Bovine jugular veins (BJVs) (Contegra) are valve-bearing pulmonary artery substitutes. Their valves have higher profiles than human pulmonary valves; this might result in less optimal performance. Therefore, we investigated the impact of stress and undersizing on conduit performance with ergometry, echocardiography and magnetic resonance imaging (MRI). Between April 2007 and June 2008, 20 BJV recipients (age 7.9-19.6 years) underwent spiroergometry and subsequent echocardiography; after due rest, ergometry was repeated and followed by MRI during recovery. A year later, exams were repeated. Data was evaluated as follows: comparison of stress related maximal individual valve performance changes (magnetic resonance: exercise induced average stroke volume changes by 61+/-49%; mean insufficiency increased by 2% in patients with <1% rest insufficiency and by 8% after rest insufficiency of >10%; the average rest gradient of 24+/-11 mmHg rose to 40+/-20 mmHg), and stratification of pooled observations by regurgitation fraction, insufficiency grades and z-values (insufficiency rose with increasing heart rate and decreasing stroke volume; undersizing increased gradients during recovery by 7+/-0.7 mmHg/z-value). Contegras high-profile valves tolerate stress without performance drop. Stress induced changes of insufficiency and gradient were clinically not significant, but sufficient to distort examination results; therefore, constant examination conditions are indispensable for a correct follow-up.