…electrolyte disorders 1. Sodium Increased (hypernatremia) and decreased (hyponatremia) sodium levels do not have any effect on the ECG, nor cardiac rhythm, or impulse conduction…

…seconds). The QRS complex is wide simply because the ectopic impulses that cause these rhythms spread partially or entirely outside of the ventricular conduction system…

…EAT, or atrial tachycardia) arises when an ectopic focus within the atria generates electrical impulses at a rate exceeding that of the sinoatrial (SA) node…

Cardiology Substance : Adenosine Brand names : Adenocor Mechanism of action Adenosine works by slowing down the impulse transmission through the atrioventricular (AV) node, thereby interfering with…

…branch block. Commonly, the premature atrial impulse arrives before one of the bundle branches has repolarized, which leads to a bundle branch block. This type…

…fascicular block, the myocardium without fascicular supply will depend on impulses spreading from other parts of the ventricle (where the fascicle is intact). Figure 1…

…automaticity (refer to Cardiac Electrophysiology). The electrical impulse propagates through the atria via the internodal pathways and Bachmann's bundle, eventually reaching the atrioventricular (AV…

…the ventricles with the same rate. This occurs if ventricular stimulation is set to be triggered by the atrial impulse. Another cause of pacemaker mediated…

…Such pathways may be conductive, such that they can transmit the atrial impulse to the ventricles directly. These pathways are termed accessory pathways (or bundle…

…anatomical or functional dysfunction in the right bundle branch, such that the electrical impulse is blocked. Figure 1 illustrates the components of the ventricular conduction…

…around 20–40 beats/min. If the impulses are discharged from fibers proximal to the bifurcation of the bundle of His, QRS complexes will be…

…activity). Sinus arrest & sinus pause (intermittent failures to discharge impulses). Sinoatrial block (delayed or blocked impulse conduction between the sinoatrial node and the atrium). All…

…with identical waveforms on the ECG. The similarity of the waveforms indicates that the origin of the impulse is the same. The sinoatrial (SA) node…

…More broadly, bradyarrhythmic arrest and asystole represent severe manifestations of impulse generation or conduction failure. The pathophysiology of these events may stem from reversible causes…

…and the start of the QRS complex. The PR interval determines whether impulse transmission from atria to ventricles is normal. The isoelectric (flat) line between…

…by an ectopic focus in the atria. The impulse from the premature beat reaches the His Purkinje system early, while some fibers are still refractory…

…potential that spreads as an electrical impulse through the atria and – via the atrioventricular node – to the ventricles. As the impulse spreads through the myocardium…

…increases the heart rate by increasing the automaticity in the sinoatrial node), and positive bathmotropic effect (i.e increased impulse transmission through the myocardium). Thus…

…as in LBBB, the left ventricle receives the depolarizing impulse from the right ventricle (where the pacemaker delivers the pulses). The depolarizing wave spreads outside…

…defect are used interchangeably. Normal and abnormal intraventricular impulse conduction The intraventricular conduction system is composed of the His Purkinje system. More precisely this system…

…However, impulses are occasionally discharged in the atrioventricular node or by cells near the node. The following must be noted: There are cells with pure…

…displaying identical waveforms on the ECG. The similarity of the waveforms indicates that the origin of the impulse is the same. The sinoatrial (SA) node…

…the AV node and the His Purkinje system, which transmit electrical impulses from the atria to the ventricles. Conduction through the AV node is intentionally…

…The premature ventricular impulse replaces a sinus beat and induces a delay to the next sinus beat (the RR interval is increased after a premature…

…to AV Blocks). Second degree AV block is defined by the intermittent failure of atrial impulses to conduct to the ventricles, resulting in some P…

…from ECG to clinical management Sinoatrial (SA) block implies that the impulses discharged in the sinoatrial node are either not conducted to the atria or…

…the propagation of depolarization across the cells. Electrical potential differences arise as the electrical impulse travels through the heart. Electric potential difference is defined as…

…of ventricular activation (depolarization). The PR interval reflects whether impulse conduction from the atria to the ventricles is normal. The PR interval must not be…

…The test presupposes that the patient has spontaneous nystagmus at the time of examination and that the examiner is experienced with the head impulse test…

…Wenckebach block) : repeated cycles of gradually increasing PR interval until an atrial impulse (P wave) is blocked in the atrioventricular node and the QRS complex…

…cause: Diminished heart sounds Disappearance of the friction rub Loss of the apical impulse Electrical alternans on the ECG Compression of the left lung base

…refractory. If an atrial impulse reaches the atrioventricular node when there are two pathways, one being refractory and the other capable of conducting the impulse…

…rapid impulse transmission in the network. Cells of the atrioventricular node, on the contrary, have a low density of gap junctions, explaining the slow impulse…

…are depolarized normally; this can only be the case if the impulse (which depolarizes the ventricles) passes through the bundle of His, and hence it…

…should always suspect digoxin as the trigger of an arrhythmia (in patients using digoxin) if there is evidence of increased automaticity and diminished impulse conduction …

…the QRS complex. The PR interval is assessed in order to determine whether impulse conduction from the atria to the ventricles is normal. The flat…

…as it does not represent a true conduction block but rather a delay in the propagation of electrical impulses from the atria to the ventricles…

…Wenckebach block) : repeated cycles of gradually increasing PR interval until an atrial impulse (P wave) is blocked in the atrioventricular node and the QRS complex…

…prolonged until one atrial impulse (P wave) is blocked in the AV node. Generally not. AV block II, type 2 Some atrial impulses (P waves…

…with identical waveforms on the ECG. The similarity of the waveforms indicates that the origin of the impulse is the same. The sinoatrial (SA) node…

…the atrial pulse to the ventricles. Impulse transmission is rapid through the bundle of His and the Purkinje fibers, such that virtually all ventricular myocardium…

…by impulses spreading through the left and right bundle branch, which branches out into the Purkinje network (refer to Cardiac Electrophysiology: The Action Potential). Impulse…

…automaticity) in the sinoatrial node. This simply means that the sinoatrial node discharges electrical impulses at a higher frequency than normal. Similar to sinus rhythm…

…3. In third degree AV block, no atrial impulses are conducted to the ventricles. The atria and the ventricles are electrically dissociated from each other…

…right atrium and it typically loops around the tricuspid valve. Impulses spread rapidly through the atria from this re entry circuit. Examples of atrial flutter…

…infarction. Sinus Node Dysfunction (SND) – Sinus node dysfunction implies that the cells of the sinoatrial node are defective and fail to generate electrical impulses. Side…

…constant PR interval. Third degree AV block: all atrial impulses are blocked in the AV conduction system and therefore cannot activate the ventricles. An escape…

…mitrale ). If the atria are depolarized by impulses generated by cells outside of the sinoatrial node (i.e by an ectopic focus), the morphology of…