Continuously adjusting CRT therapy: clinical impact of adaptive cardiac resynchronization therapy

Abstract

Cardiac resynchronization therapy (CRT) is a well-established therapy to reduce morbidity and mortality in patients with moderate and severe symptomatic congestive heart failure. Left ventricular (LV) pacing that fuses with intrinsic right ventricular (RV) conduction results in similar or even better cardiac performance compared to biventricular (Biv) pacing. Optimal programming of the atrio-ventricular (AV) and inter-ventricular (VV) delays is crucial to improve LV performance since suboptimal programming of AV and VV delays affect LV filling as well as cardiac output. CRT optimization using echocardiogram is resource-dependent and time consuming. Adaptive CRT (aCRT) algorithm provides a dynamic, automatic, ambulatory adjustment of CRT pacing configuration (Biv or LV pacing) and optimization of AV and VV delays. aCRT algorithm is safe and efficacious for CRT-indicated patients without permanent atrial fibrillation. It has been shown to improve CRT response and reduce morbidity and mortality for patients with normal AV conduction.

Keywords::

• adaptive
• biventricular pacing
• cardiac resynchronization
• left ventricular pacing
• optimization

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Right ventricular (RV) pacing (alone or during biventricular pacing) in patients with left ventricular (LV) dysfunction results in worsening of RV and LV performance.

• The best LV hemodynamic improvement is achieved when fusion of the intrinsic RV conduction with LV pacing occurs. This is known as synchronized LV pacing.

• At heart rates exceeding 100 bpm, further increase in LV performance was observed during biventricular pacing stimulation compared with LV pacing.

• ECG-optimized atrio-ventricular (AV) and inter-ventricular (VV) delays resulted in similar improvement of LV size and function compared with the echocardiogram-optimized AV and VV delays.

• Adaptive cardiac resynchronization therapy (aCRT) algorithm provides a dynamic ambulatory adjustment of the CRT pacing as well as optimization of the AV and VV delays based on periodical measurement of electrical conduction intervals in patients with sinus rhythm and AV conduction.

• The higher the LV pacing (≥50%), the better the clinical outcome and survival, since LV pacing improves the LV hemodynamic and prevents RV pacing.

• Predictors of higher percentage of LV pacing (≥50%) are observed in normal AV conduction, higher prevalence of left bundle-branch block, non-ischemic cardiomyopathy, slightly younger and fewer male.

• There is a significant reduction of development of atrial fibrillation in aCRT compared with conventional CRT.

• Patients with congestive heart failure, sinus rhythm and normal AV conduction (As-RVs ≤200 ms, Ap-RVs ≤250 ms) should be receiving aCRT due to greater clinical response and lower rate of death or heart failure hospitalizations observed in this patient population with the algorithm.

Notes