Heart Rate Irregularity Research Articles

Post-diphtheritic Polyneuropathy in Children with Diphtheria: A Prospective Observational Study

This study aimed to determine the proportion of diphtheria patients who develop post-diphtheritic polyneuropathy (DP) later on and also to study the clinical features and outcomes of children with post-DP. This prospective observational study was conducted at the Department of Pediatrics, King George’s Medical University, Lucknow, Uttar Pradesh, India. Children under 14 hospitalized with clinically diagnosed diphtheria and post-DP were recruited (n = 81). Detailed clinical examination with appropriate investigations was conducted, including throat swabs for staining and culture for Corynebacterium diphtheria, nerve conduction studies, electrocardiography, and echocardiography. The data were analyzed using Statistical Package for Social Sciences (SPSS) version 16.0. Seventy-four cases of diphtheria and seven cases of post-DP were enrolled, 56.8% were male, and the most prevalent age group afflicted was two to five years. Fifty-three children (65.4%) were partially immunized for diphtheria. Neck swelling, voice change, difficulty breathing, noisy breathing, respiratory involvement, and stridor were significantly more common in the unimmunized group. Voice change, heart rate irregularity, and hypotension were substantially more common in patients who developed clinical neuropathy than those who did not. Early administration of antibiotics in children with diphtheria before hospital admission was found to be significant in those children who did not develop clinical polyneuropathy, 38.5% of diphtheria survivors had abnormal nerve conduction study at six weeks of illness. Neck swelling and change in voice were significantly more common in patients with abnormal nerve conduction velocity (NCV) than in normal nerve conduction studies, 87.5% of children who had taken antibiotics before hospital admission had no clinical neuropathy, and NCV was also normal. Clinical neuropathy developed in just 20% of diphtheria patients with impaired NCV. Any child diagnosed with diphtheria should be followed for three to six months in anticipation of neurological complications. DP carries a good prognosis; hence, timely diagnosis and differentiation from other neuropathies is a prerequisite for rational management.

Design and Implementation of an Atrial Fibrillation Detection Algorithm on the ARM Cortex-M4 Microcontroller.

At present, a medium-level microcontroller is capable of performing edge computing and can handle the computation of neural network kernel functions. This makes it possible to implement a complete end-to-end solution incorporating signal acquisition, digital signal processing, and machine learning for the classification of cardiac arrhythmias on a small wearable device. In this work, we describe the design and implementation of several classifiers for atrial fibrillation detection on a general-purpose ARM Cortex-M4 microcontroller. We used the CMSIS-DSP library, which supports Naïve Bayes and Support Vector Machine classifiers, with different kernel functions. We also developed Python scripts to automatically transfer the Python model (trained in Scikit-learn) to the C environment. To train and evaluate the models, we used part of the data from the PhysioNet/Computing in Cardiology Challenge 2020 and performed simple classification of atrial fibrillation based on heart-rate irregularity. The performance of the classifiers was tested on a general-purpose ARM Cortex-M4 microcontroller (STM32WB55RG). Our study reveals that among the tested classifiers, the SVM classifier with RBF kernel function achieves the highest accuracy of 96.9%, sensitivity of 98.4%, and specificity of 95.8%. The execution time of this classifier was 720 μs per recording. We also discuss the advantages of moving computing tasks to edge devices, including increased power efficiency of the system, improved patient data privacy and security, and reduced overall system operation costs. In addition, we highlight a problem with false-positive detection and unclear significance of device-detected atrial fibrillation.

The hemodynamic effect of simulated atrial fibrillation on left ventricular function.

Atrial fibrillation (AF) is the most common sustained arrhythmia in humans. The onset of the arrhythmia can significantly impair cardiac function. This hemodynamic deterioration has been explained by several mechanisms such as the loss of atrial contraction, shortening of ventricular filling, or heart rhythm irregularity. This study sought to evaluate the relative hemodynamic contribution of each of these components during in vivo simulated human AF. Twelve patients undergoing catheter ablation for paroxysmal AF were paced simultaneously from the proximal coronary sinus and the His bundle region according to prescribed sequences of irregular R-R intervals with the average rate of 90and 130 bpm, which were extracted from the database of digital ECG recordings of AF from other patients. The simulated AF was compared to regular atrial pacing with spontaneous atrioventricular conduction and regular simultaneous atrioventricular pacing at the same heart rate. Beat-by-beat left atrial and left ventricular pressures, including LV dP/dT and Tau index were assessed by direct invasive measurement; beat-by-beat stroke volume and cardiac output (index) were assessed by simultaneous pulse-wave doppler intracardiac echocardiography. Simulated AF led to significant impairment of left ventricular systolic and diastolic function. Both loss of atrial contraction and heart rate irregularity significantly contributed to hemodynamic impairment. This effect was pronounced with increasing heart rate. Our findings strengthen the rationale for therapeutic strategies aiming at rhythm control and heart rate regularization in patients with AF.

