Transcatheter aortic valve implantation (TAVI) is a novel treatment for high risk or inoperable patients with symptomatic severe aortic stenosis. However, significant atrioventricular (AV) conduction system abnormalities requiring permanent pacemaker (PPM) implantation might complicate this procedure. We used best subsets logistic regression analysis to identify the independent predictors for the development of high-degree AV block (HDAVB) among 70 patients who underwent TAVI at 3 referral centers in Israel from 2008 to 2010. The mean age of the study patients was 83 ± 4.6 years. Of the 70 patients, 28 (40%) developed AV conduction abnormalities requiring PPM implantation within 14 days (median 2) of the procedure. The indications for PPM implantation were HDAVB (n = 25), new-onset left bundle branch block with PR prolongation (n = 2), and slow atrial fibrillation (n = 1). Best subsets logistic regression analysis showed that, among the 15 prespecified clinical, electrocardiographic, and echocardiographic candidate risk factors, only right bundle branch block at baseline (odds ratio 43; p = 0.002) and deep valve implantation (<6 mm from the lower edge of the noncoronary cusp to the ventricular end of the prosthesis, odds ratio 22; p <0.001) were independently associated with the development of periprocedural HDAVB. At 3 months of follow-up, HDAVB was still present in 40% of the patients who received PPM implantation for this indication. In conclusion, 40% of the patients who undergo CoreValve TAVI require PPM implantation after the procedure, with most cases (36%) associated with the development of postprocedural HDAVB. Baseline conduction abnormalities (right bundle branch block) and deep valve implantation (>6 mm) independently predicted the development of HDAVB and the need for PPM implantation after CoreValve TAVI.
Anatomically, the aortic valve annulus lies very close to the atrioventricular (AV) node and the bundle of His. Thus, heavy calcium of the aortic valve can infiltrate this area, leading to AV conduction abnormalities. Annular calcium have been linked to an increased incidence of conduction system abnormalities after surgical aortic valve replacement, requiring permanent pacemaker (PPM) implantation in 3% to 8% of patients. In the early experience of transcatheter aortic valve implantation (TAVI) using the CoreValve system, the incidence of periprocedural AV conduction abnormalities was greater, requiring PPM implantation in >30% of cases. In contrast, the Edwards valve, which does not extend into the left ventricular outflow tract, is associated with a PPM implantation rate of only 5% to 6%. The possible factors related to the development of AV conduction abnormalities in patients who undergo TAVI with a CoreValve system could include the high-risk profile of the patients, the procedural technique, and the CoreValve design of a self-expanding prosthesis (which extends into the left ventricular outflow tract). Current data regarding the risk factors for the development of high-degree AV block (HDAVB) in this population are limited. The aim of our study was to identify the independent predictors and the time course for the development of HDAVB and PPM implantation among 70 patients who underwent TAVI with a CoreValve system at 3 centers in Israel.
Methods
The study population included consecutive patients with aortic stenosis in whom a CoreValve Revalving System was implanted at 3 referral medical centers in Israel from 2008 to 2010. The patients were referred for TAVI after a careful evaluation and discussion by a local heart team, with a consensus that surgical aortic valve replacement would be associated with either high or prohibitive risk. The baseline clinical, electrocardiographic, echocardiographic, and angiographic parameters were collected for each patient, as well as information regarding the development of conduction system abnormalities and the need for PPM implantation after the procedure. In patients undergoing PPM implantation, the underlying rhythm was assessed at 3 months of follow-up. The records from the 3 medical centers were merged into a common database and included in the Israeli TAVI registry.
Of the 79 consecutive patients who underwent TAVI with a CoreValve Revalving System in the 3 medical centers from 2008 and 2010, 7 were excluded because of the presence of a PPM before implantation and 2 died within 24 hours of implantation. Thus, the final study sample included 70 patients with complete baseline and postprocedural follow-up information.
