Heart disease is a condition characterised by the presence of cholesterol-rich plaques in the coronary arteries.
The heart works non-stop, day in and day out, throughout our life span. The heart muscle (myocardium) is constructed with special cells called myocytes which contract and pump blood tirelessly.
In order to do so, the myocardial cells require a regular, uninterrupted and adequate supply of oxygen and nourishment, and this is obtained from the blood flowing in the three arteries, called the coronary arteries, which are spread over the surface of the heart. When the coronary arteries are healthy, there is no obstruction in the lumen. The blood flows freely and so there is no difficulty in supplying the required oxygen and nutrition.
What is coronary artery disease/ ischaemic heart disease?
What is significant (advanced) heart disease?
What are the factors that cause heart disease?
What are natural oxidants?
Why should heart disease be vigorously treated?
How to diagnosis the presence of heart disease?
What are tests to detect heart disease?
Why does physical exertion cause chest pain?
What are the symptoms not caused by heart disease?
What is angina?
But when disease strikes one (or more) of the three coronary arteries, it progresses relentlessly, eventually producing obstructive plaques in the lumen which impede the blood flow. As a consequence, the supply of oxygen and nourishment to the myocardial cells gets compromised. The development of heart disease is very complex and the different stages are as follows:
The point being made here is that heart disease can be easily missed by conducting the common tests we can fail to diagnose heart disease by the common tests especially when the disease is not significantly severe.
- The disease starts when LDL particles carrying cholesterol sneak into the inner layer of the coronary artery wall through a damaged segment. Tiny patches of arterial wall get damaged by free radicals in the blood and by certain conditions (called ‘risk factors’) such as hypertension, diabetes, smoking. These sites are the ideal entry points for LDL.
- The LDL-cholesterol gets oxidized by free radicals and other chemical processes, either before or after entry into the arterial wall. The oxidized LDL-cholesterol attracts monocytes and other cells, more cholesterol, collagen, calcium, smooth muscle cells and fibrous tissue to form a cholesterol-rich ‘atheromatous plaque’ in the wall of the artery. Atheroma is derived from the greek word athērōma meaning tumor full of matter resembling porridge.
- For many years, the gradually expanding plaque remains hidden within the confines of the arterial wall. The arterial wall gradually expands to accommodate the enlarging plaque. The plaque, whilst confined to the arterial wall, does not cause any narrowing of the lumen of the coronary artery so the blood flow continues unhindered.
- Eventually the arterial wall can dilate no further and the enlarging plaque bulges into the lumen. As the plaque increases in size, it causes progressive narrowing of the lumen and this restricts the flow of blood. This narrowing is called ‘stenosis’ or ‘lesion’ and is expressed as a percentage of lumen affected. For example, a 50% lesion or stenosis means that 50% of the lumen is obstructed by the plaque at that site. Various degrees of stenosis of the lumen, and different sized plaques confined to the arterial wall co-exist in individuals. Depending on the severity of the stenosis, the blood flow across the stenosis is proportionately reduced – impairing the delivery of adequate oxygen and nourishment to the myocardium.
Presence of plaques in coronary arteries is called heart disease or coronary artery disease or ischaemic heart disease (ischaemia: inadequate supply of blood).
Heart disease is present even when plaques are confined to the arterial wall. The disease starts in adolescence and usually progresses very slowly.
It takes 20-40 years for the first speck of cholesterol to become a sizable lump to cause a deleterious effect on the blood flow. Once started, the disease usually blossoms unless steps are taken (see, Defeat Heart Disease) to thwart its progress.
WHAT IS “SIGNIFICANT” (ADVANCED) HEART DISEASE?
A narrowing or stenosis of 70% or more is called significant heart disease. Such a stenosis is considered significant because it causes substantial obstruction to blood flow resulting in troublesome angina (chest pain).
|FACTORS THAT CAN NOT BE CONTROLLED||FACTORS THAT CAN BE CONTROLLED|
|Gender: male gender||High cholesterol, LDL-cholesterol and triglycerides|
|Females, after menopause||Diabetes|
|Advancing age||Tobacco – smoking|
|Overweight and obesity|
|? Vitamin B6 deficiency|
|? Dietary deficiency of iodine|
|High levels of uric acid|
When the disease is significant, it can be detected by tests like treadmill stress test and radionuclide test called SPECT. Although these plaques cause angina, they are less likely to rupture and cause a heart attack. Indeed, lesions that are more than 70%, cause less than 15% of all heart attacks.
For heart disease to strike in any individual, LDL has to get oxidized. Oxidation of LDL-cholesterol is a complex process and involves free radicals and is strongly influenced by the risk factors such as hypertension, diabetes and smoking.
Since free radicals seem to have a important impact in the development of heart disease, it makes absolute sense to quell free radicals by ensuring an adequate consumption of natural antioxidants such as in fruits, vegetables, nuts, seeds, herbs, spices, and tea and coffee.
