ABC | Volume 112, Nº1, January 2019

Viewpoint Coronary Computed Tomography Angiography Takes the Center Stage and Here is Why Illan Gottlieb, 1 Marcio Sommer Bittencourt, 2 Carlos Eduardo Rochitte, 3 João L. Cavalcante 4 Casa de Saúde São José – Radiologia, 1 Rio de Janeiro, RJ – Brazil Universidade de São Paulo - Hospital Universitário de São Paulo, 2 São Paulo, SP – Brazil Universidade de São Paulo - Faculdade de Medicina Hospital das Clinicas Instituto do Coração, 3 São Paulo, SP – Brazil Minneapolis Heart Institute at Abbott Northwestern Hospital, 4 Minneapolis, Minnesota – USA Mailing Address : João Cavalcante • Minneapolis Heart Institute at Abbott Northwestern Hospital - 800 E 28 St, Minneapolis, Minnesota, 55407 – USA E-mail: joao.cavalcante@allina.com Manuscript received Ooctober 10, 2018, revised manuscript November 14, 2018, accepted November 14, 2018 Keywords Coronary Artery Disease/diagnostic imaging; Coronary Artery Disease/prevention and control; Coronary Artery Disease/physiopathology; Computed Tomography Angiography; Tomography, X-Ray Computed. DOI: 10.5935/abc.20190003 Max Planck once said that “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” In its beginnings, coronary computed tomography angiography (CCTA) was accused of having too low accuracy for the diagnosis of obstructive coronary artery disease (CAD) to be used in clinical practice. Over the last decade, major technical developments such as larger axial coverage (from 2 cm to 16 cm) and improved temporal resolution, have enabled CCTA to become by far the most accurate non-invasive imaging method for diagnosis of obstructive CAD, with sensitivity and specificity of approximately 95% and 90%, respectively. 1 Then CCTA was burdened with the accusation of exposing patients to radiation doses so high, that warranted some society guidelines to specifically point this out and limit its use. At that time, CCTA exposed patients to doses ranging from 20 to 25 mSV, while triphasic abdomen CT exposed patients to 30 to 40 mSv and scintigraphic myocardial perfusion studies with Thallium used up to 40 mSv. In 2018, radiation exposure from CCTA dropped to well below 5 mSv (most advanced clinical centers use much less), a fraction of the dose used in myocardial perfusion studies with MIBI tetrophosmin. 2 Then the cost-effectiveness wave came with societies rightfully demanding proof that CCTA offered more value at an acceptable cost compared to other imaging modalities, and CCTA once again proved to be more cost-effective than other modalities. 3 Although one hardly finds cost-effectiveness studies comparing nuclear scans with ECG treadmill tests, providing better diagnosis performance is not enough anymore. More recently, this strategy has even been put into challenge in large randomized clinical trials comparing CCTA with the standard of care in the investigation of suspected CAD both in the acute and in the outpatient settings. 4-9 But then CCTA adoption had to face another hurdle. People started demanding that CCTA, a diagnostic study, should demonstrate that it would alter clinical outcomes. Let’s stop here for a moment: a diagnostic study makes the diagnosis. It does not provide the cure, but it could lead to changes in therapy which could eventually lead to improved outcomes. As such, although a CCTA study is not therapeutic, it could guide and inform therapeutic decisions. Measuring blood pressure was never proven to alter clinical outcomes, treatment did. The same with cholesterol measurements, ischemia testing and resting ECG recordings. And yet, everybody has always rightly assumed that diagnosis is a fundamental part of sound medical practice and an angular stone of clinical management. Cardiovascular disease, predominantly in the form of atherosclerosis and hypertension, starts as early as 30 or 40 years, silently progressing across the years to finally kill around one-third of the adult population in the developed world. The conventional strategy “to sit and wait” until patients present with symptoms certainly misses the golden period of the early disease, when treatment is much more efficient and less expensive. Early detection and diagnosis of atherosclerosis using CCTA, might lead to significant downstream changes which could consequently improve outcomes. Despite those initial criticisms and the sceptical view of the use of CCTA in the investigation of suspected CAD, the evidence supporting its clinical use has been steadily increasing over the years. From the initial studies defining the technical feasibility and accuracy of CCTA, followed by the development of techniques aimed at reducing radiation dose and improving imaging quality, CCTA has evolved to be part of the routine armamentarium for the investigation of suspected CAD. More recent evidence has led a wide variety of interpretations, as CCTA lead to an increase in the diagnosis of CAD, accompanied by a 31% reduction in the rate of myocardial infarction, while also being associated with a modest increase in the use of invasive coronary angiography (ICA) and revascularization, according to a recent meta‑analysis. 6 The potential impact of those findings have recently been enhanced by the publication of the 5 years follow up data of the SCOT-HEART trial. 5 The SCOT-HEART study randomized more than 4,000 individuals with symptoms suggestive of CAD to usual care (UC), which includes the use of stress treadmill testing or nuclear perfusion studies, versus UC combined with CCTA. In their initial report in 2015, 9 the authors demonstrated that the use of CCTA led to change in the initial clinical diagnosis in more than one in every four 104