Pericardial effusion is the collection of fluid in the pericardial space around the heart. When the pressure in the pericardial space exceeds the pressure in the cardiac chambers, then cardiac function is impaired and the resultant hemodynamic crisis is known as cardiac tamponade. Echocardiography is critical in the evaluation of pericardial effusion and instrumental in determining the presence of cardiac tamponade. Echo-guided or echo-assisted pericardiocentesis is the treatment in most cases.1
The pericardium consists of two layers: the visceral pericardium, which follows the epicardial surface of the heart, and the parietal pericardium, which lies against the pleural surfaces laterally and the diaphragm inferiorly. The pericardial space normally contains about 15 cc of fluid. There are numerous etiologies for pericardial effusion, including infections (2%), malignancy (45%), inflammation, trauma, tuberculosis (14%), postoperative (15%), coronary intervention-related (4%), ischemic heart disease-related (4%), idiopathic (or unknown) (6%), and more.2
Pericardial tamponade occurs when the pressure of pericardial fluid accumulating in the pericardial space exceeds that in the heart chambers. The low pressure atria are affected first. Tamponade results in impaired filling and reduced stroke volume and cardiac output, which leads to tachycardia, hypotension, and jugular venous distention. The amount of fluid matters less than the speed at which this accumulation occurs. In fact, loculated effusions following surgical interventions are just as likely to cause tamponade.
In 1983, percutaneous pericardiocentesis guided by two-dimensional echocardiography was introduced. It has become a safe and effective method of removing the pericardial effusion, eliminating cardiac tamponade, and providing relief for the patient and medical staff. The pericardium covers the entire external surface of the heart, so it can potentially be imaged in every view. The sonographer identifies the optimal point of needle entry which avoids contact with the heart and vital structures. The ideal entry site is the point where the distance from the skin to maximal effusion collection is the shortest. The subxiphoid or subcostal approach was used in over 91% of the cases in a study by Cho et al.3
There are no outward signs to show at what pressure tamponade results. A patient may present to the emergency room in extreme respiratory distress with low blood pressure and distended neck veins. The patient continues to move in an effort to gain an ounce of breath. Their skin appears pale or grey, and they look terrified. The cath lab monitors would show that the intrapericardial pressure has increased to or exceeded right atrial and ventricular diastolic filling pressures. It might increase to left atrial or ventricular diastolic filling pressure. Classic tamponade might demonstrate intrapericardial pressure of ≥ 7 mmHg.
Many facilities use echocardiography for guidance in the cath lab, where hemodynamics can be monitored, and needle position and advancement can be further guided by fluoroscopy. The needle is advanced into the pericardial space. This can be seen on echo, but injection of saline through the needle can be readily detected by ultrasound and confirm correct location. The pericardial fluid is drained by insertion of a pigtail catheter into the pericardial space and connection of the catheter to a collection bottle. When the fluid volume decreases, the reduced pressure slows the fluid removal. The fluid can then be pulled out with a large syringe and a stopcock to pull the fluid into the syringe and push the fluid out into the container. The pericardial effusion is termed small if less than 100 cc, moderate if between 100-500 cc and large if greater than 500 cc of fluid. Echo assistance is used until no further fluid can be removed. A drain is typically left in place overnight and removed the next day after a follow-up echo evaluation is performed. If the effusion returns, the physician may consider a surgical procedure called a pericardial window, which cuts a small square in the pericardium to prevent the possibility of future collection of fluid and then pressure buildup within the pericardium.
With the removal of the pericardial fluid, the intrapericardial pressure decreases, allowing the heart to fill once again. The systolic blood pressure is back to a normal 120 mmHg. The patient appears calm and smiling, grateful to be able to take deep and easy breaths. Their skin color is pink. The right atrial pressures are normally 3 to 5 mmHg and the intrapericardial pressures have decreased below that level on monitoring.
A trained sonographer can easily identify pericardial effusion. An experienced cardiologist can then determine the clinical diagnosis of cardiac tamponade. The advanced hemodynamic monitoring provided in the cath lab can assist throughout the procedure. Echocardiography and echo-guided or assisted percutaneous pericardiocentesis has been safely performed (0.7% complication rate) with a procedural success rate of 99% for over twenty years and remains the treatment of choice for cardiac tamponade.
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