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Ventricular Rate (ventricular + rate)
Selected AbstractsElectrical Remodeling and Atrial Dilation During Atrial Tachycardia are Influenced by Ventricular Rate: Role of Developing TachycardiomyopathyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2001BAS A. SCHOONDERWOERD M.D. Atrial Remodeling in Tachycardiomyopathy. Introduction: Atrial fibrillation (AF) and congestive heart failure (CHF) are two clinical entities that often coincide. Our aim was to establish the influence of concomitant high ventricular rate and consequent development of CHF on electrical remodeling and dilation during atrial tachycardia. Methods and Results: A total of 14 goats was studied. Five goats were subjected to 3:1 AV pacing (A-paced group, atrial rate 240 beats/min, ventricular rate 80 beats/min). Nine goats were subjected to rapid 1:1 AV pacing (AV-paced group, atrial and ventricular rates 240 beats/min). During 4 weeks, right atrial (RA) and left ventricular (LV) diameters were measured during sinus rhythm. Atrial effective refractory periods (AERP) and inducibility of AF were assessed at three basic cycle lengths (BCL). After 4 weeks of rapid AV pacing, RA and LV diameters had increased to 151% and 113% of baseline, whereas after rapid atrial pacing alone, these parameters were unchanged. Right AERP (157 ± 10 msec vs 144 ± 16 msec at baseline with BCL of 400 msec in the A-paced and AV-paced group, respectively) initially decreased in both groups, reaching minimum values within 1 week. Subsequently, AERP partially recovered in AV-paced goats, whereas AERP remained short in A-paced goats (79 ± 7 msec vs 102 ± 12 msec after 4 weeks; P < 0.05). Left AERP demonstrated a similar time course. Inducibility of AF increased in both groups and reached a maximum during the first week in both groups, being 20% and 48% in the A-paced and AV-paced group, respectively. Conclusion: Nature and time course of atrial electrical remodeling and dilation during atrial tachycardia are influenced by concurrent high ventricular rate and consequent development of CHF. [source] Combination Therapy with Digoxin and Diltiazem Controls Ventricular Rate in Chronic Atrial Fibrillation in Dogs Better than Digoxin or Diltiazem Monotherapy: A Randomized Crossover Study in 18 DogsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 3 2009A.R.M. Gelzer Background: Atrial fibrillation (AF) with excessively high ventricular rates (VR) occurs in dogs with advanced heart disease. Rate control improves clinical signs in these patients. Optimal drug therapy and target VR remain poorly defined. Hypothesis: Digoxin-diltiazem combination therapy reduces VR more than either drug alone in dogs with high VR AF. Animals: Eighteen client-owned dogs (>15 kg) with advanced heart disease, AF, and average VR on 24-hour Holter > 140 beats per minute (bpm). Methods: After baseline Holter recording, dogs were randomized to digoxin or diltiazem monotherapy, or combination therapy. Repeat Holter evaluation was obtained after 2 weeks; dogs were then crossed over to the other arm (monotherapy or combination therapy) for 2 weeks and a third Holter was acquired. Twenty-four hour average VR, absolute and relative VR changes from baseline, and percent time spent within prespecified VR ranges (>140, 100,140, and <100 bpm) were compared. Correlations between serum drug concentrations and VR were examined. Results: Digoxin (median, 164 bpm) and diltiazem (median, 158 bpm) decreased VR from baseline (median, 194 bpm) less than the digoxin-diltiazem combination (median, 126 bpm) (P < .008 for each comparison). With digoxin-diltiazem, VR remained <140 bpm for 85% of the recording period, but remained >140 bpm for 88% of the recording period with either monotherapy. Serum drug concentrations did not correlate with VR. Conclusions and Clinical Importance: At the dosages used in this study, digoxin-diltiazem combination therapy provided a greater rate control than either drug alone in dogs with AF. [source] Role of Transthoracic Echocardiography in Atrial FibrillationECHOCARDIOGRAPHY, Issue 4 2000RICHARD W. ASINGER M.D. Atrial fibrillation is a major clinical problem that is predicted to be encountered more frequently as the population ages. The clinical management of atrial fibrillation has become increasingly complex as new therapies and strategies have become available for ventricular rate control, conversion to sinus rhythm, maintenance of sinus rhythm, and prevention of thromboembolism. Clinical and transthoracic echocardiographic features are important in determining etiology and directing therapy for