…bundle branch block (C). One large box equals 100 ms at paperspeed 25 mm/s. Figure 2 shows 12 lead ECGs demonstrating right and left…

Conduction defects ECG Intraventricular conduction delay (defect): constellations of bundle branch blocks and fascicular blocks (hemiblocks) This chapter discusses intraventricular conduction delays (defects), which are…

…and the fascicles extend into the fine Purkinje network, which spreads throughout the myocardium. Figure 2 illustrates a normal ECG, a left bundle branch block…

…His bundle, which bifurcates into the left and right bundle branches. The left bundle branch further subdivides into two fascicles. From these branches and fascicles…

…atrial impulse reaches the atrioventricular node (or bundle of His) while it is completely refractory, the impulse will be blocked and no QRS complex appears…

…left bundle branch block (LBBB) or pacemaker rhythms. Atrial fibrillation or atrial flutter Patients on medications such as nitrates, beta blockers, or calcium channel blockers…

…abnormal ventricular depolarization (e.g sinus tachycardia with simultaneous left bundle branch block). P wave and PR interval Checklist P wave is always positive in…

…sinus tachycardia with simultaneous left bundle branch block). 2. P wave morphology and PR interval Assess P wave morphology and PR interval P wave is…

…excitable pathway whereas it will be blocked in the refractory pathway. If the refractory pathway has repolarized before the impulse has left the atrioventricular node…

… OM2, 14), the left posterior descending artery (LPDA, 15), and the left posterolateral branch (LPLB, 18). (B) Corresponding CT schematic with coronary artery origins from…

…CTI) at the inferior boundary, and ascends in a caudocranial direction along the interatrial septum. The left atrium is activated passively. The upper boundary of…

…elevation. Symptoms can be dramatic, but many episodes are clinically silent and detected only by electrocardiographic monitoring. Syncope may result from transient atrioventricular block, asystole…

…and by the left circumflex artery in the remainder. The atrioventricular node is supplied by the right coronary artery in 90% (right dominant system) of…

…control or worsening hemodynamics, and signs of digoxin toxicity. Toxicity can manifest as sinus bradycardia or sinus arrest, atrioventricular (AV) node block, and junctional, fascicular…

…wall (these arteries branch of after the right marginal artery) may be given off by the RCA (and otherwise the LCx). Left anterior descending coronary…

…ECG tracings and it is explained by the fact that the atria are depolarized sequentially, with the right atrium being depolarized before the left atrium…

…Nausea. Atrioventricular blocks (AV blocks). Orthostatic hypotension. Paresthesias (scalp tingling). Bronchospasm. Caution • Avoided in hypertensive emergencies with left ventricular failure (due to negative inotropic effect)…

…P wave and the onset of the QRS complex is called the PR segment and it reflects the slow impulse conduction through the atrioventricular node…

…the vein atrial and the atrio ventricular connections, the relationship between the ventricles, the ventriculo arterial connection and the relationship of the great arteries (segmental…

…etc .) are warranted. Management of AV blocks aims to restore atrioventricular conduction either pharmacologically or by means of artificial pacemakers. Both methods may be used…

…ECG, clinical characteristics and management Pre excitation The atrioventricular node and bundle of His are normally the only communication between the atria and the ventricles…

…be located anywhere between the atrioventricular node and the bifurcation of the bundle of His. If there are cells (with automaticity) distal to the block…

…A high suspicion of intermittent infrahisian block should be maintained, particularly in older patients and those exhibiting a bundle branch block (BBB) or an intraventricular…

…atrioventricular (AV) or intraventricular blocks. Isolated sinus bradycardia in the early hours following infarction may be associated with hemodynamic compromise. More broadly, bradyarrhythmic arrest and…

…a decrease in Vmax. Consequently, shifts in the pacemaker site within the sinus node and sinus exit block may occur. In humans, adenosine initially slows…

…Relevant abnormalities include bradyarrhythmias or tachyarrhythmias, AV block, acute myocardial ischemia, old myocardial infarction, long QT, and bundle branch block. Cardiac monitoring is indicated for…

…the block. The nature of these blocks is very similar to the atrioventricular (AV) blocks. Importantly, first degree sinoatrial block and third degree sinoatrial block…

…dose. Electrophysiology Sotalol prolongs the effective refractory periods of the atrium, atrioventricular (AV) node, His Purkinje system, and ventricle. It extends the A H interval…

…wave. Increasing the paper speed to 50 mm/s or applying carotid massage (which increases the atrioventricular block) will be helpful in such situations. Figure…

…in the sinoatrial node discharge an action potential that spreads as an electrical impulse through the atria and – via the atrioventricular node – to the ventricles…

…focus arises in or near the bundle of His, the impulse may be delivered to both bundle branches and subsequently the entire ventricular myocardium normally…

…action potential, automaticity and electrical vectors Video lecture The following video lecture summarises this chapter. The action potential includes a depolarization (activation) followed by a…

…digoxin. Increased Vagus activity diminishes the automaticity in the sinoatrial node (which lowers heart rate) and also slows conduction over the atrioventricular (AV) node. The…

…pause should be considered abnormal, and the following differential diagnoses are at hand: Sinus node dysfunction. Side effects of drugs (diltiazem, verapamil, beta blockers, digitalis)…

…flutter. Each P wave is followed by a QRS complex; atrioventricular block is uncommon unless the patient is receiving digoxin. The ventricular rate is regular…

…physiological effects of exercise are summarized below. Parasympathetic fibers innervate both the sinoatrial (SA) node and atrioventricular (AV) node. Parasympathetic stimulation reduces the automaticity in…

…impulses are discharged and whether there is a concomitant bundle branch block. Escape rhythms with narrow QRS complexes indicate that the block and the ectopic…

…contraindication) . Irregular wide complex tachycardia is most often due to atrial fibrillation with wide QRS complexes due to bundle branch blocks or other conduction defects…

…in 90% of the cases and the bundle of His in 10% of cases. If the ECG displays first degree AV block (PR interval ≥0…

…is completely blocked, which manifests on the ECG as a P wave not followed by a QRS complex. This cycle repeats itself over and over…

…IV every 3 to 6 hours. Adverse effects Vomiting. Dizziness. Nausea. Atrioventricular blocks (AV blocks). Orthostatic hypotension. Paresthesias (scalp tingling). Bronchospasm. Caution • Avoided in hypertensive…

…the PR interval is greater than 220 msec, first degree AV block is manifest and it is considered a pathological finding (Figure 4, second panel)…