Conduction system abnormalities after transcatheter aortic valve replacement mechanism, prediction, and management.
- 2. Introduction Aortic stenosis (AS) is a common form of valvular heart disease, the global burden of which continues to increase. Untreated, severe symptomatic AS carries a high mortality rate. Initially performed in patients deemed unsuitable for surgery, and then advancing to become an option for patients with high, intermediate, and now low operative risk, TAVR has revolutionized the treatment of symptomatic severe AS . TAVR is noninferior to surgical aortic valve replacement (SAVR) with regard to mortality at 1 year
- 3. TAVR Devices Currently, the 2 TAVR devices in clinical use in the United States are Sapien (Edwards Lifesciences, Irvine, CA, USA) Evolut (Medtronic, Santa Rosa, CA, USA): Evolut is a self-expanding, porcine pericardial tissue valve with a nitinol frame that is anchored in the supravalvular/supra- annular position. The lower portion of the Medtronic system sits in the left ventricular outflow tract (LVOT) and exerts a higher radial force. Evolut Pro: The latest generation of this transcatheter valve is similar in design and implantation to the Evolut R, but has an outer wrap of porcine pericardium to help minimize perivalvular leak Sapien 3 valve is a balloon-expandable system with bovine pericardial tissue leaflets, a cobaltchromium frame, and lower fabric skirt that sits in the intravalvular position
- 4. Most common Indications for PPM implantation in patients undergoing TAVR Complete atrioventricular (AV) block Second-degree type II AV block Sick sinus syndrome Left bundle branch block (LBBB) with first-degree AV block Atrial fibrillation with slow response/complete AV block Alternating right bundle branch block (RBBB)/LBBB Sinus bradycardia
- 5. PPM implantation Rate The rates of post-TAVR conduction abnormalities requiring a PPM range from 4.3% to 43% with self-expanding valves associated with a higher rates of PPM implantation than balloon-expandable valves. Newer valve systems having lower rates than earlier generation valves Self-expanding CoreValve Evolut R has a PPM rate of 14.7% to 17.4% Sapien 3 has a PPM rate of 6.5% to 12.3% with optimal positioning Newest generation Evolut Pro valve seems to have similar rates of PPM implantation as the Evolut R
- 6. MECHANISMS OF CONDUCTION ABNORMALITIES FOLLOWING TAVR There is heterogeneity in the location of the AV node, with 50% of patients exhibiting a predominantly right-sided AV node, 30% with a left-sided orientation, and the remaining 20% of patients with an AV node running under the membranous septum just below the endocardium. The latter 2 anatomic variants may predispose patients to increased risk of conduction abnormalities following TAVR The left bundle branch emerges from beneath the membranous septum and is located within the interventricular septum, close to the base of the interleaflet triangle that separates the noncoronary and the right coronary leaflets of the aortic valve. This relationship of the left bundle to the aortic root explains why LBBB is the most common conduction system abnormality following TAVR, as the valve itself can exert direct pressure on the conduction system
- 7. Spatial relationship between the 3 cusps of the aortic valve and the zone where the left bundle branch emerges beneath the membranous septum
- 8. MECHANISMS OF CONDUCTION ABNORMALITIES FOLLOWING TAVR If LBBB does occur post-TAVR, it appears before hospital discharge in most cases, and increases the risk of PPM implantation It does not appear to increase overall mortality in some studies, although the data are conflicting, as other studies have suggested an increase in mortality with LBBB post- TAVR
- 9. PREDICTION OF CONDUCTION SYSTEM ABNORMALITIES POST TARV Preprocedural patient characteristics and peri-procedural considerations are important predictors for conduction system abnormalities following TAVR. In a large meta-analysis that included a mix of balloon-expandable and self-expanding systems implanted predominantly via the transfemoral approach, male sex, preprocedural electrocardiographic abnormalities including first-degree AV block, left anterior hemiblock, and RBBB were significantly associated with the need for PPM. The presence of AV block during the procedure and the use of the self-expanding prosthesis were also associated with an increased need for PPM.
