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Chapter 12 Pericardial Diseases

CHAPTER 12 PERICARDIAL DISEASES

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FIGURE 12-10 Pulmonary vein and hepatic vein Doppler patterns of tampon- ade. A: Diastolic forward pulmonary venous flow decreases ( single arrowhead ) after inspiration ( Insp ) and increases ( double arrowheads ) after expiration ( Exp ). B: The hepatic vein has a marked decrease in diastolic forward flow and an increase in diastolic reversals ( DR ) after expiration. D , diastolic flow; S , systolic flow. (From Oh JK, Hatle LK, Mulvagh SL, et al. Transient constric- tive pericarditis: Diagnosis by two-dimensional Doppler echocardiography. Mayo Clinic Proceedings, 1993;68:1158–1164. Used with permission of Mayo Foundation for Medical Education and Research.)

valves are also reflected in the pulmonary and hepatic venous flow velocities as follows: an inspiratory decrease and an expiratory increase in pulmonary vein diastolic forward flow and an expiratory decrease in hepatic vein forward flow and an expiratory increase in expiratory reversal flow (Fig. 12-10). The presence of these typical Doppler velocity changes indicates hemodynamic com- promise due to pericardial effusion. Although there is a similarity between constriction and tamponade in terms of respiratory variation in ventricular filling, these filling patterns are different. In tamponade, due to increased intrapericardial pressure with decreased transmural pres- sure gradient, LV and RV filling are impeded throughout diastole, more so during early diastole, manifesting as a low mitral E velocity and E/A reversal (<0.8). In constric- tion, ventricular filling is generally restrictive (see below). Cardiac tamponade is relieved by removal of the peri- cardial fluid. Although pericardiocentesis is lifesaving, a blind percutaneous approach has a relatively high rate of complications, including pneumothorax, puncture of the cardiac wall, and death. Two-dimensional echocardiogra- phy can identify the optimal site of puncture (Fig. 12-11) by determining the thickness of the pericardial effusion envelope and its distance from the puncture site as well as monitor the results of the pericardiocentesis, usually from the subcostal window. The appropriate position of the peri- cardiocentesis needle within the pericardial space can be confirmed by imaging during injection of agitated saline. Figure 12-12 shows contrast in the pericardial space, not in the RV. At Mayo Clinic, most pericardiocentesis proce- dures are performed with 2D echocardiographic guidance. The most common locations for needle entry are the para- ECHOCARDIOGRAPHICALLY GUIDED PERICARDIOCENTESIS

(see below), the inspiratory fall of intrathoracic pressure is not fully transmissible to the LV in the presence of peri- cardial fluid (18). Thus, the pressure gradient for LV fill- ing is reduced. In contrast to constriction, where LV filling occurs primarily during early diastole (with the greatest limitation to filling occurring from mid to late diastole), LV filling in pure tamponade (without effusive-constrictive pericarditis) is impaired or reduced during early diastole due to increased intrapericardial pressure, and late filling with atrial contraction is increased (Fig. 12-8B). Moreover, during inspiration, the fall of intrapleural pressure aug- ments systemic venous return. Due to impairment in the right heart’s capacity to dilate from the effusion and the concurrent reduction in LV filling gradient during inspira- tion, the interventricular septum shifts from right to left to accommodate the increase in systemic venous return. During expiration, less venous return to the right heart and recovery of the LV pressure gradient for filling shift the septum rightward, increasing LV filling. Consequently, LV stroke volume and systolic BP are reduced during inspira- tion, and vice versa during expiration. Competitive filling of the RV and LV during respiration forms the basis for pulsus paradoxus in cardiac tamponade. In constriction, increased ventricular interdependence is initiated by the respiratory variation in left ventricular filling, as opposed to RV filling in tamponade (19). The reciprocal changes in mitral and tricuspid flow velocities in tamponade are closely coupled to respira- tory phase and therefore greatest on the first beats of inspiration and expiration. Defining percentage velocity change as [(velocity in expiration − velocity in inspira- tion)/velocity in expiration], the American Society of Echocardiography has recommended these thresholds as diagnostic of tamponade: a 30% change in mitral E veloc- ity and 60% change in tricuspid E velocity (1). Respiratory changes in flow velocity across the mitral and tricuspid &RS\ULJKW ‹

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