Cardiac Tamponade Flashcards
What is Cardiac tamponade?
Cardiac tamponade is defined as a haemo-dynamically significant cardiac compression caused by pericardial fluid.
The fluid may be blood, pus, effusion (transudate or exudate) or air.
What is the Normal Anatomy of the pericardium? What is the normal volume of fluid that the pericardium occupies?
The pericardium consists of a thin serous membrane covering the epicardial surface (visceral pericardium) and a serous membrane-lined fibrous sac (parietal pericardium).
They are fibrous structures with limited elastic properties. The pericardial space separates the two layers and contains approximately 20 mL of fluid.
How does a cardiac tamponade occur? What volume of fluid is required to produce the effects of tamponade? Where does compression start and why?
- An acute accumulation of pericardial fluid of greater than 100 mL will produce haemodynamic effects of tamponade
- whereas a chronic pericardial collection of fluid up to 2000 mL may occur without imposing any effect upon cardiac output
- Compression start on the right heart (walls are thinner)
What are the causes of cardiac tamponade? What are the 3 most common causes?
- Trauma
Penetrating and blunt chest trauma
Iatrogenic (Cardiac catheterisation, pacemaker insertion, central venous cannulation, Post operative thoracotomy, Pericardiocentesis) - Myocardial infarction (can cause a ventricular wall rupture leading to bleeding)
- Anticoagulation/thrombolytic therapy,
- Dissecting aortic aneurysm
- Neoplastic (Lung or breast cancer, lymphoma)
- Connective tissue diseases (Systemic lupus erythematosus, rheumatoid arthritis, Rheumatic fever
- Uraemia
- Radiation therapy
- Idiopathic
- Infectious
- Bacterial
- Mycobacterial
- Viral (coxsackie B, influenza, Infectious mononucleosis)
- fungal
3 most common are:
- TB
- Malignancy
- uremic pericarditis
What is the classical clinical presentation of a cardiac tamponade? What is Becks triad? Most patients suffering a CT would have Becks Triad T/F
- elevated venous pressure
- decreased systemic arterial pressure
- and a quiet heart (i.e. Beck’s triad).
Becks triad consists of:
1. muffled heart sound
2. hypotension
3. distended neck vein
FALSE: the triad is often absent as most may not have a quiet heart and the blood pressure may often be well maintained.
What are the clinical features can be seen in cardiac tamponade? What can be used to suspect cardiac tamponade in a patient?
- Dyspnea, Fatigue and light-headedness.
- Tachypnoea and tachycardia
- Hypotension and shock (i.e. pale, cool clammy extremities and poor peripheral perfusion)
- Distant heart sounds
- Pulsus paradoxus: Exaggerated fall in systolic blood pressure >10 mmHg during quiet inspiration.
It occurs due to a reduction in left ventricular stroke volume caused by interventricular interdependence leading to decrease in LV preload and stroke volume - The central venous pressure is characteristically elevated (JVP wave showed prominent X descent) but kussmaul sign is negative
- The lungs are usually clear
NB: Suspect cardiac tamponade clinically in a patient with dyspnoea, a clear chest, elevated jugular venous pressure, tachycardia and paradoxical arterial pulse and hypotension.
Investigations Cardiac Tamponade ( and the no.1 choice)
ECHO (no 1.)
ECG
Chest x-ray
Right heart catheterisation
What can be revealed with Echocardiography?
This is the most reliable and convenient way of diagnosing pericardial fluid and the haemodynamic effects of the effusion.
It shows large pericardial effusion with right atrial and right ventricular diastolic collapse. In patients without heart disease, the ejection fraction is normal or increased.
What can be revealed with ECG?
This may reveal sinus tachycardia, low-voltage complexes and non-specific ST segment and T wave changes or ST segment elevation due to pericarditis.
Electrical alternans is characteristically seen with a large effusion. Electrical alternans is seen as different heights of QRS complex between beats and its due to a pendular swinging motion of the heart within a pericardial effusion.
ECG is also useful to rule out other causes of hypotension such as arrhythmias and myocardial infarction
What can be revealed with a chest X-ray?
The chest X-ray may be within normal limits. However, features suggestive of large pericardial effusion/tamponade include an enlarged globular cardiac shadow with loss of the hilar waist and normal pulmonary vascular pattern
What can be revealed with Right heart catheterisation? What are we expected to see?
- It allows direct assessment of the arterial pressure within the heart chambers. It shows a prominent ‘x’ descent but absent ‘y’ descent.
- Normally, the Y descent (representing right atrial emptying into the right ventricle) is prominent.
- In tamponade, the Y descent is blunted or absent due to restricted right ventricular filling.
There is also equalisation of diastolic
pressures (to within 3 - 4 mmHg) in the right atrium, right ventricle, pulmonary artery and left atrium (due to pericardial fluid compressing the heart)
Pathophysiology of cardiac tamponade?
- Due to fluid accumulation, the heart cannot stretch out or relax fully between contractions
- meaning cardiac chambers cannot fill with blood properly
- this decreases cardiac output due to a lower amount of blood being squeezed out between each heartbeat
- leading to hypotension
- less blood leaving the heart means less blood reaching the organs and tissues, the heart tries to compensate for its low output by beating faster (tachycardia)
What is the definitive treatment of cardiac tamponade? And when is pericardiocentesis used?
The definitive treatment of cardiac tamponade is the removal of the pericardial fluid by either pericardiocentesis or thoracotomy.
Pericardiocentesis is usually performed for urgent management of an acute tamponade (the acute removal of as little as 50 mL of fluid is often sufficient to correct the acute hypotension).
When is a thoracotomy required/ indicated?
A thoracotomy is often required when continuous blood loss occurs and the source of the bleeding requires surgical correction or where a pericardial clot is likely, which cannot be easily aspirated.
Examples include tamponade following coronary artery bypass grafting, cardiac rupture, penetrating or closed cardiac trauma and aortic dissection.
It is also indicated when pericardiocentesis has failed to relieve the tamponade.
How to do you treat a cardiac tamponade (considering it’s an emergency)? Why shouldn’t you give diuretics?
Cardiac tamponade is an emergency.
1. The patient is initially resuscitated with intravenous fluids to promote maximum filling of the heart.
- Inotropic agents (medication that alters the force of muscular contractions) such as isoprenaline and dobutamine that increase the stroke volume and support systemic resistance are also used in order to maintain perfusion to vital organs
Do not give diuretics as it decreases intracardiac filling pressure and markedly worsened collapse of the right side of the heart
