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Frontiers in Physiology 2018The heart rhythm of a person following heart transplantation (HTX) is assumed to display an intrinsic cardiac rhythm because it is significantly less influenced by the...
The heart rhythm of a person following heart transplantation (HTX) is assumed to display an intrinsic cardiac rhythm because it is significantly less influenced by the autonomic nervous system-the main source of heart rate variability in healthy people. Therefore, such a rhythm provides evidence for arrhythmogenic processes developing, usually silently, in the cardiac tissue. A model is proposed to simulate alterations in the cardiac tissue and to observe the effects of these changes on the resulting heart rhythm. The hybrid automata framework used makes it possible to represent reliably and simulate efficiently both the electrophysiology of a cardiac cell and the tissue organization. The curve fitting method used in the design of the hybrid automaton cycle follows the well-recognized physiological phases of the atrial myocyte membrane excitation. Moreover, knowledge of the complex architecture of the right atrium, the ability of the almost free design of intercellular connections makes the automata approach the only one possible. Two particular aspects are investigated: impairment of the impulse transmission between cells and structural changes in intercellular connections. The first aspect models the observed fatigue of cells due to specific cardiac tissue diseases. The second aspect simulates the increase in collagen deposition with aging. Finally, heart rhythms arising from the model are validated with the sinus heart rhythms recorded in HTX patients. The modulation in the impairment of the impulse transmission between cells reveals qualitatively the abnormally high heart rate variability observed in patients living long after HTX.
PubMed: 30692928
DOI: 10.3389/fphys.2018.01859 -
Revista Espanola de Cardiologia... Jul 2023Little is known about the usefulness of heart rate (HR) response to exercise for risk stratification in heart failure with preserved ejection fraction (HFpEF)....
INTRODUCTION AND OBJECTIVES
Little is known about the usefulness of heart rate (HR) response to exercise for risk stratification in heart failure with preserved ejection fraction (HFpEF). Therefore, this study aimed to assess the association between HR response to exercise and the risk of total episodes of worsening heart failure (WHF) in symptomatic stable patients with HFpEF.
METHODS
This single-center study included 133 patients with HFpEF (NYHA II-III) who performed maximal cardiopulmonary exercise testing. HR response to exercise was evaluated using the chronotropic index (CI) formula. A negative binomial regression method was used.
RESULTS
The mean age of the sample was 73.2± 10.5 years; 56.4% were female, and 51.1% were in atrial fibrillation. The median for CI was 0.4 [0.3-0.55]. At a median follow-up of 2.4 [1.6-5.3] years, a total of 146 WHF events in 58 patients and 41 (30.8%) deaths were registered. In the whole sample, CI was not associated with adverse outcomes (death, P=.319, and WHF events, P=.573). However, we found a differential effect across electrocardiographic rhythms for WHF events (P for interaction=.002). CI was inversely and linearly associated with the risk of WHF events in patients with sinus rhythm and was positively and linearly associated with those with atrial fibrillation.
CONCLUSIONS
In patients with HFpEF, CI was differentially associated with the risk of total WHF events across rhythm status. Lower CI emerged as a risk factor for predicting higher risk in patients with sinus rhythm. In contrast, higher CI identified a higher risk in those with atrial fibrillation.
Topics: Humans; Female; Middle Aged; Aged; Aged, 80 and over; Male; Atrial Fibrillation; Stroke Volume; Heart Failure; Electrocardiography; Exercise Test; Prognosis
PubMed: 36038124
DOI: 10.1016/j.rec.2022.08.003 -
Nephron 1996Three hypertensive patients with chronic renal failure treated with slow-release verapamil at the recommended doses for high blood pressure experienced acute deleterious... (Review)
Review
Three hypertensive patients with chronic renal failure treated with slow-release verapamil at the recommended doses for high blood pressure experienced acute deleterious effects shortly after treatment (6 h to 3 days). Patients developed slow cardiac rhythms (junctional bradycardia or atrial fibrillation), hypotension and hyperkalemia. Consequently they also had oliguria and worsening of the renal function. Inotropic support, fluid therapy and potassium-lowering measures were able to restore the renal function and sinus rhythm after 10-12 h. Only 7 similar cases have been described so far. It is suggested that slow-release formulations of verapamil must be used with caution in hypertensive patients with impaired renal function.
Topics: Aged; Bradycardia; Delayed-Action Preparations; Electrocardiography; Female; Heart Rate; Humans; Kidney Failure, Chronic; Male; Middle Aged; Vasodilator Agents; Verapamil
PubMed: 8852497
DOI: 10.1159/000188913 -
Heliyon Jan 2023The functioning of the heart rhythm can exhibit a wide variety of dynamic behaviours under certain conditions. In the case of rhythm disorders or cardiac arrhythmias,...
