The effect of near-maximal isometric stress on the presence and amplitude of fourth heart sounds.

Near-maximal isometric exercise (IHG) was employed to provoke new, or alter pre-existing fourth heart sounds (S4s) in ambulatory middle-aged normal subjects (N), hypertensive patients (HHD), and patients with coronary disease (CAD). S4 amplitudes and systolic time intervals (STIs) were measured blindly. No subjects without a resting S4 developed a new S4 during IHG. Increases and decreases of pre-existing S4 provoked by IHG were not statistically different among all groups. Among subjects matched for presence of S4, STIs during IHG showed significant shortening of the ejection time index and prolongation of Q-Im in the HHD group only. When the subjects who increased a resting S4 during IHG were compared with the subjects who decreased their resting S4 during IHG there were no significant differences in the responses of STIs. Thus, in these ambulatory, hypertensive patients, coronary patients, and normal subjects, near-maximal IHG did not induce new S4s and had variable effects on pre-existing S4s. Neither type of S4-response could be associated with corresponding changes in systolic time intervals.