Adrenergic receptor antagonist prevents the left ventricle with chronic pressure-overload from electrical remodeling

Experiments were performed to investigate the effects of long-term treatment with adrenergic receptor antagonist on electrical remodeling of the left ventricle with chronic pressure-overload. New Zealand rabbits underwent subtotal banding of superrenal abdominal aorta. At 10 weeks after surgery, echocardiography examination was performed, then action potential (AP), inward rectifier potassium current (I(Ki)), delayed rectifier potassium current (I(K)) and Na(+)/Ca(2+) exchanger current (I(Na(+)/Ca(2+))) were recorded in midmyocardial cells isolated from left ventricle of abdominal aorta banded group (banded group), abdominal aorta banding plus Carvedilol intervention group (Carvedilol group), and normal control group rabbits by using the whole-cell patch-clamp techniques. The results showed that left ventricular mass index in control, banded, and Carvedilol groups were 1.78+/-0.06 (n=7), 2.33+/-0.11 (n=7), and 1.87+/-0.08 (n=7), respectively (banded vs control and Carvedilol, P<0.01). At basic cycle length of 2 s, AP duration (measured at 90% repolarization, APD(90), ms) in control, banded, and Carvedilol groups were 522.0+/-19.5 (n=6), 664.7+/-46.2 (n=7), 567.8+/-14.3 (n=8) respectively (banded vs control, P<0.01; Carvedilol vs banded, P<0.05). At test potential of -100 mV, inward I(Ki) density (pA/pF) in control, banded, and Carvedilol groups were -11.8+/-0.50 (n=8), -8.07+/-0.28 (n=8), -10.69+/-0.35 (n=8) respectively (banded vs control and Carvedilol, P<0.01). At test potential of +50 mV, I(K) tail current density (pA/pF) in control, banded, and Carvedilol groups were 0.59+/-0.04 (n=8), 0.40+/-0.02 (n=9), 0.51+/-0.02 (n=8) respectively (banded vs control, P<0.01; Carvedilol vs banded, P<0.05). At test potential of +60 mV, outward I(Na(+)/Ca(2+)) density (pA/pF) in control, banded, and Carvedilol groups were 1.06+/-0.11 (n=8), 1.54+/-0.10 (n=9), 1.24+/-0.07 (n=8), respectively (banded vs control and Carvedilol, P<0.01). At test potential of -120 mV, inward I(Na(+)/Ca(2+)) density (pA/pF) in control, banded, and Carvedilol groups were -0.54+/-0.06 (n =8), -0.75+/-0.04 (n=9), -0.60+/-0.03 (n=8), respectively (banded vs control, P<0.01; Carvedilol vs banded, P<0.05). It is shown that long-term treatment with Carvedilol not only prevents development of cardiac hypertrophy, but also improves the electrophysiological alterations in rabbit hearts with chronic pressure-overload. This finding may add new electrophysiological evidence for the treatment of heart failure and hypertension with adrenergic receptor antagonist.