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Left ventricular mechanics in dilated cardiomyopathy
Insights
Idiopathic dilated cardiomyopathy (IDC) alters left ventricular (LV) shape, increasing wall stress and indicating depressed contractile function. This study quantifies these mechanical changes in IDC patients.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Idiopathic dilated cardiomyopathy (IDC) is characterized by left ventricular (LV) dysfunction.
- The impact of altered LV chamber geometry on mechanical evaluation in IDC remains unclear.
Purpose of the Study:
- To investigate the influence of altered LV chamber shape on the assessment of LV mechanics in patients with IDC.
- To quantify differences in LV wall stress and contractile function between IDC patients and healthy individuals.
Main Methods:
- Simultaneous LV pressure and M-mode echocardiography were used in 9 IDC patients and 7 controls.
- LV meridional and circumferential wall stress were derived using LV pressure, dimensions, and angiographic data.
- LV load was altered using phenylephrine and nitroglycerin to construct stress-dimension and stress-shortening relations.
Main Results:
- IDC patients exhibited larger LV volumes, increased LV mass, and a more spherical LV shape.
- Both end-systolic meridional and circumferential wall stresses were elevated in IDC patients.
- The slope of the circumferential end-systolic stress-dimension relation was decreased in IDC, and the stress-shortening relation was displaced downward, indicating depressed contractility.
Conclusions:
- Altered LV chamber shape in IDC significantly impacts the evaluation of LV mechanics.
- Elevated wall stress and depressed contractile function are key mechanical abnormalities in IDC.
- These findings highlight the importance of considering geometric changes in assessing cardiac function in IDC.
Abstract:
The influence of altered chamber shape on the evaluation of left ventricular (LV) mechanics in idiopathic dilated cardiomyopathy (IDC) is unknown. Nine patients with IDC and 7 subjects with normal LV function were studied with simultaneous LV pressure and M-mode echographic recordings in order to derive LV meridional wall stress. The major axis of the left ventricle, determined from the left ventriculogram at rest, allowed for derivation of circumferential wall stress. The IDC group was characterized by larger end-diastolic and end-systolic LV volumes, increased LV mass, depressed angiographic ejection fraction and more spherical LV chamber shape. Both end-systolic meridional (114 +/- 30 kdyne/cm2) and circumferential (251 +/- 73 kdyne/cm2) wall stresses were elevated in patients with IDC, although the ratio of these stresses was less than normal (2.2 +/- 0.1 vs 2.7 +/- 0.2, respectively). LV load alteration with phenylephrine or nitroglycerin allowed for construction of end-systolic stress-minor-axis dimension and end-systolic stress-minor-axis shortening relations. Similar mean slopes of the meridional end-systolic stress-dimension relation were noted in IDC and normal subjects, although the line was displaced to the right in IDC. The slope of the circumferential end-systolic stress-dimension relation was, however, decreased in patients with IDC. Moreover, the end-systolic stress-fractional minor-axis shortening relation in patients with IDC was displaced downward from the normal relation supporting depressed contractile function in these IDC patients.(ABSTRACT TRUNCATED AT 250 WORDS)