Long-term results of radical pericardiectomy for constrictive pericarditis in Korean population

Constrictive pericarditis has a thickened, inflamed, adherent, or calcified pericardium that limits diastolic ventricular filling of the heart [1]. Pericardiectomy restores them and postoperative clinical outcomes and prognostic factors have been reported [2‐9].

A wider surface than we think exists posterior to the phrenic nerve (Fig. 1) [10]. However, pericardiectomy posterior to the phrenic nerve is not easy because it could make vital signs unstable if a heart is bent anteriorly. Therefore, it is reasonable to assume the extent of pericardiectomy would make better outcomes. Many papers have suggested the prognosis would improve as more pericardium is resected, but only Chowdhury et al. [3] have shown this by comparative analyses according to the extent of pericardiectomy.

This study is one of only a few which compare long-term results between conventional and radical pericardiectomies. The main findings were as follows: (1) The survival rate was higher in the radical group. (2) Radical pericardiectomy was one of the factors associated with survival. (3) There was more improvement of certain echocardiographic parameters in the radical group as time passed.

Radical pericardiectomy was one of several factors associated with survival. Gongora et al. [12] previously showed pericardiectomy posterior to the phrenic nerves was a predictor of long-term survival. Chowdhury et al. [3] also confirmed conventional pericardiectomy is a risk factor for late mortality. The present study confirmed those previous reports. There are various kinds of surgical techniques of pericardiectomies according to the extent of pericardiectomy, surgical approach, or use of CPB. CPB is not used when thoracotomy is done [13, 14], but it is used when sternotomy is done [8, 15‐17]. Although left thoracotomy enables pericardiectomy posterior to the left phrenic nerve without CPB, it is difficult to remove the pericardium around the right side of the heart [14, 18]. Chowdhury et al. [3] stated CPB is unnecessary even when total pericardiectomy is planned via a sternotomy, but total pericardiectomy by their definition is pericardiectomy anterior to the phrenic nerves. Therefore, in our opinion, sternotomy with CPB is inevitable if radical pericardiectomy is planned. Some authors have reported CPB is a risk factor for early mortality [5, 9], but the early mortality rate in our study was 1.3% (1/75) among the patients who underwent CPB. Bleeding risk is one of the complications of CPB especially if a patient has liver cirrhosis. In our results, the MELD score was correlated with the amount of postoperative chest tube drainage. (P < 0.001, Correlation Coefficient = .470) However, the correlation between CPB time and the amount of postoperative chest tube drainage was not significantly correlated. (P = .222, Correlation Coefficient = .130). On the other hand, there are several advantages of CPB. It helps to identify an appropriate dissection plane by emptying the ventricular cavities and helps to treat inadvertent cardiac injury [3, 9, 15, 16]. It also enables repair of the tricuspid valve without any hesitation [12]. Furthermore, Cho et al. [15] stated CPB can control preoperative volume overload.

Etiology, especially postradiative pericarditis has been known to be a predictor of late outcomes. Ling et al. [7] concluded radiation exposure was predictive of late mortality and other papers reported similar results [2, 4, 5, 12, 19, 20]. However, it was not found to be a factor associated with late mortality in our study. Patients who had postradiative pericarditis (5.6%) were too few to reach a meaningful conclusion [6].

Preoperative CVP has been known to be an important factor associated with survival. Elevated right atrial pressure and right ventricular end-diastolic pressure more than 20 mmHg were previously identified as risk factors for mortality [3, 8]. The preoperative CVP in our study was higher than normal range but under 20 mmHg. Either preoperative or immediate postoperative CVP was not a factor associated with survival. Preoperative CVP in the conventional group was higher than that in the radical group statistically (18.5 vs. 16.2 mmHg). One may think the mortality rate was higher in the conventional group because an elevated CVP indicates poor conditions; however, other clinical and echocardiographic findings were not different between groups, and a Cox proportional hazard model analyzes the data after removal of intergroup differences. We also wonder if the statistical difference between 18.5 and 16.2 mmHg is still significant in a clinical situation. The most (70%) preoperative CVP which were measured in the operating room under general anesthesia could be a limitation of our data because they can be influenced by mechanical ventilation, full sedation, or volume status at the moment.

The number of early complications was associated with later mortality in the univariate analysis but not in the multivariate analysis. It rather correlated with the period of hospitalization (P = .002, ρ = .329). Postoperative LCOS was more related with early mortality than late mortality. It was comparable to the previous reports in which postoperative LCOS affected early survival rather than late one [21, 22].

TR worsened after the operation in both groups, but it was aggravated more in the conventional group in the last echocardiography. Several cases of worsening TR or right ventricular dysfunction after pericardiectomy have been reported [23‐25]. Mantri et al. concluded if an adequate pericardiectomy is done at an earlier stage, the regurgitations will regress [26]. Gongora et al. [12] stated TR is relieved in only 29% of patients after pericardiectomy, and they recommended repair of the tricuspid valve because TR of more than a moderate grade increases late mortality. We experienced a case of tricuspid valve repair because TR was aggravated six years after pericardiectomy alone. Therefore, we expect postoperative TR can be prevented if a surgeon repairs the valve more actively. The preoperative grade of TR was also verified as a factor associated with late mortality in our study. Nevertheless we should be careful not to interpret it to mean tricuspid valve repair would improve late survival. However we may make a hypothesis that postoperative aggravation of TR could be a sign of another pathology which was masked by constrictive pericarditis or made by inadequate pericardiectomy. Then the aggravated TR after pericardiectomy in our study could be explained if the hypothesis is demonstrated someday.

There were some limitations to this study. First, the small number of patients and retrospective study design did not allow us to draw any definite conclusions. The survival rate of radiation-induced constrictive pericarditis is known to be low [20] but it was not in this study. We think the ratio of radiation-induced pericarditis was too low in Korean patient population. The other Korean authors also reported such unique Korean environment could be a limitation in their article [6]. Second, since a multivariate analysis is most robust when it involves at least 10 events for each variable assessed, it seems likely our multivariate analyses were over-fitted. So a larger number of patients and a larger number of adverse outcomes are needed to perform these analyses later. Third, clinical implication of this study remains unclear yet although the findings of this study were reasonable. So prospective randomized data are necessary to establish the clinical implication.

Radical pericardiectomy led to greater improvement in right ventricular systolic pressure and lesser deterioration of TR with the passage of time than did the conventional procedure. Conventional pericardiectomy and preoperative higher grade TR were associated with long-term mortality.