ABSTRACT

It has been reported that 10-30% of patients undergoing CRT either do not experience an improvement or in fact may worsen following implantation of a biventricular (BiV) pacing system and therefore have been termed ‘nonresponders’.1-3 Managing and troubleshooting these patients can be challenging, yet a rational systematic approach utilizing echocardiographic imaging to diagnose problems and optimize pacing settings can be useful in maximizing the potential of the therapy. Moreover, echocardiographic data may play a key role in determining when pacing therapy is poorly deployed or even detrimental.4 Significant controversy persists, however, regarding the definition of non-response, as some experts would argue that evidence of reverse remodeling (defined as a decrease in end-systolic volume of >15%) is necessary in order to categorize a patient as a responder,1,3,5,6 whereas others maintain that parameters such as functional class (New York Heart Association (NYHA) classification), global quality-of life-scores, and hospitalizations should be included in defining success or failure of the therapy. This controversy is dealt with elsewhere in this book. This chapter will focus on the clinical and echocardiographic evaluation of the patient once a no-response status has been determined, regardless of whether that means failure to demonstrate an improved left ventricular (LV) ejection fraction (LVEF) or lack of an

improved functional status. Yet another important consideration should be the time interval following implantation that should be allowed before re-evaluating function. Although some patients may experience an immediate response (either positive or negative), most studies would suggest that of the two-thirds of patients who experience a benefit, most will experience evidence of reverse remodeling 3-6 months following the procedure.7 Unless clear clinical or ventricular function deterioration is apparent, allowing a minimum of 1 and at least 3 months for evidence of response would seem most representative of the true impact of the therapy.