atrial fibrillation. Left atrial size, left ventricular wall thickness, and left ventricular function have independent predictive value for determining the risk of developing atrial fibrillation. Left atrial size may have predictive value in determining the success of cardioversion and maintaining sinus rhythm in selected clinical settings but has less value in the most frequently encountered group, patients with nonvalvular atrial fibrillation, in whom the duration of atrial fibrillation is the most important feature. When selecting pharmacological agents to control ventricular rate, convert to sinus rhythm, and maintain normal sinus rhythm, transthoracic echocardiography (TTE) allows noninvasive evaluation of left ventricular function and hence guides management. The combination of clinical and transthoracic echocardiographic features also allows risk stratification for thromboembolism and hemorrhagic complications in atrial fibrillation. High-risk clinical features for thromboembolism supported by epidemiological observations, results of randomized clinical trials, and meta-analyses include rheumatic valvular heart disease, prior thromboembolism, congestive heart failure, hypertension, older (> 75 years old) women, and diabetes. Small series of cases also suggest those with hyperthyroidism and hypertrophic cardiomyopathy are at high risk. TTE plays a unique role in confirming or discovering high-risk features such as rheumatic valvular disease, hypertrophic cardiomyopathy, and decreased left ventricular function. Validation of the risk stratification scheme used in the Stroke Prevention in Atrial Fibrillation-III trial is welcomed by clinicians who are faced daily with balancing the benefit and risks of anticoagulation to prevent thromboembolism inpatients with atrial fibrillation. [source] Hypertonic Saline Treatment of Severe Hyperkalemia in Nonnephrectomized DogsACADEMIC EMERGENCY MEDICINE, Issue 9 2000Justin L. Kaplan MD Abstract. Objectives: To determine whether a hypertonic saline bolus improves cardiac conduction or plasma potassium levels more than normal saline infusion within 15 minutes of treatment for severe hyperkalemia. Previously with this model, 8.4% sodium chloride (NaCl) and 8.4% sodium bicarbonate (NaHCO3) lowered plasma potassium equally effectively. Methods: This was a crossover study using ten conditioned dogs (14-20 kg) that received, in random order, each of three intravenous (IV) treatments in separate experiments at least one week apart: 1) 2 mmol/kg of 8.4% NaCl over 5 minutes (bolus); 2) 2 mmol/kg of 0.9% NaCl over one hour (infusion); or 3) no treatment (control). Using isoflurane anesthesia and ventilation (pCO2= 35-40 torr), 2 mmol/kg/hr of IV potassium chloride (KCl) was infused until conduction delays (both absent p-waves and ,20% decrease in ventricular rate in ,5 minutes) were sustained for 15 minutes. The KCl was then decreased to 1 mmol/kg/hr (maintenance) for 2 hours and 45 minutes. Treatment (0 minutes) began after 45 minutes of maintenance KCl. Results: From 0 to 15 minutes, mean heart rate increased 29.6 (95% CI = 12.2 to 46; p < 0.005) beats/min more with bolus than infusion and 23.4 (95% CI = 2.6 to 43.5; p < 0.03) beats/min more with bolus than control. No clinically or statistically significant difference was seen in heart rate changes from 0 to 30 minutes. Decreases in potassium from 0 to 15 minutes were similar with bolus, infusion, and control. Conclusions: In this model, 8.4% NaCl bolus reversed cardiac conduction abnormalities within the first 15 minutes after treatment, more rapidly than did the 0.9% NaCl infusion or control. This reversal occurred despite similar reductions in potassium levels. [source] Bepridil Reverses Atrial Electrical Remodeling and L-Type Calcium Channel Downregulation in a Canine Model of Persistent Atrial TachycardiaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2007KUNIHIRO NISHIDA M.D. Introduction: This study tested whether bepridil, a multichannel blocker, would reverse electrical remodeling induced by persistent atrial tachycardia. Methods and Results: Fourteen dogs were subjected to rapid atrial pacing at 400 bpm for 6 weeks after atrioventricular block was created to control the ventricular rate. During the study period, seven dogs were given placebo for 6 weeks (Control group), and seven were given placebo for 3 weeks, followed by 3 weeks of bepridil (10 mg/kg/day, Bepridil group). The atrial effective refractory period (ERP) and the inducibility and duration of atrial fibrillation (AF) were determined on a weekly basis. After 6 weeks, expression of L-type calcium channel ,1C