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Interventional Impatience With Stent Deployment—A Few Seemingly Long Seconds is Worth the Wait

Hovasse et al. report on a simple, clever, and clear method to assess stent expansion as a function of the duration of balloon inflation [1]. During the time course of stent deployment, there is continued expansion up to 25 sec. Over this half minute the proportion of inadequately expanded stents was reduced from 76.0% at 5 sec to 46.7% at 15 sec, and to 32.0% at 25 sec. Their message is clear. Stent deployment balloon inflations should be at least 25 sec. How did we come to need an answer to the question of time for stent deployment? In the pre-stent era, balloon inflations were usually minimum one minute [2], and we debated the merits of inflation durations of three or even 30 min or much longer [3]. The impatience of the interventional mentality in current practice has often reduced the time for stent deployment to the shortest possible inflate–deflate cycle of the delivery balloon. IVUS has consistently shown us that with angiographic guidance alone we often under-deploy stents [4]. This study does not completely connect improved stent expansion with 25 sec inflations to optimal deployment by intravascular ultrasound (IVUS) but still sends a clear signal that better stent expansion will result from longer delivery balloon inflations. Certainly, greater stent expansion is better, but if a stent is undersized to begin with, a longer inflation does not eliminate strut malapposition. The authors note that several factors contribute to stent expansion, including patient and lesion characteristics of the stent itself, and stent balloon deployment pressure. There are other critical factors, including the balloon:artery size ratio, stent metal composition, balloon compliance, inflation pressure, and most importantly the compliance of the artery. We have no way to practically assess lesion and vessel wall compliance, and as “luminologists” we ignore the vessel, and focus on the intravascular contrast column. In this report, the mean reference vessel diameter is 3.14 mm and the mean balloon diameter 3.0 mm. This balloon:artery ratio of 1 is ideal for a study. In practice, we often over or undersize. A larger or smaller balloon:artery size ratio in similar sized vessels, or the time course of stent expansion in smaller reference vessel sizes might be different. The continued evolution of stent metal composition, decreasing strut thickness, and improved stent delivery balloons add even more variables to the mix. Assessment of some of these variables might be the subject of future studies, and the simplicity of the methodology used by Hovasse et al. should facilitate future investigations. The number of and interaction of variables highlights the complexity of the stent expansion process, but does not negate the need to optimize our strategy for stent deployment. Waiting impatiently during stent deployment balloon inflations has a larger mental footprint that real time passed on the clock for the interventional physician. The term “New York minute” is used to describe an instant, or as an old comedian once said, it’s the interval between a Manhattan traffic light turning green and the guy behind you honking his horn. In cath lab practice, an interventionalist’s minute might be even shorter. A little patience at the critical procedural point of stent deployment is clearly worth the very short wait.