Cardiac Resynchronization Therapy for Left Ventricular Dysfunction Via a Remnant Persistent Left SVC After Accessory Pathway Ablation

Case Description

A 27-year-old male with previous radiofrequency ablation for Wolff-Parkinson-White syndrome at the age of 4 was referred for repeat ablation due to recurrent symptomatic palpitations for the last two years with residual pre-excitation. Records from his prior ablation showed evidence of intermittent complete AV block post ablation. Sometime after his ablation, he developed LV dysfunction and was lost to follow-up, but remained compliant on his heart failure medications. The patient now presents with NYHA class III symptoms on optimized medical therapy precipitated by dietary indiscretion. Twelve-lead ECG revealed sinus rhythm, QRS interval of 198 msec, frequent PVCs and pre-excitation with R<S in V1, and delta waves positive in lead I, II, and aVF, suggesting a right free wall accessory pathway (AP) (Figure 1A). During symptomatic palpitations, he exhibited sinus tachycardia with pre-excitation and frequent PVCs, but never SVT or sustained VT. Previous ambulatory monitoring did not reveal any sustained tachycardia. 

Transthoracic echocardiography, nuclear myocardial perfusion imaging, and cardiac MRI revealed absence of focal coronary artery disease or any significant scar, but demonstrated severe global LV dyssynchrony and hypokinesis with an LVEF of 25% (left ventricular end-diastolic volume [LVEDV] 242 mL, left ventricular end-systolic volume [LVESV] 145 mL). 

During patient observation in the coronary care unit, telemetry show fixed QRS duration without clear evidence of AV nodal conduction. We discussed with the patient the possibility that the AP may be his only atrioventricular connection, and ablation would lead to pacemaker dependence. Although LV function could improve from elimination of the accessory pathway alone, we also considered the need for ICD implantation for primary prevention, as well as resynchronization therapy. The patient elected to proceed with ablation of the accessory pathway.

Following informed consent, he underwent electrophysiologic study under moderate sedation using three-dimensional mapping (EnSite NavX, Abbott). Two 6 French (Fr) quadripolar catheters were advanced through the right femoral vein and placed in the anatomic His and right ventricular positions. A 7 Fr duodecapolar catheter was advanced and positioned in the right atrium due to repeated failed attempts in cannulating the CS ostium.

Baseline electrograms (Figure 1B) revealed sinus rhythm with pre-excitation (PR interval 66 msec). A His signal was not able to be observed during the study, and there were no changes in QRS duration with isoproterenol, adenosine, or atrial extrastimulation. There was no evidence of decremental conduction suggesting absence of AV nodal conduction, thereby suggesting exclusive antegrade conduction via the AP. Anterograde AV block was observed with 500 msec drive train and 300 msec extrastimulus, and ventricular effective refractory period (ERP) was reached with drive train at 450 msec and 250 msec extrastimulus. The earliest atrial signal during ventricular pacing was localized to the right anterior/anteroseptal region. There was no evidence of dual AV node physiology or evidence of decremental AV or VA conduction. No SVT or sustained VT was induced during the EP study with or without isoproterenol. 

Mapping of earliest ventricular signal in sinus rhythm was done using an 8 Fr ablation catheter (Safire TX, Abbott) through an 8.5 Fr small curl tip deflectable sheath. The earliest ventricular signal preceding the delta wave was localized and bracketed corresponding to a right anteroseptal location as confirmed by fluoroscopy (1 o’clock in LAO) (Figures 1C and 2). As there was no evidence of intact AV nodal conduction, we applied radiofrequency energy (8 mm non-irrigated, 60°C, 50 W) with resultant loss of AP conduction, complete heart block, and exclusive ventricular pacing from the RV quadripolar catheter. Subsequent testing did not show any evidence of AV or VA conduction.  

