Sudden cardiac death and tuberculosis - how much do we know?

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is a major killer in the world and pulmonary infections are well characterised. It is not widely known that TB myocarditis leads to sudden cardiac deaths (SCD), especially in young people. Unlike other causes of SCD, risk factors such as family history are absent and patients are asymptomatic. This makes risk stratification and interventions with implantable cardiac defibrillators extremely difficult. Only a few cases of TB myocarditis SCD have been reported since 1977 and all of which were diagnosed at autopsy. The majority of reports showed extensive TB infiltration of the myocardium with no systemic symptoms. Concurrent miliary or systemic TB was postulated to be the source of TB myocarditis. The mechanism of death has been hypothesized to be ventricular tachyarrhythmia. Pulmonary TB has also been reported to cause sudden death. However, ventricular arrhythmias have not been recorded, suggesting a different mechanism to TB myocarditis SCD, which centres upon cardiopulmonary collapse leading to bradycardia. Although anti-tuberculous chemotherapy is efficacious in the treatment of TB myocarditis, there is no evidence to suggest that it is effective in the prevention of SCD. It remains to be seen whether better global control of TB disease burden will result in reductions in SCD. Furthermore, no experimental data exist on the link between TB myocarditis SCD and arrhythmias. We propose a unifying diagnostic system for TB myocarditis based on the current data and molecular techniques. This is likely to require updates as more evidence becomes available.