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Atrioventricular Block After Transcatheter Balloon

Expandable Aortic Valve Implantation

Ajay Sinhal, MD, Lukas Altwegg, MD, Sanjeevan Pasupati, MBCHB,

Karin H. Humphries, DSC, Michael Allard, MD, Paul Martin, MBCHBAO, PHD,

Anson Cheung, MD, Jian Ye, MD, Charles Kerr, MD, Sam V. Lichtenstein, MD, PHD,

John G. Webb, MD, FACC Vancouver, British Columbia, Canada

Objectives Transcatheter aortic valve replacement (AVR) is a promising approach to aortic valve disease. The implications of this new therapy are not entirely known. We describe the potential for the development of new atrioventricular (AV) block.

Background Atrioventricular block is a known complication of conventional surgical AVR. Block is presumed to occur as a consequence of surgical trauma to the cardiac conduction tissue during ex-cision of the diseased aortic valve and débridement of the calcified annulus. Whether AV block might occur as a consequence of nonsurgical implantation of an aortic stent valve is unknown. Methods We reviewed our experience with patients undergoing transcatheter AVR using both the percutaneous transarterial and the open-chest direct left ventricular apical ventriculotomy ap-proaches. Patients were considered at high risk for conventional surgery because of comorbidities. Continuous arrhythmia monitoring was performed for at least 48 h after the valve implantation pro-cedure. Patients who developed apparently new, clinically significant AV block were identified. Results Transcatheter AVR was successfully performed in 123 patients. Seventeen of these patients (13.8%) had pre-existing permanent pacemakers. Two patients (1.6%) required pacemaker implanta-tion because of pre-existing intermittent bradycardia. Seven patients (5.7%) developed new and sus-tained complete AV block requiring pacemaker implantation. An additional 4 patients (3.3%) devel-oped new and sustained left bundle branch block but did not require pacemaker implantation. Conclusions As with conventional AVR surgery, transcatheter AVR may result in impaired atrioven-tricular conduction. Physicians and patients should be aware of the potential for AV block and pace-maker dependence. (J Am Coll Cardiol Intv 2008;1:305–9) © 2008 by the American College of Cardiology Foundation

From the Heart Centre, St. Paul’s Hospital, University of British Columbia, Vancouver, Canada. Dr. John Webb is a consultant to Edwards Lifesciences, Irvine, California.

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Atrioventricular (AV) block is a well-described complica-tion of surgical aortic valve replacement (AVR). New AV block reportedly requires pacemaker implantation in up to 6% of surgical patients (1–3). The mechanism is presumably injury to the cardiac conduction system during surgical excision of the adjacent diseased valve and annular tissue.

Transcatheter AVR is a relatively new alternative to conventional surgical valve replacement (Fig. 1) (4,5). In contrast to surgery, transcatheter AVR does not involve excision of the diseased native valve or annular tissue. Whether AV block can occur with transcatheter AVR because of annular dilatation and stent implantation in the absence of surgical excision of valve or annulus tissue is not known.

Methods

Patients. The procedure was approved for clinical use by the

Department of Health and Welfare, Ottawa, Canada, in patients with severe, symptomatic aortic stenosis. Accep-tance for the procedure required a consensus agreement among a group of senior sur-geons and cardiologists that the risk of mortality or morbidity with conventional surgery was excessive caused by comorbidi-ties. Patient or physician prefer-ence alone was not considered adequate (6). Written informed consent was obtained. All pa-tients undergoing transcatheter AVR at our institution were prospectively followed up.

Procedure. Transcatheter AVR was performed using either

percutaneous femoral arterial access (7,8) or open-chest left ventricular puncture (5,9). Procedures were performed with fluoroscopic imaging and, for the most part, under a general anesthetic with transesophageal echocardiographic imaging. The diameter of the aortic annulus at the site of leaflet insertion was estimated in a long-axis view of the left ventric-ular outflow tract using transesophageal echocardiography.

The aortic valve was initially dilated using a standard valvuloplasty balloon with a nominal diameter approxi-mately the same as the aortic annulus diameter as measured by echocardiography. A balloon-expandable valve (Cribier-Edwards or (Cribier-Edwards-SAPIEN, (Cribier-Edwards Lifesciences, Ir-vine, California) was used. This consists of a balloon-expandable stainless steel stent with an attached pericardial valve and fabric sealing cuff. Two sizes of prosthetic valve were used; a smaller prosthesis intended to be expanded with a 22-mm-diameter balloon to achieve a 23-mm exter-nal diameter and a larger prosthesis intended to be expanded with a 25-mm balloon to achieve a 26-mm external diam-eter. The 23-mm external diameter valve was considered

suitable for an annulus diameter of 18 to 22 mm and a 26-mm valve for an annulus diameter of to 21 to 25 mm. Our approach was to routinely select a prosthesis that exceeded the measured annulus diameter by 10% to 20%. Routine oversizing was intended to securely fix the prosthe-sis within the native valve and annulus and minimize the potential for paravalvular leaks between the prosthetic valve and native annulus (4).

