Comparisons between biopsy-proven versus clinically diagnosed cardiac sarcoidosis

Objectives Diagnosis of cardiac sarcoidosis (CS) without histological evidence remains controversial. This study aimed to compare characteristics and outcomes of histologically proven versus clinically diagnosed cases of CS, which were adjudicated using Heart Rhythm Society or Japanese Circulation Society criteria. Methods A total of 512 patients with CS (age: 62±11 years, female: 64.3%) enrolled in the multicentre registry were studied. Histologically confirmed patients were classified as 'biopsy-proven CS', while those with the presence of strongly suggestive clinical findings of CS without histological evidence were classified as 'clinical CS'. Primary outcome was a composite of all-cause death, heart failure hospitalisation and ventricular arrhythmia event. Results In total, 314 patients (61.3%) were classified as biopsy-proven CS, while 198 (38.7%) were classified as clinical CS. Patients classified under clinical CS were associated with higher prevalence of left ventricular dysfunction, septal thinning, and positive findings in fluorodeoxyglucose-positron emission tomography or Gallium scintigraphy than those under biopsy-proven CS. During median follow-up of 43.7 (23.3-77.3) months, risk of primary outcome was comparable between the groups (adjusted HR: 1.24, 95% CI: 0.88 to 1.75, p=0.22). Similarly, the risks of primary outcome were comparable between patients with clinical isolated CS who did not have other organ/tissue involvement, and biopsy-proven isolated CS (adjusted HR: 1.23, 95% CI: 0.56 to 2.70, p=0.61). Conclusions A substantial number of patients were diagnosed with clinical CS without confirmatory biopsy. Considering the worse clinical outcomes irrespective of the histological evidence, the diagnosis of clinical CS is justifiable if imaging findings suggestive of CS are observed.