**Funding**

This study was supported by the Deutsche Forschungsgemeinschaft (grants to R. Schulz and K.-D. Schlüter within the graduate school "PROMISE"/IRTG1566, a grant to K.-D. Schlüter (SCHL 324/7-1), a grant to T. Schreckenberg (Deutsche Herzstiftung)). K.-D Schlüter is principal investigator in the CRC 1213 "Pulmonary Hypertension and Cor pulmonale", project B05.
