Hypertensive left ventricular hypertrophy: relation to peripheral sympathetic drive

OBJECTIVES This study was designed to examine whether the occurrence of left ventricular hypertrophy (LVH) in moderate to severe essential hypertension (EHT) was associated with alteration in peripheral sympathetic drive. BACKGROUND In hypertension, LVH is an independent predictor of increased morbidity and mortality. The reported mechanisms leading to LVH remain unclear but include hemodynamic and humoral factors. The sympathetic nervous system may be important, particularly as catecholamines have been shown to have trophic properties. We tested the hypothesis that sympathetic activity measured using microneurography could be different in patients with hypertension depending on the presence of LVH. METHODS We examined 28 subjects with moderate to severe EHT (stages 2 to 3; Joint National Committee [JNC]-VI classification). Fourteen had echocardiographic evidence of LVH (EHT + LVH), while the other 14 subjects (EHT) did not. Subjects were matched in terms of age, body mass index and levels of arterial blood pressure. Peripheral muscle sympathetic nerve activity was measured from both multiunit bursts (MSNA) and single unit (s-MSNA) vasoconstrictor impulses via the peroneal nerve. RESULTS The mean frequency of s-MSNA and MSNA was greater in the EHT + LVH group than it was in the EHT group (mean ± SEM; 75.9 ± 6.9 impulses/100 beats vs. 52.1 ± 2.9 impulses/100 beats, p < 0.001 and 64.2 ± 5.7 bursts/100 beats vs. 48.9 ± 2.8 bursts/100 beats, p < 0.05). CONCLUSIONS These results indicate that, in subjects with moderate to severe hypertension, the presence of LVH is associated with higher sympathetic discharge, evidenced by an increase in unitary firing frequency and also by fiber recruitment.