The Incidence of Transcatheter Aortic Valve Implantation-Related Heart Block in Self-Expandable Medtronic CoreValve and Balloon-Expandable Edwards Valves

Abstract: Background. Transcatheter aortic valve implantation (TAVI) has been performed at Waikato Hospital for high-risk severe symptomatic aortic stenosis patients who are considered unsuitable for conventional cardiac surgery for the last 3 years. The Medtronic CoreValve (MCV) is a self-expandable device, while the Edwards SAPIEN valve (EV) requires the use of a balloon to expand the device. This observational study reports and compares the incidence of heart block in both Medtronic and Edwards transcatheter valves. Methods. All patients who underwent TAVI between the periods of 28 August 2008 and 27 July 2011 were included in this study. Preprocedure and daily postprocedure until discharge electrocardiograms (ECG) were obtained prospectively. New onsets of significant atrioventricular (AV) and bundle branch blocks were recorded. Patients with existing pacemaker and those who did not survive the procedure were excluded. Results. Sixty patients underwent TAVI during the study period, of whom 40 (67%) and 20 (33%) patients had MCV and EV implanted, respectively. Seven patients were excluded from the analysis; 38 MCV and 15 EV patients fulfilled the criteria for analysis. Mean age was 80 ± 7 years, 57% were male. Five patients (9%) required permanent pacemaker (PPM) implantation, which occurred exclusively post MCV TAVI (MCV vs EV: 13% vs 0%, respectively; P=.02). The indications of PPM were complete heart block in 3 patients (60%), Mobitz II second-degree heart block in 1 patient (20%), and symptomatic sick sinus syndrome in 1 patient (20%). The incidence of left bundle branch block (LBBB) was increased after the TAVI procedure and was more significant with MCV implants (MCV vs EV: 42% vs 8%, respectively; P<.01). Of note, 2 of the 5 patients (40%) with pre-existing right bundle branch block (RBBB) who underwent TAVI required PPM (P=.01). Conclusion. MCV implantation is associated with a higher incidence of significant AV block requiring PPM implantation and LBBB compared to EV. The overall rate of PPM requirement post MCV TAVI is, however, lower than previously published data. Pre-existing RBBB may help in predicting the likelihood of developing significant AV block.

J INVASIVE CARDIOL 2012;24(4):173-176

Key words: TAVI, AV block, pacemaker, LBBB, Medtronic CoreValve, Edwards SAPIEN valve

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Transcatheter aortic valve implantation (TAVI) with the Medtronic CoreValve system (MCV; Medtronic) and Edwards SAPIEN (EV; Edwards Lifescience) is an evolving therapeutic option for patients with severe aortic stenosis who are at high risk for conventional aortic valve replacement.^1-4 Atrioventricular (AV) block post TAVI is a recognized complication with the occurrence of significant AV block requiring pacemaker (PPM) implantation up to 6-7 times higher with MCV than in the conventional surgical open-heart aortic valve replacement.^5-9 The objective of this study was to compare and report our local experience on the incidence of heart block and the requirement of permanent pacemaker after TAVI in a tertiary center performing both MCV and EV TAVI.

Methods

Patients. All patients who underwent TAVI receiving a MCV and EV, including transarterial or transapical approaches, from 28 August 2008 to 27 July 2011 were included in the analysis. All patients had 12-lead electrocardiography (ECG) before and daily after the procedure until discharge collected prospectively during the study period. All patients receiving a TAVI gave written informed consent for data collection and analysis and the program was approved by the local ethics committee.

Demographic data, including age, gender, body mass index (BMI), Euroscore, STS (Society of Thoracic Surgeons) score, annular diameter, left ventricular ejection fraction (LVEF) derived by bi-plane Simpson’s method, coronary artery disease (defined as the presence of >50% diameter stenosis in at least one main coronary artery), hypertension, diabetes, and New York Heart Association (NYHA) classes was obtained in all patients.¹⁰

