Cardiac resynchronization therapy restores optimal atrioventricular mechanical timing in heart failure patients with ventricular conduction delay

Abstract

We characterized the relationship between systolic ventricular function and left ventricular (LV) end-diastolic pressure (LVEDP) in patients with heart failure (HF) and baseline asynchrony during ventricular stimulation. The role of preload in the systolic performance improvement that can be obtained in HF patients with LV stimulation is uncertain.We measured the maximum rate of increase of LV pressure, LVEDP, aortic pulse pressure (PP) and the atrioventricular mechanical latency (AVL) between left atrial systole and LV pressure onset in 39 patients with HF. Two subgroups were identified: "responder" if PP improved, or "nonresponder."Maximum hemodynamic improvement occurred at an atrioventricular (AV) delay that did not decrease LVEDP. Left ventricular and biventricular (BV) stimulation increased systolic hemodynamics significantly, despite no significant increase in LVEDP. All parameters decreased when the LVEDP was decreased by shorter AV delay. Left ventricular and BV stimulation provided better hemodynamics than right ventricular (RV) stimulation. For the nonresponder subgroup, systolic hemodynamics only worsened during AV delay shortening. For the responder subgroup, optimum PP was achieved when AVL was near zero. Restoration of optimal left atrial-ventricular mechanical timing partly contributes to the hemodynamic improvements observed in this patient subgroup. However, preload alone cannot explain the differences seen between RV and BV stimulation and the contradictory PP decreases even at maximal preload in the nonresponder subgroup. These results may be explained by a site-dependent mechanism such as the degree of ventricular synchrony. Caution should be taken in these patients when optimizing AV delays using echocardiography techniques that focus on LV inflow.

Improvement in Coronary Blood Flow Velocity With Acute Biventricular Pacing Is Predominantly Due to an Increase in a Diastolic Backward-Travelling Decompression (Suction) Wave

“…[1][2][3][4][5][6] These pioneering small studies paved the way for large randomized controlled trials that demonstrated reductions in morbidity and mortality in heart failure. [7][8][9][10][11][12][13] Surprisingly, the effects of biventricular pacing on coronary blood flow have been little studied.…”

Cardiac Resynchronisation Therapy: The Role of Echocardiography in Patient Selection and Follow-up

“…Although AV-delay optimisation can clearly impact hemodynamics in patients undergoing CRT, (32,33) it has less infl uence on LV function than the optimal pacing site (34) . An optimal AV delay is that which allows completion of the end-diastolic fi lling fl ow prior to ventricular contraction, thereby providing the longest diastolic fi lling time.…”

“…It has been recommended that the VV-interval be optimised before the AVinterval, to prevent inappropriate AV-delay programming, which might reduce LV fi lling (33) .…”

Whether noninvasive optimization of AV and VV delays improves the response to cardiac resynchronization therapy

“…CRT reduces clinical symptoms of heart failure, decreasing incidence of hospitalization, and also signifi cantly decreasing mortality in these patients [3,4]. The success of CRT depends on many factors such as appropriate location of the left ventricular (LV) electrode, and optimal timing of atrioventricular (AV) and VV delays [5,6]. Optimal programming of AV and VV delays plays an important role in reducing the proportion of patients who derive no apparent benefi t from CRT (the so called "non-responders"), despite correct positioning of the LV electrode [7].…”