Influence of Different Atrioventricular and Interventricular Delays on Cardiac Output During Cardiac Resynchronization Therapy

Abstract

Restoration of the atrioventricular (AVD) and interventricular (VVD) delays increases the hemodynamic benefit conferred by biventricular (BiV) stimulation. This study compared the effects of different AVD and VVD on cardiac output (CO) during three stimulation modes: BiV-LV = left ventricle (LV) preceding right ventricle (RV) by 4 ms; BiV-RV = RV preceding LV by 4 ms; LVP = single-site LV pacing. We studied 19 patients with chronic heart failure due to ischemic or idiopathic dilated cardiomyopathy, QRS >/= 150 ms, mean LV end-diastolic diameter = 78 +/- 7 mm, and mean LV ejection fraction = 21 +/- 3%. CO was estimated by Doppler echocardiographic velocity time integral formula with sample volume placed in the LV outflow tract. Sets of sensed-AVDs (S-AVD) 90-160 ms, paced-AVDs (P-AVD) 120-160 ms, and VVDs 4-20 ms were used. BiV-RV resulted in lower CO than BiV-LV. S-AVD 120 ms and P-AVD 140 ms caused the most significant increase in CO for all three pacing modes. LVP produced a similar increase in CO as BiV stimulation; however, AV sequential pacing was associated with a nonsignificantly higher CO during LVP than with BiV stimulation. CO during BiV stimulation was the highest when LV preceded RV, and VVD ranged between 4 and 12 ms. The most negative effect on CO was observed when RV preceded LV by 4 ms. Hemodynamic improvement during BiV stimulation was dependent both on optimized AVD and VVD. LV preceding RV by 4-12 ms was the most optimal. Advancement of the RV was not beneficial in the majority of patients.

Cardiac output response to changes of the atrioventricular delay in different body positions and during exercise in patients receiving cardiac resynchronization therapy

“…The relatively small CO response to AVD adjustments is in contrast with other studies reporting changes in the range of 10-16% using the aortic time-velocity integral 29,30 or thoracic bioimpedance. 31 Riedlbauchova et al 20 reported a non-significant 32% change in CO using similar AVD changes as in the present study. However, the fact that both rebreathing and the IHM captured significant haemodynamic effects caused by changes in body positions confirms that our methods were sensitive to relevant haemodynamic interventions.…”

“…7,19,20 However, the longterm clinical impact of AVD and/or VV-delay optimization still remains unclear. 21 -23 This may in part relate to the fact that large haemodynamic effects by AVD programming are mainly observed at extremely short or long AVDs which are usually not applied in clinical practice.…”

Cardiac resynchronization therapy in congenital heart disease

“…Asynchrony, characterized by intraventricular and interventricular conduction delay, may compromise diastolic filling, increase mitral regurgitation, worsen left ventricular dilation, and impair cardiac output [7][8][9][10][11]. CRT may improve quality of life, New York Heart Association (NYHA) functional class, exercise capacity, and left ventricular systolic function [1 -6].…”

Cardiac Resynchronization Therapy in Children

“…Cardiac asynchrony, characterized by intraventricular and interventricular conduction delay, may compromise diastolic filling, increase mitral and tricuspid valve regurgitation, worsen ventricular dilation, and impair cardiac output [1-5]. It has been long postulated that cardiac resynchronization therapy (CRT) increases the efficiency of muscular contraction and thus augments cardiac output.…”