Therapies may reduce short-term rates of nonfatal myocardial infarction (MI) without a detectable effect on mortality. We sought to estimate the long-term clinical implications of nonfatal MI occurring within the first 3 and 6 months after initial cardiac catheterization.

We included consecutive patients with significant coronary artery disease (≥75% stenosis in ≥1 epicardial segments) undergoing diagnostic catheterization between January 1, 1999, and September 30, 2006. Landmark analyses were performed for patients surviving at 3- and 6-month follow-up. At these times, patients were divided into groups based upon occurrence of a nonfatal MI subsequent to catheterization.

Among 14,890 patients alive at 3 months (669 with MI and 14,221 without an MI), having an MI during the initial 3-month period was a significant predictor of reduced 4-year survival (77.1% vs 83.5%, hazard ratio 1.40, 95% CI 1.21-1.63, P < .001), survival free of MI (68.4% vs 78.5%, hazard ratio 1.50, 95% CI 1.32-1.71, P < .001), and survival free of MI or revascularization (59.7% vs 68.5%, hazard ratio 1.34, 95% CI 1.19-1.51, P < .001). Adjusted hazard ratios were similar for patients surviving to 6 months (804 with MI and 13,842 without an MI).

Nonfatal MIs occurring within the first 3 and 6 months after diagnostic catheterization are associated with a significant increase in the risk for subsequent clinical events. Clinical studies with limited follow-up periods may underestimate the long-term value of therapies that reduce early MI rates as downstream benefits continue to accrue over time.