Circuits in avrt,avnrt i.tammi raju

1. GRAPHICS Circuits in AVNRT,AVRT Dr.I.Tammi Raju

2. Circuits in AVNRT,AVRT VPC’S in AVRT,AVNRT BBB IN AVRT

3. AV NODE ANATOMY The normal AV junctional area can be divided into distinct regions: The transitional cell zone, also called nodal approaches; The compact portion, or the AV node itself; and The penetrating part of the AV bundle (His bundle), which continues as a nonbranching portion

4. TRANSITIONAL CELL ZONE . The transitional cells or nodal approaches are located in posterior, superficial, and deep groups of cells. They differ histologically from atrial myocardium and connect the latter with the compact portion of the AV node. Some fibers may pass from the posterior internodal tract to the distal portion of the AV node or His bundle and provide the anatomical substrate for conduction to bypass AV nodal slowing.

5. The compact portion of the AV node Is a superficial structure lying just beneath the RA endocardium, anterior to the ostium of the coronary sinus, and directly above the insertion of the septal leaflet of the TV. It is at the apex of a triangle formed by the tricuspid annulus and the tendon of Todaro , which originates in the central fibrous body. The term triangle of Koch, however, has to be used with caution because in normal adult hearts the tendon of Todaro , is absent in about two thirds of hearts

6. Bundle of His (Penetrating Portion of the Atrioventricular Bundle) Connects with the distal part of the compact AV node, perforates the central fibrous body, and continues through the annulus fibrosis, where it is called the nonbranching portion). Proximal cells of the penetrating portion are heterogeneous and resemble those of the compact AV node; distal cells are similar to cells in the proximal bundle branches. Branches from the anterior and posterior descending coronary arteries supply the upper muscular interventricular septum with blood, which makes the conduction system at this site more impervious to ischemic damage unless the ischemia is extensive

7. ARTERIAL SUPPLY In 85 to 90 percent of human hearts, the arterial supply to the AV node is a branch from the RCA A branch of the LCX provides the AV nodal artery in the remaining hearts. Fibers in the lower part of the AV node may exhibit automatic impulse formation. The main function of the AV node is modulation of atrial impulse transmission to the ventricles, there by coordinating atrial and ventricular contractions

8. AVNRT

9. AVNRT INTRODUCTION Most common of the PSVTs, accounting for nearly two-thirds of cases. synonyms   AV junctional reentrant tachycardia. Reciprocal or reciprocating AV nodal reentrant tachycardia. Junctional reciprocating tachycardia .

10. Commonest cause of palpitations in patients with structurally normal hearts. AVNRT is typically paroxysmal and may occur spontaneously or provocation). It is more common in women than men (~ 75% of cases occurring in women) complain of the sudden onset of rapid, regular palpitations, presyncope . angina. The patient may complain of shortness of breath, anxiety and occasionally polyuria . The tachycardia typically ranges between 140-280 bpm and is regular in nature.  It may cease spontaneously (and abruptly) or continue indefinitely until medical treatment is sought. The condition is generally well tolerated and is rarely life threatening in patients with pre-existing heart disease. AVNRT

11. No apparent precipitating cause . However, in some patients, nicotine, alcohol, stimulants, exercise, or surges in vagal tone can initiate episodes. Familial AVNRT has been reported

12. The old model of the re-entrant circuit comprised two anatomically distinct limbs confined to the AV node can provide explanations for many aspects of the electrophysiological behaviour of these tachycardias. However, these pathways have not been demonstrated histologically and, despite several attempts to provide a reasonable model based on anatomic or functional characteristics, the exact circuit responsible for the re-entrant tachycardia is unknown

13. There is no unanimously accepted scheme for the diagnosis and classification of various AVNRT forms. Recognition of the various types of AVNRT, however, is of clinical importance because an anatomically guided catheter ablation technique may eradicate arrhythmia. In addition, some forms of AVNRT are associated with an increased risk of catheter ablation-induced AV block and special care is needed to avoid such a complication

14. SYMPTOMS Palpitations Dizziness Dyspnea Chest pain Fatigue Syncope polyuria   

15. The  slow pathway  ( alpha ):  a slowly-conducting pathway with a short refractory period. The  fast pathway  ( beta ):  a rapidly-conducting pathway with a long refractory period. AVNRT

16. AV NODAL REENTRANT TACHYCARDIA

17. Retrograde atrial activation sequence AVNRT has been traditionally classified as slow–fast or typical AVNRT, and fast–slow or atypical AVNRT, The fast pathway of the re-entry circuit runs superiorly and anteriorly in the triangle of Koch, whereas the slow pathway runs inferiorly and posteriorly close to the coronary sinus ostium.

