Prevention of pacing-induced silent myocardial ischaemia by nifedipine in coronary heart disease.

In 11 patients with angiographically documented significant coronary heart disease silent (asymptomatic) segmental myocardial ischaemia was induced by rapid atrial pacing using the sub-threshold rate (10 impulses min-1 less than angina-threshold rate). The effect of pacing-induced silent myocardial ischaemia on the left ventricular contraction was studied from three consecutive quantitative cineventriculographies--performed in control conditions (I) and during sub-threshold pacing before (II) and after (III) 20 mg nifedipine sublingually. On this basis, left ventricular mean relative hemiaxis shortening (X delta r%) for anterior, inferior and apical segments as well as ventricular volumes and ejection fraction using an area-length method were determined for every patient. Sub-threshold atrial pacing significantly (P less than 0.0005) reduced X delta r% of non-infarcted post-stenotic myocardial segments (36 +/- 10%----23 +/- 10%; N = 14) having no significant effect on the contraction of normal and infarcted segments. As a consequence, left ventricular ejection fraction (72 +/- 10%----64 +/- 14%; P less than 0.005) and end-systolic volume (33 +/- 16 ml----43 +/- 20 ml; P less than 0.005) deteriorated too. After 20 mg nifedipine sublingually in post-stenotic non-infarcted segments characterized by pacing-induced silent ischaemia, normalization of X delta r% (23 +/- 10%----42 +/- 11%; P less than 0.0005) was observed together with significant improvement of ejection fraction (64 +/- 14%----75 +/- 10%; P less than 0.005) and with reduction of the aortic end-diastolic pressure (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)