49 Archives générales, 1859.
50 McDonald, Heart Disease during Pregnancy, London, 1878.
51 Virchow's Archiv, lxxvii.
(9) Hypertrophy of the right heart in disease of the lungs or of the valves is usually followed by more or less hypertrophy of the left ventricle as well, caused by the increased work in consequence of retarded outflow into the venous system.
Right Ventricle.—Hypertrophy of this chamber is most frequently met with in connection with disease of the left side of the heart; next with various chronic affections of the lungs; and lastly with valvular affections of the right side.
(1) Mitral lesions—incompetence or stenosis—are very common causes which act by increasing the resistance in the pulmonary veins and obstructing the free flow of blood in capillaries of the lung. To compensate for this defect the walls of the right ventricle increase in size, and the hypertrophy at first may be unattended with dilatation.
(2) Pulmonary Lesions.—The obliteration of any considerable number of blood-vessels within the lungs by emphysema, cirrhosis, or phthisis (sometimes), occasionally the compression of pleuritic exudation, increases the blood-pressure in the pulmonary artery and rapidly leads to hypertrophy of the right heart. Narrowing of the main branches of the pulmonary artery by the growth of tumors or an aneurism of the aorta occasionally produces the same effect.
(3) Valvular lesions on the right side are rare causes of hypertrophy in the adult, but during foetal life, when endocarditis is more prevalent in the pulmonary and tricuspid valve, stenosis or insufficiency at these orifices leads to great enlargement of the ventricle. Pulmonary stenosis is the most common lesion; incompetence is not often met with. Lesions of the tricuspid valves in the adult are almost always associated with mitral disease. When the dilated hypertrophy of the right ventricle reaches a certain grade in cases of mitral disease or pulmonary lesion, tricuspid incompetence develops.
(4) Among other causes which may be mentioned are pericardial adhesions, which some think tend specially to the production of right-sided hypertrophy and extensive pleuritic adhesions. Atheroma of the pulmonary arteries is more often a consequence than a cause of hypertrophy.
The auricles are usually dilated and hypertrophied; simple hypertrophy is probably never seen. In the left auricle this condition develops in lesions at the mitral orifice, particularly stenosis when it compensates for the obstruction. In free mitral regurgitation the hypertrophy is not so marked.