THE MECHANISM OF PULSUS PARADOXUS DURING ACUTE PERICARDIAL TAMPONADE*

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Abstract
The mechanism responsible for pulsus paradoxus was studied in closed-chest dogs during normal ventilation and exaggerated negative pressure breathing. A disturbance in the gradient between pulmonary venous and left atrial pressures was considered as the fundamental defect responsible for the increased respiratory variation of pulse during acutely induced pericardial tamponade. During tamponade, pulmonary venous pressure follows intrathoracic pressure, whereas left atrial pressure follows intrapericardial pressure. This results in a reduction of, or actual reversal of, the gradient between pulmonary venous and left atrial pressure during inspiration. This interferes with left ventricular filling even more than usual during inspiration, exaggerating the decrease in left ventricular stroke volume and the fall in systemic arterial pressure.

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