Burst rapid pacing at 150 to 220 beats/min was used to reduce cardiac motion and transvalvular flow during balloon dilation and prosthetic valve deployment (10). A temporary transvenous right ventricular lead was used for the percuta-neous transarterial approach, and a left ventricular epicardial lead for the transapical approach. The temporary pacemaker leads were removed after valve implantation, unless required because of pacemaker dependence. Cardiopulmonary bypass was not used.

Data collection. Patients were assessed with a history,

elec-trocardiogram, and routine blood tests during screening, immediately before the procedure, daily for 3 days post-procedure, and at 30 days after the procedure. A transtho-racic echocardiogram was obtained before and after valve implantation and at 30 days after the procedure. Electro-cardiographic monitoring was performed during the proce-dure and continued for at least 48 h. In addition to interrogation of an ongoing prospective database, patient records were reviewed for prior evidence of atrioventricular block.

Statistical methods. Continuous variables are presented as

means or medians, as appropriate, or proportions for cate-gorical variables. Given the small sample size, the Fisher exact test was used to compare proportions and the Mann-Whitney Utest was used to compare continuous variables. Univariate logistic regression was used to examine potential factors associated with pacemaker requirement.

Results

Transcatheter aortic valve implantation was successfully performed in 123 patients. Patients were generally elderly with multiple comorbidities (Table 1). The logistic Euro-SCORE operative mortality estimate was 30.1% (range 19.5% to 42.8%) (11). Of the cohort of 123 patients, 17 (13.8%) were pacemaker dependent before aortic valve implantation. Characteristics of 106 patients without a pre-existing pacemaker are shown in Table 1. Two of 106 patients (1.9%) underwent post-procedural pacemaker im-plantation because of pre-existing episodic bradycardia. It seemed that episodic bradycardia was not new, but rather was only fully appreciated by in-hospital monitoring. In 7 of 106 patients (6.6%), new and complete AV block was evident immediately after transcatheter aortic valve implan-tation. Patients with heart block were monitored in the coronary care unit, and medications known to impair AV

Abbreviations and Acronyms

AVⴝatrioventricular

AVRaortic valve replacement

LVEFⴝleft ventricular ejection fraction

NYHANew York Heart Association

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conduction were discontinued. Permanent pacemakers were implanted after 45 ⫾ 23 h of continued dependency on temporary pacing.

New left bundle branch block was documented at the time of the post-procedural electrocardiogram in 7 patients (5.7%). Isolated left bundle branch block was transient in 3 Figure 1.Photographs of the Interventricular Septum in a Patient Who Developed New Atrioventricular Block After Transcatheter Aortic Valve Implantation

(A)Photograph showing macroscopically visible myocardial injury.(B)Photomicrographs of the upper interventricular septum showing myocardial necrosis of the leftward portion of the septum. The arrowheads delineate the rightward extent of myocardial injury.(C)Higher magnification (boxed area in B) shows necrotic cardiac myocytes (arrow) in contradistinction to viable cardiac myocytes (asterisk).(D)Photomicrograph of the upper interventricular septum from a patient who did not develop atrioventricular block showing no myocardial necrosis. Trichrome stain:B, C and D.

Table 1.Clinical Characteristics of 106 Patients Without a Previously Implanted Pacemaker Undergoing Transcatheter Aortic Valve Replacement

Variables

No New Pacemaker-Dependent Atrioventricular Block

New Pacemaker-Dependent

Atrioventricular Block p Value

n 99 7

Age (yrs), median [Q1, Q3] 84.8 [77.4, 87.5] 83.5 [79.9, 88.1] 0.82*

Male, n (%) 57 (57.6) 1 (14.3) 0.045†‡

Baseline regurgitation gradeⱖ3, n (%) 7 (7.1) 0 (0) 1.0†

Left ventricular ejection fraction (%), median [Q1, Q3] 60 [45, 65] 65 [55, 65] 0.38*

New York Heart Association functional classⱖ3, n (%) 86 (86.9) 6 (85.7) 1.0†

Logistic EuroSCORE (%), median [Q1, Q3] 30.5 [19.5, 41.5] 41.2 [14.3, 50.8] 0.68*

