Scientific Background In many patients with severe left heart failure (LHF) a chronic pulmonary hypertension (PH) occurs during follow-up leading to a remodeling of pulmonary arteries with an increase in pulmonary artery pressure (PAP), pulmonary vascular resistance (PVR) and transpulmonary gradient (TPG). According to the International Society for Heart and Lung Transplantation and the German Standing Committee on Organ Transplantation, cardiac transplantation is contraindicated if values of PAP, PVR, and/or TPG are above 40 mmHg, 240 dyn x s x cm-5, and 15 mmHg, respectively. Even if the patients show only slightly elevated hemodynamic values at the time of application for transplantation, values most often reach the respective exclusion limits during the waiting period. Patients signed in for transplantation partially are not any longer electable for orthotopic heart transplantation (OHT) at the time of identification of an appropriate donor organ. In the meantime the time on the waiting list for heart transplantation is increasing. In 2001, patients being on the waiting list were undergoing heart transplantation within one year. In contrast, 972 patients were on the waiting list while only 325 heart transplantations were performed in Germany in 2011 (www.eurotransplant.nl).
At present, no specific therapy for PH due to left heart disease is available (Galie 2009), treatment with PAH agents is not recommended due to lack of data (Rosenkranz 2011).
There are only few studies with PH-targeted medication within this indication. Phosphodiesterase inhibitors (e.g. Sildenafil), Endothelin-receptor antagonists and Prostacyclin are potential agents for the treatment of PH during the waiting period for a heart transplantation.
Iloprost is a synthetic analogue of Prostacyclin PGI2. Iloprost dilates systemic and pulmonary arterial vascular beds leading to a reduction of blood pressure.
In a previous study the investigators administered aerosolized Iloprost (ILO) in 14 patients with pulmonary hypertension due to chronic cardiac failure on the waiting list for heart transplantation. Iloprost caused a significant reduction in pulmonary arterial pressure and pulmonary vascular resistance without severe side effects and was more effective than nitric oxide (Sablotzky, Grünig et al. 2002, 2003). In a retrospective non-controlled study in 51 patients awaiting orthotopic heart transplantation Iloprost inhalation caused a significant decrease in PVR (from 458 dyn x s x cm-5 to 345 dyn x s x cm-5), a significant decrease in TPG (21 mmHg to 17 mmHg), and a significant improvement in Cardiac Index (CI) from 2,09 l/min/m2 to 2,23 l/min/m2 (Schulz et al., 2010). In a retrospective non-controlled study low-dose Bosentan improved hemodynamic parameters and 1-year survival rate in 82 end-stage heart failure patients on the waiting list for cardiac transplantation (Hefke et al., 2011).
Randomized-controlled trials are missing within this indication. Sildenafil is not a medication of first choice due to contraindications and as well as many patients waiting for OHT are treated with nitrate (medication due to coronary heart disease). In contrast, inhaled Iloprost has advantageous effects on coronary perfusion. However, in this indication the adverse event profile of inhaled Iloprost regarding frequency and time-dependency is not yet clear. In Germany inhaled Iloprost is administered by the I-Neb AAD-System which allows precise, reproducible dose of the drug.
Due to the positive results in retrospective analyses and in the treatment of patients with pulmonary hypertension, the initiation of this proof-of-concept study seems to be justified.
