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[Ventricular and myocardial function in mitral regurgitation (author's transl)]
Insights
Chronic mitral regurgitation leads to impaired myocardial function and reduced ejection fraction, despite normal cardiac output and afterload. Compensatory mechanisms include left ventricular hypertrophy and dilation, but these are insufficient to maintain normal heart function.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Chronic volume overload from mitral regurgitation significantly impacts left ventricular (LV) and myocardial performance.
- Understanding compensatory mechanisms is crucial for managing heart failure in these patients.
Purpose of the Study:
- To analyze left ventricular and myocardial performance in patients with chronic volume overload due to mitral regurgitation.
- To identify compensatory mechanisms and their relationship to heart failure severity.
Main Methods:
- Utilized biplane cineventriculograms, simultaneous pressure recordings, and thermodilution cardiac output measurements.
- Assessed left ventricular hypertrophy (LVMI), end-diastolic volume index (EDVI), ejection fraction (EF), and afterload (sigma tej, sigma max).
Main Results:
- Patients maintained a normal cardiac index (CI) despite a significant regurgitant fraction (49%).
- Left ventricular hypertrophy and dilation were the primary compensatory mechanisms, with preload playing a minor role.
- Ejection fraction was depressed (54%) despite normal afterload, indicating impaired myocardial function.
Conclusions:
- Mitral regurgitation leads to impaired myocardial function and reduced ejection fraction, even with preserved cardiac output.
- Left ventricular hypertrophy and dilation are key but ultimately insufficient compensatory responses.
- Myocardial function is more compromised in mitral regurgitation compared to aortic regurgitation at similar heart failure stages.
Abstract:
Left ventricular and myocardial performance were analyzed in 9 patients with chronic volume overload by mitral regurgitation from biplane cineventriculograms, simultaneous pressure recordings and cardiac output (thermodilution method) determinations. In spite of a considerable regurgitant fraction (49 +/- 17% of total stroke volume) cardiac index on the average is normal (CI = 3.3 +/- 0.7 l . min-1). The main compensatory mechanism to maintain cardiac ouput in hypertorphy (WED = 1.1 +/- 0.2 cm; LVMI = 216 +/- 62 g . m-2; LVMI/EDVI = 1.3 +/- 0.3 g . ml-1) and dilatation (EDVI = 163 +/- 37 ml . m-2). An increase of preload is of minor importance (PLVED = 15 +/- 7 mmHg; sigma ED = (40 +/- 19) x 10(3) dyn . cm-2). Left ventricular enlargement and wall mass are related to the degree of clinical heart failure (NYHA). Enddiastolic volume on the average is more increased than total stroke volume (89 +/- 31 ml . m-2). Ejection fraction (EF = 54 +/- 7%) was depressed despite a normal afterload (sigma tej = (171 +/- 37 x 10(3) dyn. cm-2; sigma max = (247 +/- 48 x 10(3) dyn . cm-2). The reduced ejection fraction and diminished myocardial power are related to an impairment of myocardial function (VMW . sigma tej = (83 +/- 39) x 10(3) dyn . cm-2 . s-1; VMW . sigma tej/ln sigma ED = 7.9 +/- 3.6 x 10(3) dyn . cm-2 . s-1). In comparable degrees of heart failure myocardial function is more compromised in patients with mitral than with aortic regurgitation.