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Cardiac Tamponade: Niteesh K. Choudhry, MD, PhD, discusses the clinical examination for cardiac tamponade.
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Cardiac Tamponade: Niteesh K. Choudhry, MD, PhD, discusses the clinical examination for cardiac tamponade.
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Segment:0 .
>> I'm Joan Stephenson, Editor of JAMA's Medical News and Perspectives section. Today, I have the pleasure of speaking with Dr. Niteesh Choudhry about cardiac tamponade. Welcome, Dr. Choudhry. >> Thank you. Good afternoon. >> And why don't you introduce yourself to our listeners? >> Sure. So, my name is Niteesh Choudhry. I am an Internist and Hospitalist at Brigham Women's Hospital in Boston and an Assistant Professor at Harvard Medical School.
>> Dr. Choudhry, when should physicians consider cardiac tamponade, and what percentage of patients with pericardial effusion have cardiac tamponade? >> So, cardiac tamponade occurs when fluid is trapped in the pericardial space and that fluid compresses the heart and compromises cardiac output. And like all diagnoses really, tamponade should only be considered in the right clinical circumstance. So, these are really one of two possibilities. So, one are patients with the right symptoms and tamponade can have a wide variety of them but signs or symptoms such as hypotension or an elevated JVP may lead a physician to think about tamponade.
On the other hand, we sometimes find pericardial effusion on an echocardiogram and the clinician is left with the question, is this causing tamponade or are findings suggestive on the echocardiogram really-- are they clinically correlated or not. So, we don't really have a good estimate of how commonly tamponade occurs in patients with pericardial effusion. There are really no population-based studies which allow us to establish what would be considered a pre-test probability. We do know that it's relatively rare and so thinking about the context and the right clinical situation is extremely important.
>> Which symptoms increase the probability of cardiac tamponade? >> So, there are lots of symptoms that are classically associated with tamponade and these include shortness of breath, chest discomfort or pain, or fullness in the chest. There are other ones like nausea or abdominal pain or dysphagia that are all, again, in the realm of classic symptoms. But really for a symptom to increase the probability of tamponade, it would have to be relatively specific or have a high positive likelihood ratio.
And, unfortunately, there are really no rigorous studies identifying symptoms that have those particular test characteristics. >> When diagnosing tamponade, what do clinicians need to know about the Beck triad and how is it used to diagnose tamponade? >> Beck's triad is, again, a classic description of some of the signs and symptoms of tamponade and it was first described in the 1930s by this thoracic surgeon who was treating patients who had surgical tamponade such as from trauma or from myocardial or aortic rupture.
And the classic triad has three parts to it. So, one is falling arterial blood pressure or hypotension. The second is an increased jugulovenous pressure. And the third is a small or quiet heart, which we take to mean muffled or soft heart sounds. And so, as it turns out, the test characteristics of the entire triad haven't really been evaluated, but the individual components of them may not be as useful as we would like. So, hypotension and diminished heart sounds, for example, are both relatively insensitive and so their absence really doesn't reliably rule out this condition.
You know, said another way, there is lots of medical patients, so not the typical surgical patient, especially those who have underlying hypertension, who might actually be hypertensive with tamponade rather than hypotensive as Beck's triad might imply. >> Which history and physical examination findings are helpful when detecting cardiac tamponade and which ones are not so helpful? >> It's important when thinking about which features are helpful or not helpful to remind ourselves of what the literature contains. And the literature really only has studies of patients with effusions in whom the diagnosis of tamponade was being considered.
And in general, these types of studies tend to overestimate the sensitivity of signs and symptoms of tamponade in unselected groups of patients. That notwithstanding, there are several features among patients with known effusions that tend to occur commonly in patients who also have tamponade. And, as such, they're relatively sensitive or their absence helps make tamponade less likely. And there's five of them that are worth noting. The first is dyspnea or shortness of breath, which has a sensitivity of somewhere between 87- and 89%.
The second is tachycardia, which has a sensitivity of around 77%. The third is pulsus paradoxus or an exaggeration of the normal inspiratory decrease in blood pressure, which has a sensitivity of around 82%. An elevated jugulovenous pressure which has a sensitivity around 76%. And cardiomegaly on a chest x-ray, which has a sensitivity of about 89%. So, those five features tend to occur commonly and their absence, therefore, helps rule out the diagnosis of tamponade.
As I mentioned before, some of the parts of Beck's triad, in particular, hypotension and diminished heart sounds, as well as low voltage on an EKG, which are all classically thought to be associated with tamponade, tend to be not that useful since they're relatively insensitive. The only feature that might actually be useful for ruling in tamponade is pulsus paradoxus. And the number that we think about in terms of ruling in the diagnosis is a number greater than or equal to 12. So, a pulsus paradoxus greater than or equal to 12 has a positive likelihood ratio of about six, but this, of course, is only based on one relatively low-quality study.
>> What are the reference standard tests for cardiac tamponade? >> So, strictly speaking, the invasive reference standard for the diagnosis really requires you to measure intrapericardial and intracardiac pressures at the same time. And if we were to do this, you would find that intrapericardial, right atrial, pulmonary artery diastolic, and pulmonary capillary wedge pressures were all elevated and, in fact, equalize once you truly get into tamponade. But doing this, of course, is invasive.
And so, from a practical perspective, echocardiography is the diagnostic test that is used most often in patients for whom tamponade is being considered. It's important to remember that while echo is perhaps the non-invasive reference standard, having an effusion itself or the mere presence of an infusion doesn't define tamponade. Rather, there are several echo features such as right atrial systolic collapse or right ventricular diastolic collapse which make the diagnosis much more likely.
It's also important to remember that because tamponade occurs along this continuum of hemodynamic effects, there's early progressing to late effects, that the findings on echo themselves may actually be too sensitive or they may overcall the diagnosis in tamponade in those patients with only subtle evidence of hemodynamic compromise. And so, that is really where the clinical exam fits in. It helps us interpret the findings of echocardiography in many cases when we go back to the bedside to figure out if the patient really does have tamponade.
>> Is there anything else you would like to tell our listeners about diagnosing this condition? >> So, there are several features that I mentioned that appear to be relatively sensitive for the diagnosis of tamponade, but in general, there's a lack of evidence which guides us as to the true diagnostic accuracy of most of the features we would think of eliciting during a clinical examination for tamponade. So, when we interpret these tests, we should do so with a grain of salt and remember that most of the studies enrolled patients with a previously established pericardial effusion.
So, this is a relatively unusual patient cohort. So, as a take-home message, when faced with a patient with a known effusion, now the clinical then may help us guide decisions about the next test if there is one. However, if diagnostic certainty is really required for the presence of tamponade, additional testing must be done regardless of what the clinical examination shows. >> Thank you, Dr. Choudhry, for your insights into diagnosing cardiac tamponade. And for additional information, JAMAevidence subscribers can consult the online chapter on this topic in the Rational Clinical Examination.
This has been Joan Stephenson of JAMA talking with Dr. Niteesh Choudhry about cardiac tamponade for JAMAevidence.
