Thyroid and heart disease

How is thyroid linked to heart disease?

Heart disease can occur with both increased function of the thyroid gland and decreased function of the thyroid gland. When thyroid function is increased, heart rate increases and the work load of the heart increases. In severe cases heart failure may occur. A peculiarity of heart failure associated with increased thyroid function is that it is a high output failure unlike the usual heart failure in which the pumping function of the heart is reduced and low output failure occurs. While in low output heart failure the extremities are cold, in high output failure due to increased thyroid function, the extremities of the limbs are warm. Another important issue with increased thyroid function is that the heart rhythm may become irregular. This condition is known as atrial fibrillation, in which the upper chambers of the heart generate very fast irregular signals, but fail to contract well. Hence the blood stagnates in some parts of the upper chambers (left atrium) and clots may form. If these clots migrate to the blood vessels of the brain, a stroke may result.

Reduced function of the thyroid gland is also associated with heart disease. Cholesterol levels go up when thyroid function comes down. This in turn can enhance the chance of plaque build up in the blood vessels of the heart (coronary arteries). When thyroid function is very low, fluid collects in various parts of the body. This may occur within the covering of the heart known as pericardium. Collection of fluid within the covering of the heart is called pericardial effusion. If it is severe enough to compress the heart, it prevents proper filling of the heart and blood pressure falls.

Stroke and heart disease

How are stroke and heart disease related?

Stroke is often due to sudden loss of blood supply to a region of the brain which usually results in paralysis of a part of the body. Stroke could also be due to bleeding into a part of the brain. Strokes and heart disease are linked together in various ways. In general, risk factors for stroke and some forms of heart disease are similar. Strokes due to blocks in blood vessels, can be seen along with blocks in blood vessels of the heart. Stroke can occur after a heart attack as well. Heart attack damages a part of the heart muscle. This can lead to damage of the inner lining of the heart in that region. A blood clot can form on the inner surface of the heart as a consequence. These clots can break away into the circulation and get lodged into a blood vessel of the brain. The clot thus blocks a blood vessel of the brain and causes stroke.

Another type of heart disease which leads to stroke is an abnormal rhythm of the heart known as atrial fibrillation. In atrial fibrillation, there is a fast irregular rhythm originating in the upper chambers of the heart. The rhythm is so fast that effective contractions of the upper chambers cease. This leads to stagnation of blood in certain parts of the left atrium (upper chamber of the heart), where a blood clot can form. These clots can also get dislodged and travel to blood vessels of the brain. They in turn block a blood vessel of the brain and cause stroke.

Another reason for stroke is high blood pressure. When the blood pressure goes very high suddenly, small blood vessels in the brain may break leading to a bleed into the brain matter. This form of stroke (hemorrhagic stroke) is generally more dangerous than a stroke due to blockage of a blood vessel. Even without a bleed, brain function can be altered due to high blood pressure, causing alteration in the level of consciousness. But then that is not a stroke, but called as hypertensive encephalopathy (brain disease due to high blood pressure).

Coronary Steal – Who is stealing what?

This is a revised version of my previous post elsewhere.

Coronary steal is the term given to blood being stolen from one region of the coronary tree by another. It is also called coronary steal syndrome. In fact the term steal is used in vascular medicine for one territory stealing blood from another territory. Another example of steal is subclavian steal in which the arm steals blood from the brain so that the person feels giddiness during arm exercise. Steal occurs when there is obstruction to one vessel which is connected to another. Coming back to coronary steal, it occurs when certain type of vasodilators (blood vessel dilating drugs) are given. The classical example is a drug called dipyridamole. Dipyridamole is both an antiplatelet drug and a vasodilator. When it is given to a person with partial obstruction to a coronary artery, all the coronary vessels dilate. Hence blood will flow preferentially to the non obstructed vessels, reducing the flow in the region of the obstructed vessel. Hence the drug given to improve the circulation will predispose to stealing of the blood into other regions. This is why dipyridamole is not used for this purpose usually. This disadvantage can be used in the form of dipyridamole stress test to bring out the deficiency of blood supply in a suspected case, if the person is unable to undergo a treadmill exercise test due to physical deficits in the legs. Another drug with similar effect is adenosine. Adenosine is used for pharmacological stress test now a days because it is short acting. Any reduction in blood supply to a region of the heart produced by adenosine is quickly reversed and unlikely to lead to long lasting cardiac damage.

Stress and heart disease

How does stress cause heart disease?

Stress and heart disease has various aspects. Stress can lead to increase in risk factors for heart disease as well as precipitate symptoms in a hitherto silent heart disease. Most older persons have build up of plaques in the blood vessels of the heart (coronary arteries). When there is a sudden severe stress, heart rate and blood pressure can shoot up. This can lead to increase of shear stress on the fat plaques in the blood vessels of the heart. A small break may form in the covering of the plaque, exposing the inner cells. Blood components known as platelets adhere to these breaks in the inner surface of the blood vessels and initiate the formation of blood clots. Blood clots in turn block the flow of blood in the vessel, leading to damage of heart muscle known as heart attack.

Sudden stress can sometimes lead to a surge in the blood levels of certain hormones like adrenaline. These contribute to the surges in blood pressure and heart rate. In addition this can upset the heart rhythm leading to life threatening rhythm disorders (cardiac arrhythmia) which can sometimes cause sudden stoppage of the heart (cardiac arrest).

Another manifestation of stress in the heart is the ‘broken heart syndrome’ or stress cardiomyopathy. This was initially described more in elderly females after sudden demise of their spouse. Part of the left ventricle (lower muscular chamber of the heart) becomes enlarged, giving it the name apical ballooning. This occurs in the absence of any blockage to the blood supply. Most of these cases do recover sooner or later. Stress cardiomyopathy has been described along with multiple other forms of stress other than bereavement.

