The apical A wave versus the fourth heart sound in assessing the severity of aortic stenosis

The height of the "a" wave of the apexcardiogram was evaluated as a marker for critical aortic stenosis in patients over 40. Critical aoritc stenosis was defined as an aortic valve area less than .75 cm-2 with no more than mild aortic insufficiency. Phonocardiograms and apexcardiograms were performed on 72 patients with catheterization proven aortic stenosis and on 14 normal controls, all over age 40. The height of the "a" wave of the apexcardiogram was measured as a percentage of the e to o excursion (a/e-o). Fourth heart sound gallops ( S4G) were recorded in 71% (11 of 14) of normal controls, 86% (6 of 7) of patients with less than critical aortic stenosis, and 85% ( 55 of 65) of patients with critical aortic stenosis. The a/e-o was less than 16% in all normals or patients with less than critical aortic stenosis. The a/e-o exceeded 16% in 45% (29 of 65) with critical aortic stenosis. Audibility of the S4G bore no relationship to recordability, apical "a" wave geight, or the severity of the aortic stenosis. In conclusion, therefore, we believe that when one is confronted with findings suggestive of aortic stenosis, the finding of a palpable apical "a" wave (or an "a" wave height of greater than 16% of the total complex on the apexcardiogram) is an important positive feature, suggesting severe aortic stenosis. Its absence, however, does not exclude severe valvar obstruction. Probably because of auscultatory inaccuracy in this condition, the apparent presence or absence of an S4G has not been of much aid in this evaluation. This sound, however, might be more useful in a carefully performed prospective study.