Right ventricular dominant myocarditis requiring cardiac resynchronization therapy-defibrillator: a case report
A 43-year-old Japanese woman visited a local hospital with a 3 week history of chest discomfort and subsequent dyspnoea, nausea, and epigastralgia. She was previously healthy, had no medical or surgical history, took no regular medications, had no allergies, and had no history of smoking or drinking. Her left ventricular ejection fraction (LVEF) was preserved at 55% on admission; however, she presented with ST elevation in a wide range of leads, troponin T elevation, and pericardial effusion on computed tomography (CT) scan. On the day of her hospitalization, the patient suddenly collapsed from sustained ventricular tachycardia (VT). VT was first terminated through cardioversion, but soon recurred. VTs were refractory despite repeated cardioversions; thus, the patient was transferred to the angiography room and inserted a peripheral veno-arterial extracorporeal membrane oxygenation (VA-ECMO) circuit under cardiopulmonary resuscitation. VT was controlled by the next cardioversion after starting VA-ECMO, intra-aortic balloon pump (IABP), and continuous amiodarone infusion. RV pacing was started against a complete atrioventricular block (CAVB) after VT termination. Coronary angiography showed no significant stenosis. Bilateral ventriculography revealed RV diffuse systolic dysfunction, whereas left ventricular (LV) function was preserved (LVEF 50%). However, on the following morning, LV function was extremely deteriorated (LVEF 20%), and the aortic valve temporarily closed due to extremely impaired left ventricular function. Therefore, she was transferred to Chiba University Hospital via an air ambulance for evaluation regarding treatment with a ventricular assist device.\nOn arrival at Chiba University Hospital, the patient was conscious and alert with the support of VA-ECMO and IABP with sustained VT (Figure\n). After the VT was spontaneously terminated, CAVB was present. An electrocardiogram revealed CAVB with ventricular pacing beats and ST elevation in leads III, aVF, and V1 through V4 (Figure\n). The blood pressure was 84/50 mmHg under stable circulation, whereas heartbeat depended on ventricular pacing with a high pacing threshold. Chest radiography revealed a mildly enlarged cardiac silhouette (cardiothoracic ratio, 60%) without vascular redistribution (Figure\n). Transthoracic echocardiography indicated diffusely reduced biventricular wall motion (LVEF 14%) with diffuse myocardial oedema in the LV [interventricular septum (IVS) thickness: 13 mm, LV posterior wall thickness: 12 mm] without significant valvular disease (Figure\n). Plasma brain natriuretic peptide level was 11.9 pg/mL, serum creatinine was 0.41 mg/dL, and C-reactive protein was 1.75 mg/dL. Rheumatoid and antinuclear antibodies were negative. Endomyocardial biopsy (EMB) from the RV-IVS on the day of transfer demonstrated a complete degeneration of cardiomyocytes with massive infiltration of lymphocytes (Figure\n). She was pathologically diagnosed with lymphocytic myocarditis, although specific viral antibodies were not detected with paired serum examination.\nAs LV function gradually improved, the pacing threshold was lowered. However, CAVB persisted and VTs were easily induced once RV pacing was turned off. Finally, VA-ECMO was successfully weaned off on the 8th hospital day, and IABP was removed on the 11th day. RV temporary pacing was stopped on Day 12 because the heart rate was maintained higher than 70 b.p.m. as ventricular escape rhythm and VT had not recurred.\nEchocardiography on Day 19 showed RV dilatation with akinesis and high echogenicity in the IVS and RV apex, severe tricuspid regurgitation (TR) with valve separation, and thrombus in the RV apex, whereas LVEF improved to 59% (Figure\n). An oral anticoagulant was initiated, which was switched from continuous intravenous heparin. A diuretic was added due to the presentation of right-sided heart failure with concomitant oedema of the extremities, and an angiotensin II receptor blocker was initiated to prevent LV remodelling. On Day 20, contrast-enhanced CT scans indicated pulmonary thromboembolism (PE) along with a thrombus in the RV (Figure\n) and a deep vein thrombosis. Cardiac magnetic resonance (CMR) on Day 30 showed a wide range of late gadolinium enhancement (LGE), including at the RV apex to free wall, IVS, and LV apex (Figure\n). After we confirmed disappearance of the RV thrombus via CT scan on Day 42, a cardiac electrophysiological study was performed. R-wave sensitivity was about 1 mV, and pacing threshold was higher than 5 V/0.4 ms in the RV. In addition, refractory VTs were easily induced. Therefore, she required both biventricular pacing and a defibrillator. She was provided with cardiac resynchronization therapy with a defibrillator (CRT-D) device on Day 49 and was discharged in good condition on Day 56. Serial follow-up echocardiography indicated severe RV dysfunction and dilatation with severe TR. LV was deformed by IVS leftward shift, and apparent LVEF had reduced to approximately 30% after 6 months of CRT-D implantation; however, the patient was able to return to work as a hairdresser without any worsening of heart failure.