BACKGROUND: Pathological early Q waves (QW) are associated with adverse outcomes in patients with ST-segment-elevation myocardial infarction (STEMI). Primary percutaneous coronary intervention (PCI) may therefore be less beneficial in patients with QW than in patients without QW. Myocardial salvage index and microvascular obstruction (MVO) are markers for reperfusion success. Thus, to clarify the benefit from primary PCI in STEMI patients with QW, we examined the association between baseline QW and myocardial salvage index and MVO in STEMI patients treated with primary PCI.

METHODS AND RESULTS: The ECG was assessed before primary PCI for the presence of QW (early) in 515 STEMI patients. The patients underwent a cardiac magnetic resonance imaging scan at day 1 (interquartile range [IQR], 1-1) and again at day 92 (IQR, 89-96). Early QW was observed in 108 (21%) patients and was related to smaller final myocardial salvage index (0.59 [IQR, 0.39-0.69] versus 0.65 [IQR, 0.46-0.84]; P<0.001) and larger MVO (1.4 [IQR, 0.0-5.4] versus 0.0 [IQR, 0.0-2.4]; P<0.001) compared with non-QW. QW remained associated with both final myocardial salvage index (β=-0.12; P=0.03) and MVO (β=0.18; P=0.001) after adjusting for potential confounders.

CONCLUSIONS: Patients presenting with their first STEMI and early QW in the ECG had smaller myocardial salvage index and more extensive MVO than non-QW despite treatment within 12 hours after symptom onset. However, final myocardial salvage index in patients with QW was substantial, and patients with QW still benefit from primary PCI.

CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01435408.