Persistent LBBB Following TAVI Linked With Adverse Outcomes

October 11, 2012

October 10, 2012 (Baltimore, Maryland) — One in three patients who undergo transcatheter aortic-valve implantation (TAVI) with a balloon-expandable valve develop left bundle branch block (LBBB), a new analysis shows [1]. LBBB resolved at discharge in more than one-third of these patients and in nearly 60% of patients at one-year follow-up, but persistent LBBB was associated with higher risks of syncope, complete heart block, and the need for a permanent pacemaker implantation (PPMI).

"This study showed that the occurrence of new-onset, persistent LBBB following TAVI is associated with a much higher risk for complete atrioventricular block [AVB] requiring [PPMI]," according to lead researcher Dr Marina Urena (Laval University, Quebec City) and colleagues. "It is of high clinical relevance that the higher risk for complete AVB started very soon (hours to days) after the appearance of LBBB and continued during the follow-up period in those patients with persistent LBBB."

Speaking with heartwire , senior researcher Dr Josep Rodés-Cabau (Laval University) said the risk of LBBB with TAVI has always been known, but the prognostic significance of LBBB was not entirely understood, particularly in patients with no previously known conduction abnormalities.

"We know that with the balloon-expandable valve, a significant number of these conduction abnormalities will disappear in hours or days following the procedure," said Rodés-Cabau. "These cases of transient left bundle branch block do not seem to have a deleterious effect on clinical outcomes. But when patients leave the hospital with a left bundle branch block, this is where a number of patients will progress to complete AV block. Also, some patients who end the procedure with left bundle branch block will progress to complete AV block in the next couple of hours or even days. So for some patients, the left bundle branch block is not benign."

The results of the study are published online October 3, 2012 in the Journal of the American College of Cardiology.

Transient LBBB vs Not-So-Benign LBBB

The analysis included 202 consecutive patients with no baseline ventricular conduction disturbances or previous permanent pacemaker implantations; all underwent TAVI with a balloon-expandable aortic valve (Sapien or Sapien XT, Edwards Lifesciences). The average age of the treated patients was 80 years, and 60% were female. In total, 117 underwent TAVI with the transapical approach while 85 were treated via the transfemoral artery.

New-onset LBBB was documented in 61 patients (30.2%) during the hospitalization period. At discharge, LBBB was resolved in 37.7% of patients and in 57.3% of patients at six- to 12-month follow-up. Among patients with persistent LBBB at hospital discharge, four patients required a permanent pacemaker because of third-degree AVB. In a multivariable-adjusted analysis, the depth of prosthesis in the ventricle (odds ratio [OR] 1.37 for each 1-mm increase; p=0.017) and baseline QRS duration (OR 1.24 for each 4-ms increase; p=0.037) were associated with an increased risk of LBBB.

In terms of the prognostic implications, patients with persistent LBBB at hospital discharge had a 4.75% decrease in LVEF at one-year follow-up, while those with transient or no LBBB at discharge had a 2.52% increase in LVEF (p=0.001 between groups). In addition, the rate of PPMI was higher in patients with persistent LBBB compared with the rest of the cohort. Among the 25 patients with persistent LBBB at discharge, 20% required a pacemaker (vs 0.7% in the rest of the cohort; p=0.001) and 16% developed syncope (vs 0.7% in the rest of the cohort; p=0.001). Patients with persistent LBBB at discharge also had a poorer NYHA functional class compared with patients with transient or no LBBB.

Risk of Valve Embolization

In an editorial [2], Drs Antonio Colombo and Azeem Latib (EMO-GVM Centro Cuore Columbus, Milan, Italy) note that the depth of valve implantation was identified in the present study as a predictor of LBBB, an unsurprising finding given the close relationship between the annulus and the left bundle branch. As a result, physicians should avoid implanting the device too ventricularly. "Patients with new-onset LBBB post-TAVI should also be kept on continuous electrocardiographic monitoring while in the hospital, and those discharged with persistent LBBB should have regular Holter monitoring," write Colombo and Latib.

In addition, there are other subgroups, including patients with pre-TAVI left ventricular dysfunction without improvement in the ejection fraction post-TAVI, those with symptomatic heart failure post-TAVI, and those with worsening ejection fractions on serial echocardiography, who "should 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," state Colombo and Latib.

To heartwire , Rodés-Cabau said that eliminating LBBB is a challenge when dealing with balloon-expandable valves. When the valve is implanted and positioned, there is no chance to remove the valve if it is positioned incorrectly. While the depth of the valve in the ventricle was associated with an increased risk of LBBB, he said that there is a risk of valve embolization if the aortic valve is positioned higher, an outcome that is worse than the onset of a conduction abnormality, said Rodés-Cabau.

"What we're seeing here is that patients with left bundle branch block need closer follow-up, and there will be a need to repeat the ECG to see if there is any progression or maybe even use of a Holter monitor," he said. "This being said, I don't think we should be thinking about implanting a pacemaker in all the patients with left bundle branch block. At the moment, at least in patients with the balloon-expandable valve, the left bundle branch block disappears within six months to a year in a significant number of patients. The trouble is, at this moment, we don't know what factors are associated with this late recovery."

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