Evaluation of pulmonary hypertension severity: The role of cardiac autonomic nervous system

There have been researches on the autonomic nervous system involvement in Pulmonary Hypertension pathogenesis. However, there is restricted information on the correlation of this involvement with the disease severity. Heart rate recovery (HRR) value and heart rate variability (HRV) are indirect indicators of sympathetic and parasympathetic activity. The objective of this study is to evaluate the correlation between disease severity and HRV and HRR, in patients diagnosed with PH. A total of 50 patients, who were monitored in the Cardiology Clinic of Hacettepe University Faculty of Medicine, whose mean pulmonary artery pressure (mPAP) measured with the right heart catheterization was ≥ 25 mmHg, were included in the study. The disease severity was grouped according to mPAP. Heart rates of the patients were recorded in 6-minute walk tests performed routinely in patients' follow-ups. The difference between the heart rate at the end of the test and one minute after the test was recorded as HRR1. 24-hour Holter monitorization was applied to all patients and time- and frequency-dependent HRV results were calculated. As pulmonary hypertension severity increased, a decrease was determined at mean HRR1 levels. All patients in the severe PH group had an HRR1 level of ≤ 16 bpm. Half of the patients with moderate pulmonary hypertension had an HRR1 level of ≤ 16 bpm, while 3.3% of patients with mild PH had an HRR1 level of ≤ 16 bpm. SDNN levels were determined to be lower in the medium and severe group compared to the mild PH group. A negative correlation was found between mPAP and HRR1 and SDNN. A negative correlation was found between PVR and HRR1 levels. A positive correlation was found between cardiac outout and HRR1 and SDANN levels. In conclusion, an impairment was determined in HRR and HRV parameters. This impairment may be an indicator of the disease severity. These kind of findings can guide us through patient selection for novel interventional methods such as pulmonary artery denervartion. Keywords: Pulmonary hypertension, heart rate variability, heart rate recovery