Mechanical dispersion (MD) is a better predictive tool for patients at risk for a ventricular arrhythmia (VA) event and sudden cardiac death (SCD) than left ventricular ejection fraction (LVEF) alone, according to a study published in JACC Cardiovascular Imaging.
In this retrospective, observational, multicenter study, researchers identified 939 consecutive, clinically stable patients presenting between 2008 and 2014 with an outpatient echocardiogram that demonstrated a reported Simpson’s LVEF ≤45%. Patients were included in the analysis if they were ≥40 days post-acute hospital admissions for myocardial infarction (MI) or heart failure (HF) and were on optimal medical therapy.
Speckle-tracking strain analysis was performed on the LV-focused views from apical 4- chamber, 2-chamber, and long axis views. Global longitudinal strain (GLS) was calculated as the average of all peak regional strain values in the 16 segments of the LV. An age-matched cohort without any documented cardiovascular history and low cardiovascular risk factors (n=200) underwent the same strain analysis to establish a normal range for MD and GLS.
The average GLS was -20.4±3.2% and the MD was 53.5±11.0 ms in the normal cohort. Cut-off values for abnormal ranges were calculated by adding 2 standard deviations to the mean; the cut-off value was calculated as ≥-14% for GLS and ≥75 msec for MD. There were 9 VA events in patients with MD <75 msec and 87 VA events in patients with MD≥75 msec, compared with 43 VA events in patients with LVEF>35% and 53 VA events in patients with LVEF ≤35%.
Cox univariate analysis showed that MD ≥75 msec (hazard ratio [HR], 9.86; 95% CI, 4.96-19.58; P <.0001), LVEF ≤35% (HR, 1.70; 95% CI, 1.15-2.57; P =.008), prior atrial fibrillation (HR, 1.48; 95% CI, 0.95-2.30; P =.09), hypertension (HR, 1.88; 95% CI, 1.26-2.8; P =.002), and prior HF (HR, 1.71; 95% CI, 1.15-2.56; P =.008) were predictors of VA events. Cox multivariate analysis demonstrated that only MD ≥75 msec was predictive of VA events (HR, 9.45; 95% CI, 4.75-18.81, P <.0001).
This study was limited by its retrospective design and inherent limitations, such as unknown symptomatic status at time of echocardiography. Incorrect coding in databases has a potential impact on the study results. Patients with greater than mild valvular disease were excluded to increase the likelihood that changes seen in the MD were indicative of scarring. Future studies should focus on this population.
“This study has demonstrated that MD ≥75 msec, as measured by echocardiographic myocardial deformation imaging, is predictive of VA events in patients with moderate and severe LV systolic dysfunction,” the researchers concluded. “Importantly MD was an independent predictor of SCD and malignant VA, even in patients with LVEF is >35%. MD is a complement to LVEF and easily obtained using standard echocardiographic images and may better define patients who would benefit from implantable cardiac defibrillator (ICD) therapy.”
Perry R, Patil S, Marx C, et al. Advanced echocardiographic imaging for prediction of sudden cardiac death in moderate and severe left ventricular systolic function [published online October 11, 2019]. JACC Cardiovasc Imaging. doi:10.1016/j.jcmg.2019.07.026