Changes ofLeftVentricular Diastolic Function inExercising DogsWithout and WithIschemia

Leftventricular (LV)diastolic function intheabsence andpresenceofregional ischemia was examined in eightconscious dogschronically instrumented withultrasonic devices for measuring LV wallthickness andvolume.Duringtreadmill exercise, ischemia was induced (hydraulic occluder) toproduce lessthan10%systolic wallthickening intheischemic zone.LV filling was assessed bythepeakfilling rate(PFR), mean filling rates inthefirst andsecond halves of filling (mFR, andmFR2), an early filling indexfrommitral valveopening tominimal diastolic pressure(PDm),andthepercentage ofatrial filling. Also, LVrelaxation (X-) andwall thinning ratesduring isovolumetric relaxation andthefirst andsecondhalves ofthefilling phase wereassessed. During control exercise without ischemia, PDm decreased by2.61mm Hg (p<0.05) to-1.1mm Hgandthere was a downwardshift oftheentire LV diastolic pressurevolume(P-V) curve.TheLVrelaxation rate, PFR,mFR,, andmFR2wereenhanced. Early filling was increased by116%,thepercentage ofatrial filling by118%,andoverall diastolic filling by 23%despite a63%decrease inthefilling period. During ischemic exercise, systolic function was depressed comparedwiththeresting state, PDm increased by4.84mm Hg (p<0.005) associated withapronounced rightward andupwardshift oftheearly portion oftheP-Vcurve. LVrelaxation rate, PFR,andmFR1werereduced, theearly filling index fell sharply by62%but percentage ofatrial filling was unchanged, whileoverall diastolic filling decreased by30%.The thlinning rateofthecontrol wallwas enhanced, whereas thatofischemic wall was depressed. Multiple factors contributed tothemarkedly impaired earlyandoverall diastolic LV filling during ischemia, including impaired systolic function, reduced relaxation rate, nonuniformity ofwallmotion, an upwardshift oftheearly diastolic P-Vcurve,andabsence ofacompensatory increase inlate diastolic filling. (Circulation 1990;81:1058-1070)