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Evaluating heart rate variability by a novel stethoscopic approach to minimise stress in cats
Chi-Ru Chen1,2, Wei-Tao Chang1,2, Hui-Wen Chen3,4
1National Taiwan University Veterinary Hospital, National Taiwan University, Taipei, Taiwan.
Insights
A novel stethoscopic method accurately assesses feline heart rate variability (HRV) and vasovagal tonus index (VVTI). This cat-friendly approach reduces stress during autonomic function evaluation in veterinary medicine.
Area of Science:
- Veterinary Cardiology
- Animal Physiology
Background:
- Electrocardiography (ECG) for heart rate variability (HRV) in cats can be stressful.
- Stress during recording may limit accurate assessment of autonomic function.
- An alternative, less invasive method is needed for feline HRV evaluation.
Purpose of the Study:
- To evaluate a cat-friendly stethoscopic approach for assessing HRV.
- To determine if the vasovagal tonus index (VVTI) derived from heart sounds can differentiate between relaxed and stimulated states in cats.
- To establish a less stressful method for autonomic function assessment in felines.
Main Methods:
- Prospective study involving 29 cats with 56 recordings.
- Heart sounds recorded using a stethoscope during relaxed and stimulated states in home and hospital settings.
- Vasovagal tonus index (VVTI) calculated from heart sound spectrograms (stethoscopic-VVTI).
- Comparison with ECG-derived VVTI using Bland-Altman analysis.
Main Results:
- Stethoscopic-VVTI significantly decreased after stimulation, indicating reduced vasovagal tone.
- Calculations from different recording sections yielded similar results.
- Stethoscopic-VVTI showed a negative correlation with heart rate.
- Mean bias between stethoscopic-VVTI and ECG-VVTI was observed.
Conclusions:
- The vasovagal tonus index (VVTI) can be reliably detected using a stethoscopic approach.
- This method offers a less stressful alternative for HRV evaluation in cats.
- The stethoscopic method is suitable for routine auscultation and autonomic function assessment in feline patients.
Objectives:
Stress associated with manipulation during electrocardiography (ECG) recording in cats potentially limits the assessment of autonomic function through heart rate variability (HRV) in the feline population. This study proposed an alternative, cat friendly, stethoscopic approach to evaluate HRV with an easily acquired vasovagal tonus index (VVTI).
Methods:
The aim of this prospective study was to evaluate whether VVTI derived from heart sound signals could distinguish between relaxed and stimulated states. A total of 29 cats with 56 recordings of heart sound and ECG on 31 occasions were included. In 25 cats in their home environment, a stethoscope connected to a digital recording device was used to record 2 mins of heart sounds twice - with the cats in a relaxed state and immediately after stimulation. The VVTI was calculated from 20, 60 and 120 consecutive beat-to-beat intervals on the heart sound spectrogram (stethoscopic-VVTI 20, 60 and 120), using the natural logarithm of the variance of the intervals based on previous literature. A 2-min ECG recording was obtained at home with the intention of avoiding strict restraint. To demonstrate the feasibility of the stethoscopic approach in a hospital setting, six cats (two of which were also recorded at home) underwent heart sound and ECG recordings during planned veterinary visits.
Results:
Stethoscopic-VVTI 20 (5.43 to 4.79, P = 0.001), 60 (6.20 to 5.18, P <0.001) and 120 (6.24 to 5.60, P = 0.02) all significantly decreased after stimulation, indicating a reduced vasovagal tone as expected. Calculations of stethoscopic-VVTI from different sections of the recording yielded statistically similar results. Stethoscopic-VVTI showed a negative correlation with the corresponding heart rate. Bland-Altman analysis revealed a mean bias for the differences between stethoscopic-VVTI and ECG-VVTI of 0.50 and 1.07 at home and in the hospital, respectively.
Conclusions And Relevance:
VVTI can be successfully detected through a stethoscopic approach, serving as a less stressful tool for HRV evaluation in cats during routine auscultation.
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