line) where there is no electrical activity and no ventricular contraction.  This results in no systolic function and therefore no cardiac output and blood flow within the circulatory system.  Another is called pulseless with electrical activity (formerly called electromechanical dissociation), where there is electrical activity but no mechanical response from the ventricles.  To the observer this condition acts like asystole in that there is no systolic function and zero cardiac output and blood flow within the circulation as well.  The third condition is the malignant and life-threatening ventricular dysrrhythmias such as ventricular tachycardia, ventricular flutter and ventricular fibrillation. 

Ventricular tachycardia (100-250 bpm) and ventricular flutter (150-300 bpm) are very rapid and regular rhythms which can severely limit cardiac output and blood flow within the circulation.  If prolonged these tachyarrhythmias usually degenerate into ventricular fibrillation.  Ventricular fibrillation is an extremely rapid ventricular dysrrhythmia (400-600 bpm) in which there is electrical disorganization and an absence of coordinated ventricular contraction.  In essence the ventricle quivers and is unable to effectively pump blood out of heart leading to minimal, if any, cardiac output and blood flow within the circulatory system.         

The malignant and life-threatening ventricular dysrrhythmias take place due to electrical irritability within the heart muscle and are most often associated with coronary artery disease and/or left ventricular failure.  If a person dies unexpectedly from a cardiac arrest it is called sudden cardiac death and is most often due to one of these dysrrhythmias.  It is unfortunate that sudden cardiac death may be the first symptom for 25% of people with coronary artery disease. 

There are many different conditions that can lead to the other two causes of cardiac arrest which effectively results in no systolic function and zero cardiac output.  Both of these conditions require a massive failure in cardiac function.  For although it is the sinus node that naturally paces the heart (usually at about 60-100 bpm) there exists a hierarchy of other cells below it that can automatically depolarize and pace the heart, albeit at lower rates.  If the sinus node malfunctions, the AV node takes over with what is called a junctional rhythm, usually at a rate of 40-60 bpm.  And if the AV node malfunctions, the specialized conduction tissue below it takes over with what is called an idioventricular rhythm which paces the heart at an even lower rate of 20-40 bpm.  People who experience this usually feel very tired and weak and have problems even walking slowly, but they aren’t dead.  However, for there to be no systolic function, whether there is electrical activity or not, means that something catastrophic has to have happened.  Here are a few of the usual culprits.   
 
It is important to remember that all of the parts of the heart are made up of cells, each of which must control its volume and chemical content and requires certain chemicals to work properly.  So, either a major blood flow problem to the heart or the lungs, or a generalized metabolic problem in the body can lead to a sudden loss of systolic function.  If not reversed, ventricular fibrillation usually degenerates into asystole because there is limited, if any, blood flow going through the coronary arteries which results in the death of most of the heart cells.  Also, a sudden lack of sufficient coronary blood flow caused by the blockage of either a major vessel or several branches, due to a clot (thrombosis), can do the same thing.  A major blockage of blood flow in the pulmonary arteries, due to clots coming from the leg or pelvic veins (pulmonary embolism) not only drastically reduces the blood level of oxygen but also the return of blood to the left side of the heart and leads to asystole.  Severely low blood pressure (hypotension) often due to low blood volume (hypovolemia), from either excessive blood loss (hemorrhage) and/or excessive water loss (dehydration) or cardiogenic or septic shock results in limited blood flow to the heart cells, which leads to cell malfunction and death from asystole.  Very low blood levels of oxygen (hypoxia) and/or glucose (hypoglycemia) prevents the cells from getting the energy they need to function properly and this is another cause for the total absence of heart function.  High levels of hydrogen ion (acidosis) are toxic to cells and high or low blood levels of potassium (hyperkalemia or hypokalemia) can cause nerve and muscle cell malfunction, so these conditions can also result in cardiac arrest due to asystole.  Also, the core temperature of the body affects its metabolism and how well the enzymes in the cells work, so when the body is extremely cold (hypothermia) this can result in a lack of heart function as well. 

Epilogue
When it comes to trying to understand how human life came into being, we are now entering the credibility zone.  For in trying to explain how the heart is able to provide the blood flow the body needs to live within the laws of nature, evolutionary biologists are faced with a Catch-22 situation.  Not only is the heart made up of cells, but so are all the organs and tissues involved in providing the control mechanisms needed to allow the heart to function properly in the first place.  In other words, the heart is dependent on its own function for survival because all of the systems in the body that control chemicals like oxygen, glucose, water, sodium, potassium, hydrogen ion and things like clotting, blood pressure and temperature, are also made up of cells that are dependent on the heart providing enough blood flow to them so they can do what they are supposed to do. 

The universal human desire to know the truth requires us to go beyond just describing how life looks, as evolutionary biology does, by digging down deeper to understand the actual mechanisms behind how life works within the laws of nature.  The heart and the organ systems that control its function, being made up of different parts, are irreducibly complex, but clinical experience teaches that that isn't enough to explain how life came about.  As this article and others have shown, the body must take control to follow the rules imposed on it by the laws of nature because real numbers have real consequences and are a matter of life and death.  And to do this it needs to have natural survival capacity, an inherent knowledge of what those numbers should be and be able to do the right things at exactly the right times to stay alive. 
Not only does life need the information present in its DNA to make everything it needs to come into being, it also needs other information to allow it to survive within the laws of nature as well.

As Stephen Meyer stated in The Information Enigma, the cause in operation that drives life is information, particularly digital or typographic information that experience tells us comes from a mind and not a material process.  It is indeed unfortunate that evolutionary biologists, who claim to know the truth about how life came into being, and control what students are taught about it, do not seem to understand this most fundamental of principles.

 

Be sure to catch all of the articles in Dr. Glicksman's series, "Beyond Irreducible Complexity."



Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.

Comments and questions about this article or any of the previous ones are welcome.

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Copyright 2016 Dr. Howard Glicksman. All rights reserved. International copyright secured.

April 2016