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Conduction Abnormalities (conduction + abnormality)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Connexin40-Deficient Mice Exhibit Atrioventricular Nodal and Infra-Hisian Conduction Abnormalities

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2000
BRIAN A. VANDERBRINK B.S.
AV Nodal and Infra-Hisian Conduction in Cx40 Mice. Introduction: Previous electrophysiologic investigations have described AV conduction disturbances in connexin4(Cx40)-deficient mice. Because expression or(Cx40 occurs predominantly in the atria and His-Purkinje system of the mouse heart, the AV conduction disturbances were thought to be secondary to disruption in His-Pnrkinje function. However, the lack of a His-bundle electrogram recording in the mouse has limited further investigation of the importance of Cx40. Using a novel technique to record His-bundle recordings in Cx40-deficient mice, we define the physiologic importance of defciencies in Cx40. Methods and Results: Ten Cx40 -/- mice and 11 Cx40+/+ controls underwent a blinded, in vivo, closed chest electrophysiology study at 9 to 12 weeks of age. In the Cx40+/+ mice, the PR interval was significantly longer compared with Cx40+/+ mice (44.6 ± 6.4 msec vs 36.0 ± 4.1 msec, P = 0.002). Not only the HV interval (14.0 ± 3.0 msec vs 10.4 ± 1.2 msec, P = 0.003) but also the AH interval (33.2 ± 4.8 msec vs 27.1 ± 3.7 msec, P = 0.006), AV Wenckebach cycle lengths, and AV nodal effective and functional refractory periods were prolonged in Cx40 -/- compared with Cx40+/+ mice. Conclusion: Cx40-deficient mice exhibit significant delay not only in infra-Hisian conduction, as would be expected from the expression of Cx40 in the His-Purkinje system but also in the electrophysiologic parameters that reflect AV nodal conduction. Our data suggest a significant role of Cx40 in atrionodal conduction and/or in proximal His-bundle conduction, [source]

Scn3b knockout mice exhibit abnormal sino-atrial and cardiac conduction properties

ACTA PHYSIOLOGICA, Issue 1 2010
P. Hakim
Abstract Aim:, In contrast to extensive reports on the roles of Nav1.5 , -subunits, there have been few studies associating the , -subunits with cardiac arrhythmogenesis. We investigated the sino-atrial and conduction properties in the hearts of Scn3b,/, mice. Methods:, The following properties were compared in the hearts of wild-type (WT) and Scn3b,/, mice: (1) mRNA expression levels of Scn3b, Scn1b and Scn5a in atrial tissue. (2) Expression of the ,3 protein in isolated cardiac myocytes. (3) Electrocardiographic recordings in intact anaesthetized preparations. (4) Bipolar electrogram recordings from the atria of spontaneously beating and electrically stimulated Langendorff-perfused hearts. Results:,Scn3b mRNA was expressed in the atria of WT but not Scn3b,/, hearts. This was in contrast to similar expression levels of Scn1b and Scn5a mRNA. Immunofluorescence experiments confirmed that the ,3 protein was expressed in WT and absent in Scn3b,/, cardiac myocytes. Lead I electrocardiograms from Scn3b,/, mice showed slower heart rates, longer P wave durations and prolonged PR intervals than WT hearts. Spontaneously beating Langendorff-perfused Scn3b,/, hearts demonstrated both abnormal atrial electrophysiological properties and evidence of partial or complete dissociation of atrial and ventricular activity. Atrial burst pacing protocols induced atrial tachycardia and fibrillation in all Scn3b,/, but hardly any WT hearts. Scn3b,/, hearts also demonstrated significantly longer sinus node recovery times than WT hearts. Conclusion:, These findings demonstrate, for the first time, that a deficiency in Scn3b results in significant atrial electrophysiological and intracardiac conduction abnormalities, complementing the changes in ventricular electrophysiology reported on an earlier occasion. [source]

Effect of insulin infusion on electrocardiographic findings following acute myocardial infarction: importance of glycaemic control

DIABETIC MEDICINE, Issue 2 2009
R. M. Gan
Abstract Aims, To determine the effects of insulin infusion and blood glucose levels during acute myocardial infarction (AMI) on electrocardiographic (ECG) features of myocardial electrical activity. Methods, ECGs at admission and 24 h were examined in a randomized study of insulin infusion vs. routine care for AMI patients with diabetes or hyperglycaemia. Results were analysed according to treatment allocation and also according to average blood glucose level. Results, ECG characteristics were similar at admission in both groups. Patients allocated to conventional treatment had prolongation of the QT interval (QTc) after 24 h but those receiving infused insulin did not. In patients with a mean blood glucose in the first 24 h > 8.0 mmol/l, new ECG conduction abnormalities were significantly more common than in patients with mean blood glucose , 8.0 mmol/l (15.0% vs. 6.0%, P < 0.05). Conclusions, Prevention of QTc prolongation by administration of insulin may reflect a protective effect on metabolic and electrical activity in threatened myocardial tissue. Abnormalities of cardiac electrical conduction may also be influenced by blood glucose. [source]

