Influence of the speed of deflation of the stent delivery system in the myocardial blush and ST-segment resolution in primary angioplasty: a randomized study

Introduction

Distal embolization may compromise the results of primary angioplasty. Our aim is to analyze the influence of the speed of deflation of the stent delivery system on the myocardial blush ≥2 and on the ST-Segment resolution ≥70%.

Methods

From December 2016 to February 2019, all consecutive patients with ST-elevation myocardial infarction who underwent urgent coronary angiography at our institution who were susceptible of thrombectomy, IIB-IIIA inhibitors and direct stenting were randomized 1:1 to fast deflation of the stent delivery system (group 1, n=103) or to slow deflation at 1 atm/second (group 2, n=107). Pre- and postdilatation was not allowed per protocol. The primary outcomes were the myocardial blush ≥2 and the ST-Segment resolution ≥70% while the size of myocardial damage, ejection fraction at discharge and at 12 months and total and cardiovascular mortality at 12 months were the secondary outcomes. A multivariate analysis was performed to analyze the influence of the speed of deflation of the stent delivery system in both primary end-points in case of possible imbalances among groups despite the randomization.

Results

Both groups represented 47% of the 447 procedures of primary angioplasty performed in that period. Baseline characteristics of the whole cohort: female gender 46 (21.9%), age 59.5±10.6 years, diabetes 35 (16.7%), Killip class IV 5 (2.4%), total ischemic time 177.5 (124–275) minutes and door to balloon time 84 (66–120.5) minutes. There were not differences in clinical or angiographic characteristics between both groups, although there was a non-significant trend towards larger reference vessel diameter in the slow deflation group (2.74±0.42 vs. 2.86±0.47, p=0.07). The study was prematurely stopped with 50% of the calculated sample size due to futility. The primary endpoint of myocardial blush ≥2 occurred in 77 (74.7%) vs. 79 (75.2%), p=0.93 and ST-Segment resolution ≥70% in 54 (53.9%) vs. 59 (55.5%), p=0.75 in group 1 and 2, respectively, without differences in any of the secondary endpoints. The speed of deflation of the stent delivery system did not show any influence on the MB or ST-Segment resolution ≥70% in the multivariate analysis. Predictors of myocardial blush ≥2 were systolic blood pressure at admission, creatinine clearance <60 ml/min and maximal diameter postprocedure. Diabetes, previous infarction, left anterior descending, TIMI ≥2 before intervention, TIMI 3 after intervention and collateral supply grade ≥2 were predictors of ST segment resolution≥70% with an area under the curve of 0.71 (0.63–0.80) and 0.75 (0.68–0.82), respectively.

Conclusions

In our series, the speed of deflation of the stent delivery system in primary angioplasty did not modified the myocardial blush ≥2 or ST-Segment resolution ≥70% and neither showed any influence in clinical outcomes, size of myocardial infarction by biomarkers and ejection fraction.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Abbott Laboratories

Theory and simulation of buoyancy-driven convection around growing protein crystals in microgravity

We present an order-of-magnitude analysis of the Navier-Stokes equations in a time-dependent, incompressible and Boussinesq formulation. The hypothesis employed of two different length scales allows one to determine the different flow regimes on the basis of the geometrical and thermodynamical parameters alone, without solving the Navier-Stokes equations. The order-of-magnitude analysis is then applied to the field of protein crystallization, and to the flow field around a crystal, where the driving forces are solutal buoyancy-driven convection, from density dependence on species concentration, and sedimentation caused by the different densities of the crystal and the protein solution. The main result of this paper is to provide predictions of the conditions in which a crystal is growing in a convective regime, rather than in the ideal diffusive state, even under the typical microgravity conditions of space platforms.