If a diastolic murmur is distinctly audible in the carotid arteries, it is invariably preceded by a loud systolic murmur in them, the systolic portion of the murmur not being very plainly audible in the aortic nor in any part of the cardiac area: this indicates very considerable incompetence with comparatively trifling obstruction.
DIFFERENTIAL DIAGNOSIS.—The diagnosis of aortic regurgitation is generally not difficult, as it rests almost exclusively upon the existence or nonexistence of a diastolic murmur. It may, however, be mistaken for aortic stenosis, for mitral obstruction, for pericarditis localized over the aorta, for aneurism of the aorta, for aneurism of the aorta immediately above the valves, patency of the ductus arteriosus, for insufficiency of the pulmonic semi-lunar valves, and, occasionally, for a rough and inelastic condition of the ascending aorta.
1st. Mitral obstruction gives a presystolic murmur, while aortic reflux produces a diastolic murmur. Mitral stenosis is accompanied by no hypertrophy or dilatation of the left ventricle, whereas these conditions are always present with aortic reflux. The quality of a presystolic mitral murmur is harsh and rough, and it has a churning, blubbering, or grinding character, while aortic reflux has a murmur of low pitch and of a soft, blowing, or musical character. Mitral stenosis is accompanied by a purring thrill which is absent in aortic regurgitation. The murmur of mitral stenosis is the longest of all the cardiac murmurs. The murmur of mitral stenosis is never heard behind, whereas that of aortic regurgitation is often heard at the sides of the chest and along the spinal column. Finally, mitral stenosis is attended by well-marked pulmonary symptoms during active physical exertion, which are rarely present in aortic insufficiency.
2d. A pericardial friction sound over the aorta has its maximum intensity over the seat of its production, and is usually audible during both the cardiac systole and diastole. In aortic regurgitation the character of the pulse, the existence of hypertrophy and dilatation of the left ventricle, and the carotid pulsation will establish the diagnosis.
3d. An aneurism at the sinuses of Valsalva is diagnosticated by the history of the case, the presence of the murmur over the pulmonary artery, the evidences of arterial degeneration, the absence of left ventricular dilatation and hypertrophy, and the peculiar jerking pulse. An aneurismal murmur is circumscribed, has a booming quality, and is usually systolic in rhythm and never transmitted to the apex of the heart.
4th. Patency of the ductus arteriosus is a rare condition: in a case where this was diagnosticated15 the murmur was audible at the left of the sternum, was not everywhere continuous with the second sound, was only transmitted very feebly to the left, and had a wavy character, sufficient of itself to distinguish it from an aortic regurgitant murmur.
15 Guy's Hosp. Rep., Ser. 3, vol. xviii., 1872–73.
5th. Insufficiency of the pulmonic semi-lunar valves is the rarest of all valvular lesions: the murmur should be diastolic, having its maximum intensity in the second intercostal space of the left side; it should be transmitted only downward and toward the right apex; and should not be attended by arterial pulsation, a jerking pulse, or by left ventricular hypertrophy and dilatation.
6th. A diastolic murmur in the ascending arch, due to roughening, rigidity, and dilatation of the artery, is also rare, while the condition which some say can produce it is very common.
Two cases are recorded in which the diagnosis rested upon the character of the pulse, throbbing of the arteries, and the absence of hypertrophy and dilatation of the left ventricle.16