Design and patients: Prospective assessment of development of pericardial effusion in 336 patients (163 males) undergoing open heart surgery for congenital heart disease by serial echocardiography on days 5, 7, 14, 21, and 28 postoperatively.

Setting: Tertiary paediatric cardiac centre.

Results: The prevalence of pericardial effusion was 23% (77 of 336). Of the 77 patients who developed effusion, 43 (56%) had moderate to large effusions and 18 (23%) were symptomatic. Patients who had a large amount of effusion were more likely to be symptomatic than those with only a small to moderate amount (47.4% v 15.5%, p = 0.01). The mean (SD) onset of pericardial effusion was 11 (7) days after surgery, with 97% (75 of 77) of cases being diagnosed on or before day 28 after surgery. The prevalence of effusion after Fontan-type procedures (60%, 6 of 10) was significantly higher than that after other types of cardiac surgery: repair of left to right shunts (22.1%, 43 of 195), repair of lesions with right ventricular outflow tract obstruction (22.6%, 19 of 84), arterial switch operation (6.7%, 1 of 15), and miscellaneous procedures (25%, 8 of 32) (p = 0.037). Univariate analyses showed that female patients (p = 0.009) and those receiving warfarin (p = 0.002) had increased risk of postoperative pericardial effusion. A greater pericardial drain output in the first four hours after surgery also tended to be significant (p = 0.056). Multivariate logistic regression similarly identified warfarin treatment (β = 1.73, p = 0.009) and female sex (β for male = −0.63, p = 0.037) as significant determinants.

The following data were collected: demographic data, cardiac diagnoses, types of surgery performed, pericardial drain output within the first 48 hours of operation, reoperation for haemostasis, timing of pericardial drain removal, postoperative use of anticoagulant and diuretics, and occurrence of pericardial effusion. In patients who developed pericardial effusion, the timing of onset and duration of effusion, their clinical presentation, and the treatments received were noted.

Seventy seven of the 336 (23%) patients developed pericardial effusion postoperatively. The amount of effusion was small in 34, moderate in 24, and large in 19 patients. The effusion was already circumferential in 55 of 77 (71%) at first presentation. Its onset was at 11 (7) days after surgery. Overall, the diagnosis was made on or before day 14 and day 28 after surgery in 79% (61 of 77) and 97% (75 of 77) of patients who developed effusion, respectively. Importantly, 12% (4 of 34), 25% (6 of 24), and 32% (6 of 19) of patients with, respectively, small, moderate, and large amounts of effusion presented beyond the second week after operation (fig 1​1).

Clinical symptoms or signs were present in only 18 (23%) patients. These were fever in 10 patients, gastrointestinal disturbance such as vomiting or abdominal discomfort in two, signs of fluid retention in three, irritability in two, and evidence of tamponade in one. Patients who had a large amount of effusion were more likely to be symptomatic than those with only a small to moderate amount (47.4% v 15.5%, p = 0.01). Likewise, patients with circumferential effusion tended to be more symptomatic than those with loculated effusion (29.7% v 9.0%, p = 0.077).

Conservative treatment with fluid restriction and diuretic treatment in 44 (57%) patients with a small to moderate amount of effusion resulted in resolution in all of these patients. Anti-inflammatory medications were started in 21 patients (27%) who, albeit asymptomatic, had a moderate amount of effusion with evidence of progression. Aspirin was prescribed to seven patients and steroid was given to 14. Eighteen patients responded, while three eventually required pericardiocentesis. Pericardiocentesis, either by a surgical or a percutaneous approach, as the initial treatment was performed in 12 (16%) symptomatic patients with a large amount of effusion. The median duration for effusion to resolve completely was eight days (range 1–394 days), with complete resolution achieved in 83% (64 of 77) of patients within four weeks of diagnosis.

Symptoms were present in only slightly more than a fifth of our patients who developed pericardial effusion and these symptoms were mostly non-specific. This is in contrast to the findings of Clapp and colleagues,⁵ who reported that 16 of 21 children with postoperative effusion developed clinical evidence of postpericardiotomy syndrome. The apparent discrepancy may be because serial echocardiographic assessment allows for early diagnosis and institution of anti-inflammatory treatment before appearance of symptoms. Nonetheless, the presence of symptoms may have important implications, as symptomatic patients were more likely to have a more severe degree of pericardial effusion and hence to be at risk of haemodynamic compromise in the absence of interventions. Close monitoring and early institution of anti-inflammatory treatment are therefore warranted in symptomatic patients.

Data on the efficacy of anti-inflammatory treatment for postpericardiotomy syndrome in children are, however, limited. While aspirin has been widely used, the reports were largely anecdotal⁶ and, to date, there have been no controlled trials on the efficacy of non-steroidal anti-inflammatory agents. Prophylactic use of aspirin, on the other hand, has been shown to have no significant benefit in the prevention of postoperative pericardial effusion in children.⁶ In a double blind placebo controlled trial of steroid in a small cohort of children with postpericardiotomy syndrome, Wilson and colleagues⁹ have shown that steroid hastens the remission in the majority, although two of their 12 patients had a further increase in the amount of effusion despite steroid administration. Likewise, only three of our 21 (14%) patients failed to respond to anti-inflammatory treatment. A trial of anti-inflammatory treatment is hence justified in patients with moderate and increasing amounts of pericardial effusion before contemplation of the more invasive pericardiocentesis.

To our knowledge, this is the first study to examine risk factors predisposing to development of pericardial effusion after open heart surgery for congenital heart disease. While Prabhu and colleagues⁷ suggested a higher incidence of effusion incidence after Ross procedure, the number of patients included in their studied was too small to be significant. We found that pericardial effusion occurred more commonly after Fontan-type procedures. On the other hand, infants, mostly boys, undergoing arterial switch operation for transposition of the great arteries had the lowest incidence. Similar to the findings of Stevenson and colleagues,³ a greater pericardial drain output early postoperation tended to be associated with an increased likelihood of pericardial effusion. It has been proposed that the increased amount of blood accumulated may irritate the pericardium through a hydrophilic action.^10,11 Multivariate analysis showed that postoperative warfarin is a significant risk factor after adjustment of other variables. This finding corroborates those reported in the adult literature.^2,12,13 Warfarin given routinely after Fontan-type procedures probably explains in part the observed higher incidence of pericardial effusion after this operation. The findings that more of our patients taking warfarin were female and that most undergoing arterial switch operation were male may explain the significance of sex in determining the occurrence of pericardial effusion in this cohort. Interestingly, however, female adult patients have been shown to be at higher risk for development of early postoperative cardiac tamponade after open heart surgery in a recent study.¹⁴ While the explanation remains unclear, female sex may indeed be an independent risk factor, even after adjustment for confounding influence.