Major pulmonary embolism and hemodynamic stability from shunting through a patent foramen ovale.

While the combination of a patent foramen ovale (PFO) and thromboembolic disease is thought to portend increased morbidity and mortality, PFO presence in the setting of major pulmonary embolism (PE) may serve as a means to rescue patients from immediate hemodynamic collapse and death. We present two patients with major pulmonary embolism and right-to-left shunting consistent with PFO as seen on transthoracic echocardiography. In the setting of major PE, PFO may prevent acute right ventricular failure by acting as a 'pop-off' valve, alleviating increased ventricular pressures; but concomitantly portend deleterious effects in the form of paradoxical embolism and intractable hypoxemia.