Estimation of PQ distance dispersion for atrial fibrillation detection

Background and objective: Atrial fibrillation (AF) is the most common cardiac arrhythmia in the world. It is associated with significantly increased morbidity and mortality. Diagnosis of the disease can be based on the analysis of the electrical atrial activity, on quantification of the heart rate irregularity or on a mixture of the both approaches. Since the amplitude of the atrial waves is small, their analysis can lead to false results. On the other hand, the heart rate based analysis usually leads to many unnecessary warnings. Therefore, our goal is to develop a new method for effective AF detection based on the analysis of the electrical atrial waves.Methods: The proposed method employs the fact that there is a lack of repeatable P waves preceding QRS complexes during AF. We apply the operation of spatio-temporal filtering (STF) to magnify and detect the prominent spatio-temporal patterns (STP) within the P waves in multi-channel ECG recordings. Later we measure their distances (PQ) to the succeeding QRS complexes, and we estimate dispersion of the obtained PQ series. For signals with normal sinus rhythm, this dispersion is usually very low, and contrary, for AF it is much raised. This allows for effective discrimination of this cardiologic disorder.Results: Tested on an ECG database consisting of AF cases, normal rhythm cases and cases with normal rhythm restored by the use of cardioversion, the method proposed allowed for AF detection with the accuracy of 98.75% on the basis of both 8–channel and 2–channel signals of 12 s length. When the signals length was decreased to 6 s, the accuracy varied in the range of 95%−97.5% depending on the number of channels and the dispersion measure applied.Conclusions: Our approach allows for high accuracy of atrial fibrillation detection using the analysis of electrical atrial activity. The method can be applied to an early detection of the desease and can advantageously be used to decrease the number of false warnings in systems based on the analysis of the heart rate.

Eccentric hypertrophy in an animal model of mid- and long-term premature ventricular contraction-induced cardiomyopathy.

BackgroundTachycardia and heart rate irregularity are proposed triggers of premature ventricular contraction–induced cardiomyopathy (PVC-cardiomyopathy). Bigeminal premature atrial and ventricular contractions (PACs and PVCs) increase heart rate and result in rhythm irregularities but differ in their effects on ventricular synchrony. Comparing chronic bigeminal PACs with PVCs would provide insights into mechanisms of PVC-cardiomyopathy.ObjectiveTo compare the impact of chronic PACs and PVCs on ventricular hemodynamics, structure, and function.MethodsPacemakers were implanted in 27 canines to reproduce atrial (PACs, n = 7) or ventricular bigeminy (PVCs, n = 11) for 12 weeks, and compared to sham-operated animals (n = 9). Four additional animals were exposed to long-term bigeminal PVCs (48 weeks). Hemodynamic changes were assessed using a pressure-transducing catheter at baseline and 12 weeks. Cardiac remodeling was monitored by transthoracic echocardiography throughout the 12- and 48-week protocols in the respective groups.ResultsPVC group demonstrated a significant decrease in left ventricular (LV) ejection fraction and contractility (max dP/dt), impaired LV lusitropy (min dP/dt), and increase in LV dimensions and LV mass at 12 weeks without further deterioration beyond 16 weeks. Despite increased LV mass, relative wall thickness decreased, consistent with eccentric hypertrophy. No significant cardiac remodeling was noted in either sham or PAC groups at 12 weeks.ConclusionIn contrast to bigeminal PACs, PVCs result in a cardiomyopathy characterized by reduced LV ejection fraction, LV dilation, and eccentric hypertrophy that plateaus between 12 and 16 weeks. The lack of remodeling in chronic PACs suggests that tachycardia and heart rate irregularity do not play a significant role on the development of PVC-cardiomyopathy.

Free gait in a shallow pool accelerates recovery after exercise in model mice with fibromyalgia.

