Cardiac tamponade: 12 pearls in diagnosis and management
ABSTRACTCardiac tamponade shares symptoms and signs such as dyspnea, edema, and low urine output with other, more-common diseases. Consider it when there is chest trauma or when the patient has a chronic medical illness that can involve the pericardium. Successfully treating it can be rewarding for both the patient and the physician.
KEY POINTS
- Slow accumulation of pericardial fluid can result in edema, whereas rapid accumulation leads to hypotension.
- Diuretics can worsen tamponade by removing enough volume from the circulation to lower the central venous pressure below the intrapericardial pressure.
- Try to determine why cardiac tamponade has occurred. Cardiac or aortic rupture requires surgery. If the gross appearance of the pericardial fluid does not match the presumed etiology, reconsider your diagnosis.
- Always review imaging studies before making the diagnosis of cardiac tamponade.
- When cardiac tamponade is considered, pulsus paradoxus must be measured, and if present, integrated with other physical findings and the echocardiogram. However, pulsus paradoxus can be present in the absence of cardiac tamponade, and vice versa.
- Consider the size and location of the pericardial effusion and the patient’s hemodynamic status when deciding between surgery and needle aspiration.
PEARL 8: PULSUS PARADOXUS WITHOUT CARDIAC TAMPONADE
Pulsus paradoxus can be present in the absence of cardiac tamponade. Once pulsus paradoxus of more than 10 mm Hg is measured, one must be sure the patient does not have a condition that can cause pulsus paradoxus without cardiac tamponade. Most of these are pulmonary conditions that necessitate an exaggerated inspiratory effort that can lower intrathoracic pressure sufficiently to oppose pulmonary venous return and cause a fall in systemic blood pressure:
- Chronic bronchitis
- Emphysema
- Mucus plug
- Pneumothorax
- Pulmonary embolism
- Stridor.
In these, there may be pulsus paradoxus, but not due to cardiac tamponade.
PEARL 9: CARDIAC TAMPONADE CAN BE PRESENT WITHOUT PULSUS PARADOXUS
Cardiac tamponade can be present without pulsus paradoxus. This occurs when certain conditions prevent inspiratory underfilling of the left ventricle relative to the filling of the right ventricle.8
How does this work? In cardiac tamponade, factors that drive the exaggerated fall in arterial pressure with inspiration (pulsus paradoxus) are the augmented right ventricular filling and the decreased left ventricular filling, both due to the lowering of the intrathoracic pressure. As the vena caval emptying is augmented, the right ventricular filling is increased, the ventricular septum shifts to the left, and pulmonary venous return to the heart is decreased.
Factors that can oppose pulsus paradoxus:
- Positive pressure ventilation prevents pulsus paradoxus by preventing the fall in intrathoracic pressure.
- Severe aortic regurgitation does not permit underfilling of the left ventricle during inspiration.
- An atrial septal defect will always equalize the right and left atrial pressures, preventing differential right ventricular and left ventricular filling with inspiration.
- Severe left ventricular hypertrophy does not permit the inspiratory shift of the ventricular septum from right to left that would otherwise lead to decreased left ventricular filling.
- Severe left ventricular dysfunction, with its low stroke volume and severe elevation of left ventricular end-diastolic pressure, never permits underfilling of the left ventricle, despite cardiac tamponade and an inspiratory decrease in intrathoracic pressure.
- Intravascular volume depletion due to hemorrhage, hemodialysis, or mistaken use of diuretics to treat edema can cause marked hypotension, making pulsus paradoxus impossible to detect.
Knowledge of underlying medical conditions, the likelihood of their causing cardiac tamponade, and the appearance of the echocardiogram prompt the physician to look further when the presence or absence of pulsus paradoxus does not fit with the working diagnosis.
The echocardiogram can give hints to the etiology of a pericardial effusion, such as clotted blood after trauma or a cardiac-perforating procedure, tumor studding of the epicardium,9 or fibrin strands indicating chronicity or an inflammatory process.10 Diastolic collapse of the right ventricle, more than collapse of the right atrium or left atrium, speaks for the severity of cardiac tamponade. With hemodynamically significant pericardial effusion and cardiac tamponade, the inferior vena cava is distended and does not decrease in size with inspiration unless there is severe intravascular volume depletion, at which time the inferior vena cava is underfilled throughout the respiratory cycle.
