Author + information
- Received December 16, 2011
- Revision received March 19, 2012
- Accepted March 26, 2012
- Published online May 1, 2012.
- Antonio J. Muñoz-García, MD, PhD⁎ (, )
- José M. Hernández-García, MD, PhD,
- Manuel F. Jiménez-Navarro, MD, PhD,
- Juan H. Alonso-Briales, MD,
- Antonio J. Domínguez-Franco, MD,
- Julia Fernández-Pastor, MD,
- Jose Peña Hernández, MD,
- Alberto Barrera Cordero, MD,
- Javier Alzueta Rodríguez, MD, PhD and
- Eduardo de Teresa-Galván, MD, PhD
- ↵⁎Reprint requests and correspondence:
Dr. Antonio J. Muñoz-García, Department of Cardiology, Virgen de la Victoria Clinical University Hospital, Campus de Teatinos s/n, 29010 Málaga, Spain
Objectives The purpose of this study was to evaluate the need for a permanent pacemaker after transcatheter aortic valve implantation with the CoreValve prosthesis (Medtronic, Inc., Minneapolis, Minnesota) using the new Accutrak delivery system (Medtronic, Inc.).
Background The need for a permanent pacemaker is a recognized complication after transcatheter aortic valve implantation with the CoreValve prosthesis.
Methods Between April 23, 2008 and May 31, 2011, 195 consecutive patients with symptomatic aortic valve stenosis underwent transcatheter aortic valve implantation using the self-expanding CoreValve prosthesis. In 124 patients, the traditional delivery system was used, and in 71 patients, the Accutrak delivery system was used.
Results There were no significant differences in baseline electrocardiographic characteristics between the traditional system and the Accutrak patients: PR interval: 153 ± 46 mm versus 165 ± 30 mm, p = 0.12; left bundle branch block: 22 (20.2%) versus 8 (12.7%), p = 0.21; right bundle branch block: 21 (19.3%) versus 8 (12.7%), p = 0.26. The depth of the prosthesis in the left ventricular outflow tract was greater with the traditional system than with the Accutrak system (9.6 ± 3.2 mm vs. 6.4 ± 3 mm, p < 0.001) and the need for a permanent pacemaker was higher with traditional system than with Accutrak (35.1% vs. 14.3%, p = 0.003). The predictors of the need for a pacemaker were the depth of the prosthesis in the left ventricular outflow tract (hazard ratio [HR]: 1.2, 95% confidence interval [CI]: 1.08 to 1.34, p < 0.001), pre-existing right bundle branch block (HR: 3.5, 95% CI: 1.68 to 7.29, p = 0.001), and use of the traditional system (HR: 27, 95% CI: 2.81 to 257, p = 0.004).
Conclusions The new Accutrak delivery system was associated with less deep prosthesis implantation in the left ventricular outflow tract, which could be related to the lower rate of permanent pacemaker requirement.
Transcatheter aortic valve implantation (TAVI) is becoming an established alternative therapy in the treatment of symptomatic aortic stenosis in patients with a high surgical risk in Europe and Canada. TAVI is associated with 30-day mortality below 10% (1–4) and a similar 1-year survival compared with that seen with surgical aortic valve replacement (5). One of the limitations of TAVI with the CoreValve prosthesis (Medtronic, Inc., Minneapolis, Minnesota) is the need for a definitive pacemaker after the implantation due to disturbances in atrioventricular (AV) conduction. The need for a post-operative permanent pacemaker varies greatly (6) and reaches over 30% in some series (2,4). These results are far higher than those found after using the Edwards-Sapien prosthesis (Edwards Lifesciences, Irvine, California) (1) or after surgical aortic valve replacement, which range from 5% to 8% (7). These variations may be partly explained by differences in prosthesis design and implantation technique.
The aim of this study was to analyze the factors predicting and affecting the need for a pacemaker after TAVI with the CoreValve aortic valve prosthesis using the new Accutrak release system (Medtronic, Inc.).
Between April 23, 2008 and May 31, 2011, 195 patients with severe aortic valve stenosis and a high surgical risk were treated with the CoreValve aortic valve prosthesis. In 124 patients (63.6%), the traditional system (TS) was used. The remaining 71 patients (36.4%) underwent the procedure with the new Accutrak release system. All the patients were evaluated by a multidisciplinary team composed of surgeons and clinical and interventional cardiologists. The process for patient selection and evaluation of the complications followed the joint consensus recommendations of the various scientific societies (8), and the Valve Academic Research Consortium criteria (9), as well as complying with the necessary anatomical criteria for percutaneous implantation with the CoreValve aortic valve prosthesis (2,4).
