Download this article's Factoid in PDF (& PPT for Gold Subscribers)

Almost one-third of patients undergoing transcatheter aortic valve replacement (TAVR) with a balloon-expandable device develop new-onset left bundle branch block, although the condition resolves by hospital discharge in about two-thirds. If the conduction disturbance persists long term, however, it is associated with increased need for permanent pacemaker implantation and ventricular dysfunction, according to a study published online October 3, 2012, ahead of print in the Journal of the American College of Cardiology.

Investigators led by Josep Rodés-Cabau, MD, of Laval University (Quebec City, Canada), looked at 202 patients who underwent TAVR with the Sapien or Sapien XT balloon-expandable valve (Edwards Lifesciences; Irvine, CA) at 2 hospitals. Those with baseline ventricular conduction disturbances or previous permanent pacemaker implantation were excluded. 

New Left Bundle Block Fairly Common with Sapien  

New-onset left bundle block was seen in 61 patients (30.2%), 57 on the first ECG after the procedure and 4 more within a mean 24 ± 17 hours. An ECG at discharge showed that the left bundle block had resolved in 23 patients and persisted in 25.

At 6- to 12-month follow-up, left bundle branch block had resolved in 48% of those who had been discharged with the conduction abnormality. However, the condition remained in 36% and progressed to third-degree atrioventricular (AV) block requiring permanent pacemaker implantation in 16%. No new left bundle branch block occurred after hospital discharge.

In multivariate analysis, predictors of persistent left bundle branch block were greater ventricular depth of valve implantation and longer baseline duration of the QRS complex (indicative of ventricular depolarization) on ECG (table 1).

Table 1. Independent Predictors of Persistent Left Bundle Branch Block

 
During hospitalization, patients with new-onset left bundle branch block were more likely to progress to complete AV block and require permanent pacemaker implantation than those without the condition (13.1% vs. 4.3%; P = 0.023 for both outcomes); they also tended to remain in the hospital longer (median 8 days vs. median 7 days; P = 0.091). However, there were no differences between the groups in rates of mortality, MI, or stroke.

No Mortality Difference

At a median follow-up of 12 months, 32 patients had died, with no difference in Kaplan-Meier survival (log rank P = 0.610 for freedom from all-cause mortality) between those with or without persistent left bundle branch block. However, the overall rate of permanent pacemaker implantation was higher in patients with persistent left bundle branch block (34.2% vs. 4.3%; P = 0.001). In addition, landmark analysis showed that most of the excess pacemaker implantations in patients with the conduction disturbance occurred between 4 and 12 months after TAVR (log rank P = 0.0001). New-onset left bundle branch block was the only factor associated with permanent pacemaker implantation over the entire study period (HR 5.99; 95% CI 2.93-15.61; P < 0.001).

At 1 year, there were no sudden deaths in patients with persistent left bundle branch block who did not receive a permanent pacemaker, and rates of cardiac death and heart failure were no higher than for those without persistent block. However, patients with persistent left bundle branch block were more likely to experience syncope (16.0% vs. 0.6%; P = 0.001) or need permanent pacemaker implantation during follow-up (20.0% vs. 0.7%; P < 0.001) than those without persistent block.

After TAVR, no differences were observed in valve hemodynamics between the patients with or without persistent left bundle branch block.

However, at 1 year, the group with the condition at discharge had lower LVEF compared with patients with no or transient left block (53 ± 13% vs. 62 ± 9%; P = 0.0014). They also had worse New York Heart Association functional status (P = 0.034). In multivariate analysis, persistent left bundle branch block was the only independent predictor of decreased LVEF at 1 year (P = 0.001).

A distinctive feature of the study is that it zeroes in on the incidence of true new-onset left bundle branch block, Dr. Rodés-Cabau told TCTMD in a telephone interview. “We were meticulous in excluding patients with prior conduction abnormalities because when you mix in [those] patients, you don’t know whether [post-TAVR left block] is due to the procedure or the natural history of the patients’ disease,” he said.

According to Dr. Rodés-Cabau, TAVR literature shows that acute left bundle branch block is more common with CoreValve than the Sapien prosthesis, and is more likely to persist, although data on this are very limited. 

When Does Persistent Block Need Treatment?

Which patients with persistent left block are likely to need a permanent pacemaker remains an unsettled issue, Dr. Rodés-Cabau observed. “We need to look at those who still have left bundle block at 1-year follow-up, or who have progressed to complete AV block,” he said. It may also be helpful to perform periodic ECGs to determine if patients’ QRS complex is getting longer during follow-up. Longer duration is probably a marker for predisposition to left bundle branch block that will persist and progress over time, he explained.

Whether or not left bundle branch block has an impact on mortality also needs further study, Dr. Rodés-Cabau noted. Unlike a recent Dutch registry study (Houthuizen P, et al. Circulation; 2012;126:720-728), the current data did not yield an association with increased mortality. But this may be due to the small sample size or the length of follow-up, he suggested.

Don’t Go Deep with Implantation? 

In an accompanying editorial, Antonio Colombo, MD, and Azeem Latib, MD, of San Raffaele Hospital (Milan, Italy), write that if the current findings are confirmed in a larger series, the message to clinicians is: “Irrespective of the device implanted, we should avoid positioning the aortic prosthesis too ventricularly.”

Dr. Rodés-Cabau agreed that the deeper the prosthesis is implanted, the greater the chance of its interfering with the left bundle and the higher the risk of causing conduction problems. But he was reluctant to advise routinely trying to implant the Sapien valve in a higher position. “For one thing, that is very difficult because the Edwards valve is short,” he observed. “And if you try to implant it [in a] very aortic [position], you increase the risk of embolization, which could make the situation worse.”

The editorial also recommends that certain subgroups with persistent left bundle block or right ventricular pacing be “closely monitored and even considered for cardiac resynchronization therapy if other causes, such as prosthesis malfunction, paravalvular leak, or coronary ischemia, have been excluded.”  That includes patients:

• With pre-TAVR LV dysfunction without improvement in LVEF after the procedure
• Who continue to have symptomatic heart failure after TAVR
• With worsening LVEF on serial echocardiography

 

---

Sources:
1. Urena M, Mok M, Serra V, et al. Predictive factors and long-term clinical consequences of persistent left bundle branch block following transcatheter aortic valve implantation with a balloon-expandable valve. J Am Coll Cardiol. 2012;Epub ahead of print.

2. Colombo A, Latib A. Left bundle branch block after transcatheter aortic valve implantation: Inconsequential or a clinically important endpoint? J Am Coll Cardiol. 2012;Epub ahead of print. 

 

 

Related Stories:

• TAVR-Induced Left Bundle Branch Block Heightens Mortality Risk
• Need for Permanent Pacemaker Uncommon After Sapien Valve Implantation
• Conduction Abnormalities Rare After TAVI with Edwards Device