Hypertonic Saline Treatment of Severe Hyperkalemia in Nonnephrectomized Dogs

ACADEMIC EMERGENCY MEDICINE, Issue 9 2000
Justin 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]

Second-degree atrioventricular block (Mobitz Type I) in an adolescent with anorexia nervosa: Intrinsic or acquired conduction abnormality

INTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 6 2009
Nuray Ö. Kanbur MD
Abstract Anorexia nervosa (AN) can cause both functional and structural cardiac complications, including a variety of different conduction abnormalities. This is the first case report of symptomatic diurnal second-degree atrioventricular (AV) block (Mobitz Type I) in an adolescent with AN. We present a 12-year-old girl with AN, restrictor sub-type who reported cardiac symptoms during weight gain, at the time of the initial diagnosis of AV block. Second-degree AV block (Mobitz Type I) is discussed as a possible complication of the AN, as well as being an intrinsic conduction system disease. © 2009 by Wiley Periodicals, Inc. Int J Eat Disord 2009 [source]

Identification and Ablation of Three Types of Ventricular Tachycardia Involving the His-Purkinje System in Patients with Heart Disease

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2004
GUSTAVO LOPERA M.D.
Introduction: Ventricular tachycardia (VT) with involvement of the His-Purkinje system (HPS) can be difficult to recognize in patients with heart disease, but it may be particularly susceptible to ablation targeting the HPS. This study defines the incidence and types of HPS involvement in VT. Methods and Results: Involvement of the HPS was sought during electrophysiologic study with catheter mapping in 234 consecutive patients referred for catheter ablation of recurrent VT associated with heart disease. HPS VT was observed in 20 (8.5%) patients (mean ejection fraction 29%± 17%); in 9 (11%) of 81 patients with nonischemic heart disease and 11 (7.1%) of 153 patients with coronary artery disease (P = NS). Three types of HPS VT were observed: 16 patients (group 1) had typical bundle branch reentry, 2 patients (group 2) had bundle branch reentry and interfascicular reentry, and 2 patients (group 3) had VT consistent with a focal origin in the distal HPS. In all three groups, the VT QRS had morphologic similarity to the sinus rhythm QRS. Ablation of HPS VT was successful in all patients in whom it was attempted but produced high-degree AV block in 6 (30%). In 12 patients (60%), other VTs due to reentry through scar also were inducible. Conclusion: Involvement of the HPS in VT associated with heart disease has three distinct clinical forms, all of which are susceptible to ablation. Ablation often is not sufficient as the sole therapy due to other induced VT's and conduction abnormalities, requiring pacemaker and/or defibrillator implantation. (J Cardiovasc Electrophysiol, Vol. 15, pp. 52-58, January 2004) [source]

Maturational Atrioventricular Nodal Physiology in the Mouse

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2000
COLIN T. MAGUIRE B.S.
Mouse AV Nodal Maturation. Introduction: Dual AV nodal physiology is characterized by discontinuous conduction from the atrium to His bundle during programmed atrial extrastimulus testing (A2V2 conduction curves), AV nodal echo beats, and induction of AV nodal reentry tachycardia (AVNRT). The purpose of this study was to characterize in vivo murine maturational AV nodal conduction properties and determine the frequency of dual AV nodal physiology and inducible AVNRT. Methods and Results: A complete transvenous in vivo electrophysiologic study was performed on 30 immature and 19 mature mice. Assessment of AV nodal conduction included (1) surface ECG and intracardiac atrial and ventricular electrograms; (2) decremental atrial pacing to the point of Wenckebach block and 2:1 conduction; and (3) programmed premature atrial extrastimuli to determine AV effective refractory periods (AVERP), construct A2V2 conduction curves, and attempt arrhythmia induction. The mean Wenckebach block interval was 73 ± 12 msec, 2:1 block pacing cycle length was 61 ± 11 msec, and mean AVERP100 was 54 ± 11 msec. The frequency of dual AV nodal physiology increased with chronologic age, with discontinuous A2V2, conduction curves or AV nodal echo heats in 27% of young mice < 8 weeks and 58% in adult mice (P = 0.03). Conclusion: These data suggest that mice, similar to humans, have maturation of AV nodal physiology, hut they do not have inducible AVNRT. Characterization of murine electrophysiology may be of value in studying genetically modified animals with AV conduction abnormalities. Furthermore, extrapolation to humans may help explain the relative rarity of AVNRT in the younger pediatric population. [source]

