Disease Characteristics of IR-CAD: a Case-control Study

A special type of coronary artery disease (CAD) has been identified in the investigators' clinical practice, which has completely different clinical features from those of typical atherosclerotic coronary artery disease (AS-CAD). The patients often have sterile inflammatory diseases and/or clinical evidence of inflammation, whose CAD progresses rapidly, recurs frequently, and responds poorly to intensified secondary prevention of AS-CAD, especially after percutaneous coronary intervention (PCI). The investigators name this special type of CAD with inflammation-associated rapidly-progressive coronary artery disease (IR-CAD). Currently, the overall disease characteristics of IR-CAD remain unknown.

The present case-control study is designed to investigate the disease characteristics of IR-CAD by comparing the demographics, clinical features, lab results, imaging findings, and prior treatment between 20 patients with IR-CAD and 10 patients with AS-CAD.

The first 20 patients who were enrolled in the IR-CAD cohort study, which included patients who met the inclusion/exclusion criteria for IR-CAD and received comprehensive treatment, will be enrolled in the case group of the present IR-CAD case-control study. Patients were diagnosed as IR-CAD if they have 1) evidence of rapidly progressive (occurred within 6 months or occurred on immunosuppressive therapy within 12 months of the last coronary revascularization) myocardial ischemia (typical symptoms and non-invasive evidence) despite standard treatment for secondary prevention of AS-CAD; 2) angiographic evidence of new coronary lesions (de novo stenosis or restenosis) considered to be relevant to myocardial ischemia; 3) evidence of inflammation (positive inflammation markers or established diagnosis of inflammatory diseases or use of immunosuppressive therapy). The comprehensive treatment for IR-CAD included: 1) intensified secondary prevention of AS-CAD; 2) immunosuppressive therapy; 3) coronary revascularization; 4) supportive therapies.

Patients who fulfill the inclusion/exclusion criteria for AS-CAD defined by the protocol of the present case-control study will be enrolled in the control group of the present case-control study. Patients will be diagnoses as AS-CAD if they 1) are ≥ 45 but < 65 years of age; 2) are receiving standard treatment for secondary prevention of AS-CAD after the last PCI which was performed 12±6 months ago; 3) do not have evidence of rapidly progressive (occurred within 6 months or occurred on immunosuppressive therapy within 12 months of the last PCI) myocardial ischemia (typical symptoms and non-invasive evidence); 4) do not have angiographic evidence of new coronary lesions (de novo stenosis or restenosis) considered to be relevant to myocardial ischemia.

Patients in the IR-CAD cohort study underwent examinations after they met the inclusion/exclusion criteria for IR-CAD based on a protocol specifically designed for the clinical management of IR-CAD patients. The results of the above examinations will be used as the examination results of the case group of the present IR-CAD case-control study. While patients in the control group of the present case-control study will undergo similar examinations after enrollment according to the protocol of the present case-control study.

The information regarding the baseline characteristics and the examination results, including demographics, clinical features, lab results, imaging findings, and prior treatment, will be collected and compared between the case group and the control group.

The primary endpoint is the rate of elevated erythrocyte sedimentation rate (ESR).

Eligible patients will be enrolled in the case group and the control group with a 2:1 ratio. The primary endpoint of the present case-control study is elevated erythrocyte sedimentation rate (ESR), which is defined as ESR > 15 mm for male, or ESR > 20 mm for female. In case of normal ESR, prior use of immunosuppressive therapy or prior diagnosis of autoimmune diseases before enrollment is regarded as the equivalent to elevated ESR. Based on currently available data from the IR-CAD cohort study, the rate of elevated ESR in the case group (IR-CAD patients) is 88.9% (8/9). The investigators hypothesize that the rate of elevated ESR in the control group (AS-CAD patients) is 20%. In consequence, 20 patients in the case group and 10 patients in the control group would be required to test the difference of the rate of the primary endpoint between the two groups at a significance level of 0.05 (α = 0.05) with a power of 90% (β = 0.10) and a drop-out rate of 20%.

Continuous variables will be presented as mean ± standard deviation (SD) or median (interquartile range [IQR]) and compared with two-sample t-test or Wilcoxon rank sum test, as appropriate. Categorical data will be demonstrated as n (%) and compared using Chi-square test or Fisher's exact test, as appropriate.