Results
During the observation period, 3,012 cases of cardiac surgery were performed in our institution. Of these, 238 cases (7.9%) were identified as having poor left ventricular function (LVEF ≤30%), and 75 cases underwent mitral valve surgery without an aortic valve procedure. Three cases of congenitally corrected transposition of the great arteries were excluded from the analysis. Another 3 cases were also excluded because they did not have secondary mitral regurgitation. Three patients underwent mitral valve surgery twice during the observation period. Their first and second surgeries were included for early result analysis, and their second surgeries were excluded from the long-term result analysis. Thus, 69 cases of secondary mitral regurgitation with poor left ventricular function comprised the study group, and their early results were investigated; long-term results were investigated in 66 cases.
The preoperative characteristics of the 69 patients are shown in Table 1. Their mean age was 65.5 years, and 58 patients (84.1%) were male. Preoperative echocardiograms showed poor left ventricular function with a mean LVEF of 21.2% (26 cases <20%), and dilated left ventricular diameters in diastole/systole of 65.1/58.6 mm, respectively.
Peri-operative results are shown in Table 2. In all but one case, which underwent surgery through a right thoracotomy under hypothermic ventricular fibrillation because severe adhesions were anticipated due to previous cardiac surgery, the procedures were performed through a median sternotomy. Mitral valve replacement was performed in 33 cases, and mitral valve plasty was performed in 36 cases. Among the cases of mitral valve plasty, 23 cases underwent subvalvular apparatus procedures. Common concomitant procedures were coronary artery bypass grafting and tricuspid valve plasty (42.0% and 40.6%, respectively). The Maze procedure was performed in 26.1% of cases. Mean operation time was 289.5 min, and mean aortic cross-clamp time was 88.5 min. Transfusion was performed in 50 cases (72.5%).
Two patients required prolonged postoperative ventilation (>72 h), but postoperative morbidity rates were relatively low, except for atrial fibrillation (42%). There were no cases of operative/in-hospital death, and mean duration of hospitalization from operation to discharge was 23.6 days.
Postoperative echocardiograms showed significantly improved mitral regurgitation, from 3.4 (moderate to severe) to 0.75 (less than trivial, p<0.001), although poor left ventricular function remained.
The rate of successful collection of follow-up data was 98.5%, with a mean follow-up of 1,605 days (range, 6–4,525 days). Figure 1 shows the survival curve for all-cause death. Actual 1-, 3-, and 5-year survival rates were 90.5%, 76.5%, and 63.4%, respectively. Figure 2 shows the rate of freedom from re-admission due to heart failure; the 1-, 3-, and 5-year re-admission-free rates were 74.6%, 61.6%, and 55.3%, respectively.
Table 3 shows the results of the risk factor analysis for long-term survival. Patients with clinical frailty scale scores ≥4 had a worse prognosis than patients with clinical frailty scale scores <4 (Figure 3, log-rank p=0.046). The other factors including mitral valve procedure type and etiology did not affect long-term survival significantly in the present study.