Shock-index as a novel predictor of long-term outcome following primary percutaneous coronary intervention.

UNLABELLED: Early identification of higher risk patients presenting with ST-elevation myocardial infarction (STEMI) and undergoing primary percutaneous coronary intervention (PPCI) will allow a more aggressive strategy and approach. The aim of this study was to evaluate the shock index (ratio of heart rate/systolic blood pressure on admission) as a predictor of mortality post PPCI in addition to other parameters.

METHODS: We analysed prospectively collected data on 3049 STEMI patients treated with PPCI in a large tertiary centre between March 2008-December 2011, out of which 2424 patients were aged up to 75 years (young) and 625 patients were older than 75 years (elderly).

RESULTS: Compared to younger patients, in-hospital mortality rates were four-fold higher in the elderly (11.5% vs 2.8%, odds ratio (OR) 3.5, 95% confidence interval (CI) 2.0-5.9). Cardiogenic shock (OR 8.7 (5.1-14.6)), non-TIMI3 (Thrombosis In Myocardial Infarction) flow post percutaneous coronary intervention (PCI) (OR 5.0 (3.1-7.9)), age over 75 (OR 3.5 (2.3-5.3)) and a positive shock index pre PPCI (OR 3.5 (2.0-5.9)) were the strongest independent predictors of in-hospital mortality. For long-term outcome (median follow-up period 454 days) we excluded 141 (4.6%) patients that died during the initial hospital stay. Previous angina (hazard ratio (HR) 2.9), and previous cerebrovascular events (HR 3.7) were predictors of adverse outcome in the younger patients, while previous myocardial infarction (HR 2.0) and a positive shock index (HR 2.3) were predictors in the elderly. Cardiogenic shock prior to PPCI was not able to predict long-term outcome for in-hospital survivors.

CONCLUSION: Mortality rates following PPCI were higher in elderly patients although remained acceptable. Invasively measured shock index before PPCI is the strongest independent predictor of long-term outcome in elderly patients. In addition, predictors of in-hospital mortality were similar across different age groups but differed significantly in relation to longer-term mortality.