This article appears in the following Europace issue: Spotlight Issue: Cardiac Imaging in EP and CRT [View the issue table of contents]
IMAGING IN CRT
Echocardiographic optimization of the atrioventricular and interventricular intervals during cardiac resynchronization
Cardiology Division, University of South Florida College of Medicine and Tampa General Hospital, Tampa, FL, USA
An optimized atrioventricular (AV) interval can maximize the benefits of cardiac resynchronization therapy (CRT). If programmed poorly, it may curtail beneficial effects of CRT. AV optimization will not convert non-responder to responder, but may convert under-responder to improved status. There are many echocardiographic techniques for AV optimization but there is no universally accepted gold standard. The optimal AV delay varies with time, necessitating periodic re-evaluation. As the optimal AV delay may lengthen on exercise, a rate-adaptive AV delay should not be routinely programmed. Intra- and interatrial conduction delays may require AV junctional ablation when AV optimization is impossible in patients with a poor clinical response. Fusion with the spontaneous QRS complex may be acceptable on a trial basis to seek a better clinical response or with a short PR interval. Routine VV optimization is presently controversial but programming may prove beneficial in some patients with a suboptimal CRT response where no cause is found. It may partially compensate for less than optimal left ventricular (LV) lead position and may correct for heterogeneous ventricular activation including a prolonged LV latency interval and slow conduction (scarring) near the LV pacing site. VV timing is generally programmed using the aortic velocity–time integral, and long-term variations of the optimal value necessitate periodic re-evaluation.
Key Words: Cardiac resynchronization, Biventricular pacing, Echocardiography, Atrioventricular interval, Interventricular interval
* Corresponding author. 5806 Mariner's Watch Drive, Tampa, FL 33615, USA. Fax: +1 813 891 1908. E-mail address: ssbarold{at}aol.com