Involvement of heart in tuberculosis (TB) occurs in one to two percent of patients with tuberculosis [1, 2]. The most common site involved is pericardium, and tuberculous involvement of the myocardium is exceedingly rare. The introduction of effective antituberculous therapy has further decreased the incidence [3]. The earliest report of myocardial TB was in 1664 by Maurocordat and second report in 1761 by Morgagni [4]. The myocardium can be affected either by direct extension or by retrograde lymphatic drainage from mediastinal nodes; direct spread from tuberculous pericarditis can also occur [5]. Moreover, during the hematogenous phase of dissemination of primary TB, any and every tissue and organ in the body is liable to seeding by mycobacteria and consequent pathological changes.
Myocardial TB is often not diagnosed during life, but if suspected the diagnosis can be established by an endomyocardial biopsy [6]. Three types of myocardial involvement have been described viz. tuberculomas of the myocardium with central caseation (seen in our patient), miliary tubercles of the myocardium complicating generalized miliary disease and the uncommon diffuse infiltrative type associated with tuberculous pericarditis [7]. The right heart, particularly the right atrium, is most often affected, probably because of the frequent involvement of the right mediastinal lymph nodes with consequent involvement of the myocardium [8], although right ventricle [3] and left ventricle [4] have been found to be involved most frequently in different series. Myocardial TB can manifest in various forms. Rhythm disturbances include supraventricular arrhythmias [3, 6], ventricular arrhythmias [9] or varying degrees of conduction blocks [10], and sudden cardiac death is also described [5, 11]. Right ventricular outflow tract obstruction [3, 12, 13], ventricular aneurysm [4, 13], ventricular pseudoaneurysm [14], aortic insufficiency [15], coronary arteritis [10, 13], or congestive heart failure [6, 16, 17] have also been described in literature. Recently, magnetic resonance imaging has also been used in the diagnosis of myocardial TB [18].
Antitubercular drugs are the cornerstone of therapy [6], and surgery [12, 14–16] is indicated only in complicated cases. Paradoxically, our patient presented with features of congestive heart failure, and echocardiography showed severe left ventricular systolic dysfunction inspite of being on anti-tuberculous therapy which had resulted in bacteriological improvement of the pulmonary lesions. The reason for this is not clear, but one likely reason is probably enhanced immunogenicity of the host to tubercle bacilli. This has been called as a 'paradoxical response' [19]. In this regard, at least theoretically, glucocorticoids may have a role along with antituberculous therapy.
In conclusion, although myocardial involvement by tuberculosis is rare, it should be suspected as a cause of congestive heart failure in any patient with features suggestive of TB, as cases of myocardial TB almost always show evidence of TB at other sites [6]. Increasing recognition of the entity, and the use of endomyocardial biopsy may help us detect more cases of this "curable" form of cardiomyopathy especially in areas of high prevalence of TB. It may not be out of place to state.... Look and ye shall find....