messenger ribonucleic acid (mRNA) was quantified by real-time reverse transcription-polymerase chain reaction. In the Control group, ERP was shortened and the inducibility and duration of AF increased through the 6-week period. In the Bepridil group, the same changes occurred during the first 3 weeks, but were gradually reversed with bepridil. After 6 weeks, ERP was longer, AF inducibility was lower, and AF duration was shorter in Bepridil group than in the Control group. Expression of ,1C mRNA was decreased by 64% in the Control group (P < 0.05 vs sham), but in the Bepridil group, it was not different compared with the sham dogs. As a whole group of dogs, ERP was positively correlated with ,1C mRNA expression. Conclusion: Bepridil reverses the electrophysiological consequences of atrial remodeling to some extent and L-type calcium channel downregulation in a canine model of atrial tachycardia. [source] Proarrhythmia of Circumferential Left Atrial Lesions for Management of Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2006EMILE G. DAOUD M.D. Background: After circumferential ablation for atrial fibrillation, new onset left atrial flutter (LA Flr) may occur. This study assessed the relationship between induced and clinical episodes of LA Flr, the rate of spontaneous resolution of LA Flr, and the proarrhythmic effect of circumferential ablation. Methods and Results: A total 112 patients underwent circumferential LA ablation for atrial fibrillation. Immediately after completion of the ablation, LA Flr was induced in 43 of 112 (38%) patients, but was not targeted for ablation. During follow-up (14 ± 4 months), new onset LA Flr occurred in 28 of 112 (25%) patients; however, the presence of inducible LA Flr did not identify those patients with clinical LA Flr (P = 0.6). In comparison to episodes of atrial fibrillation occurring before circumferential ablation, LA Flr was associated with a faster ventricular rate (124 ± 19 beats/min vs 91 ± 16 beats/min, P < 0.001), and was more likely to be persistent requiring cardioversion (86% vs 32%, P = 0.01). By ,4 months postcircumferential ablation, clinical LA Flr resolved in 18 of 28 patients (64%). A second ablation procedure for LA Flr was performed in 9 of 10 patients. Of the 17 morphologies, 16 (94%) LA Flr circuits were successfully ablated. Conclusions: (1) LA Flrs that are induced immediately after circumferential ablation for atrial fibrillation do not identify those patients who require a second ablation procedure for clinical LA Flr; (2) Since the majority of clinical LA Flrs spontaneously resolve, ablation of LA Flr should be postponed several months; and (3) new onset LA Flr after ablation for atrial fibrillation is likely a manifestation of the proarrhythmic effect of ablation lines in the LA. [source] Electrical Remodeling and Atrial Dilation During Atrial Tachycardia are Influenced by Ventricular Rate: Role of Developing TachycardiomyopathyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2001BAS A. SCHOONDERWOERD M.D. Atrial Remodeling in Tachycardiomyopathy. Introduction: Atrial fibrillation (AF) and congestive heart failure (CHF) are two clinical entities that often coincide. Our aim was to establish the influence of concomitant high ventricular rate and consequent development of CHF on electrical remodeling and dilation during atrial tachycardia. Methods and Results: A total of 14 goats was studied. Five goats were subjected to 3:1 AV pacing (A-paced group, atrial rate 240 beats/min, ventricular rate 80 beats/min). Nine goats were subjected to rapid 1:1 AV pacing (AV-paced group, atrial and ventricular rates 240 beats/min). During 4 weeks, right atrial (RA) and left ventricular (LV) diameters were measured during sinus rhythm. Atrial effective refractory periods (AERP) and inducibility of AF were assessed at three basic cycle lengths (BCL). After 4 weeks of rapid AV pacing, RA and LV diameters had increased to 151% and 113% of baseline, whereas after rapid atrial pacing alone, these parameters were unchanged. Right AERP (157 ± 10 msec vs 144 ± 16 msec at baseline with BCL of 400 msec in the A-paced and AV-paced group, respectively) initially decreased in both groups, reaching minimum values within 1 week. Subsequently, AERP partially recovered in AV-paced goats, whereas AERP remained short in A-paced goats (79 ± 7 msec vs 102 ± 12 msec after 4 weeks; P < 0.05). Left AERP demonstrated a similar time course. Inducibility of AF increased in both groups and reached a maximum during the first week in both groups, being 20% and 48% in the A-paced and AV-paced group, respectively. Conclusion: Nature and time course