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DIAGNOSIS OF CARDIAC RHYTHMS

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): – T he ventricular myocardium is depolarized rapidly

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DIAGNOSIS OF CARDIAC RHYTHMS

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  1. DIAGNOSIS OFCARDIAC RHYTHMS Lecture #2

  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

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

  4. MECHANISMPVC PAC

  5. 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)

  6. 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

  7. 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

  8. MECHANISM:Re-entryTachycardia

  9. II. Diagnosing Cardiac Rhythms

  10. A. Regular Supraventricular Rhythms

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

  12. Sinus Rhythm Criteria: 1. Every QRS complex is precededby a P-wave 2. P-waves appear normal, that is they are ofsinus 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 leadaVR

  13. 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

  14. Paroxysmal Atrial Tachycardia

  15. Paroxysmal Atrial Tachycardia

  16. 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

  17. Atrial Flutter

  18. 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!

  19. 4. Junctional Rhythm A. Impulses originate in theAV 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, duringorafter the QRS complexes D. Junctional Rate = 40 – 55 bpm E. This is usually an escape rhythm due to SA node dysfunction ordigitalis toxicity!

  20. Junctional Rhythm

  21. Junctional Rhythm

  22. 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

  23. 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

  24. 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”

  25. 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 thedelta-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

  26. Wolff–Parkinson–White

  27. B. Irregular Supraventricular Rhythms

  28. 1. Sinus Arrhythmia

  29. 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

  30. Wandering Atrial Pacemaker

  31. Wandering Atrial Pacemaker

  32. 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

  33. Multifocal Atrial Tachycardia

  34. 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

  35. Atrial Fibrillation

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

  37. C. Ventricular Rhythms…these are generally regular…!

  38. 1. Idioventricular Rhythms • Rhythm originates in the ventricles, giving rise to wide& bizarreQRS 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

  39. Idioventricular Rhythms

  40. Idioventricular Rhythm

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

  42. Accelerated Idioventricular Rhythm

  43. 3. VentricularTachycardia (VT) • Once again, you see broad& bizarreQRS complexes (> 0.12 sec) B. Often with an abrupt onset C. Rate 120 – 140 bpm D. Can be monomorphicorpolymorphic(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

  44. Monomorphic Ventricular Tachycardia

  45. Polymorphic Ventricular Tachycardia(Torsades de Pointes)

  46. Wide complex tacchycardia: SVT v/s VT

  47. 4. VentricularFibrillation (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

  48. Ventricular Fibrillation

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