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Abstract
Background Heart-rate recovery during the first minute of rest (HRR1) after a six minute walk test (6MWT) has been shown to be a strong predictor of clinical worsening in patients with pulmonary arterial hypertension.1 No data as yet has been published regarding the utility of HRR1 as a predictor of mortality.
Aim To assess the prognostic value of HRR1 after an Incremental Shuttle Walk Test (ISWT) in patients with pulmonary hypertension (PH).
Methods Data was retrieved for consecutive cases of PH diagnosed in our unit from 2001–2010. ISWT was performed routinely as part of baseline assessment according to a modified protocol of Singh et al.2 Only treatment-naive patients with ISWT and HRR data from -90 to +30 days from date of diagnosis were included. HRR1 was defined as the difference between maximum heart rate during the ISWT and heart rate after 1 min of rest following the termination of ISWT.
Results Data was available for 491 patients (including patients from each of the 5 main PH diagnostic groups). HRR1 correlated significantly with ISWT distance, highest heart-rate, maximal change in heart-rate,% predicted carbon monoxide diffusion (DLco%pred), pulmonary vascular resistance, cardiac output and mixed venous oxygen saturation (p all ≤0.01).
Using a cut-off point of 18bpm the Kaplan Meier graph for survival for patients with HRR1 >18 bpm (n = 179) was significantly better than HRR1 ≤18 bpm (n = 312), p = 0.007 (Figure 1) for all patients and for diagnostic Groups 1 and 2 separately (p = 0.045, p = 0.006).
Using univariate Cox proportional hazard analysis for all patients HRR1 (continuous data) had a Hazard Ratio for mortality (HR) of 0.990 with a confidence interval (CI) of 0.962–0.997, p = 0.008. Compared to patients with HRR1 >18, those with HRR1≤18 had a HR of 1.559 (CI 1.127–2.156) p = 0.007.
Grouping patients by median distance walked and HRR1–18 demonstrated that the HRR1 proved a useful predictor only in patients who walked less than 180 m.
Conclusion HRR1 following ISWT predicts outcome in patients with pulmonary hypertension with more severe disease.
References
1Minai OA et al. Am J Respir Crit Care Med. 2012;185:400-408
Singh et al. Thorax 1992;47:1019–1024
