Methodology of the force-frequency relation with stress echo. Left, from upper to lower rows: systolic blood pressure (SP) by cuff sphygmomanometer (first row); LV end-systolic volumes (ESV) calculated with the biplane Simpson method (second row); heart rate increase (b.p.m.) during dobutamine infusion (third row); in the lowest row, the force-frequency relation built off-line with the values recorded at baseline (second column), and at different steps (third, fourth, fifth columns) up to peak exercise (seventh column). (A) Normal subject. An increased heart rate is accompanied by an increased systolic pressure with smaller end-systolic volumes (normal up-sloping PVR). (B) A subject with LV dysfunction (EF% = 32%) without dilation, no stress-induced ischemia. The PVR was biphasic, with an initial up-sloping followed by a later down-sloping trend, the critical heart rate (90 b.p.m.) was the heart rate beyond which SP/ESV index declined by 5%. The test was stopped at 20 gammas due to limiting symptoms (dyspnea). (C) A subject with post-MI depressed baseline LV function (EF% = 30%). An increased heart rate at peak exercise is accompanied by no changes in end-systolic volumes (abnormal flat PVR). (Modified from Grosu A, EHJ 2005). BSA = Body surface area; ESV = End-systolic volume; PVR = Pressure-volume relation; SP = Systolic pressure; SP/ESV = Systolic pressure/end-systolic volume ratio.