Cardiac emergency: top tips for pericardial effusions

When presenting acutely, timely diagnosis and treatment of pericardial effusions can make the difference between life and death. Even chronic pericardial effusions will reach a tipping point, although these tend to be less dramatic on presentation. In this article we will cover the clear signs of a pericardial effusion, underlying causes and the most effective approach to maintain a calm head in the emergency scenario.

If at any stage you aren’t sure, we are here if you need advice or swift referral.

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A quick physiology refresher

The pericardium is a fibrous sac encompassing the heart, normally containing a very small amount of fluid for lubrication. Fluid can build up in the pericardial space due to:

• Drainage being impaired (e.g. due to a mass or significant distortion of cardiac shape)
• Additional fluid such as haemorrhage (due to bleeding mass or atrial tear or coagulopathy), purulent/inflammatory material (due to trauma, infection, migrating foreign body) or less commonly chyle (damage or disruption to lymphatic drainage)
• No apparent reason! Idiopathic pericardial effusion is a diagnosis of exclusion

The pressure in the right heart is low (about ¼ of that in the pressure in the left ventricle), so once the pressure in the pericardial space increases above this, the right ventricle will start to collapse, resulting in cardiac tamponade. This impairs filling, reduces output and leads to signs of right-sided failure such as:

• Abdominal distension due to fluid accumulation (ascites)
• Jugular distension
• Tachycardia and weak femoral pulses or pulsus paradoxus (pulses which vary with respiration) due to subsequent reduced left heart filling

Patients with acute effusions often show sudden weakness, breathlessness, or collapse, whereas chronic effusion may cause exercise intolerance, mild lethargy, or progressive ascites. Some may cough, vomit, or retch.

Clinical findings

Patients may have some (or all) of the following:

• Pale gums with slow capillary refill time (CRT)
• Tachycardia
• Tachypnoea (sometimes with increased effort)
• Muffled heart sounds (may be less obvious in lean/narrow chested dogs)
• Abdominal distension with fluid thrill
• Jugular distension and pulsation, positive hepatojugular reflux (with both hands, apply pressure to the cranial abdomen of the standing patient (10-15 seconds) whilst observing the jugular veins, which will distend (and can remain distended) in a positive response
• Weak or variable femoral pulses

Patients with all of these signs almost certainly have a pericardial effusion unless proven otherwise, but confirmation is always needed with imaging. Standing or sternal thoracic focussed assessment (TFAST) is often enough to visualise the heart and surrounding structures. Some patients also have a pleural effusion, so it is useful to learn to differentiate between the two. Masses can be easier to spot when there is pericardial effusion present, but don’t spend too much time searching for them – it is more important to stabilise your patient. Try to have a subjective view on whether or not there are obvious structural cardiac changes (such as marked chamber enlargement) but remember that systolic function is likely to look terrible in a heart which is being squeezed!

If you’re unsure, save any images or videos and we’ll be happy to review them and advise on next steps. You can also find information on our echo courses, if you’d like to sharpen your scanning skills.

Pericardial effusion confirmed – what next?

Don’t:

• Leave unstable patients overnight.
  • If tamponade is present, draining the pericardial space allows right heart filling to resume and often results in dramatic clinical improvement. Delaying treatment risks deterioration or death.
• Reach for diuretics.
  • Despite signs mimicking right-sided congestive heart failure, diuretics reduce circulating volume and worsen tamponade. Unless there’s clear evidence of structural cardiac disease, avoid them. Instead, consider a bolus of IV fluids to improve preload while preparing for drainage or referral.
• Panic!
  • Your goal isn’t to make a perfect diagnosis in an emergency. Even partial drainage or just entering the pericardial space (“popping” it) can stabilise the patient and buy time as some or all of the fluid will leak out into the chest cavity where it will be absorbed. Focus on relieving tamponade and keeping the patient stable.
• Assume it’s neoplastic.
  • Neoplasia is a common differential, but so are idiopathic effusions – and these have a much better prognosis! 

Do:

• Record an ECG during pericardiocentesis.
  • Ventricular premature complexes (VPCs) may indicate your needle is touching the myocardium — adjust positioning as needed.
• Check for clotting.
  • If what you are draining begins to clot, you may be draining from the heart itself rather than the pericardial space. Stop and reassess.
• Keep the first sample for analysis.
  • Submit for cytology and assess protein/specific gravity in-house if possible. You may not get a definitive answer, but it can help categorise the effusion and rule out rarer causes.
• Aim for follow-up imaging.
  • Referral for echocardiographic assessment by an experienced cardiologist +/- CT is ideal to evaluate for masses. Bear in mind that smaller lesions can still be difficult to definitively diagnose, so manage owner expectations on definitive answers.

Recurrent effusions

Even idiopathic effusions can recur, so it is important to manage owner expectations. Repeated drainage can cause stiffening of the percardium, increasing the risk of tamponade with smaller volumes. Referral for surgical pericardiectomy is an option to consider after two episodes.

Need Advice?

If you’ve diagnosed or suspect pericardial effusion, we’re happy to help. Whether it’s urgent referral, reviewing your imaging, or planning longer-term management, feel free to get in touch.

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