PMC9240706_01
Electrocardiogram and endocardial mapping. (A) Electrocardiogram of monomorphic ventricular tachycardia showing ventriculoatrial dissociation (black arrows). (B) Intracardiac electrogram revealing an early signal (-40 ms) before the QRS complex during the ventricular tachycardia rhythm. (C,D) Right and left anterior oblique projections of endocardial mapping using intracardiac echocardiography. CS, coronary sinus; RV, right ventricle.
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F1
On admission, electrocardiography demonstrated monomorphic VT with a right bundle branch block pattern, a Q wave in lead V1, left superior axis deviation, and ventriculoatrial dissociation, suggesting an exit site in the posteromedial papillary muscle region of the left ventricle (Figure 1A). Cardiac computed tomography (CT) revealed no significant stenotic lesions in the coronary arteries and no structural heart disease (Supplementary Figures 1A,B), indicating tachycardia-induced cardiomyopathy. During endocardial mapping, intracardiac electrograms showed fractionated potentials around the posteromedial papillary muscle with the earliest activation (-40 ms) (Figures 1B-D). During the first ablation, the VT was terminated for 30 s with an inaudible steam pop recorded by ICE (Figure 2D and Supplementary Video 1), and a sudden rise in electrical impedance was not noted.
Catheter ablation for ventricular tachycardia. (A) Successful ablation site on the left posteromedial papillary muscle (white arrow). (B,C) Unipolar Q signal on successful ablation site and three-dimensional activation map. (D) Termination of ventricular tachycardia with steam pops.
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F2
Under direct ICE visualization (Figure 2A), endocardial ablation using an irrigated-tip catheter (SmartTouch, Biosense Webster) and 40 W was applied to target the earliest site that showed the initial Q wave in the unipolar signal with 10-15 g of contact force (Figures 2B,C). During the first ablation, the VT was terminated for 30 s with an inaudible steam pop recorded by ICE (Figure 2D and Supplementary Video 1), and a sudden rise in electrical impedance was not noted. Echocardiography showed improved LV systolic function with LV ejection fraction of 50% and a decreased LV size with LV end-diastolic dimension of 52 mm, but a pseudoaneurysm (26 x 9 mm) that has the ratio of the maximum diameter of the orifice to the maximum internal diameter of the cavity was lesser than 0.50 was identified at the base of the LV posteromedial papillary muscle where a steam pop had occurred without pericardial effusion (Figure 3B and Supplementary Video 2).
Serial follow-up of the ablation site using transthoracic echocardiography. (A) The day after the procedure, no structural changes around the ablation site were observed. (B,C) After 2 months of follow-up, the development of a pseudoaneurysm on the ablation site (white arrow) was confirmed through transthoracic echocardiography and contrast-enhanced computed tomography.
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F3
The transthoracic echocardiography performed the next day showed no evidence of mitral regurgitation or tissue defects in the ablation sites (Figure 3A). Echocardiography showed improved LV systolic function with LV ejection fraction of 50% and a decreased LV size with LV end-diastolic dimension of 52 mm, but a pseudoaneurysm (26 x 9 mm) that has the ratio of the maximum diameter of the orifice to the maximum internal diameter of the cavity was lesser than 0.50 was identified at the base of the LV posteromedial papillary muscle where a steam pop had occurred without pericardial effusion (Figure 3B and Supplementary Video 2). One year later, cardiac CT revealed that the pseudoaneurysm that typically has a neck narrower than the diameter of the aneurysm remained present but showed no signs of a size change or other complications such as thrombus formation (Figure 3C).