What is pulsus paradoxus?

What is Pulsus Paradoxus

Pulsus paradoxus is an exaggerated inspiratory decrease in systolic blood pressure of greater than 10 mmHg during normal breathing, while diastolic pressure remains unchanged. 1, 2

Definition and Clinical Detection

• The phenomenon represents an abnormal exaggeration of the normal physiologic drop in systolic pressure that occurs with inspiration 3, 4
• It can be detected at the bedside by palpating the pulse, which weakens or disappears during inspiration 1, 2
• The term "pulsus paradoxus" was coined by Adolf Kussmaul in 1873, though the finding was first described by Richard Lower in 1669 3

Pathophysiologic Mechanism

• During inspiration, increased venous return to the right heart causes right ventricular expansion within the confined pericardial space 2
• This creates exaggerated ventricular interdependence, where the expanded right ventricle shifts the interventricular septum leftward, reducing left ventricular filling 5, 2
• The decreased left ventricular stroke volume results in a drop in systolic blood pressure during inspiration 2
• The pericardial constraint creates a "fixed total heart volume" where cardiac chambers must compete for space 2

Clinical Measurement Technique

• Using a sphygmomanometer, inflate the blood pressure cuff above systolic pressure 1, 2
• During deflation, note the pressure at which the first Korotkoff sound appears only during expiration 1, 2
• Continue deflation until the first Korotkoff sound is audible throughout the entire respiratory cycle 1, 2
• The difference between these two pressure points defines the magnitude of pulsus paradoxus 1, 2

Associated Clinical Conditions

• Cardiac tamponade is the most clinically significant cause, where pulsus paradoxus results from exaggerated ventricular interdependence 5, 1
• Constrictive pericarditis can produce this finding through similar mechanisms of cardiac constraint 3
• Severe obstructive airway disease (asthma, COPD) causes pulsus paradoxus through extreme respiratory variations in intrathoracic pressure 6, 7, 8
• Other causes include massive pulmonary embolism and tension pneumothorax 6

Important Clinical Caveats

• Pulsus paradoxus may be absent in cardiac tamponade when certain conditions coexist, including atrial septal defect, significant aortic regurgitation, or left ventricular dysfunction 1, 6
• The predictive value of pulsus paradoxus for cardiac tamponade is limited and must be interpreted in clinical context 7
• Positive pressure mechanical ventilation can alter or eliminate the finding 5

Echocardiographic Correlates

• Doppler echocardiography shows exaggerated respiratory variability (>25%) in mitral inflow velocity 2
• Inspiratory decrease and expiratory increase in pulmonary vein diastolic forward flow occurs 2
• Respiratory variation in ventricular chamber size and abnormal ventricular septal motion are visible 2
• These findings confirm the hemodynamic significance of pulsus paradoxus 6

Clinical Significance and Action

• The presence of pulsus paradoxus should prompt immediate echocardiographic evaluation 2
• In unstable patients with suspected cardiac tamponade, urgent pericardiocentesis or cardiac surgery is indicated 1
• Echocardiography serves as the first-line imaging technique to confirm tamponade and guide intervention 1