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Digital Plethysmography - Arterial Health
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Maintaining the Health of Your Heart and Vascular System

 

With advancing age, the cardiovascular system undergoes subtle but progressive changes that result in altered function:

·        The inner muscle of the heart (endocardium) becomes thicker and opaque

·        The wall of the left ventricular (LV) thickens.

·        Although the size of the heart muscle cells (myocytes) increases, the number of myocytes decreases as does the number of cells in the conduction system.

·        The decrease in the filling rate of LV in early diastole is accompanied by a greater rate of filling in late diastole augmented by atrial contraction.

·        The maximum achievable heart rate and ejection fraction (with exercise) decreases.

·        Early diastolic filling slows.

·        Between beats, the aging ventricle fills with blood more slowly because it is relaxing more slowly than it did when it was young.

·        The heart compensates for the slower early filling rate by filling more quickly in the late diastolic period, which is now larger and holds more blood than when young.

·        The left atrium, stretched with a greater volume of blood in older hearts, contracts harder, pushing open the valves and propelling the blood into the ventricle.

·        In younger people, about twice as much blood flows into the ventricle during the early filling period than during late filling.  As we age this ratio changes so blood flow during early and late filling is about equal.

 

There are several ways to estimate the health of your cardiovascular system, which is made up of:

·        Your heart muscle – assessed through an Acoustic Cardiograph (ACG)

·        An electrical system within your heart is that governs your heart rate and conduction through your heart muscle – assessed through Heart Rate Variability (HRV) and an Electrocardiogram (EKG)

·        The flow characteristics of your blood (clotting, etc). – assessed through urine and blood laboratory studies.

·        Your vascular system – assessed through your blood pressure readings and a Digital Pulse Analyzer (DPA) explained below.

 

Blood pressure is the most common assessment of your vascular system.  The importance of blood pressure is in part due to the work load placed on your heart and its contribution to atherosclerosis (hardening of the arteries).  Elevated blood pressure increases the risk of heart disease and stroke, which are the first & third leading causes of death in the United States. 

 

The diastolic pressure is the bottom number in a blood pressure reading. The diastolic number remains, especially for younger people, an important indicator of hypertension.  The higher the diastolic pressure, the greater the risk for heart attacks, strokes and kidney failure.  The systolic pressure is the top number in a blood pressure reading.  Although both systolic and diastolic numbers are important, for people 50 or older, systolic pressure gives the most accurate information for diagnosing high blood pressure.

 

The term arteriosclerosis comes from the Greek word for “hardening of the arteries.”  It generally refers to when the arterial wall becomes thickened and loses elasticity.  Contributing to arteriosclerosis is the build up of plaque, which is initiated by free radical damage to the artery wall.  Free radicals mutate the DNA of arterial cells, causing them to replicate themselves many times over.  The proliferating cells expand, stretch and tear the inner lining of the artery.  Arteriosclerosis also develops when the arterial wall is injured.  In response, blood proteins are attracted to the injured site and lay down fibrin to patch the tears.  Minerals and debris circulating in the blood become trapped in the patch.  Because of opposing electromagnetic charges, the trapped minerals attract fats, including cholesterol.  Cholesterol serves to give the patch a slippery surface so that blood cells can glide past it, and it acts as an antioxidant of last resort by donating electrons to neutralize free radicals, thus itself becoming oxidized in the process.

 

The arteriosclerosis process begins with changes to the endothelium (the innermost layer of the artery).  These changes cause white blood cells to stick to the endothelial cells, weakening the barrier between the endothelium and other layers of the artery. This allows fats, cholesterol, calcium, platelets, and cellular debris to accumulate in artery walls.  Some plaques are unstable and can rupture or burst.  When this happens, the plaque itself can block the artery or the ruptured plaque stimulates blood clotting inside the artery.

 

As an artery becomes more and more narrowed, less blood can flow through and the artery becomes less elastic.  Most plaque buildup occurs in medium to large arteries.  Atherosclerosis is a slow, progressive condition that often starts in childhood and by age 65 affects 1 out every 2 adults.  Arteriosclerosis can remain undetected for many years.  In fact nearly half of all people in the western world who die from cardiovascular related illnesses never experience any prior symptoms!

