Comment
This was a single-center, retrospective report of the early and long-term results of consecutive cases of mitral valve surgery for secondary mitral valve regurgitation with poor left ventricular function.
The early results of this study were good in terms of surgical mortality and morbidity. Our operative strategy was devised to reduce aortic cross-clamp time in poor left ventricular function. Concomitant coronary bypass was performed in on-pump beating fashion as much as possible, and mitral valve replacement was chosen for critically ill patients.10 With these modifications, more patients could tolerate open heart surgery than we expected even with reduced cardiac function.
Since the results seem to imply that poor left ventricular function itself might not be a contraindication for open cardiac surgery, operative indications should be considered very carefully. In the present study, 26 cases (37.7%) had LVEF ≤20%, but no patient had LVEF <10%. Preoperative mean left ventricular diameter was not extremely large, being 65.1/58.6 mm in diastole/systole. The cases with extremely dilated or more reduced cardiac function may not be able to tolerate open heart mitral valve surgery. For such patients, a left ventricular assist device or heart transplantation may be indicated.
Since surgical stress or trauma is much greater than that of a catheter procedure, we should carefully choose which modality to use to restore secondary mitral regurgitation with poor left ventricular function, especially in very ill patients. For critical patients with poor left ventricular function, percutaneous treatment might be a better option even if it is less effective than surgical treatment1.
Although there was no postoperative mortality, and the morbidity rate was low, except for paroxysmal atrial fibrillation, postoperative hospitalization was long, more than 3 weeks. This is probably because patients with poor cardiac function have a slow recovery and require a longer time to optimize their medication regimens that include angiotensin-converting enzyme inhibitors, angiotensin receptor/neprilysin inhibitors, mineralocorticoid receptor antagonists, beta-blockers, or sodium-glucose co-transporter 2 inhibitors15.
Long-term survival in the present study was acceptable compared to the previous reports, in which the long-term results for secondary mitral valve regurgitation were dismal when only pharmacotherapy was provided.16,17 However, re-admission-free rates were low, 61.6% at 3 years and 55.3% at 5 years. This may imply that poor left ventricular function remains even after open mitral valve surgery with good control of mitral regurgitation. Multidisciplinary therapy should be provided to these subsets, including pharmacotherapy, diet, rehabilitation, and cardiac resynchronization therapy, even after the surgery.
Concerning risk factors for long-term survival, the clinical frailty scale score was the only predictor of long-term mortality in the present study. Th clinical frailty scale is a simple method to semi-quantitatively assess patient frailty.18 It has been reported that it can predict late mortality in certain cases.19,20 Since the present study showed worse long-term survival in patients with high clinical frailty scale scores, the operative indications need to be considered carefully in such ill patients, because surgical stress or trauma could make the patients’ frailty worse. For patients with a high clinical frailty scale score, percutaneous transcatheter mitral valve edge-to-edge repair might be a better option, because it is far less invasive than open heart surgery.
The present study had several limitations. First was the retrospective design of the study. Once we selected open heart surgery for the patients, huge selection bias existed.
Second, the number of patients was small, and data in the present study represent our clinical experience with a consecutive series of surgical correction for mitral regurgitation with poor left ventricular function. However, the present results reflect real-world clinical practice and imply that open heart surgery could be appropriate for selected patients even with poor left ventricular function.
The last limitation was that, because of the retrospective nature of the investigation, this study did not have a control group. Whether surgical correction of secondary mitral regurgitation provides greater benefit than other therapeutic options over the long-term is unknown. However, considering that several articles have reported a poor prognosis for patients with secondary mitral regurgitation and our good operative results, we feel encouraged to provide open mitral valve surgery if the patient can tolerate the surgery.