Device studied. The Medtronic-CoreValve is mounted on a self-expandable nitinol frame and comes in sizes of 26 and 29 mm. The Edwards SAPIEN valve, which is available in sizes 23, 26, or 29 mm, is mounted on a stainless-steel or cobalt-chromium balloon-expandable stent. Aortic annulus based on echo was used to determine the size of device implanted. For annuluses measuring 20-23 mm and 24-27 mm, 26 and 29 mm MCV were used, respectively. Twenty-three, 26, and 29 mm EV devices were used in annuluses measuring 18-21 mm, 21-25 mm, and 25-27 mm, respectively. Balloon aortic valvuloplasty was performed before device implantation to facilitate device delivery and prepare the bed for full frame expansion. A 20-25 mm x 4 cm Nucleus balloon (NuMED Inc) was used for MCV and 20-23 mm x 3 cm Edwards balloon (Edwards Lifescience) was used for the EV. MCV was delivered via trans-arterial route in a retrograde fashion through an 18 Fr sheath. The EV was delivered using both transarterial route in a retrograde fashion through a 22 or 24 Fr sheath and transapical route in an antegrade fashion through a 26 Fr sheath.

Exclusion criteria. Patients who did not survive the procedure or who had a pacemaker prior to the procedure were excluded from the final analysis.

Outcomes assessed. The outcomes assessed were AV block, which included first, second, and third degree AV block. The new onset of trifascicular block, defined as coexistence of either first-degree heart block and LBBB or first-degree heart block, anterior or posterior fascicular block, and RBBB, was also assessed. Advanced AV block was defined as Mobitz II second-degree or third-degree block. Guidelines recommend pacemaker implantation with advanced AV block.11 The new onset of bundle branch block, defined as QRS >120 ms, was categorized into either LBBB or RBBB.

Statistical analysis. Statistical analysis was performed with PASW Statistics 18 (SPSS Institute). The continuous variables are presented as mean ± standard deviation. Categorial data were compared with t-test or Fisher’s exact test when appropriate. The incidence of bundle branch block pre- and postprocedure was compared using the McNemar test. A P<.05 was considered significant.

Results

Sixty patients underwent TAVI during the study period, 7 patients were excluded from the analysis due to procedural mortality or pre-existing permanent pacemaker. Of the 53 patients included in the analysis, 38 patients had MCV and 15 patients had EV implanted. There was no significant difference in baseline demographic data in these two groups. Transarterial approach was used in all MCV (100%) and 9 EV patients (60%); 6 of the EV TAVIs (40%) were performed via transapical approach. The results are summarized in Table 1.

Five patients (9%) required PPM implantation post TAVI procedure. The indications of PPM were complete heart block in 3 patients (60%), Mobitz II second-degree heart block in 1 patient (20%) and 1 patient (20%) had symptomatic sick sinus syndrome (Table 2). All 5 patients (5/38; 13%) had MCV implanted. No patient (0/15; 0%) who had EV implantation required PPM.

LBBB was significantly increased post TAVI from 8 (15%) to 22 (42%); P<.01. Interestingly, 1 patient with LBBB developed RBBB post procedure in the MCV group. The incidence of RBBB was not significantly increased post TAVI procedure (P=.62). MCV implantation is associated with significant incidence of new onset of trifascicular block (23%, n = 9; P=.04), this was not observed in the EV group (Table 2). Of the 9 patients who developed new onset of trifascicular block, 8 were due to first-degree heart block and left bundle branch block, none of these patient required PPM during the median follow-up of 21 months. One patient who developed asymptomatic trifascicular block due to first-degree heart block, left anterior fascicular block, and RBBB associated with bradycardia had PPM implantation at 4 months time at another institution for prophylactic reasons.

The comparison between MCV and EV groups revealed that patients in the MCV group received larger devices (28 mm vs 25 mm; P=.04) leading to a device-annulus discrepancy (1.16 ± 0.08 vs 1.09 ± 0.06; P<.01), despite similar aortic annulus size (24 mm vs 23 mm; P=.15) (Table 3). The MCV group was also associated with a higher incidence of LBBB (42% vs 8%; P<.01) and requirement of pacemaker (13% vs 0%; P=.02) (Table 2). The average time for periprocedural pacemaker implantation was 5 days post procedure (range, 2-8 days).

Univariate analysis of the pre-existing electrical abnormality demonstrated a pre-existing RBBB seems to be associated with more frequent post-TAVI PPM requirement (Table 4).

