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Pulmonary Hypertension Program Highlights from Prague

Robert Frantz, MD
Pulmonary Hypertension Council Chair

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robert frantzPulmonary hypertension and the right ventricle represented a major theme of the 2012 ISHLT Scientific Sessions in Prague, continuing an evolving trend over recent years. Offerings included:

3 Pre-meeting symposia:

Potpourri of Special Topics in PH
The RV and Pulmonary Vascular Load in Health and Disease
Congenital Heart Disease: PH Dilemmas in Pediatrics and Adult Patients

3 Scientific Sessions Concurrent Sessions:

Lung Transplantation for PAH - World-wide Panel Discussion
Following the RV through Thick and Thin
PH in Chronic Parenchymal Lung Disease - Does it Matter?

Thursday lunch session:

Optimised PAH Management: Doing the Right Thing for the Right Heart (sponsored by United Therapeutics)

The illuminating presentation by Dr. Ryan Tedford regarding the relationship between pulmonary artery resistance (RPA) and capacitance (CPA) was especially valuable. Expanding on prior work describing the hyperbolic and in many situations constant relationship between these parameters, Dr. Tedford reviewed his recently published work (Circulation 2012;125:289-287) that includes several important messages:

     1) Clinical trials of PAH therapy have generally enrolled patients who have quite high pulmonary vascular resistance. Such patients are on the flat part of the resistance - compliance relationship, meaning that a modest change in resistance produced by a PAH therapy is not going to alter compliance in any substantial way. This may help to explain why PAH remains a serious condition despite availability of several therapies. Interestingly, the steep part of the resistance-compliance curve, where modest changes in resistance can have substantial effects on compliance, is in the neighborhood of 3 Wood units, reinforcing the potential value of early identification and treatment of PAH.
     2) RV failure in the context of pulmonary hypertension accompanying left heart failure often occurs in patients with pulmonary vascular resistances in the modestly elevated range of 2-5 Wood units, where a reduction in PVR achieved by addition of appropriate medication can have a big impact on pulmonary artery compliance, suggesting much opportunity in this arena.
     3) A very important lesson of this work is the finding that elevation in pulmonary capillary wedge pressure results in a shift of the resistance-compliance relationship. For any given pulmonary artery resistance, a fall in wedge from high to normal will result in improvement in pulmonary artery compliance. This in part explains why correction of elevated wedge pressure can have such a dramatic effect on severity of right heart failure, whether by better LV afterload reduction and volume regulation, or by implantation of a left ventricular assist device. Elevated wedge pressure contributes in a substantial way to RV afterload, via the impact of the reflected wave on the RV during ejection. This presentation is just one example of how valuable attendance at ISHLT has become for all those interested in the right ventricle and the pulmonary vasculature.

Disclosure Statement: Dr. Frantz has received research grants from United Therapeutics, and has provided consulting for Pfizer, Inc.