(living in the fast lane)

Transcription

1 (living in the fast lane) Presented by M.D. Cardiology

2 IT S 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

3 Re-entrant Vs Automatic Tachycardias RE-ENTRANT V. regular Abrupt onset/cessation Easily initiated Easily terminated Responsive to drugs AUTOMATIC Wide variation Warm-up, cooldown Not so Not so Atypical responses

4 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 pathways.

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

6 What is the fastest Bird on earth? Hunter Speed Record of 322 km/h.

7 Accessory pathway syndromes Accessory Pathways WPW Manifest AP Concealed AP PJRT Mahaim WPW - ORT WPW - ART URAP

8 Understanding the variations in Pathway electrophysiology the key to understanding variations in presentations and management issues Number, Location, Direction of Propagation & Propagation velocities Propagation Direction Propagation Velocity Antegrade Retrograde Unidirectional Bidirectional Non- Decremental Decremental

9 Antidromic WPW

10 ORT - URAP

11 PJRT

12 Mahaim

13 What is the Fastest Fish in oceans? Weighing 90 k gm Length 3 m Speed 113 km/h Fastest known submarine is the K-222 top speed 82 km/h

14 WPW Syndrome

15 1930 : Wolf, Parkinson & White described a syndrome that consisted of Short PR-interval (<0.12 sec) Bundle branch block on surface QRS Paroxysmal tachycardia 1932: Wolferth and Wood hypothesized Extra-nodal AV connections to be the basis for this syndrome 1969: Sealy et al surgically confirmed. Characteristic appearance on surface ECG during Sinus Rhythm: Short PR interval Slurred initial QRS ( Delta wave ) resulting in broadening of the QRS complex, without widening the duration from beginning of P to end of QRS

16 WPW Syndrome The most common cardiac pre-excitation syndrome. Overall incidence in a population study of Olmstead County, Minnesota : 3.96/100,000 persons/year. (*Munger et al. Circ 1993) Exact cause unknown. Most cases sporadic. Bimodal age distribution 1 st year, then young adulthood. 3% of patients have an affected 1 st -deg relative. Familial occurrence reported autosomal dominant inheritance. Recent report Chr 7q3 in a family with WPW / HCM / HB. Tuberin and Hamartin gene mutations in WPW + Tuberous Sclerosis Myo Binding Prot / cardiac troponin gene mutations in WPW + HCM Prevalence of WPW In general population % In patients with CHD %

17 Generally, AV conduction through the accessory pathway is faster than through the AV Node. Thus, some part of the ventricle is pre-excited by this eccentric spread of activation Surface ECG in Sinus Rhythm depends upon the balance between ventricular depolarization occuring through the AV node vs the Accessory Pathway Greater the contribution of the Accessory Pathway to ventricular depolarization, smaller the PR interval, more prominent the Delta Wave

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19 Electrophysiological characteristics Short or negative H-V interval on His-Bundle electrogram Atrial pacing enhances preexcitation AV block results in maximum preexcitation Faster AV conduction ( Exercise / Isoproterenol) decreases the preexcitation Pre-excitation is lost when RR interval shortens below the AP effective refractory period (ERP)

20 In WPW Syndrome, Accessory Pathways are usually capable of conducting in both directions Usually the APs are Non-decremental in nature Can potentially result in several different types of tachycardias Orthodromic reciprocating tachycardia (ORT) with retrograde AP conduction is the commonest ORT is also commonly seen in patients without manifest pre-excitation Concealed Pathways Antidromic tachycardia (ART) is seen as well, but seldom in isolation without ORT

21 Per se, WPW refers to patients with pre-excitation in ECG + symptomatic episodes of tachycardia Manifest Pathways Asymptomatic patients with pre-excitation pattern are simply described as having VPE pattern Patients with Accessory Pathways, but no preexcitation are described as having Concealed Pathways. Pathways may become manifest during episodes of tachycardia

