Case management:
Prior to the procedure, cardiac CT revealed a large tumor, which
involved the interventricular septum and most of the LV anterior wall.
The LV was somewhat compressed but with normal LV ejection fraction. A
small amount of ventricular tissue could be appreciated between the
right coronary cusp (RCC) and the tumor (Figure 1). Surgical resection
was deemed not feasible due to the tumor’s size and its juxtaposition to
the coronary arteries. When not in VT, the patient’s functional capacity
was very good, and it was felt that cardiac transplant could be deferred
if VT control could be achieved.
At EP study, left ventricular voltage mapping revealed an overall normal
endocardial bipolar voltage (> 1.5 mV), but a large area of
decreased (<8.3 mV) unipolar voltage extending from the LVOT
onto the basal anterior wall, corresponding with the area of the tumor.
Two hemodynamically tolerated VTs were induced by programmed stimulation
(PES) (Figure 2). Entrainment mapping was limited by spontaneous VT
termination and cycle length oscillations.
VT1 had RBBB morphology and activation mapping demonstrated a focal
breakout at the mid lateral LV where signals were simultaneous with the
QRS onset and entrainment was consistent with a bystander site near the
exit (Figure 2). This was consistent with an epicardial or an intramural
component to the reentry circuit. Following spontaneous termination,
pace mapping from the leftward aspect of the right coronary cusp (RCC)
resulted in a perfect pace match to VT1 with a long Stim-QRS interval,
potentially consistent with a proximal isthmus site (Figure 3A).
Ablation in the RCC abolished this VT.
VT2 had LBBB morphology, and activation mapping demonstrated endocardial
breakout in the same region as the putative proximal isthmus for VT1,
just below the RCC, with activation proceeding toward the septum (Figure
2). Pace mapping here resulted in a perfect pace match (Figure 3A) with
relatively short stim-QRS and ablation abolished the VT, consistent with
a distal isthmus site. Ablation here also resulted in complete AV block.
Further ablation was performed in the peri-aortic region extending
toward the mid ventricle in the region of low unipolar voltage (Figure
3B). No VT was inducible following ablation with up to three
extrastimuli following two drive trains (400 and 600ms). He recovered
well after the procedure. ICD was upgraded to a CRT system and he has
remained free of recurrent VT at 60 day follow-up . Cardiac PET/CT
performed approximately 6 weeks after ablation did not demonstrate any
metabolic activity in the tumor, consistent with a benign process.
He underwent evaluation for heart transplantation and was eventually
transplanted successfully at another institution approximately four
months following the ablation procedure. A biopsy from the cardiac mass
was obtained following transplantation which revealed benign
fibroblastic proliferation admixed with collagen, focal chronic
inflammation, and occasional calcifications.
Conclusions: We speculate that this large tumor was the result
of a slowly growing cardiac fibroma that, perhaps from pressure,
resulted in fibrosis that extended deep to the endocardium in the
anterior wall creating the substrate for reentry. This presented as two
VT circuits that shared a common isthmus between the mass and the aortic
root which could be ablated from the endocardium.