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Figure 1 Change in left ventricular (LV) end-systolic volume and severity of systolic asynchrony as measured by asynchrony index for heart failure patients with narrow (solid triangles) and wide (open triangles) QRS complexes. The regression lines for both groups nearly superimpose on each other with nearly identical slopes. Wide QRS: r = –0.71, p < 0.001; narrow QRS: r = –0.61, p < 0.001.