974-45 Prolonged Myocardial Dysfunction After Exercise-Induced Ischaemia - Myocardial Stunning or Delayed Reperfusion?

Abstract

Prolonged LV wall motion abnormalities (dyssynergy) frequently occur following exercise-induced angina. It is postulated that the underlying mechanism is myocardial stunning – i.e. contractile dysfunction persistent after ischaemia and reperfusion. We studied 8 men with angiographically proven coronary artery disease. We developed a novel protocol using echocardiography (ECHO) and 99-Tc sestamibi SPECT to simultaneously study wall motion and myocardial perfusion (The rapid myocardial uptake and minimal redistribution properties of sestamibi allow tomographic imaging of perfusion at the time ofinjection to be performed up to two hours later). Each pt underwent, in a randomised order and one week apart: (i) resting (baseline) sestamibi SPECT (ii) treadmill exercise test with sestamibi injected at peak ischaemia (iii) exercise treadmill test with sestamibi injected 15 mins after peak stress. ECHO was performed pre-exercise and at 15 min intervals post-exercise on each occasion. SPECT was performed 60 mins after sestamibi injection. In all pts, chest pain and ECG changes normalised within 9 mins postexercise. 6 pts (75%) developed prolonged regional dyssynergy (duration 30–60 mins) after both exercise tests. Quantitative ECHO data (mean ± s.d.) pre-exercise and 15 mins post-exercise are shown below: pre ex 15’ post ex p global ejection fraction (%) 61.3 ± 2.37 47.2 ± 2.93 <0.005 shortening fraction (dyssynergic segments) 4.06 ± 0.70 1.02 ± 0.59 <0.005 At peak stress, MISI perfusion defects (compared with baseline) were seen in the dyssynergic region in all 6 pts. At 15 mins post-exercise 2 groups of patients were identified: in one group (n = 3) perfusion had normalised in the dyssynergic regions indicating stunning. In the other group (n = 3) perfusion defects persisted indicating delayed reperfusion. dyssynergy at 15’ perfusion defect at 15’ mechanism group 1 yes no stunning group 2 yes yes delayed reperfusion These data suggest that (il following exercise-induced ischaemia normalisation of perfusion may be delayed despite the resolution of angina and ECG changes (ii) prolonged LV wall motion abnormalities following exerciseinduced ischaemia are likely to be due to a combination of myocardial stunning and persistent abnormalities of perfusion.