CASE PRESENTATION
An 80‐year‐old man was referred to our facility for catheter ablation of
an atrial tachycardia (AT) that developed after atrial fibrillation (AF)
ablation. The previous procedure consisted of pulmonary vein isolation
and cavotricuspid isthmus ablation. An AT with a tachycardia cycle
length of 230 ms was detected on a baseline surface electrocardiogram
(Fig. 1A). A decapolar catheter was positioned in the coronary sinus.
The CARTO 3 system (Biosense-Webster, Inc., Diamond Bar CA) was used for
electroanatomical mapping. Contact mapping was performed using a 20-pole
high-density mapping catheter (PENTARAY; Biosense-Webster, Inc). The
activation map suggested a dual-loop tachycardia mechanism; one circuit
is a peri-mitral AT with a counterclockwise direction, and another is a
roof-dependent AT around the left pulmonary veins (Fig. 1B and 1C).
Since the lateral mitral isthmus was the common isthmus of the two
circuits, we performed Et-VOM to create a block line on the lateral
mitral isthmus. After occluding the vein of Marshall with an
over-the-wire balloon catheter, 10 ml of 98% ethanol was injected in
three divided doses. We did not observe the leakage of ethanol into the
coronary sinus. During Et-VOM, the tachycardia cycle length was
increased to 290 ms. After Et-VOM, the local staining was observed
around the vein of Marshall (Fig. 2A). In the voltage map, an extensive
endocardial scar was visible on the left atrial ridge and lateral mitral
isthmus (Fig. 2B and 2C). Although the diaphragmatic motion was normal
at baseline (Fig. 3A and 3B, and Supplementary Movie 1), the left
phrenic nerve paralysis (PNP) was recognized after Et-VOM (Fig. 3C and
3D, and Supplementary Movie 2). A review of the fluoroscopic image
revealed that the motion of the left diaphragm weakened immediately
after the initial injection of ethanol. Seven minutes after the last
ethanol injection, the left PNP gradually started to relieve. Adjunctive
radiofrequency application to the lateral mitral isthmus terminated the
AT, and the block line was finally created. At the end of the procedure,
the left PNP was completely relieved, and no symptoms were observed
after the procedure.