Overview – Cardiovascular Disease

00:05 In this lecture, we are going to have a overview of the various cardiovascular diseases that the cardiologists deal with and then we are going to take a typical patient through the initial visit with the cardiologist, how the diagnosis is established, both from clinical findings and from a variety of tests and then we will talk about the therapy of this individual. So, what are the commonest diseases that a cardiologist deals with? Well of course, first, high blood pressure or hypertension.

00:38 This is a very common problem affecting actually approximately 1/3rd of the US population and probably just as common in Western Europe. It is also very common in Asian populations.

00:51 We are going to have an entire lecture on hypertension, but it’s an important factor in the development of atherosclerosis and is one of the commonest things that a cardiologist sees. The next, we have already talked about from the last lecture, and that is hyperlipidemia - elevated cholesterol, particularly elevated low-density lipoprotein cholesterol, which is an important factor in the development of hardening of the arteries or atherosclerosis.

01:21 And of course, here it is, public enemy number one - atherosclerosis. This is hardening of the arteries, the deposition of cholesterol in an inflammatory environment in the arterial wall that leads to heart attacks and strokes and heart failure and kidney failure and a whole variety of things that are constantly keeping the cardiologists working at a very high level. We have very good drugs for this and very good interventional therapy in the catheterization laboratory and in the surgical arena. This is the number one cause of death in the world and consequently, the most common thing that a cardiologist sees. And also, it’s evident these patients often have hypertension and hyperlipidemia.

02:12 Coronary artery disease is the commonest manifestation of atherosclerosis and it is the number one cause of mortality throughout the world. It is manifested by heart attacks, by angina pectoris, which is a squeezing sensation in the heart when people… when the heart is not getting enough blood flow for the amount of work that it’s doing. It’s also a common cause of cardiac arrhythmias, that is electrical short circuits in the heart.

02:43 Cerebrovascular disease is the disease that leads to strokes. It’s also caused, in most instances, by atherosclerosis, but it can also be caused from a small blood clot that forms in the heart during the arrhythmia - atrial fibrillation. The blood clot escapes, goes to the brain, and causes a blockage in an artery that leads to a stroke. And you will remember from the last lecture, I showed you two electrocardiograms - a normal one and the one in atrial fibrillation. The irregular heartbeat in the atria leads to areas of low flow within some of the structures of the atrium and can lead to the blood clot, which can escape and then cause a stroke as well. So, there’s two major causes of stroke.

03:26 One is actual atherosclerotic narrowings or blockages in the blood vessels in the brain and the other is what we call “embolism,” which is a blood clot that is traveling in the bloodstream, usually from the heart and gets into an artery in the brain causing a stroke. The atherosclerotic process is a diffuse disease.

03:50 It’s not just affecting the arteries of the heart, it doesn’t just affect the arteries of the brain, it also affects the arteries of the legs, and consequently, when patients walk, their muscles don’t get enough blood flow. Patients developed discomfort and cramps in the legs that force them to stop walking. Eventually, if the atherosclerotic process in the legs gets bad enough, the cutoff in blood flow may actually lead to gangrene that is death of skin and muscle and bone in the toes and eventually even the foot that requires amputation. So, this is a pretty serious disease as well. And of course, since these individuals have atherosclerosis elsewhere, they are also prone to strokes and heart attacks. The commonest cause of death in a patient with peripheral vascular disease is a myocardial infarction, a heart attack. Cardiomyopathies are heart muscle disease.

04:49 They are frequently caused by things other than heart attacks. Although, in patients who have had a number of heart attacks damaging the left ventricle, they may develop a cardiomyopathy at the end stage of their disease called “ischemic” or lack-of-blood-flow cardiomyopathy. But, there are many, many things that can attack the heart muscle. One of the commoner ones is a viral infection which gets into the heart muscle and damages the heart cells so that the ventricle does not contract normally. Cardiomyopathies are usually associated with reduced left ventricular function because of injury to the heart muscle itself.

05:30 Cardiac arrhythmias, we have already been in on this a couple of times, first in the introduction when I showed you the electrocardiograms and the electrical conduction system in the heart. There are many kinds of cardiac arrhythmias. Some of them generate in the upper chamber of the heart, in the atria. Some of them are generated in the lower chambers of the heart that is the ventricles. Some of them affect the conduction, the electrical conduction system. In fact, this is a whole specialty within cardiology. There are people who do nothing else, but manage cardiac arrhythmias - electrical disturbances in the heart. They are treated, as I have already mentioned in earlier lectures, in a number of ways - with drugs, with ablation, which is actually trying to burn out the arrhythmia focus in the heart with a catheter. They are also dealt with with pacemakers. There’s a whole variety of approaches. This is a very, a very hot area in cardiology research and a very large and expanding one. Cardiac arrhythmias are extremely common. To give you one example, which I told you in the last lecture, 10% of people over age 80 in the United States and Europe have atrial fibrillation. Remember, atrial fibrillation is the irregular heart electrical activity that occurs in the atria instead of the nice, regular rhythm which is normal. Congenital heart disease occurs in a small percentage of births. Probably less than one in several hundred births, a patient will have an abnormality in the heart development. This can consist of holes in the heart, can consist of abnormalities in the valves, can even consist of rearrangements of the pulmonary artery and the aorta coming out of the left ventricle and the right ventricle. Some of these are life threatening within the first few days to weeks or months after birth. Some of them are not even discovered until adult life because they are so mild, but many of them require surgery in early childhood or surgery at a later point.