of atrial electrical remodeling and dilation during atrial tachycardia are influenced by concurrent high ventricular rate and consequent development of CHF. [source] Bimodal RR Interval Distribution in Chronic Atrial Fibrillation:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2000Impact of Dual Atrioventricular Nodal Physiology on Long-Term Rate Control after Catheter Ablation of the Posterior Atrionodal Input Bimodal RR Interval Distribution, Introduction: Radiofrequency (RF) catheter modification of the AV node hi patients with atrial fibrillation (AF) is limited by an unpredictable decrease of the ventricular rate and a wish incidence of permanent AV block, A bimodal RR histogram has been suggested to serve as a predictor for successful outcome but the corresponding AV node properties have never been characterized, We hypothesized that a bimodal histogram indicates dual AV nodal physiology and predicts a better outcome after AV node modification in chronic AF. Methods and Results: Thirty-seven patients were prospectively subdivided into two groups according to the RR histogram of 24-hour ECC monitoring, Before to RF ablation, internal cardioversion and programmed stimulation were performed, Among the 22 patients (group I) with a bimodal RR histogram, dual AV nodal physiology was found in 17 (779f) patients, Ablation significantly decreased ventricular rate with loss of the peak of short RR cycles after ablation (mean and maximal ventricular rates: 32% and 35% rate reduction, respectively; P < 0,01), In 15 patients with a unimodal RR histogram (group II), dual AV nodal physiology was found in 2 (13%), and rate reductions were 16% and 17%, respectively, At 6 months, 3 (14%) patients in group 1 and 6 (40%) in group II underwent elective AV nodal ablation with pacemaker implantation due to intolerable rapid ventricular response to AF. Conclusion: Bimodal RR interval distribution during chronic AF suggests the presence of dual AV nodal physiology and predicts a better outcome of RF ablation of the posterior atrionocdal input. [source] Transvenous Parasympathetic Nerve Stimulation in the Inferior Vena Cava and Atrioventricular ConductionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2000PATRICK SCHAUERTE M.D. Parasympathetic Stimulation in the Inferior Vena Cava. Introduction: In previous reports, we demonstrated a technique for parasympathetic nerve stimulation (PNS) within the superior vena cava, pulmonary artery, and coronary sinus to control rapid ventricular rates during atrial fibrillation (AF). In this report, we describe another vascular site, the inferior vena cava (IVC), at which negative dromotropic effects during AF could consistently he obtained. Moreover, stimulation at this site also induced dual AV nodal electrophysiology. Methods and Results: PNS was performed in ten dogs using rectangular stimuli (0.1 msec/20 Hz) delivered through a catheter with an expandable electrode basket at its tip. Within 3 minutes and without using fluoroscopy, the catheter was positioned at an effective PNS site in the IVC at the junction of the right atrium. AF was induced and maintained by rapid atrial pacing. During stepwise increase of the PNS voltage from 2 to 34 V, a graded response of ventricular rate slowing during AF was observed (266 ± 79 msec without PNS vs 1,539 ± 2,460 msec with PNS at 34 V; P = 0.005 by analysis of variance), which was abolished by atropine and blunted by hexamethonium. In three animals, PNS was performed during sinus rhythm. Dual AV nodal electrophysiology was present in 1 of 3 dogs in control, whereas with PNS, dual AV nodal electrophysiology was observed in all three dogs. PNS did not significantly change sinus rate or arterial blood pressure during ventricular pacing. Conclusion: Stable and consistent transvenous electrical stimulation of parasympathetic nerves innervating the AV node can be achieved in the IVC, a transvenous site that is rapidly and readily accessible. The proposed catheter approach for PNS can be used to control ventricular rate during AF in this animal model. [source] Atrial, SA Nodal, and AV Nodal Electrophysiology in Standing Horses: Normal Findings and Electrophysiologic Effects of Quinidine and DiltiazemJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2007Colin C. Schwarzwald Background: Although atrial arrhythmias are clinically important in horses, atrial electrophysiology has been incompletely studied. Hypotheses: Standard electrophysiologic methods can be used to study drug effects in horses. Specifically, the effects of diltiazem on atrioventricular (AV) nodal conduction are rate-dependent and allow