Pulsus paradoxus

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In medicine, a pulsus paradoxus (PP), also paradoxic pulse and paradoxical pulse, is an exaggeration of the normal variation in the pulse during the inspiratory phase of respiration, in which the pulse becomes weaker as one inhales and stronger as one exhales. It is a sign that is indicative of several conditions including cardiac tamponade and lung diseases (e.g. asthma, COPD).Khasnis A, Lokhandwala Y. Clinical signs in medicine: pulsus paradoxus. J Postgrad Med. 2002 Jan-Mar;48(1):46-9. PMID 12082330. Free Full Text. The paradox in pulsus paradoxus is that, on clinical examination, one can detect extra beats on cardiac auscultation, during inspiration, when compared to the radial pulse. It results from an accentuated decrease of the blood pressure, which leads to the (radial) pulse not being palpable and may be accompanied by an increase in the jugular venous pressure height (Kussmaul sign). As is usual with inspiration, the heart rate is increased, Abstract due to increased venous return. Free Full Text.

Mechanism of reduced blood pressure during inspiration in normal conditions

During inspiration, systolic blood pressure decreases, and pulse rate goes up. This is because the intrathoracic pressure becomes more negative relative to atmospheric pressure. This increases systemic venous return, so more blood flows into the right side of the heart. However, the decrease in intrathoracic pressure also expands the compliant pulmonary vasculature. This increase in pulmonary capacitance pools the blood in the lungs, and decreases pulmonary venous return, so flow is reduced to the left side of the heart. Reduced left-heart filling leads to a reduced stroke volume which manifests as a decrease in systolic blood pressure. Reduced filling also leads to a shorter ejection time, and thus, faster heart rate.

Measurement of PP

PP is quantified using a blood pressure cuff and stethoscope, by measuring the variation of the pressure in systole with respiration. Normal systolic blood pressure variation (with respiration) is considered to be ≤10 mmHg. Pulsus paradoxus is an inspiratory reduction in systolic pressure >10 mmHg. Pulsus paradoxus can also be measured by listening to Korotkoff sounds and hearing the actual sound of the systolic beat. If the pressure gradient is >10mmHg, it can be classified as pulsus paradoxus and shifting of the atrial septum.

Predictive value for tamponade

PP has been shown to be predictive of the severity of cardiac tamponade.Curtiss EI, Reddy PS, Uretsky BF, Cecchetti AA. Pulsus paradoxus: definition and relation to the severity of cardiac tamponade. Am Heart J. 1988 Feb;115(2):391-8. PMID 3341174.

Causes

Pulsus paradoxus can be caused by several physiologic mechanisms. Anatomically, these can be grouped into:
  • cardiac causes,
  • pulmonary causes and
  • non-pulmonary and non-cardiac causes.
    • Considered physiologically, PP is caused by:
  • decreased right heart functional reserve, e.g. myocardial infarction and tamponade,
  • right ventricular inflow or outflow obstruction, e.g. superior vena cava obstruction and pulmonary embolism, and
  • decreased blood to the left heart due to pulmonary vasodilation/hyperinflation, e.g. asthma, COPD and anaphylactic shock.

    • List of causes

    Cardiac:
  • cardiac tamponade
  • pericardial effusion
  • pulmonary embolism
  • cardiogenic shock
    • Pulmonary:
  • tension pneumothorax
  • asthma
    • Non-pulmonary and non-cardiac:
  • anaphylactic shock
  • superior vena cava obstruction


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