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INTRODUC
TION


Before onset of hypertension, changes occur in the architecture of arteries.....


If you could catch these changes early, you may be able to slow the progression and stop further damage to your arteries.
This will protect your three most important organs - heart, kidneys and brain and prevent you from getting heart attacks and heart failure, kidney disease and stroke.

 
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Arterial Tree in Health and Disease


Heart and Circulation : With each heart beat, our heart pumps fresh nutrient rich blood out into the circulatory system. This blood supplies oxygen to our cells and keeps them alive and functioning.

Our circulatory system consists of arteries and veins. Arteries carry blood from the heart and veins return the blood that needs to be recycled ( waste products are removed and oxygen is added ).

Arterial Tree in Health : Arteries are the most important component in this network of blood vessels. The largest artery in the body is aorta and is directly connected to the heart.

Aorta branches in to smaller arteries which again divide into micro-arteries called the arterioles. A network of arterioles is laid out in all tissues of our body and more importantly in our heart, kidney and brain.

Among all organs, our kidneys are a little different, it is actually a collection of very small and thin blood vessels that work as filter and remove excess water and waste products in the form of urine. On the other hand, in the heart and brain, the function of small arteries and arterioles is to supply blood to the tissue of these organs so that they function normally.

Each artery has a wall that is multi-layered and each component of this wall plays an important role in providing adequate perfusion to organs.

Arterial Tree in Disease : When these arterial walls are damaged, the blood supply to our vital organs heart, kidney and brain is compromised leading to various ailments.

For example when one gets a heart attack, it is most likely because the arteries that supply blood to the heart were damaged by years of smoking, elevated cholesterol, uncontrolled hypertension and diabetes.

Stiff arteries eventually narrow to the point where blood supply to the heart is compromised leading to angina and heart attacks

Arterial Tree and Kidneys : Same is true with kidneys too, but the damage is not only irreversible but also progressive.

As mentioned earlier, unlike other organs, kidneys are formed by a large collection of very thin arteries. The caliber of these arteries is so small that they can only be visualized under a microscope. These micro-arteries function as filters, removing waste products and excess water from the body.

These thin and fragile arteries are affected early in those who follow unhealthy lifestyle.


 
 

It is also true we are born with some risk facors and these cannot be changed. Some individuals have genetic predisposition (strong family history of kidney disease) to arterial disease, ethnicity (some races have a particular predilection to develop chronic kidney disease), old age also leads to stiffness of arteries (due to so called ‘wear and tear phenomenon’) that affect the arteries as well.  

These individuals should take precautions early and adapt a healthy lifestyle early to prevent arteries from damage.

Functional Arterial Reserve

A healthy artery is compliant (expands when the need arises). Whenever our body requires more blood – e.g. our digestive tract after eating food, our heart when we excercise or perform physical exertion,  the arteries supplying these organs increase in size temporarily to provide more blood.

Take the example of a young healthy man who decides to participate in a marathon. He trains hard for months to be fit to take part in the marathon. When an individual runs in a marathon, the heart beats faster so that more blood and energy is pumped into the body in order to accomplish this arduous task.

But to beat fast, the heart requires more oxygen (and increase in blood suuply).

The arteries supplying blood to the heart should have enough reserve to expand and accommodate excess blood needed to optimize heart function in this time of physical stress.

The healthy young man successfully participates in the marathon and completes the run in a record time.

He could perform this task because his arterial health was good and he had adequate coronary (heart) artery reserve that came to his rescue during the marathon.

 

Imagine the case of another gentleman, who appears healthy but follows a very sedentary lifestyle, he is slightly overweight and smokes regularly.

His blood pressure and other clinical parameters were all normal at a recent routine annual physical exam.

His cholesterol was elevated and he was advised to diet and take medications to reduce cholesterol, but did not follow. 

One morning while rushing to his office to be in time for a meeting, he finds the elevator to his floor broken. He decides to take the five flight of stairs and save time. After climbing few stairs, he felt short of breath and his chest started hurting. He had to call 911 and was taken to a hospital nearby. His EKG showed he was suffering from angina.

This gentleman did not have any functional arterial reserve to begin with and as soon as his heart underwent minimal stress, it fell apart. 

Even in the kidneys we have renal reserve. It is diminished in those with arterial disease. Quite often the kidney specialists come across patients who have apparently normal kidney function, but develop acute kidney failure when they experience even a little stress like dehydration.





Early Detection of Arterial Stiffness


It is now simple to screen apparently healthy individuals and identify those with early changes arterial tree. Prescribing these individuals to follow a healthier lifestyle will improve their arterial health and conserve functional arterial reserve and prevent heart and kidney disease and stroke.

Several non-invasive devices have been developed that are FDA approved to be used in clinical practice. These devices measure different parameters that reflectarterial health. Several large clinical trials have validated that these parameters accurately reflect arterial health.

In summary, arterial health is critical for us to maintain good health and lead a healthy life. We now have means to detect arterial stiffness and modify our lifestyle to provide optimal protection to our heart, kidneys and brain.


 

 
A New Concept in the Field of Hypertension

For years, experts have accepted that hypertension is a disease condition. However, in recent years, the concept of hypertension has taken on a new dimension. Some experts now argue that hypertension or elevation of blood pressure is not a disease in itself, but a marker of disease that is affecting a person’s arterial (blood vessel) system.

