Non-invasive electrophysiological evaluation of calcium antagonist long-term therapy

The evaluated effects of oral administration of verapamil, diltiazem, and nifedipine in patients with first degree A-V block by using a new noninvasive technique: signal averaged ECG. The study group consists of 5 females and 3 males ranging from 52 to 70 years old. All patients showed a first degree A-V block at surface ECG and an abnormal A-V time (suprahisian lengthening) during signal averaged ECG (SAECG). Verapamil 240 mg/daily, diltiazem 180 mg/day and nifedipine 30 mg/day were given separately for a week followed by a wash out period of 5 days before giving next drugs. An ECG and SAECG were performed before and after every administration. PR, A-H and H-V interval were evaluated in every recording. Verapamil and diltiazem induced a significant lengthening of A-V conduction (PR increase was 15.4% and 15.1%, respectively). No significant modification appeared after nifedipine. Our data, using a noninvasive technique, agreed with values of previous invasive evaluations. We suggest precaution in using verapamil and diltiazem in patients with BAV 1 degree and advise a selective use of calcium antagonist therapy.