Differential Effects of Statins (Pravastatin or Simvastatin) on Ventricular Ectopic Complexes: Gα_i2, a Possible Molecular Marker for Ventricular Irritability

Retrospective studies suggest that statins might exert an antiarrhythmic effect on the heart. The mechanism of this effect is unclear. Parasympathetic stimulation of the heart has been shown to protect against ventricular arrhythmias. The goal of this study was to determine the effect of statins on ventricular arrhythmias and its correlation with changes in parasympathetic responsiveness and Gα_i2 expression. Patients were randomized to pravastatin and simvastatin in a double-blind crossover design. Ventricular arrhythmias were determined by analysis of 24-hour Holter recordings. Spectral RR interval analysis of Holter studies determined peak high-frequency power fraction, which reflects parasympathetic modulation of heart rate. Expression of Gα_i2, a molecular component of the parasympathetic response pathway, was determined by Western blots of patients' lymphocytes. Pravastatin treatment decreased the incidence of ventricular premature complexes by 22.5 ± 3.4% (n = 20, p <0.05), couplets, and runs of 3 to 6 beats of nonsustained ventricular tachycardia from 9.8 ± 2.67 to 3.9 ± 1.25 events/patient/24 hours (n = 12, p <0.05). Pravastatin increased peak high-frequency fraction by 29.8 ± 4.3% (n = 33, p <0.001), while Gα_i2 expression increased by 51.3 ± 22.5% (n = 21, p <0.05). Effects of simvastatin on ventricular premature complexes and nonsustained ventricular tachycardia were not significant. Relative changes in couplets and nonsustained ventricular tachycardia in pravastatin-treated patients correlated negatively with changes in Gα_i2 and high-frequency fraction (ρ = −0.588 and ρ = −0.763, respectively, n = 12, p <0.05). In conclusion, these data suggest that pravastatin might decrease cardiac irritability via an increase in parasympathetic responsiveness and that changes in Gα_i2 expression might serve as a molecular marker for this effect, which might play a role in the molecular mechanism of the antiarrhythmic effect of statins.