AV Block and PPM Implantation in TAVR

Introduction

Aortic stenosis (AS) is the most common form of valvular heart disease.1,2 With an aging global population, especially in Europe and North America, the disease burden is expected to increase. Current estimates suggest a prevalence of severe AS of 3.4% in patients aged 75 years or older.3 In a recent modelling study, there were an estimated 189,836 and 102,558 candidates suitable for transcatheter aortic valve replacement (TAVR) in Europe and North America, respectively.3 Since its advent, complications associated with TAVR such as paravalvular leak, vascular injury, stroke, and conduction abnormalities have markedly decreased as a result of increased operator experience and volume,4 improved patient selection based on improved imaging techniques, and technical improvements in valve prostheses and delivery systems.5 The indications for TAVR have also expanded to include intermediate-risk patients, with ongoing trials to assess suitability for low-risk patients. A recent focused update to the American Heart Association and American College of Cardiology joint guidelines for valvular heart disease have designated a Class I recommendation for TAVR in prohibitive and high-risk surgical candidates and Class IIa recommendation for intermediate-risk candidates with AS.6 In time, TAVR may become first-line therapy for all patients with AS, especially if the associated complications can be further reduced. TAVR-related rates of conduction abnormalities, including complete heart block necessitating a permanent pacemaker (PPM) implantation, remain significantly higher than for surgical aortic valve replacement (SAVR) and may limit further expansion of this procedure.

Magnitude of the Problem

Post-TAVR conduction abnormalities resulting in PPM implantation range from 6.0% for the Edwards SAPIEN (Edwards Lifesciences; Irvine, CA) balloon-expandable valve (BEV) to 25% for the Medtronic CoreValve (Medtronic, Inc.; Minneapolis, MN) self-expanding valve (SEV).7-11 Recently, the 2016 annual Report of the Transcatheter Valve Therapy registry12 reported an incidence of 12% of post-TAVR PPM implantation in 2015; the incidence was 3 times higher in the SEV versus BEV.7-11 The current generation Edwards SAPIEN 3 (Edwards Lifesciences; Irvine, CA) BEV and the Medtronic Evolut R (Medtronic, Inc.; Minneapolis, MN) SEV have reduced this PPM implantation rate by 30-50% (from 25.8% to 11.7% for SEV).8,13-16 Recently, the Evolut PRO (Medtronic, Inc.; Minneapolis, MN) SEV clinical study presented at the American College of Cardiology 2017 Annual Scientific Sessions met its primary endpoint at 30 days with a PPM implantation rate of 10% with excellent valve hemodynamics and survival, gaining it U.S. Food and Drug Administration approval.17 The differences between these two valves are attributed to differences in stent design, ideal depth of implantation for each valve type, and the radial force exerted on the tissue, especially in the left ventricular outflow tract (LVOT), all of which have the potential to injure the conduction system.18 The PARTNER 2 (Placement of Aortic Transcatheter Valves) trial gives us data comparing the SAPIEN XT (Edwards Lifesciences; Irvine, CA) BEV and SAVR in intermediate-risk surgical candidates, with 30-day rates of PPM implantation of 8.5% and 6.9%, respectively (p = 0.17).19 In the CoreValve US Pivotal Trial that compared the CoreValve (Medtronic, Inc.; Minneapolis, MN) SEV and SAVR in high-risk surgical candidates, 30-day PPM implantation rates were 19.8% and 7.1%, respectively (p < 0.001).20 The SURTAVI (Surgical Replacement and Transcatheter Aortic Valve Implantation) trial comparing CoreValve (Medtronic, Inc.; Minneapolis, MN) SEV and SAVR in intermediate risk surgical candidates showed 30-day PPM implantation rates of 25.9% and 6.6%, respectively, but, importantly, showed no differences in 24-month mortality in patients who underwent PPM implantation.21

Indications, Timing, and Long-Term PPM Dependence After TAVR

The majority of cases of PPM implantation post-TAVR are due to complete22 or high-degree atrioventricular (AV) block (>80%).23 About half of incidences of PPM implantation in the PARTNER trial and registry were within 48 hours of the procedure, 86% within a week, and almost all of them (97.1%) in the index hospitalization, with only 1.9% of patients receiving a PPM in 1 year.23,24 Urena et al.24 reported a median time of PPM implantation of 3 days, with approximately 90% of implantations within a week. More than a third of patients who received a PPM did not show pacing activity at 6- and 12-month follow-up, and this was >50% in BEV group. Other studies have shown similar pacing independence of 55.6% at 11.5 months after SEV25 and conduction recovery in 69% of patients at a mean follow-up of 234 days.26

