In patients with ST-segment elevation myocardial infarction (STEMI) and single-vessel disease with complete of occlusion, a symptom-to-balloon time of >121 minutes is associated with increased infarct size as well as a high grade of transmural necrosis, according to a study published in the Journal of the American Heart Association. These findings suggest that the optimal time to reperfusion after STEMI with no residual antegrade or collateral flow may be less than suggested by current guidelines.
Patients with first-time STEMI and single-vessel disease were eligible to enroll from 4 institutions (Stuttgart and Tübingen, Germany; Innsbruck, Austria; Bern, Switzerland) if they presented with a complete occlusion with TIMI (Thrombolysis in Myocardial Infarction) score of 0, absence of collateral flow (Rentrop score 0), and an onset of symptoms of <12 hours (n=164). The patients underwent primary percutaneous coronary intervention (PCI), and pre- and post-PCI coronary angiographies were performed in each participant.
To determine the area at risk as well as infarct size, interventional cardiologists used late gadolinium enhancement cardiac magnetic resonance (CMR) imaging assessments. Late gadolinium enhancement CMR imaging was also used to determine myocardial salvage index, transmurality index, and transmurality grade (0-50%, 51-75%, 76-100%).
The cohort was comprised of predominantly male (80%) patients, with an overall age of 54±11 years. A median of 4 days passed after STEMI before CMR was performed. The best diagnostic cutoff for a symptom-to-balloon time of 121 minutes was identified with a receiver operating characteristic curve (area under the curve: 0.81) suggesting transmural necrosis.
A symptom-to-balloon time of >121 minutes was associated with an increased infarct size as well as an increased transmurality index and transmurality grade (all P <.01). Compared with symptom-to-balloon times of ≤121 minutes, a time of >121 minutes was associated with decreased myocardial salvage index (P <.001). Microvascular obstruction was more common in patients with symptom-to-balloon times of >121 minutes (P =.03).
Limitations of the study included the relatively small sample size as well as the single-arm design.
“A symptom-to-balloon time >121 minutes caused a high grade of transmural infarction (and low [myocardial salvage index]),” the researchers explained, “underscoring the paramount importance of the symptom-to-balloon time in the wavefront of myocardial ischemia in patients not protected by a certain extent of residual myocardial blood flow from ante- or retrograde.”
Greulich S, Mayr A, Gloekler S, et al. Time-dependent myocardial necrosis in patients with ST-segment-elevation myocardial infarction without angiographic collateral flow visualized by cardiac magnetic resonance imaging: results from the multicenter STEMI-SCAR project. J Am Heart Assoc. 2019;8(12):e012429.