Hemodynamic Observations in Two Pulmonary Hypertensive Patients Changing Treatment From Inhaled Iloprost to the Oral Endothelin-Antagonist Bosentan

Creation of a Model Comparing 6-Minute Walk Test to Metabolic Equivalent in Evaluating Treatment Effects in Pulmonary Arterial Hypertension

BACKGROUND

The 6-minute walk test (6MWT) is the current standard to assess exercise capacity in pulmonary arterial hypertension (PAH). We compared the Naughton-Balke treadmill test reported in exercise metabolic equivalents (METs) with the 6MWT to evaluate whether MET could be a useful tool to assess exercise capacity.

METHODS

Serial 6MWTs followed by Naughton-Balke treadmill tests were performed in 47 PAH patients initiating a change in PAH therapy at baseline (i.e., Time 0) and Weeks 6, 12, 24 and 48; New York Heart Association (NYHA) functional class (FC) was also assessed. Hemodynamics data were recorded at baseline and Weeks 12 and 48. Treadmill time was converted to MET. Generalized estimating equation models, receiver-operating characteristic curves and fixed-effect linear models were utilized to create a model comparing 6MWT to MET.

RESULTS

MET correlated with 6MWT (r = 0.62). Piecewise linear function described the relationship between 6MWT and MET. 6MWT and MET were both associated with FC (p < 0.001) with similar ability to discriminate FC. Changes in hemodynamics in response to a change in PAH therapy correlated with changes in both 6MWT and MET. In less sick patients (i.e., FC II), the changes in 6MWT were less pronounced than with MET.

CONCLUSIONS

MET appears to be a reliable measure of exercise capacity in PAH, and correlates with 6MWT. MET can be used in clinical assessment and is helpful in demonstrating improvements in exercise capacity in less sick patients.

Right Ventricular Pressure Waveform and Wave Reflection Analysis in Patients With Pulmonary Arterial Hypertension

BACKGROUND

Cardiac index is an important determinant of outcome in patients with idiopathic pulmonary artery hypertension (IPAH). An implantable hemodynamic monitor (IHM) [Chronicle; Medtronic; Minneapolis, MN; a system limited to investigational use only] that records right ventricular (RV) pressure waveforms continuously may increase our understanding of IPAH and improve therapeutic selections and outcomes. The aim of this study was to investigate whether the RV pressure waveform utilizing an IHM can be used to estimate the magnitude of pressure wave reflection and cardiac index in patients with IPAH in acute settings.

METHODS

In eight patients with pulmonary arterial hypertension, RV pressure waveforms were recorded utilizing the IHM, and breath-by-breath cardiac index was recorded during acute IV epoprostenol infusion at 3, 6 and 9 ng/kg/min. Late systolic pressure augmentation and cardiac index were estimated using the RV pressure waveforms and correlated with direct measurement of cardiac index.

RESULTS

At baseline, the cardiac index was 2.1 +/- 0.2 L/min/m(2), total pulmonary resistance index was 38 +/- 2 Wood U/m(2), and RV systolic pressure was 92 +/- 4 mm Hg. Wave reflection accounted for 29 +/- 1 mm Hg of the RV systolic pressure. During epoprostenol infusion, total pulmonary resistance index and wave reflection decreased (- 15 +/- 4 Wood U/m(2), p < 0.001, and - 5 +/- 2 mm Hg, p < 0.05, respectively). The breath-by-breath cardiac index correlated with the RV pressure waveform cardiac index estimates (r(2) = 0.95).

CONCLUSIONS

RV pressure waveform analysis provides continuous hemodynamic assessments including cardiac index in acute settings. Once confirmed in long-term settings, this information may prove useful in optimizing a treatment regimen in patients with IPAH.

Long-term follow-up after conversion from intravenous epoprostenol to oral therapy with bosentan or sildenafil in 13 patients with pulmonary arterial hypertension

BACKGROUND

Epoprostenol significantly improves function and survival in patients with pulmonary arterial hypertension (PAH) but is associated with many risks and side effects. Furthermore, effective oral therapy is now available. We report our long-term experience with 13 patients from among 118 treated with epoprostenol who were able to be weaned to oral therapy, including 6 with persistently abnormal hemodynamics (mean pulmonary artery pressure > or = 35 mm Hg).

METHODS

Oral therapy with bosentan (n = 11) or sildenafil (n =2) was started before weaning epoprostenol in all but 1 patient. Right heart catheterization was performed when patients reached a dose of 2 ng/kg/min, and epoprostenol was discontinued with hemodynamic monitoring. Functional class and 6-minute walk test were assessed at regular intervals. Repeat right heart catheterization was performed 1 year after discontinuation of epoprostenol.

RESULTS

Nine patients remained on oral therapy alone for up to 46 months. Four patients deteriorated in functional class, and 2 of them resumed epoprostenol therapy. Inhaled iloprost was started in another patient. One additional patient died, unrelated to PAH. Twelve patients underwent right heart catheterization at the time of epoprostenol discontinuation. Hemodynamic evaluation 13.2 +/- 0.9 months later showed that the 5 patients with normal or nearly normal hemodynamics at the time of discontinuation of epoprostenol had no deterioration, whereas 4 of the 7 patients with abnormal hemodynamics had worsened. The 6-minute walk test at last follow-up was not significantly changed from maximal distance on epoprostenol (420 +/- 94 vs 412 +/- 95 meters).

CONCLUSION

Weaning from epoprostenol to sildenafil or bosentan with sustained clinical improvement is possible, even with persistent pulmonary hypertension; however, patients with persistently abnormal hemodynamics are at risk for hemodynamic and clinical deterioration and require close follow-up.

Implantable hemodynamic monitoring devices in heart failure

The syndrome of heart failure is characterized by symptoms that are relatively insensitive and nonspecific. Physical diagnosis may be unreliable even in the hands of experienced clinicians despite the presence of significantly elevated filling pressures or a significantly depressed cardiac output. Over the past decade, the implantable hemodynamic monitor (IHM) has been developed as means of measuring intracardiac pressures over time and understanding the nuances of the hemodynamic derangements of this condition. With improved ability to accurately assess and monitor filling pressures, clinicians can more precisely adjust therapy with the goal of improving patient symptoms and possibly outcomes. Future directions include using the IHM to assist in management of other cardiovascular diseases, such as pulmonary arterial hypertension, and combining this technology with other implanted devices, such as defibrillators.