![]() IMPACT ON MYOCARDIAL STRUCTURE AND FUNCTIONĬRT has been clearly linked to favorable changes in myocardial structural and functional parameters, termed reverse remodeling. In most situations, CRT is considered appropriate for patients with a LBBB and a QRS width ≥120 ms, while in patients with a non-LBBB morphology, the QRS width should ideally be ≥150 ms. 5 These subsets are largely dictated by the width of the QRS interval and morphology of the conduction defect. While CRT is currently approved by the United States Food and Drug Administration for patients with EF 120 ms and NYHA class III/IV symptoms or 2) QRS >130 ms, LBBB, and NYHA II symptoms, major society guidelines define additional appropriate patient subsets in whom the use of CRT is thought to be of benefit. It has additionally been associated with improvements in exercise capacity, oxygen consumption, NYHA symptom class, and quality of life. CRT has been associated with a significant reduction in heart failure symptoms, heart failure hospitalizations, and mortality 1 – 4 and has become a widely accepted device therapy for a variety of indications. CRT may be implanted with or without a defibrillator.ĬRT has represented a significant advance in the treatment of severe symptomatic systolic heart failure with electrical dyssynchrony as evidenced by a prolonged QRS on the surface electrocardiogram. Thus, CRT is more than simply biventricular pacing. ![]() The 3-lead system allows for restoration of the AV and VV synchrony that is commonly lost in severe systolic heart failure with advanced conduction disease. The LV lead is typically implanted transvenously via the coronary sinus but can also be implanted epicardially via lateral thoracotomy. Typical CRT systems include a right atrial lead, right ventricular lead, and left ventricular lead ( Figure 70-2). The LV lead is located in the coronary sinus, and the lead tip is position in the LV apex.ĬRT is an advanced pacing strategy able to restore electrical synchrony of both the atria and ventricles leading to improved chamber filling and pump function. Note the paced beats, marked with “ ” on the V 1 rhythm strip, are characterized by prominent R wave in V 1 and a narrower QRS compared to the native QRS.įIGURE 70-2 A posteroanterior and lateral radiograph demonstrating bilateral intersitial edema, cardiomegaly, and a standard 3-lead CRT device, with leads pacing the right atrium, right ventricle, and left ventricle. FIGURE 70-1 An ECG demonstrating atrial fibrillation with multiple QRS morphologies: biventricular paced and native IVCD with left axis deviation.
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