Balloon angioplasty optimization: should we measure balloon volume as well as pressure?

To investigate the influence that measurement of balloon volume as a controlled variable in addition to balloon pressure has on the outcome of balloon angioplasty in an experimental model.

One hundred and three segments of explanted normal porcine carotid arteries were obtained. Five were used as controls, and the remaining 98 were subjected to balloon angioplasty with simultaneous measurement of balloon volume and pressure. These arteries were randomized into two groups. In one group the endpoint of the angioplasty was determined by balloon pressure (pressure-limited group, PLG) and in the other group by balloon volume (volume-limited group, VLG). Pressure/volume curves for each procedure were constructed by continuous measurement of both parameters by a purpose-designed computer-controlled inflation device. The diameter of each arterial segment was measured by intravascular ultrasound (IVUS) and the ratio of the inflated balloon to arterial diameter calculated. Arterial appearances after angioplasty were recorded using IVUS.

The balloon volumes measured at the endpoint of angioplasty were significantly smaller in the PLG compared with the VLG (p < 0.001). Three types of pressure/volume curves were identified: A, B, and C. In the type A curves, IVUS identified fissures in 28% (17/60) and the examination was normal in 72% (43/60). In the type B curves, IVUS identified fissures in 44% (4/9), dissections in 22% (2/9), and the examination was normal in 33% (3/9). In the type C curves, IVUS identified fissures in 44% (4/9) and dissection in 56% (5/9) with no normal examinations. In undamaged arterial segments a very high correlation was achieved between balloon volume and the balloon/artery ratio (Pearson correlation = -0.979, R(2) = 0.957, p < 0.0001, n = 27).

The measurement of pressure and volume during angioplasty enabled the construction of pressure/volume curves that showed deviations from the curves obtained in air. The balloon volume results, and significant deviation of the curve shape from the control curve shape, predicted vessel damage, which was confirmed by the IVUS appearance of the vessel after angioplasty. When pressure was used as the endpoint of balloon inflation the balloons were significantly underdilated compared with the manufacturer's nominal sizes. These data indicate that monitoring of pressure and volume during angioplasty may provide an alternative method of predicting vessel damage.