18. ELECTROPHYSIOLOGIC FEATURES   Dual AV nodal physiology may be distinct anatomic structures, or may be functionally separate  fast or beta pathway : conducts rapidly and has a relatively long refractory period. slow or alpha pathway : conducts relatively slowly and has a shorter refractory period . The origins of the fast and slow pathways are probably in perinodal atrial tissue. These pathways join and enter a final common pathway in the AV node. While atrial tissue above the AV node appears to be part of the reentrant circuit, the bundle of His below the node is probably  not  a necessary part of the circuit.

19. Dual atrioventricular nodal conduction Denes et al. in 1973, Antegrade dual pathways are demonstrable in 75% of patients. Conversely, antegrade dual pathways can be demonstrated without tachycardia A concealed atriohisian tract that bypasses the AV node may constitute the retrograde fast pathway in up to a third of all apparently "typical" AVNRT cases.

20. Koch's triangle and environment

21. Schematic representation of Koch's triangle which is bounded by the tricuspid ring and the tendon of Todoro . The tendon of Todoro and the tricuspid ring are in close proximity forming the apex of the triangle near the His bundle at the membranous septum . Koch's triangle can be divided into thirds : the anterior contains the compact AV node; the posterior contains the coronary sinus; and the middle or mid- septal third is between the anterior and posterior portions. The anterior third is associated with fast pathways, and the middle and posterior thirds with slow pathways.

22. Retrograde atrial activation sequence AVNRT has been traditionally classified as slow–fast or typical AVNRT, and fast–slow or atypical AVNRT, according to the conventional description of dual AV junctional pathways. The fast pathway of the re-entry circuit runs superiorly and anteriorly in the triangle of Koch, Slow pathway runs inferiorly and posteriorly close to the coronary sinus ostium

23. Indeed, in the majority of slow–fast cases of AVNRT, the site of the earliest atrial activation is close to the apex of Koch’s triangle, near the AV node-His bundle junction, i.e. anterior to the AV node. In the fast–slow form, the site of the earliest atrial activation is usually recorded posterior to the AV node near the orifice of the coronary sinus

24. Posterior (or type B) variety of presumed slow–fast AVNRT, with long ventriculoatrial (VA) intervals and the earliest retrograde atrial activation near the coronary sinus ostium. Posterior fast pathways have been reported in up to 6% of patients with AVNRT and require special attention for the avoidance of AV block when delivering radiofrequency energy at the anatomical site of the slow pathway

25. VA conduction time Traditionally, a VA interval measured from the onset of ventricular activation on surface ECG to the earliest deflection of the atrial activation in the His bundle electrogram VA< 60 ms, or a VA interval measured at the high right atrium < 95 ms, has been considered as diagnostic for the slow–fast form of AVNRT.

26. Conduction times are sensitive to autonomic changes and isoprenaline administration that is often used during diagnostic studies. However, a septal VA interval <70 ms is highly suggestive of slow–fast AVNRT

27. TYPES Typical AVNRT Slow–fast In the slow–fast form of AVNRT, the onset of atrial activation appears early, at the onset or just after the QRS complex Maintaining an atrial -His/His- atrial ratio AH/HA.> 1. AH/HA ratio > 3, and a VA interval measured from the onset of ventricular activation on surface ECG to the earliest deflection of the atrial activation in the His bundle electrogram <60 ms, or VA interval measured at the high right atrium< 95 ms are diagnostic of the slow–fast AVNRT type.

28. Slow-Fast AVNRT (common type ) P waves are buried in the QRS complexes –simultaneous activation of atria and ventricles – most common presentation of AVNRT –66%. If not synchronous –pseudo s wave in inferior leads ,pseudo r’ wave in lead V1---30% cases .

