This was a single-center, retrospective observational study conducted at Nihonkai General Hospital, and involved 471 unique patients from December 2005 to December 2017 who underwent isolated or combined CABG. Of those, 393 patients who underwent isolated CABG were included in the analysis. The study’s retrospective was approved by the ethics committee of Nihonkai General Hospital, and conformed to the Declaration of Helsinki. The requirement for informed consent was waived by Ethics committee of Nihonkai General Hospital based on the study’s retrospective analysis of patient data. Prior to all CABGs, a multidisciplinary team of cardiothoracic surgeons, cardiologists, physical therapists, nurses, and medical technicians met to discuss the indication for preoperative rehabilitation and preoperative conditioning. The purpose of this study was to evaluate whether a physiotherapy treatment regimen initiated in the preoperative phase could prevent postoperative respiratory and musculoskeletal complications and influence the prognosis after cardiac surgery. Inclusion criteria adopted to enroll the patients in this study were ACS, a New York Heart Association (NYHA) class I, II or III, good exercise tolerance before in-hospital admission, and chance to benefit from respiratory and motor treatment. The inclusion criteria for patients indicated for the preoperative rehabilitation program were similar to the guidelines developed by the Japanese Society of Cardiology [7]: a mean blood pressure greater than 65 mmHg, a sustained pulse greater than 50 and less than 120, and the absence of the appearance of new severe arrhythmias and ECG changes suggestive of myocardial ischemia. Patients were eligible for treatment if their respiratory rate was less than 30 breaths/min, SpO2 was greater than 92%, and FiO2 was less than 0.6. The following conditions were also considered for eligibility for the rehabilitation program: no worsening of subjective symptoms within the past 3 days, no weight gain of more than 2 kg within the past week, and no NYHA functional class IV heart failure (Fig. 1). The evaluation of exercise tolerance prior to the start of the program began with an interview to ascertain psychological status, cognitive ability, exercise capacity, and NYHA cardiac function classification. If exercise testing is possible, cardiopulmonary exercise (CPX) testing should be performed and evaluated. If it is difficult to perform exercise testing, a rating of perceived exertion (RPE) should be evaluated based on the Borg index [8] and talk test, using a heart rate of less than 120 bpm as a guide. A Borg index of 11 to 13 was used as a guide to determine RPE.
The cardiac rehabilitation program is a comprehensive program that includes nutritional guidance, psychological counseling, and management of coronary risk factors (blood pressure, lipids, diabetes, smoking, etc.) in addition to exercise therapy. Rehabilitation is based on an acute weaning program, gradually increasing in intensity from head-up in bed, end-sitting, and standing at the bedside, with the goal of walking to the toilet and walking freely in the ward [9]. Patients who complete the weaning program without progression of their condition are prepared for cardiac surgery with low-intensity aerobic exercise and resistance training.
The primary outcome was the occurrence of postoperative major adverse cardiac and cerebrovascular events (MACCE), which included death, acute myocardial infarction, cerebrovascular event, or further revascularization by percutaneous coronary intervention or CABG. Intraoperative findings, such as the amount of inotropic agent used during surgery, the presence or absence of mechanical circulatory support, and difficulty in weaning from cardio-pulmonary bypass, were evaluated as secondary outcomes, as were the number of days until extubation, postoperative complications, and postoperative hospital stay. Postoperative atrial fibrillation, mediastinitis, intubation time longer than 72 hours, intensive care unit (ICU) stay longer than 7 days, and postoperative length of stay longer than 30 days were also included. The occurrence of any short runs of atrial fibrillation more than 30 seconds during the hospital stay was considered to represent an occurrence of atrial fibrillation. A neurologic event was defined as an endpoint when symptoms appeared and could be corroborated using computed tomography (CT) and magnetic resonance imaging (MRI). The final diagnosis was performed by a neurosurgeon, and it was considered a neurologic event if diagnosed. If there were no visual findings, a transient ischemic attack was not included. These definitions are similar to those presented previously[10].
As previously reported, our institution performs prophylactic intra-aortic balloon pump (IABP) therapy in all high-risk patients [10]. An IABP was inserted in the catheterization lab the day prior to CABG, with continuous intraprocedural IABP therapy and use postoperatively as clinically indicated; patients were monitored in the ICU pre- and post-operatively.
In addition, we treated dental conditions, glycemic imbalances, and co-morbid treatable diseases, such as carotid artery stenosis, prior to cardiac surgery. A cardiopulmonary bypass (CPB) circuit was used when considered necessary at a preoperative conference. Its use was suggested mainly by preoperative characteristics (e.g., a large left ventricle, low cardiac function), and on-pump CABG was scheduled based on comprehensive risk assessment, such as the location or quality of the target vessels and technical challenges. If it was judged that a complete revascularization was feasible on the beating heart, off-pump CABG (OPCAB) was scheduled. Conversion to CPB was considered if there was any evidence of hemodynamic instability concerns, such as ventricular arrhythmia, hypotension (systolic pressure ≤ 80 mmHg), and cardiac arrest during the OPCAB procedure. OPCAB was performed after a median sternotomy. The heart was displaced using a posterior pericardial stitch, gauze and a tissue stabilizer (Octopus; Medtronic Corporation, Minneapolis, Minn., USA), along with body position changes and gravity support (Trendelenburg, right and left table rotations). A CO2 blower/NaCl misting device was used in situations where a bloodless field was not achieved after proximal target vessel occlusion. On-pump isolated CABG was performed with almost the same technique. All on-pump CABG was carried out in the beating condition. Grafting was always performed from the left internal mammary artery to the left anterior descending coronary artery, followed by grafting of the circumflex coronary artery and the right coronary artery using a radial artery or a saphenous vein. The bilateral internal mammary arteries were used in the non-touch aorta technique if ascending aortic sclerosis or calcification was assessed based on preoperative findings from imaging examinations and intra-operative palpation. The quality of the anastomosis was assessed after grafting with the use of a transit-time flow probe (Butterfly Flowmeter; Medistim, Oslo, Norway).
Statistical analysis
Continuous variables were expressed as the mean and standard deviation or the median and interquartile range, and categorical variables were expressed as frequencies or percentages. Matched-group analysis was performed by propensity matching between patients with preoperative rehabilitation and controls. Propensity scores were generated in two steps using logistic regression analysis. Potential predictors were selected from published data review, known confounding covariates for the outcome of interest, differences between the two patient groups (Table 1), and clinical judgment. Continuous data were analyzed with analysis of variance (ANOVA), an independent Student’s t-test or the Mann-Whitney U-test. Categorical variables were analyzed with a chi-square analysis and Fischer’s exact test. The MACCE-free rates after surgery for the two groups were determined by Kaplan-Meier survival analysis and compared with the log-rank test. Analyses were conducted with JMP software, version 17.0 (SAS Institute Japan, Tokyo, Japan).
Table 1
Baseline patient characteristics (preoperative data)
SD: standard deviation
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IQR: interquartile range
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BMI: body mass index
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OMI: old myocardial infarction
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PCI: percutaneous coronary intervention
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PAD: peripheral arterial disease
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SCr: serum creatinine
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CRF: chronic renal failure
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AMI: acute myocardial infarction
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NYHA: New York Heart Association
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LVEF: left ventricular ejection fraction
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LMT: left main coronary trunk
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EuroSCORE: European system for cardiac operative risk evaluation
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