DIAGNOSIS OF CARDIAC RHYTHMS Lecture #2

I. Common Terminology Supraventricular vs. Ventricular Rhythms • The differential is made on the basis of QRS duration • If the QRS complex is narrow (< 0.12 sec): – The ventricular myocardium is depolarized rapidly – The rhythm is supraventricular in origin • If the QRS complex is wide (> 0.12 sec): – There is a delay in the spread of the electrical activation throughout the ventricles – The origin of the rhythm may be in the ventricle itself

Premature Atrial Contraction (PAC) • P-waves differ from normal • P-waves appear early • P-waves are followed by a normal-appearing QRS complex

MECHANISM PVC PAC

Premature Ventricular Contraction (PVC) • NO P-waves present • QRS complex is wide • Ventricular Tachycardia (VT)  3 consecutive PVC’s, at a rate  100 bpm (Non-sustained VT - <30 sec)

I. Common Terminology (cont’d) Arrhythmia • Generally referred to as any rhythm other than normal sinus rhythm 3 general mechanisms that can cause arrhythmias: Disorders of impulse formation: Altered Automaticity Triggered activity Disorders of impulse conduction: 3. Re-entry

Mechanism of Arrhythmias: Re-entrant Tachycardia • Rhythm is secondary to a “loop” in the electrical circuitry (the re-entry pathway) resulting in tachycardia Requires: Unidirectional block (with recovery) Slowed conduction through loop • It may occur within the SA node, the AV node, or actually any ectopic foci in the atria or ventricles

MECHANISM: Re-entry Tachycardia

II. Diagnosing Cardiac Rhythms

A. Regular Supraventricular Rhythms

1. Sinus Rhythm Normal Sinus Rhythm • Rate = 60 – 99 bpm Sinus Bradycardia • Rate  59 bpm Sinus Tachycardia • Rate  100 bpm

Sinus Rhythm Criteria: 1. Every QRS complex is preceded by a P-wave 2. P-waves appear normal, that is they are of sinus node origin: A. Normal Morphology: 1. P-wave duration < 0.12 sec (< 3 boxes) 2. P-wave height < 2.5 mm (< 2.5 boxes) B. Normal Axis: 1. P-waves is upright in leads II, III & aVF 2. P-waves is negative in lead aVR

2. Paroxysmal Atrial Tachycardia (PAT) Re-entrant tachycardia of supraventricular origin, with a rate of 120 – 180 bpm (narrow complex) P-waves may or may not be visible, depending on the rate If present, P-waves are usually regular and inverted in lead II (they may be seen before, during, or after the QRS complexes) Usually idiopathic, but can also be seen in RHD, COPD, MVP & digitalis toxicity

Paroxysmal Atrial Tachycardia

Paroxysmal Atrial Tachycardia

3. Atrial Flutter A. Atrial rate ~ 250 – 350 bpm B. Characterized by rapid, undulating“flutter-waves”: 1. Are best seen in leads aVF & V1 2. Have a longer duration & a greater amplitude than a normal P-wave 3. Have a saw-toothed appearance C. There is always some degree of AV-block present (2:1, 3:1 or variable), which is why the atrial rate is always much greater than the ventricular rate

Atrial Flutter

Atrial Flutter (cont’d) D. Carotid sinus massage – may exaggerate the degree of AV-block & consequently slow down the QRS rate, to assist with the diagnosis – This makes the flutter-waves more obvious!

4. Junctional Rhythm A. Impulses originate in the AV node with retrograde & antegrade conduction B. QRS complexes are narrow & regular (this is still considered supraventricular!) C. P-waves may be inverted in leads II, III & aVF & may occur before, during or after the QRS complexes D. Junctional Rate = 40 – 55 bpm E. This is usually an escape rhythm due to SA node dysfunction or digitalis toxicity!

Junctional Rhythm

Junctional Rhythm

AV-Nodal Re-entrant Tachycardia (AVNRT) One of the most common causes of PSVT P-waves may not be visible or may occur before, during or after the QRS complexes Two pathways usually exist: slow (anterograde conduction) & fast (retrograde conduction) D. More common in younger patients E. Abrupt onset & offset

6. AV Re-entrant Tachycardia (AVRT) Another common cause of PSVT Involves an “accessory pathway” (1:1500) Usually utilizes the AV node as the anterograde & the accessory pathway as the retrograde limbs (Orthodromic AVRT) – accessory pathway may be “concealed” In 10%, impulse travels retrograde across AVN, and anterograde over accessory pathway (Antidromic AVRT) – “pre-excitation” present

Pre-excitation Pre-excitation: Impulse travels anterogradely th’ AV node + accessory pathway to ventricles Examples include pre-excitation syndromes: – Wolff–Parkinson–White syndrome (pre-excitation + tacchycardia) – Lown-Ganong-Levine (LGL) syndrome – “Mahaim fiber tachycardias”

Wolff–Parkinson–White (WPW) A. A supraventricular rhythm originating in the SA node with normal & regular P-waves B. PR interval is abnormally short (< 0.12 sec) C. QRS is wide with a “slurred upstroke” (AKA the delta-wave) Delta-waves are due to the accessory conduction pathway (bundle of Kent) from the atria to the ventricles, that bypasses the AV node Must manifest a tacchycardia at some point in time E. Rx: Procainamide