Syncope, n (%) 15 (15.2) 2 (28.6) 0.31†

Pulmonary hypertension, n (%)§ 22 (22.2) 3 (42.9) 0.35†

Atrial fibrillation, n (%) 41 (41.4) 3 (42.9) 1.0†

First-degree block, n (%) 15 (15.2) 1 (14.3) 1.0†

Second-degree block, n (%) 1 (1) 0 (0) 1.0†

Left bundle branch block , n, %) 12 (12.1) 0 (0) 1.0†

Right bundle branch block, n (%) 9 (9.1) 1 (14.3) 0.51†

Potassium disorder pre-procedure (n,%)¶ 14 (14.1) 2 (28.6) 0.28†

Potassium disorder post-procedure, n (%)¶ 22 (22.2) 2 (28.6) 0.66†

Transarterial procedure, n (%) 71 (71.7) 3 (42.9) 0.19†

Prosthesis/annulus diameter ratio, mean⫾SD 1.1⫾0.8 1.2⫾0.8 0.06*

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(2.4%) but persisted until hospital discharge in 4 (3.2%). At 6 months follow-up, 6 of the 7 patients with transient or sustained isolated left bundle branch block remain well. One patient with transient left bundle branch block died of progressive congestive heart failure 4 months after transapi-cal AVR. None have required pacemaker implantation.

At 6 months, 6 of 7 patients with new complete heart block remain well, but pacer dependent. In the remaining patient, persistent complete AV block immediately fol-lowing valve implantation had developed and the patient underwent permanent pacemaker implantation on day 6. An acutely ischemic bowel resulted in death on day 10. At post-mortem, localized macroscopic myocardial ne-crosis was observed in the leftward basal interventricular septum (Fig. 1A). Necrosis was located slightly apical to the implant rather than directly adjacent to it. Micro-scopically, the necrosis showed a geographic pattern characteristic of ischemic injury with sparing of suben-docardial myocytes. In addition, myocytes were replaced at the periphery of the injured area by a cellular infiltrate comprised of macrophages and mesenchymal cells, indic-ative of a reparindic-ative response and consistent with an onset of injury approximately 10 days previously. Myocardial injury was also seen microscopically in the uppermost portion of the leftward interventricular septum (Figs. 1B and 1C) in the immediate vicinity of the conducting tissues. The atrioventricular node itself did not show convincing evidence of myocyte injury. In the most superior aspects of the septum, myocytes in the suben-docardial region were injured, whereas more inferiorly, but still deep to the stented prosthesis, the subendocar-dial myocytes were spared. No thrombi or emboli were noted in any of the intramyocardial arteries.

Predisposing factors. In the cohort of 123 patients, 17 had

pre-existing permanent pacemakers and 7 required pace-makers after aortic valve implantation. Among those 99 patients who were not paced before or after valve implan-tation, pre-existing conduction abnormalities were com-mon, being identified in 37 patients (37.3%) as shown in

Table 1. These included first-degree block in 15 patients

(15.2%), right bundle branch block in 9 (9.1%), left bundle branch block in 12 (12.1%), and second-degree heart block in 1 (1.0%). One of 7 patients developing new and sustained complete AV block had pre-existing right bundle branch block. No pre-existing conduction abnormalities were ap-parent in the remaining 6 individuals who developed new complete AV block. Univariate logistic regression analysis did not identify any risk factors associated with pacemaker requirement (Table 1).

Discussion

New AV block is a known complication of surgical AVR, requiring pacemaker implantation in up to 6% of surgical

patients (1–3). In our transcatheter AVR experience in high-risk patients with multiple comorbidies, a comparable number, 5.7% of all patients, required a permanent pace-maker because of apparently new AV block. To put this in context, AV block has also been described as a consequence of aortic balloon valvuloplasty (12), aortic root abscess (13), and percutaneous device closure of membranous ventricular septal defect (14). That AV block might occur because of trauma to ventricular conduction tissues adjacent to the aortic valve is perhaps not surprising given the close prox-imity of these 2 structures.

Reported risk factors for complete AV block after surgery include previous aortic regurgitation, myocardial infarction, pulmonary hypertension, and postoperative electrolyte im-balance (15). Koplan et al (15) reported that right bundle branch block was the strongest predictor of pacemaker dependency after surgical aortic valve replacement. Similarly Ben Ameur et al (16) noted that bifasicular block was associated with the need for post-operative pacing. Univar-iate analysis of our experience did not suggest risk factors for heart block, although patient and event numbers may have been insufficient.

In our series, 1 of 10 patients with pre-existing right bundle branch block required pacemaker implantation. An additional 4 patients with new sustained left bundle branch block in the absence of pre-existing right bundle branch block remain well. It seems reasonable to hypoth-esize that balloon and stent trauma in the region of the aortic annulus and left ventricular outflow tract affecting the adjacent left bundle branch would be more problem-atic in the presence of pre-existing compromise of the right bundle. A 10% incidence of complete block in the setting of pre-existing right bundle branch block would be consistent with this.

