Year : 2011 | Volume
: 14 | Issue : 2 | Page : 82--84
Cardiac tamponade and clinical acumen
Shanelle Wijesuriya, Alain Vuylsteke
Department of Anaesthesia and Intensive Care, Papworth Hospital, Cambridge, United Kingdom
Department of Anaesthesia and Intensive Care, Papworth Hospital, Papworth Everard,Cambridge, CB23 3RE
|How to cite this article:|
Wijesuriya S, Vuylsteke A. Cardiac tamponade and clinical acumen.Ann Card Anaesth 2011;14:82-84
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Wijesuriya S, Vuylsteke A. Cardiac tamponade and clinical acumen. Ann Card Anaesth [serial online] 2011 [cited 2019 Nov 14 ];14:82-84
Available from: http://www.annals.in/text.asp?2011/14/2/82/81560
For millennia, medicine was practised without the aid of technology. Despite the passage of time, common principles in the field of medicine prevailed; defined by figures, such as the Greek physician Hippocrates in the Western World or Charaka in India. Homeostasis was recognized by Hippocrates as the "four humours" and by Ayurvedic practitioners as the three "doshas" - all of which needed to be perfectly balanced for health, but were not in disease. This imbalance was detected through direct observation and precise documentation of symptoms. Thorough examination of the body and the environment formed vital clues for unravelling the disease process. It was based on this collection of signs and symptoms that diagnoses were made. Clinical wisdom was the most powerful tool available to medical practitioners.
Modern medicine appears at times to be far removed from these basic principles of direct observation. Technological novelties have allowed a rapid advancement of our diagnostic capabilities but perhaps at the cost of lost clinical acumen. A prime example is the intensive care unit. In this environment, all clinical parameters that were previously examined are directly and dynamically measured through electrodes, catheters, and other devices. The art of clinical examination has been diminished as invasive monitoring has emerged. Any change in homeostasis is now a mere numerical disturbance, sometimes made obvious by a clinical deterioration. But while technology has rapidly become the diagnostic weapon of choice, there are still important scenarios where clinical expertise is vital for attaching significance to a diagnosis and guiding decision-making.
Cardiac tamponade is a recurring complication in any cardiothoracic surgical intensive care unit.
It is defined as the compression of the heart by a pericardial collection, restricting diastolic filling and leading to impaired pump function. The collection does not have to be circumferential or large to cause compromise. A small loculated collection compressing a single chamber might be life threatening. , The diagnosis of a pericardial collection and its significance represents a challenge in patients after open cardiac surgery.
Clinical Uncertainty in Cardiac Tamponade
Beck described in 1935 the 3 most common clinical signs of cardiac tamponade: hypotension, raised central venous pressure, and soft, muffled heart sounds. To these we can add pulsus paradoxus, an exaggeration of the normal decline in blood pressure during the inspiratory phase of respiration, as well as chest pain, breathlessness, tachycardia, and oliguria.
An acute collection of rapidly increasing size will lead to Beck's clinical picture, but this might not be seen after cardiac surgery, if the collection is slowly accumulating and peaking in size by about day 10.  The clinical presentation can be misleading with this insidious onset. Many other factors can perpetuate uncertainty, such as raised central venous pressure in patients with chronic congestive heart failure or pulsus paradoxus in patients with obstructive airways disease. Signs can also be absent. Central venous pressure may not be elevated in localized left-sided tamponade and pulsus paradoxus can be absent in tamponade amongst patients with positive pressure ventilation or significant aortic regurgitation.  Several studies have indeed shown the poor positive predictive value of "traditional" signs, including hypotension.
Chuttani et al. retrospectively evaluated 29 patients who had tamponade following cardiac surgery, and only 24% and 48% of patients had hypotension and pulsus paradoxus, respectively. A retrospective analysis by Tsang et al of 245 cases of echocardiography-guided pericardiocentesis for significant postoperative effusion (226 cases were postcardiac surgery) showed that only 27% of patients were hypotensive, 39% of patients had elevated central venous pressure, and 17% of patients had pulsus paradoxus. Price et al. found that of 30 patients with cardiac tamponade occurring more than 72 h after surgery, only 1 was hypotensive and none had raised central venous pressure. In the absence of these signs, the diagnosis of tamponade can be missed. Russo et al. studied 510 consecutive patients after cardiac surgery, 10 of whom had cardiac tamponade. Seven diagnoses were mistaken for either pulmonary embolism (3), myocardial infarction (1), congestive heart failure (1), or sepsis (1). Only 5 of the 10 patients had raised central venous pressure! So while the clinical presentation is variable, it is always important to consider cardiac tamponade and/or the presence of a pericardial collection as a reason for a patient's deterioration or lack of improvement after cardiac surgery. Imaging, such as echocardiography, has proven vital on the cardiac intensive care unit to provide more information.