We then proceeded to implant a CRT-D system given his non-ischemic cardiomyopathy (NICM) and complete heart block. RA and RV leads were positioned in standard locations. A CS venogram was performed via an atretic CS ostium (Figure 3, Video 1, Video 2, Video 3, Video 4, Video 5, Video 6, Video 7, Video 8, and Video 9), revealing communication with the true coronary sinus and lesser cardiac vein, with a small residual vein of Marshall/left superior vena cava (LSVC) as well as a posterior branch vein giving rise to both a posterolateral and anterior branch vein (Figure 3). The remnant LSVC was confirmed via axillary vein venography. We were unable to advance any wire or catheter into the CS via the RA through the atretic ostium; therefore, the decision was made to attempt CS lead delivery via the remnant of the left SVC. The persistent left SVC was small and contained a high-grade focal stenosis. The remnant left SVC joined the proper CS drainage and made an acute 45-degree bend (Figure 3A) with a good posterolateral vein for CS lead placement. The proximal stenosis persisted; using various venoplasty techniques with a non-compliant balloon (Fortrex 0.035" 5 x 40 mm; Medtronic) (Figure 4A), we were able to insert a 10 Fr long sheath through the stenosed lesion (Figure 4B). Using an inner CS delivery sheaths, a quadripolar CS lead was able to be delivered into the posterolateral branch vein (Figure 5). Testing demonstrated acceptable thresholds on multiple poles. Pacing QRS with the CRT system was 164 msec. The patient’s heart failure symptoms and ectopy burden improved post procedure, and he was subsequently discharged home. Follow-up echocardiography one-month post procedure revealed a significantly improved LVEF of 40% (LVEDV 176 mL, LVESV 97 mL).

Discussion

To our knowledge, this is the first reported case of CRT-D implantation after accessory pathway ablation for cardiac resynchronization via a remnant LSVC.

Our case demonstrates a challenging clinical decision to ablate an AP in a patient without any AV nodal conduction for cardiomyopathy likely secondary to ventricular dyssynchrony from right anteroseptal AP, followed by abnormal anatomy for CS lead placement through a small remnant PLSVC to achieve CRT. 

Previous reports have documented the coexistence of APs and anomalies in CS anatomy ranging from atresia, including an unroofed CS and persistent remnant left SVC.^1-5 The embryological basis derives from a spatio-temporal association of CS development with atrioventricular division by the annulus fibrosis. Here we incidentally discovered a small remnant LSVC after difficulties with CS cannulation during the ablation procedure. 

This patient’s case presents a challenging dilemma. Prior to the ablation, we had concern for absence of AV node conduction; therefore, ablating the accessory pathway would make the patient pacemaker dependent. We discussed this risk with the patient, and due to his cardiomyopathy and need for a defibrillator, he elected to have ablation and CRT-D implantation.

Workup of his cardiomyopathy did not reveal a clear etiology. He had neither a significant family history of cardiomyopathy, nor other social history or habits that could explain his dilated cardiomyopathy. Given the patient’s only AV conduction is via a single accessory pathway and AV node was likely ablated from his initial ablation, AVRT and AVNRT were not possibilities. Atrial arrhythmias were not seen on ambulatory monitoring and were not inducible during the EP study. This decreased the likelihood of tachycardia-mediated cardiomyopathy. Cardiac imaging including cardiac MRI failed to demonstrate any significant scar suggesting the cardiomyopathy was reversible. We had a high suspicion that his cardiomyopathy was likely related to dyssynchrony from RV activation via accessory pathway. Prior reports have shown causal relation between right-sided accessory pathways leading to dyssynchronous ventricular activation and adverse remodeling; elimination of AP conduction and restoring normal conduction lead to reverse remodeling and improvement/normalization of LV function.^6-8 The timing of improvement ranges from acute improvement up to months after ablation.⁹ 

In our patient, within one month there was already evidence of left ventricular reverse remodeling with a significant decrease in left ventricular volume and improvement of ejection fraction on echocardiogram. 

CS lead implantation in patients with LSVC poses several technical challenges that have been well described previously.¹⁰ In this case, several difficulties were encountered. The remnant of the left SVC was a small vessel that did not accommodate a larger sheath for CS lead delivery. In addition, the stenosed distal part of the remnant left SVC makes sheath delivery and manipulation particularly challenging. Venoplasty techniques with a non-compliant balloon were useful to help advance the sheath through the stenosed vein segment. 

The next challenge was selective vein cannulation. There were multiple acute venous angulations and a focal stenosis in the proximal PLSVC, followed by an acute bend in the distal PLSVC to the proper CS, and finally, the posterolateral branch vein. Deployment of the CS lead required several attempts but was ultimately successful, with satisfactory lead parameters and avoidance of phrenic nerve capture. 

Conclusion

In this case, we described a patient with a right anteroseptal AP with absent AV nodal conduction but frequent PVCs, presenting with worsening cardiomyopathy likely due to chronic RV activation, giving rise to a LBBB-like activation sequence with frequent PVCs. We successfully ablated the AP and implanted a CRT-D system, thus restoring ventricular synchrony and left ventricular function, and reducing PVC burden.

Disclosures: The authors have no conflicts of interest to report regarding the content herein.  

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