Variability of Ventricular Excitation Interval Does Not Reflect Fluctuation in Atrial Excitation Interval during Exercise in Humans: AV Nodal Function as Stabilizer

Nakamoto, Tomoko; Matsukawa, Kanji

doi:10.2170/physiolsci.rp002705

Cited by 2 publications

(14 citation statements)

References 24 publications

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“…Indeed, when HR approached 90–100 beats min −1 , the variance of the R–R interval became much smaller than that of the P–P interval during stair‐stepping exercise (Nakamoto et al . ) and cycle ergometer exercise (Nakamoto & Matsukawa, ), despite the same shortened average interval. As expected, the HF component of R–R interval variability was smaller during dynamic exercise than that of P–P interval variability (Fig.…”

Section: Discussionmentioning

confidence: 93%

“…R–R interval) was modulated by the atrioventricular node (Nakamoto et al . ; Nakamoto & Matsukawa, ). Indeed, when HR approached 90–100 beats min −1 , the variance of the R–R interval became much smaller than that of the P–P interval during stair‐stepping exercise (Nakamoto et al .…”

Section: Discussionmentioning

confidence: 98%

“…The P( k ) and R( k ) in the k th beat represented the onset time of the k th P wave and the peak time of the k th QRS complex, respectively. The onsets and peaks of P wave and QRS complex were automatically recognized as specific flags every heart beat with customized Fluclet ® WT software (Dainippon Pharmaceutical, Osaka, Japan; Nakamoto & Matsukawa, ). The assigned flags were searched on a computer screen over all heart beats recorded.…”

Section: Methodsmentioning

confidence: 99%

“…We have recently demonstrated a strong inverse relationship between the P–P interval and the subsequent changes in P–R interval (∆PR) within the same beat during exercise (Nakamoto et al . ; Nakamoto & Matsukawa, ). The opposite change in atrioventricular (AV) conduction time may cancel beat‐to‐beat fluctuation in the preceding atrial excitation rhythm (i.e.…”

Section: Introductionmentioning

confidence: 98%

“…Given that a substantial variability of P–P interval remained when HR increased at an HR of 120–140 beats min −1 (Nakamoto et al . ; Nakamoto & Matsukawa, ), it will be expected that the HF component of P–P interval variability does not vanish during moderate‐intensity exercise. To test the hypothesis, the power spectrum of P–P interval variability during exercise was analysed using a Wavelet transform in humans, which allowed us to assess the dynamic changes in heart rate variability (HRV; Wiklund et al .…”

Section: Introductionmentioning

confidence: 99%

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Cardiac parasympathetic outflow during dynamic exercise in humans estimated from power spectral analysis of P–P interval variability

Takahashi

Nakamoto

Matsukawa

et al. 2016

Experimental Physiology

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New Findings r What is the central question of this study?Should we use the high-frequency (HF) component of P-P interval as an index of cardiac parasympathetic nerve activity during moderate exercise? r What is the main finding and its importance?The HF component of P-P interval variability remained even at a heart rate of 120-140 beats min −1 and was further reduced by atropine, indicating incomplete cardiac vagal withdrawal during moderate exercise. The HF component of R-R interval is invalid as an estimate of cardiac parasympathetic outflow during moderate exercise; instead, the HF component of P-P interval variability should be used.The high-frequency (HF) component of R-R interval variability has been widely used as an indirect estimate of cardiac parasympathetic (vagal) outflow to the sino-atrial node of the heart. However, we have recently found that the variability of the R-R interval becomes much smaller during dynamic exercise than that of the P-P interval above a heart rate (HR) of ß100 beats min −1 . We hypothesized that cardiac parasympathetic outflow during dynamic exercise with a higher intensity may be better estimated using the HF component of P-P interval variability. To test this hypothesis, the HF components of both P-P and R-R interval variability were analysed using a Wavelet transform during dynamic exercise. Twelve subjects performed ergometer exercise to increase HR from the baseline of 69 ± 3 beats min −1 to three different levels of 100, 120 and 140 beats min −1 . We also examined the effect of atropine sulfate on the HF components in eight of the 12 subjects during exercise at an HR of 140 beats min −1 . The HF component of P-P interval variability was significantly greater than that of R-R interval variability during exercise, especially at the HRs of 120 and 140 beats min −1 . The HF component of P-P interval variability was more reduced by atropine than that of R-R interval variability. We conclude that cardiac parasympathetic outflow to the sino-atrial node can be estimated better by the HF component of P-P interval variability during exercise and that cardiac parasympathetic nerve activity exists during moderate dynamic exercise.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Cardiac parasympathetic outflow during dynamic exercise in humans estimated from power spectral analysis of P–P interval variability

Takahashi

Nakamoto

Matsukawa

et al. 2016

Experimental Physiology

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Control of heart rate variability by cardiac parasympathetic nerve activity during voluntary static exercise in humans with tetraplegia

Takahashi¹,

Matsukawa²,

Nakamoto³

et al. 2007

Journal of Applied Physiology

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Heart rate (HR) is controlled solely by via cardiac parasympathetic outflow in tetraplegic individuals, who lack supraspinal control of sympathetic outflows and circulating catecholamines but have intact vagal pathways. A high-frequency component (HF; at 0.15-0.40 Hz) of the power spectrum of HR variability and its relative value against total power (HF/Total) were assessed using a wavelet transform to identify cardiac parasympathetic outflow. The relative contribution of cardiac parasympathetic and sympathetic outflows to controlling HR was estimated by comparing the HF/Total-HR relationship between age-matched tetraplegic and normal men. Six tetraplegic men with complete cervical spinal cord injury performed static arm exercise at 35% of the maximal voluntary contraction until exhaustion. Although resting cardiac output and arterial blood pressure were lower in tetraplegic than normal subjects, HR, HF, and HF/Total were not statistically different between the two groups. When tetraplegic subjects developed the same force during exercise as normal subjects, HF and HF/Total decreased to 67-90% of the preexercise control and gradually recovered 1.5 min after exercise. The amount and time course of the changes in HF/Total during and after exercise coincided well between both groups. In contrast, the increase in HR at the start of exercise was blunted in tetraplegic compared with normal subjects, and the HR recovery following exercise was also delayed. It is likely that, although the withdrawal response of cardiac parasympathetic outflow is preserved in tetraplegic subjects, sympathetic decentralization impairs the rapid acceleration of HR at the onset of exercise and the rapid deceleration following exercise.

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Variability of Ventricular Excitation Interval Does Not Reflect Fluctuation in Atrial Excitation Interval during Exercise in Humans: AV Nodal Function as Stabilizer

Cited by 2 publications

References 24 publications

Cardiac parasympathetic outflow during dynamic exercise in humans estimated from power spectral analysis of P–P interval variability

Cardiac parasympathetic outflow during dynamic exercise in humans estimated from power spectral analysis of P–P interval variability

Control of heart rate variability by cardiac parasympathetic nerve activity during voluntary static exercise in humans with tetraplegia

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