It should be mentioned here that the old idea, that "mitral stenosis sometimes produces hypertrophy of the left ventricle," is fallacious. In no instance can it be attributable to mitral stenosis.
Physical Signs.—Inspection.—As the left ventricle does not receive its normal quantity of blood, the cardiac impulse is feeble. Sometimes it has a visible undulating movement.
Palpation.—On palpation, although the apex-beat is less forcible than normal, a distinct purring thrill will be communicated to the hand: this thrill is a constant attendant of mitral stenosis, and may be regarded as its diagnostic sign. It should be remembered, however, that a purring thrill does not always indicate mitral stenosis. It is most distinct at the apex-beat, although it may be diffused over the whole præcordial space. It either continues through the entire diastole or is only present just before the systole. It is sometimes called a presystolic thrill. It ceases with the apex-beat. The only conditions besides mitral stenosis which will cause a purring thrill at the cardiac apex are mitral regurgitation, with extensive dilatation of the left ventricle, and left ventricular aneurism; in both instances the thrill will not be presystolic, but systolic.
Percussion.—The increased size of the left auricle may cause an increase in the area of cardiac dulness upward and to the left at the inner part of the second left interspace. This increased area of dulness will only be recognized on careful percussion during expiration.
Auscultation.—Mitral stenosis is characterized by a loud churning, grinding, or blubbering presystolic murmur; this murmur is of longer duration than any other cardiac murmur, on account of the time required for the blood to pass through the narrowed and obstructed orifice. It ends with the commencement of the first sound and the apex-beat, being synchronous with the purring thrill. The murmur is heard with its maximum intensity a little above the apex-beat.
Cryan records a case where the murmur was absent, but the diagnosis of mitral stenosis was made from the other symptoms. At the autopsy the orifice would barely admit the tip of the little finger, and the absence of the murmur was accounted for by the smallness of the aperture.19
19 Trans. Path. Society, Dublin, Part 2, vol. iv., 1870.
As a rule, mitral stenosis is accompanied by the loudest as well as the longest cardiac murmur. The murmur is always louder when the patient is erect than when in the recumbent posture. For a few days before death, and at any time when there is great constitutional debility, the murmur may be held in abeyance. A presystolic murmur is never present when auriculo-ventricular narrowing does not exist. When this lesion does exist it is never permanently, and very seldom temporarily, absent. A prolonged murmur and a sharp first sound indicate a funnel-shaped stenosis. A murmur immediately following the second sound, and running through the apex-beat, indicates great contraction of the orifice—diaphragmatic contraction. The murmur of mitral stenosis is very rarely, if ever, conveyed to the left of the apex-beat, and it is rarely heard more than two inches to the right of the apex. The second sound of the heart is intensified over the pulmonary valves. When mitral reflux and mitral obstruction coexist, the two murmurs run into each other, constituting a single murmur that may be mistaken for a systolic murmur. The harsh character of the presystolic element of the murmur can always be recognized.
A mitral obstructive murmur is never soft or musical, but there is a rare form of presystolic mitral which is so short as to resemble a tone. A mitral stenotic murmur does not often merge into the first sound of the heart, but is usually separated from it by a short interval. Sometimes a stenotic murmur only becomes audible when the patient sits up. In about one-third of all cases of stenosis of the mitral orifice the second sound is reduplicated. It is best heard at the apex and when the heart's action is slow. The reduplication may be temporarily absent. Pulmonary congestion efficiently accounts for this reduplication. Geigel ascribes it to "non-coincidence in the closure of the valves." Guttman regards it as originating at the stenotic orifice itself. Balfour thinks that thrill and reduplication of the second sound are sufficient to make a diagnosis in the absence of murmur. Some regard the length of the pause between the murmur and the first sound as a measure of the stenosis—the shorter the pause, the greater the stenosis.
DIFFERENTIAL DIAGNOSIS.—The diagnosis of mitral stenosis is not difficult; it mainly depends upon the existence of two physical signs—the purring thrill and a loud, long, blubbering presystolic murmur.