Abnormal venous return: Still a challenge for electrophysiology procedures? A case report

Abstract

Catheter ablation of cardiac arrhythmias is usually performed through the femoral venous approach. Systemic venous return anomalies such as interruption of the inferior vena cava may represent a challenge during electrophysiological procedures.

A 55-year-old patient with previous surgical correction of abnormal pulmonary venous return was admitted for poorly tolerated atrial flutter recurrences. He also had an interrupted inferior vena cava continuing as azygos vein and left superior vena cava draining via coronary sinus into the right atrium. Cavotricuspid isthmus radiofrequency ablation was successfully performed through the persistent left superior vena cava using a three-dimensional (3D) electroanatomical mapping system.

Despite systemic venous abnormalities may potentially have important implications during electrophysiological procedures, arrhythmias can be successfully ablated with the aid of 3D electroanatomical mapping systems.

<Learning objective: Congenital venous return anomalies can represent significant difficulties in accessing catheters to the cardiac chambers during electrophysiological procedures, which may be facilitated by three-dimensional mapping systems. Radiofrequency ablation of the cavotricuspid isthmus can be successfully performed using the femoral approach and introducing catheters into the right atrium sequentially through the femoral-iliac venous axis, the azygos vein, the persistent left superior vena cava, and the coronary sinus.>

Introduction

Although rare, abnormal venous return can represent an obstacle to the execution of electrophysiological procedures (EP) especially regarding access to the cardiac chambers and catheter manipulation, considering that catheter ablations of cardiac arrhythmias are usually performed via femoral venous approach.

In this case we report the feasibility of a successful radiofrequency ablation of a cavotricuspid isthmus (CTI) performed by inserting the catheters into the right atrium (RA) through the coronary sinus (CS). Using the femoral venous approach and given the inferior vena cava (IVC) interruption, the catheters were passed sequentially through the right iliac vein, the azygos vein (AzV), and finally the persistent left superior vena cava (PLSVC) in continuity with the CS.

For this purpose, the three-dimensional (3D) electroanatomical mapping system has proved necessary and of inestimable value.

Case report

A 55-year-old male suffered from several weekly recurrences of atrial flutter (AFL) despite therapy with amiodarone (Fig. 1). At the age of 15, he underwent surgical correction of abnormal right pulmonary venous return. In particular, the right pulmonary veins (RPVs) drained into RA and the atrial septum was preserved. The atrial septum was widely rearranged to enlarge the left atrium and allow RPVs to drain into it (Fig. 2F). Through an oblique incision of the RA, a Dacron® velour patch was applied to readdress the antrum of the RPVs and a portion of the original RA into the left atrium. Furthermore, there was an interruption of the IVC, so iliac veins drained into CS through AzV and PLSVC (Fig. 2A). The CS regularly drained into RA, while there was a hypoplastic patent right superior vena cava and a short IVC that drained only hepatic veins. Fig. 2 shows detailed documentation of the anatomy of the patient’s atria and his venous return.

Fig. 1.

Patient’s clinical arrhythmia. 12-lead electrocardiogram shows negative “saw tooth” F waves in all the inferior leads and positive F waves in V1 compatibile with typical common atrial flutter.

Fig. 2.

X-ray, computed tomography (CT) scan, and 3D electroanatomical map: patient’s anatomy overview. (A) Femoral phlebography shows inferior vena cava interruption and iliac vein continuation in azygos vein. The black arrow indicates the small hypoplastic inferior vena cava interrupted at iliac level. The black arrow heads indicate DECANAV and THERMOCOOL SmartTouch catheters that are pushed through right femoral, right iliac and then azygos vein. (B) DECANAV and SmartTouch catheters placed into right atrium once passed through persistent left superior vena cava and coronary sinus. Right lateral view (C), inferior view (D), left anterior oblique view (E) of the right atrium with radiofrequency line of lesion (red dots) created through the entire 6 cm long cavotricuspid isthmus. The red arrow (C, D) points the small inferior vena cava (green colored) that drains only the hepatic veins. The bipolar map (0.05–0.5 mV range) shows normal potentials into the whole right atrium. Few small low voltage areas are visible at the right side of the surgically corrected atrial septum. A transverse CT scan (F) slices both atria at the level of the Dacron Velour patch suture (blue circle). This view allows appreciating the anatomy and relations between the RPVs, LPVs, and left atrium enlarged at the expense of the small right one (red circle). Inferior view (G) and left anterior oblique view (H) showing overlap between 3D CT scan reconstruction of the right atrium (3D yellow shape) and its electroanatomical map. The picture shows electroanatomical reconstruction of the persistent left superior vena cava and coronary sinus (C, D, E, G, H).

