Left Ventricular Mechanical Dyssynchrony in Acute Onset Cardiomyopathy: Association of Its Resolution With Improvements in Ventricular Function
What is the impact of mechanical dyssynchrony in patients with acute onset cardiomyopathy with narrow QRS interval, and what is its association with improvements in left ventricular (LV) function?
The study cohort was comprised of 201 patients enrolled in the IMAC-2 (Inflammatory Mediators in Acute Cardiomyopathy) trial with recent onset nonischemic cardiomyopathy and ejection fraction <40%. The study investigators assessed: 1) ventricular dyssynchrony using speckle-tracking velocity vector imaging, and 2) diastolic function by mitral inflow E and mitral E’ annular velocities (E/E’). The control group was comprised of 15 normal volunteers.
The study investigators found that 54% of patients (n = 108) had significant LV dyssynchrony at presentation: opposing wall delay 89 ± 51 ms versus 35 ± 11 ms in controls, and 12-site standard deviation 43 ± 23 versus 24 ± 8 ms in controls (p < 0.001) despite a narrow QRS complex (mean 98 ± 21 ms). The diastolic dysfunction was greater (E/E’ 15 ± 8 versus 12 ± 6, p < 0.05) in patients with ventricular dyssynchrony. The investigators also found that mean ejection fraction improved from 23 ± 8% to 40 ± 12%, and E/E’ improved from 14 ±7 to 9 ± 5 (both p < 0.001) at the end of 6 months. Dyssynchrony improved from 89 ± 51 ms to 52 ± 35 ms in maximum opposing wall delay, and 43 ± 23 ms to 32 ± 19 ms in 12-site standard deviation, and the prevalence of dyssynchrony decreased to 12% after 6 months (p < 0.001 vs. baseline).
The investigators concluded that mechanical dyssynchrony was not uncommon in acute onset cardiomyopathy, despite having a narrow QRS interval. They also concluded that resolution of LV dyssynchrony is associated with improvements in LV systolic function.
Given that the natural history of acute onset cardiomyopathy is variable, the findings of this study are important. The next step would be to determine whether LV dyssynchrony is a predictor of recovery of LV systolic function. If so, the next move would be to determine optimal therapy that will promote recovery of LV systolic function.
Keywords: Ventricular Function, Left, Cardiomyopathies, Heart Failure, Diastole, Heart Ventricles, Systole
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