Influence of cancer severity and functional status of cancer on cardiac parasympathetic indicators

Objective: To investigate the influence of cancer severity and functional status of cancer patients on cardiac parasympathetic indicators. Methods: A total of 267 patients with a fresh clinical diagnosis of solid malignant tumor not yet put on cancer therapy and 250 controls matched for age, sex of study subjects were included. Severity of cancer was defined based on the American Joint Committee on Cancer staging. Accordingly, study subjects were subdivided into early stage (Stage I and II combined) and advanced stage (Stage III and IV combined). In cancer patients, the Eastern Cooperative Oncology Group (ECOG) performance score and the Faces Pain Scale score (FPS) was noted. Two indicators of vagal function, expiratory: inspiratory ratio (E:I ratio) and root mean square of successive N-N interval difference (r-MSSD) were included. E:I ratio during deep breathing at six respiratory cycles/minute and r-MSSD at rest was obtained from 1 minute lead II electrocardiogram. Data were analyzed by applying suitable statistical tests. p≤0.05 was considered significant. Results: R-MSSD and E:I ratio was significantly reduced in the early and advanced stage of cancer compared to controls (p≤0.0001). r-MSSD and E:I ratio was significantly reduced in advanced stage compared to the early stage of cancer (p≤0.0001). r-MSSD and E:I ratio was significantly different in subgroups of stages of cancer and controls (p≤0.0001). In cancer patients, r-MSSD was negatively correlated with ECOG and FPS score (p≤0.0278, p≤0.0100). Conclusion: Severity of cancer affects vagal function. However, r-MSSD alone was associated with functional status (ECOG, FPS) of cancer patients.