Agreement between ultrashort-term and long-term heart rate variability based on 24-hour Holter monitoring

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Abstract Introduction Heart rate variability (HRV) measured for 24 hours (long-term HRV) serves as the clinical gold standard in the risk stratification of patients with comorbidities such as myocardial infarction, stroke, multiple sclerosis, end stage renal disease, and diabetic neuropathy. Previous studies explored the utility of ultra-short (US) HRV, measured for less than five minutes which could be used for bedside prognostication, for future research, or as a cheaper diagnostic alternative. Purpose This study determined the agreement between US-HRV and long-term HRV based on 24-hour holter monitoring results at a tertiary Filipino hospital. It also found the agreement in the US-HRV and long-term HRV by time of day and condition, age, sex, comorbidities, and by ability to detect abnormal HRV. Methods Tracings of 24-hour holter monitoring from January 2017 and December 2019 were reviewed. Excluded from the study were those who had arrhythmias or were taking medications affecting the autonomic nervous system. Samples of three-minute excerpts were obtained at 7am (daytime, awake), 12nn (daytime, awake, with activity), 7pm (evening, awake), and 12mn (evening, asleep). RR intervals were measured and HRV through SDNN and RMSSD were determined. Interclass correlation coefficient and kappa statistic were used to analyze the agreement between values of US and long-term HRV. Bland-Altman plots were constructed, and the limits of agreement (LOA) were reported. Kappa statistic was used to determine the agreement between the two methods in detecting abnormal HRV. Results A total of 92 results were reviewed for this study, with most patients having hypertension. Results showed that US-HRV by SDNN underestimates HRV by 47.35 to 60.58 ms (mean difference). The average discrepancy was found to be highest during daytime, awake with activity. Meanwhile, US-HRV by RMSSD was found to overestimate HRV by −29.86 to −85.24 ms (mean difference). The average discrepancy was found to be highest during evening, awake. There is poor agreement between SDNN and RMSSD measured using long-term HRV and US-HRV in all four samples, even with age, gender, and comorbidities factored in. Likewise, there is poor agreement between US-HRV and long-term HRV values in detecting abnormal HRV. At best, evening US-HRV RMSSD values have moderate agreement in detecting abnormal US-HRV. However, the study was done in a less controlled environment. Also, long-term time-domain variables (RMSSD and SDNN) are known to reflect circadian rhythms and the overall change in the autonomic nervous system, hence three-minute measurements might poorly reflect changes occurring in the autonomic nervous systems. Conclusion There is poor agreement between three-minute US-HRV and long-term HRV obtained through 24-hour holter monitoring. Studies done in a more controlled environment are recommended. Funding Acknowledgement Type of funding sources: None.