An atypical journey during a "typical" EP case.

Introduction

Some congenital heart disease lesions go undetected until adulthood. We present a case of a “routine” premature ventricular contraction (PVC) ablation that turned out to have heterotaxy syndrome with an interrupted inferior vena cava (IVC) that was unknown to us at the time of presentation.

Case report

A 60-year-old man with a history of diabetes, hypertension, dyslipidemia, and severe cardiomyopathy (ejection fraction 20%–25%) out of proportion to his coronary artery disease presented to the electrophysiology laboratory for catheter ablation of frequent symptomatic monomorphic PVCs (Figure 1A) after a Holter monitor showed 12.5% PVC burden. Following femoral venous cannulation, catheters were advanced to the level of the right atrium (RA) but no intracardiac electrograms were visualized. Hand-injection venogram elucidated circuitous vasculature with absence of a suprahepatic IVC-to-RA connection. Instead, the IVC continued into the azygos vein, ultimately draining into the RA via the superior vena cava (SVC) (Video 1, available online, and Figure 1B). Using long support sheaths, catheters were successfully advanced superiorly toward the SVC and then inferiorly into the right atrium and right ventricle (Figure 1C and D). Activation and pace mapping (Figures 1E and F) confirmed the PVC origin along the mid-right ventricular septum. After successful ablation, repeat Holter monitor revealed elimination of the PVCs and the patient’s symptoms resolved. Follow-up computed tomography scan (Figure 2A–D) showed situs ambiguous with levocardia, left atrial isomerism, bilateral hyparterial bronchi, polysplenism, abdominal situs inversus, and interrupted IVC with hemiazygos to azygos vein continuation, all consistent with heterotaxy syndrome. No other cardiac anomalies were noted in our patient.

Figure 1

A: A 12-lead electrocardiogram showing premature ventricular contraction morphology. B: Fluoroscopy (anteroposterior view) at the level of the cardiac silhouette after hand-injection of contrast with multipolar catheters in the venous system, showing hemiazygos-to-azygos connection, lack of suprahepatic inferior vena cava–to–right atrium (RA) connection, and contrast flow superiorly via azygos vein to the superior vena cava (SVC). Fluoroscopy in C: right anterior oblique (RAO) 30° and D: left anterior oblique (LAO) 34° showing the circuitous course of the multipolar coronary sinus catheter and the 4 mm ablation catheter positioned at the successful ablation site along the mid-right ventricular septum. The successful site identified by E: activation mapping showing the earliest site of activation (*) and F: nearly identical pace mapping. RV = right ventricle.

Figure 2

A: Cross-sectional computed tomography imaging shows abdominal situs inversus with “left-sided inferior vena cava” (IVC) (hemiazygos vein), left-sided liver, and polysplenia. B: Hemiazygos to azygos vein continuation. C: Azygos vein to superior vena cava (SVC) connection. D: Coronal view showing “left-sided IVC” (hemiazygos) to azygos vein continuation.

Discussion

Interrupted IVC is often associated with congenital cardiac anomalies, the most common of which is heterotaxy syndrome. Heterotaxy syndrome is an abnormal arrangement of the thoracoabdominal organs, commonly categorized as being associated with right versus left atrial isomerism. Frequent PVCs are not necessarily associated with this anomaly but other cardiac and electrophysiologic abnormalities can be. Heterotaxy with right atrial isomerism, known as asplenia syndrome, is characterized by duplication of right-sided structures and absence of left-sided structures. As such, there are bilateral right atrial appendages and bilateral trilobed lungs with bronchi that branch over the pulmonary arteries (eparterial bronchi) and absence of the spleen, rendering these patients immunocompromised and at risk of sepsis. Because of the bilateral morphologic right atria, this type of isomerism is often associated with bilateral SVCs, 2 distinct sinoatrial nodes presenting with competing “sinus” rhythms with an alternating P-wave axis corresponding to their respective atria and absence of the coronary sinus. In left atrial isomerism, known as polysplenia syndrome, there is duplication of the left-sided structures resulting in bilateral morphologic left atria and thus lack of an RA-to-IVC connection, resulting in an interrupted IVC, as seen in our patient. Additionally, the sinoatrial node is commonly dysplastic or inferiorly displaced, manifesting as slow atrial “sinus” rhythm or junctional escape rhythm. Patients with left atrial isomerism also have 2 morphologic left lungs (bilateral bilobed lungs) with bronchi that branch under the pulmonary arteries (hyparterial bronchi). Both types of isomerism have increased risk of pulmonary infections thought to be related to ciliary dysfunction.

As it relates to our case, the interrupted IVC with continuation via the azygos vein to the SVC presented a significant anatomic challenge, as catheter manipulation in this orientation can be difficult. Utilizing long support sheaths, we were able to successfully navigate the ablation catheter to the site of earliest activation that correlated with a nearly identical pace map and ultimately ablate the origin of the PVCs.

Conclusion

Early recognition of anatomic abnormalities and adaptability are key characteristics of the successful electrophysiologist, even when approaching a seemingly “routine” case.

Acknowledgments

The authors would like to thank Sally Ramon-English, administrative assistant, for her help with graphic design and manuscript preparation.

KEY TEACHING POINTS

• Interrupted inferior vena cava (IVC) is often associated with congenital cardiac anomalies, the most common of which is heterotaxy syndrome. • Heterotaxy syndrome is associated with various cardiac and noncardiac anomalies. The finding of interrupted IVC warrants further investigation. • Performing an electrophysiology study and intracardiac ablation may still be possible from the standard femoral vein approach despite the finding of interrupted IVC.