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Electrocardiogram
Published in Burt B. Hamrell, Cardiovascular Physiology, 2018
In first degree atrioventricular block every P wave is followed by ventricular depolarization. In second degree atrioventricular block there are instances where conduction from atria to ventricles fails to occur and a ventricular action potential does not follow a P wave. The cause varies and can be due to such things as drug toxicity, ischemia, and inflammation affecting some part of the conduction system. Second degree heart block also can be related to the effects of the autonomic nervous system on a normal atrioventricular node. There are two types of second degree atrioventricular block.
Arrhythmia
Published in Lauren A. Plante, Expecting Trouble, 2018
Melissa Westermann, Afshan B. Hameed
There is no association between first- and second-degree atrioventricular block or complete heart block and pregnancy. Second-degree Mobitz type 1 (Wenckebach) is more commonly seen and is usually considered benign. It rarely progresses to complete heart block and is therefore conservatively managed. Mobitz type 2 is uncommon but can progress to complete heart block, and, therefore, a permanent pacemaker is often recommended even in asymptomatic patients. Complete heart block is rarely diagnosed for the first time in pregnancy and is usually associated with prior cardiac surgery, CHD, myocardial infarction, cardiomyopathy, drugs, metabolic imbalance, and acute infection (48). However, 30% of cases remain undetectable until adulthood (49). In pregnancy, pacemakers are usually recommended for symptoms or in the presence of slow, wide complex escape rhythm (50).
Practice Paper 8: Answers
Published in Anthony B. Starr, Hiruni Jayasena, David Capewell, Saran Shantikumar, Get ahead! Medicine, 2016
Anthony B. Starr, Hiruni Jayasena, David Capewell
In Stokes–Adams attacks, there is a sudden loss of consciousness with pallor and a death-like appearance. They are due to transient ventricular asystole, which can occur in complete heart block or Mobitz type II second-degree atrioventricular block. Convulsions can occur if there is prolonged asystole due to cerebral ischaemia, but, in contrast to epileptic seizures, recovery is rapid. When the heart starts re-beating, there is a characteristic facial flush. Management of Stokes–Adams attacks is by pacemaker insertion. If untreated, there is a 50% risk of mortality within a year.
Glucose-lowering agents and risk of cardiac arrhythmias
Published in Acta Cardiologica, 2023
A recent meta-analysis (published in the Acta Cardiologica) of seven CVOTs compared the cardiovascular efficacy and safety of GLP-1RAs versus placebo in patients with T2D and high cardiovascular risk. The conclusion was that these glucose-lowering agents do not significantly affect the risk of major cardiac arrhythmias [2]. Treatment with GLP-1RAs did not provide significant benefit in the risk for AF (risk ratio or RR = 0.81; 95% confidence interval – CI − 0.78–1.15), AFL (RR = 0.79; 0.53–1.16) and atrial tachycardia (RR = 0.63; 0.10–3.90). Similarly, no negative or positive signal could be observed regarding ventricular fibrillation (RR = 0.99; 0.48–2.04), ventricular tachycardia (RR = 1.41; 0.87–2.28) and ventricular extrasystoles (RR = 1.37; 0.56–3.30). The heterogeneity was rather low with I2 ranging from 0 to 24%, except for AF that showed a higher I2 of 51%. This study also did not show any difference concerning sinus node dysfunction, second-degree atrioventricular block or complete atrioventricular block [2]. One limitation of this work is that GLP-1RAs were compared to placebo and not with other active glucose-lowering agents commonly used in clinical practice. Therefore, only indirect comparisons could be drawn from the scientific literature.
Syncope in patients with transthyretin amyloid cardiomyopathy: clinical features and outcomes
Published in Postgraduate Medicine, 2022
Gonzalo Barge-Caballero, Eduardo Barge-Caballero, Manuel López-Pérez, Raquel Bilbao-Quesada, Eva González-Babarro, Inés Gómez-Otero, Andrea López-López, Mario Gutiérrez-Feijoo, Alfonso Varela-Román, Carlos González-Juanatey, Óscar Díaz-Castro, María G. Crespo-Leiro
Syncope was considered related to a structural cardiac cause in patients who presented, coexisting with ATTR-CA, an underlying structural disorder of the heart or the great vessels, which is typically recognized as a primary hemodynamic cause of syncope, like severe aortic stenosis, cardiac tamponade, obstructive hypertrophic cardiomyopathy, aortic dissection or pulmonary embolism. Arrhythmic syncope was diagnosed when the transient loss of consciousness was coincident in time and attributable to a cardiac rhythm disturbance, which is a recognized primary cause of syncope, either bradyarrhythmic – Mobitz II second-degree atrioventricular block, third-degree atrioventricular block, asystole, prolonged sinus arrest, slow junctional rhythm, slow idioventricular rhythm – or tachyarrhythmic – sustained ventricular tachycardia, supraventricular tachycardia with fast ventricular rate–. In this study, the term cardiac syncope makes reference to syncopal episodes due to either structural cardiac causes or cardiac arrhythmias.
Flecainide toxicity in renal failure
Published in Baylor University Medical Center Proceedings, 2018
Rogin Subedi, Ryan K. Dean, Arbind Chaudhary, Tamas Szombathy
Flecainide toxicity manifests on the electrocardiogram similar to tricyclic antidepressant toxicity, because both are sodium channel inhibitors. It causes PR interval prolongation, widening of QRS, and first- and second-degree atrioventricular block.6,10 The QT interval may prolong as a concomitant effect of the QRS widening.9,11 Toxicity is suspected when the QRS duration increases by 50% or the PR interval is prolonged by 30%.11 A prominent R wave (amplitude ≥3 mm) and an R wave to S wave ratio ≥0.7 in lead aVR are the most sensitive predictors of arrhythmias or seizures in patients with tricyclic antidepressant overdoses,12,13 which may help in diagnosing flecainide toxicity.