Pericardial involvement in systemic autoimmune diseases is thought to be related to the underlying systemic inflammation and may relate to a sudden flare or a gradual progression of the disease process. It is understood to be present in many rheumatologic diseases including systemic lupus erythematosus (SLE) and SSc, with more than 60% of cases reported to have pericardial involvement on histopathology of autopsy cases [10]. In patients with SLE, development of pleuritis, and size of pericardial effusions have been seen as predictors for development of tamponade, and high dose immunosuppressive treatment has been demonstrated to reduce need for surgical intervention [11].
The present study includes the largest cohort of hospitalized patients with SSc, from the NIS database from 2002 till 2019, with pericardial effusion noted in 3.1% of overall hospital admissions. The incidence of pericardial effusions in our study is lower than the one described in a single center trial which was at 6.9% of hospitalizations though this may relate to being a single tertiary referral center [6]. This is also likely to be an underestimate of true prevalence of pericardial effusions since echocardiograms may not get routinely performed in an inpatient basis and the data may not include respective ICD codes for pericardial effusions.
The patient population of this study were predominantly Caucasian females which is consistent with the overall demographics of SSc patients. Up to one-fifth of the hospitalized SSc patients had significant cardiac comorbidities such as congestive heart failure (25.1%) and pulmonary circulatory disease (23.6%), while pericardial effusion was clinically noted in 3.1% of this population of hospitalized patients, it is clearly lower than the 62–77% noted in autopsy series [9, 12], however it is understood that many patients may have only subclinical or not clinically apparent pericardial disease.
Compared to SSc patients with cardiac tamponade, SSc patients with a pericardial effusion were significantly more likely to have pulmonary circulatory disease and congestive heart failure. This may relate to the commonly subacute nature of SSc-PH which then leads to heart failure due to the progression of the underlying pulmonary hypertension. The association between PH and pericardial effusions has been clearly described in the general population as well as SSc patients. Unfortunately, the NIS database does not allow us to clearly identify which PH WHO classification group each of these patients was, though typically most SSc-PH patients are WHO Group 1 or Group 3, both typically subacute and slowly progressive.
The presence of diabetes and hypothyroidism was also more significantly present in patients with a pericardial effusion rather than cardiac tamponade, again the assumption is made that these are chronic slowly progressive illnesses and cardiac tamponade would more likely be an acute process. In the general population pericardial effusions have been described with hypothyroidism but not as commonly in association with diabetes. Similarly, the proportion of patients with end stage renal disease was also significantly higher in patients with pericardial effusion as compared to tamponade. Again, the NIS database does not allow for us to understand if these patients had SSc related kidney disease such as scleroderma renal crisis, or other forms of kidney disease.
Patients with cardiac tamponade on the other hand, were significantly more likely to have had a history of a prior coronary artery bypass graft (CABG), peripheral arterial disease or atrial fibrillation. Some studies in the general population have suggested that a previous CABG protects against progression of a pericardial effusion to tamponade because of the presence of pericardial adhesions, though in this study it appears that this is not the case in SSc patients. The proportion of patients having coronary artery disease was also higher in patients with cardiac tamponade compared to SSc patients with pericardial effusion alone, although this was not statistically significant.
There are no specific treatment guidelines regarding treatment of pericardial effusions or tamponade in SSc patients. It can be assumed that patients with cardiac tamponade needed more emergent drainage or surgical intervention. We do not have information on treatment options or fluid characteristics on the NIS database, although prior studies have shown pericardial fluid to be exudative in nature [7].
Prior studies have showed significant burden of atrial fibrillation (AF) in rheumatic diseases and mortality, length of stay and hospitalization costs were also noted to be higher in patients with AF than patients without AF [13]. Atrial fibrillation in SSc can relate to causes such as seen in the general population which includes CAD, while in SSc patients there is a strong association with myocardial fibrosis. Our study also showed presence of AF in 16.5% of SSc patients with cardiac effusion and in 19% of SSc patients with cardiac tamponade, which is higher than the general prevalence of AF in SSc patients. Patients with AF were also significantly more likely to have pericardial tamponade than pericardial effusion, although it is difficult to establish direct causation or pathophysiologic relation with cardiac tamponade from this study.
There are some limitations of our study due to the nature of the data collected from the NIS. A major limitation is the lack of specific disease related data, including disease duration, disease subset (limited cutaneous SSc or diffuse cutaneous SSc), as well specific antibodies profile of patients or overlap with other autoimmune diseases. We do not have data on medications or laboratory values on the NIS database. A definite causal relationship of pericardial effusion or tamponade with the reported comorbidities or mortality cannot be established. In addition, pericardial effusion or tamponade being the immediate cause of death could not be ascertained. It would also be interesting to look at treatment including medical or surgical in patients with pericardial effusions and tamponade and its impact on patient outcomes.