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Thrombus aspiration is a mechanistically logical adjunct therapy to primary angioplasty for acute myocardial infarction. We use the data from thrombus aspiration RCTs to quantitatively explore the implications for trialing this and other therapies, in the modern era of STEMI where highly effective RCT-proven therapy already provides very low mortality.
In the first part of the study we perform a meta-analysis of RCTs of thrombus aspiration. In the second part we determine the number of patients that would be required to definitively answer the role of thrombus aspiration in the context of current STEMI mortality rates.
All-cause mortality at 30 days or 6-12 months was available in 13 trials (10,375 patients). At 30 days (10 trials; 9,713 patients) there was no significant effect of thrombus aspiration on all-cause mortality (OR 0.87, 95% CI 0.69-1.11, p=0.28). During longer-term follow-up (8 trials; 2,118 patients) there was no statistically significant effect of thrombus aspiration on all-cause mortality (OR 0.66, 95% CI 0.41-1.04, p=0.08).
Our model demonstrates that to reliably detect a relative risk reduction of 10%, with a current 30-day mortality of 3% in the control arm of trials, would require ∼100,000 patients.
STEMI mortality is now so low that vast numbers of patients are required to reliably identify the effect of new therapies on mortality. The lack of statistically significant mortality reduction from routine thrombus aspiration in STEMI is a reflection of this. To advance this field requires a multi-center trial, with a patient group several orders of magnitude higher than those currently being performed.