[Pathophysiology of asymmetric septal hypertrophy with special reference to the response to isoproterenol...

To investigate the pathophysiological significance of asymmetric septal hypertrophy (ASH), echocardiograms were recorded in 25 patients with hypertension (HT) (12 with ASH, 13 with symmetric hypertrophy (SH), 19 patients with hypertrophic non-obstructive cardiomyopathy (HNCM) (eight with ASH, 11 with SH), and 12 patients with hypertrophic obstructive cardiomyopathy (10 with ASH and two with SH). In eight patients with ASH, 12 patients with SH and eight normal controls, echocardiograms were also recorded during intravenous infusion of 0.02 mu/kg/min of isoproterenol. There were no significant differences in end-diastolic dimension (EDD), end-systolic dimension (ESD), percent fractional shortening (%FS), interventricular septal excursion (IVSE) and posterior wall excursion (PWE) between patients with ASH and patients with SH. Among patients with ASH, interventricular septal thickness (IVST) and its ratio to posterior wall thickness (IVST/PWT) were significantly larger in HOCM than in others. Before isoproterenol infusion, there was no significant difference in the normalized peak rate of change of left ventricular dimension during systole (pVs) between ASH and SH, and between ASH and NC. However, 5 min after isoproterenol infusion, pVs was significantly greater in ASH (7.0 +/- 2.4/sec) than in SH (4.9 +/- 1.3/sec) and in NC (4.5 +/- 1.1/sec) (p less than 0.05 and p less than 0.05, respectively). This study suggests that ASH is related to hyperfunction of the catecholamine-beta receptor system.