22 What is the fastest flying insect? 225 different species. Top speed 65km/h

23 WPW - ORT

24 WPW - ORT

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27 Symptoms ORT occurs paroxysmally with or without exercise Manifest as self-limited episodic palpitations with shortness of breath, fatigue or dizziness Syncope is uncommon but worrisome Usually well tolerated Can cause ventricular dysfunction / hemodynamic collapse if undetected for hours / days, especially in infants Faster rates (>250 BPM) and poorer condition at presentation are seen in younger children Severe symptoms occur in only about 1% older children and adult patients ECG Features: Narrow BPM in adults and higher rates in children. Tachycardia rate largely determined by AV nodal conduction Rate-related BBB may occur especially at initiation of tachycardia ; can help in localization of the Accessory Pathway as left / right Retrograde P s usually occur during T-wave

28 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

29 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

30 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% } 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

31 What is the fastest mammal on earth? Top speed 120 km/h Accelerate from 0 to top speed in 3 seconds. Maintain speed for 10 seconds. Rests for 30 minutes after.

32 WPW - ART

33 Antidromic WPW

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35 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

36 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 activation occurs with the same VA interval and same retrograde atrial activation In general, the VA interval is shorter in AVNRT

37 Immediate management of SVT with WPW Syndrome

38 WPW ORT or ART Hemodynamically stable Hemodynamically unstable Vagal Maneuvers Anti-arrhythmics Electrophysiological maneuvers Emergency DC Version Ice pack over face ADENOSINE Esophagial pacing Valsalva Carotid massage Beta Blocker Verapamil / Digoxin Elective DC Version Verapamil consistently effective but contraindicated in infants Both Dig & Verapamil ABSOLUTELY contraindicated in WPW with Atrial fibrillation or flutter

39 Digoxin and Verapamil can decrease the ERP of the AP and thereby increase the rate of conduction of Atrial impulses to the Ventricles Infants have under-developed Sarcoplasmic Reticulum and may have severe hemodynamic collapse resulting from blocking off of the trans-membrane Ca2+ channels by Verapamil

40 WPW with Pre-excited Atrial Fibrillation / Flutter

41 Risk of sudden death from rapid Ventricular response to Atrial Fibrillation

42 Pre-excited Atrial Fibrillation or Flutter in WPW It is the presenting symptom in 25% of older patients with WPW Risk of atrial fibrillation in adults with WPW 10% to 38% Spontaneous Atrial fibrillation is rare in children with WPW and even rarer in infants Can potentially result in rapid ventricular activation, even ventricular fibrillation, depending upon conduction times and ERPs of the AVN and the AP

43 Why does Atrial Fibrillation occur? Atrial pre-excitation sec to rapid AVRT Primary Atrial activity

44 Why does the ventricular rhythm degenerate during Atrial Fibrillation? Multiple APs Shortened AP ERP due to sympathetic discharge of the initial tachycardia Disorganized and extremely irregular Ventricular rhythm Activation via one AP During recovery from activation via the other pathway

45 PRIMARY ATRIAL ACTIVITY AS A CAUSE FOR ATRIAL FIBRILLATION IN WPW Jais et al (Circulation 1997) suggested rapidly firing focal atrial activity as the trigger for Atrial fibrillation in a subset of young patients without structural heart disease Basso et al in Circulation Jan 2001 reported the presence of histopathological evidence of focal atrial myocarditis in 4 of 8 (50%) patients with WPW Syndrome out of a total series of 273 children and young adults (<35 years) who had Sudden Cardiac Death Lymphocytic infiltrates in 75% Polymorphous infiltrates in 25%

46 Arrhthmogenic Atrial Myocraditis

47 Why does the ventricular rhythm degenerate during Atrial Fibrillation? Atrial fibrillation Ventricular fibrillation SCD