Wolff–Parkinson–White

B. Irregular Supraventricular Rhythms

1. Sinus Arrhythmia

2. Wandering Atrial Pacemaker (WAP) A. Pacing is from various foci within the atria B. Heart rate <100 bpm C. Contour or shape of P-waves vary from beat to beat, in a single lead (always try to look at lead II!) Associated with variations of P-R & P-P intervals, resulting in an irregularly irregular rhythm E. A common cause is rheumatic heart disease So, Dx Criterion: Three consecutive P-waves with different morphologies, on a single EKG lead, with a heart rate <100 bpm

Wandering Atrial Pacemaker

Wandering Atrial Pacemaker

3. Multifocal Atrial Tachycardia (MAT) A. Multifocal Atrial Tachycardia (MAT) is similar to wandering atrial pacemaker, except that the heart rate 100 bpm Again, you must have three different consecutive P-wave morphologies on a given lead (again, examine lead II!) C. Irregularly irregular rhythm D. Usually associated with end-stage COPD E. Rx: Control the rate & treat the underlying problem

Multifocal Atrial Tachycardia

4. Atrial Fibrillation A. Random chaotic depolarizations of the atria at rates > 300 bpm B. NO effective pumping of the atria takes place – You loose ~25% of C.O., AKA the “atrial kick” C. Irregularly irregular rhythm May occur in any clinical situation which causes LAE, hyperthyroidism, or also with EtOH use (“holiday heart”) E. Rx: Rate control & anti-coagulation

Atrial Fibrillation

Atrial Fibrillation The ventricular rate can be either rapid or well-controlled, depending on the conduction through the AV node

C. Ventricular Rhythms …these are generally regular…!

1. Idioventricular Rhythms Rhythm originates in the ventricles, giving rise to wide & bizarre QRS complexes B. The AV node & sometimes the SA node are not functioning normally! D. The axis of T-waves is in the opposite direction of the QRS complexes E. Rate = 20 – 40 bpm

Idioventricular Rhythms

Idioventricular Rhythm

2. Accelerated Idioventricular Rhythm (AIVR) A. Often develops following an acute MI! B. Occurs in short bursts & lasts < 20 sec C. Rate = 40 – 120 bpm

Accelerated Idioventricular Rhythm

3. Ventricular Tachycardia (VT) Once again, you see broad & bizarre QRS complexes (> 0.12 sec) B. Often with an abrupt onset C. Rate  120 – 140 bpm D. Can be monomorphic or polymorphic (Torsades) Look for ventricular capture & fusion beats – Capture beat: a normal atrial beat “breaks through” BEFORE the ventricular beat has occurred – Fusion beat: the atrial beat “breaks through” DURING the ventricular beat

Monomorphic Ventricular Tachycardia

Polymorphic Ventricular Tachycardia (Torsades de Pointes)

Wide complex tacchycardia: SVT v/s VT QRS duration <0.14 >0.14 s/o AV dissociation (fusion, capture bts) absent may be seen Response of vagal maneuvers + - Concordance of QRS complexes in V1-V6 Axis: extreme axis deviation rare h/o CAD uncommon Usually present

4. Ventricular Fibrillation (VF) Chaotic depolarization of the ventricles Loss of organized QRS complexes Complete loss of the cardiac contractile function Circulatory arrest comes about within seconds The most common cause of sudden cardiac death

Ventricular Fibrillation

Ventricular Fibrillation

General Rule for Arrhythmia Rates Rhythm Rate (bpm) • Normal Sinus Rhythm 60 – 100 • Idioventricular “Escape” Rhythm 20 – 40 • Junctional “Escape” Rhythm 40 – 60 • Accelerated Idioventricular (AIVR) 40 – 120 • Sinus Tachycardia (ST) 100 – 150 • *SVT & Ventricular Tach. (VT) 150 – 250 • Atrial Flutter & Torsades de Pointes 250 – 350 • Atrial Fib. & Ventricular Fib. 350 – 450 * Excludes ST, atrial fibrillation & atrial flutter

D. Arrhythmias: Review!

Regular Narrow-Complex Tachycardias Sinus Tachycardia: Normal P-waves, HR usually <150 bpm Proxysmal Atrial Tachycardia (PAT): P-waves are different from sinus (may be inverted) or absent Atrial Flutter: Large “saw-toothed” flutter-waves, +/– variable AV-block AV-Nodal Re-entrant Tachycardia (AVNRT): Most common form of PSVT, +/– P-waves AV Re-entrant Tachycardia (AVRT): A common form of PSVT, +/– P-waves, + accessory pathway

Irregularly Irregular Narrow-Complex Tachycardias Atrial Fibrillation: No recognizable P-waves Multifocal Atrial Tachycardia (MAT): Three (3) consecutive P-waves with different morphologies, usually associated with COPD 3. Any “regular” SVT with variable AV-block: Examples: PAT or a. flutter with variable AV-block

Approach to EKG Interpretation ALWAYS, ALWAYS, ALWAYS: 1. Rate 2. Rhythm (includes analysis of intervals) 3. Axis 4. Hypertrophy 5. Ischemia, Injury, or Infarct

Atrial (non-sinus) Rhythm

Multifocal Atrial Tachycardia

Atrial Flutter with 2:1 Conduction

Sinus Rhythm with Unifocal PVC’s

Atrial Fibrillation with a Slow Ventricular Response

Sinus Rhythm with Bigeminal PVC’s

Atrial Fibrillation with RVR

Thank you for your attention! The End Thank you for your attention! Questions?