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Echo Mechanical Dispersion for SCD Risk
Study Questions:
Is there long-term prognostic value associated with echocardiographic strain-derived myocardial dispersion (MD) in risk stratification for malignant arrhythmias among patients with left ventricular (LV) systolic dysfunction?
Methods:
In a retrospective study, consecutive, clinically stable patients who underwent echocardiographic imaging in an outpatient setting from 2008 to 2014 with a Simpson LV ejection fraction (LVEF) ≤45% regardless of etiology and with no more than mild disease of any heart valve were included. LV strain analysis was performed using a 16-segment model. MD was calculated as the standard deviation of the time to peak strain for each of the 16 segments. An age-matched cohort of 200 patients without documented cardiovascular history and with low cardiovascular risk served as a control group. Ventricular arrhythmia (VA) outcome data (defined as first incidence of sudden cardiac death [SCD], hospitalization primary for symptomatic ventricular tachycardia [VT] or ventricular fibrillation [VF], or appropriate implantable cardioverter-defibrillator [ICD] therapy) were obtained from medical records.
Results:
A total of 939 patients were included in the study, with median LVEF 37% (interquartile range, 30-42%). At follow-up (91.4 ± 23.4 months), 96 VA events had occurred, including 41 arrhythmic deaths, 32 cases of symptomatic VT/VF, and 23 cases of appropriate ICD therapy; of these, 43 (45%) occurred in patients with LVEF >35%. Multivariate analysis demonstrated that only MD ≥75 ms (hazard ratio, 9.45; 95% confidence interval, 4.75-18.81; p < 0.0001) was predictive of VA events (without predictive power associated with LVEF or global longitudinal strain). Low MD predicted a low event rate, irrespective of LVEF.
Conclusions:
In this study, MD but not LVEF or global longitudinal strain was predictive of VA and SCD. The authors propose that MD can be used to improve risk stratification for VA, particularly among patients who are currently not candidates for cardiac defibrillator implantation based on LVEF.
Perspective:
Higher MD might be a harbinger of LV myocardial scar and fibrosis, substrates for malignant arrhythmias. Previous studies with relatively small patient cohorts have suggested that MD is a predictor of VA events among patients who underwent ICD implantation for primary or secondary prevention; and, independent of LVEF, among patients who have a nonischemic cardiomyopathy or who suffered a myocardial infarction. This study found that MD ≥75 ms predicted VA events among patients with LV dysfunction, including among patients with LVEF >35%. However, over three quarters of patients were excluded due to anything more than mild valve disease. If the findings can be reproduced in a large, prospective, multicenter study with a less selective patient population, then echo strain-derived MD might be useful to help inform decisions regarding defibrillator implantation for primary prevention.
Clinical Topics: Arrhythmias and Clinical EP, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Valvular Heart Disease, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound
Keywords: Arrhythmias, Cardiac, Cardiomyopathies, Death, Sudden, Cardiac, Defibrillators, Implantable, Diagnostic Imaging, Echocardiography, Heart Failure, Heart Valve Diseases, Myocardial Infarction, Primary Prevention, Risk Factors, Secondary Prevention, Stroke Volume, Tachycardia, Ventricular, Ventricular Dysfunction, Left, Ventricular Fibrillation
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