Study flowchartThe flowchart for the current study is illustrated in Fig. 1 Fig. 1General Information

For this study, a total of 50 CAD patients who underwent PCI intervention at the Department of Cardiology and Cardiac Rehabilitation Outpatient Clinic of the First People’s Hospital of Xiangyang from June 2020 to December 2021 were randomly selected. Patients were allocated into two groups using a random number table: the Ctrl group (comprising 25 patients receiving combined standard pharmacological treatment and enhanced health education) and the Int group (consisting of 25 patients who received ET intervention in addition to the Ctrl group’s treatment). The study aimed to analyze the impact of these two treatment approaches on the rehabilitation outcomes of CAD patients. The research adhered to the principles outlined in the Helsinki Declaration. Furthermore, in accordance with applicable legal regulations and medical ethical guidelines, all subjects participating in the study were adequately informed about the potential risks, benefits, and psychological stress associated with physical exercise, and they provided informed consent. The specific inclusion and exclusion criteria for the study participants are as follows:

Inclusion criteria: (i) patients meeting the diagnostic criteria for CAD; (ii) patients who met the exercise experiment and training criteria published by the American Heart Association in 2013; (iii) patients with evident ischemic changes on resting ECG and/or myocardial ischemia on CPET at attack; (iv) patients who were treated with coronary artery stenting; (v) patients who had no continuous exercise habit in the past exercised less than twice per week and each exercise time was less than 15 min; (vi) the New York Heart Association cardiac function grading was grade II to III; and (vii) the patient was stable and able to receive exercise therapy.

Exclusion criteria: (i) patients with acute myocardial infarction occurring within the last 30 days; (ii) patients with chronic obstructive pulmonary disease, pulmonary embolism, stroke, and other diseases that can affect lung function; (iii) patients with unstable angina pectoris, or grade IV angina pectoris; (iv) patients with severe arrhythmia, cardiac insufficiency, or aortic dissection/stenosis; (v) patients with severe liver and kidney dysfunction; (vi) those who suffered from language communication disorder, hearing disorder, and mental dysfunction affecting communication; (vii) patients with infectious diseases, malignant tumors, or diseases of the blood system; and (viii) patients with rheumatism or motor diseases affecting training.

Therapy methods

Interventional treatment was performed. All patients underwent PCI treatment. During the surgical procedure, patients were placed in a supine position, and local anesthesia was administered at the right wrist using 1% lidocaine (B. Braun Melsungen AG, Germany). Subsequently, the Seldinger technique was employed to puncture the right radial artery, and a 6 F arterial sheath introducer (Terumo Corporation, Japan) was inserted. Following sheath placement, an appropriate dose of heparin (Pfizer Pharmaceuticals, USA) and nitroglycerin (AstraZeneca, UK) was administered, and multiposition coronary angiography was performed using a 5 F multifunctional catheter (Cordis Corporation, USA) to assess the condition of the coronary arteries. Once the degree of stenosis was confirmed (stenosis > 80%, with residual stenosis < 20% poststent deployment), PCI was performed, and the expansion and adhesion of the stent were assessed postdeployment. For patients who received thrombolytic therapy in the target vessel due to myocardial infarction, a clinical trial-based flow assessment was utilized for evaluation.

Patients in the Ctrl group received standardized pharmacological treatment and enhanced health education. Health education related to CAD was provided to the patients, including dietary habits: patients were informed about the impact of diet on CAD and educated to choose healthy foods, including a low-fat, low-cholesterol diet rich in vegetables and fruits, and to reduce salt intake. Furthermore, they were instructed on how to manage their diet to maintain a healthy weight; healthy lifestyle: promoting a healthy lifestyle is crucial for CAD patients. Patients were encouraged to quit smoking, limit alcohol intake, increase physical activity, control chronic conditions such as hypertension and diabetes, and undergo regular check-ups; psychological support: CAD can have a negative impact on patients’ psychological well-being. Therefore, providing psychological support and education to help patients cope with anxiety, depression, and psychological stress is essential. This included psychological therapy, relaxation techniques, and introductions to support groups; survival education for cardiovascular emergencies: patients were educated on how to respond to potential cardiac emergencies, including angina and heart attacks. They needed to understand how to use emergency medications, make emergency calls, and take immediate action when symptoms occurred.