control of ventricular response rate during rapid atrial pacing in horses undergoing quinidine treatment. Animals: Fourteen healthy horses. Methods: Arterial blood pressure, surface electrocardiogram, and right atrial electrogram were recorded during sinus rhythm and during programmed electrical stimulation at baseline, after administration of quinidine gluconate (10 mg/kg IV over 30 minutes, n = 7; and 12 mg/kg IV over 5 minutes followed by 5 mg/kg/h constant rate infusion for the remaining duration of the study, n = 7), and after coadministration of diltiazem (0.125 mg/kg IV over 2 minutes repeated every 12 minutes to effect). Results: Quinidine significantly prolonged the atrial effective refractory period, shortened the functional refractory period (FRP) of the AV node, and increased the ventricular response rate during atrial pacing. Diltiazem increased the FRP, controlled ventricular rate in a rate-dependent manner, caused dose-dependent suppression of the sinoatrial node and produced a significant, but well tolerated decrease in blood pressure. Effective doses of diltiazem ranged from 0.125 to 1.125 mg/kg. Conclusions and Clinical Importance: Standard electrophysiologic techniques allow characterization of drug effects in standing horses. Diltiazem is effective for ventricular rate control in this pacing model of supraventricular tachycardia. The use of diltiazem for rate control in horses with atrial fibrillation merits further investigation. [source] Impact of Right Ventricular Pacing Sites on Exercise Capacity during Ventricular Rate Regularization in Patients with Permanent Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2009HUNG-FAT TSE M.D., Ph.D. Background:The deleterious effects of right ventricular apical (RVA) pacing may offset the potential benefit of ventricular rate (VR) regularization and rate adaptation during an exercise in patient's atrial fibrillation (AF). Methods:We studied 30 patients with permanent AF and symptomatic bradycardia who receive pacemaker implantation with RVA (n = 15) or right ventricular septal (RVS, n = 15) pacing. All the patients underwent an acute cardiopulmonary exercise testing using VVI-mode (VVI-OFF) and VVI-mode with VR regularization (VRR) algorithm on (VVI-ON). Results:There were no significant differences in the baseline characteristics between the two groups, except pacing QRS duration was significantly shorter during RVS pacing than RVA pacing (138.9 ± 5 vs 158.4 ± 6.1 ms, P = 0.035). Overall, VVI-ON mode increased the peak exercise VR, exercise time, metabolic equivalents (METs), and peak oxygen consumption (VO2max), and decreased the VR variability compared with VVI-OFF mode during exercise (P < 0.05), suggesting that VRR pacing improved exercise capacity during exercise. However, further analysis on the impact of VRR pacing with different pacing sites revealed that only patients with RVS pacing but not patients with RVA pacing had significant increased exercise time, METs, and VO2max during VVI-ON compared with VVI-OFF, despite similar changes in peaked exercise VR and VR variability. Conclusion:In patients with permanent AF, VRR pacing at RVS, but not at RVA, improved exercise capacity during exercise. [source] Cardioversion for Atrial Fibrillation: Treatment Options and AdvancesPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2009JAMES A. REIFFEL M.D. Atrial fibrillation (AF) is associated with significant morbidity and mortality. There are two basic approaches to managing AF: slowing the ventricular rate, while allowing the arrhythmia to continue (the rate-control approach), and restoring and maintaining sinus rhythm (the rhythm-control approach) with antiarrhythmic drugs (AADs) and/or ablation, electrical cardioversion (CV), if needed, or both. Strategy trials comparing rate and rhythm control have found no survival advantage of one approach over the other, but other considerations, such as symptom reduction, often necessitate pursuit of rhythm control. Electrical, or direct current, CV is a widely used and effective method for termination of nonparoxysmal AF, although its success can be affected by patient- and technique-related variables. Pharmacological CV options also exist and are preferable in specific circumstances. Both pharmacological and electrical CV are associated with the risk of proarrhythmia. Many AADs are under development for both CV and maintenance of sinus rhythm. Some are atrioselective, such as vernakalant, and target ion channels in the atria, with little or no effects in the ventricle. Vernakalant, currently under Food and Drug Administration review, appears to offer a safer