The functioning of the heart rhythm can exhibit a wide variety of dynamic behaviours under certain conditions. In the case of rhythm disorders or cardiac arrhythmias, the natural rhythm of the heart is usually involved in the sinoatrial node, the atrioventricular node, the atria of the carotid sinus, etc. The study of heart related disorders requires an important analysis of its rhythm because the regularity of cardiac activity is conditioned by a large number of factors. The cardiac system is made up of a combination of nodes ranging from the sinus node, the atrioventricular node to its Purkinje bundles, which interact with each other via communicative aspects. Due to the nature of their respective dynamics, the above are treated as self-oscillating elements and modelled by nonlinear oscillators. By modelling the cardiac conduction system as a model of three nonlinear oscillators coupled by delayed connections and subjected to external stimuli depicting the behavior of a pacemaker, its dynamic behavior is studied in this paper by nonlinear analysis tools. From an electrocardiogram (ECG) assessment, the heart rhythm reveals normal and pathological rhythms. Three forms of ventricular fibrillation, ventricular flutter, ventricular tachycardia and atrial fibrillation are observed. The results are confirmed by the respective maximum Lyapunov exponents. Considering the cardiac nodes as microchips, using microcontroller simulation technology, the cardiac conduction system was modelled as a network of four ATmega 328P microcontrollers. A similarity with the results obtained numerically can be observed.
PubMed: 36820178
DOI: 10.1016/j.heliyon.2023.e12887 -
Pacing and Clinical Electrophysiology :... Jul 1995The relative significance of the direct and indirect effects of autonomic tone on diurnal fluctuations in human ventricular and atrial refractoriness are not well known....
The relative significance of the direct and indirect effects of autonomic tone on diurnal fluctuations in human ventricular and atrial refractoriness are not well known. In this study, the circadian rhythms of ventricular and atrial effective refractory periods (ERPs) were measured by noninvasive programmed stimulation in ten patients (mean age 62 +/- 10 years) who had a permanent dual chamber pacemaker for complete atrioventricular (AV) block. The ERP was measured at 4-hour intervals during spontaneous sinus rhythm with ventricular pacing (day 1) and during constant-rate dual chamber pacing (day 2). Cosinor analysis showed the ventricular ERP to have a significant diurnal rhythm in sinus rhythm (amplitude, 12 msec; 95% confidence intervals 1-24 msec) but not during constant-rate pacing (amplitude, 4 msec; 95% confidence intervals -3-12 msec). The atrial ERP had a significant rhythm at times of both spontaneous sinus rate (amplitude, 19 msec; confidence intervals 13-24 msec) and constant heart rate (amplitude, 11 msec; confidence intervals 1-21 msec) with acrophase during the sleeping hours. The increase in heart rate during dual chamber pacing resulted in a more marked decrease in the average 24-hour ERP in the ventricle than in the atrium (46 +/- 9 msec vs 12 +/- 6 msec, P < 0.01). Thus, refractoriness is more rate dependent in the ventricle than in the atrium, and autonomic influences on ventricular refractoriness are mainly indirect, via fluctuations in the sinus rate, but atrial refractoriness is also affected by direct neural influences and/or other rate independent factors.
Topics: Adult; Aged; Atrial Function; Circadian Rhythm; Electrocardiography; Female; Heart Rate; Humans; Male; Middle Aged; Refractory Period, Electrophysiological; Ventricular Function
PubMed: 7567588
DOI: 10.1111/j.1540-8159.1995.tb02597.x -
Physiological Measurement Jan 2008Automatic detection of atrial activity (P waves) in an electrocardiogram (ECG) is a crucial task to diagnose the presence of arrhythmias. The P wave is difficult to...
Automatic detection of atrial activity (P waves) in an electrocardiogram (ECG) is a crucial task to diagnose the presence of arrhythmias. The P wave is difficult to detect and most of the approaches in the literature have been evaluated on normal sinus rhythms and rarely considered arrhythmia contexts other than atrial flutter and fibrillation. A novel knowledge-based P wave detector algorithm is presented. It is self-adaptive to the patient and able to deal with certain arrhythmias by tracking the PP rhythm. The detector has been tested on 12 records of the MIT-BIH arrhythmia database containing several ventricular and supra-ventricular arrhythmias. On the overall records, the detector demonstrates Se = 96.60% and Pr = 95.46%; for the normal sinus rhythm, it reaches Se = 97.76% and Pr = 96.80% and, in the case of Mobitz type II, it demonstrates Se = 72.79% and Pr = 99.51%. It also shows good performance for trigeminy and bigeminy, and outperforms some more sophisticated techniques. Although the results emphasize the difficulty of P wave detection in difficult arrhythmias (supra and ventricular tachycardias), it shows that domain knowledge can efficiently support signal processing techniques.