Given the numerous recurrences of symptomatic high ventricular rate AFL, the patient was admitted for transcatheter ablation after he had left informed consent to the procedure. In consideration of the presence of a hypoplastic right superior vena cava, a DECANAV® Catheter and a THERMOCOOL SmartTouch® Catheter (Biosense Webster, Inc., Diamond Bar, CA, USA) were sequentially advanced into the RA from the right femoral vein through the AzV, PLSVC, and then CS (Fig. 2B). A 3D electroanatomical map performed with the aid of DECANAV and CARTO 3® mapping system (Biosense Webster, Inc.) surprisingly showed no scar areas in the RA, especially at the atrial septum, at the bipolar substrate map with 0.05–0.5 mV range (Fig. 2C–E). In particular, at the right side of the atrial septum few small low voltage areas were found, but without evidence of signal alterations (e.g. atrial fragmented electrograms) that may represent an arrhythmic substrate. DECANAV catheter was used to create a gross map with a high number of points recorded with the CONFIDENSE™ Module. Then low voltage areas and remaining areas of interest were deeply revaluated with contact-force monitoring using the THERMOCOOL SmartTouch catheter. At the beginning of the procedure, the patient was in sinus rhythm and clinical arrhythmia could not be induced during electrophysiological study (EPS). No other supraventricular arrhythmias were inducible to EPS. In consideration of the documented arrhythmia (Fig. 1), the presence of conduction through the CTI and the absence of a substrate in the RA that could justify a different mechanism of the clinical arrhythmia, we believed that the arrhythmia observed was a typical common AFL although it was not inducible to EPS and we established the CTI bidirectional conduction block as the procedure endpoint. Even though the abnormal venous return was challenging, we decided to perform ablation through the CS. Radiofrequency ablation (35 W in power control) was started on the tricuspid edge and a point by point linear lesion (with target ablation index value: 500) was performed through the entire isthmus which measured almost 6 cm (Fig. 2C–E). The ablation at the junction between RA and IVC was really challenging because the ablation catheter was always falling down into IVC; to this extent bidirectional catheter proved to be very useful. Bidirectional block was confirmed by a marked prolongation of the trans-isthmic conduction time evaluated during stimulation from the low lateral RA wall while recording at CS ostium and vice-versa (Fig. 3). At the end of the procedure, AFL was still not inducible. Whole procedural time was 90 min and fluoroscopic exposure time was almost 3 min. The patient remained free of arrhythmias during 8 months’ follow-up without antiarrhythmic administration.

Fig. 3.

Trans-isthmic conduction block after radiofrequency. The DECANAV (L1-10) catheter is spanning the line of injury created at the level of the cavotricuspid isthmus with 1–2 and 3–4 dipoles laterally to the lesion and 7–8 and 9–10 dipoles medially to the lesion. The THERMOCOOL SmartTouch ablator (Abl) catheter is placed medially to the lesion (near the CS ostium) and the stimulus delivered by it induces a very delayed activation of the portion of the right atrium lateral to the lesion and with a distal to proximal activation sequence (red circle) on DECANAV catheter confirming cavotricuspid isthmus conduction block.

The patient gave informed consent to use in anonymous form his clinical data for scientific purposes.