profile than current CV agents and is likely to expand the role of pharmacological CV. Other new AADs that provide increased efficacy or safety while maintaining normal sinus rhythm may also be better than current drugs; if so, rate-rhythm comparisons will differ from those of previous studies. In conclusion, further trials should clarify the long-term safety profiles of new atrioselective agents and other investigational drugs and define their role in the treatment of AF. [source] Radiofrequency Energy Modification of the Atrioventricular Junction in Patients with Atrial Fibrillation: Modes of Ventricular Response Under Autonomic Blockade and Long-Term EffectPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2001HARALAMPOS D. KRIATSELIS KRIATSELIS, H.D., et al.: Radiofrequency Energy Modification of the Atrioventricular Junction in Patients with Atrial Fibrillation: Modes of Ventricular Response Under Autonomic Blockade and Long-Term Effect. The short- and long-term effect of radiofrequency (RF) modification of the AV junction on ventricular rate and left ventricular function and the different types of ventricular response during energy application under autonomic nervous blockade were assessed in 28 patients with medically refractory atrial fibrillation. During the successful RF application, ventricular rate slowed progressively (type I response, ten patients) or accelerated at first and then slowed (type II response, 11 patients). Type II response was associated with a more anterior ablation site compared to Type I response. A primary successful outcome was achieved in 21 patients. Inadvertent complete AV block developed in three patients, while in four patients AV nodal ablation was performed after an unsuccessful modification attempt. During 6-month follow-up, the ventricular rate was adequately controlled in only four patients. Among the 16 patients with a recurrence of uncontrolled AF were all 10 patients with type I response and 6 of 11 patients with type II response. One patient died suddenly 10 weeks after the procedure. [source] Quinidine for Pharmacological Cardioversion of Atrial Fibrillation: A Retrospective Analysis in 501 Consecutive PatientsANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009Bernhard Schwaab M.D. Background: Although quinidine has been used to terminate atrial fibrillation (AFib) for a long time, it has been recently classified to be used as a third-line-drug for cardioversion. However, these recommendations are based on a few small studies, and there are no data available of a larger modern patient population undergoing pharmacological cardioversion of AFib. Therefore, we evaluated the safety of quinidine for cardioversion of paroxysmal AFib in patients after cardiac surgery and coronary intervention. Methods: In 501 consecutive patients (66 ± 9 years, 32% women), 200,400 mg of quinidine were administered every 6 hours until cardioversion or for a maximum of 48 hours. Patients were included with QT interval ,450 ms, ejection fraction (EF) ,35%, and plasma potassium >4.3 mEq/L. Exclusion criteria were: unstable angina, myocardial infarction <3 months, and advanced congestive heart failure. Patients received verapamil, beta-blockers, or digitalis to slow down ventricular rate <100 bpm. Results: Quinidine therapy did not have to be stopped due to adverse drug reactions (ADR), and no significant QTc interval prolongation (Bazett and Fridericia correction) and no life-threatening ventricular arrhythmia occurred. Mean quinidine dose was 617 ± 520 mg and 92% of the patients received verapamil or beta-blocker to decrease ventricular rate. Cardioversion was successful in 84% of patients. All ADRs were minor and transient. Multivariate analysis revealed female gender (OR 2.62, CI 1.61,4.26, P < 0.001) and EF 45,54% (OR 1.97, CI 1.15,3.36, P = 0.013) as independent risk factors for ADRs. Conclusions: Quinidine for pharmacological cardioversion of AFib is safe and well tolerated in this subset of patients. [source] Magnesium Sulfate versus Placebo for Paroxysmal Atrial Fibrillation: A Randomized Clinical TrialACADEMIC EMERGENCY MEDICINE, Issue 4 2009Kevin Chu MBBS Abstract Objectives:, The objective was to investigate the efficacy of magnesium sulfate (MgSO4) in decreasing the ventricular rate in emergency department (ED) patients presenting with new-onset, rapid atrial fibrillation (AF). Methods:, A double-blinded, placebo-controlled randomized clinical trial was conducted in an adult university hospital. Patients aged ,18 years with AF onset of less than 48 hours and a sustained ventricular rate of >100 beats/min were randomized to either