ACCESSORY PATHWAYS AND SVT Neil Grubb Royal Infirmary of Edinburgh
Bypass tracts - properties accessory AV connections usually endocardial may exhibit unidirectional conduction conduction properties similar to His / Purkinje tissue not adenosine / calcium sensitive class Ic drugs most effective posteroseptal tracts may exhibit nodal properties beware epicardial pathways
Avoiding Difficulties Preparation, preparation, preparation! have documentation of tachycardia onset and offset 12 leads if available pre-procedure echocardiogram identify atrial enlargement associated structural disease (e.g. Ebstein s) examine 12 lead in sinus rhythm pre-excitation pattern frontal axis and precordial transition helpful (rotation)
Anterior Left Sided
Mid Septal Right Sided
Lateral Left Sided
Posteroseptal Right Sided
Posterior Left Sided
Free Wall Right Sided
Middle Cardiac Vein
Para-Hissian
Mapping: atrial pacing
Mapping: ventricular pacing
OAVRT: entrainment ΔVA (VA V pacing VA SVT ) <85ms PPI SVT CL <115ms
Polarity mapping
Atrio-fascicular Pathways
Mahaim: atrial insertion
THE DIFFICULT CASE Difficult Anatomy
Anatomical Challenges Inability to cannulate coronary sinus Eustachian valve / take off angle abnormal cardiac rotation (ECG, look at His / RV axis) big right atrium PRACTICAL POINTS use deflectable catheter; try from above do you need to see left sided activation? coronary arteriogram with venous phase
Anatomical Challenges Trans-septal puncture abnormal cardiac rotation (ECG, look at His / RV axis) thickened septum (previous procedures) PRACTICAL POINTS use CS and RV catheters as axis markers try different curve Do NOT puncture if it feels wrong! Consider TOE or ICE guidance and extra sharp needle
THE DIFFICULT CASE Septal conduction: AVNRT versus AVRT
Differential diagnosis of narrow QRS short RP tachycardia AVNRT AVRT with septal pathway accelerated junctional tachycardia atrial tachycardia with long PR interval
Criteria to support AVNRT critical prolongation of A-H interval initiates tachycardia concentric atrial activation, septal VA <65ms ventricular overdrive manoeuvre >115ms delta HA interval more positive than 10 Para-Hissian pacing generates nodal response decremental VA conduction termination by early PVC when His bundle nonrefractory
Para-Hissian pacing
Para-Hissian pacing
Ventricular Overdrive Manoeuvre Post-pacing interval = 508ms Tachycardia CL = 328ms PPI-TCL = 180ms (if PPI-TCL >115 suggests AVNRT)
Delta HA Interval based on the sequence of His bundle and atrial activation being fundamentally different in AVRT and AVNRT during tachycardia and during V pacing during tachycardia, in AVNRT His and A are activated simultaneously whereas in AVRT His and A are activated sequentially The opposite is true during V pacing
Delta HA Interval HOW TO PERFORM MANOEUVRE Measure HA inverval during tachycardia Measure HA interval with ventricular pacing Delta HA = HA paced HA SVT Delta HA more negative than -10 indicates AVRT Delta HA more positive than -10 indicates AVNRT AVNRT AVRT Mean SVT HA 104 ms 241 ms Mean paced HA 127 ms 151 ms Mean delta HA 21 ms -85 ms Miller JH et al. Am J Cardiol 1991;68:1037-1044
Differential pacing
Differential pacing Martinez-Alday et al. Circulation 1994;89:1060-1067 HOW TO PERFORM MANOEUVRE pace at RV apex measure septal VA interval pace at RV base measure septal VA interval Ventriculoatrial index = VA (apex) VA (base) VA index > 10 ms always predicts accessory pathway
Criteria to support AVRT inducible with ventricular pacing * advancement (reset) of tachycardia with Hissynchronous VPBs nondecremental VA conduction failure of VA conduction to block with adenosine
THE DIFFICULT CASE Posteroseptal Pathways
CLOSING COMMENTS good preparation avoids many potential problems In WPW syndrome the surface ECG tells you where the pathway is most tachycardia mechanisms can be worked out using old-fashioned methods define the anatomy if you struggle with a posteroseptal pathway