Text Box: The Importance of a Healthy Endothelium One of the main determinants of blood pressure is the lining of the blood vessel wall, the endothelium. The endothelium is the layer of thin, flat cells that lines the interior surface of blood vessels, forming an interface between circulating blood and the vessel wall. Endothelial cells line your entire circulatory system, from the heart to the smallest capillary. The endothelium influences: • Vasoconstriction and vasodilation and hence the control of blood pressure • Blood clotting • Atherosclerosis • Formation of new blood vessels (angiogenesis) • Inflammation and swelling (edema) • Production of Nitric Oxide which diffuses into smooth muscle layer causing: o Dilation/relation of your arteries o Inhibits platelet aggregation and the adherence of circulating blood cells to blood vessel walls. As a result it reduces clotting o Decreased monocyte (white blood cell) migration (into smooth muscle cells) which is the beginning of the atherosclerotic process o increases oxygen supply o protects the heart from damage and cell death o mediator in inflammation o potent free radical scavenger

Healthy endothelial cells product nitric oxide, an important signaling molecule that helps keep arteries supple. When nitric oxide enters a cell, it stimulates a biochemical process that relaxes and dilates blood vessels.  Nitric oxide also keeps atherosclerosis in check by preventing platelets and white blood cells from sticking to the blood vessel walls. The molecule can also curb the abnormal growth of vascular muscle, which can thicken blood vessel walls.  Even if sufficient amounts of nitric oxide are produced it can still be inactivated by oxygen free radicals –which are unstable molecules that injure vascular tissue.  Without adequate levels of biologically available nitric oxide, endothelial cells in the intima can’t function properly.  Some researchers consider decreased availability of nitric oxide in the endothelium to be one of the earliest signs of arterial aging and high blood pressure.

Text Box: In addition, those at high risk of developing heart disease or have heart disease produce a modified amino acid called asymmetric dimethylarginine (ADMA). ADMA is a modified amino acid that can block the production of NO. Similar in structure to L-Arginine, ADMA can fit into the NOS enzyme, but because it has two extra methyl groups, it can’t be made into NO. The level of ADMA is a better predictor of endothelial impairment than the level of cholesterol. Many different researchers around the world have found that blood levels of ADMA were elevated in people with each of the risk factors for heart disease. • Elevated cholesterol • Elevated triglycerides • High blood pressure • Insulin resistance • Elevated homocysteine • Tobacco use ADMA accumulates in people with risk factors, blocking the production of NO, causing poor blood flow and contributing to hardening of the arteries. L-Arginine along with anti-oxidants can improve the body’s ability to get rid of ADMA. A study reported in the concluded that treatment with L-arginine produced a fourfold increase in blood vessel dilation from 2.2% to 8.8%. (Hambrecht et al., 2000)This is one reason for the inclusion of Arginine in our own Formula HT. (The Cardiovascular Cure by John P. Cooke, M.D., Ph.D. and Judith Zimmer)

The DPA (Digital Photo-plethysmograph Analyzer) is a FDA approved device used to measure and analyze pulse waveforms and heart rate.  The measurement probe is placed on your finger (or toe) and a LED light is transmitted through your finger to a photodiode sensor on the other side.  The sensor detects how much light was absorbed by the hemoglobin in your blood vessels.  The DPA converts the changes in light into a waveform and graph, which are used to assess your heart rate, blood vessels, and the power and speed of your heart muscle.  For example, the proportion of your blood pumped out during each beat compared to the amount that remains in your heart at the beginning of the next beat, is called the ejection fraction.  The ejection fraction estimates the hearts pumping ability based on the relationship between end diastolic volume, stroke volume, end systolic volume, and ejection fraction.

 

From the information provided, the following can be assessed:

  1. Early detection of hypertension
  2. Early detection of arteriosclerosis (hardening of the arteries)
  3. Blood circulation status
  4. The relative age of your blood vessels
  5. Disturbances in the smaller blood vessels not found when measuring you blood pressure with a cuff.

 

A print out of your DPA will be given to you and a more detailed interpretation will follow.  The report will explain your values for:

  1. Heart Rate - Heart rate is a stronger predictor of cardiovascular death in the elderly, particularly in men, than traditional risk factors such as diabetes and hypertension.  After 12 years of follow-up, elderly men with > 80 beats per minute had a significantly higher rate of cardiovascular mortality.  A low heart rate, below 64 beats per minute, was protective against cardiovascular mortality.  (Arch Intern Med 1999;159:585-592).
  2. Pulse Height
  3. Cardiac Ejection Time
  4. Elasticity Index
  5. Angle of Descent Index
  6. Cardiac Ejection Elasticity Index
  7. Dicrotic Dilatation Index
  8. Dicrotic Elasticity Index