This study aimed to determine the effect of pool gait exercise using fibromyalgia-induced model mice. The sensory threshold, locomotive behavior, electrocardiogram, and onset time after the gait test in shallow water using male C57BL/6J mice (weight, 30–35 g; n=21) were investigated. To induce fibromyalgia in model mice, reserpine was injected intraperitoneally into wild-type mice once a day for 3 days. Subsequently, the fibromyalgia-induced model mice were randomly classified into two groups as follows: the control group (n=11) and the pool gait group (n=10). The mice in the pool gait group walked in the same cage containing shallow warm water 5 times per week. Both groups underwent sensory thresholds and video recordings to determine locomotive behaviors weekly. Further, both heart rate and video recordings for observation of a recovery after the gait test in shallow water were undertaken (control group; n=5, pool gait group; n=5). The pool gait did not affect sensory thresholds and locomotive behavior; however, in the pool gait group, both the recovery after the test, such as onset time and gait distance, were considerably better than those of the control group. Furthermore, changes in heart rate and heart rate irregularity after the test were more apparent in the control group than in the pool gait group. The free gait in a shallow pool accelerated recovery after exercise, unlike the sensory threshold.

Excessive exercise induces cardiac arrhythmia in a young fibromyalgia mouse model.

Fibromyalgia patients experience cardiovascular complications in addition to musculoskeletal pain. This study aimed to investigate the cardiac effects of a prolonged shallow water gait in a fibromyalgia-induced young mouse model. To produce a fibromyalgia mouse model, wild-type mice were administered an intraperitoneal injection of reserpine once a day for three days, and two primary experiments were performed. First, three types of gait tests were performed before and after the reserpine injections as follows: (i) 5 minutes of free gait outside the water, (ii) 1 minute of free gait in shallow warm water, and (iii) 5 minutes of free gait in shallow warm water. Second, electrocardiogram recordings were taken before and after the three gait tests. The average heart rate and heart rate irregularity scores were analyzed. Exercise-induced cardiac arrhythmia was observed at 1-minute gait in shallow water during the acute stage of induced FM in young mice. Further, both cardiac arrhythmia and a decrease in HR have occurred at 5-minute gait in shallow water at the same mice. However, this phenomenon was not observed in the wild-type mice under any test conditions. Although a short-term free gait in shallow warm water may be advantageous for increasing the motor activity of FM-model mice, we should be aware of the risk of prolonged and excessive exercise-induced cardiac arrhythmia. For gait exercises in shallow water as a treatment in FM patients. We suggest a gradual increase in exercise duration may be warranted.

Increased Overall Heart Rate Irregularity Risk by Hyperuricemia in the General Population: Results from the Korean National Health and Nutrition Examination Survey.

Background and objectives: Hyperuricemia is one of the well-known cardiovascular risk factors. There is a growing interest in the association between hyperuricemia and arrhythmia. We used the representative sample data of Korean population to study the association between hyperuricemia and heart rate irregularity (HRI) that reflects total arrhythmia. Materials and Methods: We performed weighted multivariate logistic regression analysis to assess the association between hyperuricemia and HRI. Results: Of the 10,827 subjects, 1308 (13.2%) had hyperuricemia and 130 (1%) had HRI. In the presence of hyperuricemia, HRI was three times higher than that in the absence of hyperuricemia (OR 2.98, 95% CI 1.71–5.18). The risk of HRI was highest in subjects with both hypertension and hyperuricemia. In the subgroup analysis, the association of hyperuricemia with HRI was most pronounced in the smoker group. Conclusions: Hyperuricemia was highly correlated with HRI in adult Korean representative sample data. Hyperuricemia was associated with a nearly tripled risk for HRI. Hypertension has a synergistic effect with hyperuricemia on HRI. Further research is warranted to clarify the relationship between hyperuricemia and arrhythmia and its mechanism.

Динамика сердечного ритма у индивидов при оценке и описании ими эмоционально окрашенных изображений

The aim of present research was to investigate system organization of behavior dynamics which manifests in heart rate dynamics. The participants (n=30) described 24 images which in turn appeared on a computer screen. Having described an image, the participants evaluated emotional images by valence and arousal on 9-point scales, but not earlier than one minute after describing it. Heart rate was recorded during image description. Sample entropy of the heart rate irregularity was lower for images rated as negative with high arousal, as compared to neutral images in a group of participants whose ratings of negative and neutral images differed considerably. The received results allow us to suggest that higher emotionality characteristics are connected to temporary systems dedifferentiation.

