Abstract
Oscillations of arterial pressure occur spontaneously at a frequency of approximately 0.1 Hz coupled with synchronous oscillations of sympathetic nerve activity (“Mayer waves”). This study investigated the extent to which corresponding oscillations may occur in ventricular action potential duration (APD). Fourteen ambulatory (outpatient) heart failure patients with biventricular pacing devices were studied while seated upright watching movie clips to maintain arousal. Activation recovery intervals (ARI) as a measure of ventricular APD were obtained from unipolar electrograms recorded from the LV epicardial pacing lead during steady state RV pacing from the device. Arterial blood pressure was measured non-invasively (Finapress) and respiration monitored. Oscillations were quantified using time frequency and coherence analysis. Oscillatory behavior of ARI at the respiratory frequency was observed in all subjects. The magnitude of the ARI variation ranged from 2.2 to 6.9 ms (mean 5.0 ms). Coherence analysis showed a correlation with respiratory oscillation for an average of 43% of the recording time at a significance level of p < 0.05. Oscillations in systolic blood pressure in the Mayer wave frequency range were observed in all subjects for whom blood pressure was recorded (n = 13). ARI oscillation in the Mayer wave frequency range was observed in 6/13 subjects (46%) over a range of 2.9 to 9.2 ms. Coherence with Mayer waves at the p < 0.05 significance level was present for an average of 29% of the recording time. In ambulatory patients with heart failure during enhanced mental arousal, left ventricular epicardial APD (ARI) oscillated at the respiratory frequency (approximately 0.25 Hz). In 6 patients (46%) APD oscillated at the slower Mayer wave frequency (approximately 0.1 Hz). These findings may be important in understanding sympathetic activity-related arrhythmogenesis.
Highlights
Oscillatory activity is a ubiquitous property of autonomic nerves innervating the heart, and is considered by some to facilitate synchronization of nerve traffic and potentiate the response
Oscillations in action potential duration (APD) were present for all subjects at the respiratory frequency which were strongly correlated with respiration
Oscillations in APD were present at a slower frequency in a proportion of subjects which were coupled with systolic blood pressure oscillations
Summary
Oscillatory activity is a ubiquitous property of autonomic nerves innervating the heart, and is considered by some to facilitate synchronization of nerve traffic and potentiate the response. Since sympathetic nerves are known to innervate ventricular myocardium, and elicit changes in the potassium and calcium channels, both of which are important components of the cardiac action potential, it is possible that oscillations in APD may occur at this slower frequency (Zipes and Jalife, 1999; Workman, 2010; Taggart et al, 2011; Shen and Zipes, 2014). To the authors’ knowledge, variation of APD in synchronization with Mayer waves has not been reported
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