History on Heart and Heart Diseases

Heart is considered as the central organ of the body since time immemorial. In fourth century B.C. the Greek philosopher Aristotle identifies heart as the centre of vitality in the body, the first to form according to his observations on chick embryos.

In second century A.D. Galen in his writings had described about the common beliefs of heart as the source of body’s innate heat and the organ most closely related to soul. He argued that the expansion and contraction of the heart was a function of its role as an intelligent organ. According to him, heart is a hard flesh which is not easily injured.In hardness, tension, strength and resistance it overpowers all others and no other organ work such continuously as heart does.

Avicenna, in his Canon of Medicine, mentioned heart as the vital power or innate heat within the body. He identified the pulse as a movement in the heart and arteries which takes the form of alternate expansion and contraction.

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At the time of renaissance people come to know about the actual structures of heart having four chambers. Leonardo Da Vinci with his great artistic observations drawn the heart with a great accuracy. He had investigated the coronary arteries.

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William Harvey who was the physician of King Charles-I, has discovered how blood moves from the right ventricle through the lung and into the aorta, then peripheral vessels and back into the lung. The French philosopher Rene Descartes, who has accepted Harvey’s theory and too his ideas a step further he has described heart as a pump and specifically a combustion engine.

Heart diseases are now the number one killer in the world as hundreds of thousands suffer from non-fatal heart attack. This disease of heart attack has always plagued the human race. Narrowing of arteries and deposition of atherosclerosis plaque because of the cholesterol deposits has always affected the humans whether now or then at the Egyptian times. Egyptian mummies, some 3500 years old had evidence of atherosclerosis according to researchers. This can be because of the high class Egyptians eating a lot of fatty meats from cattle, ducks and geese, and using a lot of salt for food preservation.

Angina, literally meaning tightness in the chest, is often an indicator of heart disease which has puzzled many physicians. First described in 1768, it was believed to be because of the narrowing of coronary arteries, thought others thought it was a harmless condition. William Osler has studied extensively on angina. James B. Herrick concluded that the slow, gradual narrowing of the coronary arteries could be a cause of angina. He is credited for invention of the term “heart attack.”

In twentieth century a lot of studies were conducted on heart and many insides were revealed in details. Doctors began to experiment with coronary arteries with catheters. The credit of first cardiac catheterisation goes to German physician Werner Forssman (1904-1979) who experimented on himself. In 1948, National Heart Institute initiated the Framingham Study, the first major study to understand heart disease. In 1949, the term arteriosclerosis was added to the International Classification of Diseases.

In 1960s and ’70s coronary artery bypass surgery and angioplasty were started to treat heart disease. In 1980s use of stents to open of narrow arteries become common practice. Now we know how to treat narrowed arteries and lengthen and improve quality of life. Though we have learned from the Egyptian mummies, Leonardo Da Vinci’s paintings, and reached a lot ahead but still we don’t know it all.

 

A brief details about the Heart

Heart exposed after sternotomy

Heart is a blood pumping muscular organ of middle mediastinum having 3 layers (outer epicardium, middle mesocardium and innermost endocardium) covered by  fibrous pericardial sheath and having four chambers, two on the left (left atrium and left ventricle) and two on the right (right atrium and right ventricle).

Pericardium:

Pericardium along with heart also cover the mediastinal great vessels. The outer wall of pericardial sac consists of outer fibrous and inner serosa. Histologically fibrous is fibrocollagenous tissue while serosa is composed of mesothelial cells. Laterally, pericardium forms medial walls of pleural space. Inferiorly, pericardium is the superior surface of central tendon of diaphragm. Anteriorly pericardium is loosely joined to xiphoid process and sternal manubrium by ligamentous structures.

Left Atrium:

It has four basic parts-1. left atrial appendage 2. the vestibule and 3. the venous component. It is separated from right atrium by the septum- interatrial septum. Unlike of the right atrium, the pectinate muscles are confined within the appendage and do not extend around the vestibule. Because of the the anchorage by the four pulmonary veins, the left atrium is fixed posteriorly.

Left Ventricle:

It has mainly three components- 1. the inlet, 2. the trabecular and 3. the outlet portion. The inlet portion contains the mitral valve and its supporting tension apparatus. The outlet portion supports the aortic valve.  The septal surface of outflow tract is characteristically smooth, and down this smooth surface runs the fanlike left bundle. The landmark for descent of left bundle branch is the membranous septum immediately beneath the commissure between right coronary and non coronary leaflets of the aortic valves.

Right Atrium:

Right atrium like that of the left atrium has also three parts – 1. the appendage, 2. vestibule, 3. venous component.

Externally the junction of the right atrial appendage and the venous component is marked by a groove called the terminal groove.  The appendage has pectinate muscles. The constant feature of the morphologic right atrium is that the pectinate muscles of appendage extend all the way around the parietal margins of the AV junction. Sinus node is a spindle shaped structure that lies within the terminal groove in a sub pericardial portion. Sinus node artery usually courses through the anterior interatrial groove towards the superior cavoatrial junction. From surgical point of view the entire superior cavoatrial junction is a potential surgical danger area.

Right Ventricle:

Right ventricle has three parts- 1. inlet, 2. trabecular and 3. the outlet portion. The inlet portion contains tricuspid valve and its tension apparatus. A distinguishing feature of the tricuspid valve is the direct septal attachment of its septal leaflets. Trabecular portion is a supra ventricular crest portion of right ventricle is the prominent muscular shelf separating the tricuspid and pulmonary valves. The outlet portion is a complete muscular structure, the infundibulum, which supports leaflets of the pulmonary valve. Another important feature of the right ventricle is a muscular column called trabeculae septomarginalis. This trabeculation has a body which divides superiorly into anterior and posterior limbs. The anterior limb runs up into the infundibulum and supports the leaflets of pulmonary valve. The posterior limb extends backward beneath the inter ventricular membranous septum to run into the inlet component of ventricle. The medial papillary muscle arises from this posterior limb.