Pulsus paradoxus

From Dog

Pulsus paradoxus, defined as systolic pressure fluctuation greater than 10 mmHg during the respiratory cycle, is relatively common heart disease of dogs.

This phenomenon is caused by diseases which cause an abnormally large inspiratory decrease in transmural aortic pressure and beat-to-beat aortic flow[1] due to a reduced output of the left ventricle during inspiration[2] due to cardiogenic or non-cardiogenic (blood volume depletion) causes[3].

In dogs, this is frequently associated with shock, congestive heart failure, cardiac tamponade[4], pericardial effusion, right ventricular diastolic collapse[5] and bronchoconstriction associated with upper airway obstruction (e.g. foreign body, asthma)[6].

Physical examination findings may include muffled heart sounds and jugular venous distention.

During inspiration, pulmonary arterial pressure drops and left atrial and aortic pressure rises[7].

In cases of pericardial effusion, pericardiocentesis is indicated for the emergency treatment of secondary cardiac tamponade. Pericardiectomy may improve survival in some dogs. The prognosis varies greatly, depending on the underlying cause[8].

In severe cases, vagotomy is effective at curing the condition[9].

in cases of shock-induced pulsus paradoxus, positive pressure ventilation has been shown to reverse this condition[10].


  1. Kimura T (1995) Hemodynamics associated with sleep disorders in anesthetized dogs. Nihon Kyobu Shikkan Gakkai Zasshi 33(1):3-9
  2. Fitchett DH & Sniderman AD (1990) Inspiratory reduction in left heart filling as a mechanism of pulsus paradoxus in cardiac tamponade. Can J Cardiol 6(8):348-354
  3. Cohn JN et al (1967) Mechanism of pulsus paradoxus in clinical shock. J Clin Invest 46(11):1744-1755
  4. Cogswell TL et al (1985) Effects of intravascular volume state on the value of pulsus paradoxus and right ventricular diastolic collapse in predicting cardiac tamponade. Circulation 72(5):1076-1080
  5. Klopfenstein HS et al (1985) The relative merits of pulsus paradoxus and right ventricular diastolic collapse in the early detection of cardiac tamponade: an experimental echocardiographic study. Circulation 71(4):829-833
  6. Parsons GH & Green JF (1978) Mechanisms of pulsus paradoxus in upper airway obstruction. J Appl Physiol 45(4):598-603
  7. Strohl KP et al (1987) Cardiovascular performance during bronchospasm in dogs. Respiration 51(1):39-48
  8. Shaw SP & Rush JE (2007) Canine pericardial effusion: diagnosis,treatment, and prognosis. Compend Contin Educ Vet 29(7):405-411
  9. Federici A et al (1984) Aortic pressure and heart rate patterns during the respiratory cycle in different autonomic conditions in conscious dog. Boll Soc Ital Biol Sper 60(6):1119-1125
  10. Robotham JL et al (1983) A re-evaluation of the hemodynamic consequences of intermittent positive pressure ventilation. Crit Care Med 11(10):783-793