Pictorial review: non-anatomical cardiovascular gas: causes, appearances and consequences.

Gas does not occur naturally in the cardiovascular system, although it is not unusual to identify it on imaging. The true incidence is difficult to know as asymptomatic cases are rarely recorded. In iatrogenic instance, this occurs when atmospheric air enters the cardiovascular system from a high to low pressure, or when gas is forcibly injected into a vessel. The source of air must be promptly identified and treatment must be expedited to reduce morbidity and mortality. This pictorial review aims to give an overview of the causes (with particular emphasis on the conditions that may be encountered by a Radiologist), appearances of cardiovascular gas, and any subsequent treatment.