The Impact of Short or Long Transcatheter Occluder Waist Lengths on Postprocedure Complete Atrioventricular Block: A Retrospective Study

Abstract: Background. Complete atrioventricular block (cAVB) is considered the most serious adverse event after transcatheter closure of ventricular septal defect (VSD). Objectives. To evaluate the incidence of postprocedure cAVB and its relationship with different waist lengths of transcatheter occluders. Methods. This is a retrospective study of patients with VSD who had been treated with transcatheter closure at the Shanghai Changhai Hospital from December 2001 to December 2010. Patients were treated with short-waist (n = 234) or long-waist occluders (n = 571). All patients were monitored by electrocardiogram (ECG) within 7 days post procedure. Results. Nine patients (3.8%) treated with short-waist occluders suffered from cAVB and 3 patients (1.3%) required permanent pacemaker implantation, compared with 4 patients (0.7%) and 1 patient (0.2%), respectively, in the long-waist occluder group (P<.001). There was a significantly higher incidence of postprocedure incomplete right bundle branch block (IRBBB) in patients treated with short-waist occluders compared with patients treated with long-waist occluders. There were no significant differences in other procedure-related complications between the two groups. Conclusions. Long-waist VSD occluders are beneficial in the prevention of cAVB and the need for pacemaker implantation after transcatheter closure of VSD.

J INVASIVE CARDIOL 2015;27(11):E231-E235

Key words: congenital heart disease, CHD, transcatheter occluder waist length, ventricular septal defect, VSD

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Ventricular septal defect (VSD) is one of the most common congenital heart anomalies and accounts for approximately 40% of all congenital heart diseases.¹ Conventional surgical repair is a cornerstone treatment for VSD.^2,3 In the past 15 years, transcatheter closure, a minimally-invasive procedure, has been explored as an alternative to surgical strategy. Many devices have been designed in order to achieve successful closure of VSD. Since its successful use in muscular VSD by Thanopoulos in 1999, the Amplatzer VSD occluder (AGA Medical Corporation) became the most widely implanted transcatheter VSD closure device.^4-6 In several countries, transcatheter closure for specific types of VSD has become the primary treatment option.^5-7 However, even if high complete closure rates are achieved at 6-12 months, this treatment strategy remains controversial in several large medical centers due to the excessive risk of short-term and long-term complications, including heart valve injury, thromboembolic events, and complete atrioventricular block (cAVB).⁸ 

cAVB is considered to be the most serious postprocedure adverse event and requires close monitoring.^9,10 Recent studies showed that the risk of cAVB associated with transcatheter closure was approximately 1%-6%, with the highest reaching 22%.^6,11-14 More importantly, the rate of device-related cAVB requiring pacemaker implantation has been reported to be as high as 2.0-5.7%.^6,11-14 

Despite improvements of transcatheter closure of VSD, postoperative complications remain a major challenge for interventional cardiologists worldwide. It has previously been shown that the majority of patients with cAVB can recover to sinus rhythm; however, some patients require permanent pacemaker implantation.^{6,11-13,15,16} Such findings indicate an urgent need for studies to identify the risk factors associated with cAVB in order to reduce mortality after VSD transcatheter closure.^8,17

The successful closure of perimembranous VSD (pmVSD) using a modified double-disc VSD occluder (MDVO) device, (Shanghai Shape Memory Alloy) was reported in 2002.¹⁸ At our center, MDVO devices with two different waist lengths were used between 2001 and 2010 for VSD transcatheter closure. Short waist-length occluders (2-2.5 mm) were originally used, but postprocedure conduction abnormalities, such as cAVB, were observed. Consequently, the waist length was adjusted to 3 mm in 2005, and fewer cases of cAVB were observed. Therefore, it was hypothesized that postoperative cAVB may be associated with the length of the waist of the transcatheter occluder. Therefore, the aim of the present study was to evaluate the incidence of postprocedure cAVB and its relationship with different MDVO waist lengths.

