Reproducibility and inter-observer variability of dobutamine stress CMR in patients with severe coronary disease: implications for clinical research.

PURPOSE The purpose of this study was to analyze reproducibility and inter-observer variability of dobutamine stress cardiac magnetic resonance imaging (dobutamine CMR) and its implications on serial studies. METHODS Nineteen consecutive patients underwent two dobutamine CMR each (median 12 days apart), as part of eligibility criteria for phase I/II stem cell therapy trial. These patients had Canadian Cardiovascular Society Class III/IV angina despite maximal therapy. The two studies were compared for reproducibility of stress response. To assess inter-observer variability, 29 randomly selected dobutamine CMR studies were analyzed by three experienced observers and Kappa values were computed to measure the agreement. RESULTS Dobutamine CMR studies were completed without any major complications. The left ventricular function, dobutamine and atropine dose, hemodynamic response, symptomatic response and the results of wall motion and perfusion abnormalities were highly reproducible between the two studies (p = .91). Sample size calculations suggested that a clinical trial using dobutamine CMR to detect an endpoint of resolution of two ischemic segments would require a sample size of 20 subjects and to detect an improvement in perfusion of two segments would require a sample size of 8 subjects. Inter-observer variability between individual and consensus interpretation of dobutamine CMR was good to very good (kappa = 0.81 for wall motion and 0.70 for perfusion). CONCLUSION Dobutamine CMR is a highly reproducible technique with very good inter-observer variability and could be used as a specific endpoint in a relatively small clinical trial.