Ablation of a Left-Sided WPW in a Patient with Total Upper Venous Return through a Persistent Left Superior Vena Cava

A case of Wolff-Parkinson-White (WPW) in a patient with a persistent left superior vena cava is described. The peculiar characteristics of this rare congenital vascular anomaly regarding catheter ablation are reviewed.

Clinical Case

A 23-year-old man was referred for catheter ablation of WPW with left-sided accessory pathway for recurrent presyncopal spells due to preexcited atrial fibrillation (AF). Normal valve and left ventricular function were assessed with echocardiography. Dilation of the coronary sinus (CS) was noticed on the echocardiogram, suggestive of a persistent left superior vena cava (PLSVC). The following catheters were inserted through the femoral vein: three quadripolar catheters were placed in the high atrium, AV junction and right ventricular apex. A ten-electrode steerable catheter (Polaris Dx^™, Boston Scientific) was placed easily in the CS. Baseline underlying electrophysiology parameters were as follows: AH = 100 msec; HV = 33 msec. The accessory pathway did not have retrograde conduction. The pathway effective refractory period was 270 ms at 600 ms pacing drive train from the high right atrium. Shortest RR interval during AF was 230 msec. Atrioventricular reentrant tachycardia was not induced.

Catheter Ablation of WPW

An intracardiac echo 9 French phased array catheter ViewFlex^™ (St. Jude Medical) and the electroanatomical mapping system EnSite NavX^™ (St. Jude Medical) were used to help with catheter manipulation, mapping the location of the pathway and to minimize fluoroscopy. A standard 4-mm tip deflectable ablation catheter was used for mapping and ablation. 

Severe dilatation of the CS was confirmed with intracardiac ultrasound (Figure 1B). The CS catheter was advanced into the PLSVC and placed into the innominate vein (Figure 1A). Contrast venography showed absence of a right superior vena cava with thoracic venous return through a persistent left superior vena cava (Figure 1C).

Mapping of the accessory pathway was done with atrial pacing following conventional electrophysiology techniques. First, we attempted catheter ablation of the ventricular insertion of the accessory pathway through the CS (epicardial). Two applications of radiofrequency energy (RF) of less than 10 seconds within the CS at the earliest ventricular site (20 msec before the delta wave) failed to abolish the accessory pathway. Then, the ablation catheter was placed retrograde through the aorta at the posterolateral mitral annulus. At this location, the ventricular electrograms on the ablation catheter preceded the delta wave by 40 ms, the unipolar electrograms showed rapid and deep QS, and there was a possible accessory pathway potential (Figure 1D). One application of RF (temperature = 55º, power = 50 watts) at this site in temperature control mode abolished cardiac preexcitation within two seconds. Notice the close proximity between the failed ablation site within the coronary sinus (epicardial) and the successful endocardial site along the ventricular side of the mitral annulus (Figure 2).

Successful ablation of WPW in the presence of PLSVC has been reported from within the CS, trans-aortic and via transseptal approach.^1,2

When the CS is very dilated and there is absence of the right SVC, trannseptal puncture may be challenging and intracardiac echocardiography is recommended.

Persistent Left Superior Vena Cava 

Though PLSVC is the most common congenital anomaly of the thoracic systemic venous return, its true prevalence is unknown because the vast majority of the cases are asymptomatic. It has been reported to occur in the general population in 0.3%–0.5% and up to 12% if another congenital heart abnormality is present.³ The most common associated congenital heart abnormality is atrial septal defect followed by aortic coartaction.^4-6

Contrary to this case, there is frequently a right SVC (80%–90%) when a PLSVC is identified (Figure 3).⁷ In the instance of bilateral SVC, the left innominate vein is usually absent (Figure 3). The PLSVC (80%) drains into the RA via the coronary sinus in 80% without hemodynamic consequences. In 10%–20%, the PLSVC can drain via the left atrium (cardiac shunt) through an unroofed coronary sinus (Figure 3), directly into the LA or through the left superior pulmonary vein.^5-7

WPW and PLSVC

Chiang et al⁸ reported that major CS abnormalities were found more frequently in patients with accessory pathways than in patients with AV nodal reentrant tachycardia. The authors further suggested that the presence of an accessory pathway in the event of PLSVC was not a random event but could be explained by a common embryogenic development. Embryologically, failure of the left superior cardinal vein to regress, i.e., the ligament of Marshall, results in PLSVC. In the same fashion, accessory pathways may result from failure of resorption of the myocardial syncytium at the annulus fibrosis of the atrioventricular valves during fetal development.

PLSVC and Atrial Fibrillation

The association between WPW and AF is well known, although the underlying basic mechanism is not totally understood. Up to 30% of patients with WPW developed AF,⁸ perhaps due to retrograde conduction to the atrium at a time when it is vulnerable to the development of AF.

In this case report, I only performed catheter ablation of WPW, and no more AF has been documented at five-month follow-up.

The PLSVC could potentially be the cause for this patient’s AF episodes. Ectopic beats from the CS, ligament of Marshall have been reported as triggers for AF. Wissner et al⁹ reported that in patients with PLSVC referred for catheter ablation of AF (without an accessory pathway), electrical isolation of the pulmonary veins (PVs) was not enough and isolation of the PLSVC was required. They also reported that isolation of the PLSVC was a cumbersome task, only effective when its mid portion was targeted and it was associated with an increase in major procedural complications. Therefore, it seems reasonable that when AF is documented in WPW patients with PLSVC to only target the accessory pathway as a first-line approach.

Summary

PLSVC is the most frequent congenital thoracic vein abnormality. It is critical to recognize its presence during attempted catheter placement in the heart. PLSVC is suspected where there is dilation of the CS in the absence of a cause for elevated right atrial pressure. Mapping and ablation of an accessory pathway in patients with PLSVC follows the same general electrophysiology principles applicable to patients without anomalous venous return. n

Disclosures: Dr. Navarrete is a consultant for St. Jude Medical. Dr. Janeira has nothing to declare. 

References

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