Perioperative management may have strong connections with postoperative complications (PCs). However, little is known about the perioperative risk factors of PCs after septal myectomy in hypertrophic obstructive cardiomyopathy (HOCM) patients. This study is designed to assess the in-hospital PCs rate of HOCM patients and to identify perioperative risk factors of PCs in patients who underwent septal myectomy. Retrospective chart review will identify adult HOCM patients who underwent septal myectomy from October 2013 to December 2018 in the investigators' hospital. Patients' data will be collected from electronic medical records. The multivariable logistic regression analysis will be used to determine independent predictors. The predictive ability of individual predictor and different combination of multiple risk factors on PCs will also be calculated.

This study is a single center retrospective observational study designed to assess the in-hospital PCs rate of HOCM patients and to identify perioperative risk factors of PCs in patients who underwent septal myectomy.

Ethical approval of this study was obtained from the Institutional Review Board of the investigators' hospital (No. KY20192036-C-1). The requirement for written informed consent was waived by the Institutional Review Board, considering the retrospective nature of the study.

Retrospective chart review will identify adult HOCM patients who underwent septal myectomy from October 2013 to December 2018 in the investigators' hospital. The clinical diagnosis of HOCM is made by echocardiography, cardiac magnetic resonance imaging, or computed tomography of a hypertrophied, non-dilated LV, in the absence of cardiac or systemic disease that can aggravate the magnitude of hypertrophy.

Data Collection

The following data will be collected. Data will be obtained from electronic medical records and collected by two trained staff who are unaware of the purpose of the study.

1. Demographic and clinical data included New York Heart Association class, family history of hypertrophic cardiomyopathy (HCM) and sudden death, patient history, symptoms, medications, and comorbidities of these enrolled patients.
2. The following preoperative echocardiographic parameters will be collected : left atrium diameter, left ventricular (LV) ejection fraction (EF), maximal LV wall thickness (defined as the greatest thickness measured at any site within the LV wall), maximal interventricular septal thickness, left ventricular outflow tract diameter (LVOTd) (C-sept distance, the shortest distance from the septum to the coaptation point of the mitral valve), and resting left ventricular outflow tract (LVOT) gradient (measured with continuous-wave Doppler in the apical five-chamber view using the modified Bernoulli equation).
3. Intraoperative data collected include the duration of anaesthesia, surgery, CPB, and cross-clamp; excised LV weight; type of concomitant procedure; lowest body temperature, haematocrit , haemoglobin and highest Lactic acid; perioperative fluid management including the volumes of total fluid intake, total output and intraoperative fluid balance (total intraoperative fluid intake is calculated as the sum of crystalloid, colloid and blood products; total output was calculated as the sum of the volumes of estimated blood loss and urine output; intraoperative fluid balance is calculated by subtracting the total output from the total fluid intake); and blood pressure parameters including the baseline mean arterial pressure and lowest mean arterial pressure, and duration of intraoperative hypotension (intraoperative hypotension is defined as a mean arterial pressure <65 mmHg).
4. Postoperative ventilation hours, lengths of stay in the intensive care unit (ICU) and hospital, blood transfusion in 72 hours after surgery, EF, LVOTd, resting LVOT gradient gradient, and in-hospital PCs will also be obtained. In-hospital PCs include all-cause mortality, heart failure, low cardiac output syndrome, stroke, spinal cord injury, acute respiratory distress syndrome, reintubation, reoperation, permanent implantable cardioverter defibrillator, kidney injury, renal failure, liver injury, and liver failure.

Statistical analysis

Continuous variables will be expressed as mean ± standard deviation (SD) or median (interquartile range). Differences of continuous variables will be analysed by using a parametric unpaired Student's t-test or non-parametric Mann-Whitney U-test, as appropriate. Categorical variables will be described as percentages (%) and compared using the chi-square test or Fisher's exact test. For all analyses, a two-tailed P-value <0.05 will be considered statistically significant. The multivariable model will be used to determine independent predictors by including only variables that are identified by univariable analysis as significant prognosis risk factors with a P-value <0.05. Receiver operating characteristic curve will be used to calculate the cut off values of individual risk factors. The predictive ability of individual predictor and different combination of multiple risk factors on PCs will also be calculated. SPSS software version 22.0 (IBM Corp., Armonk, NY, USA) will be used to analyse the data.

Privacy

All data collected in this study will be stored on computer systems that require user authentication for log on. After data collection is complete, none of this electronic data will be stored with subject-identifying information and will be archived and kept indefinitely.

Inclusion Criteria:

• Adult patients ≥18 years of age who underwent thoracotomy for septal myectomy.

Exclusion Criteria:

• Patients with severe liver and renal disease, severe central nervous system disease, malignancy, defibrillators and age under 18 years old

Patients with a confirmed clinical diagnosis of HOCM were referred for surgical septal myectomy in a tertiary hospital in China