Discussion

IVC interruption or congenital stenosis are rare in the general population (<0.1%) but their incidence is 0.6% in patients with congenital heart disease (CHD) [1], [2]. The incidence of a PLSVC in those with situs solitus has been reported as 0.3%, but is greater in patients with CHD [3]. Usually, the PLSVC drains into the RA via a dilated CS that may be demonstrated by transthoracic echocardiography [4].

Catheter ablation of cardiac arrhythmias is usually performed via the femoral venous approach. Congenital or acquired abnormalities of the IVC pose technical challenges in accessing the ablation site. Alternative approaches via internal jugular vein, subclavian vein, cephalic vein, and transhepatic have been described [5], [6], [7], [8], [9]. Several case reports describe successful transcatheter ablations and device implants in patients with IVC interruption and PLSVC [10].

We decided to perform the procedure via right femoral vein approach for different reasons. First of all, left subclavian vein was draining in left persistent vena cava, and therefore ultimately the same way we used to access the right atrium. Although catheter manipulation could theoretically have been easier if they had been introduced through the left subclavian vein, we opted for the femoral approach to avoid any complications related to the puncture of the subclavian vein (e.g. pneumothorax). Conversely, right superior venous approach seemed not suitable because superior vena cava was described to be hypoplastic in the report of cardiac surgery performed in the patient’s youth. Such data were confirmed by angiography performed during the procedure through right basilic vein. So, we decided that we would attempt the superior venous approach as a last chance in case of failure with the inferior venous approach. The manipulation of the catheters via the right femoral vein was difficult, because they were extremely bent at the junction between AzV and PLSVC, however not impossible so much so that the procedure was technically completed successfully in 90 min and with just 3 min of fluoroscopy.

This report describes a clinical application of the CARTO 3® as an adjunctive and essential technology to guide the ablation with high accuracy and detail in a complex anatomy. CTI-dependent AFL was treated in a patient with right abnormal pulmonary venous return surgically corrected in childhood, with PLSVC, interruption of the IVC and azygos continuation. In our case, positioning and manipulation of the recording and mapping/ablator catheters were difficult because of abnormal access to the RA through the CS. In this case, the CARTO 3® system improved navigation of the mapping/ablator catheter within the RA and provided better accuracy of radiofrequency delivery in order to ensure optimal lesions despite the complex anatomy. This approach allows fluoroscopic exposure reduction for both the patient and the operator and at the same time improves the safety and efficacy of the procedure. DECANAV® was essential to facilitate a rapid and accurate electroanatomic reconstruction of the RA. The greatest difficulty was represented by obtaining a good stability of THERMOCOOL SmartTouch® in the CTI area facing the caval edge. In this setting, the 3D mapping system and, particularly, continuous contact force monitoring allowed us achieving and maintaining correct ablation sites and thus performing a successful CTI block.

Although we had not demonstrated that clinical arrhythmia was a typical common (i.e. CTI-dependent) AFL since it was not inducible to EPS, the absence of relapses in the 8 months’ follow-up after ablation suggested to us an “ex adiuvantibus” diagnosis of the aforementioned arrhythmia: the patient went from having frequent weekly arrhythmic episodes to being free from recurrences after ablation without the need for antiarrhythmic drugs.

To the best of our knowledge, this is the first case in which transcatheter ablation of a CTI-dependent AFL was successfully performed in a patient with azygos continuation and PLSVC with access to the RA via CS.

Conclusions

Systemic venous abnormalities may have important implications during EP procedures and device implantation. They occur frequently in patients with CHD and, if not already known, they may prolong procedural time, enlarge radiation exposure, and increase rates of complication and failure. Arrhythmias in the presence of such venous abnormalities could be successfully ablated with the aid of 3D electroanatomical mapping. Therefore, an adequate pre-procedural planning is mandatory.

Conflict of interests

On behalf of all authors, the corresponding author states that there is no conflict of interest.

Funding

No funding has been received for manuscript preparation and publication.