Discussions
At present, the pathophysiological mechanism of CIN was not fully clear, which might be involved by multiple factors, including the direct toxicity of contrast agent on the kidney, renal hemodynamic changes and oxidative stress reaction, inflammation, and renal tubular obstruction, etc8-10. Contrast agent cloud induce that vacuoles formation, intracellular Ca2 + overload and adenosine triphosphate decreased in renal tubular epithelial cells, thus inducing apoptosis. There were two-phase effects of contrast agent on renal hemodynamics. Firstly, the application of contrast agent lead to renal vascular dilatation that mediators were consequently released. For example, endoderin stimulated progressive and continuous contraction of renal vessels, thereby leading to eGFR declining11. The generation of reactive oxygen species and oxygen free radicals increased dramatically. After binding with some amino acid residues of tissue proteins, proteins were easy to be hydrolyzed, polymerized and cross-linked, which affected the structure and function of cells and lead to oxidative stress reaction. Secondly, when contrast agents were filtered through the glomerulus into the renal tubules, they were viscous as a result of the absence of water in the tubules, which might lead to tubules obstruction and aggravate renal damage12. In this study, results showed that dosage of contrast agent had a positive association with CIN, which was similar to the previous studies13,14.
Studies had shown that the use of IABP as adjuvant therapy of PCI could effectively improve renal blood perfusion and have protective effects on renal function, which markedly reduced the incidence of postoperative renal insufficiency15,16. In this study, we found that the values of eGFR were significantly lower in the IABP duration ≤4 days group as compared to the IABP duration>4 days group in the three time section of IABP implantation. However, there were no significant differences in the values of eGFR, SCr among three time section of IABP implantation in any group. It manifested that IABP contributed to increase the patient’s urine output and improve serum creatinine level as soon as possible, which were conducive to reduce the occurrence of renal insufficiency and protect the patient’s kidney function.
AMI complicating pump failure was common in patients that areas of myocardial infarction accounted for more than 40% of the left ventricle, which significantly influenced cardiac pumping function. The aggravation of left ventricular filling pressure strengthened the myocardial oxygen consumption. Eventually, interaction of myocardial hypoxia, pump failure and myocardial ischemia necrosis developed into cardiac shock17. IABP using could alleviate the burden of the left ventricle and improve cardiac function through reducing left ventricular ejection resistance. Studies have shown that IABP enhanced the pulsation of coronary arteries and provided pulsed blood flow, which were beneficial to reduce the occurrence of acute occlusion and no reflow after PCI treatment18.
In this study, the duration of using IABP was not obviously related to incidence of 12-month MACEs and all-cause mortality. This reason might be explained that the patients with AMI complicating pump failure was in a state of severe ischemia, hypoxia, or even necrosis. Consequently, the perfusion of important organs suffered serious damage. At this time, IABP therapeutic therapy was often ineffective. Especially, elderly patients with AMI complicating CS were more likely to be complicated by vital organ dysfunction. There were more complications and higher mortality rates when they underwent IABP adjuvant therapy. A study indicated that the clinical implications were significantly increased with IABP using for more than two days19.
Several limitations should be recognized in this study. First, in consideration of patient safety, the control group without IABP treatment was not set up. Secondly, due to the lack of long-term follow-up data, the follow-up time could be appropriately extended and the long-term prognosis of patients could be further analyzed in detail. Finally, this study was a single-center, retrospective study, and the sample size was small, so the results of this study should be interpreted with caution.
In conclusion, longer duration of IABP implantation was beneficial to renal function, but was not significantly correlated with the incidence of 12-month MACEs and all-cause mortality in patients with AMI complicating pump failure. Patients undergoing PCI or CABG should notice that the potential damage of high dose of contrast agents on the renal function.
Acknowledgements The authors are grateful to thank all those who contributed to the study design and implementation.
Informed consent All participants provided informed consent, and approval to conduct the survey.
Ethical approval This study was granted by the Research Ethics Committee of University of Science and Technology of China.
Conflict of interest Statement The authors declare that they have no conflict of interest.