A. PATHOPHYSIOLOGY
Cardiac tamponade can be produced by the accumulation of fluid, pus, blood, gas, or tissue. Causes of cardiac tamponade are the same as pericardial effusion
, but in different series of cases, an estimated frequency of causes that can develop cardiac tamponade has been described, including
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Different types of cardiac tamponade can be seen depending on the clinical scenario and the onset:
- Acute cardiac tamponade (minutes): secondary to trauma, cardiac rupture, or after an invasive diagnostic or therapeutic procedure.
- Subacute cardiac tamponade (days to weeks): in the context of neoplastic, uremic, or idiopathic pericarditis.
- Low pressure (occult) cardiac tamponade occurs in severely hypovolemic patients.
- Regional cardiac tamponade: due to the presence of loculated, eccentric effusion or localized hematoma. Only selected chambers are compressed.
Size or composition does not matter:
- The rate of fluid accumulation is more significant in cardiac tamponade.
- Acute setting: pericardium is stiffer and non-compliant. A little amount of pericardial fluid (100–200 cc) can be devastating.
- Subacute setting: pericardium can stretch and become more compliant. A slow or gradual accumulation of up to 1000-1500 cc can be tolerated without hemodynamic impairment.
- TIPS
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- When the pericardium has maximally distended, small increments in intrapericardial volume will trigger acute cardiac tamponade.
- The thickened pericardium can have a much lower threshold for pressure increases.
B. CLINICAL ASSESSMENT
Prompt diagnosis is essential to reduce the mortality risk of these patients.
- Beck´s triad refers to increased central venous pressure, hypotension, and muffled heart sounds.
- Clinical signs and symptoms can vary depending on the acuteness and underlying cause of the tamponade, being the most common dyspnoea, tachycardia, and elevated jugular venous pressure.
- Other frequent findings are hepatomegaly, pulsus paradoxus, pericardial rub, and diminished heart sounds. In severe cases, signs of cardiogenic shock may appear.
C. BEDSIDE FINDINGS: CARDIOLOGIST BE AWARE
Patients suspected of having cardiac tamponade should be evaluated initially with an electrocardiogram, chest radiograph, and echocardiography.
- Electrocardiogram (ECG) typically shows sinus tachycardia and may show diffuse low voltage and occasionally electrical alternans
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- It has been suggested that low QRS voltage in patients with pericardial effusion is a specific manifestation of cardiac tamponade.
- Echocardiography: although cardiac tamponade is a clinical diagnosis, an echocardiogram (two-dimensional and Doppler) should always be performed without delay to confirm the suspicion. It usually shows
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- Pericardial effusion.
- Cardiac chamber compression with the early diastolic collapse of the right atrial (RA) or right ventricular (RV) free wall (typically occurs before clinical hemodynamic failure). Left chamber collapse is less commonly seen (25%) due to the muscular wall of the LV.
- Inferior vena cava (IVC) plethora: dilatation and reduction (50%) in the diameter of the IVC during inspiration, reflecting a marked elevation in central venous pressure.
- Doppler flow-velocity paradoxus, compression of the thoracic IVC and pulmonary trunk.
- The paradoxical motion of the interventricular septum and swinging motion of the heart in the pericardial sac.
- Respiratory variation in volumes and flows (variation of mitral and tricuspid flow velocities).
D. IMAGING FEATURES FROM X-RAY TO MRI
- CHEST X-RAY: ALWAYS COMPARE (GO WAY BACK)
- The enlarged cardiac silhouette is the more frequent finding (always important to compare with prior radiographs)
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. A bottle-shaped heart may appear
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- Cardiomegaly is an infrequent finding in acute cardiac tamponade (more than 200 mL is needed to manifest on the x-ray).
- TIPS: findings on a chest radiograph are neither sensitive nor specific.
- Tension pneumopericardium: small heart sign.
- CHEST CT FINDING
Echocardiography remains the first diagnosis approach for the evaluation of pericardial disease, especially pericardial effusion, or when clinical findings are equivocal of cardiac tamponade. Nevertheless, chest CT has a lot of unknown advantages over echocardiography. It provides the ability to assess the entire chest. Chest CT allows to rule out other abnormalities in the mediastinum or lungs. Further, CT can be extremely helpful in defining the nature of the pericardial effusion. Attenuation values greater than those of the water (0-20 HU) can be seen in malignancy, hemopericardium, or purulent exudates
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. The presence of pericardial thickening or nodular lesions arising from or adjacent to the pericardium suggests malignant pericardial disease in the right context. The pericardium can also show contrast enhancement if an inflammatory process is present (pericarditis)
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CT is less operator and patient dependent than other imaging techniques, particularly in those with difficulties in holding their breath. Multidetector CT scanners also offer the ability to obtain ECG-gated images, allowing functional and dynamic evaluation of the heart
. Another advantage is the ability to assess pericardial thickening and calcification (location and extent).
As said, CT can be extremely helpful in discarding conditions that may simulate pericardial effusion (ie, pleural effusions, lower lobe atelectasis, pericardial and intracardiac masses, or other mediastinal lesions), and more importantly defining, the nature of the pericardial effusion
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Normal pericardium thickness on CT scans and MR images is 2 mm (abnormal >3-4mm)
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Thickness and volume correlation of the pericardial effusion
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- <10 mm: small (< 250 cc)
- 10-20 mm: moderate (250-500 cc) (more risk to evolve to cardiac tamponade)
- >20 mm: large (> 500 cc)
CT CHEST FINDINGS:
- Pericardial thickening or nodular lesions arising from or adjacent to the pericardium suggests malignant pericardial disease
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- CT findings in cardiac tamponade include
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- Enlargement of the superior vena cava or IVC
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- Reflux of contrast to the IVC or azygos vein
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- Enlargement of hepatic and renal veins
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- Periportal oedema
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- Liver with “nutmeg” morphology
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- Cardiac findings:
- “Flattened sign” (flattening of the anterior surface and decreased anteroposterior diameter of the heart) secondary to the presence of fluid, air, or tissue
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- Compression of the coronary sinus, pulmonary trunk, or the intrathoracic segment of IVC
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- Compression of right cardiac chambers
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- Bowing of the interventricular septum, not specific for tamponade, can also be reported in other conditions including constrictive pericardial disease and massive pulmonary embolism
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- Doble cardiac contours reassembling tachycardia
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3. MRI ALMOST IDEAL BUT NOT FAST ENOUGH
Although magnetic resonance imaging (MRI) allows the detection of pericardial effusion with high sensitivity (demonstrating as small as 30 cc fluid quantities), it has a limited role in the prompt diagnosis of cardiac tamponade.
MRI findings
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- Swinging heart
- Paradoxical septal bounce
- Characterization of the nature of the pericardial effusion
- Effects on cardiac function and diastolic filling
ONCE IDENTIFIED, PROMT TREATMENT: PERICARDIOCENTESIS
A diagnostic algorithm for the evaluation of patients with suspected cardiac tamponade is suggested
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Emergency pericardiocentesis, preferably by using needle pericardiocentesis with echocardiographic guidance is the treatment of choice
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. Patients with recurrent tamponade may require pericardial sclerosis or a balloon pericardiotomy.