128-Detector-Row Computed Tomography Coronary Angiography Evaluating Coronary Artery Disease: Who Avoids Cardiac Catheterization?

Angiology Volume 61 Number 2 February 2010 174-178 # 2010 The Author(s) 10.1177/0003319709335513 http://ang.sagepub.com

Olga Lazoura, MD, PhD, Marianna Vlychou MD, PhD, Assistant Professor, Katerina Vassiou, MD, PhD, Lecturer, Christos Rountas, MD, PhD, Fezoulidis Ioannis, MD, PhD, Professor Purpose: To evaluate the prevalence of significant coronary artery disease (CAD) and nondiagnostic studies in patients referred for clinically indicated coronary angiography performed by 128 multidetector computed tomography (MDCT).Methods: We examined patients referred for coronary computed tomography (CT) angiography for the presence of CAD. The analysis included 438 studies classified as normal, with nonsignificant CAD, with significant CAD, or nondiagnostic.Results: Of the 438 cases evaluated, 121 (27.6%) cases were reported as normal, 184 (42%) were classified as nonsignificant CAD, 92 (21%) as significant CAD, and 41 (9.3%) were inconclusive. Therefore,

69.7% of the study population most probably did not require conventional coronary angiography.Conclusion: Among patients referred for computed tomography angiography (CTA) for appropriate indications, 69.6% had either normal coronary arteries or nonobstructive disease. Given the high negative predictive value of coronary CTA, these patients most likely would not require invasive coronary angiography. Selective cardiac CTA may substantially decrease unnecessary diagnostic cardiac catheterizations.

Introduction

However, cardiac catheterization is an invasive and expensive method. A noninvasive imaging modality like coronary CTA, in the setting of appropriate clinical indications, could lead to a significant reduction of unnecessary diagnostic cardiac catheterizations and of the costs and complications associated with this invasive method.6

Noninvasive coronary angiography (CA) performed with multidetector computed tomography (MDCT) has emerged as a new method for the evaluation of the coronary arteries. Multislice CT angiography (CTA) has the advantage of visualizing coronary artery wall morphology, identifying and characterizing plaques.1-4 Many studies have shown the high diagnostic accuracy of multislice CTA compared with conventional CA.2-5 Conventional CA remains the gold standard for the diagnosis of coronary artery stenosis against which other tests are compared.1

From the Departments of Radiology (OL, MV, CR, IF) and Anatomy (KV), Medical School of Thessaly, Greece. Address correspondence to: Olga Lazoura, Mezourlo 41110, Larissa, Greece; e-mail: [email protected].

174

Keywords: coronary artery disease; noninvasive CT angiography; multidetector computed tomography

Materials and Methods The study consisted of 438 patients (335 men, mean age 61 years; 103 women, mean age 65 years) who underwent coronary CTA for evaluation of coronary artery disease (CAD). Patients were divided into 3 groups according to their indication for the CTA. Group 1 included patients referred for the most frequent indication, which was an abnormal, equivocal, or nondiagnostic

