Background: Aerosolized iloprost is used as an alternative to IV prostacyclin in patients with pulmonary hypertension. The desired outcome of this treatment is a reduction of pulmonary pressure, which can be measured by right-heart catheterization or Doppler echocardiography. However, both techniques provide only snapshots of the hemodynamic state.
Patients and methods: The aim of our study was to test the usability of an implantable hemodynamic monitor (IHM) [the Chronicle, model 9520; Medtronic Inc; Minneapolis, MN] in patients with pulmonary hypertension. For this purpose, the device was implanted into five patients (mean [± SEM] age, 45 ± 16 years; all women) with pulmonary hypertension who had received long-term treatment with aerosolized iloprost (100 μg/d). Repeated short-term tests including two standard inhalations of iloprost as well as repeated long-term tests lasting 20 to 26 h, including nighttime, without inhalation were performed on an outpatient basis.
Results: The device provided information that was reproducible and individual for each patient during the entire study period. During short-term tests, pulmonary artery pressure was reduced from a mean (of all patients) of 68 ± 13 to 49 ± 11 mm Hg, with a mean total effective treatment time of 49 ± 8 min. Thereafter, pulmonary pressure returned to preinhalation levels before the next inhalation. Long-term tests showed similar results. During a total recorded time of 15,876 min, the vasodilator effect lasted 2,140 min, corresponding to 13% of the whole time span.
Conclusion: Our study provided new insights into the short-term and long-term effects of treatment with inhaled iloprost in patients with pulmonary hypertension. While there were no signs of tachyphylaxis, the improvement of central hemodynamics was much shorter than expected. Continuous hemodynamic monitoring with the IHM demonstrated the need to improve the treatment modalities of aerosolized iloprost in patients with pulmonary hypertension.