Review Question - QID 217743

This patient who presents with distant (muffled) heart sounds following a stab wound most likely has cardiac tamponade. A decrease in systolic blood pressure of 10 mmHg or greater with inspiration, also known as pulsus paradoxus, is a finding associated with cardiac tamponade.

Cardiac tamponade is an accumulation of fluid in the pericardial sac that restricts ventricular filling. Risk factors for tamponade include pericarditis, malignancy, uremia, tuberculosis, and penetrating trauma (e.g., stab wounds). Cardiac tamponade occurs when increased pericardial pressure from accumulated fluid (e.g., blood) causes compression of the cardiac chambers, leading to decreased blood pressure and decreased cardiac output. Beck triad is a constellation of findings seen in cardiac tamponade and includes muffled heart sounds (due to the presence of pericardial fluid between the heart and pericardium), jugular venous distension (due to the inability of the right atrium to accommodate venous return), and hypotension. Pulsus paradoxus is another finding in cardiac tamponade and refers to a decrease in systolic blood pressure greater than 10 mmHg during inspiration. This occurs due to interventricular dependence in cardiac tamponade. Normally, during inspiration, there is no change or a slight decrease in systolic blood pressure as the right ventricle can accommodate the increased blood volume and pushes slightly on the left ventricle or into the pericardial space. This effect is exaggerated in cardiac tamponade, as the filled pericardial sac also inhibits right ventricular filling, leading to even more pushing of the interventricular septum towards the left ventricle and decreased left ventricular filling. Other conditions associated with pulsus paradoxus include constrictive pericarditis and obstructive lung disease.

Van Dam and Fitzgerald discuss pulsus paradoxus and note several non-cardiac diseases such as asthma, pneumothorax, large pleural effusion, and pulmonary embolism can also lead to pulsus paradoxus.

Incorrect Answers:
Answer 2: Disappearance of JVP with inspiration does not occur in cardiac tamponade. Kussmaul sign, or an increase in JVP with inspiration, may occur in cardiac tamponade. Normally, the JVP should decrease with inspiration due to increased venous return to the heart. However, in cardiac tamponade, the JVP may increase with inspiration as the right ventricle is unable to accommodate increased blood volume due to the surrounding fluid-filled pericardium.

Answer 3: A high-pitched heart sound in early diastole describes a pericardial knock. Pericardial knocks may be evident in constrictive pericarditis, which is a chronic condition that leads to the scarring of the pericardium. The sudden cessation of ventricular filling during diastole causes a pericardial knock. Constrictive pericarditis would present with fatigue, dyspnea, and symptoms of right-sided heart failure. Signs and symptoms of right-sided heart failure include elevated JVP, lower extremity edema, ascites, and positive hepatojugular reflux (distension of neck veins when pressure is applied over the liver).

Answer 4: An increase in systolic blood pressure of 15 mmHg with inspiration does not occur in cardiac tamponade. Rather, a decrease in systolic blood pressure (pulsus paradoxus) occurs.

Answer 5: Prominent y descent in the JVP waveform occurs in constrictive pericarditis. The y descent occurs due to the right atrium emptying into the right ventricle. This waveform is absent in cardiac tamponade due to impaired early diastolic flow into the right ventricle due to compression from surrounding pericardial fluid. In contrast, this waveform is prominent in constrictive pericarditis because the right ventricle is adherent to the pericardium, creating a "vacuum-like" effect during diastole and leading to exaggerated ventricular filling during early diastole.

Bullet Summary:
Pulsus paradoxus, defined as a decrease in systolic blood pressure greater than 10 mmHg with inspiration, can be seen in cardiac tamponade.