When fluid accumulates slowly, the parietal pericardium can stretch to accommodate large volumes of fluid. However, if the development and accumulation of the effusion is very rapid or the volume exceeds the capacity of the pericardial space to stretch to contain the volume, increases in intrapericardial pressure begins to impact intracardiac pressure, elevation and equalization of diastolic intracardiac and pericardial pressures, decrease cardiac output, and exaggerated inspiratory decrease in systolic pressure (> 10 mm called pulsus paradox)4,5 (Figure 106–7).
Pericardial pressure. (Reproduced with permission from Hoit JP, Rhode EA, Kines H: Pericardial and ventricular pressure, Circ Res 1960 Nov 1;8(6):1171-1181.)
Circumstances that can lead to pericardial tamponade include all those that cause pericardial effusions including uremic renal failure, hypothyroidism, coronary vessel perforation during percutaneous interventions in the catheterization laboratory, a bleed following cardiac surgery, rupture or dehiscence following valve surgery or aortic dissection, bleeding into the pericardium from a neoplasm, infection (viral, bacterial, fungal, tubercular), or a marked inflammatory response.1 One study of 173 patients who underwent pericardiocentesis cited the etiologies as malignant (33%), acute or chronic pericarditis (26%), trauma (12%), uremia (6%), postpericardiotomy (5%), infection (5%), collagen vascular disease (3%), and radiation (2%).8
Tamponade following cardiac surgery may be due to bleeding from anticoagulants for prosthetic valves, delayed cessation of antiplatelet drugs, oozing from vascular or aortic anastomoses, or irritation from chest tubes. Loculated effusions may create regions of focal cardiac tamponade that may present with hypotension, but difficult to diagnose unless suspected, especially after cardiac surgery.
Clinically, patients with tamponade may have dyspnea, weakness, tachycardia, and hypotension. On anterior-posterior (AP) x-ray, a large cardiac silhouette, projecting a “water bottle-shaped” heart, in a patient with clear lung fields suggests the presence of a pericardial effusion with at least 250 mL of fluid. An electrocardiogram (ECG) may show signs of pericarditis with sinus tachycardia, and PR depression in leads 2, 3, and aVF. A valuable ECG sign indicative of potential cardiac tamponade is electrical alternans. Computed tomography (CT) and magnetic resonance imaging (MRI) scans may show incidental large effusions suggestive of tamponade.5,9,10,11 If the patient is stable, hemodynamics in the catheterization laboratory will show equilibration of average diastolic pressure across the cardiac chambers produced by the extrinsic pericardial pressure and ventricular interdependence, an inspiratory increase on the right-sided pressures with a concomitant decrease on the left-sided filling pressures—pulsus paradoxus.
Echocardiography is the most expedient modality to diagnose pericardial effusion and confirm the presence of pericardial tamponade. Echocardiography demonstrates circumferential pericardial fluid and compressed cardiac chambers (Figures 106–8). Among echocardiographic signs, the most characteristic is the diastolic right atrial and right ventricular compression. Right atrial collapse may also be seen in patients with hypovolemia who do not have tamponade. With greater compression, the left atrium may also collapse, a more specific finding. The diastolic collapse of the right ventricle usually connotes large enough external pressure to impact stroke volume. Doppler of aortic or pulmonic systolic flow discloses marked respiratory variations: On inspiration, the right ventricle fills at the expense of the left ventricle, seen as increased peak filling pulsed-wave Doppler velocity; both the ventricular and atrial septa move sharply leftward, reversing on expiration when the left ventricle fills at the expense of the right ventricle (Figure 106–9). A greater than 25% change in peak Doppler flow velocity obtained from the left ventricular outflow track or through the aortic valve, obtained by pulsed Doppler in the apical 4-chamber/5-chamber view or of the pulmonic valve, may connote pericardial tamponade (Figure 106–10). Pulsus paradoxus may also be seen with pulmonary embolism, chronic asthma, chronic obstructive pulmonary disease (COPD) and croup, but may be absent in low cardiac output states. The absence of any cardiac chamber collapse has greater than 90% negative predictive value for cardiac tamponade.12
Ventricular interdependence: 2D echo demonstrating indentation of left ventricular (LV) interventricular septum due to inspiratory increase in right ventricular (RV) pressures.* pericardial effusion
M-mode echocardiogram demonstrates large anterior pericardial effusion (*), with ventricular interdependence: the right ventricle enlarges with inspiration, while the left ventricle (identified by the mitral valve) becomes smaller and the opposite occurs with expiration.
Transaortic Doppler flow in the left ventricular outflow track, demonstrating higher velocity with expiration and lower with inspiration, creating pulsus paradox (arrows).
Importantly, pericardial tamponade is a clinical diagnosis based on the presence of tachycardia and hypotension, which can be supported by echo/Doppler findings. Therefore, clinical suspicion of the presence of tamponade or the imminent development of tamponade is extremely important in prevention of acute cardiac collapse. Under certain circumstances, especially with hypertrophy of the left and/or right ventricle and pulmonary hypertension, which may be seen in hypertensive patients with chronic renal failure, who are prone to recurrent pericardial effusion, there may not be the typical findings of tamponade, because the ventricular hypertrophy limits the impact of the external compression on ventricle interdependence.
Management of Acute Cardiac Tamponade
Patients presenting with hypotension and tachycardia in which pericardial pressure from the volume of pericardial effusion causes cardiac compression have cardiac tamponade and require emergency pericardiocentesis that should be performed with echo guidance. The European Society of Cardiology’s recent position statement on the triage of patients with potential cardiac tamponade proposed a stepwise scoring system to triage patients requiring pericardiocentesis.13 The paper incorporates etiology, clinical presentation, and imaging findings (with primary emphasis on echo findings) to determine whether urgent pericardiocentesis, surgical approach, or intervention can be delayed14 (Figure 106–11).
Triage strategy for urgent management of cardiac tamponade: European Society of Cardiology Working Group on Myocardial and Pericardial Diseases.14 (Reproduced with permission form Ristic AD, Imazio M, Adler Y, et al. Triage strategy for urgent management of cardiac tamponade: a position statement of the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases, Eur Heart J 2014 Sep 7;35(34):2279-2284.)
Pericardial drainage may be performed in the catheterization laboratory with hemodynamic measurement, with sterile technique in which both transthoracic echo and fluoroscopy can be utilized. However, sudden circulatory collapse may mandate the use of pericardiocentesis with imaging where the patient presents, in the emergency ward, ICU, or in the regular ward bed. Surgical drainage may be required if drainage cannot be achieved by percutaneous needle, in the presence of an active intrapericardial bleed, cardiac trauma or laceration, or complicating aortic dissection.
Medical treatment of acute cardiac tamponade can briefly temporize, but even volume infusion may increase intracardiac volume and pressures, thus increasing pericardial pressure and interventricular dependence, exacerbating the hypotension. Mechanical ventilation with positive airway pressure should be avoided in patients with tamponade, because this decreases venous return and may potentiate hypotension.
Pericardiocentesis is the most expedient method to resolve the impending circulatory collapse.15 The immediate treatment of cardiac tamponade is drainage of the pericardial fluid by either needle pericardiocentesis or surgical pericardial window.
Relative contraindications include suspected effusion due to aortic dissection, traumatic hemopericardium, or myocardial rupture in which the pericardiocentesis may exacerbate the underlying condition that may be temporarily in equilibrium. Anticoagulation or bleeding dyscrasias are relative contraindications, depending on the acuity of the situation and the severity of bleeding disorder.