Direct evidence of impaired cardiac sympathetic innervation in essential hypertensive patients with left ventricular hypertrophy

Increased sympathetic nervous activity has been proposed as one of the causes of left ventricular hypertrophy (LVH) associated with hypertension. However, the precise relationship is not fully understood. Methods: To elucidate the relationship between myocardial sympathetic nervous activity and LVH in patients with essential hypertension (EHT), we performed I-123-metaiodobenzylguanidine (MIBG) myocardial scintigraphy in 49 patients with EHT and 17 normotensive control subjects. Sympathetic innervation of the left ventricle was evaluated using SPECT, and the whole heart uptake of the tracer was quantitatively assessed as the heart-to-mediastinum uptake ratio on both the early (15-min) and delayed (5-hr) images. Myocardial washout rate (MWR) of the tracer from 15 min to 5 hr after the isotope administration was also calculated. The left ventricular mass index (LVMI) was determined echocardiographically. Results: In 49 hypertensive patients, there was a negative correlation between LVMI and heart-to-mediastinum uptake ratio on both the early and delayed images (r = -0.55, p < 0.0001; r = -0.63, p < 0.0001, respectively). In addition, there was a positive correlation between the LVMI and MWR of I-123-MIBG in these hypertensive patients (r = 0.59, p < 0.0001), As for the regional uptake of the tracer, there was no significant difference between control subjects and hypertensive patients without cardiac hypertrophy, but a significant decrease of the uptake in the inferior and lateral regions was observed in hypertensive patients with cardiac hypertrophy, Conclusion: Patients with EHT had decreased accumulation and increased MWR of I-123-MIBG in proportion to the degree of LVH. Hypertensive patients with cardiac hypertrophy had impaired sympathetic innervation in the inferior and lateral regions of the left ventricle.