29. REGULAR SVT NARROW QRS TACHYCARDIA

30. REGULAR SVT

31. Slow-Fast (Typical) AVNRT: Narrow complex tachycardia at ~ 150 bpm . No visible P waves. There are pseudo R’ waves in V1-2. NARROW QRS TACHYCARDIA

32. Atypical AVNRT Fast–slow . In the fast–slow form of AVNRT (5–10% of all AVNRT cases), retrograde atrial electrograms begin well after ventricular activation with an AH/HA ratio <1, indicating that retrograde conduction is slower than antegrade conduction The VA interval is > 60 ms, and in the high right atrium > 100 ms. In the majority of fast–slow cases, the site of the earliest atrial activation is posterior to the AV node near the orifice of the coronary sinus

33. Accounts for 10% of AVNRT Associated with Fast AV nodal pathway for anterograde conduction and Slow AV nodal pathway for retrograde conduction. Due to the relatively long ventriculo-atrial interval, the retrograde P wave is more likely to be visible after the corresponding QRS. Fast-Slow AVNRT (Uncommon AVNRT) REGULAR SVT

34. NARROW QRS TACHYCARDIA

35. NARROW QRS TACHYCARDIA

36. Slow–slow 1-5% AVNRT Associated with Slow AV nodal pathway for anterograde conduction and Slow left atrial fibres as the pathway for retrograde conduction. In the slow–slow form, the AH/HA ratio is >1 but the VA interval is >60 ms, suggesting that two slow pathways are utilized for both anterograde and retrograde activations. Usually, but not always, the earliest atrial activation is at the posterior septum (coronary sinus ostium ).

37. Slow-Slow AVNRT (Atypical AVNRT) ECG features: Tachycardia with a P-wave seen in mid-diastole… effectively appearing “before” the QRS complex. Confusing as a P wave appearing before the QRS complex in the face of a tachycardia might be read as a sinus tachycardia.

38. AVNRT - ECG Presence of a narrow complex tachycardia with regular R-R intervals and no visible p waves. P waves are retrograde and are inverted in leads II,III,AVF. P waves are buried in the QRS complexes –simultaneous activation of atria and ventricles – most common presentation of AVNRT –66%. If not synchronous –pseudo s wave in inferior leads ,pseudo r’ wave in lead V1---30% cases .

39. Management Of AVNRT May respond to vagal maneuvers with reversion to sinus rhythm. The mainstay of treatment is  adenosine . Other agents which may be used include calcium-channel blockers, beta-blockers and amiodarone . DC cardioversion is rarely required. Catheter ablation may be considered in recurrent episodes not amenable to medical treatment.

40. NARROW QRS TACHYCARDIA AVNRT (the Jaeggi algorithm), Pseudo S/R waves, RP interval, Lack of significant ST depression in multiple leads A correct diagnosis of typical AVNRT can be made by ECG analysis 76% of the time

41. NARROW QRS TACHYCARDIA

42. NARROW QRS TACHYCARDIA

43. Summary of AVNRT subtypes

44. What are “Pre-excitation syndromes” ? Term coined by Ohnell First described in 1930 by Louis Wolff, John  Parkinson  and Paul Dudley White. A group of ECG and Electrophysiological abnormalities in which The atrial impulses are conducted partly or completely, PREMATURELY, to the ventricles via a mechanism other than the normal AV-node Associated with a wide array of tachycardias with both normal QRS and prolonged QRS durations

45. Origin of the Accessory pathways ? In early stages of cardiac development, there is direct physical and electrical contact between the atrial and ventricular myocardium ….disrupted by subsequent in-growth of the AV sulcus tissue and formation of the annulus fibrosus Defects in this annulus results in accessory pathhways

46. Most of these connections are of ventricular myocardial origin, rather than of atrial tissue origin May be found anywhere across the tricuspid or mitral valve annulus – whether endocardial or epicardial Most common pathways in are Left Free Wall followed by Posteroseptal and Right Free Wall ; Midseptal and Anteroseptal are least common * *Calkin et al, Circulation 1999

47. Atrioventricular Reentry Tachycardias .AVRT AVRT is a form of paroxysmal supraventricular tachycardia. A reentry circuit is formed by the normal conduction system and the accessory pathway resulting in circus movement. During tachyarrythmias the features of pre-excitation are lost as the accessory pathway forms part of the reentry circuit. AVRT often triggered by premature atrial or premature ventricular beats .