How Does This Affect Our Patients

Although the increase in cost, the PPM implantation procedure, and having a permanent implantable device are obvious additional associated morbidities, a recent retrospective study by Fadahunsi et al.27 of patients from the Transcatheter Valve Therapy registry and CMS database showed a 31% increase in risk of 1-year mortality and 33% increase in risk of a composite of mortality and heart failure (HF) admissions at 1 year in patients who underwent PPM implantation. A study by Nazif et al.23 on patients from the PARTNER trial showed a similar morbidity associated with PPM implantation. Biner et al.28 conducted a hemodynamic study suggesting that PPM implantation may have a negative impact on left ventricular ejection fraction (LVEF) (-0.9 ± 8.7% vs. 2.3 ± 10.8%, p = 0.03) and left ventricular (LV) unloading (LV stroke volume -2 ± 16 vs. 4 ± 10 ml/m2, p = 0.015), even though it did not affect 2-year clinical outcomes. Other studies have shown new PPM implantation to be an independent predictor of LVEF decrease at 6- and 12-month follow-up24 (Table 1). Conduction recovery and pacemaker independence in more than half of the patients at 1 year after balloon expandable TAVR23 begs the question of which patients are at risk of persistent, versus transient, high-grade or complete AV block.

Predictors and Risk Stratification of PPM Implantation

SAVR can result in AV conduction disturbances, likely due to removal of the native valve and peri-valve tissue, sutures in proximity to the membranous septum, and the ensuing edema. Although TAVR is not associated with these issues, the procedure has its own particular risks for damage to the conduction system.

Predictors of post-TAVR PPM implantation can be divided in to electrocardiographic, patient, and procedural factors (Table 2). The mechanism of AV block is likely due to direct injury of the His bundle given its close relation to the membranous septum and native aortic valve.29-31 Preexisting right bundle branch block (RBBB), low depth of implantation, and use of SEV have been identified as the most common and consistent risk factors for PPM implantation across multiple studies.23,32-38 Positioning of the SEV lower in the LVOT compared with the BEV results in the potential for more damage to the AV node and left bundle branches. A recent study by Mauri et al.39 of the latest generation SAPIEN 3 (Edwards Lifesciences; Irvine, CA) BEV also identified calcium volume in the LVOT in the area below the left and right coronary cusps as another independent risk factor for PPM implantation.

New hypothesis-generating studies offer more ways to risk stratify individuals. For example, need for PPM implantation based on surface and intracardiac electrocardiographic characteristics has been suggested in a study conducted by Rivard et al.,40 in which they found a delta-HV interval ≥13 ms and an HV interval ≥65 ms in new onset left bundle branch block after TAVR to be predictive of AV block after TAVR and proposed a clinical decision-making algorithm. Hamdan et al.41 suggest that a short membranous septum may confer additional risk for heart block and pre-implantation computed tomography screening may identify at-risk individuals. Furthermore, the study by Naveh et al.42 showed that pre-existing RBBB, baseline PR interval, post-TAVR PR interval, and change in PR interval from baseline are reliable predictors of long-term PPM dependency.

Our Recommendations

For all patients, but especially intermediate-risk patients, a thorough discussion of post-TAVR PPM implantation risk is necessary. We propose careful screening of at-risk individuals, with preexisting RBBB and a heavily calcified LVOT most predictive of the need for post-TAVR PPM implantation. Procedural factors that may reduce PPM implantation rates include a high depth of implantation and use of a BEV in high-risk individuals. Innovations in design may reduce PPM rates in the future.

The 2013 European Society of Cardiology guidelines recommend a period of clinical observation up to 7 days for recovery before proceeding with PPM implantation in patients with persistent high degree or complete AV block post-surgery or post-TAVR in order to assess whether the conduction disturbance is transient or permanent (Class I recommendation; Level of Evidence C).43 However, the length of observation must be balanced with the importance and desire to ambulate and discharge patients expeditiously post-procedure. In patients with transient high-degree AV block or a new left bundle branch block, short-term mobile outpatient rhythm monitoring, along with avoidance of AV-nodal-blocking agents, might be indicated upon hospital discharge, with close follow-up for conduction recovery. With current knowledge and technology, it might still be justified to implant a PPM in patients who develop complete heart block because the median time to recovery might take several months.

