2.2 Case series
We performed electrophysiological study, catheter ablation and mapping
to identify the location of the accessory pathway with velocity map in
three patients (2 male, median age 45 yo) with WPW syndrome.
First, we started with electrophysiology study to assess the electrical
property and the risks of accessory pathway. Then, patients underwent
standard local activation time (LAT) mapping with Advisor HD Grid
multipolar catheter for localization of AP. Advisor HD Grid was used in
order to take advantage of OT and new wave speed map.
After AP localization we studied the conduction velocity values
registered at the level of the pathway. Normal atrial conduction
velocity was found to be 1±0.1 m/s, accessory pathway conduction
velocity 2.8±0.02 m/s (Fig 1).
Atrio-ventricular nodal reentrant tachycardia (AVNRT)
Overview
Dual AV node physiology characterizes the normal AV node function, and
the presence of dual AV node pathways can be demonstrated in most
individuals. Although the potential substrate for AVNRT (dual pathways)
is normally available, only a minority of normal individuals develop AV
nodal reentry. In fact reentry requires other conditions, first of all
refractoriness over the two pathways and the presence of a synchronous
trigger. Tipically dual pathways have different capacity of conduction
and refractoriness (slow and fast).
Case series
Patients who have AVNRT generally have dual atrioventricular nodal
physiology and the ability for a reentrant arrhythmia to occur involving
the atrioventricular (AV) node. Patients in general have a fast pathway
in which normal conduction proceeds down during sinus rhythm.
However, patients with AVNRT have one or more slow pathways or
additional circuits near the coronary sinus and connected to the AV node
that are capable of electrical conduction. In the most common or
“typical form” of AVNRT, patients become stuck in a reentrant loop
with conduction proceeding down the slow pathway as the anterograde limb
of the circuit and back up the fast pathway as the retrograde limb.
Wave speed map can be useful to give numeric value of how fast or slow
are the two pathways for patients with dual atrioventricular nodal
physiology.
We studied two patients presenting to our institution for ablation of
AVNRT.
First, we started with electrophysiology study to assess the presence of
dual nodal pathways and then we used Advisor HD Grid to characterize the
conduction velocity of the slow and fast pathways in sinus rhythm.
Normal atrial conduction velocity was found to be 1±0.1 m/s and slow
pathway 0.9±0.1 m/s.
We compared standard voltage map and wave speed map indentifiyng the
slow pathway localization (Fig 2).
Atrial flutter
Overview
Atrial flutter are one or the most commons atrial arrhythmia. Atrial
flutter are classified in typical, who are cavotricuspid isthmus
(CTI)-dependent, and atypical. The electrophysiological substrate
underlying CTI-dependent atrial flutter has been shown to be
macroreentry around the tricuspid valve annulus. In most cases typical
atrial flutter have counterclockwise direction around tricuspid valve
annulus, in a minority of patients, the direction is clockwise. In both
cases the ablation target is bidirectional block through CTI. Atypical
or non isthmus-dependent atrial flutter and atrial macroreentry requires
fixed or functional block and regions of slow conduction. This is the
result in the most cases of catheter ablation or surgery that involves
right or left atriotomies.
Case series
We report 6 cases of atrial flutter (3 atypical, 3 typical) mean age
66.67±9 years. Patients underwent catheter ablation and atrial mapping
with the new Ensite X system, using the HD Grid. We compared the
standard local activation map (LAT) of the critical isthmus (Figure 3a)
with the slowest conduction zone identified with OT (Figure 3b). In
patients with atypical flutter critical isthmus were identified in LA
roof, in mitral isthmus and in LA posterior wall, near left superior
pulmonary vein ostium. Mean velocity value for CTI was 1.08 ± 0.3 m/s,
mean velocity value for LA atrial flutter critical isthmus was 9.86 ±
7.26 m/s. The conduction velocity map was used to identify areas of slow
conduction throughout the isthmus and wave velocity values of 0.45 ±
0.3 m/s were found to discriminate critical areas of the flutter
circuits. The mean LAT map area values are 3.89 ± 2.22 cm2 and the
slowest conducting zone identified by OT has a mean area of 1.26 ±
0.82 cm2. A single RF delivery at the slowest site of critical isthmus
resulted in rapid cessation of the arrhythmia in all cases.
Atrial fibrillation
Overview
Pulmonary vein isolation (PVI) represents the primary target of current
catheter ablation techniques for the treatment of atrial fibrillation.
However, PVI has proven to be effective in paroxismal AF, in patients
with persistent and long standing persistent AF this seems not enough to
obtain a high efficacy [5,6,7]. Recently, some studies have shown
that Bachmann’s bundle plays a significant role in the genesis of AF and
its ablation leads to increase efficacy in terms of AF-free survival at
follow up [8].