P15 AN OLD MYOCARDIAL INFARCTION UNMASKED BY UPGRADE TO HIS BUNDLE PACING: A CASE REPORT

Abstract

Abstract Case Report We report the clinical case of a 71–year–old man who was implanted with a dual–chamber PMK for complete atrioventricular block in 2012. In 2013 he was treated with two percutaneous coronary intervention (PCI) and stenting of the left anterior descending coronary artery (LAD) and right coronary artery (RCA).In March 2021, he was referred to our hospital for acute heart failure. Transthoracic echocardiography showed diffuse hypokinesis, with a left ventricular ejection fraction (LVEF) of 28% (46% six months earlier). ECG showed atrial flutter and paced ventricular rhythm with notch of the QRS complex in all 12 leads (Figure B). After achieving good clinical compensation with intravenous diuretics, the patient underwent coronary angiography with evidence of an unchanged coronary situation compared with 2013; Given the constant right ventricular pacing in the apex, we considered the LVFE decline as a consequence of pacemaker–induced cardiomyopathy (PICM)5 and a successful upgrade to HB pacing was performed. The surface ECG showed selective HB pacing with QRS width comparable to the native ECG (Figure A) but different morphology, because of evidence of QS complexes in V3–V6 and II, III, aVF (Figure C); physiological pacing obtained with selective HBP had made evident electrocardiographic signs of a previous myocardial infarction (MI). Discussion Very difficult is the diagnosis of a previous MI during RV pacing; to date, although considered questionable, we have only the criteria of Kochiadakis and colleagues (Figure 2A): – Notch of 0.04–second duration on the ascending limb of the S–wave of leads V3, V4, or V5 (Cabrera‘s sign). – Notching of the ascending stroke of the R wave in leads I, aVL, or V6 (Chapman‘s sign).– Q waves of 0.03 second duration in leads I, aVL, or V6. – Notch of the first 0.04 seconds of the QRS complex in leads II, III, and aVF. – Q wave of 0.03 seconds duration in leads II, III, and aVF. Occurring through the normal conduction system, HB pacing should generate a physiological myocardial repolarization resulting in a paced QRS complex with morphology and duration equal to the basal ECG, without alterations in the ventricular repolarization phase. As proof of the above, it was possible to appreciate that the transition from RV pacing to selective HB pacing allowed to unmasked the signs of a previous infero–lateral IMA, showing clear QS complexes in II, III, aVF, V3–V6. Conclusion Extremely old age should not discourage PM implantation, when indicated; age is obviously predictor of long–term death but is not predictor of precocious mortality. Acute periprocedural complication rate is low and generally comparable to that of younger populations.