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Noninvasive Assessment of Regional and Global Myocardial Contractility in Normal Control Subjects and in Patients
Michael J. Domanski1, Dean Follman, Marsha Kravitz
1Clinical Trials Group, National Heart, Lung and Blood Institute, Bethesda, MD 20892-7936.
Insights
This study introduces a novel noninvasive method to assess myocardial contractility without drugs. The ejection fraction/afterload relationship effectively differentiates dilated cardiomyopathy from healthy hearts.
Area of Science:
- Cardiology
- Physiology
- Medical Imaging
Background:
- Assessing myocardial contractility typically requires interventions to alter cardiac load.
- A noninvasive method to evaluate contractility independent of pharmacological manipulation is needed.
Purpose of the Study:
- To develop and validate a noninvasive approach for assessing regional and global myocardial contractility.
- To determine if the ejection fraction/afterload relationship can differentiate healthy individuals from those with dilated cardiomyopathy (DCM).
Main Methods:
- Echocardiography, sphygmomanometry, and carotid pulse tracings were used in 34 healthy adults and 5 DCM patients.
- Left ventricular segments were analyzed to determine shortening, shortening rate, and ejection fraction/afterload relationships.
- Discriminant analysis was employed to compare patient groups.
Main Results:
- The ejection fraction/afterload relationship was significantly different in DCM patients compared to controls.
- This relationship proved to be the most sensitive indicator for differentiating between the groups.
- Linear and nonlinear relationships were observed for endocardial and mid-wall shortening in control subjects.
Conclusions:
- The developed noninvasive method allows for individual contractility assessment without drug interventions.
- Load variation is derived from intrinsic left ventricular wall stress gradients.
- The approach is applicable to patients with segmental contractile abnormalities.
Abstract:
The aim of the present study was to develop a new noninvasive approach for the assessment of regional and global myocardial contractility without the need for pharmacological intervention to alter load. Thirty-four healthy adults and five adults with dilated cardiomyopathy (DCM) were studied. Patients with diabetes mellitus and hyperthyroidism were eliminated from the study. The remainder underwent echocardiography, sphygmomanometric blood pressure determination, and carotid pulse tracings. Left ventricular cross section in the parasternal long-axis four- and two-chamber views was divided into 20 segments. Associated measurements of end-systolic pressure and left ventricular ejection time enabled shortening, shortening rate, and ejection fraction/afterload relationships to be determined. A discriminant analysis showed that the ejection fraction/afterload relationship in patients with DCM differed substantially from that of control subjects and was the most sensitive in this regard. Endocardial shortening, mid-wall shortening, and ejection fraction/afterload relationships demonstrated linearity or nonlinearity for control subjects. This study thus permits the assessment of contractility in individual subjects without the need for drug interventions because load alteration stems from the variation of wall stress from base to apex in the left ventricle. More importantly, the approach may be applied to patients with segmental abnormalities of contractile function.