IT has always seemed passing strange to me that writers on cardiac disease, with one accord, entirely ignore the subject of the elasticity of the cardiac muscle, and the very important part it plays in the economics of that organ. One does not wish to deal, more than necessary, with superlatives, but if ever they are justified it is when writing of the neglect of a subject, of such prime importance, as the elasticity of the cardiac muscle. It is, indeed, of essential importance, and it is impossible to elucidate many cardiac sufferings, without taking it into account, or to manage the diseased or crippled heart intelligently. Certain it is that it is impossible to give an intelligible and rational account of cardiac diseases without taking it into consideration.
No complete solution of any problem can be reached by leaving out one of the essential factors. It resembles the attempt to solve a complicated problem in Higher mathematics, with one or more of the essential factors left out. True it is that some sort of a solution can be given, for many Mathematicians are “clever fools,” and do not hesitate to introduce some additional factor, if the answer appears likely to be very far “out.” But the physician must not imitate such tactics, clever though they be; for he is dealing with the lives of patients, who have committed themselves to his care, and expect to get a “square deal.”.
The heart itself is developed from an elastic and contractile muscular tube. The primary vertebrate heart is formed by a modification of this muscular tube. In the lowest division of the Vertebrata, the Fish, the heart consists of one auricle and one ventricle. The walls of both auricle and ventricle contract rhythmically, the auricle sending the blood into the ventricle, and this, when it contracts, sending the blood into the bulbus arteriosus. From the bulbus the blood passes through the branchial arteries to the gills, where it takes up oxygen from the water, and the blood, then flows into he aorta and thence to the various organs of the body.
It we go a step higher, to the Amphibia, e.g. the frog, the heart consists of two auricles and one ventricle. The right auricle receive venous blood from the body by means of the venae cavae, and forces it, by contraction, into the ventricle. From the ventricle the blood passes into the aorta, from whence it is carried, partly by the pulmonary artery tot he lungs, partly by arteries to the different organs of the body. The blood that has passed through the lungs and has been arterialised, flows through the pulmonary veins to the left auricle, whence it passes into the ventricle and mixes with the venous blood, which is coming from the right auricle. The bulbus aortae in the frog is divided into two parts by means of a spiral valve, by which a partial separation of the blood coming from the right and left auricles is effected.
In the Reptilia the heart is much the same as in the Amphibia. But from the single ventricle in REptilia there proceed a distinct aortic and pulmonary trunk, whereas in Amphibia there is only a single arterial trunk.
In Birds and Mammals the heart has become entirely divided into two halves, each with two cavities: the two halves have no functional connection with each other. These two halves may be looked upon as two highly complicated pulsatile bulbs, one sending the venous blood through the lungs, the other placed beyond the lungs to send the blood through the body. But the mammalian heart is the lineal descendant of the simple pulsatile elastic bulbs of the fish.
But the pulsatile bulbs themselves are mere modifications of the primary elastic tubes, and therefore we must assume that the muscle of the heart is elastic as well as contractile, and that this descends to the more complicated and elaborate pulsatile and elastic bulbs of the highly developed mammalian heart. The whole vascular system is distensible and elastic, and with this we must include the heart itself, as elastic and contractile, since it is developed from a tube which is itself elastic and contractile. We thus see that in the case of the heart evolution is very evident, and marked, from the lowest vertebrate to the highest, the highest form being involved in the original plan, to be evolved when the time was ripe.
There can be no doubt that the heart of the human foetus passes through all those various stages, en route to the higher mammalian heart-a sort of rapid recapitulation of the mammalian heart-a sort of rapid recapitulation of the various stages from the fish-heart to that of Man (homo). Occasionally a child is born with a heart clinically indistinguishable from the Reptilian form.
Such a child may live to grow up, with special care as to feeding and warmth-especially warmth. In fact such a child would have to live in rooms kept constantly at one temperature such as is used in the reptile house at the Zoo. Such an one could probably live to thirty or forty years of age, under the very best circumstances. I do not think that a child with a fish or amphibian heart could live anywhere for long, except in utero.
In children and young adults the elasticity of the heart muscle is small but perfect, i.e. it readily stretches, when on exertion, an extra supply of blood is sent to it, and returns to its original size when the effort is over. How long a heart is “young” in this sense, it is impossible to state. This will vary with each individual person, depending. This will vary with each individual person, depending, not doubt, largely on the quality of the “tubing” handed on from a previous generation.
Here heredity plays a most important part. Some hearts may be young and elastic at eighty, while others are old and the muscle rigid at forty. So far as the word “age” is used in respect to the heart, it is not a mere matter of years or almanacs, or birth certificates.
The elasticity of the young and healthy heart is small but perfect. It is small in amount, because it readily extends, i.e. the heart dilates easily, but repeatedly regains its former size, provided it has not been overstretched. But here can be no doubt that as years advance from youth to old age this elasticity gradually diminished, becoming less perfect in quality, so that the heart finds it more and more difficult, both to stretch and to return to its former size, i.e. in accommodating itself to varying amounts of extra blood and in stretching without pain.
There can be no doubt that this diminished elasticity is a simple and adequate explanation of the “effort syndrome,” which may be regarded as one form of Angina pectoris, for visceral pain is always due tot he attempt to stretch a tissue which will not stretch, or which resists stretching very strongly, as the heart- muscle with defective elasticity, or a band of white fibrous tissue, e.g. when the edge of a ruptured semi-lunar cartilage of the knee-joint slips in between the joint-surfaces of the femur and tibia, and an attempt is made to straighten the leg, the pain is excruciating, due to stretching of the ligaments.
In all severe, athletic efforts , such as racing, cycling, boat- racing, etc., if the heart is to come through the ordeal unharmed its elasticity must be perfect. I have not doubt that in the race, the hearts of the rowers would be found to be dilated from three-quarters to an inch all round, but if the men are in “good form” this will disappear in the course of a few hours, and the heart resume its normal size. But if any one of them suffers from defective elasticity of the cardiac muscle, or a bad quality of “tubing” having been handed down to him from his forefathers, the heart will not not recover, but remain dilated and crippled to the end of his life.
It is in such efforts that the elasticity of the heart is of such vital importance, and therefore it is only the young (and only some of them) that can undertake such ordeals with safety. The question up to what age it is safe to undertake such violent athletic exercise is a difficult one to answer. It will be easily understood that no definite age can be states, for what might be safe to one young man at a given age, might be quite unsafe to another.
So much depends on the quality of the heart-muscle, and the quality of the “tubing,” i.e. the arteries. But there can be no doubt that there is an age in every life beyond which it is dangerous to undertake sudden severe and prolonged physical exertion, as in boat-racing, cycling, running, etc. Also for such severe exertion it is important that the athlete be in “good form,” not resulting from a few months intensive training merely, but to be perpetually training to keep the muscle of the heart in “good form.” To this end the athlete should have a large supply of sugar in is food-mono-saccharides for preference, as honey, grape-sugar, glucose, etc.