Consequences of chronic frequent premature atrial contractions: Association with cardiac arrhythmias and cardiac structural changes.

Frequent premature ventricular contractions (PVCs) can cause cardiomyopathy (CM). Postextrasystolic potentiation (PESP) and irregularity have been in implicated as triggers of PVC-CM. Because both phenomena can also be found in premature atrial contractions (PACs), it is speculated that frequent PACs have similar consequences. A single-center, retrospective study included all consecutive patients undergoing a 14-day Holter monitors (November 2014 toOctober 2016). Patients were divided into four groups by ectopy burden group 1 (<1%) and remaining by tertiles (group 2-4). Echocardiographic and arrhythmic data were compared between PAC and PVC burdens. In addition, a translational PAC animal model was used to assess the chronic effects of frequent PACs. A total 846 patients were reviewed. In contrast to PVCs, we found no difference in left ventricular ejection fraction (LVEF), end-systolic and end-diastolic dimensions and presence of CM (LVEF <50%) between different PAC groups. Multivariate regression analysis demonstrated that only PVC burden predicted low EF (odds ratio, 1.1; confidence interval, 1.03-1.13; P = .001). While there was a weak correlation between PAC burden and supraventricular tachycardia (SVT) episodes and atrial fibrillation (AF) burden (r = 0.19; P < .001), there was no correlation between PAC burden and LVEF or CM. Finally, atrial bigeminy in our animal model did not significantly decrease LVEF after 3 months. PAC burden is associated with increased AF and SVT episodes. In contrast to a high PVC burden, a high PAC burden is not associated with CM. Our findings suggest that heart rate irregularity and/or PESP may play a minimal role in the pathophysiology of PVC-CM.

Safety of Perfluorobutane (Sonazoid) in Characterizing Focal Liver Lesions.

Background:The purpose of this study was to report the safety of perfluorobutane (Sonazoid) as a vascular-phase imaging agent in characterizing focal liver lesions (FLLs).Materials and Methods:From May 2014 to April 2015, a total of 54 individuals who received Sonazoid contrast-enhanced ultrasound (CEUS) were enrolled at 5 hospitals of 4 medical centers. All individuals were included in safety evaluation. A prospective study to evaluate the adverse effect (AE) incidences after intravenous administration of Sonazoid.Results:Sonazoid was well tolerated. Treatment-emergent adverse events (TEAEs) representing AE were recorded for 13 (24.1%) patients. The most common AE was abdominal pain (9.3%), followed by heart rate irregularity (5.6%). The majority of these patients (69.2%) experienced TEAEs that were mild in intensity. Sonazoid causes no significant AEs after intravenous injection. The only noteworthy AEs are related to tolerable myalgia (3.7%), abdominal pain (1.9%), and headache (1.9%). None of the 54 patients showed serious adverse effects.Conclusion:Sonazoid shows good safety and tolerance of intravenous use during CEUS of the liver for evaluation of FLLs.

Abstract TMP89: Early Heart Rate as an Outcome Predictor in Atrial Fibrillation Related Acute Ischemic Stroke

Backgrounds: Previous studies demonstrated the association of resting heart rate with cardiovascular outcomes while there were only few evidence for patients who experienced ischemic stroke. As atrial fibrillation (AF) is characterized by rapidity and irregularity of heart rate, heart rate characteristics might be a predictor for future vascular event in patients with AF acute ischemic stroke. Methods: From a multicenter prospective registry of stroke patients, acute ischemic stroke patients with AF who admitted within 48 hours after stroke onset were included. Heart rate data during the first 24 hours after admission were collected and level and variability of heart rate were assessed by mean and coefficient of variation (CV). Primary outcome was a composite of stroke recurrence, myocardial infarction and all-cause death, which was prospectively captured until 1 year after stroke onset. Results: A total of 2,046 patients were included for the final analysis. There were 102 (5.0%) stroke recurrence, 9 (0.4%) myocardial infarction and 440 (21.5%) death events within 1 year after stroke onset. Proportional hazards regression models were constructed and the non-linearity of effects of heart rate parameters were examined for outcome events. Among all the associations, effects of mean heart rate on primary outcome and all-cause mortality were non-linear ( p’s for quadratic effect = 0.017 and 0.032, respectively). The overall effects were significant only for effects of mean heart rate on primary outcome and all-cause mortality (P =0.013 and P=0.006, respectively). Effects of CV on outcome variables were not significant. Conclusion: This study suggests that mean heart rate during the first day of hospitalization was a predictor of future vascular events in AF patients presenting with acute ischemic stroke and the association seems to be non-linear ‘J shaped’. However, heart rate variability did not affect.

