Instead on differentiating variant from anomaly based on possible prognostics, some use the term as a measure of prevalence: anomalies are fewer than 1%... variations more than this.
One interesting and extremely rare anomaly that arises in 0.025 - 0.04% of patients is the single coronary artery.
The single coronary artery can arise from either the right or left cusp and continue with a coronary artery on the same side with a branch to the opposite side... or it can have a completely anomalous course. Like with the "malignant course" mentioned above, a patient is at increased risk for sudden death if the coronary crosses between the pulmonary artery and the aorta. A proximal stenosis in a single coronary artery is likewise a grave problem since obviously both vascular territories are at risk.
|Single coronary artery in an 80Y man. Oblique VR image of the top of the heart shows only one coronary artery arising from the left coronary sinus. The RCA courses between the aorta and the pulmonary artery (Radiographics).|
|Single coronary artery in an 80Y man. On a sagittal oblique VR image, the single coronary artery demonstrates a high takeoff above the sinotubular junction (Radiographics)|
|Single coronary artery in a 55Y man. Coronary angiogram shows the anomalous origin of the hypoplastic RCA which arises from the LAD and courses anteriorly to the pulmonary artery (Radiographics)|
Some sources state that a single coronary artery is associated with other cardiac anomalies and a careful evaluation of the rest of the heart should be pursued. A classification scheme has also been proposed, bascially dividing between a dominant single coronary artery that supplies the whole myocardium (group 1) and a single coronary artery ostium and single coronary artery trunk that bifurcates into the left and right side of circulation (group 2). Due to the small numbers of patients, there does not seem to be a consensus whether the single coronary artery occurs more frequently on the left or right, or whether a group 1 or group 2 anomalies is more common.
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