48. Bundle of KentThe classic accessory pathway is the AV bypass tract or in WPW that directly connects atrial and ventricular myocardium, bypassing the AVnode /His-Purkinje system James fibers , atrionodal tracts , connect atrium to distal or compact AV node ( " Lown - Ganong -Levine syndrome and enhanced atrioventricular nodal conduction") Brechenmacher fibers ( atrio-Hisian tracts) connect the atrium to His bundle Mahaim fibers - Hisian -fascicular tracts , connect the atrium ( atriofascicular pathways), AV node ( nodofascicular pathways) or His bundle ( fasciculoventricular ) to distal Purkinje fibers or ventricular myocardium.

49. Transverse plane  — In the transverse plane, bypass tracts can cross the AV groove anywhere except between the left and right fibrous trigones where the atrial myocardium is not in direct juxtaposition with ventricular myocardium. The remainder of the transverse plane can then be divided into quadrants consisting of the left free wall, posteroseptal , right free wall, and anteroseptal spaces . The distribution of accessory pathways within these regions is not homogeneous . 46 to 60 percent of accessory pathways are found within the left free wall space 25 percent are within the posteroseptal space 13 to 21 percent of pathways are within the right free wall space 2 percent are within the anteroseptal space

50. Understanding the variations in “Pathway – electrophysiology – Direction of Propagation & Propagation velocities

51. ORT - URAP

52. “Manifest Pathways” Per se, WPW refers to patients with pre-excitation in ECG + symptomatic episodes of tachycardia – “VPE pattern”- Asymptomatic patients with pre-excitation pattern are simply. “Concealed Pathways” - Patients with Accessory Pathways, but no pre-excitation . Pathways may become manifest during episodes of tachycardia

53. PR interval <120ms Delta wave  – slurring slow rise of initial portion of the QRS QRS prolongation >110ms ST Segment and T wave discordant changes – i.e. in the opposite direction to the major component of the QRS complex Pseudo-infarction pattern can be seen in up to 70% of patients – due to negatively deflected delta waves in the inferior / anterior leads (“pseudo-Q waves”), or as a prominent R wave in V1-3 (mimicking posterior infarction). WPW in sinus rhythm

54. AVRT With Orthodromic Conduction In orthodromic AVRT antegrade conduction occurs via the AV node with retrograde conduction occurring via the accessory pathway. This can occur in patients with a concealed pathway.

55. WPW - ORT

56. Orthodromic AVRT using a rapidly conducting accessory pathway: Most common type of AVRT Initiated by either an APB or VPB AV conduction is over the AV node & VA conduction over accessory pathway Activation of ventricle & atrium follow sequentially  P waves are separated from the QRS complex. Retrograde conduction is rapid  P wave closer to the preceding QRS  RP < PR. The QRS may be narrow or if aberrant conduction occurs, a typical BBB will be present.

57. Electrophysiological Study for confirmation of ORT Premature ventricular beat placed when the His Bundle is refractory results in blocking-off of the Accessory Pathway resulting in termination of the tachycardia without atrial activation Ventriculo-Atrial (VA) interval is prolonged by introduction of a premature VPB when the His is refractoy Retrograde atrial activation pattern demonstrating eccentric atrial conduction, identically matching that during ventricular pacing BBB during tachycardia results in persistent lengthening of the tachycardia cycle-length VA prolongation occurs with BBB aberration when AP is ipsilateral to the BBB

58. Initiation of Tachycardia Critically timed Atrial premature stimulus that blocks anterograde in the Accessory connection, and encounters an appropriate delay in AV Node conduction so that AP and Atria are excitable when the re-entrant wave-front reaches them That is, at an interval < ERP of the AP Isoproterenol Other intiating events : High catecholamine states, exercise, sinus acceleration, junctional beats (conducting antegrade only in AVN) , VPBs ( conducting retrograde, only in the AP)

59. Termination of tachycardia Spontaneous OR drug-induced block in either the AVN OR AP OR placement of a critically timed APC that encounters AVN or AP when they are refractory Spontaneous termination occurs more frequently with AVN due to increases in the vagal tone When the last beat of the tachycardia is manifest as an atrial stimulus without the following ventricular stimulus = Termination in the AVN When the last beat of the tachycardia is manifest as a ventricular stimulus without the following atrial stimulus = Termination in the AP

60. Electrophysiological features for differentiating ORT from AVNRT Atrial recording ( INTRACARDIAC or ESOPHAGEAL ) ORT : VA interval > 95 milliseconds ( intracardiac recording) or > 70 milliseconds ( esophageal recording) in ORT Typical AVNRT : VA interval < 70 milliseconds by either method { Positive predictive value 94% ; Negative predictive value 100% ; Sensitivity 100% ; Specificity 92% }

