Variations in pulmonary venous drainage to the left atrium: implications for radiofrequency ablation.

PURPOSE To evaluate and classify the various drainage patterns of the pulmonary veins as depicted with thin-section chest computed tomography (CT). MATERIALS AND METHODS Thin-section (2.5-mm collimation) contrast material-enhanced CT scans of 201 consecutive patients obtained over a 3-month period for diagnosis of pulmonary embolism (n = 197), pulmonary vein stenosis (n = 2), or aortic injury (n = 2) were routinely reviewed in transverse and (if necessary) coronal and coronal-oblique imaging planes. A classification was formulated based on both the number of venous ostia on each side and the drainage patterns of pulmonary veins. The frequency of each pattern was determined, and association with atrial arrhythmia was assessed with the chi(2) and Fisher exact tests. RESULTS Most patients (n = 142, 71%) had two ostia on the right side for upper and lower lobe veins. Fifty-six patients (28%) had three to five ostia on the right side, which were due to one or two separate middle lobe vein ostia in 52 (26%) patients. Three patients (2%) had a single venous ostium on the right side. Most patients (n = 173, 86%) had two ostia on the left side for upper and lower lobe veins. The remainder (n = 28, 14%) had a single ostium. There was no significant association between any particular venous drainage pattern and atrial arrhythmia; however, patients with a separate ostia for the right middle lobe pulmonary vein(s) tended to have a higher frequency of atrial arrhythmia than those with other patterns (P =.053). CONCLUSION A classification system to succinctly describe pulmonary venous drainage patterns was developed. Right-sided venous drainage was more variable than left-sided venous drainage. One-quarter of patients had more than two venous ostia on the right side.