Topics: Accelerated Idioventricular Rhythm; Algorithms; Arrhythmias, Cardiac; Atrial Fibrillation; Atrial Flutter; Electrocardiography; Heart; Heart Rate; Humans; Reproducibility of Results; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Tachycardia, Supraventricular; Tachycardia, Ventricular; Ventricular Flutter
PubMed: 18175865
DOI: 10.1088/0967-3334/29/1/010 -
Prediction of atrial fibrillation using a home blood pressure monitor with a high-resolution system.Open Heart Sep 2022The usefulness of screening for atrial fibrillation (AF) using several home blood pressure (BP) monitors has been reported. We evaluated the accuracy of a...
OBJECTIVE
The usefulness of screening for atrial fibrillation (AF) using several home blood pressure (BP) monitors has been reported. We evaluated the accuracy of a high-resolution system (HiRS) for AF prediction and its usefulness when installed in home BP monitors.
METHODS
In patients with paroxysmal, persistent or permanent AF, ECG recording and BP measurements were performed simultaneously. The relationship between ECG rhythm diagnosis and pulse irregularity recognition, using a home BP monitor with HiRS, was investigated. The severity of a pulse disturbance during BP measurement was displayed as an irregular pulse rhythm symbol (IPRS) in three instances. The IPRS was not displayed if the pulse was regular, turned on if there was a weak variation in the pulse, and blinked if there was a strong variation in the pulse.
RESULTS
One hundred and seven patients (44 paroxysmal AF, 63 persistent or permanent AF) were enrolled, and a total of 333 recordings were analysed. The rhythms recorded by each ECG were 73 sinus regular rhythms, 35 extrasystoles, 222 AFs and 3 atrial flutters. Sensitivity and specificity for the prediction of any arrhythmia by the IPRS display of the BP monitor were 95.8% (95% CI 92.6% to 97.6%) and 96.8% (95% CI 92.6% to 100%), respectively. In addition, sensitivity and specificity for the prediction of AF were 100% (95% CI 97.5% to 100%) and 74.8% (95% CI 65.6% to 82.5%), respectively. Sensitivity and specificity for the prediction of AF by the IPRS blinking display were 88.3% (95% CI 83.3% to 92.2%) and 94.6% (95% CI 88.6% to 98.0%%), respectively. IPRS exhibited lighting or blinking during AF occurrence; however, during sinus rhythm, IPRS was not displayed in 72 out of 73 recordings.
CONCLUSION
The IPRS device predicted AF with precision and may be particularly useful for predicting an arrhythmia attack in patients with paroxysmal AF.
Topics: Atrial Fibrillation; Blood Pressure Monitors; Electrocardiography; Heart Rate; Humans; Sensitivity and Specificity
PubMed: 36170999
DOI: 10.1136/openhrt-2022-002006 -
The Journal of Thoracic and... Apr 2008We sought to assess the clinical and survival benefit of atrial fibrillation surgery in patients submitted to mitral valve surgery after stabilization of postoperative...
OBJECTIVES
We sought to assess the clinical and survival benefit of atrial fibrillation surgery in patients submitted to mitral valve surgery after stabilization of postoperative rhythm at 1 year.
METHODS
One thousand seven hundred twenty-three patients were enrolled. Patients with follow-up of longer than 1 year (n = 972) were divided into 3 groups according to surface electrocardiographic rhythm during follow-up visits: stable sinus rhythm, stable atrial fibrillation, and intermittent rhythms. Adverse cardiac event incidence and predictors of long-term outcome were compared among the 3 groups.
RESULTS
In-hospital mortality was 2.6%. Risk factors for mortality were the cut-and-sew technique (odds ratio, 8.92; 95% confidence interval, 1.71-46.50; P = .009) and isolated left atrial procedure (odds ratio, 0.16; 95% confidence interval, 0.04-0.56; P = .004). At 1 year, 63.4% patients were in stable sinus rhythm. Stable sinus rhythm was found to be associated with early and late survival (P = .01, log-rank analysis). Multivariate binary logistic regression analysis found that left atrial dimension (odds ratio, 0.97; 95% confidence interval, 0.96-0.99; P = .005) and concomitant coronary revascularization (odds ratio, 0.48; 95% confidence interval, 0.25-0.92; P = .027) were independent predictors of stable sinus rhythm at 1 year after surgical intervention. At 48 months' follow-up, predictors for stable sinus rhythm were biatrial surgical approach and absence of preoperative permanent atrial fibrillation (odds ratio, 3.56; 95% confidence interval, 1.62-7.83; P < .002). Left atrial size (each millimeter) has a borderline statistical significance (odds ratio, 0.97; 95% confidence interval, 0.93-1.00; P = .065). Thromboembolic events were found to be associated with absence of stable sinus rhythm (P = .010, log-rank analysis).