Methods

Patients. In this retrospective study, patients suffering from pmVSD and who were candidates for transcatheter closure according to transthoracic echocardiographic (TTE) screening were included. These patients were treated at the Department of Cardiovasology, Changhai Hospital, Second Military Medical University in Shanghai, China from December 2001 to December 2010. Inclusion criteria were: (1) hemodynamically significant congenital pmVSD, QP/QS >1.5; (2) body weight >10 kg and age >3 years; (3) VSD diameter >4 mm and <14 mm as determined by TTE; (4) defect located at the 9-12 o’clock positions of an analog clock in the short-axis parasternal view by TTE; (5) distance of >2 mm from the pmVSD to the aortic valve and >2 mm from the pmVSD to the tricuspid valve without right aortic coronary valve casting into the VSD and aortic valve regurgitation; (6) left-to-right shunt; and (7) calculated pulmonary vascular resistance <8 Wood units. Exclusion criterion was: other cardiac lesions requiring a surgical approach. 

Transcatheter occluders. MDVOs (Shanghai Shape Memory Alloy, Ltd) were used in the present study, as previously described.⁷ The MDVO devices are currently available in sizes ranging from 4-20 mm. The occluder’s right disk diameter is limited to 4 mm, while the left disk diameter is limited to 4 mm (A2B2; A for left ventricular disk, B for right ventricular disk), 6 mm (A3B2), or 8 mm (A4B2) larger than that of the waist. In the current study, the waist length of both the A2B2 and A3B2 occluders was 2 mm (between 2001 and 2005) and 3 mm (from 2005 to present), while the waist length of the A4B2 occluder was 2.5 mm (between 2001 and 2005) and 3.5 mm (from 2005 to present) (Figure 1). 

Transcatheter closure. In patients older than 10 years, the transcatheter procedure was performed under local anesthesia (lidocaine). In patients younger than 10 years, general anesthesia was administered. In both groups, MVDOs were placed retrogradely via transvenous access, as previously described.¹⁹ In particular, size, location, shape of the VSD, and the relationship of the VSD to the adjacent aortic valve were assessed by TTE prior to the procedure and confirmed by angiography during procedure. Left ventricular angiography was performed at 45°-60° in the left anterior oblique position and 25° cranial tilt using a pig tail catheter. The inlet diameter of the VSD and the maximum outlet diameter were measured. In addition, a femoral artery-vein loop was established. Using the loop wire, a 6-10 Fr delivery sheath was advanced to the left ventricle via the femoral vein. The left ventricular disc was released first. After confirming that the left ventricular disc was attached to the left ventricular side, the right ventricular disc was released. Once the auscultation murmur disappeared, left ventricular angiography was performed once again to verify closure. Following ultrasonic cardiogram (UCG) confirmation of VSD closure and no obstruction of tricuspid and aortic valve function by the occluder, the occluder was released. If cAVB, inadequate VSD closure, or valve interference were observed during the procedure, transcatheter procedure was terminated and surgical repair was considered.

Postoperative management. Following the transcatheter procedure, all patients had routine prophylactic antibiotics for 1 day and oral aspirin 3-5 mg/kg once daily for 3 months. If a heart block was observed, 5 mg of dexamethasone was administered intravenously twice daily for 7 days. All patients underwent electrocardiographic monitoring for 7 days.  

Statistical analysis. Continuous variables are presented as means ± standard deviations. Categorical variables are presented as frequencies and/or percentages. Age is presented as median and range, and the Wilcoxon signed rank test was used. Analysis of variance (ANOVA) was performed for continuous data. The Pearson Chi-square test was used to analyze categorical data. SPSS version 19.0 for Windows (SPSS, Inc) was used for statistical analysis. P-values ≤.05 were considered significant.

