Illustration of a Normal Heart vs. Heart with Dilated Cardiomyopathy The progression of heart failure is associated with left ventricular remodeling, which manifests as gradual increases in left ventricular end-diastolic and end-systolic volumes, wall thinning, and a change in chamber geometry to a more spherical, less elongated shape. This process is usually associated with a continuous decline in ejection fraction. The concept of cardiac remodeling was initially developed to describe changes that occur in the days and months following myocardial infarction. Compensation effects As DCM progresses, two compensatory mechanisms are activated in response to impaired myocyte contractility and reduced stroke volume: * Frank-Starling law * Neurohormonal feedback, via activation of the sympathetic nervous system and the renin-angiotensin system. These responses initially compensate for decreased cardiac output and maintain those with DCM as asymptomatic. Eventually, however, these mechanisms become detrimental, intravascular volume becomes too great, and progressive dilatation leads to heart failure symptoms. Computational models Cardiac dilatation is a transversely isotropic, irreversible process resulting from excess strains on the myocardium. A computation model of volumetric, isotropic, and cardiac wall growth predicts the relationship between cardiac strains (e.g. volume overload after myocardial infarction) and dilation using the following governing equations: where is elastic volume stretch that is reversible and is irreversible, isotropic volume growth described by: where is a vector, which points along a cardiomyocyte's long axis and is the cardiomyocyte stretch due to growth. The total cardiomyocyte growth is given by: The above model reveals a gradual dilation of the myocardium, especially the ventricular myocardium, to support the blood volume overload in the chambers. Dilation manifests itself in an increase in total cardiac mass and cardiac diameter. Cardiomyocytes reach their maximum length of 150 m in the endocardium and 130 m in the epicardium by the addition of sarcomeres. Due to the increase in diameter, the dilated heart appears spherical in shape, as opposed the elliptical shape of a healthy human heart. In addition, the ventricular walls maintain the same thickness, characteristic of pathophysiological cardiac dilation. Valvular effects As the ventricles enlarge, both the mitral and tricuspid valves may lose their ability to come together properly. This loss of coaptation may lead to mitral and tricuspid regurgitation. As a result, those with DCM are at increased risk of atrial fibrillation. Furthermore, stroke volume is decreased and a greater volume load is placed on the ventricle, thus increasing heart failure symptoms.
causes of Cardiomegaly
causes of Cardiac tamponade
types of Cardiomegaly
causes of Ventricular tachycardia
causes of Hyperthermia
causes of Mitral insufficiency
causes of Fat embolism syndrome
causes of Mitral valve stenosis