When a Pseudo-Infarct Electrocardiogram (ECG) Pattern in a Posterior Accessory (Wolff-Parkinson-White) Pathway Masks a True Inferior Infarct

BACKGROUND Wolff-Parkinson-White (WPW) pattern is due to a pre-excitation leading to characteristic ECG changes in sinus rhythm as short PR interval, the presence of delta waves, wide QRS complexes, and potentially Q wave-T wave vector discordance (pseudo-infarct pattern). These later changes can mask the underlying ECG depolarizing solely through the His-Purkinje system. Our case highlights how the ECG of a WPW pattern with a pseudo-infarct pattern can in fact mask a true infarct on the underlying ECG without pre-excitation. CASE REPORT A 61-year-old diabetic man with a recent history of supra-ventricular tachycardia (SVT) presented with the ECG characteristic of a Wolff-Parkinson-White pattern i-e short PR interval of 0.10 s (<0.12 s) and the presence of delta waves in sinus rhythm. In addition, there was a wide significant Q wave in the inferior leads meeting the criteria for significant and pathologic Q waves, related to the pre-excitation and known as a pseudo-infarct pattern. The patient underwent successful ablation of his left inferoseptal accessory pathway. The pre-excitation pattern (short PR and delta wave) disappeared after successful ablation revealed a narrower Q wave in inferior leads, likely from unexpected true old inferior infarction, which was later confirmed by 2D echocardiogram and nuclear stress test (fixed inferior defect). CONCLUSIONS The presence of pseudo-infarct pattern due to a WPW does not always preclude the presence of underlying true infarct pattern, especially in the presence of coronary artery disease risk factors.