128-Detector-Row CT Coronary Angiography Evaluating CAD / Lazour et al 175

stress test. Group 2 included patients who had a low probability of disease and CTA was their first test. Group 3 included patients referred for chest pain or for evaluation of cardiomegaly and congestive heart failure or for evaluation of cardiac aetiology of syncope. The above are considered appropriate indications according to the criteria by the American College of Cardiology (ACC) for CTA,7 and the recent American Heart Association Scientific Statement on Cardiac CT.8 Patients with an established diagnosis of CAD were excluded from the study. The coronary CTA protocol was at the beginning of the examination, a noncontrast localization scan was performed that was used to plan the scan volume. Acquisition delay time was determined by injection of 20 mL test-bolus at 5 mL/s, followed by 50 mL of saline. The peak time of test-bolus enhancement was used as a delay time. A nonionic contrast medium (Iomeron 400 mg iodine/mL; Bracco Altana Pharma, Germany) was infused through an 18-G intravenous antecubital catheter at 5 mL/s. The total contrast dosage for the MDCT CA was adapted to the calculated scan duration (5 mL/s þ 5 mL, total 65-80 mL, infusion rate 5.0 mL/s, saline bolus 50 mL, flow 5 mL/s). Coronary CTA was obtained using the following parameters: 128X0.6 collimation, 0.3 seconds rotation time, pitch of 0.32, 120 kv tube voltage, and 185 reference milliamperes. Patients with heart rates more than 60 bpm and no contraindications for b-blockers use received an additional dose of 100 mg of metoprolol orally 1 hour before the examination. Image acquisition was performed during inspiratory breath-hold. To familiarize the patient with the protocol, breath-holding was practiced before the examination. Studies were acquired in a craniocaudal direction from the level of the carina to just below the diaphragm. Image reconstruction was performed using retrospective electrocardiograph (ECG) gating at the desired cardiac phase. The reconstruction intervals were timed to the phase of the cardiac cycle with the least cardiac motion. Image reconstruction parameters comprised an individually adapted field of view encompassing the heart, a medium soft-tissue convolution kernel (B26f), and a section thickness of 0.6 mm. All CT data sets were transferred to a dedicated workstation (Circulation, Siemens, Germany) and analyzed using curved-multiplanar reformats. Studies were classified as normal (no atherosclerotic plaques seen), nonsignificant CAD (50% stenosis), or nondiagnostic (calcifications of the coronary arteries or motion artefacts). All patients assigned to the significant CAD group and the nondiagnostic study group were referred for cardiac catheterization. In the remaining 2 groups, a cardiac catheterization would not be necessary for diagnosis or treatment. Informed consent was obtained from each participant and the University Hospital ethics committee approved the trial.

Results The clinical characteristics of the study group are shown in Table 1. Smoking was the most frequent risk factor for CAD (73.2%), followed by hypertension (70%), hyperlipidemia (66.2%), and diabetes mellitus (13%). Of the CT angiograms performed, 121 cases (27.6%) were reported to be normal (Figure 1), 184 patients (42%) were classified as having nonobstructive CAD (Figure 2), 93 patients (21%) were defined to have obstructive CAD

176

Angiology / Vol. 61, No. 2, February 2010

Figure 2.

Nonsignificant coronary artery disease.

Figure 4.

Nonevaluable coronary artery segment.

patients. Tables 2 and Figure 5 show the classification of findings according to the indication for CTA. In group 1, 11.9% of studies were reported as normal, 47.7% as nonsignificant CAD, 28.8% as significant CAD, and 11.4% as inconclusive. In group 2, 53.4% of studies were reported as normal, 32.3% as nonsignificant CAD, 8.7% as significant CAD, and 5.5% as inconclusive. In group 3, 14.4% of studies were reported as normal, 47.3% as nonsignificant CAD, 26.3% as significant CAD, and 11.8% as inconclusive. Therefore, in groups 1 and 3, 43.2% and 38.1% of patients were sent to cardiac catheterization, whereas in group 2, 14.2% of patients required catheterization.

Discussion

Figure 3.

Significant coronary artery disease.

(Figure 3a and b) and 41 cases (9.3%) were inconclusive (Figure 4). Group 1 included 201/438 (45.9%) patients, group 2 included 161/438 (36.7%) patients, and group 3 included the remaining 76/438 (17.3%)

Computed tomography techniques allow the visualization of coronary arteries for the evaluation of CAD.7,9,10 The small dimensions of the coronary arteries and their rapid motion make imaging challenging and necessitate improvement of temporal and spatial resolution of CT. 128-MDCT can provide important information on coronary artery lumen morphology and patency. Coronary artery symptomatic lesions with greater than 70% stenosis result in revascularization procedures when evidence of viable, ischemic myocardium is present in that vascular distribution. Patients with lesser degrees of coronary arterial stenosis may be managed with medical therapies. In experienced hands, a high sensitivity and specificity for the detection of hemodynamically significant coronary artery stenosis can be achieved by the new generations of 16-slice to 64-slice CT.3,11-13

128-Detector-Row CT Coronary Angiography Evaluating CAD / Lazour et al 177

Table 2.

Classification of Findings According to the Indication for the Computed Tomography Angiography (CTA)

Normal (n ¼ 121) Nonsignificant CAD* (n ¼ 184) Significant CAD* (n ¼ 92) Inconclusive test (n ¼ 41) Group 1 (n ¼ 201) 24 (11.9%) Group 2 (n ¼ 161) 86 (53.4%) Group 3 (n ¼ 76) 11 (14.4%)

96 (47.7%) 52 (32.3%) 36 (47.3%)

58 (28.8%) 14 (8.7%) 20 (26.3%)

23 (11.4%) 9 (5.5%) 9 (11.8%)

NOTE: CAD ¼ coronary artery disease.

