Cardiac tamponade
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Cardiac tamponade is a medical emergency condition where a large amount of a liquid accumulates in the pericardium in a relatively short time. The created pressure prevents proper filling of heart cavities. Instead of reducing the filling of both ventricles equally, the septum of the heart will bend into either the left or right ventricle. The end result is low stroke volume and shock.
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Causes
Cardiac tamponade can happen acutely, such as from a stab wound, from surgery, or from the heart muscle rupturing. Heart rupture will usually happen (though it is very uncommon) around the site of myocardial infarction. Chronic cardiac tamponade is a slower process, where up to two litres of fluid can enter the pericardial space over a period of time, the pericardium stretching to accommodate.
Diagnosis
The signs and symptoms can appear very similar to congestive heart failure. There usually is a history of sudden onset attributable to trauma, particularly in younger patients.
In cases of cardiac tamponade, the heart sounds may sound muffled on auscultation as the accumulated fluid dampen the normal heart sounds transmitted through the chest wall.
First Aid
If recognized, call for help and arrange for immediate transport to advanced medical care. MEDEVAC in wilderness first aid situations is indicated. If the patient's heart stops, apply CPR as you would normally, although it is unlikely to be effective.
Field care (for EMTs)
In the field, some paramedics have protocols which permit them to use a hollow needle to penetrate the pericardial sac through the chest wall and relieve the pressure. This is an extremely dangerous procedure which may be the only hope of saving life, particularly if evacuation is delayed. Effective treatment of cardiac tamponade requires advanced medical care.
Clinical treatment
Pericardiocentesis (needle evacuation of the fluid and lowering of the pressure), and then treatment of the underlying cause, is life-saving. Often, a pericardial drain is left in situ to prevent short-term recurrence. Surgery to repair the damage to the heart is often required.