Cardiopulmonary Testing and Pulmonary Hypertension in Patients with Sickle Cell Anemia

Objectives: Sickle cell disease (SCD) is responsible for multiple complications that can lead to dyspnea, including pulmonary hypertension (PAH). PAH is a common cause of death among these patients and represents a prognosis feature, but can be clinically difficult to detect. We reviewed the charts of patients with SCD and analyse correlation between hemoglobin level, EKG, chest X-ray, pulmonary function tests, and cardiopulmonary exercise test (CPET) with echocardiography.

Methods: We performed a retrospective chart review of 25 patients with SCD (11 patients with SC, 12 patients with SS and 2 patients with S-β thalassemia haplotype). All patients had pulmonary functions testing, CPET and resting echocardiography in the same period. PAH was defined as tricuspid regurgitant jet velocity (TRJV) >2,5 m/s on cardiac echography. Subjects underwent symptom-limited CPET using cycle ergometry and individualized ramp protocol. Exercise was stopped when subject showed criteria of maximality or inability to keep the pace. Breath-by-breath analysis was done.

Results: Only 3 patients had PAH. All these patients were SS and suffered numerous acute thoracic syndrome. No correlation were made between lower hemoglobin level and higher TRJV; no patients had EKG or CXR anomaly. DLCO/VA appeared to be a independent risk factor: DLCO/VA < 75 % correlated with a TRJV > 2,5. CPET was abnormal in all patients, but were limited by patient fatigue and patterns were consistent with peripheral muscle disease except for one patient who had PAH; this patient showed a higher VE/VCO2 and a slower pulse kinetics, compatible with pulmonary vasculopathy.

Conclusions: Decrease DLCO/VA may indicate a sickle pulmonary vasculopathy. and this factor appears to play a significant role in detecting PAH in SCD patients. CPET was a safe procedure and gave details about global aerobic performance and exercise tolerance. Because of peripheral muscle limitations, CPET still an unreliable diagnostic test for PAH. Peripheral muscle dysfunction could explain a large part of exercise intolerance, but physiopathologic mechanisms still underexplored.