An exclusion criterion for acute pericarditis

Notwithstanding its characterization by the four diagnostic criteria enumerated by the authors,1 acute pericarditis (AP) has electrocardiographic (ECG), echocardiographic and clinical stigmata which overlap with those documented in takotsubo cardiomyopathy (TTC)2 and in pericarditis secondary to acute myocardial infarction (AMI).3 In a study which compared electrocardiographic stigmata in eight TTC patients vs. eight AP patients, concave-shaped ST-segment elevation was equally prevalent (75% prevalence) in TTC and in AP.2 Five TTC patients exhibited PR-segment depression in at least one inferior lead,2 inferior leads being the ones most likely to be characterized by this phenomenon in AP.4 Strictly speaking, the diagnostic label should be myopericarditis when clinical and ECG stigmata of suspected AP are associated with troponinosis,5 as in the reported case.1 Furthermore, in myopericarditis, it is the presence of subepicardial atrial injury which generates PR-segment depression.6 By the same token, it is the presence of atrial ischaemia which generates similar PR-segment deviation in patients who have inferior AMI in the absence of pericarditis.7 Consequently, when effusive pericarditis occurs as a complication of inferolateral AMI the ECG profile may be characterized, not only by concave ST-segment elevation in many leads, but also by PR-segment depression,3 simulating the recently reported case of AP.1 It is the absence of unequivocal differentiation between AP/myopericarditis and AMI which was largely responsible for the 24.7% frequency of inappropriate urgent coronary angiography among 146 patients with ST-segment elevation attributable to the AP/myopericarditis syndrome.8 To mitigate the risk of inappropriate coronary angiography urgent echocardiography has been proposed to support or refute the presence of AMI-related regional wall abnormalities.8 That strategy would also support or refute TTC-related regional dyskinesia.9 Absence of regional dyskinesia would then favour the diagnosis of AP/myopericarditis, thereby obviating inappropriate coronary angiography. Diagnostic criteria for AP/myopericarditis should be amended to include this specification. Conflict of interest: None declared.