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Figure 2 Left ventricular pressure (LVP)–first derivative of left ventricular pressure (dP/dt) relationship (phase loop). (A) A loop obtained from a patient with inertia force. (B) A loop obtained from a patient without inertia force. The negative inverse slope of the best linear-fitting line between the points a and b is equal to the time constant of exponential pressure decay during isovolumic relaxation (Tp). The Tp was 56.3 ms in A and 83.1 ms in B. The area in red divided by the vertical distance between P0,0 and point d is equal to the amount of pressure decay augmented by the effect of the inertia of blood flowing out of the LV, and is defined as the inertia force. The inertia force in A was 3.6 mm Hg, and 0.12 mm Hg in B.
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