Discussion
Idiopathic ventricular arrhythmia (VA) from the ostium of the left
ventricle could be eliminated by the radiofrequency (RF) application
within the aortic sinus cusps (ASCs). The VA originating from the
junction between the left and right coronary cusp was rare, however, the
elimination needs to the RF application below the aortic
cusps.[1] Of interest, this VA had a
unique electrocardiographic characteristic of a qrS pattern in at least
one of the leads V1–V3 or abrupt V3 transition (Figure
1A).[2,
3] The tip of the ablation catheter
should be positioned at this site by deflecting the loop of the ablation
catheter in the left ventricle cavity or on the non-coronary cusp, but
this technique was relatively difficult to stabilize the ablation
catheter due to the limited anatomical space. In the current case,
although electrogram at the ablation catheter was sub-optimal, RF
application at the left coronary cusp (LCC) – right coronary cusp (RCC)
junction above ACSs could eliminate the VA (Figure 1C). The local
electrogram at the successful ablation site showed a tiny dull
ventricular potential with low R wave amplitude. The distal tip of the
ablation catheter in the fluoroscopy was located behind the coronary
sinus catheter in the right anterior oblique view (Figure 1B, C). These
findings suggest the ablation catheter is more likely to be located
close to the LCC-RCC junction above the ASCs.
To identify radiofrequency lesion extension, high-resolution
late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) was
performed three months after the catheter ablation. The LGE-MRI of ASC
and left ventricle was acquired using a 3D inversion recovery,
respiration navigated, electrocardiogram-gated, T1-FFE sequence in the
transverse plane 15 minutes after the contrast injection, as previously
reported. The typical parameters were as follows: repetition time/echo
time = 4.7 / 1.5 ms, voxel size = 1.43 × 1.43 × 2.40 mm (reconstructed
to 0.63 × 0.63 × 1.20 mm), flip angle = 15°, SENSE = 1.8, and 80
reference lines. The inversion time (TI) was set at 280 – 320 ms using
a Look-Locker scan. LGE-MRI could demonstrate that the strong LGE could
be found at the ventricular myocardium beyond the LCC – RCC junction,
so-called myocardial crescents. However, we have clearly demonstrated
that the LCC – RCC junction does not involve the myocardial
crescents.[4] The resign corresponds
to the myocardium beneath the interleaflet triangle, which is located
within the left ventricle. Therefore, it is better reached from the
below ASC approach with caution to the thin interleaflet triangle. In
the current case, fortunately, RF lesion could extent from the
myocardial crescent beneath the LCC – RCC junction to the myocardium
beneath the interleaflet triangle (Figure 2). In case when the accurate
mapping and catheter stability was difficult beneath the ASCs, careful
mapping and RF application at the LCC – RCC junction above the ASCs
might be acceptable option to eliminate the VA arising from the
myocardium beneath the interleaflet triangle.