The main findings of the present study were as follows. First, among 25 patients with ACS, the prevalence of abnormal MODD was high (96%) compared to the prevalence of DM (38%). Second, there was a correlation between MODD, a parameter of day-to-day GV, and NT-pro BNP, a parameter of cardiac function.
In the present study, 8 patients (32%) were diagnosed with diabetes at or before admission to the hospital. In contrast, MODD assessed by CGM was found to be over the normal level (> 10) in 24 (96%) patients. These results suggest that CGM may provide indications of diabetes and glucose intolerance in some patients who were considered normal using previous diagnostic methods. Previous reports have shown that when oral glucose tolerance testing (OGTT) was performed on patients admitted with ACS, 24% were diagnosed as diabetic, 38% as impaired glucose tolerance, and the remaining 38% as normal12, 13. Day-to-day assessment of blood glucose using CGM could identify patients with blood glucose variations beyond daily glucose variability.
We also found that a large number of ACS patients had GV, suggesting that blood glucose variability causes plaque instability and endothelial erosion, which may be a trigger for ACS. This is supported by a previous report that higher blood glucose variability is an important factor in coronary plaque vulnerability14, 15.
Although day-to-day GV in the acute phase may differ from day-to-day variability in regular outpatient care, it was suggested that incorporating CGM into routine diabetes care and measuring MODD may help to differentiate patients at high risk for ACS who are being impacted by GV.
We also examined the association between MODD and other indices. Despite the lack of correlation between peak CK and MODD, MODD was found to be associated with NT-pro BNP. MOD was not correlated with CK, which reflects the degree of myocardial infarction. In addition, there was no correlation between infarct size and MODD. On the other hand, the fact that MODD was correlated with NT-pro BNP, a marker of cardiac function, suggests the presence of prior myocardial dysfunction in addition to the myocardial infarction that caused the patient to be hospitalized. These results are not inconsistent with previous reports that daily and day-to-day GV increase oxidative stress and inflammation, which cause myocardial damage16–19. Recent investigations suggest that α-glucosidase inhibitor and glucagon-like peptide-1 analogue attenuate GV and inhibit oxidative injury20, 21. Therefore, we could improve prognosis using these drugs.
The significance of measuring MODD in patients with ACS is that the measurement can predict more heart failure symptoms beyond those expected based on infarct volume and may serve as a marker for more-intensive anti-cardiac therapy. In addition, CGM in DM routine practice may help in risk stratification of vulnerable patients with ACS.
Although some of the patients in this study had high HbA1c levels, these patients may have had less blood glucose variability and been less likely to have MODD abnormalities and therefore should have been omitted from the study, we included them due to the limited number of cases. Therefore, the correlation between MODD and NT-pro BNP in this study may be weak. In addition, OGTT was not used to diagnose diabetes at hospitalization. This may have resulted in a lower rate of diabetes diagnosis. However, the rate of elevated MODD was higher than the number of diagnoses of DM comorbidities and new DM cases on admission for ACS previously reported.