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SAN FRANCISCO -- Better indicators of high-grade atrioventricular (AV) conduction system abnormalities following transcatheter aortic valve replacement (TAVR) could be gleaned from an intraprocedural electrophysiologic (EP) study, researchers found.

In the prospective EPS/TAVR study of Sapien-dominant TAVR recipients at one center, baseline right bundle branch block (RBBB) on ECG turned out to be a strong predictor of heart block during TAVR hospitalization but not after discharge, whereas a post-TAVR PR interval >300 msec predicted both early and late blocks. New-onset left bundle branch block (LBBB) was not predictive at all.

More promising were the strong EP predictors of complete heart block (CHB) after discharge that were identified:

• Post-TAVR HV interval

• Baseline AH interval

• Post-AH interval

• Baseline AV Wenckebach cycle length

• Post-TAVR AV Wenckebach cycle length

All are indicators of altered AV node and His bundle function after TAVR, the study showed.

Meanwhile, anatomic and procedural variables at best provided fairly weak predictors of delayed CHB, Alfred Buxton, MD, of Beth Israel Deaconess Medical Center in Boston, reported at the Transcatheter Cardiovascular Therapeutics (TCT) meeting here, hosted by the Cardiovascular Research Foundation.

For the research, an EP study was performed before and after each of 399 TAVR cases at Buxton's institution. In each EP study, structural valve operators placed electrode catheters -- first pacing the right atrium (RA), then positioned for His bundle electrography, and finally moved to the right ventricle for pacing as well as retrograde conduction assessment -- under guidance of an electrophysiologist.

The electrophysiologist monitored ECG and intracardiac electrograms continuously during TAVR. Any people found to have a conduction abnormality stayed overnight in the hospital and were discharged with 2 weeks of mobile cardiac telemetry.

"His bundle recordings can be performed by interventional cardiologists and appear useful to predict risk for AV block," Buxton told the TCT audience. He nevertheless acknowledged the learning curve for structural colleagues not used to placing His catheters.

Session discussant Tamim Nazif, MD, of NewYork-Presbyterian Columbia University Irving Medical Center in New York City, called these EP studies during TAVR a "Herculean" effort, given logistic barriers such as the availability of appropriate physicians and equipment.

He said he hoped that the "robust mechanistic data" from Buxton's group may improve the ability to risk-stratify TAVR candidates. Not being able to predict late AV conduction system abnormalities is "the main barrier to early discharge," he said.

For a normal heart rhythm, an electric signal travels from AV node, down to the bundle of His, then proceeds through the right or left bundle branch, headed toward each respective ventricle.

CHB, a condition where the electrical signal can't pass normally from the atria to the ventricles, is a common complication of TAVR. This can occur due to damage to the atrioventricular (AV) node. Although an implanted pacemaker can restore normal rhythm, CHB is nevertheless associated with .

Buxton acknowledged that the EP parameters identified as predictive of late heart block had negative predictive value (NPV) far exceeding their "unacceptably low" predictive positive value (PPV). For example, a post-TAVR HV interval of at least 80 ms carried an NPV of 0.96 for ruling out late heart block, but only a 0.12 PPV for finding a case.

"This is obviously not something that's ready for prime time," he said. "I'm not recommending that this should be done universally, but with people that have markers that ... may predict increased risk of AV conduction abnormalities."

At a press conference, a study collaborator of Buxton endorsed an existing right atrial pacing strategy to predict need for new permanent pacemakers after TAVR. "The easiest thing for interventional cardiologists," suggested Roger Laham, MD, also of Beth Israel Deaconess Medical Center, is to put the temporary pacemaker in the RA and pace and watch for Wenckebach AV block, an indicator of risk.

The EPS/TAVR study covers consecutive patients who underwent TAVR at Buxton's institution from May 2021 to March 2023. Investigators excluded people with pre-existing pacemakers or implantable cardioverter-defibrillators.

The 399 participants had a mean age of 78.4 years, and 56% were men. Baseline atrial fibrillation was recorded in 11%, an elongated PR interval in 24%, LBBB in 5%, RBBB in 12%, and left ventricular hypertrophy in 24%. Bicuspid anatomy was noted in 15%.

TAVR was performed with the balloon-expandable Sapien 3 valve in 357 people, and self-expanding Evolut in 42. Valve-in-valve procedures reached 36.

There were 60 individuals who had CHB or other AV conduction abnormalities peri-procedure, most of them resolving quickly so that only 26 people were left with AV block at the end of TAVR. One person had had a 2:1 infra-nodal block prior to catheter placement.

Buxton reported that 20 people had a new permanent pacemaker by the end of their index TAVR hospitalization. Another 20 had delayed CHB or Mobitz 2 after discharge and received a pacemaker a median 4 days after TAVR. Five people in total died, classified as one periprocedural death plus four late deaths at a median 14 months.

Nazif said the findings that new-onset LBBB and pre-existing RBBB are not predictive of delayed CHB should be interpreted with caution, given the limited sample in the report. Prior studies had shown that these ECG variables are associated not just with pacemakers but mortality as well, he noted.

Nazif suggested that the EPS/TAVR study findings be verified in TAVR with self-expanding valves.

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