Of the 195 patients, 18 were excluded from the analysis as they had a definitive pacemaker due to advanced AV block before the TAVI and 3 due to failure in the implantation of the CoreValve prosthesis. Thus, the final analysis involved 111 patients with TS and 63 patients with Accutrak.
Description of the prosthesis and release system
The CoreValve prosthesis consists of a trileaflet bioprosthetic porcine pericardial tissue valve, which is mounted and sutured in a self-expanding nitinol stent frame. There are 2 different valve sizes currently available for different annulus dimensions: the 26-mm prosthesis (small prosthesis) for aortic valve annulus sizes from 20 to 23 mm and the 29-mm prosthesis (large prosthesis) for aortic valve annulus sizes from 23 to 27 mm. The small prosthesis is 55 mm long and the large prosthesis 53 mm.
The traditional release system for the CoreValve aortic valve prosthesis is a 12-F catheter for the first 108 cm and 18-F (6 mm) for the distal portion (7 cm long), introduced via a 0.035-inch guidewire. The distal portion of the catheter, which transports the prosthesis folded in a sheath, is characterized by being flexible and directable, as well as possessing the necessary stiffness to navigate through the aortic annulus. The proximal end consists of a precise release system composed of 2 adjustment knobs, 1 for rotation, called micro, and the other for sliding, called macro. After positioning the catheter at the level of the aortic annulus, the micro knob is used to withdraw the sleeve slowly, thereby releasing the prosthesis, which recovers its original position in contact with the blood.
The first 90.9 cm of the new Accutrak release system has a 15-F additional layer isolating the retractable sheath, permitting greater stability when introducing the catheter into the aortic annulus and starting release of the prosthesis, making the transmission of the release strength imparted with the micro knob more proportionate, thus preventing uncontrolled displacement of the prosthesis toward the interior of the left ventricle during the release process.
Before the procedure, the patients took acetylsalicylic acid 100 mg, which they then continued indefinitely. They also received a loading dose of clopidogrel 300 mg, later continuing with 75 mg for at least 6 months. During the procedure, intravenous sodium heparin was given, adjusted for weight (70 IU/kg). Antibiotic prophylaxis was given with cephalosporin or vancomycin if the patient was allergic to beta-lactams.
Almost all (92.3%) of the procedures were performed under local anesthesia with superficial sedation. Access was via the femoral artery in most cases, with an 18-F introducer, closing the femoral puncture with the Prostar XL 10-F percutaneous closure device (Abbott Vascular Devices, Redwood City, California). In 18 patients, the left subclavian artery was used as the access route, in collaboration with the cardiac surgeon who performed the opening and closure of the artery.
After positioning a transitory pacemaker catheter via the transjugular route, the femoral artery was punctured for the implantation of the valve, leaving the closure device fitted. Aortic valvuloplasty was then performed with cardiac overstimulation at a frequency of 150 to 180 beats/min to prevent balloon displacement. The aortic prosthesis was then released under fluoroscopy-guided angiographic control. After the procedure, the patients were monitored by telemetry for 4 days and echocardiographic control at 72 h.
All the patients had an electrocardiogram (ECG) before and after the percutaneous implant. Analyses were made of the rhythm; heart rate; and PR, QRS, and QT intervals (measured in milliseconds at a speed of 25 mm/s), as well as the presence of bundle branch block or advanced AV block according to the criteria recommended by the World Health Organization and the International Society and Federation for Cardiology Task Force to define hemiblock and right bundle branch block (RBBB) and left bundle branch block (LBBB) (10). The implantation of a definitive pacemaker was indicated by the cardiology care team in the presence of third- and second-degree AV block (Mobitz type 2), following the recommendations of the European Society of Cardiology for patients with acquired AV block in special situations, such as valve surgery (11).
Quantitative angiography, done by 2 independent observers, was used to measure the depth of the prosthetic structure in the outflow tract by the distance (in millimeters) from the noncoronary cusp to the distal extreme of the prosthesis situated in the left ventricle, as described by Piazza et al. (12).
The implantation was considered normal when the depth of the prosthesis in the left ventricular outflow tract (LVOT) was 4 to 8 mm, high when it was below 4 mm, and low when it was more than 8 mm (13). The number of primary operators that were involved in this study was 2 in all patients.
