P461Prognostic value of inotropic contractile reserve during low-dose dobutamine stress echo in identifying CRT responders.

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Purpose: Inotropic contractile reserve (ICR) during dobutamine stress echo (DSE) differentiates the viable myocardium from scar tissue according to inotropic response. Furthermore, low dose DSE provides information for the global left ventricular response. The aim of this study was to identify the role of inotropic contractile reserve while compared with other echocardiographic indices in predicting cardiac resynchronization therapy (CRT) responders.Methods: 34 pts referred for clinically indicated CRT were evaluated. The interventricular and intraventricular dysynchrony were evaluated using conventional and TDI Doppler indices. All patients underwent low-dose dobutamine stress echocardiography to assess ICR, defined as an improvement of ejection fraction (EF) >5%. Responders were defined by a 5-percent increase in EF after CRT.Results: 34 pts (mean age 65±9 years old, 25 men, NYHA III-IV) included. The mean QRS duration was 150±8msecs. During a 12-month follow-up, 22 pts (65%) had responded. The ejection fraction before CRT was 22±4% and increased to 29±3% after CRT (p<0.05). The presence of ICR was the strongest predictor of response to CRT (area under the curve, 0.92; p<0.005) compared with interventricular dysynchrony indice (area under the curve, 0.76; p<0.05) and intraventricular dysynchrony indice (area under the curve, 0.81; p<0.05).Conclusions: Inotropic contractile reserve was a stronger predictor of CRT response than conventional and TDI indices. Therefore, DSE plays a pivotal role in identifying responders to CRT.

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