Materials and Methods
Between November 2008 and April 2021, all cases of cardiac surgery performed at Nagoya Heart Center were screened, and patients with preoperative echocardiographic LVEF ≤30% were identified. Of these, cases that underwent mitral valve surgery due to secondary mitral valve regurgitation comprised the study group. Cases with concomitant aortic valve surgery were excluded.
On echocardiographic evaluations, cardiac chamber size was measured using the standard M-mode method, and LVEF was calculated using the modified Simpson’s method. Valve regurgitation was assessed using color-flow Doppler as “trivial”, “mild”, “moderate”, or “severe”. Postoperative transthoracic echocardiographic evaluation was performed on each patient before discharge, usually on postoperative day 7.
Chronic obstructive pulmonary disease was defined as percentage predicted forced expiratory volume in 1.0 s <75%, partial pressure of oxygen in arterial blood <60 mmHg, or provision of medical therapy. The definition of liver dysfunction was total bilirubin ≥1.5 mg/dl or liver enzymes (aspartate aminotransferase or alanine aminotransaminase) ≥100 U/l. Clinical data were gathered from medical records, operative records, and the in-hospital surgical database.
Long-term results were assessed by direct contact with the patients or telephone interviews with the patients, their families, or their local doctors. Survival was assessed between January and April 2021.
The primary endpoints for the early results were peri-operative mortality and morbidity, and those for the long-term results were mortality and hospitalization due to heart failure. As the secondary endpoints, risk factors for mortality in the long-term were examined. Patients were divided into two groups, and their long-term results were compared. The groups were stratified as follows: sex, ischemic etiology, ejection fraction <20%, clinical frailty scale score ≥4, presence of hypertension, diabetes mellitus, hyperlipidemia, preoperative atrial fibrillation, peripheral artery disease, hemodialysis, history of smoking, percutaneous coronary intervention, myocardial infarction, main procedural type (mitral valve replacement or plasty), and concomitant procedures, including coronary artery bypass grafting, tricuspid valve plasty, Maze procedure, and left ventricular restoration surgery.
Data were analyzed using SPSS version 22 statistical software (SPSS, Chicago, IL). Results are expressed as means ± standard deviation. Continuous data were analyzed using the Mann-Whitney U test ort- test as appropriate. Categorical data were analyzed using the χ2 test. Survival analysis was performed using the Kaplan-Meier method and the log-rank test. Results with values of p<0.05 were considered significant.