Late Complete Heart Block in an Adult Patient undergoing<br />
Percutaneous Ventricular Septal Defect Closure

Transcatheter closure of ventricular septal defects has emerged as an attractive therapeutic modality, with excellent procedural and intermediate hemodynamic outcomes. While experience with this technique is relatively limited, longerterm follow up in the pediatric population has demonstrated an incidence of complete heart block both acutely and in late follow up.^1,2 Transient disturbances of heart rhythm are common at, or shortly after, the time of device implantation, however, complete heart block remains a late sequela previously documented only in the pediatric population.³
We describe a case of late complete heart block occurring in a 37-year-old female patient who had previously undergone successful percutaneous closure of both a perimembranous ventricular septal defect (VSD) and a secundum atrial septal defect (ASD), and subsequently developed complete heart block 7 months after the procedure. The risk factors, potential mechanisms and treatment of conduction abnormalities complicating percutaneous device closure of ventricular septal defects are discussed.

Case Report. A 37-year-old female patient was referred for consideration of percutaneous device closure of both an ASD and a VSD. The patient had a background of type 2 hereditary hemorrhagic telangiectasia (HHT) and associated pulmonary hypertension. Cardiac catheterization confirmed elevated pulmonary artery pressures as well as a significant left-to-right shunt (Qp:Qs > 1.5:1). Cardiac magnetic resonance imaging demonstrated right ventricular dilatation, with evidence of mild right ventricular hypertrophy. Endothelin antagonist therapy with bosentan resulted in improvement in functional capacity as well as a satisfactory decline in pulmonary artery pressure. Cardiac catheterization confirmed a mean pulmonary artery pressure of 28 mmHg, thus permitting intracardiac defect closure with a low risk of precipitating right-heart failure. Imaging with both transthoracic and transesophageal echocardiography demonstrated a secundum ASD and an aneurysmal perimembranous VSD. Both intracardiac defects appeared suitable for percutaneous device closure, with device closure performed to preserve the pulmonary vasculature and to prevent subsequent worsening of pulmonary hypertension complicating persistent left-to-right intracardiac shunting. As both defects appeared suitable for transcatheter closure, with a similar anticipated hemodynamic result, a percutaneous approach was therefore utilized in favor of a surgical approach.

The procedure was performed under general anesthesia, with the patient administered intravenous heparin and cephazolin antibiotic prophylaxis. Right femoral arterial and venous access was obtained. The secundum atrial defect was successfully closed with a 22 mm Amplatzer ASD occlusion device, with the defect size previously sized to 20 mm by using standard techniques. Left ventriculography demonstrated an aneurysmal perimembranous VSD, with evidence of multiple fenestrations (Figure 1A). A 6 Fr JR4 diagnostic catheter was successfully passed through the aortic valve and positioned across the VSD. After creation of an arteriovenous loop, an 8 Fr AGA delivery system (AGA Medical Corp., Golden Valley, Minnesota) was advanced into the left ventricle. An Amplatzer 25 mm Cribiform^™ ASD device (AGA Medical) was selected given the fenestrated appearance of the defect, and implanted within the aneurysmal portion of the interventricular septum (Figure 1B). The left-sided disc was initially released and retracted toward the defect. The device was then successfully deployed with no significant residual leak noted. The procedure was well tolerated, with the postprocedure electrocardiogram (ECG) demonstrating sinus rhythm, right ventricular hypertrophy and right bundle-branch block (QRS duration 116 msec), which was unchanged from her preprocedural ECG (Figures 2A and B).

At follow up 2 months after the procedure, the patient was well, noting an improvement in exercise capacity, with echocardiography confirming satisfactory device placement, no residual intracardiac shunting and normal biventricular function. An ECG at that time demonstrated sinus rhythm with borderline prolongation of the PR interval (206 msec), right ventricular hypertrophy and persistent right bundlebranch block with an unchanged QRS duration (Figure 2C).
The patient was admitted to the hospital 7 months later with presyncope. An ECG demonstrated marked sinus bradycardia, first-degree heart block (PR interval 233 msec) and right bundlebranch block with QRS prolongation (QRS duration 142 msec). Telemetry monitoring demonstrated the presence of complete heart block, with nonconducted P waves (Figures 3A and B).
The patient subsequently underwent endocardial pacemaker insertion from a right subclavian vein approach and was discharged without further complication.