Technology and Cardiac Tamponade
The "classical" echocardiographic features of cardiac tamponade have been defined. These include right ventricular diastolic collapse, right atrial systolic collapse, an enlarged nonpulsatile inferior vena cava, a "swinging" heart and/or reciprocal variation in transmitral and transtricuspid flow with inspiration in the presence of a pericardial collection. But the postoperative period provides several obstacles to the execution and interpretation of imaging. The presence of mediastinal drains limits windows in transthoracic imaging, particularly the subcostal view. Positive end expiratory pressure (PEEP) alters transvalvular inspiratory flow making true variations from baseline difficult to judge. Body habitus makes visualization difficult. A sonulucent space adjacent to the heart could be a pleural effusion and not necessarily a pericardial collection. Additionally, echocardiography is notoriously user-dependent and findings can vary between operators. So when "classical" echocardiographic signs are absent, a small thrombus or collection on imaging may be thought of as benign. In reality these "classical" findings have a poor negative predictive value for tamponade. Price et al. conducted a retrospective analysis of 2297 adult cardiac surgical patients, 148 of whom had surgically proven tamponade. They showed that of those that presented early (within 72 h) transthoracic echocardiography failed to visualize 60% of collections and 79% showed none of the classical echocardiographic features of tamponade. Pre-existing structural disease of the heart can alter the response to increased intrapericardial pressure, making echo findings difficult to interpret.
Imren et al. at the Gazi University Medical Faculty studied 1550 patients after open heart surgery. Sixty-two patients who had suspected tamponade underwent both transthoracic (TTE) and transesophageal echocardiography (TOE). Any patients with positive TTE or TOE findings went on to the operating theatre for surgical evacuation and confirmation of tamponade. More than 50% of the patients with negative transthoracic findings had positive findings on TOE that were surgically confirmed. The negative predictive value of transthoracic imaging was estimated to be 41% - not even as good as tossing a coin!
But while negative TTE findings can be falsely reassuring, the other issue to consider is the significance of a positive finding. The visualization of large amounts of fluid in the pericardial space, particularly if slowly accumulating, may not be hemodynamically significant. A globally distributed collection may produce only small increases in intrapericardial pressure. Evidence suggests that the small loculated collection compressing a single chamber is more common in tamponade.  Furthermore, Gillam et al showed right atrial collapse in 19 of 19 patients with cardiac tamponade, but also in 19 of 109 patients without tamponade.  Studies in animals have shown that right-sided collapse occurs at lower intrapericardial pressures in hypovolaemic cases (as in dehydration or blood loss) without cardiac tamponade. 
The combination of poor negative predictive value of TTE findings of tamponade with atypical clinical features represents an interesting dilemma. There will thus be a cohort of patients with hemodynamic deterioration with no or minimal findings on echocardiography. Another cohort will have positive echo findings of no hemodynamic significance. Some will have an "apparent" lack of compromise as highlighted by Chuttani and Tsang where less than half of the patients with tamponade were hypotensive.
The Cross-Road between Technology and Acumen
A diagnosis of tamponade is important. It carries a high risk of increased morbidity and mortality. Surgical evacuation provides a swift remedy. But committing a cardiac patient with likely significant comorbidity to further open cardiac surgery is not an easy decision.
The key to decision-making lies in a firm understanding of the physiology of tamponade. By the time a low-output state is reached, a series of adaptive changes have occurred-from a reduction in diastolic filling, to a compensatory tachycardia to increased systemic venous resistance to maintain mean arterial pressure. Recognizing that tamponade is a dynamic process may be useful when a patient appears clinically well despite a large collection on echocardiography.
We have seen those patients not returning to theatre for surgical evacuation because of normal echocardiographic findings, or those for which echocardiographic findings were dismissed due to perceived clinical well-being. Too often, it is the reliance on one of the two that causes trouble. Modern clinical acumen in all areas of medicine, including intensive care, must come from the integration of clinical observation and technological support.
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