TIME TO THERAPY AND SALVAGE IN MYOCARDIAL-INFARCTION

Objectives. This study sought to examine the influence of time to repe rfusion on myocardial salvage. Background. Major trials of reperfusion therapy for myocardial infarction (MI) have demonstrated improved out come for patients achieving earlier reperfusion, However, some patient s experience significant benefit despite delayed reperfusion. Methods. Fifty five patients with a first anterior MI underwent successful rep erfusion therapy (angioplasty or thrombolysis). Technetium-99m (Tc-99m ) sestamibi was injected before reperfu sion therapy and again at hosp ital discharge to determine the myocardial salvage index for each pati ent. Residual flow to the infarct territory was assessed by the nadir of the Tc-99m sestamibi count-profile curve. Results. The salvage inde x showed wide variability (range -0.04 to 1.0), and extreme values wer e seen in 34.5% of the group (<0.10 in 9%, >0.90 in 25%). A high salva ge index was associated with reperfusion therapy before 2 h (p = 0.02) or good residual blood flow (p < 0.01). For the 10 patients who recei ved reperfusion therapy within 2 h, residual blood flow was not correl ated with salvage (p = 0.12), For the 45 patients treated after 2 h, r esidual blood flow correlated significantly with salvage (r = 0.57, p < 0.0001). There was a significant interaction (p < 0.05) between resi dual blood flow and time to therapy, indicating that the effect of eac h variable on salvage depended on the value of the other. Multiple his toric and hemodynamic variables were examined, but none demonstrated a ny association with residual flow or myocardial salvage. Conclusions. In patients with acute MI, successful reperfusion therapy within 2 h i s associated with the greatest degree of myocardial salvage. For patie nts treated after 2 h, residual blood flow to the infarct related terr itory appears to be the most important determinant of myocardial salva ge.