6Idiopathic Ventricular Tachycardia In 10% of patients with VTYoung (20-50 years, range, 6 to 80 years)Palpitation, dizziness, presyncope or syncope (rare)Sudden cardiac death is rareExcellent prognosisCan be a cause of tachycardia-mediated cardiomyopathyCertain anatomic locations with manifest specific ECG patterns which help identify their site of origin.
11Mechanism of tachyarrhythmia Automaticity1. focal origin2. may become incessant during isoproterenol3. cannot be initiated or terminated by programmed electricalstimulation4. sometimes suppressed by calcium or β blockers5. adenosine transiently suppresses but does not terminate it.Triggered activity2. EAD or DAD ([Ca2+]i overload due to HR↑, β adrenergic effect(cAMP↑) or digoxin)3. Induced by burst pacing, isoproterenol infusion or atropineRVOT VT: DAD, adensine sensitive
12Mechanism of tachyarrhythmia Reentry1. a large circuit (macroreentry) or focal (microreentry)2. slow conduction zone: small diastolic potential3. can be initiated and terminated by programmedelectrical stimulation4. can be entrained from multiple sitesIdiopathic left VT: macroreentry, verapamil sensitive
13Classification of idiopathic VT relative to the mechanism Adenosine-sensitive VT (triggered activity)Propranolol-sensitive VT (automaticity)Verapamil-sensitive VT (reentry)
14Classification of idiopathic VT relative to the location Outflow tract ventricular tachycardia (OTVT)1. RVOT VT (90%)above pulmonary valves rarely2. LVOT VT (10%): above/below AVs, mitral annulusIdiopathic left ventricular tachycardia (ILVT)1. Left posterior fascicular VT (most common)2. Left anterior fascicular VT (rare)3. Upper septal fascicular VT (rare)Others…….Purkinje fibers, epicardium…..
15RVOT VT Nonsustained, repetitive, monomorphic VT. # Most common form (60-90%)# Characterised by frequent VPCs, couplets and salvos of nonsustained ventricular tachycardia (NSVT)# LBBB morphology and inferior QRS axis.# Occurs at rest or following a period of exercise# Transiently suppressed by sinus tachycardia. They maydiminish with exercise during stress testing.Paroxysmal, exercise-induced sustained VT.# This VT may be initiated during exercise or recovery.# Exercise stress testing is frequently uses to initiate and evaluateRVOT VT, but is not clinically helpful in most cases.
23Signal transduction schema for initiation and termination of cAMP-mediated DAD (triggered activity) AdenosinecAMP↓DAD↓
24Outflow tract ventricular tachycardia 90% of outflow tract VT comes from the RVOT- may above the pulmonary valves (rare)10% may arise from LVOT- superior basal region of LV septum, free wall- aortic sinuses of Valsava- aortic cusps- the aorto-mitral continiuty- mitral annulus- His bundle areaEpicardium
25Management of OTVTAcute termination: vagal maneuver or adenosine (6 mg until 24 mg), IV verapamil (10 mg given over 1 min. These drugs may suppress triggered rhythms; electrical cardioversion.Long term treatment options# Medical therapy: β-blockers, verapamil, diltiazem(efficacy: 20 to 50%); Alternatively class IA, IC and IIIagents.# Radiofrecuency ablation has cure rates of 90% witha recurrence rate of 5%.
