TAILIEUCHUNG - Cardiovascular Imaging A handbook for clinical practice - Part 10

Phụ thuộc lẫn nhau này hiện diện trong những trường hợp bình thường trong quá trình thở và là phóng đại bởi sự tích tụ chất lỏng trong màng ngoài tim hoặc xơ cứng màng ngoài tim | Myocarditis and pericardial disease 265 Figure Transverse CMR image showing normal pericardium over the right ventricle. lar interdependence or coupling exists . the more space one side of the heart occupies the less is available for the other side leading to increased diastolic pressures in the contralateral part. This interdependence is present in normal circumstances during breathing and is exaggerated by fluid accumulation in the pericardium or by pericardial stiffening. The depth and speed of respiration also significantly determines the size of the effect on cardiac hemodynamics and should be recorded during imaging. During inspiration pressure in the thorax and the pericardium drops and flow towards inferior vena cava and from the right heart increases while the reverse occurs on the left side during expiration the opposite changes take place. While cardiac tamponade increases distension pressures throughout the entire filling period the restraint in CP7 is nearly absent during early filling but rapidly increases thereafter giving rise to the characteristic square root sign on LV pressure traces. Another characteristic of CP is the belated transmission of changes in intrathoracic pressures to the intrapericardial structures creating the exaggerated acute changes in filling gradients at the onset of the inspiratory and expiratory motions. During inspiration the increased venous return is not coupled to the characteristic drop in right atrium RA pressure and systemic venous pressure may actually increase . Kussmaul sign in the superior caval vein SVC Fig. . Because respiratory interdependence in CP decreases at higher absolute left atrium LA pressures and with the severity of constriction examining a patient in the upright position decrease of filling pressures can unmask interdependence in such cases. 266 Chapter 21 Figure Diameter of the inferior vena cava IVC flow in the superior vena cava SVC and in a hepatic vein during inspiration .

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