Figure 5. Severity of coronary artery disease (CAD) according to the indication for computed tomography angiography (CTA).

Recent studies show that sensitivities ranging from 83% to 99% and specificities ranging from 93% to 98% can be achieved at experienced centers. A very high negative predictive value (95% to 100%) is uniformly found.14 In the current study, 30.3% of patients without a known history of CAD, referred for cardiac CTA (cCTA), were found to have either significant disease or inconclusive tests. According to these results, cardiac catheterization would be required in 30.3% of patients, while 69.7% would most probably avoid catheterization. Our results are in agreement with others,1 who found 27% of patients requiring cardiac catheterization in an outpatient environment. In patients with low to intermediate probability of CAD, the lower percentage of cardiac catheterizations required (14.2%) was observed, due both to lower percentage of significant stenosis (8.7%) and nondiagnostic studies (5.5%) reported. In the past, many patients with borderline noninvasive testing were referred directly for cardiac

catheterization. This strategy is associated with a small, but measurable, complication rate, in addition to increased costs.1 A feasible noninvasive coronary imaging modality like CTA will help avoid unnecessary diagnostic cardiac catheterizations and will significantly reduce the costs and complications associated with this invasive procedure.6 Selective cCTA has potential cost benefits that are not compromised by nondiagnostic studies, because the prevalence of nondiagnostic CTA studies is low (9.3% in this study, and 0% to 11% in recent studies).15 A survey by the Society for Cardiac Angiography and Interventions indicated that the total risk of CA for all major complications (including mortality) is approximately 2%.16 The most common risk is due to the catheter advancement that can dislodge aortic plaque, which can dissect the artery or embolize, causing myocardial infarction or stroke.1 The arterial puncture can cause vessel damage. Serious bleeding (usually retroperitoneal) is a rare but significant complication.16 These risks are not present using intravenous access during CTA. The radiation dose is higher during CTA than CA (10 mSv vs 2-5 mSv), although the exact consequences of this difference are currently unknown. Both coronary CTA and conventional CA have risks associated with injection of iodinated contrast material, which include potential renal toxicity, and allergic reactions, including anaphylaxis. We use 65 to 80 mL of contrast material to evaluate CTA in this cohort, approximately the same dose that is used during invasive CA to get similar data (coronary arteries plus left ventriculogram).1 Coronary CTA has limitations and should not be expected to widely replace diagnostic CA. Spatial resolution limits the ability of CTA to provide exact, quantitative measures of stenosis severity. Patients with arrhythmias, for example, atrial fibrillation, as well as patients with contraindications to iodinated contrast agents cannot be examined by CTA. In our study, 9.3% of all patients had nondiagnostic examinations. Impaired image quality, due to dense calcifications and/or multiple image artefacts including

178

Angiology / Vol. 61, No. 2, February 2010

coronary artery motion and breathing artefacts, also limits the clinical use of noninvasive CA.17 Coronary CTA can noninvasively image coronary artery luminal stenoses, as well as plaques that may become responsible for an acute coronary syndrome.12,18,19 The main area of interest is currently the use of CT to rule out stenosis in patients with possible CAD but a rather low pretest likelihood of significant disease.14,20 Patients whose clinical presentation suggests a very high likelihood of significant CAD (eg, with absolutely typical chest pain and an unambiguously positive stress test) will most likely not benefit from noninvasive CT angiography. However, targeting the test to patients without a high pretest likelihood of coronary stenosis appears justified as a safe and possibly cost-efficient option. The consistently high negative predictive value will help ensure that the vast majority of patients with CTA studies diagnosed as nonsignificant CAD will not have severe underlying CAD and invasive angiography will not be necessary.

8.

9. 10.

11.

12.

