Comparative electrophysiological effects of captopril or hydralazine combined with nitrate in patients with left ventricular dysfunction and inducible ventricular tachycardia.

OBJECTIVE

To assess the electrophysiological and antiarrhythmic effects of pharmacological load manipulation by an angiotensin converting enzyme (ACE) inhibitor (captopril) and a direct vasodilator (hydralazine plus isosorbide mononitrate) in patients with inducible ventricular tachycardia and impaired left ventricular function.

DESIGN

Randomised open label cross-over comparison of three regimens.

SETTING

Tertiary arrhythmia referral centre.

SUBJECTS

Eight patients with reduced left ventricular function and sustained ventricular tachycardia inducible by programmed stimulation.

INTERVENTIONS

Three treatment regimens each of 48 hours duration: captopril, hydralazine plus isosorbide mononitrate, and control (no vasodilator).

MAIN OUTCOME MEASURES

Changes in central haemodynamics, electrophysiological parameters, and induction of ventricular tachycardia during treatment with captopril, or hydralazine combined with nitrate, compared with a control period.

RESULTS

Both vasodilator treatments produced similar balanced reductions in peak systolic pressures and filling pressures compared with controls. Captopril had no effect on sinus cycle length, atrial refractoriness, or intraventricular conduction, but prolonged ventricular effective and functional refractory periods and QT interval during constant rate atrial pacing. Hydralazine combined with nitrate did not significantly alter any electrophysiological variable. Ventricular tachycardia was similarly inducible during all three periods.

CONCLUSIONS

Load manipulation by captopril but not hydralazine combined with nitrate prolonged ventricular refractoriness and repolarisation, possibly reflecting a combination of mechano-electrical effect with the restraining influence of ACE inhibitors on reflex sympathetic stimulation.