DIFFERENTIAL AUTONOMIC MECHANISMS UNDERLYING EARLY-MORNING AND DAYTIME TRANSIENT MYOCARDIAL-ISCHEMIA IN PATIENTS WITH STABLE CORONARY-ARTERY DISEASE

Objectives-To see whether autonomic regulatory mechanisms play a part in transient myocardial ischaemia in patients treated with beta blockers. Design-Prospective study. Setting-Outpatients' clinic. Patients-51 consecutive patients with angiographically documented coronary artery disease, stable angina, and transient myocardial ischaemia despite beta blockade. Interventions-24 hour ambulatory electrocardiographic monitoring for analysis of variability in ST depression and heart rate. Main outcome measures-Numbers of episodes of ischaemia, with an ST depression of greater than or equal to 0.1 mV 80 ms after the J point that lasted greater than or equal to 60 s at an interval of greater than or equal to 60 s from a previous ischaemic episode. Heart rate at onset of ischaemia. Normalised spectral analysis of heart rate variability; ratio of low to high frequency power to assess the sympathovagal balance. Results-Despite treatment, 258 episodes of transient ischaemia were recorded. At heart rates at onset of ischaemia of