Physiologically motivated detection of Atrial Fibrillation.

Atrial Fibrillation (AF) is the most common arrhythmia and it is estimated to affect 33.5 million people worldwide. AF is associated with an increased risk of mortality and morbidity, such as heart failure and stroke and affects mostly older persons and persons with other conditions (e.g. heart failure and coronary artery disease). In order to prevent such life threatening and life quality reducing conditions it is essential to provide better algorithms, capable of being integrated in low-cost personalized health systems. This paper presents a new algorithm for AF detection, which is based on the analysis of the three physiological characteristics of AF: 1) Irregularity of heart rate and; 2) Absence of P-waves and 3) Presence of fibrillatory waves. Based on these characteristics several features were extracted from 12-lead electrocardiograms (ECG) and selected according to their discrimination ability. The classification between AF and non-AF episodes was performed using a Support Vector Machine (SVM) classification model. Our results show that the identification of the fibrillatory patterns, using the proposed features, extracted from the analysis of 12-lead ECG improves the performance of the algorithm to a sensitivity of 88.5% and specificity 92.9%, when compared to our previous single-channel approach, in the same database.

Circadian variation of variability and irregularity of heart rate in patients with permanent atrial fibrillation: relation to symptoms and rate control drugs.

The aim of the present study was to evaluate diurnal variations of the variability and irregularity of heart rate (HR) in patients with permanent atrial fibrillation (AF) with and without rate control drugs. Thirty-eight patients with permanent AF were part of an investigator-blind crossover study comparing diltiazem, verapamil, metoprolol, and carvedilol. We analyzed five Holter recordings per patient: at baseline (no rate control drug) and with each of the four drug regimens. HR, variability (SD; percentages of interval differences of successive RR intervals of >20, 50, and 80 ms; and root of the mean squared differences of successive RR intervals), and irregularity (approximate and sample entropy) parameters were computed in 20-min long nonoverlapping segments. Circadian rhythmicity was evaluated using cosinor analysis to each parameter series, which is characterized by the 24-h mean [midline statistic of rhythm (MESOR)] and excursion over the mean (amplitude). Arrhythmia-related symptoms were assessed by a questionnaire measuring symptom severity and frequency. HR and variability parameters showed a significant circadian variation in most patients, whereas only a small minority of the patients had circadian variations of irregularity parameters. Patients with circadian approximate entropy n at baseline had more severe symptoms (symptom severity: 9 ± 4 vs. 6 ± 5, P < 0.05, circadian vs. noncircadian variations). All drugs decreased the MESOR of HR and increased the MESOR of variability parameters. Only carvedilol and metoprolol decreased the normalized amplitude over 24 h of all parameters and HR. In conclusion, HR and RR variability parameters present a circadian variation in patients with permanent AF, whereas few patients demonstrated circadian fluctuations in irregularity parameters, suggesting different physiological mechanisms.

High-pitch prospective ECG-triggered helical coronary computed tomography angiography in clinical practice: image quality and radiation dose.

