Discussion
The present study demonstrated that among STEMI patient population, the presence of moderate to severe TR was associated with significantly lower survival rate compared to patients with mild/no TR. TR was associated with excess mortality even when adjusted for demographic, clinical and other echocardiography parameters.
To our knowledge, this is the first report to date suggesting a possible prognostic implication of TR in STEMI patients.
TR is a common echocardiographic finding 19, but has been disregarded due to the credence that it is a clinically insignificant condi­tion. The clinical impact and outcome of TR are difficult to assess, given its heterogeneity and the association with numerous comorbidities. Hence, management guidelines of TR patients remain ambiguous due to conflicting studies results9,20,21. Pivotal studies suggested that untreated TR is associated with excess mortality and cardiac events7,21. TR had been associated in previous studies with additional cardiovascular outcomes. It has been shown that TR is a common finding in patients with left-sided valvular disease. Significant TR in this circumstance is considered as a late-stage marker and is associated with poor outcome and worse prognosis21–23. Therefore, patients undergoing left valve surgery with severe functional TR (FTR) have a class I indication for concomitant tricuspid valve surgery 24. In patients undergoing transcatheter aortic valve replacement (TAVR) the impact of preoperative significant TR was associated with almost a 2-fold increase in 2-year mortality 23.
TR is also common among patients with chronic heart failure (CHF), due to the pathophysiology of CHF resulting in right ventricular dilatation, and the development of FTR which, consequently, generating further right ventricular dilatation and worsening of TR 25. Studies indicate a strong impact of TR on the clinical outcome in CHF patients, where TR was significantly related to mortality 26.
Recent studies had demonstrated that moderate-severe TR is associated with poor outcome, even in the absence of left ventricular dysfunction or pulmonary hypertension 3,7,9, implying that tricuspid valve repair or replacement may lead to a survival benefit. However, to date, TR patients are rarely referred for isolated surgical tricuspid valve repair, and these are mostly performed during other planned cardiac surgery 5,27,28. In the era where percutaneous repair procedures are on the rise, more research on percutaneous approaches for TR is needed 28.
Limited data exist on the prevalence and prognostic value of significant TR in STEMI patients undergoing PCI. In the setting of acute occlusion of the right coronary artery leading to inferior MI, RV involvement, and concomitant severe TR, tricuspid papillary muscle rupture (PMR) had been reported as a rare complication 29,30.
The present study provides, for the first time, evidence that moderate to severe TR can serve as a possible prognostic marker among STEMI patients. We found that among STEMI patients undergoing primary PCI, with no previous TR, the prevalence for developing moderate to severe TR was 2.7%. These patients suffered more in-hospital complications and worse long-term outcomes. These results imply that in patients developing moderate to severe TR, additional follow up after PCI is needed. Once released from hospital these patients should be followed by a cardiologist, undergo an additional echocardiographic exam to track progression of TR severity and possibly electrocardiogram exam due to a high prevalence of arrythmias. An extra emphasis should be placed on balancing of cardiovascular risk factors for these patients.
Though the reason for higher mortality among STEMI patients with significant TR is yet unclear, we postulate that the presence of TR after STEMI could be a marker of decreased RV function and contractility. It has been shown that the presence of severe TR can be attributed to RV akinesis in the settings of inferior MI or to ischemic impairment of the tricuspid valve 29. Moreover, increasing severity of TR is allied with RV dilation, dysfunction and elevated right atrial pressure, therefore leading to a worse outcomes25. In addition, the association between enlarged RV and increased mortality was demonstrated in previous studies31,32, elucidating that RV function after STEMI has important prognostic implications. Nevertheless, from our understanding the RV function influence on outcomes only partly explains the association between significant TR among STEMI patients and mortality, therefore, additional research is needed in order to illuminate the matter.
We acknowledge several important limitations of our study. This was a single-center retrospective and non-randomized observational study; because of its retrospective nature, the study was subjected to selection bias, and therefore the results point toward association, and not cause and effect.
The study included only patients with first MI who were undergoing primary PCI and with no previous TR. Therefore, the results cannot be generalized to all STEMI patients with TR. The group with moderate to severe TR was small, patients were significantly older, female and with CKD. We attempted to adjust for confounding factors using the multivariate Cox hazard model, however, most of the study population were men, hence the data may not be applicable to female patients. Finally, data were collected retrospectively from echocardiographic reports who were recorded and analyzed by different sonographers. An echocardiographic exam is highly operator dependent which may be subjective, even though it was determined by echocardiography experts.