IMPAIRED MATCHING OF PERFUSION AND VENTILATION IN HEART-FAILURE DETECTED BY XENON-133

In severe chronic heart failure (CHF) the ventilatory cost of CO2 elim ination during exercise (VE/VCO2) is increased, suggesting ventilation /perfusion (V/Q) mismatch. The relationship of exercise VE/VCO2 regres sion slope nz to deadspace ventilation was studied in 15 patients with CHF who underwent cardiopulmonary exercise testing and arterial blood gas monitoring. Regional lung ventilation and perfusion was studied, using (133)xenon, at rest and peak exercise in a further group of 10 C HF patients and in five normal subjects. VE/VCO2 slope m correlated we ll with deadspace ventilation at peak exercise in the 15 patients with CHF. We therefore used exercise VE/VCO2 slope m to categorize CHF pat ients undergoing (133)xenon imaging into groups with increased (slope m > 36) or normal (slope m < 36) exercise deadspace ventilation. In no rmals, resting V/Q determined by (133)xenon showed a gravitational gra dient, which improved on exercise as a result of relative increases an d of relative reductions in regional perfusion; no significant changes in regional ventilation distribution were detected. In patients with CHF who had normal slope m (n = 5), rest and exercise V/Q were similar to the normal subjects. In CHF patients with increased slope nl (n = 5) however, the resting gravitational gradient of V/Q was lost, and th ere were no significant changes in relative perfusion distribution on exercise. These findings suggest that the increased ventilatory cost o f CO2 elimination found in certain patients with CHF is related to ina bility to coordinate and optimise the relative distribution of lung pe rfusion with respect to ventilation during exercise.