Discussion

TAVI has become an important treatment modality for patients with severe symptomatic aortic stenosis who are at high risk for surgical valve replacement. Until the emergence of TAVI as a therapeutic option, many of these patients were treated medically or with palliative balloon aortic valvuloplasty.¹² 

The reported incidence of significant AV conduction abnormalities after conventional aortic valve replacement requiring PPM is about 3%-6%.^7,8 By contrast, recent studies suggest that TAVI, especially with the self-expanding prosthesis, is associated with significantly higher AV conduction abnormalities and PPM requirement.^6,13-16 The reported PPM requirement for MCV TAVI has varied between 16%-43% in different published registries with an average of 1 in 4 patients requiring pacemaker implantation.^14,15,17-20 PPM requirement, however, in EV TAVI appears to be less frequent, ranging between 4%-7%.^5,21 The need for PPM after TAVI may be influenced by pre-existing conduction abnormalities, procedural factors, which include the depth of device implantation and the length of BAV balloon used, and inter-physician variability in interpreting the actual indication for PPM implantation.^13,22 The large variation in PPM needs post TAVI can in large part be explained by the above factors and by the unadjudicated data reporting in multiple registries.

Our center performs both MCV and EV TAVI and observed the overall pacemaker requirement was lower than previously reported. Of the 38 patients who underwent MCV TAVI, only 5 (13%) required PPM implantation up to 30 days from device implantation and none in the EV group. One possible explanation may relate to implantation techniques with our operators favoring relatively higher implantation of MCV, which may avoid compression of the electrical bundles running below the aortic annular level. This hypothesis we believe is worthy of further investigation. In addition, our operators have a higher threshold for PPM implant with a preference to avoid implantation for trifascicular block caused by first-degree AV block and LBBB. The Australia-New Zealand Medtronic CoreValve Registry reported that the majority of patients who received a PPM (61%) maintained an underlying intrinsic ventricular rhythm at last follow-up and were not fully pacemaker dependent (defined as ≤85% ventricular paced by the device) (Unpublished data: Meredith et al. The Australia-New Zealand Medtronic CoreValve Registry: outcomes in inoperable and high-risk AS patients. Transcatheter Cardiovascular Therapeutics, 2010).

We also noted that the average aortic annular size in both MCV and EV groups appeared to be similar; however, patients who received MCV prosthesis have significantly larger device and device-annulus discrepancies when compared to the EV group (Table 3). This may contribute to a higher incidence of significant AV block requiring PPM implantation.

We observed the incidence of LBBB to be significantly higher after TAVI and that this occurred more frequently in MCV than EV TAVI (42% vs 8%; P<.01), which is in concordance with previously reported data.^{5,13,15,23,24} This is likely due to the dilatation of MCV frame and compression of surrounding structure around the left ventricular outflow tract resulting in the destruction of the left bundle branch. Hence, using a larger device in a smaller annulus, especially implanted low, may influence the appearance of new LBBB. Also, using longer balloons for predilatation may contribute to this, with further assessment of this theory warranted, as the most common ECG abnormality post TAVI is the appearance of a new LBBB. A pre-existing RBBB is likely to influence the need for PPM as shown in our study and by others previously.^13,15 Due to the relative smaller number of patients with pre-existing RBBB in our series, our results should, however, be interpreted with caution. The association of new LBBB after TAVI with long-term left ventricular function and survival is currently unknown.

Study limitations. This is a single-center observational experience. There is no randomization in prosthesis selection and the number of patients treated is small. The data are self-reported with no adjudication. The patients who died postprocedure were excluded, as there were no ECGs to compare. However, none of these patents died from a conduction abnormality.

Conclusion

Our study demonstrated that Medtronic CoreValve implantation is associated with higher degrees of AV block and the need for permanent pacemaker implantation than the Edwards SAPIEN prosthesis. LBBB is also more frequently noted after MCV implantation. 

References

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From the ¹Waikato Hospital, New Zealand, and ²National University Heart Centre, Singapore.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Sanjeevan Pasupati discloses that he is a proctor and a member of the Valve Advisory Board for Medtronic CoreValve. He is a researcher for novel Edwards valve technologies with no financial commitments. No other authors report disclosures.
Manuscript submitted January 18, 2012, provisional acceptance given February 7, 2012, final version accepted February 14, 2012.
Address for correspondence: Dr Sanjeevan Pasupati, Department of Cardiology, Waikato Hospital, Hamilton, New Zealand. Email: drspasupati@gmail.com