The prosthesis consists of a self-expanding nitinol frame to which a bioprosthetic porcine pericardial tissue valve is secured. Currently, the prosthesis is available in 26- and 29-mm sizes. The selection of the device depends on the measurements of the aortic valvular anatomy obtained using echocardiography, angiography, or multislice computed tomography. Balloon valvuloplasty was performed before deployment of the prosthesis. All patients had transvenous temporary cardiac pacing during the procedure. Burst rapid pacing at 150 to 220 beats/min was used to reduce cardiac motion and transvalvular flow during balloon dilation. The temporary pacing catheter was removed 24 to 48 hours after the procedure if no evidence of advanced AV block was apparent. Positioning and deployment of the device was performed solely under fluoroscopic and angiographic guidance. On the basis of the recommendations at that time, the ventricular edge of the valve frame was aimed to be implanted approximately 8 to 10 mm below the lower edge of the right noncoronary cusp as identified on contrast aortography. In 35 patients (49%), the 26-mm device was implanted and the 29-mm device was used in 36 patients (51%). Transthoracic or transesophageal echocardiography was performed before and during the procedure and before discharge. Baseline electrocardiograms were obtained before the procedure, and the electrocardiogram was continuously recorded during the procedure using 3 leads and then daily after the procedure until hospital discharge and at 1 month after the procedure. The decision to implant a PPM was made by the attending physician at each of the 3 medical centers. A pacemaker check was performed for all paced patients at 3 months, with evaluation of the underlying rhythm by gradual slowing and inhibition of the pacemaker for several seconds. The diagnostic criteria recommended by the World Health Organization and International Society and Federation for Cardiology Task Force were applied to electrocardiographic interpretation. High-degree AV block (HDAVB) was defined as Mobitz type 2 or complete AV block.
The primary outcome measure of the present study was defined as the development of HDAVB within 30 days after the procedure; and the secondary outcome measure was defined as the need for PPM placement within 30 days of the procedure.
Statistical Analysis
The baseline characteristics of the study patients, stratified by the development of HDAVB, were compared using the chi-square test for categorical variables and the Mann-Whitney-Wilcoxon test for continuous variables. We included 15 potential clinical, electrocardiographic, echocardiographic, and procedural binary covariates ( Table 1 ) as candidate risk factors for the development of HDAVB. The thresholds for categorization of numeric variables were prespecified using clinical and laboratory accepted criteria. Univariate relations between the candidate factors and the primary and secondary outcomes measures were assessed using ordinary least squares logistic regression analysis. Response factors with p <0.20 were evaluated further by performing a best-subset logistic regression analysis, examining the models created from all possible combinations of predictor variables and using a penalty of 3.84 on the likelihood ratio chi-square value for each factor included (correlating to a p value of 5% for 1 df chi-square test). The cumulative probability of survival free of HDAVB after TAVI by the presence of baseline right bundle branch block (RBBB) and the depth of the implanted valve was assessed using the Kaplan-Meier method, and significance was tested with the log-rank test. A 2-sided 0.05 significance level was used for hypothesis testing.
| Characteristic | All (n = 70) | AV Block | p Value | |
|---|---|---|---|---|
| No (n = 45) | Yes (n = 25) | |||
| Clinical | ||||
| Age ⁎ (years) | 0.08 | |||
| Mean ± SD | 83 ± 5 | 84 ± 4 | 82 ± 6 | |
| Range | 66–91 | |||
| Women ⁎ | 44 (63%) | 30 (67%) | 14 (56%) | 0.09 |
| Smoker | 11 (16%) | 7 (15%) | 4 (16%) | 0.93 |
| Coronary heart disease † | 38 (54%) | 26 (57%) | 12 (48%) | 0.27 |
| Diabetes mellitus | 24 (34%) | 15 (33%) | 9 (36%) | 0.78 |
| Hypertension ‡ | 58 (83%) | 35 (80%) | 22 (84%) | 0.72 |
| Hypercholesterolemia § | 57 (81%) | 35 (76%) | 22 (88%) | 0.23 |
| Renal failure | 18 (26%) | 11 (24%) | 7 (28%) | 0.86 |
| Atrial fibrillation ⁎ | ||||
| Paroxysmal | 16 (23%) | 10 (22%) | 6 (24%) | 0.79 |
| Permanent | 3 (4%) | 2 (5%) | 1 (4%) | 0.73 |
| New York Heart Association functional class | 0.52 | |||
| III | 51 (72%) | 36 (78%) | 15 (60%) | |
| IV | 20 (28%) | 10 (22%) | 10 (40%) | |
| Previous coronary artery bypass grafting | 16 (23%) | 9 (20%) | 7 (28%) | 0.42 |
| Electrocardiographic | ||||
| First-degree atrioventricular block ⁎ | 6 (9%) | 3 (7%) | 3 (12%) | 0.48 |
| QRS >120 ms ⁎ | 11 (16%) | 4 (9%) | 7 (28%) | 0.01 |
| Right bundle branch block ⁎ | 11 (16%) | 1 (2%) | 10 (40%) | <0.0001 |
| Left bundle branch block ⁎ | 17 (24%) | 11 (24%) | 6 (24%) | 0.93 |
| Bundle branch block + first-degree atrioventricular block ⁎ | 6 (9%) | 0 (0%) | 6 (24%) | <0.0001 |
| Echocardiographic | ||||
| Interventricular septum >11 mm ⁎ | 66 (94%) | 42 (93%) | 24 (96%) | 0.84 |
| Left ventricular outflow tract annulus >22 mm ⁎ | 18 (26%) | 10 (22%) | 8 (32%) | 0.51 |
| Severe aortic valve calcium ⁎ | 51 (73%) | 31 (69%) | 20 (80%) | 0.32 |
| Severe pulmonary hypertension(>60 mm Hg) ⁎ | 15 (21%) | 6 (13%) | 9 (36%) | 0.03 |
| Procedural | ||||
| Implanted valve 29 mm ⁎ | 37 (53%) | 22 (49%) | 15 (60%) | 0.38 |
| Depth of implanted valve (mm) ⁎ ¶ | 5.9 ±1.4 | 5.5 ±1.2 | 6.6 ±1.6 | 0.002 |
⁎ Prespecified as candidate risk factors for development of postprocedural HDAVB.