Results

Patient baseline characteristics. A total of 819 patients (413 males and 406 females) who underwent VSD closure between 2001 and 2010 were eligible for the present study. Among them, 236 were treated with short-waist occluders and 583 were treated with long-waist occluders. Due to some cases missing patient data, 805 patients who underwent VSD closure were finally included (234 with short-waist occluders and 571 with long-waist occluders). All procedures were successful, with an immediate success rate of 98.3% (Table 1). The baseline characteristics (age, gender, body weight, pulmonary pressure, and combined procedures) were not significantly different between the two groups (P>.05). 

Procedure and occluders used in the study. There were no significant differences between the two groups for the time of interventional digital subtraction angiography (DSA) and the total time required for the procedure. In addition, the VSD diameter, as measured by left ventriculography and TTE, was similar between the two groups. Furthermore, there was no significant difference between the two groups in the types of MDVO used (Table 2).

Postprocedure heart blocks. Significantly more patients (23.1%) treated with short-waist devices had postprocedure blocks compared with patients treated with long-waist devices (14.0%; P<.001). Incomplete right bundle branch block (IRBBB), left anterior bundle branch block (LABBB), complete left bundle branch block (CLBBB), complete right bundle branch block (CRBBB), junction tachycardia, and cAVB (Table 3) were observed. Significantly higher incidence of IRBBB occurred in patients treated with short-waist length devices compared with those treated with long-waist length devices (P=.02). 

In the short-waist group, 9 patients (3.8%) suffered from cAVB, including 2 patients younger than 10 years of age. These patients underwent medical management and a temporary pacemaker was implanted during the patients’ hospital stay. Of these 9 patients, 6 recovered their sinus rhythm in 3-14 days. The remaining 3 patients (1.3%) did not recover and required permanent pacemaker implantation. Among the patients treated with long-waist devices, significantly fewer patients experienced cAVB (4 patients, 0.7%, P<.001). All patients who suffered from cAVB were older than 10 years of age. Of these, 3 of the 4 patients recovered their sinus rhythm within 2 weeks of medical management; 1 patient needed permanent pacemaker placement.

Procedure-related complications. Table 4 presents the postprocedure complications. In the short-waist group, the incidence of complications such as hemolysis, groin hematoma, residual shunt, and valve regurgitation was 21.4% (50 patients), compared with 27.2% (155 patients) in patients treated with long-waist devices, without difference between the two groups (P=.09). Hematoma and hemolysis were medically managed with success. Twenty-one patients (9.0%) treated with short-waist occluders suffered from minor or minimal new-onset valve regurgitation compared with 64 patients (11.2%) treated with long-waist occluders (P=.38). Trivial or small residual shunts were observed in 22 patients (9.4%) in the short-waist group and 72 patients (12.6%) in the long-waist group. 

Discussion

In the present study, a total of 805 patients who underwent transcatheter closure from 2001 to 2010 were compared according to the waist length of occluder devices used to treat VSD. In patients treated with long-waist occluders, the incidence of cAVB was 0.7%, and only 1 out of 571 patients (0.2%) treated with a long-waist occluder required permanent pacemaker implantation. Interestingly, the incidence of procedure-related arrhythmias and cAVB was significantly less in patients treated with long-waist devices compared with patients treated with short-waist devices. 

In the present study, the immediate procedure success rate was 98.3%, which was relatively high compared with previous studies that had smaller sample sizes and used the Amplatzer occluder.^15,16,20 One of the reasons for this high success rate might be the use of the new MDVO device. The MDVO device used in the present study was a nitinol wire mesh covered with a polyester fabric. Different MDVO device sizes were used in the current study to ensure individualized transcatheter closure.  