26Indications for catheter ablation of idiopathic ventricular tachycardia Monomorphic VT that is causing severe symptomsMonomorphic VT when antiarrhythmic drugs are not effective, not tolerated, or not desiredTachycardia-induced cardiomyopathy
27Contraindication for catheter ablation of idiopathic ventricular tachycardia Presence of a mobile ventricular thrombusAsymptomatic PVCs and/or non-sustained VT that are not suspected of causing or contributing to ventricular dysfunctionVT due to transient, reversible causes, such as acute ischemia, hyper-/hypokalemia, or drug-induced torsade de points
28How to ablate VT Mapping Basic electrophysiologic study Pace mapping (identical 12-lead ECG morphology)Activation mapping (earliest activation site)Electroanatomic mapping (Carto, Navx, Enside Array, Magnetic remote control) (voltage, anatomy)Ablation successful rate: 90 %
29Mapping Tool for OT-VT ECG morphology: Could be non-inducible Pacing morphologycould be large area 2 cm2: different chamber, scar, or epicardiumActivation mapMore accurate: remain unsuccess: more mapping sites, epicardium
35Important overlapping nature of the outflow tract course! RVOT and PA lie anterior and to the left of the LVOT and aorta.The right coronary cusp (RCC) of the aortic valve is directly posterior to the thick posterior infundibular portion of the RVOT. The true septum of the RVOT is not leftward but rather posterior and similarly, the septal portion of the LVOT is its anterior portion, just behind the RVOT.catheter placed in the RCC will record a large amplitude ventricular electrogram, the origin of which is mainly the right ventricular myocardium and partly the supravalvar left ventricular myocardiumRecordings from the left coronary cusp (LCC) may map a supravalvar left ventricular myocardium, portions of the distal peripulmonary valve, posterior right myocardium, as well as the mitral annular left ventricular myocardium.The noncoronary cusp (NCC) of the aortic valve generally is surrounded only by atrial structures, and thus, mapping in the NCC will identify predominately atrial signals that may arise either from the right atrium, left atrium, or the interatrial septum. Therefore, ablation in the NCC is rarely required for ventricular tachycardia, but more often for atrial tachycardias from these regions. However, supravalvar posterior left ventricular tachycardias can occasionally be ablated with a catheter placed in the depths of the NCC .35
41Management of RVOT VTCAG and 2D echo are usually normal, but MRI may show abnormalities of the RV in up to 70% of patients (focal thinning, diminished systolic wall thickening and abnormal wall motion).RVOT VT should be distinguished from ARVD: ECG morphologic features similar to RVOT VT but DOES NOT terminate with adenosine.It should be strongly considered for the following patients with a potentially malignant form of OT VT:a) a history of syncope; b) very fast VT; c) ventricular premature beats with a short coupling interval.
44Requirement of non-contact mapping system for VT mapping Pacing mapping may not sensitive to locate the sites of foci in certain patients with focal VT, in the presence of large scar area.VT could be non-sustained and unstable. It is difficult to map the entire chamberOne beat analysis of dynamic substrate by NCM may be useful to treat these patients.In conclusion, the noncontact mapping provides accurate global unipolar Eg and resultant isopotential maps throughout the chamber. It is an useful guide for mapping and guide ablation of unstable, nonsustained, and multiple focal tachycardia from one-beat analysis.44
52Mechanism of fascicular VT The most likely mechanism of idiopathic left ventricular tachycardia is reentry with an excitable gap and a zone of slow conduction since can be initiated and terminated with programmed stimulation as well as the demonstration of entrainment of the tachycardia with rapid pacingVerapamil sensitive
55Management of fascicular VT The long-term prognosis of patients with fascicular VT without structural heart disease is very good.Arrhythmias in patients with sporadic, well-tolerated episodes of idiopathic left ventricular tachycardia may not progress despite absence of pharmacologic therapy.Treated with oral verapamil (120 to 480 mg/day).Ablation successful rate: >95%
57Where to TargetDiastolic potential (P1) in the midseptum of LV. P1-QRS= msecIf P1 could not be identified, target the fused and earliest Purkinje potential (P2)Successful ablation revealed P1 during SR could be a marker of successful ablation.Ablation successful rate: >95%Complication: trivial
58Role of electroanatomic mapping systems Refers to point by point (contact) mapping combined with the ability to display the location of each point in 3-dimensional space.Carto, Navx, Ensite array, Magnetic remote systemFunctions:1. non-fluoroscopic localization of the ablation catheter2. display of intracardiac electrograms (scar, low voltage zone)3. interpretation of mechanism of arrhythmia (focal or macroreentry)Always useful in scar-related VTs; can be useful in idiopathic VTs.
62ConclusionIdiopathic VT concerns a small subgroup of patients with VT. Depending on tachycardia mechanism, idiopathic VT may respond to β-blockers, Ca2+ channel blockers or to vagal manueuvers, although radiofrequency ablation is curative in most patients.Patients usually continue to follow up to rule out latent progressive heart disease such as arrhythmogenic right ventricular dysplasia (ARVD) or other forms of cardiomyopathies.