Prediction of beneficial effect of β blocker treatment in severe ischaemic cardiomyopathy: assessment of global left ventricular ejection fraction using dobutamine stress cardiovascular magnetic resonance

Patients with severe ischaemic cardiomyopathy have a combination of viable and non-viable myocardium. In the presence of substantial ischaemic, but viable myocardium, β blocker treatment may improve left ventricular ejection fraction (LVEF) because of a reduction in oxygen consumption and a restoration of β adrenergic signalling pathways. However, not all patients show a positive response to this treatment1 and some can suffer from side effects.2 Therefore, it is desirable to identify patients with a high likelihood of beneficial response to β blockers. Models currently used to detect viable myocardium are based upon segmental analysis. Dobutamine induced segmental improvement before treatment is suggested to have a relation between regional contractile reserve and improvement in global LVEF after β blocker treatment. However, improvement of remote tissue is not evaluated and this may also contribute to the improvement of LVEF after treatment. Thus, direct measurement of LVEF during low dose dobutamine stimulation may represent contractile reserve of the entire left ventricle. Cardiovascular magnetic resonance imaging (MRI) is a highly reproducible, validated, and observer independent imaging method for the measurement of global LVEF, and can be used to evaluate LVEF at rest as well as during dobutamine stress. Furthermore, Bellenger and co-workers described that calculated sample sizes for assessment of LVEF for MRI were substantially smaller than recently published values for ultrasound. The measurement of a 3% change in LVEF required only 15 patients.3 Accordingly, the purpose of the present study was to evaluate the feasibility for prediction of β blocker treatment effect …