A Rare Case of a Common Inferior Pulmonary Vein Presumed to Be a Remnant of the Common Pulmonary Vein

Abstract

A 74-year-old woman with an implanted physiological DDD pacemaker visited our department complaining of palpitations due to atrial fibrillation (AF). Catheter ablation therapy for AF was scheduled. Preoperative multidetector computed tomography showed that the inferior pulmonary vein (PV) was a common trunk, and the left and right superior PVs branched from the center of the left atrial roof. In addition, mapping of the left atrium before AF ablation revealed no potential in either the inferior PV or common trunk. We performed left and right superior PV and posterior wall isolation. After ablation, AF was not observed on pacemaker recordings.

Introduction

Pulmonary vein isolation (PVI) is a useful strategy in radiofrequency catheter ablation (RFCA) for atrial fibrillation (AF) (1). Previously, RFCA of AF using multidetector computed tomography (MDCT) or magnetic resonance imaging (MRI) was shown to be feasible and safe for achieving a favorable outcome, even in patients with an abnormal cardiac anatomy (2,3). At present, these modalities are commonly used to plan and guide AF ablation procedures. However, anatomical variations in pulmonary vein (PV) drainage to the left atrium have been reported using MDCT and MRI (4).

We herein report a rare case of PV malformation with an inferior common trunk that was successfully treated with RFCA.

Case Report

A 74-year-old woman with complete atrioventricular block and a previously implanted physiological DDD pacemaker visited our hospital. Fourteen months after pacemaker implantation, the patient had complained of palpitations, and device interrogation revealed paroxysmal AF. Physical and laboratory examinations revealed no abnormalities. Catheter ablation therapy for paroxysmal AF was planned due to drug ineffectiveness.

Preoperative MDCT depicted the inferior PV as a common trunk, and the left and right superior PVs branched from the center of the left atrial roof (Fig. 1). RFCA was therefore performed under general anesthesia. PVI using RFCA was planned under the guidance of three-dimensional (3D) ultrasound geometries and 3D merged computed tomography using the CARTO 3 system (Biosense Webster, Diamond Bar, USA). Before ablation, the CARTO system was used to establish a detailed 3D electroanatomic voltage map (EVM) of the left atrium during sinus rhythm (Fig. 2). The voltage height was measured as a bipolar peak-to-peak electrogram amplitude, and a voltage range of <0.5 mV was defined as a low-voltage area, while a voltage range of <0.05 mV was defined as the scar area. An EVM of the left atrium obtained before AF ablation revealed no potential in the inferior PVs or inferior common trunk. Intravenous isoproterenol was administered; however, premature atrial contraction, which triggers AF, was not observed in the inferior PVs or inferior common trunk, and not captured by electrical stimulation. In contrast, pacing capture was observed in the low-voltage area below the common trunk of the inferior PV. We performed left and right superior pulmonary vein, bilateral carinas, roof line, bottom line, and posterior wall isolation (Fig. 3).

Figure 1.

Multidetector computed tomography (MDCT) of the left atrium before ablation. A: anterior image, B: posterior image, C: roof image. The inferior pulmonary vein (PV) was a common trunk, and the left and right superior PVs branched from the center of the left atrial roof.

Figure 2.

Three-dimensional (3D) ultrasound geometries and 3D merged computed tomography (CT) using the CARTO 3 system. A: anterior image, B: posterior image, C: roof image. The CARTO system was used to establish a detailed 3D electroanatomic voltage map (EVM) of the left atrium during sinus rhythm. EVM images of the left atrium before ablation showing no electrical potential in either PV. The common inferior trunk, except for a part of the posterior wall, also had no electrical potential.

Figure 3.

Images of an ablation line and electroanatomic mapping of the left atrium after radiofrequency catheter ablation (RFCA). A: anterior image, B: posterior image, C: roof image. We performed left and right superior pulmonary vein (PV) isolation, bilateral carina, roof line, bottom line, and posterior wall isolation.

After ablation, there was no electrical potential around the roof or common trunk of the inferior PVs (Fig. 4). It was no longer possible to induce AF or atrial tachycardia. Despite no antiarrhythmic medication, the patient remained free from AF at the 20-month follow-up.

Figure 4.

No electrical potential around the roof and common trunk of the inferior pulmonary veins (PVs). A: posterior image, B: roof image. After ablation, there was no electrical potential around the roof or common trunk of the inferior PVs.

Discussion

There have been reports of variations in the normal anatomy of PVs. One anomaly reported was a common trunk of the left PVs or separate right PVs (4). Some reports maintain that a common trunk of the inferior PV is a rare anomaly (5). In our case, the patient exhibited a common trunk of the inferior PVs, and the superior PVs were separated from the center of the left atrial roof. In addition, this case had specific electrophysiological features.

Embryologically, when an embryo is around 15 mm in length, lung development begins, and the 4 major PVs meet in the midline posterior to the developing heart to form the common PV. Simultaneously, the common atrium undergoes formation and septation. The common PV fuses with the posterior wall of the left atrium up to the peripheral bifurcation, and four normal pulmonary veins are formed (6,7). The present patient had an inferior common trunk of the PVs with no electrical potential in either the inferior PV or common trunk.

Such an anatomy is attributed to an abnormality in the developmental process of the heart and PVs. Pulmonary venous connections to the cardinal and umbilicovitelline veins normally involute, and the common PV becomes incorporated into the dorsal wall of the left atrium, ultimately giving rise to four separate PVs (8). In the present case, it is believed that the morphology of the PV was inadequate, as the common PV failed to properly incorporate into the dorsal wall of the left atrium. The common PV had no atrial muscle and thus no electrical potential. In this case, the morphological abnormality was probably due to premature cessation of the absorption process of the common PV into the left atrium, which is supported by the absence of potentials in the inferior PV and common trunk. However, the detailed mechanism underlying how the common duct of the inferior pulmonary vein is formed is not yet known.

No marked differences in the long-term efficiency of radiofrequency ablation for AF among different PV anatomies have been reported (9,10). Furthermore, some reports have indicated that cryoballoon ablation is not inferior to radiofrequency ablation in patients with a left common PV (11). Although the majority of previous studies have only discussed PV anomalies with the left common trunk, there have been few case reports of ablation of the common trunk of the inferior PVs. Posterior wall isolation was reportedly useful for suppressing the recurrence of AF, although premature contractions that triggered AF were not observed from the posterior wall (12,13). In the present case, we administered intravenous isoproterenol, but no premature atrial contractions, which trigger AF, were observed. Furthermore, no electrical potential was observed in the inferior PVs or common trunk before ablation. We performed left and right superior PV isolation, followed by isolation of the bilateral carinas and posterior wall. Non-PV triggers of AF have been reported to be more likely to originate within or around low-voltage areas of the left atrium. The arrhythmogenic potential of the inferior common trunk is unclear, with some reports finding that ectopic triggers were not observed within the inferior common trunk or others that were observed (5,14). Substrate modification should be performed for abnormal potentials at the entrance of the common trunk, even if no potential is detected in the PVs or their antrum (15,16).

Although such structural abnormalities of PVs are rare, it is important to perform preoperative MDCT and MRI. Intraoperative electrophysiological studies and voltage mapping are also important in the treatment strategy for rare anatomic abnormalities, such as a common trunk of inferior PVs.

Conclusions

We encountered a case with an uncommon anatomy and electrical characteristics of the left atrium and PVs. It is important to know that, if anatomic abnormalities are present, there may also be electrical abnormalities in the left atrium and PVs. Thus, electroanatomical mapping before the ablation procedure will provide important information to support the catheter ablation strategy.