A 75 year old woman presented with out of hospital cardiac arrest following sudden breathlessness. She was resuscitated and transferred to the Emergency department where she was intubated and 300 ml of blood stained fluid was aspirated from the endotracheal tube.

Chest radiograph showed right sided pulmonary oedema with sparing of the left lung. Transthoracic and subsequent transoesophageal echocardiography showed a flail anterior leaflet of the mitral valve with preserved left ventricular function.

She underwent emergency coronary angiography and then mitral valve replacement. Unfortunately despite multi-organ support she died on post-op day 2.

Unilateral pulmonary oedema is uncommon, seen in approximately 2% of cases. It is strongly associated with mitral valve rupture and affects the right lung. It is thought to occur as the regurgitant jet is directed towards right pulmonary veins resulting in hydrostatic pulmonary oedema.

Unilateral pulmonary oedema should prompt urgent echocardiography to assess the mitral valve function (Figure 1).

Figure 1: Unilateral Pumonary Oedema.