The differentiation of ischemic (I) versus non-ischemic (NI) cardiomyopathy (CMP) by non-invasive stress testing has been plagued by suboptimal sensitivity and specificity leading to coronary angiography. We used MDCT angiography as gold standard to assess if coronary calcium could be used as a simple screening tool to differentiate I versus NI CMP.
Out of six seventy six 64 slice MDCT angiograms we identified 98 patients with no prior documented CAD or angina referred for CAD evaluation for new onset left ventricular dysfunction (EF <50%). Using a CTA diagnosis of >50% obstructive lesion in any major coronary artery as indicative of ICMP we classified this group into non-ischemic (78) and ischemic (20) CMP. CCS was calculated using noncontrast CT prior to the MDCTA by standard methodology. Fischer exact and Student's t-test were used to compare the 2 groups and ROC analysis to determine the sensitivity and specificity of different CAC cutoffs for determining I or NICMP.
Age (NICMP 56+14 vs ICMP 63+ 12), female gender (NICMP 51% vs ICMP 30%), African American status (NICMP 59% vs IMP 50%), diabetes (NICMP 15% vs ICMP 33%) and smoking (NICM 37% vs ICMP 50%) were all comparable in both groups (all p value=NS). EF in both groups also were not different (NICMP 33+13% vs ICMP 34.8+12%, p=0.59). The mean calcium score was 80+150 in NICMP vs 340+397, p=<0.0001).ROC analysis demonstrated that a calcium score of 106 had the best sensitivity and specificity for differentiating I vs. NI etiology of CMP (sensitivity 75% specificity 81%, with AUC 0.82).
This study shows that CCS determination has good high sensitivity and high specificity for separating I vs NICMP and is comparable if not better than some of current stress test modalities by providing a simple direct measure of atherosclerosis burden.
In patients with a low-intermediate pre-test likelihood for CAD and no angina,CCS rather than stress testing may serve as useful initial screening tool for CMP assessment.A high CCS score could triage patients directly to cath and a low score to MDCTA with stress testing reserved for equivocal cases.This concept needs prospective validation.
Zehra Husain, No Financial Disclosure Information; No Product/Research Disclosure Information