Cardiopulmonary Exercise Testing Contributes to Accurate Risk Assessment in Patients with Low-risk Pulmonary Hypertension

Background: European guidelines for pulmonary arterial hypertension (PAH) stratify the risk using clinical characteristics and complementary studies, including the cardiopulmonary exercise test (CPET). This takes into account 3 parameters: peak O consumption (peak VO ), its percentage with respect to the predicted VO, and the minute ventilation/carbon dioxide production (VE/ VCO ) slope. However, none of the models that validated this way of stratifying risk included PCPE among their variables. Objectives: To determine what proportion of patients with group I PAH considered to be at low risk and who walk >440 meters in the 6-minute walk test (6MWT) have parameters considered to be of moderate or high risk in the PCPE. Methods: Patients >18 years of age, diagnosed with group I PAH at low risk of events, who walked >440 meters in the 6MWT and had NT-proBNP value < 300 pg/dL were included. A CPET was performed in which the peak VO, its percentage with respect to the predicted VO, and the VE/VCO slope were recorded. It was determined what proportion of patients presented these parameters in a higher than low risk stratum (peak VO consumption ≤15 ml/min/Kg, its percentage with respect to the predicted VO ≤65% and the VE/VCO slope ≥ 36). Results: Eighteen patients were included. Despite being low-risk patients with a good functional class, all patients presented a peak VO less than 85% of predicted, which determines a deterioration of functional capacity. A single patient (6%) presented the three parameters evaluated at low risk, 8 patients (44%) had at least one altered parameter, 7 patients (39%) presented 2 altered parameters and in 2 patients (11%) all parameters were altered. The parameters that were most frequently altered were the percentage of predicted peak VO and the VE/VCO slope in 67% of the cases. Only 4 patients presented a peak VO <15 ml/kg/m. No patient presented peak VO values or percentage of predicted VO in the high-risk category. However, 6 patients (33%) presented a high-risk VE/VCO slope. Conclusion: Majority (92%) of the patients considered low risk and who walk more than 440 meters in 6 minutes presented at least one altered variable in the CPET. The VE/VCO slope and the percentage of predicted peak VO consumption were the most frequently altered variables. The VE/VCO slope was the only one that showed values considered high risk. CPET could have a place in the precision stratification of low-risk patients. The value of this finding should be evaluated in prospective studies.