As the arteries (blood vessels that carry fresh blood from heart to the whole body) lose their elasticity, blood pressure starts to rise. Stiffness in the arteries occur when the architecture and function of arteries is altered because of excess cholesterol (hyperlipidemia), excess sugar (diabetes), aging, genetic factors etc. 

Traditional methods for blood pressure measurement , using a sphygmomanometer (mercury or aneroid type) as is usual in a doctor’s office are not sensitive enough to detect early changes in arterial elasticity.

There are several new devices that have been validated in clinical trials and are USFDA approved to measure a person’s arterial stiffness in the out-patient setting.

Of the many measures of arterial stiffness three have been validated in large clinical trials. These are the Pulse wave velocity (PWV), the Augmentation Index (Aix) and the Central Blood pressure level.

Pulse wave velocity (PWV) : Every time our heart beats to pump fresh blood out to the periphery (systole), it also generates a wave that precedes the column of blood. This wave helps blood to flow forward. As the arteries get stiffer, there is an increase in the velocity with which this pulse wave moves forward. Measurement of pulse wave velocity indicates if the arteries are beginning to get stiff. In one large study published recently, a high PWV  predicted future onset of hypertension.

Augmentation Index (Aix) : When the forward moving pulse wave strikes the branching points of very small arteries in the peripheries, a reverse (reflectance) wave is generated that travels back in the arterial tree and reaches the heart between the heart beats (diastole). This is the most critical moment for the heart, because as the heart relaxes, its own arteries open up and blood gushes into them and provides the heart with nourishment. Normally, the reflectance wave augments and helps this blood flow supplying the heart.

When arteries become stiff, this relationship is altered as the forward wave moves fast, hits the branch points early producing an earlier and faster reflectance wave that reaches the heart while the heart is still in the contraction phase (systole) and not yet relaxed to allow blood flow to its nourishing arteries. As a result of this, the blood supply to heart is compromised to a certain extent and the contracting heart is under added pressure because of the early returning wave.

This duet of forward and return wave is measured in the form of Augmentation Index (Aix). An increase in Aix is an early indication that it is not just the large arteries, but also the architecture and stiffness of smaller arteries that has altered.


Central Blood Pressure (CBP) : This is yet another new concept that is revolutionizing blood pressure measurement and assessment. Traditional blood pressure measurement is performed in the arm as is usual in a doctor’s office. Data from clinical trials now indicates that a more accurate blood pressure that should be measured is the pressure in the large artery (aorta) attached to the heart. It is this pressure in the aorta that is transmitted to and experienced by our vital organs such as the heart, kidneys and brain

There is a large discordance between traditional (arm) blood pressure measurement and central blood pressure level. For example, two patients may have similar arm blood pressures (eg 135/85 mmHg), but different central blood pressure levels. The one with higher central blood pressure likely needs interventions such as aggressive lifestyle changes and if the person is already on anti-hypertensive therapy, he/she needs to have additional medications that will target and help achieve a lower central blood pressure.



 

Arterial Stiffness Measures are Here to Stay

Evidence from large observational studies and some of the randomized controlled trials demonstrates that arterial stiffness measures are better in stratifying a patient’s cardiovascular risk than traditional blood pressure measurement. They provide better goals of blood pressure lowering that appear to improve cardiovascular outcomes.

Some of these tests are now recommended by international societies of hypertension for risk stratification of hypertensive patients.

Arterial stiffness measures adds enormous important information on cardiovascular health of an individual. It will provide a physician information if the patient is at a higher risk for these diseases. For these patients periodic monitoring of these measures will help physicians to evaluate if the therapy they have tailored for the patient is effective or not.

These are unique tests that determine if your arteries are aging faster than you. 

In our body there are large arteries that carry blood from the heart to our vital organs and there are small arteries that wire these organs and provide fresh oxygen and nutrition rich blood that nourishes them.

Long before the development of heart and kidney disease or stroke our arteries are affected. 

There are advanced new devices that detect these early changes and help personalize interventions that help preserve arterial health.

Augmentation Index (Aix), Pulse wave velocity (PWV) and Central blood pressure (CBP) are three measurements that define arterial stiffness. 

In healthy individuals as well as in those with hypertension, heart  or kidney disease and stroke these measures detect if the arterial system is aging faster. In addition, in patients with heart or kidney disease periodic screening helps in guiding physicians to provide optimal therapy.

These tests are non-invasive and are performed in a physician office setting. It takes about 15 minutes to perform these tests.

 
Suggested Interpretation of Arterial Stiffness Tests

Based on current findings, the literature suggests that if :

• PWV is over 6m/s in a normotensive individual, it predicts onset of incident hypertension

• Central systolic pressure exceeds approximately 125mmHg, or  Central pulse pressure is equal to or exceeds 50mmHg, more aggressive management of the patient’s blood pressure should be considered.

• In patients with elevated augmentation index, vasodilating drugs (e.g., ACEIs, ARBs, CCBs, vasoactive beta blockers) may have a greater efficacy than non-vasodilating drugs (e.g., beta blockers, thiazide diuretics)


 
 

 

         
 
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