Tuberculous pericarditis

EDITOR, - The case of tuberculous pericarditis presented by C P Clifford and G J Davies1 contained a misleading characterisation of the findings on admission as classic tamponade. Kussmaul's sign and an abnormal third heart sound are inconsistent with the physiology of classic tamponade.2 Indeed, it is the virtual elimination of the rapid filling period necessary to produce a third heart sound that is a classic feature of tamponade. It is far more likely that this patient already had, under the tamponading fluid, an epicardial constriction with its typically mixed picture; a pulsus paradoxus with a 20 mm Hg fall in blood pressure is unusual while a third heart sound and Kussmaul's sign are the rule in constriction.2 Although acute tuberculous pericarditis can progress rapidly to acute or subacute constriction, this was not such a case.34

Finally, I wish to argue against the term “pericardial knock.” The abnormal early diastolic sound of constrictive pericarditis does not usually present an auscultatory knocking quality. More importantly, this description clouds concepts even if this form of the third heart sound did always “knock.” The early diastolic sound of constrictive pericarditis is an especially early and often loud third heart sound with all necessary abnormal dynamics-accelerated early ventricular filling, with abrupt deceleration, into ventricles made abnormally stiff by pericardial scarring.4