MYOCARDIAL-ISCHEMIA AND ANGINA IN THE EARLY POSTINFARCTION PERIOD - ACOMPARISON WITH PATIENTS WITH STABLE CORONARY-ARTERY DISEASE

Objective-To evaluate Holter and treadmill responses in patients with stable angina or recent myocardial infarction in order to compare the mechanisms of ischaemia and its symptomatic expression in these two gr oups. Patients-75 patients with ischaemic ST segment depression on bot h a treadmill stress test and ambulatory Holter monitoring. Group A co mprised 35 patients with stable angina, and group B comprised 40 patie nts in the early period after infarction. Setting-The coronary care un it and cardiology department of a district general hospital. Design-A prospective, between group, comparative study. Results-Treadmill test showed demand driven ischaemia in both groups. Although ST depression occurred at comparable rate-pressure products and workloads, it was as sociated with angina in 80% of group A compared with only 40% of group B (p < 0.005). During Holter monitoring, ST depression was associated with an attenuated increase in rate in group A and almost no increase in rate in group B (18.2% v 3.7%; p < 0.005), suggesting that reducti ons in myocardial oxygen delivery were contributing to the ischaemic e pisodes, particularly in group B. Ischaemic episodes were more commonl y silent during Holter monitoring, particularly patients in group B, o nly two of whom experienced angina in association with ST depression. Spectral and non-spectral measures of heart rate variability were sign ificantly reduced in group B compared with group A. Patients with sile nt exertional ischaemia in group A had significantly less heart rate v ariability than patients who experienced angina but this difference wa s not seen in group B. Conclusion-In stable angina, myocardial ischaem ia is usually painful and demand driven, whereas in the early period a fter infarction silent, supply driven ischaemia predominates. The fail ure of myocardial ischaemia to provoke symptoms in some patients with stable angina may be related to autonomic dysfunction affecting the se nsory supply to the heart. In the early period after infarction despit e clear evidence of autonomic dysfunction, other mechanisms must also be important as there was no tendency for the reduction in heart rate variability to be exaggerated in the subgroup with silent exertional i schaemia.