Objective: To study the prevalence and circadian distribution of ischaemic ST-segment depression detected with ambulatory electrocardiographic monitoring (AECG) in patients with intermittent claudication (IC) as well as to study ambulatory blood pressure (ABP) and the relation of ischaemic episodes to variations in ABP and heart rate.
Design: A total of 40 patients with a history of IC and an ankle/brachial-index (ABI) <0.9 performed: (i) 24-h AECG recordings, (ii) simultaneous 24 h recordings of ABP every 15 min (Spacelabs 90207), (iii) an exercise treadmill test (ETT). An ischaemic episode was defined as a transient ischaemic ST-segment deviation > or =1 mm lasting >1 min. Eleven patients were excluded from ECG analysis because of uninterpretable ECG caused by treatment with digoxin or technical problems.
Results: Out of 29 patients, eight experienced a total of 15 episodes of ST-depression on AECG. The mean duration was 21+/-31 min. The majority of episodes (11 of 15) occurred between 6 and 12 a.m. In eight patients with ST-segment depression three had a history of ischaemic heart disease (IHD), four were hypertensives and four had signs of myocardial ischaemia on ETT. There were no significant differences between patients with and without ST-segment depression in ABP, walking performance or ABI. During ST-depression episodes systolic and diastolic blood pressure and heart rate were higher than day mean values; 178+/-41 vs. 166+/-30 mmHg (P= 0.09); 96+/-9 vs. 90+/-4 mmHg (P = 0.01) and 103+/-9 vs. 87+/-5 beats min(-1) (P < 0.01).
Conclusion: Silent myocardial ischemia occurred in about a third of patients with IC. Episodes of ischaemia were associated with an increased ABP and heart rate. Whether treatment of high blood pressure may reduce silent ischaemia and if this favourably influences outcome is a matter of further research.