The effect of right ventricle diastolic functions and pulmonary hypertension on exercise limitation and relation with serum nt-probnp levels in chronic obstructive lung disease

Chronic obstructive pulmonary disease is an important morbidity and mortality cause across the world. During the course of the COPD, pulmonary hypertension (PHT) and right ventricular failure may develop due to elevated afterload of the right ventricle. PHT is associated with poor prognosis. In those patients, exercise capacity is reduced because of pulmonary and cardiac limitations. In this study, we included 31 moderate and severe COPD patients, and 20 healthy controls. Each patient was examined for parameters reflecting the right ventricular diastolic function by echocardiography along with assessment of the serum NT-proBNP levels. Cardiopulmonary exercise testing (CPET) was applied on the patients and the physiologic changes during the exercise were assessed. In order to evaluate the quality of life among our patients, which is an indicator of physical, psychological, and social health, SF-36 health survey was used. PHT was determined in 13 of our COPD patients by echocardiography. Among those cases, mean pulmonary arterial pressure (mean PA pressure) was 35,38 ± 7,48 mmHg. There was a statistically significant difference between the patient and control groups with regard to serum NT-proBNP levels; mean value was higher in the COPD patient group than in the control group (p<0.05). Serum NT-proBNP level was observed to be associated with PA pressure, however, no statistically significant difference was found between COPD patients with and without PHT in terms of serum NT-proBNP levels (p>0.05). There was a statistically significant difference between the COPD patients and the control group with regard to CPET parameters (particularly in terms of anaerobic threshold oxygen consumption [ATVO2] and carbondioxide production [ATVCO2], and peak oxygen consumption [PVO2] and peak carbondioxide production [PVCO2]). Mean values for those parameters were lower in the COPD patients. Serum NT-proBNP levels in CPET demonstrated a negative correlation between the AT and pVO2 values (L/min, ml/kg/min). Regarding the comparison of echocardiographic measurement parameters between COPD and control groups, only tricuspid annular plane systolic excursion (Tapse) value was found to be statistically significant among other right ventricular diastolic parameters. As expected, the wave of ventricular early filling velocity (Em), another diastolic parameter, was lower in the COPD patients. Serum NT-proBNP level and PA pressure, an echocardiographic measurement parameter, exhibited a significant relationship. In view of the relationship between echocardiography data and CPET parameters in the patient and control groups; Em wave, a right ventricular diastolic parameter, was observed to show a significant correlation with the amount of oxygen pumped to the peripheral regions by each heartbeat (O2 pulse). Moreover, there was a positive correlation between tricuspid E/A ratio and VO2 value at AT. There was no significant difference between the groups with and without PHT in terms of NT-proBNP, VO2 at AT, and VCO2 at AT. However, although tricuspid E-wave, a right ventricular parameter, was not found to demonstrate a significant difference echocardiographically, it was observed to be lower in patients with PHT. Based on the above mentioned findings, we believe that NT-proBNP levels may be elevated in COPD patients and in cases with high PA pressure, COPD patients may tend to develop right ventricular diastolic dysfunction due to right ventricular overload, and exercise limitation may be predicted by assessment of right ventricular functionality and NT-proBNP levels. Key Words: COPD, pulmonary hypertension, NT-proBNP, cardiopulmonary exercise testing, right ventricular diastolic dysfunction