Pulmonary hypertension (PH) is uniformly defined as high pressure in the pulmonary vasculature but can be divided into three groups: active, passive, and reactive. According to the Department of Anaesthesia & Intensive Care of Chinese University of Hong Kong, passive PH is due to high pressure in post-pulmonary capillaries, active PH is due to obstructions in capillary and precapillary vessels, and reactive PH is due somewhat to an active-superimposed-on-passive component.
Reactive PH is viewed as most severe and is secondary to left-sided heart failure. Pulmonary vasculature shows abnormal structure and function in reactive PH, and a group of researchers led by Dr. Doron Aronson at the Israel Institute of Technology was interested in determining how these abnormalities affect pulmonary artery capacitance (PAC) and clinical outcome for affected patients.
Data presented in “Pulmonary Arterial Capacitance in Patients with Heart Failure and Reactive Pulmonary Hypertension” were obtained from 393 heart failure patients. The split between passive and reactive PH was fairly even, with 124 and 140 patients in each group, respectively. Not all patients had PH. These patients had high PAC compared to the PAC of reactive and passive PH patients. Lowest PAC was found in reactive PH.
As PAC is a measure of venous elasticity, and pulmonary vascular resistance represents the force needed to push blood through the vasculature, the two showed a hyperbolic inverse relationship. Reactive PH patients showed little improvement in PAC even if PVR was reduced.
These results may have directly impacted the clinical outcomes of the study group. After a mean follow-up period of 31 months, mortality was shown to be higher in patients with either reactive PH or reduced PAC. Pulmonary hypertension gave a hazard ratio of 2.59, and patients with adequate PAC had a hazard ratio of 0.72 for every 1mL/mmHg increase in PAC.
In light of this data, the researches believe, “PAC is a strong independent haemodynamic marker of mortality in heart failure and may contribute to the increased mortality associated with reactive PH.” Lead author Dr. Robert Dragu continued to explain, stating, “The development of reactive PH is associated with a marked reduction in PAC.” Perhaps these results will prove vital to studies interested in enhancing PAC to treat PH.
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