Bernstein EJ, Mandl, LA, Gordon JK, Spiera RF, Horn EM. Submaximal Heart and Pulmonary Evaluation: A Novel Noninvasive Test to Identify Pulmonary Hypertension in Patients With Systemic Sclerosis, Arthritis Care & Research (2013) doi:10.1002/acr.22051. First publised online September 24, 2013.
A six-minute exercise-based test successfully and non-invasively diagnoses pulmonary hypertension (PH) in patients with systemic sclerosis, researchers say.
Their retrospective chart study included 19 patients with limited or diffuse cutaneous systemic sclerosis, 15 of whom were diagnosed with pulmonary hypertension. All participants underwent the submaximal stress “step test” along with right-sided heart catheterization. The latter is the gold standard for pulmonary hypertension diagnosis, but is invasive and expensive, the authors point out.
The Step test is a novel submaximal stress test that monitors heart rate, rhythm, breathing patterns, and the pressure of exhaled CO2 after 3 minutes of stepping up and down repeatedly on 5.5” high step. Patients with PH are unable to increase cardiac output or pulmonary blood flow during exercise, leading to a lower “end tidal carbon dioxide” (or PETCO2) – changes which the Step test measures with a special system to gauge gas exchange.
The entire test takes six minutes with two minutes of baseline monitoring, three minutes of step exercise and one minute of recovery.
The Step test shows a sensitivity of 100% and specificity of 75% for identifying pulmonary hypertension. The test's positive predictive value is 93.8% and the negative predictive value is 100%.
The researchers report that change in end- tidal CO2 as measured by the step test has a “very strong, statistically signiﬁcant” negative correlation with mean pulmonary artery pressure (mPAP) on right-sided heart catheterization. In addition, end- tidal CO2 on the step test is better correlated with mPAP on right-side heart catheterization.
Finally, the step test performs better than transthoracic echocardiogram and pulmonary function testing.
The authors caution that this is a retrospective study done in a small patient population, and that it needs verification in larger prospective studies.