A Technique for Cardiac Resynchronization Therapy Using Left Bundle Branch Area and Left Ventricular Pacing

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A Technique for Cardiac Resynchronization Therapy Using Left Bundle Branch Area and Left Ventricular Pacing

Heart failure (HF) affects millions worldwide, and for patients with left bundle branch block (LBBB)—a type of abnormal heart rhythm—and reduced left ventricular (LV) function, cardiac resynchronization therapy (CRT) via biventricular pacing (BVP) is a proven treatment. BVP syncs the right and left ventricles to improve pumping efficiency, but researchers are always looking for ways to make CRT more effective.

Recently, left bundle branch area pacing (LBBAP) has emerged as a promising alternative. By pacing the left bundle branch (LBB) region beyond the block, LBBAP can narrow the heart’s electrical signal (QRS duration, QRSd) with stable energy requirements. But does combining LBBAP with traditional LV pacing work better than either alone? That’s what a team from Xinhua Hospital in Shanghai set out to test with their new technique: LBB-optimized CRT (LOT–CRT).

The LOT–CRT Technique

LOT–CRT combines two key steps to sync the heart: LBBAP (fixing the bundle branch block) and sequential LV pacing (targeting slow LV activity). Here’s how it works:

  1. Backup RV Lead: First, a defibrillator lead was placed in the right ventricle (RV) to act as a safety net in case of temporary heart block during LBBAP.
  2. LV Coronary Sinus Lead: Next, a lead was inserted into the LV via the coronary sinus (a vein on the heart’s surface), targeting areas where the LV was beating slowest—standard for CRT.
  3. LBBAP Lead: Finally, the LBBAP lead (a Medtronic SelectSecure 3830 lead) was guided into the RV septum (the wall between the heart’s lower chambers). The team used a “nine-grid system” to find the right spot and adjusted the lead’s angle: 12–1 o’clock from a right anterior oblique (RAO) view and 2–3 o’clock from a left anterior oblique (LAO) view. They monitored electrical signals, impedance (resistance), and the shape of the QRS wave to ensure proper placement.

For patients getting a CRT-defibrillator (CRTD), the LBBAP lead connected to the RV port and the LV lead to the LV port. For CRT-pacemakers (CRTP), the LV lead went first, followed by LBBAP.

Study Cohort

Five patients were included in the study:

  • 60% male (3 men, 2 women)
  • Average age: 71.8 years
  • All had cardiomyopathy (2 non-ischemic, 3 ischemic)
  • 2 had paroxysmal atrial fibrillation (AF)
  • All had hypertension
  • Baseline left ventricular ejection fraction (LVEF, a measure of pumping ability): 32.0% ± 4.2%
  • Baseline QRSd (abnormal heart rhythm marker): 158.0 ± 13.0 ms

All patients had at least one HF hospitalization in the 3 months before LBBAP and were on standard HF medications: Entresto (sacubitril/valsartan), beta-blockers, and loop diuretics.

Results

LOT–CRT was successful in all five patients. Key findings include:

  • Procedure Metrics: Average operation time: 152.0 ± 31.1 minutes. Average X-ray fluoroscopy time: 26.2 ± 5.9 minutes. Four patients received a CRTD (CRT + defibrillator), and one received a CRTP (CRT + pacemaker).
  • Stable Pacing: Both LBBAP and LV lead thresholds (energy needed to “capture” the heart muscle) stayed consistent during follow-up.
  • Narrower QRS: Unipolar LBBAP (using one electrode) narrowed QRSd to 123.0 ± 5.7 ms—a 22% reduction from baseline (P = 0.001). LOT–CRT narrowed it even more, to 119.0 ± 7.6 ms (P < 0.01 compared to baseline or BVP).
  • Improved Heart Function: After three months, LVEF jumped to 45.0% ± 5.1% (up from 32.0%), and the LV’s end-diastolic dimension (LVEDD, a measure of heart enlargement) shrank from 68.2 ± 12.3 mm to 62.2 ± 11.3 mm (P = 0.017).
  • Better Symptoms: The New York Heart Association (NYHA) class—from 1 (mild) to 4 (severe)—dropped from 3.2 ± 0.5 to 2.4 ± 0.6 (P = 0.016), meaning patients felt less short of breath and more able to perform daily activities.

During follow-up (average 296 days), no patients had lead dislodgement, infection, or stroke. The ventricular pacing rate was 99%, meaning the device was working almost constantly.

Why LOT–CRT Matters

BVP works well for many, but some patients don’t respond—often due to scar tissue in the LV, a bad LV lead spot, or ongoing electrical/mechanical dyssynchrony. LBBAP fixes LBBB but doesn’t always address intraventricular (within the LV) dyssynchrony, especially in patients with lots of scar tissue.

LOT–CRT solves this by adding the LV lead: it combines the physiologic benefits of LBBAP (fixing the bundle branch block) with the targeted resynchronization of LV pacing. For patients with ischemic cardiomyopathy—who often have more scarring—this could be a game-changer.

Limitations

The study has caveats:

  1. Time-Consuming: The procedure took longer (152 minutes) and used more fluoroscopy (26 minutes) than some previous LBBAP studies.
  2. Small Sample: Only five patients were included, all from one center.
  3. Short Follow-Up: Most data is from three months—long-term outcomes need more research.
  4. Few Ischemic Patients: Only three of five had ischemic cardiomyopathy, so results may not apply broadly to this group.

Conclusion

Despite its limitations, this study shows LOT–CRT is feasible and effective for patients with HF, LBBB, and reduced LV function. The combo of LBBAP and LV pacing narrowed QRSd more than either alone, improved heart function, and made patients feel better. For doctors, this could mean a new tool to help the hardest-to-treat HF patients—especially those with scar tissue or incomplete response to standard CRT.

This study was conducted by Xiang-Fei Feng, Rui Zhang, Mei Yang, Bo Liu, Ya-Qin Han, Qiu-Fen Lu, and Yi-Gang Li from the Department of Cardiology at Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University. It was published in the Chinese Medical Journal in 2021.

doi: https://doi.org/10.1097/CM9.0000000000001622

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