Stress in general changes our life style and we may eat more of carbohydrate and fat. This has long term consequences like increase in body weight, blood sugar and blood pressure. These can further increase the chance of heart disease. Stress increases the blood pressure and blood sugar through hormonal influences even without a change in the diet pattern.

Coronary Angioplasty

Here is one of my old posts elsewhere on Coronary Angioplasty. It is supplemental to my recent post at: https://cardiophile.blog/category/angioplasty/

Angioplasty is a method to remove blocks from important blood vessels. The most common form of angioplasty is coronary angioplasty, the method of removing blocks from the blood vessels supplying oxygenated blood (arteries) to the heart. Coronary angioplasty was originally described by Andreas Gruentzig in 1975. He used a balloon at the tip of tiny long tubes known catheters to dilate narrowed coronary arteries. The procedure is also known as PTCA (Percutaneous Transluminal Coronary Angioplasty). Blood vessels supplying the brain, kidneys and the limbs can also be treated by angioplasty. Coronary angioplasty is usually done when one or more blood vessels supplying the heart are critically narrowed (> 70% decrease in diameter). The most important benefit of angioplasty is symptomatic relief, rather than improvement in survival. The procedure is done under local anaesthesia. The tiny tubes used for angioplasty can be introduced into the body either through the groin or above the wrist. The tubes are threaded back into the main artery of the body called aorta and from the aorta into the coronary arteries under x-ray fluoroscopic guidance. Initially iodine containing contrast dye is injected into the vessels to visualise the sites of narrowing. Read more…

Symptoms of heart disease

What are the important symptoms of heart disease?

Symptoms depend on the type of heart disease. Sometimes there could even be silent heart disease without any symptoms. Many of the birth defects of the heart remain asymptomatic for long periods. Some become symptomatic during another illness or a major stressful event. Occasionally the very first manifestation of a silent underlying heart disease is sudden death. Apart from these two extremes, most significant heart diseases have some symptom or other though there may be a lot of variation between individuals. The severity of symptoms may not correlate with the severity of heart disease in some cases.

Important symptom of heart disease which every one is familiar with is the severe chest pain of a heart attack. As the name implies, it often occurs out of the blue and is quite disabling. A crushing feeling may be felt instead of chest pain, and it may spread to the arms or jaw. It may be associated with profuse sweating or sometimes breathlessness and dizziness. Some even feel an impending doom.

Classical symptom of reduced blood supply to the heart is chest pain brought on by exertion and relieved by rest (effort angina). This indicates gradually increasing blockage of coronary arteries which supply oxygenated blood to the heart. This pain may also spread to the jaw, neck or the arms. Occasionally pain may be felt in the upper part of the stomach. Rarely jaw pain or pain in the wrist occurs without chest pain.

Breathlessness brought on by exertion and relieved by rest is another important symptom of heart disease, though it can be due to lung disease or even reduced amount of hemoglobin in the blood (anemia). Sudden breathlessness during sleep and breathlessness which gets worse on lying down are also important symptoms of some forms of heart disease.

Palpitation or undue awareness of one’s heart beats is another important symptom of heart disease, though it may occur with anxiety and undue exertion as well. Palpitation can be fast, slow, regular or irregular, depending on the abnormality in the heart rhythm.

Some forms of heart disease, especially birth defects of the heart, produce a bluish discoloration of the skin and lips (cyanosis). This is due to reduced content of oxygen in circulating blood. Spitting out blood can also be a symptom of heart disease, though it is more often a symptom of lung disease.

Prolonged fever can occur with infections of the heart valve. Joint pain and swelling can occur in infections of the heart valves as well as in rheumatic fever, which can affect the heart valves.

Stroke or sudden weakness of one part of the body can be an indirect symptom of heart disease. Atrial fibrillation, an abnormal rhythm of the upper chambers of the heart, can cause clots to form in the heart. These clots can move out of the heart and block a blood vessel in the brain causing stroke. Similar clots can form in diseases of heart valves, where there is obstruction to blood flow.

Palpitation

What is palpitation?

Normally our heart is beating regularly at a rate between 60-100 per minute. But we are not aware of it. In certain circumstances, we become aware of our own heart beat. This is known as palpitation. Very often palpitation is just a manifestation of anxiety. When you are stressed or with exercise, the heart races and we become of our heart beating fast. Though most often palpitation is harmless, in some situations it could be a manifestation of a dangerous disease. For example, abnormal heart rhythms can cause palpitation. Very fast rhythms can be regular or irregular. Sometimes it may not be continuous palpitation, but feeling of an occasional flutter in the chest. This is due to transient irregularity in the heart rhythm, which is often of not much significance.

Serious forms of palpitation occurs in those with severe heart disease – either electrical or structural. Structural abnormalities of the heart which damage the heart muscle or heart valves can cause paliptation due to extra load which it gives the heart. Electrical disorders of the heart often produce either very fast rhythms or very slow rhythms, both of which can be life threatening if severe.

One of the simple tests to analyse the heart rhythm in case of palpitation is an ECG. Structural damage to the heart can be assessed by ultrasound imaging of the heart known as echocardiography. Both these tests are commonly done for evaluation of heart disease. Other more advanced tests are needed only in selected cases. If the palpitation is only occasional, it can be recorded by long term ECG monitoring known as Holter monitoring (typically 24-48 hours) or event monitoring (one week to three months). If still longer recording is needed, we have implantable loop recorders – small devices which can be implanted under the skin under local anaesthesia, which can record electrical abnormalities of the heart for up to 3 years. These devices have wireless options which can relay the signals to a device at home which in turn can transmit it to a central server by mobile networks. The central server could be even located in another continent!