Key result
LVET provides better autonomic space than PEP, evidenced by weaker CAB and CAR correlations.
Why the study?
Impedance-derived cardiac autonomic balance and regulation combine chronotropic parasympathetic and inotropic sympathetic measures, whereas left ventricular ejection time is a sympathetic chronotropic measure that may be more appropriate than pre-ejection period.
Does calculating CAB and CAR using LVET compared to PEP provide more independent measures of cardiac autonomic activity in healthy young adults?
Observational (n=158)
No
Does calculating CAB and CAR using LVET compared to PEP provide more independent measures of cardiac autonomic activity in healthy young adults?
Calculating cardiac autonomic balance and regulation using chronotropic measures for both parasympathetic and sympathetic activity (LVET) yields more independent measures than mixing inotropic (PEP) and chronotropic measures.
Answers are grounded in this paper and cite their sources.
LVET may yield more independent CAB and CAR than PEP in young adults; leaves open utility for clinical autonomic assessment.
Traditionally, impedance derived measures of cardiac autonomic balance (CAB) and regulation (CAR) are calculated using indices of heart rate variability (HRV) that primarily reflect parasympathetic nervous system activity (e.g., high-frequency HRV | HF-HRV) and pre-ejection period (PEP; a systolic time interval and measure of sympathetic activity). However, HF-HRV and PEP are considered measures of chronotropic and inotropic cardiac influence, respectively. Left ventricular ejection time (LVET) is a systolic time interval that reflects sympathetic chronotropic influence, and therefore may be a more appropriate measure for calculating CAB and CAR compared to PEP. Thus, the current study evaluates both PEP and LVET in the calculation of CAB and CAR. Data from 158 healthy participants (mean age = 19.09 years old, SD = 1.84 years) were available for analyses. CAB and CAR values were calculated using both HF-HRV and the root mean square of successive differences, in addition to both PEP and LVET, in accordance with previously established guidelines. Analyses showed that correlations were significantly weaker between CAB and CAR calculated using LVET for both HF ( z = 5.12, p < 0.001) and RMSSD ( z = 5.26, p < 0.001) than with PEP. These data suggest that LVET, compared to PEP, provides better “autonomic space” as evidenced by a lack of correlation between CAB and CAR computed using LVET. We stress that future research consider calculating CAB and CAR using chronotropic measures for both parasympathetic and sympathetic activity, as doing so may yield more accurate and independent measures of cardiac autonomic activity compared to a mixture of inotropic (i.e., PEP) and chronotropic (i.e., HF-HRV) measures.
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Wiley et al. (2021) conducted an observational in Healthy participants (n=158). Left ventricular ejection time (LVET) vs. Pre-ejection period (PEP) was evaluated on Correlation between cardiac autonomic balance (CAB) and cardiac autonomic regulation (CAR) calculated using high-frequency heart rate variability (HF) (z = 5.12, p=<0.001). Left ventricular ejection time provided better autonomic space than pre-ejection period, as evidenced by weaker correlations between cardiac autonomic balance and regulation.
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