Childhood multifocal acquired demyelinating sensory and motor neuropathy

MUSCLE AND NERVE, Issue 6 2008
Hiroyuki Wakamoto MD
Abstract We report the first pediatric cases of multifocal acquired demyelinating sensory and motor neuropathy with electrophysiologic evidence of proximal conduction abnormalities but no definite conduction block. Intravenous immunoglobulin caused clinical improvement followed by long-term remission without maintenance therapy; one patient has exhibited a monophasic course and the other has had a single relapse during the last 5 years. These cases suggest that there may be a long-term sustained beneficial effect of intravenous immunoglobulin therapy for children with this neuropathy. Muscle Nerve, 2008 [source]

Abnormal Atrioventricular Node Conduction and Atrioventricular Nodal Reentrant Tachycardia in Patients Older Versus Younger Than 65 Years of Age

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2009
MIHAELA GRECU M.D.
Study Objective: We examined the possible role of atrioventricular node (AVN) conduction abnormalities as a cause of AVN reentrant tachycardia (RT) in patients >65 years of age. Study Population: Slow pathway radiofrequency catheter ablation (RFCA) was performed in 104 patients. Patients in group 1 (n = 14) were >65 years of age and had AV conduction abnormalities associated with structural heart disease. Patients in group 2 (n = 90) were <65 years of age and had lone AVNRT. Results: Patients in group 1 versus group 2 (66% vs. 46% men) had a first episode of tachycardia at an older age than in group 2 (68 ± 16.8 vs 32.5 ± 18.8 years, P = 0.007). The history of arrhythmia was shorter in group 1 (5.4 ± 3.8 vs 17.5 ± 14, P = 0.05) and was associated with a higher proportion of patients with underlying heart disease than in group 2 (79% vs 3%, P < 0.001). The electrophysiological measurements were significantly shorter in group 2: atrial-His interval (74 ± 17 vs 144 ± 44 ms, P = 0.005), His-ventricular (HV) interval (41 ± 5 vs 57 ± 7 ms, P = 0.001), Wenckebach cycle length (329 ± 38 vs 436 ± 90 ms, P = 0.001), slow pathway effective refractory period (268 ± 7 vs 344 ± 94 ms, P = 0.005), and tachycardia cycle length (332 ± 53 vs 426 ± 56 ms, P = 0.001). The ventriculoatrial block cycle length was similar in both groups. The immediate procedural success rate was 100% in both groups, and no complication was observed in either group. One patient in group 2 had recurrence of AVNRT. One patient with a 98-ms HV interval underwent permanent VVI pacemaker implantation before RFCA procedure. Conclusion: In patients undergoing RFCA for AVNRT at >65 years of age had a shorter history of tachycardia-related symptoms than patients with lone AVNRT. The longer AVN conduction intervals and refractory period might explain the late development of AVNRT in group 1. [source]

Delayed Occurrence of Unheralded Phase IV Complete Heart Block After Ethanol Septal Ablation for Symmetric Hypertrophic Obstructive Cardiomyopathy

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2006
JOANNA J. WYKRZYKOWSKA
Ethanol septal ablation has emerged as a less invasive alternative to surgical myomectomy for treatment of asymmetric hypertrophic obstructive cardiomyopathy (ASH). The procedure has very low mortality, but high-degree AV conduction block is a frequent complication. Prior studies have documented baseline left bundle branch block and high volume of ethanol injection (greater than 4 mL) as risk factors. Complete heart block is often preceded by postprocedure conduction abnormalities and generally develops within 48 hours after ethanol ablation. We present a unique case of a patient with symmetric hypertensive hypertrophic obstructive cardiomyopathy (SHOCM) who developed phase IV complete heart block >96 hours postprocedure without preceding conduction abnormalities or other classic risk factors.3 [source]

