How is coronary heart disease diagnosed?
Coronary heart disease (coronary artery disease, coronary artery heart disease, ischemic heart disease) is usually suspected by the symptoms. Typically it is a central chest pain or discomfort induced by exercise and relieved by rest. But this need not be the case always. Pain of heart attack may appear all of a sudden and does not get relieved by rest. Still it is an important manifestation of coronary heart disease. Other symptoms associated with chest pain could be pain in the jaw or arms, excessive sweating along with pain or sometimes breathlessness or dizziness. First investigation to be done is usually an ECG (electrocardiogram). When a heart attack is suspected, other investigations done in the emergency department are a bedside echocardiogram and a blood test for Troponin, which is released into the blood when heart muscle is damaged. Finally an emergency coronary angiogram may be done if there is evidence of a heart attack. In the outpatient setting, a treadmill exercise ECG (treadmill test) can be done in stable patients resting ECG does not give a diagnosis. Other advanced tests are coronary CT angiogram and nuclear scan of the heart.
LMCA: Left main coronary artery; LAD: Left anterior descending coronary artery (blood vessels supplying oxygenated blood to the the heart muscle) – as seen on coronary angiogram (X-ray imaging after injecting iodinated contrast into the vessel)
What is ischemic heart disease?
Ischemia means a decrease in the blood supply. Hence ischemic heart disease means blood flow to the heart muscle is reduced. Ischemic heart disease is also known as coronary artery disease. Usually this occurs due to partial or complete blocks in the coronary arteries which supply oxygenated blood to the heart muscle. It could also occur due to transient contraction of the muscle of the blood vessel, known as ‘coronary vasospasm’. Ischemic heart disease due to partial blockage of the blood vessels usually manifest as chest pain on exertion (effort angina). When the block is near total or total there could be chest pain at rest as well. Then it is called unstable angina or sometimes when there is damage to the heart muscle it results in heart attack (technical term: myocardial infarction).
Does ischemic heart disease always manifest with chest pain?
Ischemic heart disease can have other manifestations like breathlessness on exertion, dizziness, undue sweating on exertion, or pain in the jaw, wrist, neck or back. These are known as anginal equivalents, meaning symptoms of ischemic heart disease other than chest pain. Occasionally there is no symptom at all and it is detected on routine medical evaluation for some other reason. Then it is called silent ischemia or even silent heart attack.
Is there any difference in the significance between silent and manifest ischemic heart disease?
Significance is the same for silent and manifest ischemic heart disease. But the risk is probably more for the silent one because there is no warning symptoms and the individual would not take care and exert beyond what his medical condition permits and may end up with more severe problems.
These days many are worried about blocks developing in the blood vessels of the heart because it is one of the leading causes of illness and death. Most of the blocks in the blood vessels of the heart do not occur all of a sudden though heart attack is usually an abrupt event. Material which block the vessels including fat deposit develop over a long period of time, just like in an old rusted water pipe. This gradually decreases its lumen size, leading to poor blood supply to the region of the heart muscle supplied by it. But a vessel can get blocked suddenly when one which is partially blocked by fat deposit gets totally blocked by a clot forming over the partial block. This is often the mechanism behind a sudden heart attack, which can even be fatal.
Risk factors for blocks in blood vessels of the heart (coronary arteries)
Risk factors could be modifiable and non modifiable ones. Male gender and advancing age are associated which higher frequency of blocks in blood vessels. These two are important non-modifiable risk factors, along with genetics and ethnicity. Certain families have a higher incidence of heart attacks among their members. Similarly people from some ethnic background are more prone for heart attacks than others.
Though we can’t do much about non modifiable risk factors, there are quite a few modifiable risk factors. The well known ones are high blood sugar (diabetes mellitus), high blood pressure (hypertension), high body weight (obesity) and smoking. Though stress itself does not causes blocks to build it blood vessels, it can act in multiple ways. Stressed individuals are likely to take solace in excessive eating as a method of relief and may become obese. Sudden stress can increase the heart rate and blood pressure which can precipitate a heart attack in an individual already having partially blocked blood vessel. The sudden increase in blood flow speed can cause fissures in the partial blocks which have built up in the blood vessels. This exposes a raw area in the blood vessel where clots can easily form and convert the partial block into a total block.
Risk factor modification by changes in lifestyle is an important intervention in the prevention of heart attack. Reducing total food intake to cut down obesity, regular walking program for physical fitness, restriction of fatty foods and smoking cessation are good time tested methods for remaining fit.
Blood vessels supplying oxygenated blood to the heart are known as coronary arteries. The two important coronary arteries are the right coronary artery (RCA) and the left main coronary artery (LMCA). Left main coronary artery has two branches – left circumflex coronary artery (LCX) and left anterior descending coronary artery (LAD). Each of these give several branches to supply the heart muscle. Both the left and right coronary arteries arise from the root of the aorta, the biggest blood vessel arising from the heart, carrying blood to the whole body.
Blood returning from the heart, containing deoxygenated blood are known as coronary veins. The biggest coronary vein is the coronary sinus (CS), which drains into the right atrium, the upper right chamber of the heart.
Left anterior descending artery (LAD)
LAD is so called because it descends on the front (anterior) surface of the heart. It is by far the most important blood vessel supplying the heart muscle so that blockage can be catastrophic. Hence it has earned the name ‘widow maker‘ artery. Blockage of LAD causes anterior wall myocardial infarction – damage to the heart muscle in the front portion of the left ventricle, which is the lower muscular chamber of the heart. Significant damage to the musculature of the left ventricle can impair the pump function of the heart very much so that the blood pressure can fall very low.
Left circumflex coronary artery (LCX)
LCX, as the name implies, curves around the left border of heart, to run in a groove between the upper and lower chambers of the heart (atrioventricular groove or AV groove). It supplies blood to the left side and back of the left ventricle and left atrium (upper left chamber of the heart).
Right coronary artery (RCA)
RCA gives branches to the right atrium right ventricle (lower right chamber of the heart) and part of the back side of the left ventricle. Blood supply to two important electrical structures of the heart can be from the RCA. The upper one is known as sinus node (SA node), which is the usual pacemaker of the heart, causing the heart to beat regularly. The lower one is atrioventricular node (AV node) which is situated at the junction between the upper and lower chambers of the heart (AV Junction). AV node passess on the signals conducted down from the SA node, into the lower chambers of the heart after a short delay. The delay is useful to delay the contraction of the lower chambers for a short while after the contraction of the upper chambers. This allows completion of emptying of the upper chambers into the lower chambers, before they start contracting.