Cardiac tamponade occurs when fluid accumulation within the pericardial space compresses the heart and impedes diastolic filling. When fluid accumulates rapidly, tamponade may occur at relatively low pericardial volumes. Subacute or chronic processes, such as neoplastic disease may be associated with much larger effusions. Fluid in the pericardial cavity leads to compromised ventricular filling and decreases cardiac output. The rate of fluid accumulation is very important than the volume of the effusion. This restricts venous return to the heart and lowers right and left ventricular filling. The net result of fluid accumulation is decreased preload, SV, and cardiac output from the heart. Lung examination reveals typically clear lungs to auscultation due to decreased ventricular filling rather than fluid overload.
Risk factors for cardiac tamponade
- Pericarditis,
- Malignancy,
- SLE,
- Uremia
- Tuberculosis, and
- Penetrating Trauma (commonly stab wounds medial to the left nipple).
Clinical Features
- Presents with fatigability, shortness of breath, chest pain, tachycardia, and tachypnea which can rapidly progress to cardiogenic shock.
- Physical Examination of a patient with acute tamponade may reveal
- Beck’s triad (hypotension, distant or muffled heart sounds, and Jugular venous distension)
- a narrow pulse pressure
- Pulsus paradoxus.
- Lung fields are typically clear on examination. Remember, in Dilated Cardiomyopathy bibasilar crackles will be heard with fluid overload features on CXR. S3 will be heard in DCM
- Physical Examination of a patient with acute tamponade may reveal
Mechanism of Pulsus paradoxus in Cardiac Tamponade
Inspiration worsens this condition by lowering the intrathoracic pressure and increasing venous return to the right ventricle. Under normal conditions, the right ventricle is able to accommodate this increased venous return by expanding the right ventricular free wall. Cardiac tamponade usually decreases right ventricular compliance and it causes the interventricular septum to shift toward the left ventricular cavity which further reduces left ventricular filling. This mechanism is also responsible for pulsus paradoxus (>10 mm Hg drop in systolic pressure during inspiration) in patients with cardiac tamponade.
Diagnosis of Cardiac Tamponade
- Echocardiography :
- Most diagnostic. It is used for the diagnosis of tamponade.
- Findings include right atrial and right ventricular diastolic collapse and swinging of heart within the fluid.
- Chest Xray
- It shows a globular, water-bottle-shaped heart
- EKG
- Electrical alternans is diagnostic of a large pericardial effusion. In EKG, there is a beat to beat variation in height of QRS amplitude and axis.
- Right Heart Catheterization
- Rarely necessary. It shows equilibration of pressures in all 4 chambers of heart during diastole
Treatment of Cardiac Tamponade
- It is a life-threatening condition and once the diagnosis is established
- Aggressive volume expansion with intravenous fluids.
- Urgent percutaneous pericardiocentesis (aspirate will be non-clotting blood) should be done
- Surgical drainage should be done, when percutaneous pericardiocentesis can’t be performed safely.
- A pericardial window is required to prevent recurrent pericardial effusion.
References
1. Braunwald E. Harrison’s Principles of Internal Medicine. 17th ed. New York: McGraw Hill; 2008:1489