[Effects of thromboendarterectomy for post-embolic pulmonary hypertension on physiological dead space on exercise]

The effect of therapy on the modification of a functional parameter is an elegant method for assessing the causal relationship between functional abnormalities and symptoms. We report an analysis of the effects of thromboendarterectomy for post-embolic pulmonary arterial hypertension on exercise functional parameters. A patient (62 years) had post-embolic pulmonary hypertension documented by pulmonary angiography and right heart catheterization (PAP mean: 48 mmHg). Cardiopulmonary exercise testing demonstrated a decreased aerobic capacity (59% predicted), significant hyperventilation (VE/VO(2) at peak 82) and a dead space to tidal volume ratio (VD/Vt) increased at rest (0.55) and remaining high at peak exercise (0.48). Thromboendarterectomy was performed and led to a dramatic improvement in dyspnoea (NYHA class II to I), a gradual improvement in aerobic capacity, and a significant decrease of VD/Vt (0.26) and hyperventilation (VE/VO(2) at peak: 38) on exercise. This observation illustrates the fact that an increase in the physiological dead space on exercise is associated with significant hyperventilation and consequently dyspnoea of effort.