Abstract
AIMS: In 2019, pulmonary vascular resistance (PVR) < 3WU was adopted to stratify patients at low risk in pulmonary hypertension due to left heart disease (PH-LHD) as well those with isolated PH-LHD. We sought to evaluate whether supervised machine learning with decision tree analysis, which provides more information than Cox Proportional analysis by forming a hierarchy of multiple covariates, confirms this risk stratification. METHODS AND RESULTS: Two hundred two consecutive patients (mean age: 69 ± 11 years, female: 42%) with mean pulmonary artery pressure ≥ 20 mmHg and wedge pressure > 15 mmHg were recruited. Transpulmonary pressure gradient ⩾̸ 12 mmHg, PVR ⩾̸ 3WU, diastolic pressure gradient ⩾̸ 7 mmHg, pulmonary arterial capacitance < 1.1 mL/mmHg, tricuspid annular plane systolic excursion (TAPSE) < 16 mm, peak systolic tissue Doppler velocity < 10 cm/s, right ventricular end-diastolic area ⩾̸ 25 cm(2) were the seven categorical values entered into the model due to their prognostic significance in PH. We used the chi-squared automatic interaction detection method to predict mortality. Each node and branch were compared using survival analysis at 6-year follow-up. Mean pulmonary artery pressure, wedge pressure, cardiac index, and PVR were 40.3 ± 10.0 mmHg, 22.3 ± 7.1 mmHg, 2.9 ± 0.8 L/min/m(2) , and 3.6 ± 2.1WU, respectively. Among the seven dichotomous, TAPSE was first selected following by PVR. Compared with patients with PVR < 3WU and TAPSE ⩾̸ 16 mm, patients with PVR ⩾̸ 3WU and TAPSE ⩾̸ 16 mm, or patients with PVR ⩾̸ 3WU and TAPSE<16 mm had significantly increased mortality, HR = 3.0, 95% CI = [1.4-6.4], P = 0.006 and HR = 3.3, 95% CI = [1.6-6.9], P = 0.002, respectively, while patients with PVR < 3WU and TAPSE < 16 mm exhibited the worst prognosis, HR = 7.2, 95% CI = [3.3-15.9], P = 0.0001. CONCLUSIONS: Used for solving regression and classification problems, decision tree analysis confirms that PVR and TAPSE have to be analysed together in PH-LHD and revealed the dangerous and contradictory prognostic significance of PVR < 3WU when TAPSE<16 mm.