Differential Diagnosis.—Nervous pal pitation does not give the sensation of strength in the cardiac impulse, although if long continued it merges into hyper trophy. The sounds are more valvular and have a certain "irritable" character.
Dilatation has a feeble impulse, com ing against the chest with a weak slap. The first sound at the apex has less mus cular quality than in health, while in hypertrophy the difference is the other way. In other organs we notice signs of failing compensation. There are dull ness and moist Tales at the base of the lungs or even hydrothorax. The liver is enlarged. Dependent parts are cedem atous. The urine is scanty, high-col ored, with an excess of urates and more or less albumin.
Care must be taken not to mistake a displaced heart for an enlarged one, whether the change in position be due to thoracic tumor, pleural effusion, or pressure through the diaphragm. Again, the retraction of the lung because of chronic phthisis or failure to expand after pleurisy may expose a normal heart in an abnormal way. On the other hand, emphysema may mask actual hyper trophy. In a complicated case under my care a left-sided pneumothorax, limited by adhesions, acted similarly.
The area of dullness in pericardial effusion is triangular, with the base downward. That of a generally-hyper trophied heart is ovoid. Moreover, the feeble impulse and distant heart-sounds would at once exclude hypertrophy.
It is advisable in every case to estab lish the cause of the hypertrophy. When this can be done it confirms the diag nosis,—besides having a possible influ ence upon treatment.
results from increased demands upon the circulation. An essential condition for its develop ment is a fair degree of cardiac and sys temic nutrition. A patient far advanced in phthisis cannot develop hypertrophy, nor will greatly-occluded coronary arter ies supply to the myocardium the req uisite material for new growth. The causes of hypertrophy may be enumer ated as follows: 1. Obstruction to the general circulation, as occasioned by coaretation of the aorta, hypoplasia of that vessel, or compression of it by de formed chest-walls or tumors.
Aneurism might be expected to cause hypertrophy, but it seldom does, unless associated with aortic regurgitation. Atheroma of the aorta is set down as productive of hypertrophy. It embar rasses the heart because it increases the friction of the blood-current and dimin ishes the elasticity of the artery. Con versely hypertrophy tends to produce atheroma by maintaining a high arterial pressure; so that the two conditions are apt to co-exist. Other things which in crease the labors of the left ventricle and enlarge it are arteriosclerosis, acute and chronic nephritis , and, to a certain extent, pregnancy.
Enlargement of the heart in Bright's disease as a useful, compensatory process. It is well known that the cells of the con voluted tubules remove excrementitious matter from the blood. Since a great number of these cells are destroyed by the connective-tissue proliferation, an increased amount of work falls upon the remaining ones, which require a large amount of fluid to prevent an accumula tion of the toxic products within them. Thus follows polyuria, and this again necessitates cardiac hypertrophy. Al though the process so far is salutary, it is obvious that the greater strain to which the arterial system is exposed will eventually lead to endarteritis, while finally there must come a time when either the overworked heart or blood vessels will no longer bear the pressure, and degenerative process will occur. A. Bier (Mfinchener med. Woch., Apr. 17, 1900).
2. A second class of the causes of hypertrophy includes those conditions which obstruct the lesser or pulmonary circulation, viz.: tumors, excessive pleu ral effusion, emphysema, chronic inter stitial pneumonia, and some cases of phthisis. Orth states that some cases of chronic bronchitis exhibit a degree of hypertrophy of the right ventricle not accounted for by the amount of emphy sema present. 3. Valvular lesions are sure to cause hypertrophy unless the pa tient is too feeble, or unless he is over whelmed by the shock of their sudden development, as, for example, when a cusp of the aortic valves is torn off by violent exertion. More will be said about the valves under PATHOLOGY. Chronic adhesive pericarditis causes hypertrophy, particularly when, besides the oblitera tion of the pericardial space, there is adhesion of the outer surface of the peri cardium to the pleura. Interstitial myo carditis is another cause. 4. Long-con tinued and severe muscular exertion— as exemplified in blacksmiths, iron molders, coal-miners, and longshoremen —may endanger the heart; also pro longed or habitual mental excitement or worry, to some extent. 5. Somewhat allied to the preceding causes are exoph thalmic goitre and excess in tea, coffee, tobacco, alcohol, and venery. Sometimes more than one cause operate in a single person. Laborious occupations affect much more severely the free drinkers than the total abstainers. Brewery workmen illustrate this; although it may be that the effect of beer is due not merely to the alcohol it contains, but also to the large amount of liquid and to the carbohydrates dissolved in it, which would, in an excessive drinker, tend to keep the arteries at rather high tension.