There are many factors which are strongly linked to heart disease – they are called the ‘risk factors’. The risk of heart disease increases in direct proportion to the number of risk factors present. Some of these risk factors are under our control and some we can not change. The risk factors are:
Why should heart disease be vigorously treated irrespective of the degree of stenosis?
Every plaque intruding into the lumen is vulnerable to rupture, producing a heart attack. Plaques that produce less severe stenosis (20-50% stenosis) are more vulnerable than more severe lesions. Indeed lesions which are more than 70% cause less than 15% of all heart attacks. So, the identification of any plaque, big or small, calls for vigorous treatment in order to prevent a heart attack.
Diagnosis of heart disease
Diagnosing heart disease is easy when the victim suffers from chest pains (angina) due to significant stenosis of the coronary arteries. Treating and reversing heart disease relieves fearsome chest pains, and diminishes the risk of heart attack. The presence of heart disease can be established by:
* a careful clinical assessment of symptoms
* physical examination of the patient,and
* by tests like ECG, echocardiography, stress echocardiography, treadmill stress test, SPECT and coronary angiography
The most prominent feature of heart disease is discomfort right in the centre of the chest produced by physical exertion, often noticeable when walking after a meal. This may be associated with fatigue and some breathing difficulty. Sometimes the chest discomfort spreads into the lower jaw or the right or left upper limb. Some patients experience no chest discomfort but only jaw pain. These symptoms are caused by inadequate blood supply (oxygen) to the myocardium due to significant heart disease. The chest discomfort or jaw pain caused by heart disease is known as ‘angina’ (from the greek ankhonē meaning strangling). Relief is obtained by resting, and also by placing a nitrate tablet under the tongue.
The chest discomfort can also be triggered by emotional upheaval such as an angry flare-up.
Interestingly, some patients, even with advanced disease suffer no discomfort. This is often observed in patients who lead a sedentary life with very little physical activity. Their physical activity never reaches the intensity that could cause angina.
Some patients, especially diabetics, suffering from advanced heart disease suffer no chest pain because their pain sensation mechanism is disrupted. When these patients exercise, they do in fact develop ischaemia (inadequate blood supply to the myocardial cells) but experience no discomfort. This is called ‘silent angina’ or ‘silent ischaemia’. Once detected, silent ischaemia calls for vigorous treatment with the aim to reverse the disease.
Physical examination may be entirely normal but often reveals one or several abnormalities which point to heart disease:
* abnormal heart sounds
* abnormal heart and pulse rate (very fast or very slow rate)
* irregular heart beat and pulse such as atrial fibrillation, and ventricular ectopic activity
* abnormal blood pressure
Tests for heart disease
The tests carried out to confirm heart disease include:
Certain abnormalities in ECG indicate heart disease. However, a normal ECG does not mean that there is no disease. The reverse is also true – a person with no heart disease could have an abnormal ECG.
Ultrasound sonography is used to evaluate the functional capacity of the heart, contraction of the different segments, and the condition of the four valves.
With echocardiography, the functional capacity (called ejection fraction, EF) of the heart can be measured. An EF of 50-70% is normal. It is often reduced in heart disease but not always so.
Certain abnormalities like impaired or diminished contraction of a segment of the heart (called hypokinesia) signify heart disease. Complete loss of movement of a segment of the heart (called akinesia) is a strong indicator of heart disease. These findings are of great clinical significance. Diminished contraction of a segment means that normal function can possibly be established by restoring blood flow to the affected segment either by coronary angioplasty or by-pass surgery. Total absence of movement of a segment indicates dead tissue and it is unlikely to get better with any treatment. A normal echocardiographic examination does not exclude heart disease.
It needs to be stressed that all echocardiographic tests are subject to operator bias. This means the accuracy of the report depends on the experience and skill of the medical professional recording the echocardiogram.
3) Stress echocardiogram
In this test, a resting echocardiogram is recorded. The heart is then subjected to chemical stress by injecting a drug called dobutamine into a vein in the forearm of the patient. When the heart is adequately stressed, a second echocardiographic examination is carried out. By comparing the two echocardiograms, the presence or absence of significant heart disease can be established.
One parameter that is commonly examined is the ejection fraction (EF). Compared with the EF at rest, a decrease of 4% (or more) following stress is considered indicative of heart disease. Contraction of each segment of the heart is also evaluated in the two echocardiograms. The appearance of new defects after stress, virtually confirms heart disease.
4) Treadmill stress test
In this test, the patient exercises on a treadmill and ECGs are recorded at regular intervals. By comparing the resting ECG with the exercise ECGs, it is possible to identify or exclude significant heart disease. If the patient suffers from significant heart disease (70% or more stenosis), exercise will result in an inadequate supply of blood to the myocardial cells and this will produce an abnormal test. Patients suffering from heart disease with lesions less than 70% will have a normal test result.
