Cardiac resynchronization therapy: the state of the art

Abstract

A strong body of evidence exists to support cardiac resynchronization therapy (CRT) as a mainstay in the management of advanced heart failure for patients with LBBB-type QRS prolongation. Progress in technology has made percutaneous CRT easier to achieve. Skillful operators can readily reach implantation success rates in excess of 95%. Nevertheless, not every patient selected for CRT, according to current criteria, benefits from this therapy. Several factors contribute to the lack of benefit in these patients, including inadequate patient selection, lack of control of atrial arrhythmias, procedural factors and suboptimal pacemaker settings. It remains to be seen whether newer technology and pacing algorithms will increase response rates to CRT. The focus of this review will be to examine which patients benefit most from CRT and to assess methods for optimizing patient selection in order to achieve maximum benefit from this pivotal therapy.

Keywords::

• AV optimization
• heart failure
• remodeling
• resynchronization
• VV optimization

Financial & competing interests disclosure

RG Trohman has served as an advisor to Boston Scientific/Guidant; received research grants from Boston Scientific/Guidant, Medtronic Inc., St Jude Medical, Vitatron and Wyeth-Ayerst/Wyeth Pharmaceuticals; served as a consultant for Biosense Webster and St Jude Medical and has received speaker’s fees or honoraria from Boston Scientific/Guidant CRM, Medtronic Inc. and St Jude Medical. The authors have no other 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 apart from those disclosed.

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

Key issues

• Cardiac resynchronization therapy has become a mainstay in the management of select patients with systolic heart failure (left ventricular [LV] ejection fraction ≤35%).

• QRS duration ≥140–150 ms and left bundle branch block QRS morphology appear to be the most important criteria for patient selection.

• Response to cardiac resynchronization therapy varies from ‘super’ (with near or complete normalization of ejection fraction) to nonresponder.

• LV-only pacing may be as beneficial as biventricular pacing.

• LV-only pacing is thought to improve LV systolic function by increasing the amount of mechanical work generated by the right ventricular myocardium.

• Basic and clinical research directed toward understanding and reducing nonresponse is ongoing.

• The benefits derived from current methods of AV and VV optimization are limited.

• Recent data have rekindled in interest in LV endocardial pacing.

• Completion of controlled trials confirming the safety, efficacy and superiority of LV endocardial pacing compared with standard cardiac resynchronization therapy is requisite to implementation of this approach.

Notes