60 PATHOLOGICAL CARDIAC ACTION. 



00 the upper limb the valve is actel on only at each systole of the heart, blood is driven beyond 

 it, bat daring diastole it closes and no blood can return. This goes on until the pressure beyond 

 the valve in the mercury manometer is the same as in the heart. If the valve be reversed, it is 

 converted into a minimum manometer.] 



49. PATHOLOGICAL CARDIAC ACTION. Cardiac Hypertrophy. All resistances to the 

 movement of the blood through the various chambers of the heart, and through the vessels com- 

 municating with it, cause a greater amount of work to be thrown upon the portion of the heart 

 speciallv related to this part of the circulatory system ; consequently, there is produced an 

 increase in the thickness of the muscular walls and dilatation of the heart. If the resistance or 

 obstacle does not act upon one part of the heart alone, but on parts lying in the onward direc- 

 tion of the blood-stream, these parts also subsequently undergo hypertrophy. If in addition 

 to the muscular thickening of a part of the heart, the cavity is simultaneously dilated, it is 

 spoken of as eccentric hypertrophy or hypertrophy with dilatation. The obstacles most 

 likely to occur in the blood-vessels, are narrowing of the lumen or want of elasticity in their 

 walls; in the heart, narrowing of the arterial or venous orifices or insufficiency or incompetency 

 of the valves. Incompetency of the valves forms an obstruction to the movement of the blood, 

 by allowing part of the blood to flow back or regurgitate, thus throwing extra work upon the 

 heart 



Thus arise (1) Hypertrophy of the left ventricle, owing to resistance in the area of the 

 systemic circulation, especially in the arteries and capillaries not in the veins. Amongst 

 the causes are constriction of the orifice or other parts of the aorta, calcification, atheroma, and 

 want of elasticity of the large arteries and irregular dilatations or aneurisms in their course ; 

 insufficiency of the aortic valves, in which case the same pressure always obtains within the 

 ventricle and in the aorta ; and, lastly, cirrhosis of the kidneys, whereby the excretion of water 

 by these organs is diminished. Even in mitral insufficiency, compensatory hypertrophy of the 

 left ventricle must occur, owing to the hypertrophy of the left atrium in consequence of the 

 increased blood-pressure in the pulmonary circuit. 



(2) Hypertrophy of the left auricle occurs in stenosis or constriction of the left auriculo-ven- 

 tricular orifice, or in insufficiency of the mitral valve, and it occurs also as a result of aortic 

 insufficiency, because the auricle has to overcome the continual aortic pressure within the 

 ventricle. 



(3) Hypertrophy of the right ventricle occurs (a) when there is resistance to the blood- 

 stream through the pulmonary circuit. The resistance may be due to (a) obliteration of large 

 vascular areas in consequence of destruction, shrinking or compression of the lungs, and the 

 disappearance of numerous capillaries in emphysematous lungs ; (j8) overfilling of the 

 pulmonary circuit with blood in consequence of stenosis of the left auriculo-ventricular orifice, or 

 mitral insufficiency consequent upon hypertrophy of the left auricle resulting from aortic 

 insufficiency, (b) When the valves of the pulmonary artery are insufficient, thus permitting 

 the blood to flow back into the ventricle, so that the pressure within the pulmonary artery 

 prevails within the right ventricle (very rare). 



(4) Hypertrophy of the right auricle occurs in consequence of the last-named condition, and 

 also from stenosis of the tricuspid orifice, or insufficiency of the tricuspid valve (rare). 



Artificial Injury to the Valves. If the aortic valves are perforated, with or without 

 simultaneous injury to the mitral or tricuspid valves, the heart does more work ; thus the 

 physical defect is overcome for a time, so that the blood- pressure does not fall. The heart seems 

 to have a store of reserve energy which is called into play. Soon, however, dilatation takes 

 place, on account of the regurgitation of the blood into the heart. Hypertrophy then occurs, 

 but the compensation meanwhile must be obtained through the reserve energy of the heart 

 (0. Roscnbaeh). 



Impeded Diastole. Among causes which hinder the diastole of the heart are copious effusion 

 into the pericardium, or the pressure of tumours upon the heart. The systole is greatly inter- 

 fered with when the heart is united to the pericardium and to the connective-tissue in the 

 mediastinum. As a consequence the connective-tissue, and even the thoracic wall, are drawn 

 in during contraction of the heart, so that there is a retraction of the region of the apex-beat 

 during systole, and a protrusion of this part during the diastole. 



[Palpitation is a symptom indicating generally very rapid and quick action of the heart, the 

 pulsations often being unequal in time and intensity, while the person is generally conscious of 

 the irregularity of the cardiac action. It may be due to some organic condition of the heart 

 itself, especially where the cardiac muscles are weak, in cases of dilatation and hypertrophy of 

 the left ventricle, where the heart is gradually becoming unable to overcome the resistances offered 

 to its work, and especially during exertion when the heart is taxed above its strength. It may 

 also occur where the blood -pressure is low, as in anemia, so that the heart contracts quickly, 

 there being little resistance opposed to its action. The excitability of the cardiac muscle may 

 be increased as in fatty heart, when very slight exertion may excite it often in a paroxysmal 

 way. In other cases, it is nervous in its origin, being either direct or reflex. In very emotional 

 and excitable people (especially in women) it is easily set up, and in some people it may be 



