Temporal trends in cardiogenic shock treatment and outcomes among Ontario patients with myocardial infarction between 1992 and 2008

Background — Clinical trials have demonstrated that emergent revascularization improves survival of patients with acute myocardial infarction (AMI) complicated by cardiogenic shock (CS). However, rates of uptake and impact on outcomes remain uncertain.

Methods and Results — The study identified 9,750 patients (3.1%) with CS among 311,183 AMI patients in the Ontario Myocardial Infarction Database between 1992 and 2008 (55.8% men; mean age, 73 years). CS incidence, mortality, revascularization, and transfers from nonrevascularization sites were studied over 3 periods: period 1, before the 1999 American College of Cardiology/American Heart Association AMI guidelines recommending urgent revascularization for patients <75 years; period 2 (1999 to 2004); and period 3, after 2004 guideline revisions suggesting revascularization for patients ≥75 years. Compared with period 1, period 3 was marked by significantly lower CS incidence (3.4% versus 2.6%), increase in transfers from nonrevascularization sites (10.6% versus 23.9%), and adjusted 1-year mortality rates (81.9% versus 71.5%; all comparisons statistically significant). Admission to nonrevascularization sites was associated with lower revascularization rates (8.6% versus 46.6%, P<0.001) and higher adjusted 1-year mortality rates (78.8% [95% confidence interval, 77.4 to 80.2] versus 71.9% [95% confidence interval, 69.8 to 74.1]). Patients ≥75 years of age were less likely to be revascularized or transferred. The greatest increase in transfers from nonrevascularization sites occurred between periods 1 and 2 for patients <75 years (16.5% to 31.4%; P<0.001) and between periods 2 and 3 for patients ≥75 years (6.7% to 12.8%; P<0.001).

Conclusions — Publication of American College of Cardiology/American Heart Association guidelines was followed by increased revascularization and transfer rates, along with declining mortality rates among Ontario AMI patients with CS. These results highlight possibilities for further improvement, particularly among patients eligible for transfer from nonrevascularization sites.