Aortic valve closure: Echocardiographic, phonocardiographic, and hemodynamic assessment

The temporal relationship between the closure of the aortic valve (AoV) and the onset of the aortic component of the second heart sound (A₂) was defined by simultaneous recording of AoV echogram, phonocardiogram (PCG), and electrocardiogram in 25 subjects. Ten subjects had no heart disease (normal); 15 suffered from various cardiac conditions other than AoV disease (patients). The point of coaptation (C) of the AoV cusps to the onset of A₂, the C-A₂ interval, was measured to the nearest 5 msec. in 125 cycles. Fifty-eight cycles had a C-A₂ of 10 msec., and 47 cycles had a C-A₂ of 15 msec. The remainder were distributed at intervals below 10 or above 15 msec. The average C-A₂ interval was 11.48±0.38 msec. (mean±1 S.D.). A similar distribution pattern was observed when the total number of cycles was divided into "normal" and "patient" groups. In 3 subjects, simultaneous equisensitive (catheter-tip micromanometer) left ventricular and central aortic pressures, PCG, and AoV echograms were recorded. C-A₂ ranged from 0 to 10 msec.; the interval between left ventricular and aortic pressure at the level of the incisura-hangout interval-ranged from 8 to 20 msec. Inhalation of amyl nitrite in one subject produced a significant fall in arterial pressure, accompanied by prolongation of the hangout interval from 10 to 20 msec. and of the C-A₂ interval from 0 to 8 msec. Thus, the C-A₂ interval is an integral part of the hangout time. Data suggest that A₂ does not originate from the coaptation of the aortic valve cusps per se, but is related to events that occur at the time of or slightly after coaptation.