In our patients, the prosthetic valve was routinely dilated to a diameter slightly larger than the echocardiographically estimated annulus diameter. The intention was to securely fix the prosthesis within the annulus and minimize paraval-vular regurgitation. Although not confirmed by univariate analysis, it seems reasonable to speculate that the use of relatively larger valve sizes and greater degrees of prosthesis/ annulus mismatch might result in greater compression of adjacent structures and more likely result in impaired AV conduction.

Study limitations. We attempted to distinguish between new bradycardia as a consequence of AVR and pre-existing bradycardia unrelated to AVR. However, pre-existing epi-sodic bradycardia may have been undetected in some pa-tients, leading to overestimation of the risk attributable to the procedure, particularly given the frequency of comor-bidities and the lack of a comparator group. Larger numbers of patients would be required to adequately assess risk factors for heart block. There are considerable differences

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between various types of implantable valves, and it is possible that the likelihood of AV block may vary.

Conclusions

As with conventional surgery, new or worsened AV block may occur as a consequence of transcatheter aortic valve implantation. Physicians and patients should be aware of the potential for AV block and pacemaker dependence.

Reprint requests and correspondence:Dr. John G. Webb, McLeod Professor of Heart Valve Intervention, St. Paul’s Hospital, Room 476A, 1081 Burrard Street, Vancouver, British Columbia V6Z 1Y6, Canada. E-mail: webb@providencehealth.bc.ca.

REFERENCES

1. El-Khally Z, Thibault B, Staniloae C, et al. Prognostic significance of newly acquired bundle branch block after aortic valve replacement. Am J Cardiol 2004;94:1008 –11.

2. Limongelli G, Ducceschi V, D’Andrea A, et al. Risk factors for pacemaker implantation following aortic valve replacement: a single centre experience. Heart 2003;89:901– 4.

3. Kolh P, Lahaye L, Gerard P, Limet R. Aortic valve replacement in the octogenarians: perioperative outcome and clinical follow-up. Eur J Car-diothorac Surg 1999;16:68 –73.

4. Webb JG, Chandavimol M, Thompson CR, et al. Percutaneous aortic valve implantation retrograde from the femoral artery. Circulation 2006;113:842–50.

5. Ye J, Cheung A, Lichtenstein SV, et al. Transapical aortic valve implantation in humans. J Thorac Cardiovasc Surg 2006;131:1194 – 6.

6. Vassiliades TA Jr., Block PC, Cohn LH, et al. The clinical develop-ment of percutaneous heart valve technology: a position statedevelop-ment of the Society of Thoracic Surgeons (STS), the American Association for Thoracic Surgery (AATS), and the Society for Cardiovascular Angiog-raphy and Interventions (SCAI) Endorsed by the American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA). J Am Coll Cardiol 2005;45:1554 – 60.

7. Webb JG, Chandavimol M, Thompson CR, et al. Percutaneous aortic valve implantation retrograde from the femoral artery. Circulation 2006;113:842–50.

8. Webb JG, Pasupati SJ, Humphries K, et al. Percutaneous transarterial aortic valve replacement in selected high risk patients with aortic stenosis. Circulation 2007;116:755– 63.

9. Lichtenstein SV, Cheung A, Ye J, et al. Transapical transcatheter aortic valve implantation in man. Circulation 2006;114:591– 6.

10. Webb JG, Pasupati S, Achtem L, Thompson CR. Rapid pacing to facilitate transcatheter prosthetic heart valve implantation. Catheter Cardiovasc Interv 2006;68:199 –204.

11. Nashef SA, Roques F, Hammill BG, et al. Validation of European System for Cardiac Operative Risk Evaluation (EuroSCORE) in North American cardiac surgery. Eur J Cardiothorac Surg 2002;22: 101–5.

12. Plack RH, Porterfield JK, Brinker JA. Complete heart block develop-ing durdevelop-ing aortic valvuloplasty. Chest 1989;96:1201–3.

13. Massoure PL, Kereun E, Chevalier JM, et al. [Severity of aortic ring abscess complicated by cardiac conduction abnormalities]. Ann Cardiol Angeiol (Paris) 2005;54:132–7.

14. Gougeon F. Complete heart block associated with the AMPLATZER membranous VSD Occluder. Plymouth, MN: AGA Medical, Advisory Notice, 2006.

15. Koplan BA, Stevenson WG, Epstein LM, Aranki SF, Maisel WH. Development and validation of a simple risk score to predict the need for permanent pacing after cardiac valve surgery. J Am Coll Cardiol 2003;41:795– 801.

16. Ben Ameur Y, Baraket F, Longo S, et al. [Conductive disorders following open-heart valvular surgery. Concerning 230 operated pa-tients.] Ann Cardiol Angeiol (Paris) 2006;55:140 –3.

Figure

Figure 1. Photographs of the Interventricular Septum in a Patient Who Developed New Atrioventricular Block After Transcatheter Aortic Valve Implantation

References

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