Unlocking high-intensity performance thresholds through ventilatory signatures in the ECG

Area of Science:

• Exercise Physiology
• Cardiopulmonary Exercise Testing
• Biomedical Engineering

Background:

• Accurate non-invasive ventilatory threshold assessment (NIVA) is crucial for evaluating performance in clinical and sports settings.
• Current methods for determining the second ventilatory threshold (VT2) often require invasive or complex procedures like spiroergometry or lactate sampling.
• Developing a widely accessible and accurate NIVA method is a significant unmet need.

Purpose of the Study:

• To investigate the accuracy of ECG-derived ventilatory phase analysis for determining the second ventilatory threshold (VT2).
• To compare the NIVA-derived threshold with traditional methods, including VT2 from cardiopulmonary exercise testing (CPET) and lactate-based thresholds (LT2).
• To assess the agreement between NIVA and VT2 for heart rate (HR) and exercise load (W).

Main Methods:

• Seventy-four healthy adults underwent stepwise CPET with simultaneous lactate sampling.
• The second ventilatory threshold (VT2) and lactate-based thresholds (LT2) were determined.
• ECG-derived ventilatory phase analysis (NIVA) was employed to estimate the ventilatory threshold, and results were compared with VT2, LT2, and age-estimated HR (HR-Est).

Main Results:

• NIVA demonstrated high accuracy, yielding threshold estimates for HR and exercise load that closely agreed with CPET-derived VT2 (HR: -0.46 bpm; Load: 0.46 W).
• Significant differences were observed between VT2 and HR-Est (HR: -7.22 bpm; Load: -6.26 W).
• LT2, available in 58 subjects, differed significantly from both VT2 and NIVA (p < 0.001).

Conclusions:

• ECG-derived NIVA provides a non-invasive method for determining a high-intensity performance threshold with reference-standard fidelity, closely matching CPET-derived VT2.
• NIVA's performance and accessibility make it a valuable tool for frequent performance reassessment without the need for spiroergometry or lactate measurements.
• Further validation of NIVA across diverse devices, protocols, populations, and real-world conditions is warranted.