ST-segment elevation in acute pericarditis and myocardial involvement: electrocardiographic and clinical profiling

Background: Pericardium is considered electrically inert, but diffuse ST-elevation is an electrocardiographic marker of acute pericarditis. We hypothesised that ST-elevation in acute pericarditis may reflect underlying myocardial involvement. Accordingly, this study aimed to assess the association between ST-elevation and myocardial involvement in pericarditis patients and to further characterise the clinical features and long-term outcomes of myopericarditis compared with isolated pericarditis. Methods: This longitudinal multicentre study included 351 pericarditis patients (328 recurrent; 180 females), 70/351 with myopericarditis, defined by troponin elevation and/or suggestive cardiac MRI. Results: 121 patients had ST-elevation (34.5%); they were younger: 38 years (23–53) vs 47 (31–58) (median (IQR)) (p<0.001), more often male: 63.6% (77/121) vs 40.9% (94/230) (p<0.001) and had higher C reactive protein values: 92.0 (35–170) vs 58.4 mg/L (15.8–137.5) (median (IQR)) (p=0.002) and less frequent pericardial effusions: 71.1% (86/121) vs 83.5% (192/230) (p=0.004).Myocardial involvement was diagnosed in 70/351 (19.9%) patients, occurring more frequently among those with ST-elevation: 26.4% (32/121), compared with those without: 16.5% (38/230) (p=0.035). ST-elevation predicted myocardial involvement with an OR of 1.82 (95% CI 1.07 to 3.10). Compared with isolated pericarditis, patients with myopericarditis were more frequently male: 61.4% (43/70) vs 45.6% (128/281) (p=0.023) and had a higher prevalence of transient systolic dysfunction: 13.5% (7/52) vs 2.1% (3/141) (p=0.004). During follow-up, myopericarditis patients had a lower remission rate: 18.5% (12/65) vs 31.2% (82/263) (p=0.047) and a higher annual hospitalisation rate (median 0.5 vs 0.4/year, p=0.010), while recurrence rates and disease duration were similar. Treatment strategies, including use of corticosteroids and interleukin 1 blockers, were also comparable. Conclusions: ST-segment elevation in acute pericarditis was associated with myocardial involvement, supporting the concept that the pericardium is electrically inert. Myopericarditis was associated with lower remission rates and slightly higher hospitalisation needs compared to isolated pericarditis, despite otherwise comparable recurrence rates and treatment strategies.