Background:
In ISCHEMIA, an initial invasive strategy did not significantly reduce rates of cardiovascular events or all-cause mortality compared with a conservative strategy in patients with stable ischemic heart disease and moderate/severe myocardial ischemia. The most frequent component of composite cardiovascular endpoints was myocardial infarction.
Methods:
ISCHEMIA prespecified that the primary and major secondary composite endpoints of the trial be analyzed using two MI definitions. For procedural MI, the primary MI definition used CK-MB as the preferred biomarker whereas the secondary definition used cardiac troponin. Procedural thresholds were >5 times URL for PCI and >10 times for CABG. Procedural MI definitions included (i) a category of elevated biomarker only events with much higher biomarker thresholds (ii) new ST segment depression of ≥ 1mm for the primary and ≥ 0.5 mm for the secondary definition and (iii) new coronary dissections ≥ NHLBI grade 3. We compared MI type, frequency, and prognosis by treatment assignment using both MI definitions.
Results:
Procedural MI's accounted for 20.1% of all MI events with the primary definition and 40.6% of all MI events with the secondary definition. Four-year MI rates in patients undergoing revascularization were more frequent with the invasive vs conservative strategy using the primary [2.7% vs. 1.1%; adjusted HR 2.98 (95% CI 1.87, 4.73)] and secondary [8.2% vs. 2.0%; adjusted HR 5.04 (95% CI 3.64, 6.97)] MI definitions. Type 1 MI's were less frequent with the invasive vs conservative strategy using the primary [3.40% vs. 6.89%; adjusted HR 0.53 (95% CI 0.41,0.69); p<0.0001], and secondary [3.48% vs 6.89%; adjusted HR 0.53 (95% CI 0.41, 0.69); p<0.0001] definitions. The risk of subsequent cardiovascular death was higher after a type 1 MI compared to no MI using the primary [adjusted HR 3.38 (95% CI 2.03,5.61); p<0.001] or secondary MI definition [adjusted HR 3.52 (2.11, 5.88); p<0.001].
Conclusions:
In ISCHEMIA, type 1 MI events using the primary and secondary definitions during 5-year follow-up were more frequent with an initial conservative strategy and associated with subsequent cardiovascular death. Procedural MI rates were greater in the invasive strategy and using the secondary MI definition.
Clinical Trial Registration:
URL: https://clinicaltrials.gov Unique Identifier: NCT01471522
Letter by Correia and Viana Regarding Article, “Myocardial Infarction in the ISCHEMIA Trial: Impact of Different Definitions on Incidence, Prognosis, and Treatment Comparisons”