07:45 Arteriovenous shunts are abnormal connections in the blood circulation. Let’s think about this for a moment. You remember that the blood is carried in the arteries, passes down through continuously narrowing vessels until it reaches the tiny blood vessels, the capillaries which are in close communication with the cells. In the capillaries, oxygen is exchanged for waste products. Then, small veins collect the blood and bring it back to the heart where it is reoxygenated in the lungs and starts on the journey again in the arterial system.

08:23 If there is an abnormal large vessel connecting the artery to the veins, you have a shunt - that is the blood doesn’t get to the capillaries. It doesn’t nourish the cells. It shunts directly from the artery to the venous system. If these shunts are large enough, they can eventually lead to considerable extra work for the heart and can even lead to heart failure.

08:45 They are not anywhere near as common as coronary artery disease, but they are seen and they have to also be identified and treated by cardiologists.

08:57 Hypotension is low blood pressure. Some individuals have a congenital abnormality where their blood pressure is too low. These people are often very tired, very fatigued. They may have lightheaded episodes and they may even faint. There are a variety of individuals who have abnormalities in the automatic or autonomic nervous system that controls blood pressure and heart rate, and these individuals may have a syndrome where they are frequently affected by low blood pressure and even by fainting or near fainting. And there are a variety of drugs and even sometimes pacemakers that can help these individuals.

09:44 Finally, there is disease in the veins and the right side of the circulation. Here, for example, with a long plane flight or with individuals who have cancer or individuals taking birth control pills or who are pregnant, there’s an increase in the likelihood of the blood to clot. When that happens, the clots can form in the legs. Pieces of the clot can break off. And remember the term “embolism”? That’s where the clots travel through the bloodstream. In this case, it’s venous embolism, that is it starts in the blood… in the legs, travels up through the heart and into the lungs and can actually block the blood flow in the lungs. And this can actually be fatal. When these clots arrive in the lungs, it is known as “pulmonary embolism.” Remember the word “embolism,” again, meaning the blood clot has traveled from somewhere else.

10:40 Obesity - Now, you might think, “Obesity - that’s not something that cardiologists deal with.” But, obesity is very important because it often leads to high fat in the blood - hyperlipidemia. It also increases blood pressure and can cause hypertension. It also is a risk factor for diabetes which can affect the kidneys and also increase the risk for atherosclerosis. So, cardiologists are dealing with obesity all the time because it is a major factor in causing other forms of heart disease that is atherosclerosis.

11:19 Endocarditis is a special disease. It’s due to bacterial infection in the heart, usually the heart valves, and this, again, can be a fatal disease. Unfortunately, we had hoped, with antibiotics, that this disease was going to disappear. In fact, it’s becoming more common, partly because more patients with valvular heart disease are living long lives and val-… valves that are affected by heart disease actually are at increased risk to get infected. We will talk about this when we talk about valvular heart disease in a later lecture. In addition, we often give patients drugs which suppress the immune system.

11:59 For example, people with rheumatoid arthritis or people with transplants get drugs which suppress the immune system and increase the risk for infections including infection in the heart which is endocarditis. These patients often require a new valve to be put in in place of the one that’s infected. Now, we already talked a bit about embolism.

12:27 We talked about embolism on the venous system - in the legs, getting up into the lungs, causing pulmonary embolism. Embolism on the left side that is forming in the left atrium and passing out through the ventricle, left ventricle and out into the aorta and can cause strokes, kidney damage and a whole variety of other very unfortunate complications. So, “embolism” is a term that can be used either on the right side of the circulation or the left side and often, the therapy involves the use of anti-coagulants, as we discussed in the last lecture.

13:03 Cardiac trauma - These days there are, as you know, lots of automobile accidents and a variety of other injuries where the patient is struck a severe blow on the chest. This can actually result in both bruising and disruption of some of the cardiac structures, for example, an artery or a valve and often requires urgent cardiac surgery. And these days, knife wounds and gunshot wounds can also injure the heart and also require urgent surgery. The cardiologists are usually not the main individuals involved with the treatment of cardiac trauma. It’s usually done by cardiac surgeons, but we are always involved to help with the complications such as cardiac arrhythmias, heart failure and so forth that can result from the trauma.

13:52 And we are also involved in diagnosing the degree of injury that occurs to the heart.

13:57 Yes, another condition that cardiologists commonly see is bradycardia. “Bradycardia” means “slow heartbeat”. This can occur because of abnormalities related to disease in the electrical conduction system of the heart and sometimes it’s due to an excessive amount of drugs that slow the heartbeat. In either case, there needs to be a change in the medical program and sometimes these patients may need pacemakers to make sure that their heart rate stays at a normal level. Bradycardia can be associated with decreased pumping ability of the heart and, therefore, low blood pressure and these patients may feel markedly fatigued or even lightheaded or even faint. Bradycardia can be treated sometimes with drugs or sometimes we actually cause bradycardia with drugs and we have to back down on the dose of the drugs and they can be treat… bradycardias can be treated with pacemakers. Again, it’s usually the expertise of the cardiac electrical expert known as a “cardiac electrophysiologist,” who gets involved dealing with both tachyarrhythmias which is fast heart rhythms and bradyarrhythmias.

15:09 So, you might ask, “What’s the normal heartbeat?” Somewhere generally between 55 and 90 or 90 to 100. In fact, most of us run in the 60s to 80s most of the time, but of course, when you exercise, you increase your heart rate and when you rest, you decrease your heart rate. Heart rate and blood pressure are changing constantly throughout the day depending upon your activities and the demands that are being placed on the cardiovascular system.