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Is standardization of left ventricular chamber elastance necessary?
1Department of Internal Medicine, University of Michigan, Ann Arbor.
Circulation
|June 1, 1990
Summary
Standardizing maximum time-varying elastance (Emax) for heart size is not essential for differentiating preserved versus depressed left ventricular (LV) systolic performance in adult patients. Heart size contributes minimally to reduced LV elastance, making standardization unnecessary for clinical assessment.
Area of Science:
- Cardiology
- Physiology
Background:
- Left ventricular (LV) chamber elastance is linked to heart size, prompting hypotheses about standardizing maximum time-varying elastance (Emax).
- Differentiating preserved from depressed LV systolic performance may require accounting for LV end-diastolic volume (EDV).
Purpose of the Study:
- To test the hypothesis that Emax standardization is necessary for accurate LV systolic performance assessment.
- To evaluate the independent relationship between Emax, LV end-diastolic volume (EDV), and cardiac pathology.
Main Methods:
- Studied 66 patients (25 normal, 41 with cardiac pathology) using micromanometer-determined LV pressures and radionuclide angiograms.
- Analyzed Emax and EDV data under various LV loading conditions using multiple regression and logarithmic transformations.
- Applied mathematical standardization to Emax to assess the impact of heart size.
Main Results:
- Emax was independently related to LV end-diastolic volume (r = -0.69).
- Distinct linear relations between lnEmax and lnEDV were observed in normal and cardiac pathology groups.
- Standardization for heart size did not significantly alter the classification of LV systolic performance (concordance k = 0.73).
- Heart size contributed only an estimated 14% to the reduction in Emax in patients with cardiac pathology.
Conclusions:
- LV chamber elastance (Emax) calculated via radionuclide angiography is independently related to LVEDV.
- Mathematical standardization of Emax for heart size does not significantly change the dichotomization of patients into preserved or depressed LV systolic performance groups.
- Heart size has a relatively small impact on reduced LV systolic performance indices, suggesting standardization may not be clinically necessary for adult patients.