We report the case of a 76-year-old woman with mild-to-moderate mitral regurgitation due to rheumatic disease, severe dyspnoea, pulmonary hypertension and a recent episode of heart failure with paroxysmal atrial fibrillation. Transthoracic echocardiography at rest showed a mild-to-moderate mitral regurgitation, which was unable to justify the acute worsening of heart failure symptoms. During transesophageal echocardiography (TEE), deep anxiety induced sinus tachycardia and high SBP followed by pulmonary subedema. The TEE study ascertained a new-onset transient severe mitral regurgitation induced by stress and tachycardia. We speculate that the mechanism underlying the increasing of mitral regurgitation was related to the restricted motion of the posterior leaflet worsened by tachycardia. A further TEE, performed in the operating room under general anesthesia, thus without the emotional involvement of the patient, was not able to provoke a heart failure, even after dobutamine infusion, thus, downgrading the anatomical and functional mitral regurgitation severity.