Treatment of acute myocardial infarction - Direct PTCA or thrombolysis?

Since reperfusion of the infarct-related coronary artery has been established as a mainstay in the treatment of acute myocardial infarction (AMI) mechanical recanalization by direct angioplasty has been used as an alternative to the standard treatment with thrombolysis. Direct PTCA is more efficient than thrombolysis in terms of reperfusion rates, whereas thrombolysis is more readily available. Thrombolysis reduces mortality from AMI by approximately 25%. The clinical efficacy is strongly time-dependent, and treatment within the first hour of AMI improves survival by nearly 50% by preventing transmural infarction in a significant proportion of the patients. The disadvantage of thrombolysis is its limited efficacy in terms of rapid, complete and sustained patency of the infarct vessel yielding optimal results in only 50% of the patients. Direct PTCA is generally agreed to be more efficient to recanalize the infarct vessel, but its clinical advantage remains controversial. The first randomized studies of direct PTCA in AMI from highly specialized centers in selected patients reported success rates of coronary reperfusion up to 97% resulting in a trend to less death and reinfarction, but the differences were significant only in a metaanalysis of these small studies. The real world of direct PTCA has been depicted by a large registry in Germany of the Arbeitsgemeinschaft Leitender Kardiologischer Krankenhausarzte (ALKK) now including more than 4,000 direct PTCA-procedures since 1994. In this registry, the success rate of direct PTCA was 87% as defined by a final TIMI-grade 3 perfusion of the infarct vessel which is close to the data of the MITI-registry and the GUSTO IIb study. Failed PTCA was associated with an exceptionally high mortality rate of 36% confirming earlier observational reports. The non-randomized comparison of thrombolysis and direct PTCA in the MITI-registry showed no difference in survival or reinfarction rates, and the randomized GUSTO IIb substudy of direct PTCA versus front-loaded alteplase showed a small advantage in death and reinfarction rates at 30 days which dissipated over time leaving no significant clinical advantage of direct PTCA over thrombolysis at 6 months. Thus, in myocardial infarction in general the advantage of direct PTCA over thrombolysis is at best minimal. The reason is very probably the longer time lag until the procedure is started, the lower success rate as compared to the first reports of some specialized centers, and the clearly negative impact of failed PTCA on survival. Moreover, the immediate success of direct PTCA seems to be overestimated by the operator as demonstrated by comparison of central and local estimates of the TIMI flow rates in GUSTO IIb. Improvements of direct PTCA in AMI might be possible by coronary stenting which has markedly increased to more than 60% during the last year in the ALKK-registry. This was accompanied by a slight decrease in death and reinfarction rates. Further improvements can be expected from GP IIb/IIIa platelet antagonists which are under clinical investigation. It has been claimed, that in cardiogenic shock direct PTCA is more effective than thrombolysis. This hypothesis is based on comparison of failed versus successful PTCA-attempts, but this comparison is not valid since failed procedures clearly increase mortality In the GUSTO-I study patients with cardiogenic shock had lower mortality with than without an early coronary angiogram. This survival advantage, however, was independent of revascularization since only half of the patients with an early angiogram had PTCA. The same was observed in the International Shock Registry: reflecting significant selection bias in that patients in relatively better condition will be taken to the cathlab whereas apparently hopeless cases will not. In the ALKK-registry; half of the patients in cardiogenic shock died after direct PTCA casting doubt on the presumed high clinical efficacy of this strategy A definitive answer to the role of PTCA in cardiogenic shock could only be given by randomized studies, but these have been stopped prematurely for poor patient recruitment. Thus, the consensus to prefer PTCA over thrombolysis in cardiogenic shack is not based an firm clinical data.