Myocardial ischaemia and spinal analgesia in patients with angina pectoris

We have studied prospectively myocardial ischaemic events by Holter monitoring of ST-segment depression in patients with angina pectoris given spinal analgesia for minor surgery compared with a reference day of normal daily activities. Monitoring was undertaken continuously for 24 h on both days, starting just before anaesthesia on the day of surgery. On the reference day, seven of 14 patients had 27 ischaemic events with mean max ST-depression of 0.15 mV and total duration of 143 min, compared with 10 of 14 patients with 70 ischaemic events with mean max ST-depression of 0.22 mV and total duration of 1078 min (P < 0.01 for all). On the day of surgery, the first ischaemic event occurred a mean 338 min (range 75-480 min) after spinal analgesia, and the duration of all first events was 480 min. On this day, the first ischaemic event was associated with increased heart rate (103 beat min-1 (range 66-131 beat min-1) compared with 92 (60-122) beat min-1 during all events (P = 0.011)). In patients with angina pectoris, myocardial ischaemia did not occur immediately after the onset of spinal analgesia, but several hours later, corresponding to the cessation of block. This could be explained by increased cardiac pre- and afterload, probably further aggravated by the volume load.