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Qin et al. Vessel Plus 2020;4:2 I http://dx.doi.org/10.20517/2574-1209.2019.22 Page 7 of 8

be reinserted during treatment, which increases the surgery time and the risk of complications; however,
[13]
the new perfusion balloon is expensive, which limits its clinical application. It has been reported that
this drug could be injected into the target vessel through the side hole of the balloon by using a modified
balloon catheter, and the high local concentration of this drug was used to treat slow blood flow/no reflow.
However, the operation including the abovementioned methods is relatively complex, requiring a more
extensive operation and prolonging the operation time, thus this procedure is not suitable for use in
emergency PCI at most chest pain centers. In this study, rhPro-UK was directly injected into the coronary
artery through a guiding catheter. This operation process is simple and does not affect the operation flow.
We aimed to adopt a simple and low-cost method. At present, in the process of promoting the construction
of a nationwide “chest pain center”in China, this method has been shown to be suitable for most chest
pain centers. Although the administration of a guiding catheter leads to the outflow of part of the rhPro-
UK out of the guiding catheter, most of the drug can reach the middle and distal end of the affected vessel
in the direction of the blood flow, achieving effective results. In this study, there was no difference in the
time from the onset to balloon dilatation and from admission to balloon dilatation between the Pro-UK
group and the control group, suggesting that the administration of drugs through the guiding catheter
did not affect the operation time and procedure. Additionally, with the improvement of myocardial
reperfusion, there was no significant difference in the results of cardiac color Doppler ultrasounds between
the two groups, including LVEF, LVEDd, ventricular aneurysm, ventricular thrombus, and segmental wall
[14]
motion abnormality. Reinstadler et al. found that the ST-segment return rate was an important index
of myocardial perfusion after emergency PCI. There was no difference in the ECG ST-segment return rate
[15]
between the two groups. Previous studies have shown that a higher Killip grade is associated with higher
mortality. In our study, MACEs were positively correlated with the Killip grade, as higher Killip grades
were associated with a higher incidence of MACEs, which is consistent with the results described above.
MACEs are a new clinically feasible measure of the accurate, rapid, and safe evaluation of myocardial
[16]
perfusion . During the follow-up period of one month, there was no difference in MACEs between the
two groups. In this study, the ST return rate, based on ECG and color Doppler echocardiography, and
MACEs were studied. There was no difference between the Pro-UK group and the control group in regard
to these parameters. Multivariate regression analysis showed that there was no significant association
between the use of rhPro-UK and the risk of MACEs. In conclusion, in conditions of high thrombus load
during emergency PCI, rhPro-UK administration to the IRA through a guiding catheter was not associated
with an increase in the incidence of bleeding complications and MACEs, suggesting that this method is
safe and effective.

This study, in addition to having an insufficient sample size and a short follow-up time, was not a
randomized controlled prospective study. Additionally, there was no standard dosage for all patients in
the Pro-UK group. Considering that different dosages and routes of administration may affect the efficacy
and safety of the drug, further study is needed to explore the optimal dose and route of administration of
rhPro-UK in IRAs.

DECLARATIONS
Authors’ contributions
Conceived the study, collected the data, participated in the design and drafted the manuscript: Qin ZA, Lu
XL
Participated in the design, collected the data, performed statistical analysis and helped to draft the
manuscript: Qin ZA, Zhou Q, Lu XL
Helped to perform statistical analysis and to revise it critically for important intellectual content: Qin ZA,
Luo L, Zhan ZX, Guo N, Ge LQ
All authors read and approved the final manuscript.