Investigations
1st investigations to order
ECG
Test
An essential test in the evaluation of any patient with symptoms of tamponade.
A rhythm strip should also be collected to look for beat-to-beat electrical alternans, which is a more specific ECG sign of tamponade.[5][15]
Electrical alternans is rarely seen in the absence of tamponade.
Low QRS voltage is indicative of cardiac tamponade, but its absence does not exclude tamponade.[45]
Result
low voltage, electrical alternans; electromechanical dissociation associated with end stage tamponade
transthoracic echocardiogram
Test
First-line investigation in cases of suspected cardiac tamponade as it provides rapid, readily available haemodynamic data to detect tamponade physiology.[4][15]
Result
pericardial effusion; chamber collapse and respiratory variation of ventricular filling; variation in transmitral flow >30% and/or in transtricuspid flow >60% on Doppler recording; inversion of the free wall of the right atrium for >⅓ of systole; dilated inferior vena cava and hepatic veins; reduced left ventricle (LV) size and appearance of LV hypertrophy; septal shift or ‘bounce’ with inspiration
CXR
Test
Neither sensitive nor specific. The pericardium can hold over 200 cm^3 of fluid before an enlarged silhouette is noted.[5]
Result
enlarged cardiac silhouette
FBC
Test
Baseline test; might indicate inflammatory pericarditis or anaemia in chronic renal failure.
Result
raised WBC count and differentials; low Hb
erythrocyte sedimentation rate/CRP
Test
Non-specific; may indicate an inflammatory process.
Result
may be elevated
cardiac enzymes
Test
Raised in cardiac trauma and myocardial infarction.
Result
may be elevated
Investigations to consider
cardiac CT
Test
May be considered in cases of complicated tamponade: for example, in postoperative or loculated pericardial effusions.[4]
Result
static CT: pericardial effusion, compression of the anterior cardiac surface causing a 'flattened heart', angulation/bowing of the interventricular septum (correlating with inspiratory septal bounce on echocardiography), enlarged superior and inferior vena cava; dynamic CT (similar to echocardiography findings): pericardial effusion, chamber collapse and respiratory variation of ventricular filling, variation in transmitral flow >30% and/or in transtricuspid flow >60% on Doppler recording, inversion of the free wall of the right atrium for >⅓ of systole, dilated inferior vena cava and hepatic veins, reduced LV size and appearance of LV hypertrophy, septal shift or ‘bounce’ with inspiration
cardiac MRI
Test
May be considered in cases of complicated tamponade: for example, in postoperative or loculated pericardial effusions.[4]
Result
static MRI: pericardial effusion, compression of the anterior cardiac surface causing a 'flattened heart', angulation/bowing of the interventricular septum (correlating with inspiratory septal bounce on echocardiography), enlarged superior and inferior vena cava; dynamic MRI (similar to echocardiography findings): pericardial effusion, chamber collapse and respiratory variation of ventricular filling, variation in transmitral flow >30% and/or in transtricuspid flow >60% on Doppler recording, inversion of the free wall of the right atrium for >⅓ of systole, dilated inferior vena cava and hepatic veins, reduced LV size and appearance of LV hypertrophy, septal shift or ‘bounce’ with inspiration
cardiac catheterisation
Test
Direct measurement of the haemodynamic effects of tamponade.
Infrequently performed in patients with pure tamponade.[15]
Useful in differentiating tamponade from constrictive pericarditis or restrictive cardiomyopathy.
Result
equalisation of diastolic pressures; respiratory reciprocal inflow
pericardiocentesis fluid for culture and cytology
Test
Pericardial fluid (collected from pericardiocentesis/surgical drainage) may be sent for culture and cytology to support diagnosing underlying aetiology.
Result
may identify underlying cause in non-traumatic cases
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