LBB area pacing as a bailout for failed CRT
The Geisinger group also presented and published an international multicenter study that assessed the feasibility of LBBP as a bailout when standard biventricular pacing did not work – because of inadequate coronary sinus anatomy or CRT nonresponse, defined as lack of clinical or echocardiographic improvement.
This series included 212 patients in whom CRT failed and who underwent attempted LBBP pacing. The bailout was successful in 200 patients (91%). The primary endpoint was defined as an increase in LVEF above 5% on echocardiography.
During 12-month follow-up, 61% of patients had an improvement in LVEF above 5% and nearly 30% had a “super-response,” defined as a 20% or greater increase or normalization of LVEF. Similar to the previous studies, LBBP resulted in shorter QRS duration and improved echocardiography parameters.
Am I persuaded?
I was an early adopter of His-bundle pacing. When successful, it delivered both aesthetically pleasing QRS complexes and clinical efficacy. But there were many challenges: it is technically difficult, and capture thresholds are often high at implant and get higher over time, which leads to shorter battery life.
Pacing the left bundle branch mitigates these challenges. Here, the operator approaches from the right side and screws the lead a few millimeters into the septum, so the tip of the lead can capture the left bundle or one of its branches. This allows activation of the heart’s specialized conduction system and thus synchronizes right and left ventricle contraction.
Although there is a learning curve, LBBP is technically easier than His-bundle pacing and ultimately results in far better pacing and sensing parameters. What’s more, the preferred lead for LBBP has a stellar efficacy record – over years.
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ECG after CSP showing right bundle-branch pattern in V1, rapid activation in V6, and narrow paced QRS complexes.
I have become enthralled by the gorgeous QRS complexes from LBBP. The ability to pace the heart without creating dyssynchrony infuses me with joy. I chose cardiology largely because of the beauty of the ECG.
But as a medical conservative who is cautious about unproven therapies, I have questions. How is LBBP defined? Is left septal pacing good enough, or do you need actual left bundle capture? What about long-term performance of a lead in the septum?
Biventricular pacing has set a high bar because it has been proven effective for reducing hard clinical outcomes in large randomized controlled trials.
The studies at HRS begin to answer these questions. The randomized controlled trial from China supports the notion that effective LBBP (the investigators rigorously defined left bundle capture) leads to favorable effects on cardiac contraction. The two observational studies reported similarly encouraging findings on cardiac function.
The three studies therefore tentatively support the notion that LBBP actually produces favorable cardiac performance.
Whether LBBP leads to better clinical outcomes remains uncertain. The nonrandomized comparison study, which found better hard outcomes in the CSP arm, cannot be used to infer causality. There is too much risk for selection bias.
But the LBBP bailout study does suggest that this strategy is reasonable when coronary sinus leads fail – especially since the alternative is surgical placement of an epicardial lead on the left ventricle.
At minimum, the HRS studies persuade me that LBBP will likely prevent pacing-induced cardiomyopathy. If I or a family member required a pacemaker, I’d surely want the operator to be skilled at placing a left bundle lead.
While I am confident that conduction system pacing will become a transformative advance in cardiac pacing, aesthetically pleasing ECG patterns are not enough. There remains much to learn with this nascent approach.