# Preddiagnosis of Heart Failure (HF) Using Deep Learning and the Korotkoff Sound
## 3 Materials and Methods
### Database Acquisition  
This work was completed by the medical team of the Department of Cardiology, the fourth people's Hospital affiliated with Zhejiang University. All volunteers' heart conditions were evaluated in accordance with the ESC 2021 Guidelines [45]. Only HF patients with a left ventricular ejection fraction (LVEF) of less than 50% and healthy people with no cardiovascular disease or other underlying diseases were chosen as volunteers for this study. Each volunteer was thoroughly examined by experienced cardiologists prior to the test to ensure the sample's reliability. As shown in Table 1, a total of 365 samples were collected, including 116 healthy people and 249 HF patients. The average age of the healthy subjects was 42 \(\pm\) 22 years old, the average body mass index (BMI) was 24.8 \(\pm\) 2.1, the average LVEF was 65 \(\pm\) 7.5%, the average systolic blood pressure (SBP) and diastolic blood pressure (DBP) were 111 \(\pm\) 15 and 73 \(\pm\) 10 mm Hg, respectively; The patients' average age was 61 \(\pm\)17, their average BMI was 24.5 \(\pm\) 3.2, their average LVEF was 40 \(\pm\) 6.83%, and their average SBP and DBP  
Figure 1: The overall structure of this paper. were 129 \(\pm\) 35 and 77 \(\pm\) 20 mm Hg, respectively. NT-proBNP levels in selected patients ranged from 513 to 11,950 pg/mL, while NT-proBNP levels in healthy people were less than 125 pg/mL. When volunteers arrived at the echo lab, we advised them to sit for 10 min prior to the test in order to be as emotionally stable as possible, and then we took measurements in a temperature-controlled room (23-25 \({}^{\circ}\)C) [46]. The overall left ventricular systolic function of each patient was evaluated by two professional cardiac ultrasound technicians using a PHILIPS ultrasound instrument based on the patient's clinical status and established clinical guidelines [47]. We measured the left ventricular volume using the biplane method (improved Simpson) [48]. The corresponding LVEF and cardiac output was generated automatically by PHILIPS ultrasound machines. The audio collection equipment was a 3M Littman 3200 electronic stethoscope (480 kHz effective sampling frequency), which has a powerful environmental noise suppression capability that ensures the capture of essential sounds while reducing background noise by 85%. As shown in Figure 2, the stethoscope was placed directly above the brachial artery during the test to eliminate the influence of other interference factors on the test results [49]. The stethoscope probe was placed about 5 cm from the lower edge of the cuff. According to the blood pressure detection procedure, the cuff was pressurized to 180 mm Hg, and the measurement began with the cuff step-down until the last KS pulse disappeared. The test duration ranged from 14 to 25 s. To ensure the consistency of the test results, each volunteer was measured three times. After the test, the data was transferred to the workstation via mobile storage media or Bluetooth for analysis and processing. It should be noted that the current study described in this paper only collected information on the hospitalization status of consecutively diagnosed patients with heart failure; the patient's course and the impact of pharmacological therapy on the prediagnosis are not considered. Furthermore, the impact of diabetes, hypertension, coronary heart disease, renal failure, anemia, and other comorbidities of HF patients on HF pre-diagnosis results, as well as the impact of separate body weight and breast analysis on KS records based on BMI and gender, are very important. So far, we have not paid attention to these issues, which is a limitation of our current dataset.