61. Electrophysiological features for differentiating ORT from AVNRT ORT via ‘ Septal pathways’ Vs AVNRT - Para- Hissian pacing Comparison of the VA intervals with high-output & low-output pacing { Hight output captures both His and the ventricle ; low output only captures the ventricle } Unchanged VA makes Septal pathway more likely Premature VPB when His is refractory confirms presence of Acc Pathway

62. AVRT With Antidromic Conduction In antidromic AVRT antegrade conduction occurs via the accessory pathway with retrograde conduction via the AV node.  Much less common than orthodromic AVRT occuring in ~5% of patients with WPW. ECG features of AVRT with antidromic conduction are: Rate usually 200 – 300 bpm . Wide QRS complexes due to abnormal ventricular depolarisation via accessory pathway.

63. Antidromic WPW

64. Requirements for occurrence of ART AVN anterograde conduction be blocked, while it continues in the AP , i.e. Anterograde ERP of AP < ERP of AVN Requirements for maintenance of ART Retrograde RP of AVN < tachycardia cycle length Infrequency of both of these occurring makes it an infrequent tachyarrhythmia

65. Electrophysiological features for differentiating ART from other Wide-QRS tachycardias Regularity of ART rules out Pre-excited atrial fibrillation Termination of tachycardia with a VPB that does not depolarize the atria or His rules-out Pre-excited atrial flutter and EAT Ventricular Tachycardia ruled out by An Atrial premature beat that terminates the tachycardia without conducting to the ventricle APB can advance the tachycardia cycle-length with the SAME QRS pattern AVNRT with antegrade conduction down a ‘bystander’ AP ruled out by APB that advances the tachycardia, but next atrial actrivation occurs with the same VA interval and same retrograde atrial activation In general, the VA interval is shorter in AVNRT

66. ANTIDROMIC AVRT-REGULAR BROAD COMPLEX TACHYCARDIA

67. Other Pre-Excitation Syndromes / Accessory Pathways Lown - Ganong -Levine (LGL) Syndrome Proposed pre-excitation syndrome Accessory pathway composed of  James fibres ECG features: PR interval <120ms Normal QRS morphology The term should not be used in the absence of paroxysmal tachycardia Existence is disputed and may not exist

68. Lown - Ganong -Levine Syndrome

69. Mahaim -Type Pre-excitation Right sided accessory pathways connecting either AV node to ventricles, fascicles to ventricles, or atria to fascicles proximal AV nodal-like electrophysiologic properties and distal bundle branch-like properties Accessory pathway with features similar to normal atrioventricular nodal tissue Would account for the decremental properties seen in Mahaim fibers ECG features: Sinus rhythm ECG may be normal May result in variation in ventricular morphology Reentry tachycardia typically has  LBBB  morphology

70. Mahaim

71. Tachycardia with a left bundle branch block patternQRS axis between 0 and -75º QRS duration of 0.15 seconds or less R-wave in lead 1 rS complex in lead V1 Precordial transition in lead V4 or later Cycle length between 220 and 450 milliseconds (heart rates of 130 to 270

72. 1 – 6% of SVTs in childhood Rarely presents past early adolescence 80% present in childhood ; 50% within the first year of life In the past, thought to be ‘fast-slow’ form of AVNRT. Actually an ORT via an AP with decremental conduction Usually, the QRS morphology is normal, both in sinus rhythm AND during tachycardia Rarely, MAY be associated with antegrade conduction and Pre-excitation in sinus rhythm PJRT

73. PJRT

74. PJRT Multiple APs are common Unlike what was previously thought, APs may be located anywhere along the AV groove Results in an incessant tachycardia with relatively slow rates (150 – 250 BPM) During the first several years, the rate tends to slow down as a function of delay in conduction not only in the AV node AND in the concealed pathway. 50% of patients present with fatigue or even CCF Palpitations and syncope are unusual and occur in older patients May lead on to LV dysfunction

75. AV node – like response to autonomic stimuli Long VA interval ( > 150 ms ) Tachycardia cycle length depends upon conduction times in the AVN and the AP Major contribution (nearly 64%) to the increase in cycle lengths with age is due to the decremental retrograde conduction across the AP Can be initiated / terminated with critically timed APB / VPB