References 1. Budoff MJ, Gopal A, Gul KM, Mao SS, Fischer H, Oudiz RJ. Prevalence of obstructive coronary artery disease in an outpatient cardiac CT angiography environment. Int J Cardiol. 2008;129(1):32-36. 2. Mollet NR, Cademartiri F, Nieman K, et al. Noninvasive assessment of coronary plaque burden using multislice computed tomography. Am J Cardiol. 2005;95(10):1165-1169. 3. Raff GL, Gallagher MJ, O’Neill WW, Goldstein JA. Diagnostic accuracy of noninvasive coronary angiography using 64-slice spiral computed tomography. J Am Coll Cardiol. 2005;46(3):552-557. 4. Leber AW, Knez A, Becker A, et al. Accuracy of multidetector spiral computed tomography in identifying and differentiating the composition of coronary atherosclerotic plaques: a comparative study with intracoronary ultrasound. J Am Coll Cardiol. 2004;43(7):1241-1247. 5. Leschka S, Alkadhi H, Plass A, et al. Accuracy of MSCT coronary angiography with 64-slice technology: first experience. Eur Heart J. 2005;26(15):1482-1487. 6. Budoff MJ, Lu B, Shinbane JS, et al. Methodology for improved detection of coronary stenoses with computed tomographic angiography. Am Heart J. 2004;148(6):1085-1090. 7. Hendel RC, Patel MR, Kramer CM, et al. ACCF/ACR/ SCCT/SCMR/ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for cardiac computed tomography and cardiac magnetic resonance imaging: a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group, American College of Radiology, Society of Cardiovascular Computed Tomography, Society for

13.

14. 15.

16.

17.

18.

19.

20.

Cardiovascular Magnetic Resonance, American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography and Interventions, and Society of Interventional Radiology. J Am Coll Cardiol. 2006;48(7):1475-1497. Budoff MJ, Achenbach S, Blumenthal RS, et al. Assessment of coronary artery disease by cardiac computed tomography: a scientific statement from the American Heart Association Committee on Cardiovascular Imaging and Intervention, Council on Cardiovascular Radiology and Intervention, and Committee on Cardiac Imaging, Council on Clinical Cardiology. Circulation. 2006;114(16):1761-1791. Becker CR. Coronary CT angiography in symptomatic patients. Eur Radiol. 2005;15(suppl 2):B33-B41. Butler J, Shapiro M, Reiber J, et al. Extent and distribution of coronary artery disease: a comparative study of invasive versus noninvasive angiography with computed angiography. Am Heart J. 2007;153(3):378-384. Nikolaou K, Knez A, Rist C, et al. Accuracy of 64-MDCT in the diagnosis of ischemic heart disease. AJR Am J Roentgenol. 2006;187(1):111-117. Muhlenbruch G, Seyfarth T, Soo CS, Pregalathan N, Mahnken AH. Diagnostic value of 64-slice multi-detector row cardiac CTA in symptomatic patients. Eur Radiol. 2007;17(3):603-609. Gaemperli O, Schepis T, Koepfli P, et al. Accuracy of 64slice CT angiography for the detection of functionally relevant coronary stenoses as assessed with myocardial perfusion SPECT. Eur J Nucl Med Mol Imaging. 2007;34(8):1162-1171. Achenbach S. Computed tomography coronary angiography. J Am Coll Cardiol. 2006;48(10):1919-1928. Budoff MJ, Achenbach S, Duerinckx A. Clinical utility of computed tomography and magnetic resonance techniques for noninvasive coronary angiography. J Am Coll Cardiol. 2003;42(11):1867-1878. Noto TJ, Jr., Johnson LW, Krone R, et al. Cardiac catheterization 1990: a report of the Registry of the Society for Cardiac Angiography and Interventions (SCA&I). Cathet Cardiovasc Diagn. 1991;24(2):75-83. Budoff MJ. Noninvasive coronary angiography using computed tomography. Expert Rev Cardiovasc Ther. 2005;3(1):123-132. Finet G, Ohayon J, Rioufol G, et al. Morphological and biomechanical aspects of vulnerable coronary plaque. Arch Mal Coeur Vaiss. 2007;100(6-7):547-553. Ueno K, Anzai T, Jinzaki M, et al. Diagnostic capacity of 64-slice multidetector computed tomography for acute coronary syndrome in patients presenting with acute chest pain. Cardiology. 2008;112(3):211-218. Schlosser T, Mohrs OK, Magedanz A, et al. Noninvasive coronary angiography using 64-detector-row computed tomography in patients with a low to moderate pretest probability of significant coronary artery disease. Acta Radiol. 2007;48(3):300-307.

For reprints and permissions queries, please visit SAGE’s Web site at http://www.sagepub.com/journalsPermissions.nav.