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Myocardial mechanical dispersion increased in post-MI patients at risk for arrhythmias

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Left ventricular mechanical dispersion was more pronounced in post-MI patients with recurrent arrhythmias vs. those without arrhythmias, new study results indicated.

Researchers included 85 post-MI patients with and without arrhythmias who fulfilled study indications for implantable cardioverter defibrillator therapy. All patients underwent coronary angiography prior to ICD implantation, and 49 patients received percutaneous coronary intervention. Forty-seven patients had no arrhythmias, and 38 patients had >1 arrhythmia requiring appropriate ICD therapy during follow-up. The researchers measured regional heterogeneity of contraction by myocardial strain to determine left ventricular mechanical dispersion. They assessed longitudinal strain using speckle tracking echocardiography, and the calculated standard deviation of time to maximum myocardial shortening in a 16-segment LV model as a measure of LV mechanical dispersion. Patients were followed for a mean of 2.3 years.

There was no difference in ejection fraction between ICD patients with and without arrhythmias during follow-up (34 ± 11% vs. 35 ± 9%, P=.70), results indicated. The researchers reported that LV mechanical dispersion was greater in patients with recorded ventricular arrhythmias vs. those without recorded arrhythmias (85 ± 29 milliseconds vs. 56 ± 13 milliseconds, P<.001). By Cox regression, LV mechanical dispersion was an independent predictor of arrhythmias requiring ICD therapy (HR=1.25 per 10-millisecond increase; 95% CI, 1.1-1.4). Global strain showed better LV function in patients without recorded arrhythmias and with an ejection fraction >35% (P=.05), whereas ejection fraction did not differ between the groups (P=.023).

“This study demonstrates that post-MI patients at risk for cardiac arrhythmias have increased myocardial mechanical dispersion,” the researchers wrote. “Assessment of mechanical dispersion by echocardiography might therefore help identify post-MI patients susceptible to ventricular arrhythmias beyond the extent of reduced LV function.”

Haugaa K. J Am Coll Cardiol Img. 2010;3:247-256.

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