intravenous (IV) MgSO4 10 mmol or normal saline (NSal). Rhythm and instantaneous heart rate as measured by the monitor were recorded at baseline and every 15 minutes for 2 hours after starting the trial drug. Heart rate and rhythm were compared at 2 hours. A multilevel modeling analysis was performed to adjust for differences in baseline heart rate and any additional treatment and to examine changes in heart rate over time. Results:, Twenty-four patients were randomized to MgSO4 and 24 to NSal. Baseline heart rate was lower in the MgSO4 group (mean ± standard deviation [±SD] = 125 ± 24 vs. 140 ± 21 beats/min]. One and 3 patients in the MgSO4 and NSal groups, respectively, were given another antiarrhythmic or were electrically cardioverted within 2 hours after starting the trial drug. Heart rate (mean ± SD) at 2 hours in both MgSO4 (116 ± 30 beats/min) and NSal groups (114 ± 31 beats/min) decreased below their respective baseline levels. However, the rate of heart rate decrease across time did not differ between groups (p = 0.124). The proportion of patients who converted to sinus rhythm 2 hours post,trial drug did not differ (MgSO4 8.7% vs. NSal 25.0%, p = 0.25). Conclusions:, This study was unable to demonstrate a difference between IV MgSO4 10 mmol and saline placebo for reducing heart rate or conversion to sinus rhythm at 2 hours posttreatment in ED patients with AF of less than 48 hours duration. [source] Electrical Remodeling and Atrial Dilation During Atrial Tachycardia are Influenced by Ventricular Rate: Role of Developing TachycardiomyopathyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2001BAS A. SCHOONDERWOERD M.D. Atrial Remodeling in Tachycardiomyopathy. Introduction: Atrial fibrillation (AF) and congestive heart failure (CHF) are two clinical entities that often coincide. Our aim was to establish the influence of concomitant high ventricular rate and consequent development of CHF on electrical remodeling and dilation during atrial tachycardia. Methods and Results: A total of 14 goats was studied. Five goats were subjected to 3:1 AV pacing (A-paced group, atrial rate 240 beats/min, ventricular rate 80 beats/min). Nine goats were subjected to rapid 1:1 AV pacing (AV-paced group, atrial and ventricular rates 240 beats/min). During 4 weeks, right atrial (RA) and left ventricular (LV) diameters were measured during sinus rhythm. Atrial effective refractory periods (AERP) and inducibility of AF were assessed at three basic cycle lengths (BCL). After 4 weeks of rapid AV pacing, RA and LV diameters had increased to 151% and 113% of baseline, whereas after rapid atrial pacing alone, these parameters were unchanged. Right AERP (157 ± 10 msec vs 144 ± 16 msec at baseline with BCL of 400 msec in the A-paced and AV-paced group, respectively) initially decreased in both groups, reaching minimum values within 1 week. Subsequently, AERP partially recovered in AV-paced goats, whereas AERP remained short in A-paced goats (79 ± 7 msec vs 102 ± 12 msec after 4 weeks; P < 0.05). Left AERP demonstrated a similar time course. Inducibility of AF increased in both groups and reached a maximum during the first week in both groups, being 20% and 48% in the A-paced and AV-paced group, respectively. Conclusion: Nature and time course of atrial electrical remodeling and dilation during atrial tachycardia are influenced by concurrent high ventricular rate and consequent development of CHF. [source] Bimodal RR Interval Distribution in Chronic Atrial Fibrillation:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2000Impact of Dual Atrioventricular Nodal Physiology on Long-Term Rate Control after Catheter Ablation of the Posterior Atrionodal Input Bimodal RR Interval Distribution, Introduction: Radiofrequency (RF) catheter modification of the AV node hi patients with atrial fibrillation (AF) is limited by an unpredictable decrease of the ventricular rate and a wish incidence of permanent AV block, A bimodal RR histogram has been suggested to serve as a predictor for successful outcome but the corresponding AV node properties have never been characterized, We hypothesized that a bimodal histogram indicates dual AV nodal physiology and predicts a better outcome after AV node modification in chronic AF. Methods and Results: Thirty-seven patients were prospectively subdivided into two groups according to the RR histogram of 24-hour ECC monitoring, Before to RF ablation, internal cardioversion and programmed stimulation were performed, Among the 22 patients (group I) with a bimodal RR histogram, dual AV nodal physiology was found in 17 (779f) patients, Ablation significantly decreased