Further prospective studies are needed to more precisely define the patients who actually require PPM implantation post-TAVR, utilizing patient characteristics both pre- and post-procedure as well as type of valve prosthesis implanted. Until more data are available, guideline-directed medical therapy according to the most recent guidelines for cardiac pacing should be followed.43 With BEV now showing a PPM incidence almost equal to surgery and SEV incidence dropping rapidly with the new Evolut PRO (Medtronic, Inc.; Minneapolis, MN) data, all indications point toward improvements in technology eventually making this dilemma of historical interest only.

Table 1: Long-Term Outcomes of PPM Implantation Post-TAVR

Author (Year)Ref (Number of Patients)

Valve Type      

% Patients Requiring PPM

Follow-Up Duration

Significant Outcomes

Biner (2014)28
n = 230

BEV = 13%
SEV = 87%

Total = 25%
BEV = 10%
SEV = 27%

2 years

At 6 months:

  • Attenuated improvement in LVEF
  • LV stroke volume
  • Smaller reduction in systolic pulmonary artery pressure
  • Deterioration of right ventricular index of myocardial performance

Fadahunsi (2016)27
n = 9785

BEV = 88.27%
SEV = 11.2%

Total = 6.7%
BEV = 4.3%
SEV = 25.1%

 

At 1 year:

  • Higher cumulative incidence of HF admission, mortality, composite of mortality or HF admission

Urena (2014)24
n = 1556

BEV = 55.14%
SEV = 44.85%

Total = 15.4%
BEV = 7.1%
SEV = 25.5%

1.83 years

At 30 days:

  • Lower rate of sudden cardiac/unknown death was observed in patients with PPM implantation

Nazif (2015)23
n = 1973

BEV

Total = 8.8%

 

At 1 year:

  • PPM implantation was associated with significantly higher repeat hospitalization and mortality or repeat hospitalization

Kawaguchi (2015)44
n = 160

BEV = 33.75%
SEV = 66.25%

Total = 17.5%
BEV = 7.4%
SEV = 22.6%

3 years

No difference in outcomes

Mouillet (2015)45
n = 833

SEV

30.2%

0.66 years

No difference in outcomes

Schymik (2015)46
n = 793

BEV
SEV

17.4%

1 year

No difference in outcomes

Pereira (2013)47
n = 58

SEV

32.8%

1 year

No difference in outcomes

Buellesfeld (2012)48
n = 305

BEV = 10.5%
SEV = 89.5%

Total = 32.1%
BEV = 34%
SEV = 15.6%

1 year

No difference in outcomes

De Carlo (2012)34
n = 275

SEV

24%

1 year

No difference in outcomes

Reardon (2017)21
n = 864

SEV

25.9%

2 years

No difference in mortality

Table 2: Predictors of PPM Implantation Post-TAVR

Author (Year)Ref
(Number of Patients)

Valve Type      

% Patients Requiring PPM

Predictors

Bagur (2012)36
n = 411

BEV

7.3%

  • Pre-existing RBBB

Ledwoch (2013)33
n = 1147

BEV
SEV

33.7%

  • Absence of prior valve surgery
  • Use of SEV
  • Porcelain aorta

Khawaja (2011)49
n = 243

SEV

33.3%

  • Periprocedural AV block
  • Balloon predilatation
  • Larger 29 mm prosthesis
  • Interventricular septum diameter
  • Prolonged QRS duration

De Carlo (2012)34
n = 275

SEV

24%

  • Depth of implantation
  • Pre-existing RBBB
  • Pre-existing left anterior fascicular block
  • Longer PR at baseline

Munoz-Garcia (2012)32
n = 174

SEV

27.6%

  • Depth of prosthesis in LVOT
  • Pre-existing RBBB
  • Traditional delivery system

Calvi (2012)37
n = 181

SEV

28.7%

  • Pre-existing RBBB

Nazif (2015)23
n = 1973

BEV

8.8%

  • Pre-existing RBBB
  • Prosthesis diameter/LVOT diameter (for each 0.1 increment, odds ratio: 1.29, 95% confidence interval: 1.10-1.51, p = 0.002)
  • LV end-diastolic diameter (for each 1 cm, odds ratio: 0.68, 95% confidence interval: 0.53-0.87, p = 0.003)
  • Treatment in continued access registry

Fadahunsi (2016)27
n = 9785

BEV = 88.27%
SEV = 11.2%

Total = 6.7%
BEV = 4.3%
SEV = 25.1%

  • Age
  • Prior conduction defect
  • Use of SEV

Mauri (2016)39
n = 229

BEV

14.4%

  • Pre-existing RBBB
  • Depth of implantation
  • LVOT right coronary cusp calcification
  • LVOT left coronary cusp calcification

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