Subarachnoid hemorrhage is associated with high morbidity and mortality, and cerebral arterial vasospasm is one of its main complications that determines neurological prognosis. The use of intravenous milrinone is becoming more common in the treatment of vasospasm. This molecule has positive inotropic and vasodilating properties by inhibiting phosphodiesterase-3. Its most described side effects are cardiac arrhythmias and arterial hypotension. In this paper, we raise a new issue concerning milrinone and discuss an undescribed side effect of this treatment, left ventricular outflow tract obstruction (LVOTO). Dynamic LVOTO is a clinical situation favored by hypovolemia, decreased left ventricular afterload, and excessive inotropism that can lead to severe hemodynamic failure and pulmonary edema. To our knowledge, this is the first study describing milrinone-induced LVOTO. This could compromise cerebral perfusion and therefore the neurological prognosis of patients. While it is known that catecholamines may induce LVOTO, milrinone-induced LVOTO appears to be a new pathophysiological entity of which neurosurgical intensivists should be aware.