Arterio-venous malformations AVMs can be in any part of the body, the most common ones pulmonary, cerebral and hepatic. Pulmonary AVMs are R → L shunts, small shunts are asymptomatic, larger ones can cause desaturation/ cyanosis and congestive heart failure. Systemic AVMs are L → R shunts, small shunts are mostly asymptomatic, whereas larger ones cause congestive heart failure (high output failure). Coronary AVMs cause a L → R shunt at coronary level and can cause coronary steal with myocardial ischaemia and heart failure. 50% of cases are asymptomatic.