ventricular rate with loss of the peak of short RR cycles after ablation (mean and maximal ventricular rates: 32% and 35% rate reduction, respectively; P < 0,01), In 15 patients with a unimodal RR histogram (group II), dual AV nodal physiology was found in 2 (13%), and rate reductions were 16% and 17%, respectively, At 6 months, 3 (14%) patients in group 1 and 6 (40%) in group II underwent elective AV nodal ablation with pacemaker implantation due to intolerable rapid ventricular response to AF. Conclusion: Bimodal RR interval distribution during chronic AF suggests the presence of dual AV nodal physiology and predicts a better outcome of RF ablation of the posterior atrionocdal input. [source] Transvenous Parasympathetic Nerve Stimulation in the Inferior Vena Cava and Atrioventricular ConductionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2000PATRICK SCHAUERTE M.D. Parasympathetic Stimulation in the Inferior Vena Cava. Introduction: In previous reports, we demonstrated a technique for parasympathetic nerve stimulation (PNS) within the superior vena cava, pulmonary artery, and coronary sinus to control rapid ventricular rates during atrial fibrillation (AF). In this report, we describe another vascular site, the inferior vena cava (IVC), at which negative dromotropic effects during AF could consistently he obtained. Moreover, stimulation at this site also induced dual AV nodal electrophysiology. Methods and Results: PNS was performed in ten dogs using rectangular stimuli (0.1 msec/20 Hz) delivered through a catheter with an expandable electrode basket at its tip. Within 3 minutes and without using fluoroscopy, the catheter was positioned at an effective PNS site in the IVC at the junction of the right atrium. AF was induced and maintained by rapid atrial pacing. During stepwise increase of the PNS voltage from 2 to 34 V, a graded response of ventricular rate slowing during AF was observed (266 ± 79 msec without PNS vs 1,539 ± 2,460 msec with PNS at 34 V; P = 0.005 by analysis of variance), which was abolished by atropine and blunted by hexamethonium. In three animals, PNS was performed during sinus rhythm. Dual AV nodal electrophysiology was present in 1 of 3 dogs in control, whereas with PNS, dual AV nodal electrophysiology was observed in all three dogs. PNS did not significantly change sinus rate or arterial blood pressure during ventricular pacing. Conclusion: Stable and consistent transvenous electrical stimulation of parasympathetic nerves innervating the AV node can be achieved in the IVC, a transvenous site that is rapidly and readily accessible. The proposed catheter approach for PNS can be used to control ventricular rate during AF in this animal model. [source] Combination Therapy with Digoxin and Diltiazem Controls Ventricular Rate in Chronic Atrial Fibrillation in Dogs Better than Digoxin or Diltiazem Monotherapy: A Randomized Crossover Study in 18 DogsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 3 2009A.R.M. Gelzer Background: Atrial fibrillation (AF) with excessively high ventricular rates (VR) occurs in dogs with advanced heart disease. Rate control improves clinical signs in these patients. Optimal drug therapy and target VR remain poorly defined. Hypothesis: Digoxin-diltiazem combination therapy reduces VR more than either drug alone in dogs with high VR AF. Animals: Eighteen client-owned dogs (>15 kg) with advanced heart disease, AF, and average VR on 24-hour Holter > 140 beats per minute (bpm). Methods: After baseline Holter recording, dogs were randomized to digoxin or diltiazem monotherapy, or combination therapy. Repeat Holter evaluation was obtained after 2 weeks; dogs were then crossed over to the other arm (monotherapy or combination therapy) for 2 weeks and a third Holter was acquired. Twenty-four hour average VR, absolute and relative VR changes from baseline, and percent time spent within prespecified VR ranges (>140, 100,140, and <100 bpm) were compared. Correlations between serum drug concentrations and VR were examined. Results: Digoxin (median, 164 bpm) and diltiazem (median, 158 bpm) decreased VR from baseline (median, 194 bpm) less than the digoxin-diltiazem combination (median, 126 bpm) (P < .008 for each comparison). With digoxin-diltiazem, VR remained <140 bpm for 85% of the recording period, but remained >140 bpm for 88% of the recording period with either monotherapy. Serum drug concentrations did not correlate with VR. Conclusions and Clinical Importance: At the dosages used in this study, digoxin-diltiazem combination therapy provided a greater rate control than either drug alone in dogs with AF. [source] | ||||||||||