A total of 149 continuously T2DM patients at the Affiliated Hospital of Jining Medical University without known symptoms suggestive of CHD who underwent CCTA from July 2019 to December 2019 were enrolled in the study. All T2DM patients had at least one other cardiovascular risk factor such as hypertension, dyslipidemia, smoking, lack of exercise, and family history of myocardial infarction in first-degree relatives.
T2DM was confirmed according to the criteria of the American Diabetes Association (15): Glycated hemoglobin (HbA1c) levels ≥6.5%, fasting blood glucose levels ≥7.0 mmol/l and/or a postchallenge blood glucose level ≥11.1 mmol/l (2 hours after a 75 g oral glucose load) or the current use of hypoglycemic treatment. The symptom asymptomatic status of the patients was evaluated using the Rose questionnaire for angina. Patients without CHD were defined as asymptomatic.
The exclusion criteria were as follows: type 1 diabetes; known or suspected CHD; abnormal resting electrocardiographic results; history of prior myocardial infarction, history of coronary artery bypass grafting or stenting; and incomplete clinical data.
Ninety-three other continuous non-T2DM non-CHD patients at the Affiliated Hospital of Jining Medical University who underwent CCTA in December 2019 were chosen as the control group.
CHD fatal risk stratification prediction
The CHD fatal risk stratification of T2DM patients was forecasted by the United Kingdom Prospective Diabetes Study (UKPDS) risk engine 2.0 (http://www.dtu.ox.ac.uk/riskengine/). The UKPDS is a group of clinical trials, epidemiological analyses and health-modeling studies with an influence that can be assessed across a broad range of health domains. The UKPDS made the risk of age, hyperglycemia, elevated blood pressure, adverse blood lipids and smoking contributions more clear. Equations were developed, combined and incorporated into the UKPDS risk engine. The UKPDS risk engine provides risk estimates in individuals with T2DM not known to have heart disease (16, 17).
A structured interview was performed to record the demographic and clinical data. The following characteristics were used to calculate the patients’ CHD fatal risk: age, duration of diabetes, sex, ethnicity, atrial fibrillation, smoking history, HbA1c, systolic blood pressure, total cholesterol and high-density lipoprotein (HDL) cholesterol. A positive smoking history was defined as current smoking or cessation of smoking within three months.
Multidetector CT Scan Protocol and image reconstruction
CCTA was performed using a dual source CT scanner (SOMATOM Definition Flash dual-source; Siemens Medical Solutions, Erlangen, Germany) following standard guidelines (18).
During the CCTA acquisition, 50-80 ml iodinated contrast (Ultravist 370, Bayer Schering, Berlin, Germany) was injected based on the individual’s weight, followed by a 30 ml saline flush, the injection rate was 5-7 ml/s. A retrospective ECG-gated spiral scan was performed covering the region immediately beneath the aortic arch to the apex of the left ventricle during an inspiratory breath hold of 10-20 s. The scan parameters were as follows: gantry rotation for 330-420 ms, spiral imaging with retrospective ECG gating and automatic dose modulation, 750-850 mA, 100 kV or 120 kV and 0.75 mm slice thickness, 128×0.6 mm collimation. A multisegment algorithm was used to reconstruct overlapping images, typically at 75% of the cardiac cycle in central diastole. If motion artifacts were present, additional reconstructions were made at different points of the R-R interval, as needed. All reconstructed datasets were sent to a dedicated workstation (syngo.via VA 20B, Siemens Healthcare) for postprocessing and three dimensional reconstruction.
Coronary stenosis analysis
The coronary arteries were divided into 18 segments following the Society of Cardiovascular Computed Tomography guidelines (19). Each segment was examined for coronary plaques. The structures of >1 mm2 and adjacent to or within the coronary artery lumen that could be clearly separated from the vessel lumen were scored as a coronary plaque (20). Each coronary segment was scored individually for the presence of plaque, and any stenosis was visually quantified. Coronary stenosis was assessed by the following clinical coronary plaque scores: the segment stenosis score (SSS); segment involvement score (SIS); stenosis coefficient (SC); and severe proximal plaque (SPP) (21).
The SIS reflected the plaque distribution and was calculated as the total number of coronary artery segments exhibiting plaque, irrespective of the degree of luminal stenosis within each segment (scores from 0 to 18). The SSS was used as a measure of the overall coronary artery plaque burden. Each individual coronary segment was graded as having no to severe plaque (scores from 0 to 3) based on the extent of the obstruction of the coronary luminal diameter. Then, the extent scores of all 18 individual segments were summed to yield a total score. The SC was defined as the ratio of the SSS to SIS (the SC was defined as 0 when the SIS was 0), which reflected the degree of artery stenosis. The presence of any severe plaque in the left main or proximal portion of the left anterior descending, left circumflex and right coronary arteries was defined as SPP positive. A vessel stenosis greater than 70% was defined as a severe plaque. An obstructed coronary vessel was defined as a ≥50% reduction in the diameter of the lumen (21, 22).
The examination results were independently interpreted and summarized by two doctors with more than five years of CCTA diagnosis experience. If there was any difference, the final results were decided by the two doctors after consultation and discussion.
Continuous variables with a normal distribution are presented as the mean ± standard deviation; nonnormal variables are presented as the median (interquartile range). Categorical variables were expressed as frequencies. Continuous variables were compared by the Mann Whitney U test or Kruskal Wallis test. Differences in the categorical variables were assessed using the χ2 test. The association of T2DM and CCTA findings was analyzed by binary logistic regression. All statistical analyses were performed using SPSS 26.0 software (SPSS, Inc., Chicago, IL, USA), and p<0.05 was considered statistically significant.