Patients
The present retrospective study included 219 patients who underwent isolated aortic valve replacement for chronic AR from March 2004 to December 2018 at the heart center, First Hospital of Tsinghua University, China. Patients were excluded if they were undergoing previous aortic surgery, concomitant coronary artery bypass grafting, mitral valve repair or replacement, congenital aortic stenosis, acute infective endocarditis, aortic dissection. Perioperative death was defined as death within 30 days after AVR or in-hospital death. The left ventricular reverse remodeling (LVRR) was defined as an increase in LVEF at least 10 points or a follow-up LVEF ≥ 50%, and a decrease in the indexed left ventricular end-diastolic diameter of at least 10%, or an indexed left ventricular end-diastolic diameter ≤ 33 mm/m2, and LVRR was calculated based on baseline at 6 months to 1-year follow-up echocardiograms [8]. The severe LV dilatation was defined as left ventricle end-diastolic diameter (LVEDD) > 65 mm, preoperative left ventricle systolic dysfunction was defined as ejection fraction (EF) < 50% [3]. Based on the LVRR definition, these patients were divided into LV reverse remodeling group (remodeling group) and no reverse remodeling group (no remodeling group). The baseline clinical information and echocardiographic variables were retrieved from medical records. The study was approved by the ethics board of the First Hospital of Tsinghua University. Because clinical data was obtained in routine clinical practice, the informed consent from each patient was waived in this retrospective study.
Surgical procedures
All patients have been treated with cardiotonic, diuretics, and other medications for heart failure before the operation. Hypothermic cardiopulmonary bypass and intermittent antegrade direct cold cardioplegia were routinely for the surgical procedure. There were 66 patients who underwent mechanical valve replacement, and 3 patients who underwent bioprosthetic valve replacement.
Echocardiographic examination and parameters
Transthoracic echocardiography was performed before AVR, and at 6 months after AVR, using a commercially available ultrasound system (vivid7, E9) equipped with 3.5-MHz or M5S transducers. Two-dimensional and Doppler’s data were acquired at the parasternal, apical, subcostal, and supra-sternal views according to the standards of current recommendation. LV end-diastolic and LV end-systolic volumes (LVEDV and LVESV) were quantified in the apical two- and four-chamber views using Simpson’s biplane method, and LVEF was calculated according to the American Society of Echocardiography recommendations. Aortic valve function was evaluated using color, continuous- and pulsed-wave Doppler, AR was grade as 0 (absent), 1 (mild), 2 (mild-moderate), 3 (moderate-severe), or (severe) [9].
Follow-Up
The major adverse cardiac events (MACE) included cardio-related death, hospitalization due to heart failure, and lethal arrhythmia. The follow-up data were obtained from our outpatients’ clinic records or by correspondence with referring physicians using telephone and subsequent hospitalization. The mean follow-up period was 47.29 months (range 6 to 173 months).
Statistical analysis
Continuous variables were reported as mean ± standard deviation. The categorical variables were presented as numbers or percentages and compared using the Chi-square test or Fisher’s exact test. Continuous variables were compared using student’s t-test. The cumulative incidence of clinical outcomes after AVR was estimated using the Kaplan–Meier method. Multi-variable independent factors were performed by using stepwise regression. Statistical significance was defined as a 2-tailed p value < 0.05. All statistical analysis was performed with R version 3.5.3. (R Core Team (2019). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/.)