Acute chest pain in a patient with left bundle branch pacing.

We present a patient with left bundle branch (LBB) electronic ventricular pacing with chest pain. ECG showed ventricular pacing and ST elevation in the inferolateral leads. At first it was felt that the Sgarbossa criteria for STEMI in electronic ventricular pacing are not met. However, as symptoms persisted, emergency coronary angiography was performed showing complete occlusion of the left circumflex artery. As LBB pacing results in narrow QRS complexes with incomplete right bundle branch block, ST-segment deviation should not be ignored and the Sgarbossa criteria for patients with LBB block or right ventricular electronic pacing should not be applied.