Protective effect of Lycium barbarum on doxorubicin-induced cardiotoxicity

PHYTOTHERAPY RESEARCH, Issue 11 2007
Yan-Fei Xin
Abstract The objective of this work was to explore the hypothesis that Lycium barbarum (LB) may be protective against doxorubicin (DOX)-induced cardiotoxicity through antioxidant-mediated mechanisms. Male SD rats were treated with distilled water or a water extract of LB (25 mg/kg, p.o.) daily and saline or DOX (5 mg/kg, i.v.) weekly for 3 weeks. Mortality, general condition and body weight were observed during the experiment. DOX-induced cardiotoxicity was assessed by electrocardiograph, heart antioxidant activity, serum levels of creatine kinase (CK) and aspartate aminotransferase (AST) and histopathological change. The DOX group showed higher mortality (38%) and worse physical characterization. Moreover, DOX caused myocardial injury manifested by arrhythmias and conduction abnormalities in ECG (increased QT and ST intervals and ST elevation), a decrease of heart antioxidant activity, an increase of serum CK and AST, as well as myocardial lesions. Pretreatment with LB significantly prevented the loss of myofibrils and improved the heart function of the DOX-treated rats as evidenced from lower mortality (13%), normalization of antioxidative activity and serum AST and CK, as well as improving arrhythmias and conduction abnormalities. These results suggested that LB elicited a typical cardioprotective effect on DOX-related oxidative stress. Furthermore, in vitro cytotoxic study showed the antitumor activity of DOX was not compromised by LB. It is possible that LB could be used as a useful adjunct in combination with DOX chemotherapy. Copyright © 2007 John Wiley & Sons, Ltd. [source]

The Effect of Topical Epinephrine on Peripheral Nerve Conduction,,§

THE LARYNGOSCOPE, Issue 10 2002
Quintessa Miller MD
Abstract Objective/Hypothesis The aim of the study was to determine the effect of direct application of epinephrine solution on peripheral nerve conduction latency and amplitude. It was hypothesized that epinephrine does not cause neurapraxia when a standard (1:10,000) solution is applied topically. Study Design Eleven animals were divided into two groups of five and six. Group I had their left sciatic nerves and group II had their right sciatic nerves treated with epinephrine-soaked patties. The contralateral nerves of each group served as controls. Methods Nerve conduction studies were performed at baseline and immediately, at 1 minute, and at 5 minutes after patty application. Results Latency was found to increase above baseline immediately after patty application (P = .003) for the epinephrine-treated and saline-treated groups. Furthermore, the amplitude at 5 minutes after patty application increased from baseline (P = .009) for both groups. These observed differences were below what is considered to be clinically significant. Conclusion Topical epinephrine at a standard solution (1:10,000) does not lead to clinically significant nerve conduction abnormalities. [source]

Characteristics of patients with abnormal stress technetium Tc 99m sestamibi SPECT studies without significant coronary artery diameter stenoses

CLINICAL CARDIOLOGY, Issue 11 2003
Peter Ammann M.D.
Abstract Background: Single-photon emission computed tomography (SPECT) sestamibi (MIBI) is an excellent tool for detection of coronary artery disease (CAD), preoperative risk assessment, and follow-up management after coronary revas-cularization. While the sensitivity of MIBI SPECT for detecting CAD has been reported to exceed 90%, the specificity ranges between 53,100%. Hypothesis: The study was undertaken to assess characteristics of patients with abnormal stress technetium Tc 99m sestamibi SPECT (MIBI) studies without significant coronary artery diameter stenoses (< 50%). Methods: Between January 1999 and November 2000, 270 consecutive patients were referred for coronary angiography due to reversible MIBI uptake defects during exercise. In 41 patients (15%; 39% women, mean age 59 ± 9 years), reversible MIBI uptake defects were assessed although coronary angiography showed no significant CAD. These patients were compared with age- and gender-matched patients with perfusion abnormalities (39% women, mean age 60 ± 9 years), due to significant CAD (coronary artery stenosis > 50%). Results: There were no significant differences between the two groups regarding body mass index, left bundle-branch block (LBBB), or method of stress test (dipyridamole in patients with LBBB or physical inactivity [n= 11] and exercise in all the others [n= 30]). Left ventricular hypertrophy (44 vs. 23%, p = 0.05) and left anterior fascicularblock (LAFB) (17 vs. 0%, p = 0.005) were more common in patients with perfusion abnormalities with no significant CAD, whereas ST-segment depression during exercise (17 vs. 37% p = 0.05) and angina during exercise (15 vs. 29%, p = 0.02) were significantly less common than in patients with abnormal MIBI perfusion studies and angiographically significant CAD. Sestamibi uptake defects during exercise were significantly smaller in patients without significant CAD than in matched controls with significant CAD (p < 0.0004). Conclusion: Of 270 consecutive patients, 41 (15%) referred to coronary angiography due to reversible MIBI uptake defects showed coronary artery stenoses <50%. Twenty-six (10%) of these presented angiographically normal coronary arteries. The significantly higher proportion of left ventricular hypertrophy and LAFB in patients with reversible MIBI uptake defects without significant CAD suggest microvascular disease, angiographically underestimated CAD, and conduction abnormalities as underlying mechanisms. [source]