New-onset angina preceding acute myocardial infarction is associated with improved contractile recovery after thrombolysis.

BACKGROUND

Ischaemic preconditioning reduces myocardial infarct size in animal models. Clinical data suggest that episodes of angina immediately before acute myocardial infarction may be associated with smaller infarct size in man. However, it is unclear whether ischaemic episodes preceding acute myocardial infarction also affect contractile recovery in patients.

OBJECTIVE

In this study we investigated the recovery of regional myocardial function after thrombolysis in two groups of patients at their first Q-wave acute myocardial infarction; in one group (n = 42) myocardial infarction occurred unheralded, whereas patients of the second group (n = 48) had experienced new-onset angina in the 48 h that preceded infarction. Echocardiographic analysis of myocardial regional function in the infarct area was done at 2, 24 and 72 h after thrombolysis, and at 1 week, and 1 and 3 months follow-up.

RESULTS

Peak level of MB-creatine kinase was significantly lower in patients with new-onset angina (96 +/- 47 as compared with 221 +/- 108 IU.l-1, P < 0.01), as was the area under the MB-creatine kinase curve (1321 +/- 876 as compared to 3879 +/- 1555 U.l-1/36 h, P < 0.01). Hypokinetic segments were fewer in patients with pre-infarction angina. Similarly, wall motion score improved significantly earlier in patients who had new-onset angina before acute myocardial infarction. Thus, contractile recovery was more rapid in patients with previous angina than in those in whom infarction occurred unheralded. Complications during the in-hospital outcome and other variables considered during the 4-week follow-up were similar between groups.

CONCLUSIONS

Patients who experienced new-onset angina before acute myocardial infarction showed better recovery of regional function after thrombolysis. Our study supports the hypothesis that brief periods of ischaemia immediately before myocardial infarction may precondition the human heart, thus improving contractile recovery.