CONCLUSIONS
The achievement of stable sinus rhythm is a predictor of better survival and lower incidence of thromboembolic events. Predictors of stable sinus rhythm were smaller dimensions of the left atrium, biatrial approach, absence of preoperative permanent atrial fibrillation, and absence of concomitant coronary artery bypass grafting.
Topics: Aged; Atrial Fibrillation; Female; Follow-Up Studies; Heart Valve Diseases; Humans; Male; Middle Aged; Mitral Valve; Registries; Survival Analysis; Treatment Outcome
PubMed: 18374769
DOI: 10.1016/j.jtcvs.2007.08.069 -
Pacing and Clinical Electrophysiology :... Apr 1994Despite advances in the computerized detection of arrhythmias, arrhythmia recognition by morphological waveform analysis still poses a difficult problem. Artificial...
Despite advances in the computerized detection of arrhythmias, arrhythmia recognition by morphological waveform analysis still poses a difficult problem. Artificial neural networks, computer algorithms that are self-trained by an analog of biological synaptic modification to perform pattern recognition, hold great promise for the differentiation of various cardiac rhythms. The goal of this study was to differentiate beats of sinus and ventricular origin on a global basis and on a patient-specific basis by the use of artificial neural network analysis. Neural networks were trained to recognize digitized intracardiac electrograms (9 patients) and surface electrocardiograms (11 patients) obtained during sinus rhythm and ventricular tachycardia. After training, sinus rhythm or ventricular tachycardia beats were input into the neural network, and classified as to their origin. By the use of modified receiver operating characteristic curve plots, it was possible to differentiate with high sensitivity and specificity between beats of sinus origin and ventricular origin in all patients. The addition of high amounts of noise to the beats did not markedly degrade the performance of the surface ECG neural networks, and still allowed high sensitivity in differentiating beats of sinus origin from beats of ventricular origin, especially when noise was added to the training set. Neural networks provided sensitive and specific detection of cardiac electrical activity during sinus rhythm and ventricular tachycardia, and may play an important role in allowing development of improved arrhythmia recognition and management systems.
Topics: Aged; Aged, 80 and over; Algorithms; Artifacts; Diagnosis, Differential; Electrocardiography; Electrophysiology; Feedback; Heart Rate; Humans; Male; Middle Aged; Neural Networks, Computer; Pattern Recognition, Automated; ROC Curve; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Sinoatrial Node; Software; Tachycardia, Ventricular
PubMed: 7516545
DOI: 10.1111/j.1540-8159.1994.tb02398.x -
Pediatric Critical Care Medicine : a... Aug 2023To characterize inappropriate shock delivery during pediatric in-hospital cardiac arrest (IHCA).
OBJECTIVES
To characterize inappropriate shock delivery during pediatric in-hospital cardiac arrest (IHCA).
DESIGN
Retrospective cohort study.
SETTING
An international pediatric cardiac arrest quality improvement collaborative Pediatric Resuscitation Quality [pediRES-Q].
PATIENTS
All IHCA events from 2015 to 2020 from the pediRES-Q Collaborative for which shock and electrocardiogram waveform data were available.
INTERVENTIONS
None.
MEASUREMENTS AND MAIN RESULTS
We analyzed 418 shocks delivered during 159 cardiac arrest events, with 381 shocks during 158 events at 28 sites remaining after excluding undecipherable rhythms. We classified shocks as: 1) appropriate (ventricular fibrillation [VF] or wide complex ≥ 150/min); 2) indeterminate (narrow complex ≥ 150/min or wide complex 100-149/min); or 3) inappropriate (asystole, sinus, narrow complex < 150/min, or wide complex < 100/min) based on the rhythm immediately preceding shock delivery. Of delivered shocks, 57% were delivered appropriately for VF or wide complex rhythms with a rate greater than or equal to 150/min. Thirteen percent were classified as indeterminate. Thirty percent were delivered inappropriately for asystole (6.8%), sinus (3.1%), narrow complex less than 150/min (11%), or wide complex less than 100/min (8.9%) rhythms. Eighty-eight percent of all shocks were delivered in ICUs or emergency departments, and 30% of those were delivered inappropriately.
CONCLUSIONS
The rate of inappropriate shock delivery for pediatric IHCA in this international cohort is at least 30%, with 23% delivered to an organized electrical rhythm, identifying opportunity for improvement in rhythm identification training.
Topics: Humans; Child; Electric Countershock; Retrospective Studies; Heart Arrest; Cardiopulmonary Resuscitation; Ventricular Fibrillation; Hospitals
PubMed: 37115167
DOI: 10.1097/PCC.0000000000003241