48 ECG features EP Risk Factors Irregularly irregular rhythm in Atrial fibrillation, strictly regular in flutter Variable fusion between AVN and AP conduction resulting in varying QRS morphologies Presence of two distinct QRS patterns suggests multiple APs Inducible atrial fibrillation H/o ventricular fibrillation RR interval < 250ms and antegrade AP ERP < 340ms In children, atrial fibrillation may be difficult to induce, so response of APs to rapid atrial pacing may suffice

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50 Management Goals Hemodynamics Reduce Ventricular Response rate Terminate Atrial Fibrillation Unstable Synchronized DC- Version Relatively stable Procainamide

51 Long-term management Definitive RFA Palliation Medical Goals Prevent recurrence Reduce Vent Rate If AF recurs Medical Palliation Oral Procainamide Beta Blockade Other Class IA, IC or III drugs

52 What is the fastest reptile on earth? Top speed of 35 km/h.

53 ORT without Pre-excitation URAP (Concealed AP)

54 ORT with Preexcitation ORT without Preexcitation ORT does NOT depend upon the ability of an AP to conduct antegrade When ORT occurs without ventricular pre-excitation, it is said to be through concealed or unidirectional retrograde AP (URAP) Comprises nearly 60% of ORTs Clinical, ECG and EP manifestations identical to ORT with WPW, except for sinus rhythm ECG Lacks the risk of SCD in response to atrial fibrillation

55 ORT - URAP

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57 MANAGEMENT Acute management same as for ORT However : AP cannot conduct antegrade Lack of risk from SCD consequent to AF Verapamil and Digoxin are not contraindicated If not very symptomatic, medical management may be preferred Periodic vagal maneuvers Digoxin / Beta blockers / Verapamil Class IA, IC, or III agents Severe or frequent symptoms RFA is still first-line treatment

58 Persistent Junctional Reciprocating Tachycardia (PJRT)

59 PJRT 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

60 PJRT

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62 PJRT Multiple APs are common Results in an incessant tachycardia with relatively slow rates ( 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 but also in the concealed pathway. 50% of patients present with fatigue or even CHF Palpitations and syncope are unusual and occur in older patients May lead on to LV dysfunction

63 PJRT EP Features 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 PJRT Incessant Paroxysmal

64 Incessant Paroxysmal Tachy cycle length just > cycle length at which 1:1 VA conduction occurs across AP Shorter tachycardia cycle length Both pathways excitable with each cycle Faster VA conduction

65 Distinguishing PJRT from EAT and Atypical AVNRT Relatively late VPC introduced during tachycardia at a time when the His Bundle is known to be refractory will block retrogradely in the AP & reproducibly terminate the tachycardia, without reaching the atrium Not only does this exclude atrial tachycardia as a mechanism, but if the anterograde His-Bundle potential is not there and therefore refractory, the VPC could not have reached AV node. The possibility of AVNRT is ruled out. As in more typical forms of AVRT, the ability to preexcite the atria with single VPC during tachycardia at a time when the His is refractory proves that an accessory connection is present.

66 Management Emergency therapy is rarely necessary Maneuvers as for ORT more often turn-out to be only diagnostic rather than therapeutic Therefore.. Manage with Long-acting drugs RFA

67 What is the fastest particle in the proposed in 1967 by Gerald Feinberg Slowest speed for this particle is the speed of light. When it losses energy it become faster. universe?

68 Mahaim Pathways

69 Mahaim Tachycardia Mahaim fibres are long, insulated Atrioventricular connections running between the lateral right atrium and the anterior wall of the RV Most are atriofascicular rather than nodoventricular Decremental conduction usually antegrade only Sinus rhythm ECG shows intermittent delta wave, with a normal PR interval Can support an ART using Mahaim fibres as the antegrade limb and AVN as the retrograde limb, resulting in a wide QRS tachycardia

70 Mahaim

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72 Localization of Accessory Pathways Fitzpatrick et al, JACC 1994 Apr; 23(5):1272

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74 EPS & RFA One last word!!

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