Late systolic stress-diameter relation in patients with aortic valve disease before and after valve replacement
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The end-systolic pressure-diameter ratio (Ees) and the maximal pressure-diameter ratio (Emax) during systolic ejection were determined in 10 control patients and 25 patients with aortic valve disease before and 18 months after successful valve replacement. The pressure-diameter ratio was determined from simultaneous M-mode echocardiograms and high-fidelity pressure measurements. A new index of myocardial contractility, as proposed by Pouleur and co-workers, was assessed from the late systolic stress-diameter relationship during one single heart cycle. The slope of this stress-diameter relationship was used for determination of myocardial contractility. Meridional wall stress was calculated from echopressure measurements at time intervals of 5 to 10 msec. The aortic valve patients were divided into two groups according to the preoperative angiographic ejection fraction: group 1 (ejection fraction ≧57%) consisted of 16 patients and group 2 (ejection fraction <57%) of 9 patients.
Standard hemodynamics showed a significant decrease in left ventricular end-diastolic pressure from 18 to 11 mm Hg in group 1 (P<0.01) and from 16 to 12 mm Hg (NS) in group 2. Peak systolic pressure decreased from 186 to 135 mm Hg (P<0.01) in group 1 and from 155 to 140 mm Hg (NS) in group 2. Left ventricular end-diastolic volume decreased from 137 to 105 ml/m2 in group 1 and from 225 to 150 ml/m2 in group 2 (P<0.05) whereas left ventricular ejection fraction remained unchanged in group 1 (67 versus 65%) and increased slightly in group 2 (45 versus 51%) following surgery. Emax and Ees were preoperatively significantly decreased in group 2 when compared to group 1. Postoperatively, Emax and Ees were no longer significantly different between the two groups although left ventricular ejection fraction remained significantly depressed in group 2 after surgery when compared to group 1. The slope of the late systolic stress-diameter relationship (β) and the diameter at zero stress (D0) did not show any difference between the two groups pre- as well as postoperatively.
Thus it is concluded that Ees and Emax might help to identify myocardial dysfunction in preoperative patients with aortic valve disease. However, in the presence of persistent myocardial dysfunction, as evaluated from systolic ejection fraction, following successful valve replacement, both Ees and Emax do not allow to identify patients with postoperative depressed myocardial function. The failure of the slope of the late systolic stress-diameter relationship to distinguish between patients with normal and decreased ejection performance is due to an intrinsic relation between stress and diameter. Hence this index cannot be recommended for the assessment of contractility in patients with aortic valve disease.
Key wordspressure-diameter ratio late systolic stress-diameter relationship aortic valve disease aortic valve replacement myocardial function
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