Exercise haemodynamic variables, measured shortly after diagnosis, correlate with exercise capacity and predict survival in patients with pulmonary arterial hypertension (PAH), study findings indicate.
Cardiac index during exercise and the change in cardiac index from rest to exercise, both measured with right heart catheterisation within 5 weeks of diagnosis, correlated significantly with 6-minute walk distance (6MWD) in a study of 55 patients with idiopathic, familial or anorexigen-associated PAH.
The study, by Ari Chaouat (Hôpital de Brabois, Vandoeuvre-lès-Nancy, France) and colleagues, also showed that change in cardiac index from rest to exercise was a significant independent predictor of survival, with each L/minute per m2 change associated with an 83% decrease in the chances of survival during the median follow-up period of 67 months.
Among the study participants, 87% were alive at 1 year, 81% at 2 years and 69% at 3 years. However, all patients with a 50% or greater increase in cardiac index from rest to exercise at baseline were alive after 18 months of follow-up, even when their cardiac index at rest was low.
Therefore “[c]hange in cardiac index from rest to exercise may be a useful end-point for clinical research and may help to guide treatment decisions in the individual patient”, Chaouat and co-authors remark in the European Respiratory Journal.
Indeed, receiver operating characteristic curve analysis showed that a 20% increase in cardiac index from rest to exercise was the optimal threshold for determining survival at 18 months, with a sensitivity and specificity of 70% and 80%, respectively.
The researchers also found that cardiac index during exercise decreased significantly as New York Heart Association (NYHA) functional class increased. By contrast, cardiac index at rest was not significantly different across NYHA groups.
Chaouat et al note that the “constant workload cardiopulmonary testing during right heart catheterisation was easy to perform and safe.”
Furthermore, “[c]ompared with 6MWD, pulmonary haemodynamic values during mild-to-moderate exercise in the supine position may be less affected by peripheral muscle weakness, increased dead-space ventilation and dynamic lung hyperinflation.”
The team concludes that exercise cardiac index and change in cardiac index from rest to exercise “should be further investigated in prospective studies and perhaps in a randomised controlled trial.”
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