A case of idiopathic dilatation of the pulmonary artery with mild subvalvular pulmonary stenosis revealed by cardiovascular magnetic resonance.

We present herein a rare case of idiopathic pulmonary artery dilatation with mild subvalvular pulmonary stenosis. The chest radiograph showed the protrusion of the left second arch of the cardiac silhouette. Cardiovascular magnetic resonance revealed an aneurysmal pulmonary trunk (maximal diameter, 4.5 cm) and mild subvalvular pulmonary stenosis. The pressure gradient across the pulmonary valve was mild (peak-to-peak, 11 mmHg), and the right ventricular pressure was normal. We diagnosed this case with idiopathic dilatation of the pulmonary artery by excluding other causes of pulmonary arterial enlargement.