The exact mechanism of increased risk for cAVB after transcatheter closure remains unknown. It is currently believed that cAVB may be related to inflammatory edema of tissues in the membranous interventricular septum.^11-14 It is possible that the compression, friction, and traction between the memory alloy of the VSD occluder device and conduction branches within the membranous interventricular septum may lead to increased tension, eventually resulting in rhythm or conduction abnormality, or even cAVB.^21-24 Like the bundle of His, the left and right bundle branches are in close vicinity of the membranous interventricular septum. Therefore, cardiac tissue inflammatory edema and compression caused by the occluder waist and rim may affect the conduction of these branches or even cause a certain degree of damage, leading to arrhythmia. In addition, other risk factors for cAVB after transcatheter closure have been reported, including large VSD, low body weight, and Down’s syndrome.^{8,15-18,25,26} In an attempt to reduce the potential pressure and damage caused by a transcatheter closure device, a revised pmVSO2 device was recently designed and tested by Bass and Gruenstein.²⁷ In an animal model, this novel device achieved 75% radial force reduction and 45% clamping force reduction.²⁷ This modified pmVSO2 was successfully implanted in 2 patients. At 7 days and 4 weeks of follow-up, no adverse events were reported.²⁸ Clinical studies are currently investigating this modified device in a large patient population. It is important to note that this modified pmVSO2 device is similar to the long-waist device used in the present study.

The frequencies of cAVB and pacemaker observed in the present study are lower than in previous studies,^6,9,10,14 but this may be due to the short follow-up period that was available for analysis since these previous studies followed patients for as long as 39 months. Indeed, many complications after VSD may appear in the long term.^6,9,10,14

Several studies using the first generation Amplatzer occluder support the findings of the present study.⁵ In a study in 23 European tertiary referral medical centers, Carminati et al reported a rate of cAVB of 5% in 250 patients suffering from pmVSD and who were treated with Amplatzer VSD devices.¹⁵ In a report by Holzer et al of 100 patients who underwent an attempt of percutaneous pmVSD closure using the Amplatzer VSD devices in 24 international centers between April 2002 and August 2004, a total of 4 patients (4%) suffered from transient cAVB. cAVB requiring permanent pacemaker implantation occurred in 2 patients (2%).²⁰ Furthermore, in a recent single-center study of 301 VSD patients using Amplatzer VSD devices, cAVB occurred in 5.78% of patients, with 88% presenting with early cAVB.²⁹ Compared with the short-waist group included in the present study (2 mm waist length occluders), the cAVB rates associated with 1.5 mm waist length Amplatzer VSD devices were similar. These data, in combination with the results of the current study, confirm the hypothesis that the occluder’s structure, in particular the waist length, may be related to the occurrence of postprocedure heart block.

Study limitations. The present study has several limitations. Because the hypothesis for the present study was developed following observation of an increased incidence of postprocedure complications in patients treated with short-waist occluders, this study was a non-randomized, retrospective study. Consequently, several measurements were not included in the study, such as atrial and ventricular sizes before and after treatment, the amount of the residual shunt, and cardiac function. In addition, the electrocardiographic follow-up that was available for analysis was very short. Further prospective trials with longer follow-up are needed.

Conclusion

A longer waist length MDVO is associated with lower incidences of postprocedure cAVB and pacemaker implantation. It is possible that the optimal waist length of 3 mm may result in less septal movement restriction, decreased inflammatory edema, and reduced compression caused by the occluder waist. Additional clinical studies are required to confirm the results of the present study.

Acknowledgments. The authors would like to thank Mr Gong Shanshi for his assistance in the development of our transcatheter closure program, as well as Wang Ersong, MD, and Xiong Wenfeng, MD, for their expertise and assistance with TTE. In addition, we would like to acknowledge the hard work and dedication of the staff and fellows of our Cardiac Catheterization Laboratory at Changhai  Hospital.

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^*Joint first authors.

From the Department of Cardiology, Changhai Hospital, Second Military Medical University, Shanghai, People’s Republic of China.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted June 26, 2014, provisional acceptance given  September 4, 2014, final version accepted November 24, 2014.

Address for correspondence: Hong Wu, MD, Department of Cardiology, Changhai Hospital, Second Military Medical University, Shanghai, 200433, P.R.China. Email: wuhong021398853@163.com