In the Int group, in addition to the treatment methods applied in the Ctrl group, patients received ET interventions. The following is a detailed description of the ET intervention: warm-up exercises: before commencing the formal ET, patients engaged in 5 to 10 min of warm-up exercises. The purpose of this warm-up phase was to prepare the body for higher-intensity exercise and reduce the risk of injury. Warm-up exercises primarily included low-intensity aerobic activities or low-intensity stretching exercises. Formal exercise: formal ET training encompassed fixed treadmill running, treadmill exercises, or upper body fluid resistance training (NordicTrack T Series, USA). These exercises were predominantly aerobic in nature and aimed at improving cardiopulmonary health, enhancing muscular strength, and promoting overall well-being. Exercise intensity assessment: to ensure patient safety, exercise intensity needed assessment. The Berg Balance Scale is a commonly used tool for assessing the risk of falls in elderly individuals. A score within the range of 13 to 16 on this scale was necessary to ensure that patients had sufficient exercise capacity to undertake formal exercise. Training frequency and duration: the duration of each formal aerobic ET session ranged from 30 to 60 min. The training frequency was set at 3 to 4 sessions per week, with a 1-day interval between each training session. This training schedule was designed to promote improvements in cardiopulmonary health and physical adaptability. Electrocardiogram (ECG) monitoring: To monitor the cardiac status of patients during exercise, a remote ECG telemetry system (Siemens Remote Service system, Siemens Healthineers AG, Germany) was employed. This allowed for the timely detection of ECG abnormalities to ensure patient safety. Stop criteria: If patients experienced progressive chest pain, pallor, dizziness, fatigue, shortness of breath, or discomfort during exercise, they were instructed to immediately cease the activity. These symptoms could be indicative of cardiovascular issues. Following exercise cessation, the physician might need to administer medications such as nitroglycerin based on the patient’s condition. The specific parameters of ET, including frequency, intensity, time, and type (FITT), are detailed in Table 1.

Table 1 Specific indicators of FITT parametersRoutine blood indicators

In this study, the Hitachi 7170 A Automatic Analyzer (manufactured by Hitachi, Japan) was employed to measure the levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL). This analysis served to assess cardiovascular health and risk factors.

Quantitative load index

Heart rate (HR), blood pressure (BP), rating of perceived exertion (RPE), and ST segment were measured using the Cortex Biophysik Metamax II Gas Analysis System (Cortex Biophysik GmbH, Germany).

Pulmonary function evaluation

Static lung function was assessed using the MINAO AS-507 Spirometer (MINATO, Japan). The primary parameters measured included forced expiratory volume in 1 s (FEV1), the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC%), and maximum voluntary ventilation (MVV).

Cardiac ultrasound examination

Cardiac function was assessed in the morning from 9 to 10 using a cardiac color Doppler ultrasound diagnostic system (General Electric Healthcare, USA). This evaluation encompassed the measurement of key parameters, including left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), and left ventricular end-systolic diameter (LVESD). The specific procedure was as follows: patients were instructed to lie supine on the examination bed, and the ultrasound probe was set at a frequency of 8.2 Hz. Subsequently, the gel-coated ultrasound probe was placed on the patient’s chest, covering areas including below the sternum and to the left of the sternum, to acquire the LVEF, LVEDD, and LVESD parameters of the heart.

CPET test

In this study, the assessment of patients’ cardiopulmonary function, respiratory system efficiency, and exercise capacity was conducted before and after the intervention using the PFTErgo V10.0 A cardiopulmonary exercise testing (CPET) system from COSMED (Italy). The CPET testing in this study utilized a stationary bike protocol with a progressive workload increase every minute, allowing patients to reach their maximum achievable load within 8–12 min. After increasing the workload on the stationary bike, patients continued exercising on a treadmill and were subsequently monitored after cessation of exercise. Clinically, the peak values between 8 and 12 min are commonly used to assess patient rehabilitation progress. Data from the CPET examination were determined based on standardized principles. The primary parameters included the minute ventilation-to-carbon dioxide production slope (VE/VCO2 − Peak), anaerobic threshold (AT), peak oxygen pulse (VO2/HR Peak), 1-minute postexercise heart rate recovery (HRR1), oxygen uptake efficiency plateau (OUEP), peak load power (PLP), increased power exercise time (IPEt), and peak metabolic equivalents (METs).

Evaluation of anxiety and depression

The Self-Rating Anxiety Scale (SAS) [15] and Self-Rating Depression Scale (SDS) [16] were adopted to evaluate anxiety and depression, respectively. The SAS and SDS contain 20 items, and each item is divided into 4 levels. When the score is less than 50, it indicates that the patient’s mood is normal, and there is no obvious anxiety or depression. Scores of more than 50 indicate significant anxiety or depression. The higher the SAS and SDS scores were, the more serious the anxiety or depression.

36-item short-form (SF-36) health status assessment

Patients’ health status was evaluated using the SF-36 scale [17], which includes 36 items and 8 dimensions. They are physiological function (PF), physiological function (RP), physical pain (BP), general health status (GH), energy (VT), social function (SF), emotional function (RE), and mental health (MH). The higher the SF-36 score is, the better the patient’s health.

Outcome measures

The primary outcome measures in this study encompassed pulmonary function assessment parameters (FEV1, FEV1/FVC, MVV), cardiac function indicators (LVEF, LVEDD, LVESD), and CPET test results (peak VO2, AT, VO2/HR peak, OUEP, PLP, IPEt, and METs).

The secondary outcome measures in this study comprised lipid profile results (TC, TG, HDL, LDL), quantitative load index results (HR, BP, RPE, ST segment), SAS, SDS, and SF-36 assessment outcomes.

Statistical analysis

SPSS 19.0 was employed. The mean ± SD was used for measurement data consistent with a normal distribution, and an independent sample T test was adopted for analysis of comparisons between the two groups. The frequency (percentage) of counting data was expressed, and the chi-square test was performed to analyze the comparison between the two groups. Pearson correlation analysis was implemented to analyze the correlation between CPET and LVEF. P < 0.05 indicated a statistically significant difference.