PURPOSE: The usefulness of the six minute walk test (6MWT) as a clinical endpoint to assess pulmonary arterial hypertension (PAH) severity has been questioned. Distance walked during an incremental shuttle walk test (ISWT), an incremental, symptom-limited walk test, studied in COPD and cardiomyopathy, seems to correlate with VO2 max. and dyspnea. We wished to determine whether the ISWT could be performed easily and safely in a PAH population which included advanced WHO functional class (FC) or right ventricular dysfunction (RVD).
METHODS: We retrospectively reviewed the charts of patients with PAH (WHO Groups I and IV) who had undergone ISWTs between 3/2009 and 12/2010. Eighty-two ISWTs from 46 patients were reviewed for WHO functional class (FC), distance walked, heart rate and adverse events (AEs). ISWTs in each FC: FC 1 - 7, FC 2 - 35, FC 3 - 33, and FC 4 - 7.
RESULTS: A total of 22 AEs occurred. CREST/SCL (8/18), Idiopathic (4/23), Porto-pulmonary (2/8), HIV (2/2), Drug-induced (3/8), and Autoimmune hemolysis (3/6) accounted for AEs during ISWTs. Two patients developed angina and 6 described lightheadedness, all self-remitting within minutes of completion. Fourteen described musculoskeletal events during testing (pain or heaviness in hips or legs); one patient stumbled. There were no falls, deaths or sustained AEs. 51/82-conducted ISWTs were associated with RVD by echocardiogram. 8/22 AEs were associated with RVD. RVD with FC 3 & 4 accounted for 29/82 (35.3 %) ISWTs, and accounted for 12 of 22 (54.5 %) of adverse events.
CONCLUSIONS: ISWTs in patients with advanced COPD have shown significant tachycardia in comparison to 6MWT, leading to a fear of adverse cardiac events in those with RVD. Our population of patients included patients with FC 3 and 4 and RVD who underwent ISWT without development of syncope or sustained tachycardia. The observed adverse musculoskeletal events did not to lead to fall or injury. ISWT may not be appropriate for patients with CREST/SCL, given the observed high proportion of musculoskeletal AEs.
CLINICAL IMPLICATIONS: As part of a routine outpatient evaluation for PAH, the ISWT appears to be feasible and safe, even in patients with advanced FC or RVD. Musculoskeletal AEs may limit its usefulness in some patients. The ISWT should be compared prospectively with the 6MWT in future trials to determine its suitability as a clinical endpoint in patients with PAH.
DISCLOSURE: The following authors have nothing to disclose: Sidharth Bagga, Michael Scharf, Vipul Kumar
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