Prognostic value of fluorine-18 fluoro-2-deoxyglucose positron emission computed tomography in patients with unexplained atrioventricular block.

BACKGROUND: The cause of atrioventricular conduction block (AVB) remains unexplained in a significant number of patients. Granulomatous myocarditis is an uncommon but important cause of AVB. Fluorine-18 fluoro-2-deoxyglucose positron emission computed tomography (18-FDG PET) scan has emerged as a sensitive tool for diagnosing granulomatous myocarditis.

OBJECTIVE: The purpose of this study was to evaluate the prognostic value of 18-FDG PET scan in patients with unexplained AVB.

METHODS: Patients age 18-55 years presenting with unexplained AVB and requiring a permanent pacemaker were evaluated with a fasting 18-FDG PET scan. Transthoracic echocardiography was performed at baseline and at follow-up. Major adverse cardiac events (ventricular tachycardia, heart failure, cardiac death) were noted during follow-up.

RESULTS: Over a period of 3 years, 35 patients (20 females, 15 males; mean age 43.67 ± 11.21 years) were included in the study. Abnormal myocardial FDG uptake was noted in 15 patients (42.8%). Four patients consented for biopsy of paracardiac FDG avid lymph nodes, which revealed granulomatous inflammation (one of which grew Mycobacterium tuberculosis in culture). Mean follow-up period was 24 months. Major adverse cardiac events were significantly higher in the patients with abnormal PET uptake (P < .01) compared to those with normal scans.

CONCLUSION: Patients with high-degree AVB and abnormal myocardial 18-FDG PET uptake have more adverse cardiac events and worse outcomes. Early screening for myocardial inflammation and appropriate treatment may prevent these complications. Tuberculosis may be an important cause of unexplained AVB, apart from sarcoidosis, in developing countries such as India.