This study is the first to examine the prevalence of idiopathic pericardial effusion among those with HCM and the clinical and pericardial pathological profiles of these patients. The major findings of the study are: (1) prevalence of moderate to large pericardial effusion in patients with HCM was 4% (11/277); (2) pericardial pathological and fluid analysis in patients with massive pericardial effusion were characterized by normal pericardial thickening, nonspecific histological findings, and transudative profile with no evidence of infectious or inflammatory process, or autoimmune or inflammatory reactive etiology; and (3) patients with moderate to large pericardial effusion were more likely to have pulmonary hypertension (PH), elevated right atrial pressure, right ventricular hypertrophy and septal hypertrophy.
The normal pericardial sac contains 20–50 ml of pericardial fluid. (1; 2) A pericardial effusion occurs when excess pericardial fluid accumulates in the pericardial sac. (1; 2) Pericardial fluid is normally generated by plasma ultrainfiltrate and drains to the mediastinal, tracheobronchial, peri-esophageal and pleural lymphatic systems.(2) The excessive pericardial fluid is typically caused by (1) increased production of pericardial fluid following infectious or noninfectious inflammatory pericardial process (mostly exudate), (2) impaired reabsorption or drainage of pericardial fluid (transudate) including heart failure or PH, (3) systemic conditions including hypoalbuminemia or hypothyroidism (transudate/hydropericardium), or (4) conditions associated with cardiac and great-vessel injuries (hemopericardium).(2; 3; 12) In our study, the prevalence of moderate to large pericardial effusion in patients with HCM was uncommon (4% of patients with HCM). We found that no inflammatory, infectious, or specified etiologies were identified in these patients. Patients with moderate to large pericardial effusion did have higher estimated right atrial and pulmonary arterial pressures compared to those with no or small pericardial effusion. The pathogenesis of pericardial effusion in PH is currently unclear. Previous studies have reported 15–65% of patients with PH had pericardial effusion.(12; 13; 14) Hinderliter et al. demonstrated that severity of RV dysfunction is associated with pericardial effusion in patients with PH, and among invasive intracardiac and pulmonary hemodynamic indices, mean right atrial pressure correlated best with the size of pericardial effusion.(15) Fröhlich et al. suggested that venous and/or lymphatic congestion may be involved in the etiology of pericardial effusion in heart failure. (14)Further, they proposed that cytokines released in severe heart failure may play a role in the instigation of pericardial effusion by way of systemic inflammatory inducing capillary leakage which increase production of pericardial effusion. Ong et al. reported that 38% of patients with HCM had PH. In our study, 42% of overall patients with HCM and 90% of patients with moderate to large pericardial effusion had PH. Whether pericardial effusion was coincident or associated with HCM remains to be determined. We hypothesize that right heart congestion and/or PH may be involved in the pathophysiology of idiopathic pericardial effusion in patients with HCM. Additionally, we found that patients with moderate to large pericardial effusion had greater septal thickness and were more likely to undergo surgical myectomy. This finding supports the link between the degree of LV wall thickness, diastolic dysfunction, and PH. (16)
To our best knowledge, there has been no systematic review or published data about idiopathic pericardial effusion or tamponade in HCM patients. This study is the first to describe the clinical and pericardial pathological profiles in an HCM cohort. The severity of pericardial effusion along with the severity of right atrial and pulmonary pressures in both patients with pericardial pathological confirmation confirms a similar trend of findings among the entire cohort.
Pericardial biopsy or pericardiocentesis was not performed in all patients with pericardial effusion. Traditionally, patients with HCM with small to moderate pericardial effusion with no clinical tamponade do not require invasive biopsy or pericardiocentesis. Simultaneous invasive pulmonary pressure and vascular resistance measurements were not performed in all patients with pericardial effusion and PH. Doppler interrogation of tricuspid regurgitation to estimate peak pulmonary arterial systolic pressure has been validated and widely accepted and remains the best noninvasive measure available. (9; 10)