Internally recorded systolic time intervals in hypertrophic subaortic stenosis

The cardiac catheterization records of 20 patients with documented hypertrophic subaortic stenosis were analyzed to evaluate the utility of systolic time intervals in quantitating left ventricular outflow tract obstruction in this disease. The preejection period, ejection time and instantaneous peak outflow pressure gradient were measured from simultaneous recordings of the electrocardiogram and left ventricular and central aortic pressure signals, and the preejection period/ejection time (PEP/ET) ratio was computed. Most patients had a significant spontaneous or induced (with isoproterenol or postextrasystolic potentiation) variation in peak outflow gradient (range 0 to 186, average 85 mm Hg) with a high linear correlation between the peak outflow gradient and the systolic time intervals. For the group, peak outflow gradient correlated best with PEP/ET ratio (r = ?0.82, no. = 183) and less well with preejection period (r = ?0.62), ejection time (r = 0.56) or their rate-corrected values (r = ?0.71 and r = 0.60, respectively). The PEP/ET ratio for beats recorded at the time of cardiac output measurement correlated with instantaneous mean outflow pressure gradient (r = ?0.88, no. = 28, P < 0.001) and calculated left ventricular outflow orifice size (r = 0.72, no. = 28, P < 0.001), each of which correlated less well with preejection period, ejection time or their rate-corrected values. These findings indicate that the systolic time intervals are importantly affected by the degree of outflow obstruction as best exemplified in the relation between the PEP/ET ratio and mean outflow pressure gradient. In view of the previously documented close correspondence between internally and externally recorded systolic time intervals, the latter may be useful in the noninvasive assessment of outflow obstruction in this disease.