Cardiac aliasing in atrial rate variation response to fixed-rate ventricular pacing

Abstract

It is found that the frequency components of atrial rate variation (ARV) of A V-block patient with fixed-rate ventricular pacing valy irregularly with the pacing rates.We attempt to learn about the relationship between the oscillation frequency of AR V and the blood pressure (BP) pattern in this study.The beat-to-beat AR Vs extracted from esophageal ECG and noninvasive BP waveforms of seven AV-block patients were recorded. Each patient was paced under 60, 90, 120 beatdmin of three ventricular rates. Results reveal that the oscillation frequency of ARV does not correlate to the variation frequency of systolic or diastolic BP or respiration frequenc.y. Instead, it may be an aliasing phenomenon of BP pulse frequency exactly equal to ventricular rate when the mean atrial rate is considered as the sample rate of ARV signal. This study suggests that the BP pulse dominate the ARV in AV asynchronous situation IntroductionTwo main frequency components of heart rate variation (HRV) in low frequency (0.04-0.15 Hz) and high frequency (0.15-0.4 Hz) bands, respectively, have been identified and used to clinical assessment of autonomic balance in cardiac control. The high frequency oscillation of HRV correlating to the respiration has been verified. But the origin of low frequency oscillation is more complicated and still under investigation.The heart rate variation expresses the dynamics in the feedback system of heart rate control. To observe the atrial rate variability (ARV) of AV-block patient paced with different fixed ventricular pacing rate will help to understand the heart rate control mechanism. Recently, we have used the PP intervals on an esophageal lead for analysis of ARV in patients with AV block [ 11. It was shown that AV block patients had ARV differing from normal subjects. Some studies also have reported that ventricular rate and AV-delay have marked influences on ARV [2-41. Moreover, we found that the frequency components of ARV of AV-block patient with fixed-rate ventricular pacing vary irregularly with the pacing rates in a pilot study [5]. Hence we hardly figured out any conclusion for the influences of ventricular rates and AVdelays to ARV. Some evidences have reveal that the blood pressure (BP) variations play an important role in HRV [6,7]. Therefore, we attempt to learn about the relationship between the oscillation frequency of ARV and the BP pattern in this study. 2.Materials and methods PatientsSeven AV block patients loaded with VDD pacemakers were included in this study. All these patients demonstrated normal atrial activity in surface ECG and absence of ventriculo-atrial conduction during ventricular pacing. Patients lay on a table and breathed normally. During the whole experimental procedure, the breathing rate had no marked change. MethodsAn esophageal lead was used to non-invasively record the atrial ECG. PP intervals on the atrial ECG were acquired with the method used in a previous studyThe ARVs of each patient at three different fixed ventricular pacing rates (VVI mode, 60, 90 and 120 bp...

Applying independent component analysis to heart rate and blood pressure variations

“…The lead II surface ECG and NICBP were simultaneously recorded and sampled at 500 Hz for further processing. The experimental procedure was described in previous work [9].…”

The interaction of heart rate and blood pressure variations for av dissociation illustrated by a closed-loop heart rate control model

“…It is found that the dominant frequency of ARV is an aliasing of ventricular pacing rate while considering the mean atrial rate as the sampling rate [6]. It is suggested that the BP pulse rate and waveform play an important role for this phenomenon.…”

“…Some studies was reported that ventricular rate and AV-delay have marked influences on ARV [2,3] Moreover, some evidences have shown that beat-to-beat blood pressure (BP) variation (BPV) may play a role for this phenomenon [4,5]. In our later investigation [6], we found that the oscillation frequency of ARV may be an aliasing phenomenon of BP pulse frequency exactly equal to ventricular rate when the mean atrial rate is considered as the sample rate of ARV signal. Hence we suggested that the BP pulse dominate the ARV in AV dissociation situation.…”

“…The real BP waveform was transformed to be the modulation signal m(t) according to equation (2) to generate the simulated ARV. The real ARV and BP data of reference [6] were used to simulate and compare. Because the mean HR of each experiment is different, the constants a and b were tuned to generate the ARV with a similar mean HR to real ARV.…”