High-pitch prospective ECG-triggered helical (PTH) protocols for coronary computed tomography angiography (CCTA) have demonstrated adequate image quality (IQ) in small-scaled studies and highly selected patients. Clinical applicability in a general clinical population is uncertain. This study evaluated the implementation of a PTH protocol in a routine clinical cohort, focusing on IQ and radiation dose. The local scientific board approved the retrospective analysis and all patients signed an informed consent statement for usage of their data. In consecutive patients suspected of coronary artery disease CCTA was performed using a dual source 128-slice scanner. All patients with a regular heart rate <65bpm underwent a PTH CCTA. IQ for each coronary segment was graded (1=absence of artifacts to 4=non-evaluable). In 664 (80.4%) of 826 included patients [mean age±standard deviation (SD) 57±11, 65% female, mean body mass index (BMI)±SD 27±9kgm(-2)] PTH CCTA was acquired whereas in 162 (19.6%) a non-PTH sequence was used. Reasons for not performing a PTH protocol were persistent high heart rate (41.6%) or heart rate irregularity (58.4%). Mean±SD heart rates for PTH and non-PTH CCTA were 55±5 and 65±9bpm, respectively, p<0.001. In the PTH group 92% of the segments were of diagnostic quality (score 1-3), versus 87% in the non-PTH group (p=0.055). Per patient, mean IQ score was 1.19 and 1.21 respectively (lower is better; p=0.012). Effective dose (including topogram, test bolus, and coronary calcium score), as calculated with a conversion factor of 0.014mSvmGy(-1)cm(-1) was 1.6±0.6 and 4.7±2.6mSv for the PTH and the non-PTH group respectively, (p<0.001). Performing high-pitch PTH sequences on a routine basis is feasible in the majority of patients with high IQ and significant reduction in radiation dose.

Short-term ECG recordings for heart rate assessment in patients with chronic atrial fibrillation.

IntroductionThere is no consensus on the length of ECG tracing that should be recorded to represent adequate rate control in patients with atrial fibrillation (AFib). The purpose of the study was to examine whether heart rate measurements based on short-term ECGs recorded at different periods of the day may correspond to the mean heart rate and rate irregularity analyzed from standard 24-hour Holter monitoring.Material and methodsThe study enrolled 50 consecutive patients with chronic AFib who underwent 24-hour Holter monitoring. Mean heart rate (mHR) and the coefficient of irregularity (CI) were assessed from 5- and 60-minute intervals of Holter recordings in different periods of the day.ResultsThe highest correlation in mean heart rate interval within 24 h was found during a 6-hour sample and in the periods 11.00 AM–12.00 PM, 12 PM–1.00 PM, and 1.00 PM–2.00 PM. With respect to irregularity, only the CI measurements based on a 6-hour interval (7.00 AM–1.00 AM) show a correlation > 0.08 compared to data from the 24-hour recording.ConclusionsOnly long-term (6-hour) recordings provide a high correlation within 24 h in mean heart rate interval and coefficient of irregularity. It seems that the mean heart rate interval in 1-hour periods between 11 AM and 2 PM might be predictive for 24-hour data. Short time recordings of the coefficient of irregularity of heart rate in AFib patients at this moment are not useful in clinical practice for long-term prognosis of ventricular irregularity.

Analysis of stability of different regimes of heart rate dynamics by computer modeling

Computer modeling revealed the following three regimes of heart rate dynamics: linear dynamics, “1st degree chaos,” and “2nd degree chaos.” This study investigated a stability of these regimes with respect to changes in initial conditions. The results show that the greatest stability is notable for the linear regime. For this regime small errors in values of initial conditions can not sharply change the initial dynamics of RR intervals. Both nonlinear regimes of heart rate dynamics are unstable, and a degree of instability of regime “2nd degree chaos” is higher in comparison with regime “1st degree chaos.” The results of computer modeling are in agreement with experimental data pointing to the existence of a relationship between the degree of heart rate irregularity and cardiac electrical stability.

Dynamic ventricular overdrive stimulation in atrial fibrillation: effects on ventricular rate irregularity, ventricular pacing, and fusion beats

In pacemaker patients with preserved atrio-ventricular (AV) conduction, atrial fibrillation (AF) can lead to symptomatic ventricular rate irregularity and loss of ventricular stimulation. We tested if dynamic ventricular overdrive (DVO) as a potentially pacemaker-integrated algorithm could improve both aspects. Different settings of DVO and ventricular-ventricular-inhibited-pacing (VVI) with different base rates were tested in two consecutive phases during electrophysiological studies for standard indications. Mean heart rate (HR), HR irregularity and percentage of ventricular pacing were evaluated. A fusion index (FI) indicative of the proportion of fusion beats was calculated for each stimulation protocol. Dynamic ventricular overdrive from the right ventricular apex was acutely applied in 38 patients (11 females, mean age 62.1 ± 11.5 years) with sustained AF and preserved AV conduction. Dynamic ventricular overdrive at LOW/MEDIUM setting increased the amount of ventricular pacing compared with VVI pacing at 60, 70, and 80 beats per minute (bpm; to 81/85% from 11, 25, and 47%, respectively; P < 0.05). It also resulted in a maximum decrease in interval differences (to 48 ± 18 ms from 149 ± 28, 117 ± 38, and 95 ± 46 ms, respectively; P < 0.05) and fusion (to 0.13 from 0.41, 0.42, and 0.36, respectively; P < 0.05) compared with VVI pacing at 60, 70, and 80 bpm. However, the application of DVO resulted in a significant increase in HR compared with intrinsic rhythm and VVI pacing at 80 bpm (to 97 bpm from 89 and 94 bpm, respectively; P < 0.05). Dynamic ventricular overdrive decreases HR irregularity and increases ventricular pacing rate compared with VVI pacing at fixed elevated base rates and spontaneous rhythm. Fusion index might help to refine information on pacing percentages provided by device counters.

