P872 A case of transient atrioventricular block: the role of cardiac magnetic resonance imaging

A 42-year old man with no relevant past medical history presented to the emergency department for recurrent transient loss of consciousness in the last 12 hours. 3 weeks earlier he had flu-like symptoms which spontaneously resolved. Physical examination revealed altered mental state, heart rate 30 beats per minute, respiratory rate 30 cycles per minute, blood pressure 70/40mmHg and basal lung rales on pulmonary auscultation. Blood gas analysis revealed hyperlactacidemia with hypocapnia. Electrocardiogram showed third-degree atrioventricular block. Atropine was administrated (total dose 3mg) with no rate response. Transcutaneous pacing was initiated followed by a temporary transvenous pacemaker, removed after 72 hours. Transthoracic echocardiogram revealed compromised left ventricular systolic function (ejection fraction by Simpson’s method 45%) due to septal dyskinesia and reduced global longitudinal strain (-11%). Blood analysis revealed erythrocyte sedimentation rate 20mm/hr, C-reactive protein 2.43mg/dL and negative high-sensitivity troponin T (9.44ng/L). Rheumatologic screening was negative. Coronary computed tomography angiography revealed normal epicardial coronaries. Cardiac magnetic resonance imaging (CMRI) performed 7 days after admission revealed preserved left ventricular systolic function (ejection fraction 51%). Late gadolinium enhancement showed scared myocardium in the medium and basal segments of the interventricular septum, compatible with subacute myocarditis. Due to the history of recurrent syncope, a permanent pacemaker was inserted. The patient was discharged the day after. No further syncope occurred. In last pacemaker follow-up, 9 months after presentation, patient had 0% auricular and ventricular pacing and 100% sensing over the previous 6 months. Discussion Transient atrioventricular block is a well-known complication of myocarditis when there is involvement of the conduction system by the inflammatory reaction. However, in rare cases it can persist or recur. CMRI plays an important role in these cases. Gadolinium-enhanced CMRI can be used to access the extent of inflammation and cellular edema and delayed-enhanced CMRI can also be used to quantify scarring which has important prognostic value. CMRI can also play a crucial role in excluding infiltrative disorders with conduction system involvement. Also, in these patients, the transient aspect of atrioventricular block poses a challenge when deciding about permanent pacemaker insertion. Abstract P872 Figure. Magnetic Ressonance IVS