Feasibility of a Novel Augmented 6-Minute Incremental Step Test: A Simplified Cardiorespiratory Fitness Assessment Tool

Jeroen Molinger; Veraprapas Kittipibul; J Matthew Gray; Vishal N Rao; Stratton Barth; Ashley Swavely; Brian Coyne; Aubrie Coburn; Jan Bakker; Paul E Wischmeyer; Cynthia L Green; David MacLeod; Manesh Patel; Marat Fudim

doi:10.1016/j.jacadv.2024.101079

Feasibility of a Novel Augmented 6-Minute Incremental Step Test: A Simplified Cardiorespiratory Fitness Assessment Tool

JACC Adv. 2024 Jul 8;3(8):101079. doi: 10.1016/j.jacadv.2024.101079. eCollection 2024 Aug.

Authors

Jeroen Molinger^{1

2

3}, Veraprapas Kittipibul^{1

4}, J Matthew Gray¹, Vishal N Rao^{1

4}, Stratton Barth², Ashley Swavely¹, Brian Coyne¹, Aubrie Coburn¹, Jan Bakker^{5

6}, Paul E Wischmeyer³, Cynthia L Green^{4

7}, David MacLeod^{2

3}, Manesh Patel^{1

4}, Marat Fudim^{1

4}

Affiliations

¹ Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA.
² Human Pharmacology & Physiology Lab, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.
³ Division of Critical Care, Department of Anesthesiology, Duke University School of Medicine, Durham, North Carolina, USA.
⁴ Duke Clinical Research Institute, Durham, North Carolina, USA.
⁵ Department of Intensive Care Adults, Erasmus MC University Medical Center, Rotterdam, The Netherlands.
⁶ Department of Medicine, NYU Grossman School of Medicine, New York, New York, USA.
⁷ Department of Biostatistics & Bioinformatics, Duke University School of Medicine, Durham, North Carolina, USA.

Abstract

Background: The cardiopulmonary exercise test (CPET) is considered a gold standard in assessing cardiorespiratory fitness (CRF) but has limited accessibility due to competency requirements and cost. Incorporating portable sensor devices into a simple bedside test of CRF could improve diagnostic and prognostic value.

Objectives: The authors sought to evaluate the association of an augmented 6-minute incremental step test (6MIST) with standard CPET.

Methods: We enrolled patients undergoing clinically indicated supine cycle ergometry CPET with invasive hemodynamics (iCPET) for the same-day 6MIST. CRF-related variables were simultaneously recorded using a signal morphology-based impedance cardiograph (PhysioFlow Enduro) and a portable metabolic analyzer (VO₂ Master Pro) during incremental pace stationary stepping. The correlation between CPET and hemodynamic parameters from both tests was assessed using the intraclass correlation coefficient (ICC).

Results: Fifteen patients (mean age 60 ± 14 years, 40% female, 27% Black) were included. All patients who agreed to undergo 6MIST completed the study without any test-related adverse events. We observed good to excellent correlation between iCPET- and 6MIST-measured CPET parameters: peak heart rate (ICC = 0.60; 95% CI: 0.15-0.85), absolute peak O₂ consumption (VO₂) (ICC = 0.77; 95% CI: 0.44-0.92), relative peak VO₂ (ICC = 0.64; 95% CI: 0.20-0.86), maximum ventilation (ICC = 0.59; 95% CI: 0.13-0.84), O₂ pulse (ICC = 0.71; 95% CI: 0.33-0.89), and cardiorespiratory optimal point (ICC = 0.82; 95% CI: 0.52-0.94). No significant correlation was determined between iCPET and 6MIST in measuring cardiac index at rest (ICC = 0.19; 95% CI: -0.34 to 0.63) or at peak exercise (ICC = 0.36; 95% CI: -0.17 to 0.73).

Conclusions: We demonstrate the feasibility of a novel augmented 6MIST with wearable devices for simultaneous CPET and hemodynamic assessment. 6MIST-measured CPET parameters were strongly correlated with the iCPET-derived measurements. Additional studies are needed to confirm the validity of the 6MIST compared to standard upright CPET.

Keywords: 6-minute incremental step test; cardiopulmonary exercise test; cardiorespiratory fitness; wearable devices.