Cardiac comorbidities in COPD patients explained through HRV analysis and respiratory indices of disease severity

Chronic obstructive pulmonary disease (COPD) patients exhibit depressed heart rate variability (HRV), while comorbidities may worsen the patients’ prognosis. We investigated whether HRV analysis, clinical markers of disease severity and respiratory function, may explain the presence of cardiac-related comorbidities. Several HRV indices were evaluated in 46 COPD patients before a 6- minute walk test (6MWT). Maximum heart rate (HRmax) and walked distance (Dist) were measured during the test, while heart rate recovery (HRR) was estimated immediately afterward. All these features and the patient characteristics were used to identify cardiac-related comorbidities (COPDco, n=11). A logistic regression classifier with regularization was used for modeling and feature selection, while model assessment was performed by leave-one-out cross-validation. Only 4 features were needed to accurately identify comorbidities with overall performance metrics AUC=84%, sensitivity=77% specificity=83%. The feature subset included the ratio given by the forced expiratory volume and the forced vital capacity ((FEV1/FVC), the normalized HRR at minute 3, the Borg-scale of exertional dyspnea and the normalized LF power. These features could provide relevant information for early identification of cardiac comorbidities in COPD patients