Heart imaging based on echocardiography, magnetic resonance imaging (MRI) and computed tomography (CT) is used to assess heart size and systolic and diastolic cardiac function. Using dedicated acquisition sequences, particularly MRI provides various information on myocardial structure and morphology, e.g. edema and diffuse or local fibrosis. MRI is the gold standard to measure cardiac size. Left ventricular volumes and myocardial mass can be assessed with high accuracy and reproducibility.
Based on these measurements, wall stress is calculated using a thick walled sphere model of the left ventricle that is derived from the law of LaPlace and allows arbitrary wall diameters. Wall stress appears to be a crucial prognostic determinant, i.e. increased wall stress propagates the vicious circle of ongoing ventricular dilatation in heart failure and is associated with an increased arrhythmia risk following activation of stretch-associated myocardial ion channels. Thus, examination of wall stress has been envisaged as crucial prognostic determinant that requires further research.
Wall Stress of the Heart
Thick-walled sphere model that is used to calculate left ventricular wall stress. The model is derived from the law of LaPlace and allows wall stress calculation for arbitrary wall diameters.
Therefore, the wall stress index (σi) was introduced.
Increased wall stress is associated with variety of adverse consequences, e.g., propagation of the vicious circle of heart failure and dilatation, and the arrhythmia risk is increased by opening of stretch-activated cardiomyocyte ion channels. This may be associated with an unfavourable prognosis.
Cardiac Magnetic Resonance Imaging of the Heart
Cines images of a normal healthy heart (left), of a patient with dilative cardiomyopathy (middle) and a patient with pericardial effusion (right).
Late gadolinum enhancement (LGE) in a patient with Churg-Strauss syndrome. Usually, late gadolinium enhancement occurs streakly-like in various types of cardiomyopathies. In contrast, late enhancement predominantly occurs subebdocardial in Churg-Strauss disease as shown in long- (A) and short-axis (B). (Prof. Dr. Peter Alter, NICE-MR)
Large pericardial effusion as shown by CMR in 4-chamber (A), 3-chamber (B), short-axis (C) and 2-chamber (D) views.
Large ventricular aneurysm of the anterior wall and apex as shown in steady-state-free-precession-images (A). The aneurism is makedly thinned and shows late gadolinium enhancement in short axis views (B).