† Coronary heart disease: ≥1 coronary artery with >50% stenosis.
‡ Blood pressure >140/90 mm Hg.
The statistical software used for analyses was the Statistical Package for Social Sciences, version 19.0 (SPSS, Chicago, Illinois).
Results
Of the 70 study patients, 25 (36%) developed HDAVB during or after the procedure. All patients who developed HDAVB underwent PPM implantation. In addition, 3 patients underwent PPM implantation because of the development of left bundle branch block with PR prolongation (n = 2) or slow atrial fibrillation (n = 1). Thus, 28 patients (40%) required PPM implantation after the procedure. The baseline clinical, electrocardiographic, echocardiographic, and procedural characteristics, stratified by the development of HDAVB after TAVI, are listed in Table 1 . The patients who developed HDAVB tended to be younger and were somewhat more likely to be men. The frequency of baseline RBBB and severe pulmonary hypertension was significantly greater among patients who developed HDAVB. In addition, the depth of the implanted valve was significantly higher in the patients who developed HDAVB than in the patients who did not develop this complication.
The course of the electrocardiographic changes at baseline, during the procedure, and at follow-up, is listed in Table 2 . All 6 patients with both first-degree AV block plus any bundle branch block (2 right and 4 left) at baseline and 10 of 11 patients with baseline RBBB developed HDAVB during or after the procedure and underwent PPM implantation (p <0.05). In addition, 33 patients (47%) developed new left bundle branch block (4 with first-degree AV block) and 3 patients (4%) developed new RBBB (1 with first-degree AV block) after the procedure. Of those with newly developed left bundle branch block, 6 patients (18%) subsequently developed HDAVB, and 8 had resolution by hospital discharge, and 1 did so after 1 month. Of those with newly developed RBBB, 1 patient (33%) subsequently developed HDAVB and 2 persisted. The development of both left bundle branch block and RBBB occurred at a similar frequency among patients who did not go on to develop HDAVB, suggesting that postprocedural bundle branch block was not a predictor of HDAVB among the study patients.
| Variable | Baseline | During and Immediately After | During Hospital Stay | Discharge | 1 mo After Discharge |
|---|---|---|---|---|---|
| Sinus rhythm | 62 (89%) | 45 (64%) ⁎ | 44 (63%) | 34 (49%) | 40 (57%) |
| Atrial fibrillation | 8 (11%) | 11 (16%) | 13 (19%) | 8 (11%) | 8 (11%) |
| Left bundle branch block | 13 (19%) | 34 (49%) | 18 (26%) | 15 (21%) | 13 (19%) |
| Left bundle branch block + first-degree atrioventricular block | 4 (6%) | 12 (17%) | 19 (27%) | 13 (19%) | 13 (19%) |
| Right bundle branch block | 9 (13%) | 3 (4%) | 3 (4%) | 3 (4%) | 2 (3%) |
| Left anterior hemiblock | 10 (14%) | 2 (3%) | 2 (3%) | 3 (4%) | 3 (4%) |
| Right bundle branch block + first-degree atrioventricular block | 2 (3%) | 5 (7%) | 1 (1%) | 0 (0%) | 1 (1%) |
| First-degree atrioventricular block | 5 (7%) | 1 (1%) | 1 (1%) | 1 (1%) | 2 (3%) |
| Atrioventricular block Mobitz type I | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) |
| High-degree atrioventricular block | 0 (0%) | 10 (14%) | 15 (21%) | 11 (16%) | 0 (0%) |
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