Multiple Arrhythmogenic Substrate for Tachycardia in a



Majid Haghjoo, Arash Arya, Mohammadreza Dehghani, Zahra Emkanjoo, 67
Amirfarjam Fazelifar, MohammadAli Sadr-Ameli.,
“Multiple Arrhythmogenic
Substrate for Tachycardia in a Patient with Frequent Palpitations”

had no chance to capture any 12-lead electrocardiogram (ECG) during palpitation. The only
evidence of arrhythmia in this patient was a sustained SVT with heart rate about 185 beats/min
recorded in one of her 24-hour holter monitoring. Two antiarrhythmic agents (propranolol,
verapamil) were tried in our patient with no success.

The baseline standard 12-lead ECG showed no any abnormality. The physical
examination and transthoracic echocardiography were unremarkable.

After obtaining of written informed consent, electrophysiological study (EPS) was done
in post absorptive, and non-sedated state. All antiarrhythmic drugs were interrupted for at least
five half-lives before procedure. Three 6F diagnostic catheters (Daig, St. Jude Medical Inc.,
Minnetonka, MN, USA) were inserted via left femoral vein and placed in the high right atrium
(HRA), His bundle position, and right ventricular apex (RVA), respectively. A 7F decapolar
catheter with 2/2/2 mm electrode spacing (Marinr® CS; Medtronic, Inc., Minneapolis, MN,
USA) positioned retrogradely via right femoral vein into the coronary sinus (CS) for coronary
sinus mapping. During programmed electrical stimulation (PES) from RVA, nondecremental
retrograde conduction was seen with earliest atrial activity on the proximal pole of CS catheter
(located at the ostium of CS). No ventricular preexcitation was observed on atrial incremental
pacing, compatible with a concealed right posteroseptal (RPS) accessory pathway. During atrial
extrastimulation, a sustained narrow complex tachycardia (cycle length=320 ms) was induced
reproducibly with earliest retrograde atrial activity in the proximal CS (
Figure 1A). This
tachycardia easily terminated by overdrive ventricular pacing and timed ventricular extrasystole
during His refractoriness advanced atrial activity.

Application of RF energy at right posteroseptal area resulted in loss of conduction over
the accessory pathway (AP) (
Figure 2A). Repeat ventricular PES revealed 1:1 vetriculoatrial
conduction with earliest atrial activity on the HRA catheter, compatible with concealed right free
wall (RFW) AP and atrial PES culminated in induction of a new narrow complex tachycardia
(cycle length=340 ms) well-matched with orthodromic AVRT using RFW-AP (
Figure 1B).
Atrial advancement was also seen during the second AVRT (RFW). Mapping of tricuspid
annulus localized the site of second AP on the posterolateral area. RF energy delivery at this area
interrupted AP conduction (
Figure 2B) and VA conduction shifted to the normal pathway.
Repeat PES under isoproterenol infusion leads to induction of a new narrow complex
tachycardia (cycle length=360 ms) compatible with typical AVNRT (
Figure 1C). AVNRT
became noninducible after successful slow pathway (SP) ablation. During postablation
arrhythmia induction under isoproterenol infusion, a sustained, self-terminating atrial
tachycardia was induced but no attempt was made for ablation (
Figure 1D). Atrial origin of
tachycardia was confirmed by V-A-A-V pattern after termination of ventricular pacing during
tachycardia (
Figure 2C). She left the EP laboratory in good condition without any
complications.

During 8-month’s follow-up, she was free of symptoms with no antiarrhythmic drugs and
no recurrence of tachycardia was seen.

Discussion

The combination of AVNRT-AVRT1,2,3 (including multiple bypass tracts), AVNRT-AT4, and
AVRT-AT
5 was reported. To the best of our knowledge, our case is the first patient reported
with a combination of two AVRT, typical AVNRT, and AT.

As atrioventricular (AV) bypass tract is a congenital abnormality due to developmental
defect in the AV rings, it is not surprising that multiple bypass tracts can be present in the same
patient. Incidence of multiple bypass tracts ranges from 3.1-30%
6,7,8, and the most common
combination has been RPS with RFW bypass tracts.
6 The incidence of multiple APs is higher in:
1) patients with antidromic AVRT; 2) patients in whom atrial fibrillation results in ventricular

Indian Pacing and Electrophysiology Journal (ISSN 0972-6292), 5(1): 66-70 (2005)



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