Advanced technology: clinical blessing or clinical blinders?

Clinical Blinders? To the Editor: In their article “Occult anomalous pulmonary venous drainage: the clinical value of cardiac magnetic resonance imaging,”1 Dr Tan and colleagues present elegant magnetic resonance images from a patient with total anomalous right pulmonary venous drainage into the inferior vena cava (Scimitar syndrome). Their article demonstrates the superb graphic capability of MRI and also provides evidence of the hemodynamic or functional value of magnetic resonance flow mapping in quantitating the magnitude of a left-to-right shunt. The authors’ addition of “occult” to their title, however, implies that high-tech MRI was critical to the diagnosis. I question the occult nature of this anomaly. Given that the ratio of pulmonary blood to systolic blood flow was 2.7:1, one would anticipate highly suggestive bedside findings such as a palpable lift over the right ventricle, a pulmonary ejection murmur, a persistently split second sound, and even a tricuspid inflow rumble. The contrast-enhanced magnetic resonance pulmonary venous angiogram (Figure 3 in Tan et al)1 suggests that this “scimitar” might even have been visible on plain chest radiography. Further, transthoracic and transesophageal echocardiography, which were performed before MRI, seem to have replaced, rather than augmented, the physical examination. At right-heart catheterization, a left-to-right shunt was identified at the right atrial level. The careful collection of a series of blood samples to document oxygen saturation from the superior vena cava to the inferior vena cava would have pinpointed the location of the shunt to the high inferior vena cava. Moreover, manipulation of the catheter would have permitted entry into the common vein draining the right upper and lower pulmonary veins. There, an injection of contrast medium would have illuminated the “occult.” Undeniably, MRI and other technical advances of the recent past have added immeasurably to our diagnostic and therapeutic acumen. It is not correct, however, to create the impression that MRI was, in this case, required to bring light out of darkness. The proper performance of a right-heart catheterization in searching for a shunt, a skill best appreciated nowadays by our pediatric cardiology colleagues, still needs to be taught to our adult cardiology trainees if we are to expect them to recognize conditions that might otherwise be considered occult. In this time of escalating medical costs, we have an obligation to use all of our resources with care and reason.