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Figure 3 Effects of carvedilol, metoprolol controlled release/extended release (CR/XL), and no treatment on left ventricular (LV) stroke work, myocardial oxygen consumption (MvO₂), and LV mechanical efficiency. Although both treatments had comparable effects on MvO₂, carvedilol was associated with greater increases in stroke work and mechanical efficiency. Cessation of pacing alone had no effect. The indicated p values represent the differences in the carvedilol response and metoprolol response. *p < 0.05 compared with before treatment. Open bars = before treatment; solid bars = after treatment. Carv = carvedilol; Con = control subjects; Met = metoprolol.