Computed tomography: The optimal imaging method for differentiation of ischemic vs non-ischemic cardiomyopathy.

Case history: 57-year-old woman presents with 8 month history of shortness of breath on exertion. She has no chest pain. She has history of hypertension and type 2 diabetes and both are well controlled with oral medications. The HR is 74 bpm and regular, BP140/ 85 mm Hg. The cardiac examination is normal. The ECG shows NSR and voltage criteria of LVH. The renal function is normal. TTE shows mildly enlarged LV, EF of 35%, and mild diffuse wall motion abnormality with trivial MR. The RV is normal. The PAS pressure is estimated at 35 mm Hg. Cardiomyopathies are diseases of the heart muscle and represent a heterogeneous group of disorders affecting the myocardium and ultimately resulting in heart failure. The primary diagnostic strategy is to determine the underlying cause of cardiomyopathy. Notably, there are causes that are treatable and may to some extent be reversible. Ischemic cardiomyopathy is the most common cause of dilated cardiomyopathy in the Western world and is associated with a worse adverse outcome. The differentiation between ischemic and non-ischemic cardiomyopathy is challenging, and has both important therapeutic and prognostic implications as patients with ischemia may benefit from coronary revascularization. In those patients with extensive coronary atherosclerotic disease (CAD), the cardiomyopathy is likely ischemic in etiology. Therefore, a diagnostic strategy for the differentiation between ischemic and non-ischemic cardiomyopathy relies primarily on the evaluation of coronary anatomy for the presence of coronary atherosclerosis. Coronary artery calcium (CAC) is a marker of vascular injury and its presence is pathognomonic for the presence of coronary atherosclerosis. A non-contrast coronary CT, referred to as a CAC scan, allows for the visualization and quantification of calcium in the coronary arteries. The deposit of coronary calcium is highly correlated to the extent and severity of the coronary atherosclerotic burden. As such, CAC-scanning has been used to identify those patients at high risk for obstructive disease. The complete absence of coronary calcium deposits rules out obstructive CAD with near to absolute certainty, implying a non-ischemic etiology to the cardiomyopathy. Of note, Budoff et al found an accuracy of 92% to differentiate between ischemic and non-ischemic cardiomyopathy by using a non-contrast CT scan, obviating the need of invasive procedures in those patients with a negative CAC-scan. Nevertheless, the presence of coronary calcium deposits warrants further testing, since the CAC-score has poor predictive values for obstructive CAD. In this regard calcium scoring may serve as a gatekeeper to CT-based coronary angiography. In contrast to conventional coronary angiography, coronary computed tomography angiography (CCTA) provides a non-invasive alternative for visualizing coronary anatomy. There is a large body of literature on the diagnostic performance of CCTA, unambiguously portraying the same picture of an unequaled high sensitivity and negative predictive value (NPV) of 96% and 94%, respectively. Notably, studies have demonstrated that its accuracy remained high even in patients with tachycardia and/or irregular heart rhythms, recipients of heart transplants, and dilated cardiomyopathy of Reprint requests: ames K. Min, MD, FACC, FSCCT, Dalio Institute of Cardiovascular Imaging, Weill Cornell Medical College and The NewYork-Presbyterian Hospital, 413 East 69th Street, Suite 108, New York, NY 10021; jkm2001@med.cornell.edu J Nucl Cardiol 2015;22:961–7. 1071-3581/$34.00 Copyright 2015 American Society of Nuclear Cardiology.