Vascular compliance (C) governs the energetic coupling of the ventricle to the pulmonary circulation and, through its influence on pulse pressure and mechanotransduction, the nature and degree of adverse remodeling. We therefore assessed the impact of increasing intravascular pulmonary compliance by inserting a closed compliance system into the pulmonary arteries of 7 patients with established WHOI PAH undergoing diagnostic right heart catherization.
The system consisted of an inert gas filled balloon coupled to a gas filled reservoir container that allowed for the passive flux of gas between balloon and reservoir in response to cardiac cycle changes in pressure and volume. High fidelity pressure recordings and determination of CO were made at rest and during arm exercise.
There were no complications during vice insertion and testing. Activation of the device increased C by 0.4ml/mmHG (22%) and increased cardiac output by 0.6L/min (7%) at rest, while activation during exercise, increased C by 0.6ml/mmHG(47%) and cardiac output by 1.6L/min (20%). All patients were on optimal multi-drug management. Effective arterial elastance, a measure of static and pulsatile afterload, was reduced by 12% and 21% (rest and exercise). Stroke volume index increased by 9% and 26%.
The magnitude of the changes induced by balloon activation exceed those reported by the introduction of drug therapy, as well as changes in compliance that have been associated with altered mortality risk. The effective change induced by the intravascular compliance device may be of sufficient magnitude to either modify disease progression or effect reverse remodeling.