Severe calcification was defined as the presence of heavy calcification of all cusps or bulky calcification detected on the aortic angiogram (14).
The continuous variables are expressed as the mean ± SD and the qualitative variables as percentages. The chi-square test was used for the qualitative variables and the Student t test for paired data for continuous variables, as all the variables had a normal distribution. A multivariate analysis was performed with a backward stepwise Cox regression analysis to identify independent variables predicting the need for a pacemaker due to AV block. This model included those variables with probability value <0.05 in the univariate analysis. Results are presented as hazard ratios with 95% confidence intervals. Significance was set at p < 0.05. The data were analyzed with SPSS (version 15.0, SPSS, Inc., Chicago, Illinois).
The success rate for the procedure was 97.5% for the TS and 100% for Accutrak. After the implantation, 48 patients (27.6%) required a definitive pacemaker due to AV conduction disturbances. Table 1 shows the baseline characteristics and the procedure data according to the release system used.
No significant differences were found in the baseline electrocardiographic characteristics between the TS patients and the Accutrak patients (Table 2).
The depth of the prosthesis in the LVOT was greater in the TS patients than in the Accutrak patients (9.6 ± 3.2 mm vs. 6.4 ± 3 mm, p < 0.001). Only 36.3% of the TS patients had a depth <8 mm compared with 74.6% of the Accutrak patients (p < 0.001) (Fig. 1). The need for a pacemaker was greater in the TS patients than in the Accutrak patients (35.1% vs. 14.3%, p = 0.003). New-onset LBBB occurred in 41.5% of patients with TS and 56.3% of patients with Accutrak system (p = 0.210) after excluding the patients with LBBB on baseline ECG.
In 18 patients, the subclavian route was used, 9 patients with TS and the other 9 patients with the Accutrak system. There were not significant differences between the TS patients and the Accutrak patients in the need for a pacemaker (44.4% vs. 22.2%, p = 0.317), depth in the LVOT (10.2 ± 3.2 mm vs. 7.6 ± 3.3 mm, p = 0.112), and low implantation (55.6% vs. 44.4%, p = 0.444) in this subgroup.
In our series, we found that 34 patients (21.1%) experienced AV block during the procedure and 22 (64.7%) of these patients required a definite pacemaker. There was a higher rate of intraprocedural AV block for the TS than the Accutrak group (Table 1). Of the 26 patients who required pacemaker by conduction disturbances after procedure and without AV block during the procedure, there were not significant differences between TS patients compared with Accutrak patients (58.3% vs. 55.6%, p = 0.880), but we found differences in the occurrence AV block in the time, with a median of 48 h (24 to 72 h) for the TS group and 72 h (48 to 148 h) for Accutrak group (p < 0.005).
In the analysis of the first one-half of the TS patients compared with the second one-half showed no significant differences in the need for a pacemaker (34.5% in the first one-half vs. 35.7% in the second one-half, p = 0.974) nor in the depth of the prosthesis (10 ± 3.2 mm vs. 9.2 ± 3.2 mm, p = 0.226). In the same analysis of the Accutrak patients, no significant differences were found (12.9% in the first one-half vs. 15.6% in the second one-half, p = 0.758) nor in the depth of the prosthesis (6.13 ± 2.7 mm vs. 6.8 ± 3.4 mm, p = 0.401).
The factors associated with the need for a pacemaker are shown in Table 3. Of note among these were baseline electrocardiographic disturbances, mainly the presence of RBBB and the presence of hemiblock, and the parameters related with the procedure, such as the position of the prosthesis.
The multivariate analysis showed that the predictors of the need for a definitive pacemaker due to ventricular conduction disorders were the depth of the prosthesis in LVOT, the prior presence of RBBB, and use of the TS (Table 4).
With the introduction of the new Accutrak release system, we noted a significant reduction in the need for a pacemaker after the percutaneous implant with the CoreValve aortic valve prosthesis, falling from 35.1% to 14.3%. The main reasons for this decline were the simplicity to position the CoreValve prosthesis higher and because of fewer manipulations and less trauma to the LVOT during the procedure with the Accutrak release system. The membrane stabilizing the Accutrak system balances the transmission of the forces at the moment of release better, thus avoiding sudden displacement toward the interior of the left ventricle, minimizing mechanical trauma against the left bundle branch, and enabling the prosthesis to be adequately placed in the valvular plane.
