Reduced anisotropy of action potential conduction in left ventricular hypertrophy.

INTRODUCTION: The aim of this study was to determine if anisotropic action potential conduction was altered during development of left ventricular hypertrophy (LVH). METHODS AND RESULTS: Isolated guinea pig left ventricular preparations from hearts that had developed LVH were used to measure conduction velocity in longitudinal and transverse orientations to the fiber direction. A variable degree of LVH was induced by placing a ring around the ascending aorta for 50 to 250 days. Results were compared with an age-matched control group that underwent a similar operation but with no ring placement. LVH was measured as the heart-to-body-weight ratio (HBR), which correlated with an increase of mean myocyte cross-sectional area. Longitudinal conduction velocity (LCV) declined progressively as HBR increased (mean +/- SD: sham vs LVH: HBR 3.74 +/- 0.30 g/kg vs 4.53 +/- 0.52 g/kg; LCV 72.8 +/- 15.5 vs 63.6 +/- 11.1 cm/sec). Mean transverse conduction velocity (TCV) was greater in LVH compared with control (20.5 +/- 4.7 cm/sec vs 25.4 +/- 8.1 cm/sec), but there was no significance in the trend as a function of HBR. The anisotropic ratio (LCV/TCV) significantly declined as HBR increased. The time constant of the foot of the action potential was smaller in the transverse compared with the longitudinal dimension. There was no influence of hypertrophy. CONCLUSION: The decrease of LCV and reduction of the anisotropic conduction ratio suggest remodeling of the tissue in LVH. The consequences for the generation of arrhythmias are discussed.

Effect of indapamide on left ventricular hypertrophy in hypertension: a meta-analysis.

Left ventricular hypertrophy is a major risk factor for cardiovascular morbidity and mortality. Angiotensin-converting enzyme inhibitors, calcium antagonists, and beta-blockers prevent, and cause regression of, left ventricular hypertrophy after short-term therapy. The ability of diuretics to do the same is unclear. We have performed a meta-analysis of studies documenting the effect on left ventricular mass of 6 months' treatment with 2.5 mg indapamide daily. Six studies comprising 197 patients, aged 20-75 years, were included. There was an overall mean reduction in left ventricular mass index of 13.3%, which was principally due to a reduction in left ventricular wall thickness rather than internal diameter.