TAVR-Induced Left Bundle Branch Block Heightens Mortality Risk

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All-cause mortality after transcatheter aortic valve replacement (TAVR) is higher in patients who develop left bundle branch block (LBBB), seen in up to one-third of cases, according to findings published online July 12, 2012, ahead of print in Circulation.

For the Dutch registry study, Frits W. Prinzen, PhD, of Maastricht University (Maastricht, The Netherlands), and colleagues collected data from 679 patients undergoing TAVR at 8 centers from November 2005 to December 2012. The CoreValve (Medtronic, Minneapolis, MN) device was used in 57% of patients (n = 387), while an Edwards Sapien (Edwards Lifesciences, Irvine, CA) valve was used in 43% (n = 292).

Higher Mortality with New LBBB

A third of patients (n = 233) developed new LBBB within 7 days after TAVR. At 30 days, all-cause mortality trended higher in patients with new LBBB compared with those who did not have the conduction abnormality. By 1 year, the excess mortality in patients with LBBB had become significant, and at an average 450 day total follow-up for both groups, all-cause mortality remained higher in patients with new LBBB (table 1).

Table 1. All-Cause Mortality

Multivariate analysis determined several independent predictors of all-cause mortality (table 2).

Table 2. Independent Predictors of All-Cause Mortality

The cardiovascular mortality rate was 9.4% for patients without vs. 18.0% for patients with TAVR-induced LBBB (P < 0.001).

New LBBB was observed more than 4 times as often in patients treated with CoreValve compared with the Edwards Sapien device (51.1% vs. 12.0%; P < 0.001). However, device type did not influence mortality regardless of LBBB status.

‘Nascent Technology’ Needs Improvement

In an e-mail communication with TCTMD, Dr. Prinzen said that although he expected LBBB to cause adverse effects, he originally underestimated the condition’s actual impact. “The large effect on mortality probably has to do with the fragile patient population,” he said. “The data indicate that if a patient develops LBBB upon [TAVR], the survival benefit of [TAVR] has disappeared.”

Since the exact cause of LBBB is unclear, Dr. Prinzen suggested that future prospective studies focus on both risk factors for the complication and the exact cause of death. In addition, he stressed the need for greater awareness about LBBB among operators and device makers.

“I think that if LBBB is recognized, [improved] training of implanters may lead to less LBBB. Furthermore, I hope that vendors may be stimulated to develop better delivery systems,” Dr. Prinzen observed, adding that since the study showed the “danger of LBBB is independent of device type,” this will play a part in the introduction and integration of future devices as well.

In an accompanying editorial, Frederick G. P. Welt, MS, MD, of Brigham and Women’s Hospital (Boston, MA), and colleagues write that findings such as these “are a constant reminder of the knowledge gaps present in this relatively nascent technology now being applied to an increasingly sick and complex patient population. This and other issues are unlikely to be resolved without eventually conducting further investigations including randomized, head-to-head trials of devices.”

Don’t Jump to Conclusions

What will “undoubtedly . . . receive the most interest is the fact that there was a much higher incidence of induced LBBB among patients treated” with CoreValve compared with the Sapien device, Dr. Welt and colleagues comment.

An “obvious conclusion, but potentially incorrect, is to assume that this represents a sign of superiority of one device over the other,” they note. However, since the study cannot answer that question, “there are likely significant differences in clinical performance of the valves that follow from their different materials, design, and methods of insertion.”

In addition, the editorial states that the CoreValve learning curve contributes to LBBB incidence, and thus perhaps “the valve itself may not be the predominant cause of conduction system defects but rather the method of insertion.”

This is “an issue that needs to be clarified more for cardiologists going forward as to how devices are chosen for specific patients,” Peter C. Block, MD, of Emory University School of Medicine (Atlanta, GA), told TCTMD in a telephone interview.

Though CoreValve is “a good device, I wish we could tell beforehand which patients would end up with conduction abnormalities because that may change the way we strategize what device to use for which patient,” he continued.

When the ongoing US-based CoreValve trial is completed, the US Food and Drug Administration (FDA) will carefully evaluate the results, Dr. Block observed. “Everyone is sort of holding their breath to see what will happen. The FDA is going to look very hard at costs associated with it, and if half the patients need pacemakers, that may not be something that they are very eager to support,” he concluded.

 

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Sources:
1. Houthuizen P, Van Garsse LAFM, Poels TT, et al. Left bundle branch block induced by transcatheter aortic valve implantation increases risk of death. Circulation. 2012;Epub ahead of print.

2. Welt FGP, Davidson MJ, Eisenhauer AC. The transcatheter valve revolution: Time for a compensatory pause. Circulation. 2012;Epub ahead of print.

 

• Dr. Welt reports serving on a scientific advisory board for Medtronic.

• Dr. Block reports no relevant conflicts of interest.

 

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