Left-ventricular-only cardiac resynchronization therapy with electrocardiographic optimization of the atrio-ventricular delay and with active dromotropic modulation
T Thong, T O A N Nguyen-Duy, D U C Nguyen-Huu, K N Truong, T D Tran, C U O N G Vuong-Dinh, T A N Vu-Manh, N A M Hoang-Phuong, N H U T Nguyen-Lien, C A M T U Nguyen, T H A N G Nguyen-Duy, T U Le, P H O N G Nguyen-Vu, T I E N Hoang-Anh, M I N H HuynhAbstract
Introduction
Traditional pacing therapy of congestive heart failure uses a triple chamber CRT pacing device with biventricular (biV) pacing. Left Bundle Branch pacing (LBBp) has also been proposed as an improved alternative to biV.
Purpose
A new LV-only (LVo) CRT method with ECG optimization of the LV AV delay with active dromotropic modulation is proposed. The intrinsic RV depolarization is used, yielding optimal RV contraction.
Methods
The ECG optimization consists of synchronizing the A-RV intrinsic (per sensing test) and LVp (per LV threshold test) wavefronts at the times of the strongest contractions in the respective ventricles, corresponding to the largest (positive or negative) initial deflection in the ECG lead DII (with contributions from RV and LV). In these tests, until the initial DII peak/trough, in the ventricles there is only one wavefront in the RV or LV. Thus, this DII synchronization leads to the largest myocardium mass being simultaneously depolarized in the RV and LV. This optimum LV AV delay is the AVDopt.
To recruit dromotropic modulation for this LVo CRT, instead of using AVDopt, the LVp is advanced slightly, about 15 ms. Thus, LV AVD=AVDopt-15 ms.
At rest, there is a small ventricular dyssynchrony between the RV and LV. Due to homeostasis, this small imbalance is compensated by slight increases in chronotropic and inotropic modulations.
During the initial stages of exercise, the Autonomic Nervous System (ANS) shortens the A-RV to reduce the asynchrony. This "free" dromotropic effect will result in a small bolus of blood that can kick-start increased chronotropic and inotropic modulations, power-hungry functions. At high level of exercise, chronotropy becomes the primary driver of hemodynamics. This kick-start effect should reduce exercise differences in patients with NYHA I, II and III.
Since the RV lead is redundant in LVo, a dual chamber CRT (dcCRT) can be used with bipolar RA & LV leads with an off-the-shelf dual chamber PM.
24 dcCRT patients were followed: age 64.2±12.1, 61% male, LVEF 28.1±7.3%.
Results
The LVEFs are reported in Fig.1. Follow-ups were to 20.5±8.0 months. For comparison, also shown are LVEFs from a 2024 study of 68 LBBp and 153 biV patients[1]. The improvements in LVEF are clearly superior with dcCRT. Note that the dcCRT LVEF curve has an initial steep slope, followed by a leveling, then a smaller positive slope past 1 year. The LBBp and biV curves >6 month are on constant smaller slope.
Echocardiographic summaries are shown in Fig.2. DcCRT super-response is clearly superior.
Conclusions
With the ECG optimization and the recruitment of dromotropic modulation during exercise, the new LVo CRT is clearly superior to biV and LBBp. The LVo program can be applied to triple chamber CRT devices, even those already implanted. Since it is possible to go back to biV at any time, the conversion to LVo is safe. This is a paradigm shift in CRT, yielding a superior therapy for heart failure patients!LVEFEchocardiographic summaries