The test is inexpensive and can be performed in a basic investigative setup.
This test has its weak points. It cannot be carried out in someone who is physically disabled (such as severe weakness, arthritis). If the resting ECG shows left bundle branch block (LBBB), it is useless to carry out the test because analyzing the ECGs for abnormalities becomes impossible.
This test has another disadvantage. Although it is fairly reliable, it is not always accurate. When patients with significant heart disease are tested, it is expected that they will all test positive but that does not always happen. Most of the patients will show an abnormal response but a small fraction will come up with a normal result. The same applies to patients who definitely have no heart disease. Most of the patients will produce a normal result but some will, unexpectedly, show an abnormal test.
5) Coronary angiography
This is the definitive test for heart disease. This test accurately establishes:
* the presence of heart disease, where the plaque has extended into the lumen of the coronary artery
* the extent and severity of the disease, and
* helps determine the treatment required to relieve symptoms
This test can identify mild stenosis (as small as 10-20%) but the weakness of the test is that it cannot detect plaques confined to the coronary arterial wall.
This nuclear imaging technique is used to detect significant coronary artery disease. The test reflects the blood supply of the different segments of the myocardium (heart muscle). It can identify whether any segment(s) of the myocardium is totally dead (seen as zero blood supply) or salvageable (seen as decreased blood supply). Restoring normal blood flow either by coronary angioplasty or by by-pass surgery will help revive the salvageable segment(s) but not the dead tissue.
Diagnosis of non-significant heart disease – disease confined to the arterial wall or less than 70% stenosis
There are millions of individuals who suffer from heart disease. Most are not even aware they have the disease because they have ‘insignificant’ heart disease: they have plaques either confined to the arterial wall or obstructions of the lumen which are less than 70%. They suffer no chest pains. It is vitally important to identify these individuals and treat them, because it is much easier to get rid of mild, early disease and prevent the formation of further new plaques. Unless vigorously treated, the mild disease will inevitably progress and eventually produce significant disease. Besides, stenosis of 50% and lower are significantly more vulnerable to rupture and heart attack: treatment will prevent this from happening.
Heart disease should be suspected if an individual has several risk factors even if he suffers no chest pain. The possibility of heart disease is directly linked to the number of risk factors – more the number of risk factors present in an individual, higher the likelihood of the disease. Some risk factors like smoking, diabetes, hypertension and abnormal lipid profile carry far more weight than others. If the risk factors indicate a very high possibility of heart disease, the following tests will help in the diagnosis:
- Carotid artery intimal media thickness (IMT). This test is easy to
perform and inexpensive. Ultrasound sonography is used to measure the thickness of the inner and middle layer of the carotid artery. An IMT greater than 1 mm strongly indicates cholesterol plaques in the carotid artery. When present, plaques can often be clearly visualized in the wall of the arteries and intruding into the lumen. Evidence of plaques in the carotid artery is strongly indicative of cholesterol plaques being present elsewhere as well, especially in the coronary arteries and in the arteries of the brain.
- Coronary artery computed tomography (CT angio). Unlike conventional coronary angiography, this test does not involve introducing catheters into the body (i.e. it is non-invasive). A radio-opaque liquid (called ‘dye’) is injected into a vein in the forearm. Images of the coronary arteries are acquired and the severity of stenosis can be accurately assessed. The usefulness of this test lies in its ability to detect and quantify the calcium deposited in the coronary arteries and this can be done without injecting the dye. Calcium is deposited only in cholesterol plaques. If there are no plaques – there will be no calcium deposit. A calcium score of more than 130 units is evidence of heart disease.
If these indicate a strong possibility of heart disease, vigorous management should be initiated to get rid of the disease.
The agonizing fact is that heart disease is the number 1 killer. The disease imposes a heavy economic burden on every victim and, in deed, on the entire nation. Unfortunately, the entire emphasis at present is on diagnosing and treating the disease with expensive coronary artery bypass surgery and
The agonizing fact is that heart disease is the number 1 killer. The disease imposes a heavy economic burden on every victim and, in deed, on the entire nation. Unfortunately, the entire emphasis at present is on diagnosing and treating the disease with expensive coronary artery bypass surgery and angioplasty because this is financially lucrative for hospitals and medical professionals. What we really need are national educational programs on preventing and defeating heart disease. The use of print and TV media can prove very useful. Regular display of simple and short messages focused on healthy lifestyle, diet, and on the importance of taking medicines properly, can easily achieve this goal.
3. IVUS: A special ultrasound probe is introduced into the coronary arteries. A clear diagnosis of the plaques can be established from the images generated by the probe. Plaques that are vulnerable to rupture can also be identified. This technique is a very powerful diagnostic tool but carries some risk of complications, can only be carried in a handful of highly specialized centers and is expensive. For these reasons the reach of this test is pretty limited.