Moving average and standard deviation thresholding (MAST): a novel algorithm for accurate R-wave detection in the murine electrocardiogram.

Advances in implantable radio-telemetry or diverse biologging devices capable of acquiring high-resolution ambulatory electrocardiogram (ECG) or heart rate recordings facilitate comparative physiological investigations by enabling detailed analysis of cardiopulmonary phenotypes and responses in vivo. Two priorities guiding the meaningful adoption of such technologies are: (1) automation, to streamline and standardize large dataset analysis, and (2) flexibility in quality-control. The latter is especially relevant when considering the tendency of some fully automated software solutions to significantly underestimate heart rate when raw signals contain high-amplitude noise. We present herein moving average and standard deviation thresholding (MAST), a novel, open-access algorithm developed to perform automated, accurate, and noise-robust single-channel R-wave detection from ECG obtained in chronically instrumented mice. MAST additionally and automatically excludes and annotates segments where R-wave detection is not possible due to artefact levels exceeding signal levels. Customizable settings (e.g. window width of moving average) allow for MAST to be scaled for use in non-murine species. Two expert reviewers compared MAST's performance (true/false positive and false negative detections) with that of a commercial ECG analysis program. Both approaches were applied blindly to the same random selection of 270 3-min ECG recordings from a dataset containing varying amounts of signal artefact. MAST exhibited roughly one quarter the error rate of the commercial software and accurately detected R-waves with greater consistency and virtually no false positives (sensitivity, Se: 98.48% ± 4.32% vs. 94.59% ± 17.52%, positive predictivity, +P: 99.99% ± 0.06% vs. 99.57% ± 3.91%, P < 0.001 and P = 0.0274 respectively, Wilcoxon signed rank; values are mean ± SD). Our novel, open-access approach for automated single-channel R-wave detection enables investigators to study murine heart rate indices with greater accuracy and less effort. It also provides a foundational code for translation to other mammals, ectothermic vertebrates, and birds.

Reduced Heart Rate Variability and Altered Cardiac Conduction after Pre-Eclampsia.

Pre-eclampsia is a hypertensive disorder of pregnancy that is associated with elevated maternal risk for cardiovascular disease. The aims of this study were to determine the effect of normal pregnancy on postpartum parameters of the electrocardiogram, and furthermore to determine how a history of pre-eclampsia may affect these parameters. Ten-minute high-resolution (1000 Hz) orthogonal Holter electrocardiogram (ECG) recordings were used to measure heart rate variability (HRV). Signal-averaged P-wave and QRS complex durations were determined. Participants included non-pregnant controls, normotensive parous controls and women with a recent history of PE. While reductions in HRV induced by uncomplicated pregnancy returned to non-pregnant levels by 6-8 months postpartum HRV remained reduced in women with a history of PE compared to control groups. In addition, P-Wave and QRS complex durations were prolonged in PE subjects at 6-8 months postpartum compared to control groups. Only QRS duration was independent of differences in blood pressure. These results suggest increased sympathetic cardiac activity, and delayed myocardial conduction in women after PE; alterations consistent with cardiac remodeling and increased risk for arrhythmia. In examining the association between PE and cardiovascular disease, identification of ECG abnormalities soon after pregnancy in women with a history of PE highlights a unique opportunity for early identification and screening in this population before other risk factors become apparent.

Heart rate variability and procedural outcome in catheter ablation for atrial fibrillation.

INTRODUCTION: In patients with normal hearts, increased vagal tone is associated with onset of paroxysmal atrial fibrillation (AF). Vagal denervation of the atria renders AF less inducible. Circumferential pulmonary vein isolation (CPVI) is effective for treating paroxysmal and persistent AF, and has been shown to impact heart rate variability (HRV) indices, in turn, reflecting vagal denervation. We examined the impact of CPVI on HRV indices, and evaluated the relationship between vagal modification and AF recurrence. METHODS: Electrocardiogram recordings were collected from 83 consecutive patients (63 male, 20 female, age 56.9 ± 9.3 years) undergoing CPVI for paroxysmal (n = 56) or persistent (n = 27) AF. Recordings were obtained over 10 minutes preprocedure, and at intervals up to 12 months. Antiarrhythmic medications were suspended prior to CPVI, and were resumed for 3 months following. Success was defined as no recurrence of atrial arrhythmia lasting longer than 30 seconds. RESULTS: In patients with successful procedures (n = 56, 42 paroxysmal, 14 persistent), HRV indices were significantly altered, with respect to preprocedure levels, over a sustained period. However, patients with recurrence (n = 27, 14 paroxysmal, 13 persistent) demonstrated similar HRV to their preprocedure levels over the follow-up period. CONCLUSION: Our results suggest that patients experiencing recurrence after a single CPVI have HRV attenuated by the procedure only intermittently, whereas patients with one successful CPVI experience a sustained change. A short-term HRV recording is a convenient and potentially important marker for recurrence of atrial arrhythmia in a population undergoing CPVI.

Reverse atrial electrical remodelling induced by continuous positive airway pressure in patients with severe obstructive sleep apnoea.

BACKGROUND: Obstructive sleep apnoea (OSA) is associated with cardiovascular morbidity and mortality, including atrial arrhythmias. Continuous positive airway pressure (CPAP) is the gold standard treatment for OSA; its impact on atrial electrical remodelling has not been fully investigated. Signal-averaged p-wave (SAPW) duration is an accepted marker for atrial electrical remodelling. OBJECTIVE: The objective of this study is to determine whether CPAP induces reverse atrial electrical remodelling in patients with severe OSA. METHODS: Consecutive patients attending the Sleep Disorder Clinic at Kingston General Hospital underwent full polysomnography. OSA-negative controls and severe OSA were defined as apnoea-hypopnea index (AHI) < 5 events/hour and AHI ≥ 30 events/hour, respectively. SAPW duration was determined at baseline and after 4-6 weeks of CPAP in severe OSA patients or without intervention controls. RESULTS: Nineteen severe OSA patients and 10 controls were included in the analysis. Mean AHI and minimum oxygen saturation were 41.4 ± 10.1 events/hour and 80.5 ± 6.5 % in severe OSA patients and 2.8 ± 1.2 events/hour and 91.4 ± 2.1 % in controls. At baseline, severe OSA patients had a greater SAPW duration than controls (131.9 ± 10.4 vs 122.8 ± 10.5 ms; p = 0.02). After CPAP, there was a significant reduction of SAPW duration in severe OSA patients (131.9 ± 10.4 to 126.2 ± 8.8 ms; p < 0.001), while SAPW duration did not change after 4-6 weeks in controls. CONCLUSION: CPAP induced reverse atrial electrical remodelling in patients with severe OSA as represented by a significant reduction in SAPW duration.