Biventricular endocardial pacing was superior to epicardial pacing in ischemic patients with poor cardiac resynchronization therapy (CRT), according to research published in JACC: Clinical Electrophysiology.

Jonathan M. Behar, MBBS, of the Department of Imaging Sciences, King’s College London & Guy’s and St Thomas’ Hospital, London, and colleagues conducted a study to identify the optimal pacing site for the left ventricular lead in ischemic patients with poor CRT response.

Researchers performed cardiac magnetic resonance imaging (MRI) and invasive electro-anatomical mapping, and measured the acute hemodynamic response in patients with existing CRT systems. They tested 135 epicardial and endocardial pacing sites in 8 patients.


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For each pacing site and endocardial position, they measured left ventricle electrogram amplitude and sensed electrical delay in the first left ventricle depolarization, stimulation-QRS (representing electrical depolarization of both ventricles) onset, and paced QRS duration.

“Endocardial pacing is superior to epicardial pacing with an even greater response achievable optimization for each set of protocols,” researchers concluded. “The mechanism of benefit may be due to the ability to access more optimal sites that cannot be reached by the constraints of the coronary sinus anatomy. Furthermore, guidance to the optimal LV [left ventricle] pacing site may be aided by modalities such as MRI to target non-scarred and delayed activating sites.”

The mean acute hemodynamic response of left ventricle endocardial positions was 11.81% (range: -7.2% to -44.6%), which was significantly superior to the mean acute hemodynamic response of left ventricular epicardial positions (6.55%; range: -11.0% to 19.7%; P=.025).

Endocardial pacing was also superior to epicardial pacing in terms of left ventricle depolarization (75ms vs 75ms; P=.354), shorter stimulation-QRS duration (15ms vs 19ms; P=.010), and shorter paced QRS duration (149ms vs 171ms; P<.001).

Researchers also found that the mean best achievable acute hemodynamic response was significantly was higher with endocardial pacing compared with epicardial pacing (25.64% ± 14.74% vs 12.64% ± 6.76%; P=.044). The acute hemodynamic response was significantly greater pacing the same site endocardially vs epicardially (15.2% ± 10.7% vs 7.6% ± 6.3%; P=.014) with a shorter paced QRS (137 ± 22ms vs 166 ± 30ms; P<.001) despite having a similar left ventricle depolarization.

Notable “lack of capture” in areas of scar, corroborated by electro-anatomical mapping and MRI, was associated with a poor acute hemodynamic response.

“Our results suggest that MRI imaging may be helpful in this respect especially in avoiding areas of scar, which result in failure to capture or poor resynchronization,” the authors noted. “Targeting a late but not necessarily latest activating site (ie, late but not within a scar) is achievable with MRI techniques that give information regarding myocardial activation/contraction patterns as well as pinpointing scar.”

Disclosures: Dr Claridge received research fellowship funding and Dr Sohal received an educational grant from St Jude Medical. Dr Jackson received research fellowship funding from Medtronic Inc. Dr Rinaldi is a consultant for St. Jude Medical, Medtronic, and Spectranetics, and receives research funding from St. Jude Medical and Medtronic.

Reference

Behar JM, Jackson T, Hyde E, et al. Optimised left ventricular endocardial stimulation is superior to optimized epicardial stimulation in ischemic patients with poor CRT response: a combined magnetic resonance imaging, electro-anatomical contact mapping and hemodynamic study to target endocardial lead placement. JACC Clin Electrophysiol. 2016. doi: 10.1016/j.jacep.2016.04.006.