- 10. PREDICTION OF CONDUCTION SYSTEM ABNORMALITIES POST TARV In an analysis of 9785 patients undergoing TAVR across 229 sites in the United States between 2011 and 2014 as part of the Society of Thoracic Surgeons (STS)/American College of Cardiology Transcatheter Valve Therapy Registry, patient characteristics associated with higher rates of PPM included increasing age, higher STS Predicted Risk of Operative Mortality score, previous aortic valve procedures, chronic lung disease, and the need for home oxygen. Electrocardiographic, anatomic, and procedural characteristics associated with an increased need for PPM were conduction defects on the preprocedural electrocardiogram, larger aortic annulus size and valve area, need for a larger prosthesis, and the use of valve oversizing Preoperative atrial fibrillation, left-posterior hemiblock, LBBB, and ejection fraction were not associated with the need for PPM
- 11. Recent studies have also implicated post TAVR balloon dilation, a method used to treat insufficiently expanded valves and/or significant perivalvular leak, as a significant predictor of PPM. This same study also found PR prolongation greater than 178 ms post-TAVR as an important risk factor for PPM. Depth of the prosthesis within the LVOT, as measured by the mean distance from the annular margin of the noncoronary cusp to the ventricular end of the prosthesis on computed tomography, is a significant predictor of PPM implantation. Patients requiring a PPM had a mean depth of 9.7 + 4.1 mm, compared with versus 6.3 + 3.4 mm among patients who did not require a PPM PREDICTION OF CONDUCTION SYSTEM ABNORMALITIES POST TARV
- 12. Most conduction system problems following TAVR occur within the first 48 hours after the procedure. However, a minority of patients may develop late conduction disease. RBBB and an increase in the PR interval have been identified as independent predictors of delayed advanced conduction disturbances requiring PPM. Preexisting RBBB has been shown to be a predictor of increased cardiovascular mortality after TAVR as well, and hence such patients need careful follow-up surveillance post-TAVR.
- 13. MANAGEMENT AND CLINICAL IMPLICATIONS The duration of the PR interval has been shown to peak on post-TAVR days 4 to 6 and the QRS duration on days 7 to 9. Increased PR interval and preexisting RBBB are reliable predictors of the long-term need for pacing, whereas LBBB and QRS width is not. In the PARTNER registry, the mean time to PPM implantation was 4.1 days. Even among patients who experience high-degree AV block following TAVR, electrical recovery can eventually occur in 22% to 56% of patients. Increased PR interval and preexisting RBBB are reliable predictors of the long-term need for pacing, whereas LBBB and QRS width is not. In patients without a preexisting bundle branch block or PPM, new RBBB or PPM implantation was associated with increased all-cause mortality greater than 1 year from TAVR implantation Development of either condition was also associated with an increased risk of heart failure hospitalization and reduced left ventricular ejection fraction New LBBB with reduced left ventricular ejection fraction has been implicated in an increased risk of sudden death after TAVR
- 14. Additional Testing and Practical Considerations Electrophysiology studies can also be helpful in determining the need for PPM post-TAVR. Ideally, an electrophysiology study would be able to identify those patients who do not require long-term ventricular pacing.
- 15. A proposed decision-making algorithm for permanent pacemaker implantation following TAVR
- 16. Pacing Modes and Pacemaker Types Recent studies suggest that the type of pacing used in post-TAVR patients may be important. In a multicenter study involving 1621 patients who underwent TAVR, of whom 16.4% received a PPM, a retrospective analysis was undertaken to determine the effect of various pacing programming modes on clinical outcomes. During a follow-up period of 13 months, 53% of patients were pacemaker dependent (defined as the absence or inadequate ventricular rhythm >95% of the time on pacemaker interrogation). Conventional dual-chamber pacing (DDD) mode was associated with higher rates of pacemaker dependency compared with other modes aimed at optimizing native conduction (namely AAI/DDD or VVI modes).
- 17. Pacing Modes and Pacemaker Types Heart failure hospitalizations were significantly increased in the DDD group (81.8% vs 54.6%, P = .03), and there was a trend to increased overall mortality in this group (73% vs 96%, P = .06) Along with pacing modes aimed at encouraging native conduction, cardiac resynchronization therapy or His-bundle pacing may be options for reducing the risk of heart failure in patients undergoing TAVR who require a PPM Cardiac resynchronization therapy should be considered for patients with a reduced ejection fraction who will have a high pacer burden and a wide LBBB Leadless pacemakers may be an option for elderly or frail patients in whom dual-chamber pacing is not required and who may not have a high pacemaker burden
- 18. KEY POINTS Conduction abnormalities are common following transcatheter aortic valve replacement (TAVR), as the anatomy of the left ventricular and aortic outflow tracts predispose to damage to the conduction system during and after the procedure. Patient factors, procedural characteristics, and the type of valve used during TAVR all contribute to the need for permanent pacemaker. Careful monitoring of patients post-TAVR can help identify the patients who will require a pacemaker and minimize potential deleterious effects. A decision-making algorithm incorporating preexisting conduction abnormalities and electrophysiology testing may improve the appropriate use of permanent pacemakers post-TAVR.
- 19. Thank You