Arrhythmias and EKGs Part 2 Outline 1

Arrhythmias and EKGs Part 2

Outline 1. Sinus Arrhythmia and Sick Sinus 2. 3. 4. Syndrome Multifocal Atrial Tachycardia Bigeminal Rhythms Preexcitation and AVRT

Mechanisms of Arrhythmogenesis

Sinus Arrhythmia Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7 th ed. , 2005. EKG Characteristics: Presence of sinus P waves Variation of the PP interval which cannot be q attributed to either SA nodal block or PACs When the variations in PP interval occur in phase with respiration, this is considered to be a normal variant. When they are unrelated to respiration, they may be caused by the same etiologies leading to sinus bradycardia.

Sick Sinus Syndrome Characterized by a collection of symptoms and ECG findings due to chronic dysfunction of the sinoatrial (SA) node: – Chronic and severe sinus bradycardia – Sinus pauses – Sinus arrhythmia – Complete sinus arrest – Progressive development of atrial arrhythmias (aflutter, a-fib, atrial tachycardia) Patients are usually elderly and present with lightheadedness and/or syncope, but it can also manifest as angina, dyspnea, and palpitations. About 50% of people with SSS also display some degree of dysfunction of the AV node

Sick Sinus Syndrome Sinus bradycardia (rate of ~43 bpm) with a sinus pause

Etiologies of Sick Sinus Syndrome More Common Sinus node firbosis Atherosclerosis of the SA artery Congenital heart disease Excessive vagal tone Drugs Less Common Familial SSS (due to mutations in SCN 5 A) Infiltrative diseases Pericarditis Lyme disease Hypothyroidism Rheumatic fever

Tachycardia-Bradycardia Syndrome Common variant of sick sinus syndrome severe bradycardia alternates with paroxysmal tachycardias, most often atrial fibrillation. There is usually a prolonged pause in the cardiac rhythm following cessation of the tachyarrhythmia.

Tachycardia-Bradycardia Syndrome Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7 th ed. , 2005. Abrupt termination of atrial flutter with variable AV block, followed by sinus arrest with a junctional escape beat.

Multifocal Atrial Tachycardia EKG Characteristics: Discrete P waves with at least 3 different morphologies. Atrial rate > 100 bpm. The PP, PR, and RR intervals all vary.

Bigeminal Rhythms Arrhythmias in which each normal sinus beat is followed by a premature contraction (PAC, PJC, or PVC). Results in a couplet rhythm which can be detected by pulse or auscultation. Generally benign

Atrial Bigeminy

Ventricular Bigeminy

Preexcitation is a condition characterized by an accessory pathway of conduction, which allows the heart to depolarize in an atypical sequence. The most common form of preexcitation is called Wolfe-Parkinson. White (WPW) syndrome, in which a direct atrioventricular connection allows the ventricles to begin depolarization while the standard action potential is still traveling through the AV node. ECG Characteristics of WPW: 1. Short PR interval 2. QRS prolongation 3. Delta wave

AV Reentrant Tachycardia (AVRT) In patients with WPW, a reentrant rhythm can be generated where the AV node serves as one arm of the reentrant circuit, and the accessory pathway as the other.

Types of AVRT Orthodromic AVRT (More common) – Narrow complex tachycardia in which the wave of depolarization travels down the AV node and retrograde up the accessory pathway. Antidromic AVRT (Less common) – Wide complex tachycardia in which the wave of depolarization travels down the accessory pathway and retrograde up the AV node.

Mechanism of orthodromic AVRT

Mechanism of antidromic AVRT

What is this arrhythmia? Antidromic AVRT

Classification Scheme for Arrhythmias Abnormalities in Conduction Bradyarrhythmias Conduction Block SA node – SA block Atria - NA AV node – AV block Ventricles – NA Reentry Tachyarrhythmias SA node – SA nodal reentry Atria – Intraatrial reentrant tachycardia, a-flutter, a-fib AV node – AVNRT Ventricles – Ventricular tachycardia (common) Accessory pathways – AVRT Abnormalities in Automaticity Decreased Automaticity SA node – Sinus bradycardia Atria – NA AV node – NA Ventricles - NA Increased/Abnormal Automaticity SA node – Sinus tachycardia Atria – Ectopic atrial tachycardia AV – Junctional tachycardia Ventricles – Ventricular tachycardia (rare) Additional important arrhythmias: Multifocal atrial tachycardia, torsade de pointes