Implication of Renal Impairment for Acute Coronary Syndrome

The Global Burden of Disease, Injuries, and Risk Factors Study shows that the prevalence of chronic kidney disease (CKD) has increased by 29.3% from 1990 to 2017.¹ Particularly, the prevalence of moderate-advanced CKD (stages 3–5) in Japan is absolutely higher than that in the USA. Moreover, even in the Japanese general population, a progressive decline in renal function is seen as people age.² In addition, diabetes, hypertension, etc may be related to a faster decline in the glomerular filtration rate (GFR).

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On the other hand, the incidence of acute myocardial infarction (AMI) is significantly decreasing after 2000 in the USA,³ but in Japan it absolutely increased between 1979 and 2008.⁴ During that time, the prevalence of major coronary risk factors, including hypertension, diabetes mellitus, and dyslipidemia, significantly increased in Japan, so the reason why the incidence of AMI increased may be insufficient control of risk factors. Such coronary risk factors are also well-known as factors that deteriorate renal function.

In this issue of the Journal, Kai et al⁵ report that renal dysfunction is associated with coronary microvascular dysfunction and obstruction after primary percutaneous coronary intervention (PCI) in patients with ST-elevation myocardial infarction (STEMI). Essentially, there is a close relationship between impaired renal function and coronary flow.⁶ Moreover, patients with CKD stages 3a and 3b have higher lipid and lower fibrous content in coronary plaques, contributing to greater vulnerability. Indeed, studies suggest that there is a close association between renal function and coronary plaque composition and that reduced lower GFR levels may be predictive for lipid-rich composition of coronary plaque, which is considered a histologic markers of plaque vulnerability related to the risk of plaque rupture.⁷ Therefore, the findings of Kai et al⁵ seem so surprising. However, until now, there have been limited reports of the relationship between renal function and microcirculatory impairment after primary PCI in patients with STEMI. The issue alerts us to various risks in CKD patients undergoing PCI for acute coronary syndrome (Figure).

Figure.

Risks of PCI in CKD patients. ACS, acute coronary syndrome; CI-AKI, contrast-induced acute kidney injury; CKD, chronic kidney disease; LV, left ventricle; PCI, percutaneous coronary intervention.

Patients with slow flow/no-reflow have a larger infarct size than those without the phenomenon. In addition, the total amount of contrast media may be increased in patients with slow flow/no-reflow because frequent angiography may be essential to confirm coronary flow. An increased volume of contrast media directly affects the onset of contrast-induced acute kidney injury (CI-AKI), as well as the unstable condition of STEMI patients. Needless to say, both a large infarct and CI-AKI are associated with poor prognosis in STEMI patients. Therefore, physicians should pay an attention to performing direct PCI in STEMI patients with renal impairment.

One important point of the study was that ST resolution was used to evaluate microvascular dysfunction. Recently, various imaging modalities have been used to assess microcirculatory impairment. However, even now, ECG is the simple and cheap option that can be used and evaluated almost anywhere. Clinicians should realize the importance of evaluating the ECG in STEMI patients undergoing primary PCI again.

It has been reported that proteinuria strongly predicts worse clinical outcomes than GFR.⁸ The JDDM54 study clearly showed a higher risk of cardiovascular disease in patients with albuminuric diabetic kidney disease without reduced estimated GFR even if they had no prior cardiovascular disease.⁹ However, cardiologists often do not measure albuminuria in the clinical setting. Proteinuria plays an important role during the pathogenesis of progressive renal dysfunction,¹⁰ so we should collect data on the importance of proteinuria in coronary reperfusion therapy.

Because Japan is ahead of any other country in the world in the advance to a super-old society, there are increasing concerns regarding both CKD itself and its comorbidities that are related to cardiovascular events. Therefore, research and studies regarding the interaction between the heart and kidneys, which is known as ‘cardiorenal interaction’ should be developed.

Disclosures

H. Ishii received lecture fees from Astellas Pharma Inc., Astrazeneca Inc., Bayer Pharmaceutical Co., Ltd., Bristol-Myers Squibb Inc., Chugai Pharmaceutical Co., Ltd., Daiichi-Sankyo Pharma Inc., and MSD K. K.

H. Ishii is a member of Circulation Journal’s Editorial Team.

IRB Information / Reference Number

None.

References

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