In the present study, we evaluated long-term mortality and morbidity between 2 groups of TV repair and TV replacement over a median of 8 years. We found that mortality was higher (32.6%) in the replacement group than in the repair group (25.9%); nevertheless, this finding should be interpreted in light of the fact that our study sample was small. Consistent with our results, previous studies have also concluded that TV replacement is associated with considerably high mortality compared with TV repair [10, 11]. Guenther et al. evaluated 416 patients over a median of 5.9 years and found that 30-day mortality after TV repair was 13.9% (43/310) opposed to 33% (35/106) after TV replacement (P = 0.0001) . In line with it, multiple studies have reported that the in-hospital mortality after TV replacement ranges between 14.5 and 48% . It is crucial for surgeons to select their patients cautiously to reduce the rate of mortality after TV replacement. Topilsky et al. also believed that candidating the right patient for TV replacement might lower the rate of mortality .
There are other independent predictors of mortality after isolated TV surgeries such as the New York Heart Association (NYHA) functional class [13, 14] and RV function parameters [13, 15]. These variables should be considered in the decision for the medical or surgical treatment of TV disease. It is apparent that both of them play central roles in both preoperative clinical status and postoperative outcomes [4, 16,17,18]. As is shown in our results, postoperative RV dysfunction and the NYHA functional class improved in both groups by comparison with the preoperative measurements, and we detected no correlation between either TAPSE or the NYHA functional class and mortality. Bevan et al.  and Buzzatti et al.  posited that RV dysfunction played an important role in preoperative characteristics such as ascites and also postoperative outcomes. Topilsky et al. reported that a preoperative NYHA functional class of 4 was associated with a higher chance of mortality . In a propensity score study, Calafiore et al. showed that functional benefits were present with moderate-to-severe functional tricuspid regurgitation subjected to mitral surgery if the TV was concomitantly diseased .
There are different causes of readmission after TV surgery irrespective of the type of Surgery (repair vs. replacement) including congestive heart failure (CHF), arrhythmia, respiratory and surgical complications, cerebrovascular arrest, infections and acute kidney injury . In our study, only repair group experienced readmission due to CHF, renal failure, transient ischemic attack and valve dysfunction. The patients in replacement group had higher rate of mortality.
PAP is associated with worse outcomes in patients undergoing isolated tricuspid surgery . Likewise, we observed a drop in postoperative PAP in both groups. Preoperative PAP had a significant correlation with the length of stay in the ICU, and it was strongly higher in the RV replacement group. Buzzatti et al. observed a relationship between the presence of a higher PAP leading to poor outcomes and mortality in their patients undergoing TV replacement. Similarly, Mangoni et al. concluded that one of the factors associated with poor outcomes was a high PAP . We believe that the high preoperative PAP in our replacement group might have resulted in the higher rate of mortality in this group.
We have previously demonstrated that redo surgery is a major determinant of early and long-term mortality [3, 5, 23]. In this study, we also observed that none of the patients in the TV repair group had redo surgery, whereas 14% of the TV replacement group patients were scheduled for redo surgery, which can cause a lower rate of survival in a longer follow-up period. Great precaution may be needed when performing redo surgery in patients with isolated TV disease due to the high recurrence of tricuspid regurgitation after redo surgery . Our results also revealed that only 3.5% of the entire study population (n = 7, 14.8% in the replacement group) needed redo surgery, which is lower than the rates in previous studies [24,25,26,27].
Rheumatic etiology is one of the most important predictors of a poor outcome. This is understandable because rheumatic disease is a destructive and ongoing process causing extensive and sometimes irreparable damage not only to the TV but also to the myocardium . We found that the incidence of rheumatic valve disease was higher in the TV replacement group than in the TV repair group (76.6% vs 20.0%). Moreover, our results revealed a higher mortality rate in the replacement group. Previous studies have also reported that rheumatic heart disease is correlated with mortality in patients after TV surgery [6, 28]. It can be referred from our results that rheumatic valve disease might have caused the high mortality in our TV replacement group compared with our TV repair group.
We had 1 patient with hemorrhagic stroke in the TV repair group who had a history of atrial fibrillation and was on vitamin K antagonist regimen. Postoperative neurological impairment after cardiac surgery is a serious complication. In a recent study, Raffa et al. evaluated the incidence of different types of stroke after a variety of cardiac surgeries and found that the incidence of hemorrhagic stroke was relatively low compared with ischemic stroke and it occurred in patients undergoing concomitant cardiac surgeries (TV surgery concomitant with coronary artery bypass graft or aortic valve surgery) .
Based on the past medical history of our patients, most of the ASD cases were in the TV repair group (79.5% vs 17.0%) rather than in the TV replacement group. ASD closure surgery is one of the concomitant procedures in TV surgery .
In our study, we found that ICU hours and the length of hospital stay were significantly higher in the replacement group, even though this group comprised fewer patients than did the repair group. Alqahtani et al. evaluated the outcomes of surgical treatment in 45,477 patients, 15% of whom only had isolated tricuspid surgery. They found that TV surgery was associated with a long duration of hospitalization, which is reported to be higher in other types of valve surgeries . In another study, TV replacement and repair propensity-matched cohorts had similar ICU lengths of stay, but the replacement group had a significantly longer hospital length of stay .
It is believed that diabetes, the level of creatinine, and the white blood cell count play important roles in mortality insofar as they can increase the chance of postoperative infection and mortality afterward. Among the patients who died in the present study, 3 patients had leukocytosis due to urinary tract infection, which caused septicemia and led to death. This finding is concordant with the results reported by Fowler et al., who reported a higher rate of complications such as longer lengths of hospital stay and higher rates of mortality in patients with major infections after cardiac surgery .
In the current study, we had 2 patients with endocarditis as the etiology of repair surgery; both of them expired. (The power of the study made it impossible to evaluate the statistical difference.) Nonetheless, Singh et al. reported that the organic pathology of the valve could significantly increase the occurrence of mortality in TV replacement as opposed to TV repair irrespective of the type of implant. Pfannmüller et al. concluded that mortality could be higher if surgery was performed under urgent conditions due to endocarditis or other cardiac diseases . The discrepancy between the results of the present study and those previously reported might be due to our small sample size. We, thus, recommend further evaluations on larger sample volumes.
We did not calculate the predictive score of mortality (eg, the EuroSCORE), nor did we assess the reoccurrence rate of postoperative regurgitation. In addition, the study population was relatively small and we were unable to perform a long-termfollow-up on our patients. Moreover, there were differences in the some of the baseline characteristics of the study population. Another salient weakness of our study is our failure to record information concerning the presence of ascites and anasarca, which have major associations with mortality. It must be mentioned, due to low percentage of mortality, evaluating the predictors of the mortality in either groups, was not the aim of present study.