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Several ECG characteristics put patients at higher risk for delayed conduction disturbances after transcatheter aortic valve replacement (TAVR), two groups reported in separate studies.

According to the first, high-degree conduction defects -- namely second-degree atrioventricular (AV) block type 2, third-degree AV block, or atrial fibrillation (Afib) with bradycardia -- occurred in 7.5% of patients within 30 days of TAVR at one Danish center. The likelihood was different depending on what patients showed on a 12-lead electrocardiogram (ECG) immediately after the procedure:

• Patients in sinus rhythm without right bundle branch block (RBBB), PR interval <200 ms and QRS interval <120 ms: zero late conduction defects
• Patients in sinus rhythm without RBBB, PR interval <240 ms and QRS interval <150 ms: 4.6%
• PR interval ≥240 ms or QRS interval ≥150 ms: 13.9%
• Patients with Afib and no RBBB, QRS interval <140: 6.1%
• Patients with Afib and no RBBB, QRS interval ≥140 ms: 10.0%

"No patient in sinus rhythm with normal PR and QRS intervals on immediate post-TAVR ECG developed late high-degree conduction defects, indicating a patient population safe for early discharge in absence of other complications," concluded Troels Jørgensen, MD, of Rigshospitalet, Copenhagen University Hospital, and colleagues, writing in their study in .

"Conversely, patients with RBBB, nodal rhythm, sinus rhythm, and PR interval ≥240 ms, or LBBB [left bundle branch block] with QRS interval ≥150 ms, or Afib with LBBB and QRS interval ≥140 ms on immediate post-TAVR ECG had a high risk for late high-degree conduction defects with insufficient escape rhythm and should keep the temporary pacemaker when leaving the catheterization laboratory."

For all others, leaving the catheterization laboratory with the temporary pacemaker taken out is fine if the patients continue telemetry or daily ECG measurements, Jørgensen's group suggested.

In another single-center study, baseline RBBB and an increase in PR interval were the independent predictors of late advanced conduction disturbances that held up after multivariable adjustment. Conduction disturbances requiring permanent pacemaker placement 48 hours or more after TAVR were reported in 8.8% of patients, which was "frequent," according to Azeem Latib, of San Raffaele Scientific Institute in Milan, and colleagues.

Those showing RBBB (12.9% versus 5.3%, OR 3.56; 95% CI 1.07-11.77) and a widening in PR interval (OR 1.31 for each 10-ms increase, 95% CI 1.18-1.45) were at particularly high risk, the investigators reported in the same issue of

"A simple ECG analysis could help in detecting potentially lethal advanced conduction disturbances that could occur more than 48 hours after TAVR."

Yet there may be limitations to this approach, suggested Tamim Nazif, MD, of New York-Presbyterian Hospital/Columbia University Medical Center, and colleagues, writing in an .

"For example, studies have shown resolution of a substantial proportion of new conduction disturbances during hospitalization and the potential for recovery may not be captured by an immediate ECG. Additionally, early ECGs may not detect the impact of certain pathophysiological mechanisms of delayed conduction system injury such as tissue edema or inflammation."

What's more, the studies in this area suffer from a lack of standardized definitions for important endpoints such as "high-degree conduction disturbance," making it difficult to compare across studies, the editorial noted.

"Nevertheless, the current studies clearly build on the existing literature by confirming the occurrence of 'delayed' high-degree conduction disturbances in 7% to 9% of patients without prior permanent pacemaker after TAVR. The studies reinforce the utility of readily available 12-lead ECG parameters at different time points after TAVR in predicting 'delayed' high-degree conduction disturbances and confirm that patients with normal PR and QRS intervals are not at significant risk of subsequent, dangerous conduction disturbances."

The Danish study by Jørgensen and colleagues included 467 consecutive patients who went into TAVR without pacemakers in the years 2015 to 2017. The second study, by Latib's group, consisted of 611 consecutive patients who went into TAVR in 2009 to 2015 without a permanent pacemaker and did not receive one in the 48 hours after the procedure.

Both reports were limited by a small sample size, the research teams noted.