ABC | Volume 113, Nº4, October 2019

Review Article Evaluation of Myocardial Perfusion by Computed Tomography - Principles, Technical Background and Recommendations Tiago Augusto Magalhães, 1,2 Roberto Caldeira Cury, 3 Rodrigo Julio Cerci, 4 José Rodrigues Parga Filho, 5 Ilan Gottlieb, 6 Marcelo Souto Nacif, 7,8 Ibraim Masciarelli Pinto, 9 Carlos Eduardo Rochitte, 5 Fabio Vilas-Boas, 10 Paulo R. Schvartzman 11 Universidade Federal do Paraná - Complexo Hospital de Clínicas (CHC) –Universidade Federal do Paraná, 1 Curitiba, PR – Brazil Hospital do Coração (HCor) - Division of cardiovascular CT/MR, 2 São Paulo, SP – Brazil Diagnósticos da América SA, 3 São Paulo, SP – Brazil Quanta Diagnóstico e Terapia, 4 Curitiba, PR – Brazil Instituto do Coração (InCor) - Universidade de São Paulo - Division of Cardiovascular CT/MR, 5 São Paulo, SP – Brazil Casa de Saúde São José – Division of Radiology, 6 Rio de Janeiro, RJ – Brazil Complexo Hospitalar de Niterói - Division of Radiology, 7 Niterói, RJ – Brazil Hospital Universitário Antônio Pedro, 8 Niterói, RJ – Brazil Instituto Dante Pazzanese de Cardiologia, 9 São Paulo, SP – Brazil Hospital da Bahia, 10 Salvador, BA – Brazil Hospital Moinhos de Vento - Division of Cardiovascular CT/MR, 11 Porto Alegre, RS – Brazil Keywords Computed Tomography Angiography/methods; Myocardial Perfusion Imaging/methods; Coronary Artery Disease; Dipyridamole; Adenosine; Vasodilatation. Mailing Address: Tiago Augusto Magalhães • Complexo Hospital de Clínicas da Universidade Federal do Paraná (CHC‑UFPR) - Cardiovascular CT/MR - Rua General Carneiro, 181, unidade de diagnóstico por imagem. Postal Code 80060-900, Curitiba, PR – Brazil E-mail: tiaugusto@gmail.com Manuscript received September 19, 2018, revised manuscript February 25, 2019, accepted March 20, 2019 DOI: 10.5935/abc.20190217 Abstract Coronary computed tomography angiography (CCTA) has gained a prominent role in the evaluation of coronary artery disease. However, its anatomical nature does not allow the evaluation of the functional repercussion of coronary obstructions. It has been made possible to evaluate Myocardial computed tomography perfusion (Myocardial CTP) recently, based on myocardial contrast changes related to coronary stenoses. Several studies have validated this technique against the anatomical reference method (cardiac catheterization) and other functional methods, including myocardial perfusion scintigraphy and fractional flow reserve. The Myocardial CTP is performed in conjunction with the CCTA, a combined analysis of anatomy and function. The stress phase (with assessment of myocardial perfusion) can be performed before or after the resting phase (assessment of resting perfusion and coronary arteries), and different acquisition parameters are proposed according to the protocol and type of equipment used. Stressors used are based on coronary vasodilation (e.g. dipyridamole, adenosine). Image interpretation, similar to other perfusion assessment methods, is based on the identification and quantification of myocardial perfusion defects. The integration of both perfusion and anatomical findings is fundamental for the examination interpretation algorithm, allowing to define if the stenoses identified are hemodynamically significant and may be related to myocardial ischemia. Introduction Coronary computed tomography angiography (CCTA) was introduced in clinical practice in the end of the last century to promote noninvasive visualization of coronary arteries. Its use proved it an appropriate option for the evaluation of coronary artery disease. 1-4 Technological improvements of the equipment in recent years have allowed its application in different clinical conditions (emergency room chest pain evaluation, investigation in patients with conflicting diagnostic tests, among others). It is noteworthy that in all these conditions the background for its use rests on its high negative predictive power, making the presence of obstructive disease in the face of a negative test very unlikely. 1,2,5-8 Hence the need for invasive coronary angiography in a large number of individuals with clinical presentation or results of noninvasive tests compatible with coronary artery disease, but without obstructive coronary disease, shows a favorable cost-benefit profile using CCTA in these clinical scenario. 1,2,5,8-10 On the other hand, the routine use of CT scan could result in a greater number of invasive procedures, since it would show lesions without clinical manifestation and that would be submitted to interventional treatment. 11 This limitation would stem mainly from the fact that the positive predictive value of Coronary artery CT is not as high as its negative predictive value, as it is also somewhat limited in characterizing plaques of moderate obstruction, especially when compared to other diagnostic tests. 1,4,6 This is relevant because the correct management of patients with coronary artery obstruction requires the characterization of the functional impact of stenosis, given that atheromas that do not cause flow reduction should receive maximum clinical treatment, whereas plaques that impact myocardial perfusion could be treated with surgical or percutaneous revascularization even if it promotes a moderate decrease in vessel lumen. 12-15 Given the importance of myocardial ischemia detection, either by echocardiography, magnetic resonance imaging, myocardial scintigraphy, or by invasive examinations that include Fractional Flow Reserve (FFR) analysis, 4,15-18 the use of hybrid images, combining anatomical and functional findings, has become extremely desirable. 4 However, this involves 758