The heart is a unique
I just returned after attending an international conference on cardiovascular diseases at Winnipeg, Manitoba, Canada. The conference was organised under the aegis of the International Society of Heart Research and I had the honour of being invited to speak on an area of cardiovascular disease in which I have been deeply interested for the last many years. A distinctive feature of this conference which made one feel proud was that the conference was organised by two distinguished scientists of the Indian origin, both hailing from Punjab. Prof Niranjan S. Dhalla, who was the Chairman of the conference, hails from a village near Batala and Dr Pawan K. Singhal, who was the organising secretary, comes from Malerkotla and is a product of the Department of Biophysics, Panjab University.
Heart disease is
already the No. I killer in the developing world and even at the
global level it is soon going to replace diarrhoeal and resporatory
diseases as the top killer diseases. Therefore, a frantic race is on
to find solution to the epidemic and the conference reflected that
activity. Our country is also in the grip of this disease and younger
and younger people are falling victim to disease for various
It is worthwhile to know certain basic facts about the anatomy and physiology of the heart before we talk about the afflictions of this very sturdy yet sensitive organ. It is amazing how recent our knowledge about cardiovascular physiology is.
Heart is probably the most efficient, durable and self-sustained pump ever devised by Nature. A healthy heart beats anywhere between 60-80 times a minute amounting to 1,00,000 times a day and nearly 35 million times a year. Anybody can calculate as to how many times the heart would have beaten in a person living up to 100 years without maintenance and lubrication. Heart is a conical organ placed somewhat obliquely in the chest behind sternum between two lungs and in front of the food pipe and the spine. It has four chambers separated by a set of valves which allow the blood to flow in one direction only. The two sets of small chambers are known left and right atrium and the big chambers are known as left and right ventricles. The left ventricle is the strongest and the biggest chamber which pumps fresh oxygenated blood into the biggest artery of the body, aorta. The blood reaches every nook and corner of the body, delivers nutrients and oxygen to the tissues and returns via the veins (bluish in colour and seen superficially under the skin) bringing with it the waste products of the body and carbon-dioxide generated by tissue respiration.
This blood comes back to the right side of the heart and the right ventricle pumps this into the lungs where the oxygen is imbibed and the carbon-dioxide delivered to the lungs and finally breathed out. This relatively small pump measures 12x9x6 cm and weighs nearly 250 - 350 gm depending upon the age and sex of a person. It performs its work with such precision and automatic rhythm that one marvels at the ingenuity of Mother Nature. The automatic contraction is initiated and controlled by the electrical system of the heart which generates the electrical impulses which traverse through various chambers in a systematic manner. These chambers contract not only rhythmically but in a very programmed manner so that blood flows across the chambers to the body and back to the lungs in a very coordinated manner.
On an average, about 5 litres of blood is pumped every minute by the heart and this is known as the cardiac output. But there is an automatic increase and decrease depending upon the need of the body at a given time — exercise for instance.
Before we go on to the coronary artery disease itself, I would like to define certain diseases which are referred to in relation to the heart. Some of these are overlapping and create confusion for the layman.
This refers to various defects in the development of the heart which can take place and be present at birth or after sometime. These defects may include relatively minor defects like a hole between two chambers or an abnormal communication between two major arteries. But this can present a major defect and the child may be blue right at the birth. The heart may be occasionally placed on the right side of the chest.
In this group of diseases the main defect is that one of the valves of the heart, may be either narrow so that blood cannot easily flow through it or a valve may be incompetent and leak after the contraction of the chamber behind it. The defect in the valve may also be congenital sometimes. But the major cause of these valvular diseases in our country is rheumatic fever. In this group of diseases from which both children and young adults suffer from, the commonest valve involved is the mitral valve which separates the left atrium and left ventricle. This group of diseases plays havoc in case of young females during pregnancy.
In this disease, the heart is affected by continuous high blood pressure and prominently leads to thickness of the left ventricle and if not checked properly can lead to heart failure and other problems.
The heart is enclosed in a thin sheath known as pericardium. This can get inflamed due to diseases like tuberculosis and the fluid may collect around the heart producing difficulty in contraction and can sometime create an emergency situation where the blood flow to the heart is impeded.
In this group of diseases, chronic inflammation of the lung, as in the case of smokers, flow of blood from the right side of the heart to the lungs is not free and produces congestion in the right side of the heart. This leads to what is known as right side failure with congestion of the liver and swelling of the feet.
Ischaemic heart disease
Ischaemia implies that there is not enough oxygen supplied to a particular tissue. If the coronary arteries, cannot deliver the blood to the heart in a required amount, the heart suffers from ischaemia, producing various syndromes like:
Angina:The patient may be symptomatically free while resting but during physical exertion or emotional disturbances or any other activity requiring extra oxygen, the blood supply is not enough and the patient gets pain. The pain may occur in the chest and radiate to the left arm and sometimes to the right arm, the neck or upper abdomen. The anginal pain should get relieved on resting.
Myocardial infarction (heart attack): In this syndrome, the lack of blood supply produces not only pain like angina but goes on producing necrosis or death of a particular portion of the heart, thus producing irreversible damage to that portion. In this syndrome the pain lasts longer, is often more severe and accompanied by a sense of weakness and sweating. There may be a state of confusion, fall in blood pressure or a frank state of shock. Unfortunately, many times such an attack can prove fatal right in the first episode.
Unstable angina: This is the condition which may be considered to be between a simple stage of angina and the myocardial infarction. Here the anginal pain becomes very frequent, comes on minor provocation and may show more ECG changes. This condition should be taken seriously both by the patient as well as the doctor.
Ischaemic heart disease can sometimes be totally painless and thus misleads the patient and the doctor. This happens more often in diabetics and the elderly persons.
Diseases of the conduction system of the heart: This is a broad group of diseases in which problem may lie in the pace-maker or the conduction system of the heart as described above. This may be a simple missing of the beat or very rapid or irregular heart rate.
In the next column we will discuss the genesis of coronary artery disease and ischaemic heart disease and what can be done about it.
(To be concluded)