Primary vascular tumours of the heart are rare and heterogeneous in their presentation and classification. We present a primary intramuscular vascular malformation of the left ventricle in an asymptomatic 12-year-old girl. Characteristics on cardiac magnetic resonance imaging, specifically increased signal intensity on T2-weighted images, and marked contrast enhancement with gadolinium were suggestive of increased vascularity. Histologically, the mass was determined to be an intramuscular vascular malformation of the small vessel arteriovenous subtype. This represents one of a select few intramuscular vascular malformations of the left ventricle reported in children. Our patient remains completely asymptomatic and has had no change in the size and appearance of the mass after more than 30 months of follow-up.