Discussion. We describe a unique case of a patient with hereditary hemorrhagic telangiectasia undergoing simultaneous percutaneous device closure of both an atrial and ventricular septal defect. While pulmonary hypertension is associated with type 2 HHT, congenital heart defects and conduction system abnormalities have not been previously described in association with HHT. In this case, the postprocedural course following simultaneous ASD and VSD closure was complicated by late onset of complete heart block.
Transcatheter closure of both muscular and perimembranous VSDs has been shown in several series to offer excellent procedural and intermediate-term hemodynamic outcomes.^1,4,5 Acute procedural complications include device embolization, conduction system abnormalities and left-sided valvular regurgitation. Late complete heart block complicating this procedure has been described in the pediatric population,³ with an incidence of 0.8% in large series;² our case demonstrates that this issue is not unique to the pediatric population.
The development of transient cardiac rhythm abnormalities has been well-described following percutaneous VSD closure, including complete heart block, left bundle-branch block and right bundle-branch block.¹ It is believed to be a consequence of the proximity of the conducting system to the site of device deployment, with mechanical irritation immediately after implantation precipitating conduction delay. The development of heart block during the procedure has been used as an indication to abandon attempts to deliver the device percutaneously.⁶ Care should be taken during creation of the arteriovenous loop, and a kissing catheter technique used, to prevent wire injury to the septum adjacent to the defect.⁴ Aside from the development of rhythm disturbance during the procedure and difficulty in positioning catheters across the defect,⁷ no other risk factors for subsequent heart block have been identified. Oversizing of the VSD occlusion device has been identified as a possible contributing factor,⁶ but this does not appear to be present in all cases. Indeed, complete heart block may complicate an apparently successful procedure. Complete heart block that develops acutely following device implantation has been successfully treated in the acute setting with corticosteroid and aspirin therapy.⁷
The occurrence of late complete heart block up to 12 months after closure of perimembranous defects has been observed in previous series.³ These described cases have occurred exclusively in the pediatric population, with none of the reported cases complicating device closure in adult patients. The mechanism of late complete heart block is unclear; it may be the consequence of scarring adjacent to the device, and therefore may be less likely to improve with corticosteroid therapy than complete heart block seen early after the procedure. In one example, there were transient conducting system abnormalities following the procedure, with development of both a transient left bundlebranch block and a junctional rhythm, which resolved with no persisting evidence of conducting system disease. The authors conclude that these arrhythmias may reflect inflammation in the area of the atrioventricular (AV) node. Such immediate postprocedural arrhythmias are not universal, however, and alternate mechanisms postulated include device movement following apparently successful closure.
In our case, the use of an ASD Cribiform occlusion device may have contributed to conducting system injury; ASD occlusion devices have been used successfully to treat ventricular defects, particularly in the setting of a thin ventricular septum, which allows for normal device shape after deployment.⁸ The greater diameter of the left- and right-sided discs, when compared to perimembranous VSD occlusion devices, may have predisposed the patient to a more extensive area of inflammation and subsequent scarring. Positioning of device within the aneurysmal component of the defect, as in our case, has been previously described and has the advantage of avoiding aortic valve injury.⁹ Furthermore, the use of a Cribiform device in a fenestrated defect avoided the complication of oversizing, which has been described in patients with this type of VSD morphology,¹⁰ and may contribute to the risk of acute complete heart block after the procedure.⁶ Previouslyreported cases of complete heart block have not been described as using an aneurysmal component of the VSD for defect closure. While the use of transcatheter techniques to close both ASDs and VSDs is now well established, the use of percutaneous methods to close both defects in the same patient is certainly unique, and it is therefore difficult to comment on any increased risk of complications using this approach. Transient disturbance of heart rhythm has been described after percutaneous closure of an ASD using the Amplatzer septal occluder,¹¹ however, atrial tachyarrhythmia during follow up is a more likely procedural complication of ASD closure.¹² The presence of preexisting conduction abnormalities in older patients could be anticipated to confer an increased risk of subsequent heart block, however, both prior to and 2 months after the procedure, there was no evidence of significant atrioventricular conduction delay in this patient.
Late heart block after VSD closure clearly remains a recognized complication of both surgical and percutaneous approaches13 and does not appear to be exclusive to the developing conducting system of the pediatric patient. Thus, complete heart block remains an important issue in the follow up of both adult and pediatric patients undergoing transcatheter device closure of a perimembranous VSD. Interventional cardiologists and their patients must be aware of the potential of this late complication, even after apparently successful procedures. Long-term follow up is required to identify patientand device-related risk factors for late heart block, which may direct more intensive monitoring late after percutaneous device deployment.

References

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