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  • br Conclusion br Limitations br

    2019-06-19


    Conclusion
    Limitations
    Conflict of interest
    Introduction The prevalence of Cyclopiazonic acid failure prevalence is increasing throughout the world. The reasons for this pandemic include the aging populations of both industrialized and developing nations and a growing incidence of obesity, diabetes, and hypertension [1]. Several conduction abnormalities are commonly seen in association with chronic heart failure. Among these are abnormalities of ventricular conduction, such as bundle branch blocks that alter the timing and pattern of ventricular contraction, so as to place the already failing heart at a further mechanical disadvantage [2]. These ventricular conduction delays produce suboptimal ventricular filling, a reduction in left ventricular (LV) contractility, prolonged duration of mitral regurgitation, and paradoxical septal wall motion. Taken together, these mechanical manifestations of altered ventricular conduction have been termed ventricular dyssynchrony [2,3]. Ventricular dyssynchrony has been defined by a prolonged QRS duration, generally longer than 120ms, on a surface electrocardiogram [3]. By this definition, about one third of patients with systolic heart failure have ventricular dyssynchrony [4]. In patients with heart failure, cardiac resynchronization therapy (CRT) for 6 months was associated with reduced end-diastolic and end-systolic volume, reduced LV mass, increased ejection fraction, reduced mitral regurgitant blood flow, and improved myocardial performance index as compared with controls [5–8]. Biventricular pacing (BiV) is the most common mode of delivering CRT [9]. However, initial clinical studies comparing BiV pacing with LV only pacing indicated that BiV and LV pacing may provide a similar systolic function [10–15]. Nonetheless, more evidence is required based on clinical trials conducted in different settings, to confirm this issue. The present study addressed this important question by comparing the hemodynamic responses of BiV versus LV only pacing in patients with a standard indication for ventricular pacing.
    Materials and methods The patients with CRT, who were referred to the electrophysiological clinic of Ekbatan (Farshchian) Hospital, were enrolled if they fulfilled the following criteria: (a) LV ejection fraction less than or equal to 35%; (b) a QRS duration greater than or equal to 0.12s; (c) sinus rhythm; (d) indication for the treatment of New York Heart Association (NYHA) functional Class III or ambulatory Class IV heart failure symptoms with optimal recommended medical therapy; and (e) had received CRT at least 3 months previously. Patient characteristics were as follows: etiology (non-ischemic, 24 patients; ischemic, 20 patients); morphology (LBBB, 38 patients; non-LBBB, 7 patients); QRS interval (LBBB group, 158±32ms; non-LBBB group, 185±38ms). All patients were on full medical treatments including loop diuretic (furosemide), beta blocker (long acting metoprolol or carvedilol) and angiotensin converting enzyme inhibitors or angiotensin receptor blockers. Spironolactone was administered to all patients with a creatinine level less than 2.2mg/dL and potassium level less than 5.5mEq/dL. The dosage of all drugs was adjusted according to the patients’ conditions. The CRT devices of all patients had already been set for BiV pacing. Therefore, their CRT devices were set for LV only pacing for 3 months. The hemodynamic status of the patients was assessed by echocardiography before setting (as control) and three months later (as an intervention). After setting, the mean QRS width was 148±34ms. A decrease of 0–80ms in QRS width was observed. An atrioventricular (AV) delay was described as nominal in all patients, and echo-guided optimization was used in non-responsive patients. At the end of the study, patients’ pacemakers were set back to the initial BiV pacing. In order to minimize possible errors, all patients were evaluated with a specific echocardiography machine (MY LAB 60, Esaote, Italy). The paired t-test was used for analysis of continuous variables. All statistical analyses were performed at a significance level of 0.05 using statistical software Stata 11 (Stata Corp, College Station, TX, USA).