Methodological problems related to the quantitative assessment of stretch, elastic recoil, and balloon-artery ratio

The (inflated) balloon is important to determine the extent of stretch (theoretical maximal gain in diameter or area during PTCA), elastic recoil (the loss in diameter or area immediately after PTCA), and whether under- or over-sizing (balloon-artery ratio) of the dilated lesion occurred. In these assessments, the inflated balloon is used as scaling device with assumed uniformity along its entire length. In order to assess more accurately stretch, elastic recoil, and the balloon-artery ratio, the balloon diameter was measured over its entire length with edge detection and videodensitometry in 505 lesions (453 patients). With an average inflation pressure of 8.3 +/- 2.6 atm a difference between the minimal and the maximal balloon diameter of 0.59 +/- 0.23 mm was measured using edge detection and 1.70 +/- 0.90 mm2 difference in area using videodensitometry. This results in large variations in the calculated stretch, elastic recoil, and balloon-artery ratio depending on the site of the balloon chosen for assessment. The mean difference +/- SD between stretch and elastic recoil assessed by edge detection and videodensitometry (using the minimal luminal diameter or area of the balloon) are respectively 0.00 +/- 0.19 and 0.00 +/- 0.24, suggesting that both methods are appropriate.