Is Heart Rate Irregularity the Key to Unmasking Ventricular Proarrhythmia?

Journal of Cardiovascular ElectrophysiologyVolume 20, Issue 8 p. 880-882 Is Heart Rate Irregularity the Key to Unmasking Ventricular Proarrhythmia? SANJIV M. NARAYAN M.B., M.D., F.R.C.P., SANJIV M. NARAYAN M.B., M.D., F.R.C.P. University of California and Veterans Affairs Medical Centers, San Diego, California, USASearch for more papers by this author SANJIV M. NARAYAN M.B., M.D., F.R.C.P., SANJIV M. NARAYAN M.B., M.D., F.R.C.P. University of California and Veterans Affairs Medical Centers, San Diego, California, USASearch for more papers by this author First published: 28 July 2009 https://doi.org/10.1111/j.1540-8167.2009.01486.x Address for correspondence: Sanjiv M. Narayan, M.B., M.D., F.R.C.P., University of California and Veterans Affairs Medical Centers, San Diego Cardiology 111A, 3350 La Jolla Village Drive, San Diego, CA 92161, USA. Fax: +1-858-552-7490; E-mail: snarayan@ucsd.edu J Cardiovasc Electrophysiol, Vol. 20, pp. 880–882, August 2009. This work was supported, in part, by grants from the Doris Duke Charitable Foundation and the National Institutes of Health (R01 HL85539). Dr. Narayan has received speaking honoraria and consulting fees from St. Jude Medical, Cambridge Heart, Boston Scientific, Medtronic, Biosense-Webster, and Novartis Corporations. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume20, Issue8August 2009Pages 880-882 RelatedInformation

Persistent Atrial Fibrillation Worsens Heart Rate Variability, Activity and Heart Rate, as Shown by a Continuous Monitoring by Implantable Biventricular Pacemakers in Heart Failure Patients

Atrial fibrillation (AF) induces loss of atrial contribution, heart rate irregularity, and fast ventricular rate. The objectives of the study were to accurately measure AF incidence and to investigate the mutual temporal patterns of AF and heart failure (HF) in patients indicated to cardiac resynchronization therapy. Four hundred ten consecutive patients (70% male, age 69 +/- 11) with advanced HF (NYHA = 3.0 +/- 0.6), low ejection fraction (EF = 27 +/- 9%), and ventricular conduction delay (QRS = 165 +/- 29 ms) received a biventricular pacemaker. Enrolled patients were divided into two groups: G1 = 249 patients with no AF history, G2 = 161 patients with history of paroxysmal/persistent AF. In a median follow-up of 13 months, AF episodes longer than 5 minutes occurred in 105 of 249 (42.2%) G1 patients and 76 of 161 (47.2%) G2 patients, while AF episodes longer than one day occurred in 14 of 249 (5.6%) G1 patients and in 36 of 161 (22.4%) G2 patients. Device diagnostics monitored daily values of patient activity, night heart rate (NHR), and heart rate variability (HRV). Comparing 30-day periods before AF onset and during persistent AF, significant (P < 0.0001) changes were observed in patient activity, which decreased from 221 +/- 13 to 162 +/- 12 minutes, and in NHR, which increased from 68 +/- 3 to 94 +/- 7 bpm. HRV significantly decreased (from 75 +/- 5 ms before AF onset to 60 +/- 6 ms after AF termination). NHR during AF was significantly (P < 0.01) and inversely correlated (R(2)= 0.73) with activity, with a significant lower activity associated with NHR >or= 88 bpm. AF is frequent in HF patients. Persistent AF is associated with statistically significant decrease in patient activity and HRV and NHR increase.