Ventricular rhythms
Andrew R Houghton in Making Sense of the ECG, 2019
Ventricular rhythms are those which arise from the ventricles, i.e. below the level of the atrioventricular node. This chapter discusses the diagnostic ECG features for ventricular ectopic beats (also known as ventricular extrasystoles, ventricular premature complexes, ventricular premature beats or premature ventricular contractions), accelerated idioventricular rhythm, monomorphic ventricular tachycardia, polymorphic ventricular tachycardia, fascicular ventricular tachycardia and ventricular fibrillation. The chapter includes a discussion on how to distinguish between ventricular tachycardia and supraventricular tachycardia with aberrant conduction, and in particular the diagnostic importance of identifying ECG evidence of atrioventricular dissociation (as indicated by independent P wave activity, fusion beats or capture beats). Potential causes and key management steps are presented for each of the ventricular arrhythmias discussed in the chapter.
The P wave
Andrew R Houghton in Making Sense of the ECG, 2019
After determining the heart rate, rhythm and axis, examine each wave of the electrocardiogram (ECG) in turn, beginning with the P wave. Atrial depolarization is therefore normally so regular that it is easy to predict when the next P wave is going to appear. A lack of coordinated atrial depolarization occurs in atrial fibrillation, and this is the commonest reason for P waves to be truly absent from the ECG. Even in sinus tachycardia, at high heart rates the P waves may start to overlap with the T waves of the previous beats, making them hard to identify. The wave of depolarization normally spreads through the atria from the sinoatrial node to the atrioventricular node. The P wave becomes broad because the enlarged left atrium takes longer than normal to depolarize. Prolongation of P wave duration and also increased P wave dispersion have been identified as predictors of risk for the development of atrial fibrillation.
Conduction of electrical activity in the heart
Burt B. Hamrell in Cardiovascular Physiology, 2018
Ions move freely from myocyte to myocyte through gap junctions. Electrical charges carried by ions easily move from cardiac muscle cell to cardiac muscle cell and throughout normal heart muscle tissue. The electrical response of heart muscle is all or none, which means that an adequate stimulus to one healthy atrial myocyte will result in an action potential that is then transmitted to all the other atrial myocytes. Each myocyte is a separate cell with its own cell machinery and bounded by a membrane, the sarcolemma. But the low myocyte-to-myocyte electrical resistance at the gap junctions and easy myocyte-to-myocyte transmission of action potentials result in the heart behaving as if it were a syncytium. Electrical activity is conducted from atrial myocyte to atrial myocyte throughout the right and left atria primarily via gap junctions. The Atrioventricular node is in the right atrium at the bottom of the interatrial septum near the opening of the coronary sinus.
An Unusual Cause of Palpitations Requiring Atrioventricular Node Ablation and Pacemaker Therapy
Published in Blood Pressure, 1997
Charalampos Lydakis, Ken Hollinrake, Gregory Yh Lip
Lydakis C, Hollinrake K, Lip GYH. An unusual cause of palpitations requiring atrioventricular node ablation and pacemaker therapy. We report the unique case of a patient who complained of palpitations resistant to many antiarrhythmic treatment strategies, finally requiring treatment with atrioventricular node ablation and pacemaker implantation. A pheochromocytoma was eventually diagnosed, 16 years after the onset of her symptoms.
Sudden Death from Occlusive Disease of the Atrioventricular Node Artery
Published in Pathology, 1981
Kenneth R. Anderson, J. Bowie, A. G. Dempster, J. F. Gwynne
Non-atherosclerotic focal occlusive disease of the atrioventricular node artery was the only significant pathological lesion found at autopsy in 2 individuals aged 40 and 17 yr who died suddenly and unexpectedly. The cases were observed amongst 115 autopsies categorized as sudden cardiac death and performed during an 18 mth period. Occlusive disease of the atrioventricular node artery is a poorly documented entity of unknown aetiology and pathogenesis. We believe it is a more frequent pathological finding in sudden cardiac death than has been previously recognized and that it deserves more attention than it currently receives.
Postcardiac injury syndrome complicating radiofrequency ablation of the atrioventricular node
Published in Acute Cardiac Care, 2006
A. Kibos, G. Pacouret, D. Babuty, A. De Labriolle, L. Fauchier, B. Charbonnier
Radiofrequency ablation, which is increasingly used in the treatment of cardiac arrhythmia, can be complicated with pericardial effusion and one case of Dressler's syndrome has already been reported after an atrioventricular pathway ablation. This case reports a second case complicating an atrioventricular node radiofrequency ablation procedure.