Abstract
Up to 30-40% of patients undergoing cardiac resynchronization therapy (CRT) are described as nonresponders since the initial studies. This paradigm has inspired several modifications of the devices, electrodes and surgical technique in the implant. The definition of CRT response should be rethought, standardized, and ratings based on structural and/or clinical response should be proposed. The authors discuss a series of cases in which sustained clinical improvement was achieved despite structural worsening. Objective: To assess the profi le of clinical responders to CRT who have worsened structurally. Method: It is a retrospective cohort of patients in outpatient follow-up from January 2012 to March 2017. We included 13 patients (2.7%) out of a total of 476 submitted to CRT. Inclusion criteria were to present an improvement in functional class according to the New York Heart Association criteria (FC-NYHA) ≥ 1 sustained for at least one year and absence of improvement or worsening of the structural parameters evaluated by transthoracic echocardiogram [ejection fraction (EF), diastolic diameter (LVDD) and systolic diameter (LVSD)]. The variables analyzed were age, gender, FC-NYHA, cardiopathy, echocardiographic and electrocardiographic parameters, medications in use, location of implanted electrodes, device programming, cardiary defibrillator therapies, and mortality. Statistical analysis was performed using non-parametric Wilcoxon and McNemar tests. Results: There were 13 patients, 92% male, mean age 60.9 ± 9.2 years and mean follow-up of 3.3 ± 1.1 years, 76% of CRT associated with implantable cardioverter defibrillator (CRT-D). In pre-implantation, 84.6% were in FC-NYHA III and then 61.5% were in FC-NYHA I (p = 0.001). The mean pre-implantation EF was 31.3 ± 7.6% and 26.6 ± 7.3 (p = 0.002) in the last evaluation. The predominant heart disease was non-ischemic in 92.5%, most of which were chagasic cardiomyopathy (CCM) (66%). In the TRC-D group, no shock therapy was recorded in the period; there was one death in a patient with ischemic cardiomyopathy (IC) for the septic shock of pulmonary focus after 2.2 years of follow-up. The mean QRS was 189.9 ± 23.1 ms to 157.9 ± 35.2 after CRT (p = 0.032). There was no signifi cant change in pre-and postimplant medications during follow-up. Conclusion: The absence of structural improvement should not be considered therapeutic failure, since CRT seeks to modify the electrical activation, and may be related to better performance and decrease of symptoms, even in evolutionary heart diseases.
Highlights
Cardiac pacing began to be thought of as adjuvant therapy in the treatment of cardiac insufficiency (CI) refractory to pharmacological treatment in the mid-1990s.The theoretical and experimental basis of this application is the correction of delayed left ventricular (LV) contraction in patients with ischemic cardiomyopathy (IC) that present complete left bundle branch block (LBBB)
Despite the technical advances of devices, electrodes, implant surgery, and development of complementary methods, more recent studies still classify about 30% of patients as non-responders to cardiac resynchronization therapy (CRT) despite the lack of consensus in the definition of CRT response[1,2,3,4,5,6,7,8].The present study analyzed a retrospective cohort of patients submitted to CRT, evaluating the profile of clinical responders to therapy, seeking to identify factors associated with the mechanism of action that results in clinical improvement without the presence of structural improvement
Exclusion criteria were any increase in left ventricular ejection fraction (EF) and/or reduction of diastolic and/ or final systolic diameters evaluated by transthoracic echocardiography or unsupported clinical improvement for a minimum period of 12 months
Summary
Cardiac pacing began to be thought of as adjuvant therapy in the treatment of cardiac insufficiency (CI) refractory to pharmacological treatment in the mid-1990s.The theoretical and experimental basis of this application is the correction of delayed left ventricular (LV) contraction in patients with IC that present complete left bundle branch block (LBBB). In these cases, with the advent of imaging exams such as echocardiography, it can be confirmed that, in addition to the delay in electrical activation, there is mechanical dyssynchrony of the ventricle, decreasing cardiac efficiency, and may promote cardiac remodeling in the short and long term. Despite the technical advances of devices, electrodes, implant surgery, and development of complementary methods, more recent studies still classify about 30% of patients as non-responders to CRT despite the lack of consensus in the definition of CRT response[1,2,3,4,5,6,7,8].The present study analyzed a retrospective cohort of patients submitted to CRT, evaluating the profile of clinical responders to therapy, seeking to identify factors associated with the mechanism of action that results in clinical improvement without the presence of structural improvement
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