The incidence of AV conduction disturbances with the need to implant a definitive pacemaker after TAVI with the CoreValve aortic valve prosthesis is high (15,16). This is easily explained if we recall the anatomic relation between the AV conduction system and the aortic valve. Rubín et al. (17) recently reported that after implantation with the CoreValve aortic valve prosthesis there is worsening of AV conduction, due to the direct damage of the bundle of His or the AV node. In an autopsy, Moreno et al. (18) demonstrated the histopathologic presence of a hematoma of the interventricular septum that compromised the bundle of His after implanting an Edwards-Sapien prosthesis, which could explain the AV conduction disturbances. In our series, we found that of the 48 patients who required a permanent pacemaker, 22 patients experienced AV block during the procedure. The possible mechanisms involved include inflammation, edema, ischemia, and mechanical trauma over the interventricular septum, with the resulting consequences in the conduction system, which may be transitory as occurs with the balloon used to predilate the native valve (19). Gutiérrez et al. (20) reported transitory ECG changes after implanting the Edwards-Sapien prosthesis, with the incidence of LBBB increasing from 9% at baseline to 27% after the procedure, and then falling at 1 month to 13%.
The greater prosthetic surface area in contact with the LVOT and the particular characteristics of nitinol, which provide a continued self-expansion, might account for the differences in the percentage of pacemaker implants due to persistent AV conduction disorders between the CoreValve aortic valve prosthesis and the Edwards-Sapien prosthesis, which is mounted over a balloon and is shorter (14 mm) and therefore has less contact with the LVOT.
Our study also confirms other previously described factors regarding the need for pacemaker implantation: the depth of the prosthesis in the LVOT (14,15) and the previous presence of RBBB (14,21). The improvements incorporated into the release system of the prosthesis thus allow greater stability during the implantation and a higher position, resulting in a reduction in AV conduction disorders. In our study, cessation of chronotropic therapy is a potential independent negative predictor of pacemaker placements. Because chronotropic therapy before implantation has been suggested to increase the need for pacing (22), in this scenario, it is reasonable that this may favor a strategy of that cessation of chronotropic therapy before the procedure.
We found that there were more incidences of stroke in the Accutrak group than in the TS group (7.9% vs. 0.9%, p = 0.015) after TAVI in according to Valve Academic Research Consortium criteria, likely because there were more previous strokes in the Accutrak group than in the TS group (23.8% vs. 11.7%, p = 0.037) before the procedure. We also found a trend toward more vascular complications with the Accutrak group, which could be related to poor femoral vascular access in the Accutrak group (mean diameter femoral vascular 6.8 ± 1.4 mm vs. 7.2 ± 1.2 mm, p = 0.053).
A possible limitation of this study concerns operator experience, attempting to position the prosthesis at <8-mm depth from the aortic annulus. Nevertheless, analysis of the first one-half compared with the second one-half of the TS patients and Accutrak patients showed no significant differences in the need for a pacemaker or in the depth of the prosthesis. Also, the operators that were involved in this study were the same in all patients. The cardiology care team had the same criteria for placing permanent pacemakers for AV block as those indicated in the Methods section. Another possible limitation concerns the method used to measure the depth of the CoreValve aortic valve prosthesis. We used quantitative angiography, as have other series, though different imaging techniques, such as computerized tomography or magnetic resonance, could provide more accurate quantification of the depth of the prosthesis in the LVOT. There was a numerical, but statistically nonsignificant, trend toward less LBBB, RBBB, and hemiblock in the Accutrak patients than in the TS patients, and it could to be associated with reduced pacemaker need. Although there were significant differences in the univariate analysis between the no pacemaker group and the pacemaker group in relation to RBBB and hemiblock, furthermore, it seems these differences may have contributed to the magnitude of the difference in pacemaker needs between the TS group and the Accutrak group, although they probably do not take away from the fact that traditional system is an independent predictor of the need for pacemaker. In addition, the ratio of endpoint count to predictors evaluated is low and that replication in a larger sample is indicated.
The new Accutrak release system was associated with less deep prosthesis implantation in the LVOT, which could be related to the lower rate of permanent pacemaker requirement.
Drs. Hernández-García and Alonso-Briales are physician proctors for Medtronic, Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- left bundle branch block
- left ventricular outflow tract
- right bundle branch block
- transcatheter aortic valve implantation
- traditional system
- Received December 16, 2011.
- Revision received March 19, 2012.
- Accepted March 26, 2012.
- American College of Cardiology Foundation
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