ORIGINALARTICLES TheLinearity oftheEnd-systolic Pressure-Volume Relationship inMan andItsSensitivity forAssessment ofLeftVentricular Function

SUMMARY Thelinearity andsensitivity oftheend-systolic pressure-volume (P-Ve,) relation totheinotropic state oftheleft ventricle wereinvestigated in11patients withcoronaryheart disease andonepatient withcongestive cardiomyopathy. Tominimize autonomic reflex responses, propranolol, 0.15mg/kg,and atropine, 1mg,wereadministered i.v. atthebeginning ofthestudy. Threeventriculograms wereperformed: at rest, after oral isosorbide dinitrate, 10mg (systolic pressuredecrease15mm Hg),andduring infusion of methoxamine, 2mg/min(systolic pressureincrease > 10mm Hg). Thethree points oftheP-Ve, relation showed linearity (r 0.96). Therelation between theslope kofthePVe,relation andtheleft ventricular ejection fraction atrest was bestdescribed byan exponential function (r= 0.94). Theuseofpeaksystolic pressureinstead ofend-systolic pressureshowed equally goodresults. The intercept oftheP-V,, line on theabscissa, whichrepresents thetheoretical end-systolic volumeatzero pressure,was notrelated totheejection fraction undercontrol conditions. TheP-Ve, relation inpostextrasystolic beats was displaced toward theleft (smaller end-systolic volumes) andbecamesteeper. MYOCARDIAL fiber shortening isdetermined by preload, afterload andcontractility, andend-systolic fiber length isinversely proportional toafterload.' In theisolated left ventricle, end-systolic fiber length is linearly related toend-systolic tension.2 Intheexperimental animal, theisolated left ventricle also shows a linear end-systolic pressure-volume (P-Ves) relationship that isnotdependent onpreload. Theslope ofthe P-Ve, relation isdetermined bythecontractile state andisincreased bypositive inotropic interventions.3 Although theconcept oftheP-Ve, relationship has