Precautions while taking Warfarin (blood thinner)

Blood thinner

What are the precautions while taking Warfarin (blood thinner) ?

Warfarin is a blood thinner medication used to prevent the formation of blood clots within the heart and blood vessels. It is used in a variety of conditions involving the heart and blood vessels. Though it is a very effective medication, it has a narrow window of safety. This means that the dose has to be carefully adjusted with appropriate blood testing. A test known as prothrombin time with international normalized ratio (PT-INR) is used to adjust the dosage according to the condition for which it is given. Frequent monitoring is needed, because the effect of Warfarin in the body can be influenced by food and other medications which are taken along with it. For example, leafy vegetables and other foods which contain a lot of vitamin K will reduce the effectiveness of the drug. On the other hand certain medications increase the effectiveness of the drug by displacing it from the proteins in the blood, thereby increasing its effective blood level. So it is essential to check PT-INR whenever there is any change in the diet or medication pattern. Concomitant liver disease will also increase the bleeding risk with Warfarin as the factors needed for blood clotting are synthesized in the liver.

While taking Warfarin, a constant vigil has to be there for all potential types of bleeding which may otherwise go unnoticed. If any abnormal bleeding is noted, PT-INR has to be checked. Bleeding may be blood in stools, urine or vomitus. Bleeding into the skin can appear like bruises. Bleeding in the upper intestine (small intestine) manifest as black tarry stools instead of red stools in case of bleeding from the lower intestine (large intestine). Bleeding into brain can manifest a stroke with weakness of one side of the body with or without loss of consciousness.


Evaluation of heart function prior to another surgery

ECG - X-ray Chest - Echocardiogram

What is the purpose of evaluation of heart function prior to another surgery?

The purpose of evaluation of heart function prior to any other operation (surgery) is not just to give ‘fitness for surgery’. Very often surgeries are undertaken in those who are ‘unfit’ as per conventional thinking. This is because of dire necessity of the surgical procedure. For example, a person needing surgery for a major head injury, will be taken for surgery even if he has a significant heart problem. Here surgical treatment of head injury gets priority over the underlying illness of the heart due to its life threatening nature. So it is basically a balancing of risk vs benefit, while evaluating a person for cardiac ‘fitness’ prior to surgery. Similarly if it is a surgery for cancer, even those with a major cardiac illness, may be taken up, of course with all necessary precautions.

Cardiac evaluation prior to other surgeries is meant to give a comprehensive assessment of cardiac status of the individual so that a care plan can be given to the surgeon, anaesthesiologist, physician, nurse, patient and other care givers. Cardiac evaluation report gives suggestions to the team taking care of the patient through the surgery regarding for optimal results, preventing cardiac complications as far as possible. Very often the cardiologist is part of the team taking care of patients with significant heart problems before and after the surgery. Within the operation theatre, it is mostly the anaesthesiologist who takes care of the cardiac status, as they are more familiar with the changes which are likely to occur in the circulatory system during anaesthesia.

What tests are done while assessing the cardiac status of a person prior to surgery?

In addition to routine blood tests done prior to all surgeries, electrocardiogram (ECG), chest X-ray and an echocardiogram (ultrasound imaging of the heart) are the tests likely to be done in case there is a specific request for evaluation of heart function. In certain cases, a treadmill exercise ECG (TMT for short) may also be done. But in many cases, patient may not be fit to undergo a treadmill exercise test, due to the illness for which surgery is being planned. In very rare instances, coronary angiography (injecting radiocontrast material into the blood vessels of the heart and getting cine X-ray images) may also done prior to major high risk surgeries.

What is myocarditis?


What is myocarditis?

Myocarditis is inflammation of the myocardium (middle muscular layer of the heart). Often it is due to viral infection, though it is not a common condition. Inflammation can be so mild as to be hardly noticeable or very severe (fulminant myocarditis) so that the pumping function of the heart is deranged and the individual requires mechanical support for blood circulation. In between there are cases of varying severity. Myocarditis can occur secondary to other major diseases like dengue virus infection or human immunodeficiency virus (HIV) infection.

What are the symptoms of myocarditis?

Mild forms of myocarditis may be asymptomatic and symptoms may be just due to an underlying disease like dengue. Viral myocarditis usually has preceding prodromal symptoms like a general feeling of being unwell, fever, fatigue or headache. Symptoms actually due to the involvement of the heart could be breathlessness, fatigue, giddiness, palpitation (undue awareness of one’s own heartbeat) or chest discomfort. In severe cases, features of heart failure like severe breathlessness, swelling of feet due to fluid collection beneath the skin (edema) or fall in blood pressure (hypotension) may occur. Such a situation needs treatment in an intensive care setting.

Migration of clots to blood vessels of lungs – pulmonary embolism

Clot in lung vessel

What is pulmonary embolism?

Blood clots may migrate along with blood flow from various parts of the body to the lungs and block the blood vessels of the lungs. This condition is known as pulmonary embolism. When only small clots reach the blood vessels of the lungs, only a small portion of the blood vessels of the lung is blocked and may not cause any problem. But when large clots or multiple clots migrate to the lungs and block major blood vessels of the lung or multiple blood vessels, it can cause significant problems. Lack of blood flow to regions of the lung cause wastage of air breathed in, which goes back without being utilized for oxygenating the blood. Hence the oxygen level in the blood falls, causing breathlessness and bluish discoloration of the skin in extreme cases. Blockage of parts of the blood circulation to the lung causes an increase in the blood pressure in the remain blood vessels. High blood pressure in the blood vessels of the lung leads to failure of the right ventricle (lower muscular chamber of the heart) which pumps blood into the lungs. When sufficient quantity of blood cannot be pumped to the lungs, the blood returning to the left atrium (upper chamber of the heart) also decreases, which in turn leads to lower volume of blood pumped into the rest of the body. This causes a fall in the blood pressure of the rest of the body. The individual feels dizziness and may faint in severe cases. It can be seen that massive pulmonary embolism is a life threatening situation demanding immediate medical attention.

Thyroid and heart disease

Thyroid and heart

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

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?

Coronary arteries - blood vessels of heart

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.