Rapid Inflation/Deflation Compared With Prolonged High-Pressure Balloon Inflation

Overview

It is universally accepted that high-pressure balloon inflation is required to most effectively deploy a coronary balloon-expandable stent. However, there is not consensus nor are there any guidelines regarding the method of balloon inflation, particularly the duration of inflation. Underexpansion and strut malapposition after stent deployment are among the most powerful predictors for adverse vessel outcomes. High-pressure inflation for stent deployment is effective to optimally expand the stent, but unlike in vitro testing in air, there are poorly distensible plaque elements that may not instantaneously yield to the balloon pressure. However, these elements may ultimately yield to prolonged inflation. Most clinical interventional cardiologists inflate for a relatively short period (15-30 sec). The investigators have noted that when balloon pressure is maintained at a certain pressure level it tends to decrease over time, and may require 60-180 or more seconds to maintain pressure stability. This finding implies that plaque elements are yielding slowly over time to the increased pressure, thus increasing expansion, and suggests that a prolonged inflation until balloon pressure stabilizes is more effective than a rapid inflation/deflation sequence to fully expand and appose the stent to the vessel wall. At present there is no consensus on stent deployment strategy. It is our hypothesis that prolonged inflation is superior to the more commonly used strategy of rapid inflation/deflation. Optimal coherence tomography (OCT), a novel technology that measures near-infrared light reflections and translates them into a 2D image, has an axial resolution nearly 10-times that of intravascular ultrasound (IVUS). Thus it is possible to examine the extent of stent malposition and stent expansion using this modality. The current randomized trial tests the hypothesis that prolonged balloon inflation until a stable balloon pressure is maintained is more effective than a rapid inflation/deflation sequence when performed to the same balloon inflation pressure.

The rapid inflation method (termed rapid) will consist of reaching a high-pressure (16 atmospheres)with the stent-deployment balloon and maintaining it the duration of time determined by the operator but \<30 sec if the balloon is fully deflated and longer only if the balloon requires a longer duration to become fully inflated. Based on previous data, the average time will likely be in the 20-30 sec range. Prolonged inflation (termed prolonged) will be performed at high pressure (16 atmospheres) and maintained for 30 sec with \<0.3 atmospheres drop during that period. For example, in the case of 16 atmospheres, the prolonged inflation will require a steady pressure of 15.8-16 atmospheres for at least 30 sec. If the inflation pressure falls 0.3 further pressure will be applied using the digital inflation device until it is again at the target pressure, resetting the 30 second clock. It should be emphasized that if at any time during prolonged inflation there is hemodynamic or electrocardiographic instability, the balloon will be deflated. Based on our previous experience we do not anticipate any safety issues; however, we will measure safety parameters as noted below. After either the rapid or prolonged inflation, an OCT run will be performed to delineate stent expansion and strut apposition. Should the operator determine that the OCT appearance of the stent is unsatisfactory, it is left to the operator to proceed as clinically required, using any further approaches, as he or she sees fit. The results of any further intervention, however, will not be included as part of the data analysis. The study period consists of randomization through the end of the coronary intervention within the catheterization laboratory, for both the efficacy and safety endpoint. The study period will be monitored continuously by a research coordinator and an investigator. All adverse events as described under Safety end points will be reported to the Institutional Review Board (IRB) as per the IRBs prescribed time frame.