Effects of Atrio-Ventricular Delay and Interventricular Delay on Continuous Left Atrial Pressure and Waveforms in Ambulant Heart Failure Patients: A Novel Method for Cardiac Resynchronisation Therapy Optimisation

Abstract

Background: Left atrial pressure (LAP) is sensitive to cardiac resynchronisation therapy (CRT) device settings and may be helpful for CRT optimisation. We evaluated the effect of changes in atrio-ventricular delay (AVD) and inter-ventricular delay (VVD) on LAP and its waveform morphology using a novel implantable LAP sensor. Methods: Eight ambulant patients (age 66 ± 12 yrs, EF 30 ± 10%) implanted with separate CRT-D and a new LAP monitoring system (PROMOTE™ RF and HeartPOD™ ISL, both from St Jude Medical) underwent CRT optimization with echocardiographic guidance including transmitral and left ventricular outflow tract Doppler indices. Left atrial pressure and intracardiac electrograms were recorded at eight AVDs and five VVDs. Each LAP recording was 20 seconds long and was band-pass filtered to remove both high-frequency noise and respiration artifact. QRS-triggered ensemble average waveforms were calculated for each recording and plotted to evaluate the effects of the different AVDs and VVDs on the LAP waveform. Results: Mean LAPs were lower in the more optimal echocardiography guided settings. All patients exhibited a dramatic response in waveform morphology to the changes in AVD with the c-wave moving progressively into the a-wave and producing large cannon a-waves with shorter, less optimal AVD. Inter-ventricular delay changes produced a less dramatic effect on LAP morphology. The effects were consistent between patients, with individual patient signals correlating closely with the mean population signal r = 0.80 ± 0.14. Conclusion: Left atrial pressure and its waveform morphology are sensitive to the effects of AVD and VVD in a consistent manner across patients. Further investigation of the role of LAP in CRT interval optimisation is warranted.