A comparison of peak-to-peak pulmonary transit time determined by digital intravenous angiography with standard dye-dilution techniques in anesthetized dogs.

To evaluate the relationship between mean pulmonary transit time and peak-to-peak transit time by digital intravenous angiography six dogs were assessed during either isoproterenol or phenylephrine infusion. Acutely anesthetized dogs were instrumented with catheters in the pulmonary artery, left atrium, and carotid artery. An injection catheter was placed in the inferior vena cava, and contrast injections were made with a power injector (30 cc/second for 1 second of Renografin 76). Peak-to-peak transit times (pulmonary artery-left atrial time) were derived from videodensitometric time-absorption curves. Mean transit time was calculated from the usual optical densitometric analyses of green dye injected first in the pulmonary artery and then in the left atrium (sampled in a carotid artery). Peak-to-peak times averaged 3.6% greater than mean transit time (4.39 +/- 1.76 seconds vs. 4.24 +/- 1.82 seconds, P less than .05), though they correlated well with green dye values (r = .97; y = .97 x +.44). It was concluded that peak-to-peak transit times are excellent approximates of standard dye-dilution mean transit times and may simplify calculations of the pulmonary circulation when videodensitometric or radionuclide techniques are utilized.