Tanja Meyer

Prognostic value of coronary computed tomographic angiography for prediction of cardiac events in patients with suspected coronary artery disease.

OBJECTIVES We assessed the rate of cardiac events after detection or exclusion of obstructive coronary artery disease (CAD) by coronary computed tomography angiography (CCTA). BACKGROUND Several studies have demonstrated a high diagnostic accuracy of CCTA for detection of obstructive CAD compared with invasive angiography, but data regarding the clinical prognostic value of CCTA are limited. METHODS In all, 1,256 consecutive patients with suspected CAD undergoing 64-slice CCTA in our institution between October 2004 and September 2006 were observed prospectively for the occurrence of severe cardiac events (cardiac death, myocardial infarction, or unstable angina requiring hospitalization: primary study end point) and all cardiac events (additionally including revascularization >90 days after CCTA). The observed rate of all cardiac events was compared with the event rate predicted by the Framingham risk score. Obstructive CAD was defined as > or = 50% diameter stenosis in any coronary artery. RESULTS During a median follow-up of 18 months (interquartile range 14 to 25 months), the overall rates of severe and all cardiac events were 0.6% and 1.8%, respectively. In 802 patients without obstructive CAD, there were 4 cardiac events, of which 1 was severe, whereas in 348 patients with obstructive CAD, there were 17 cardiac events, of which 5 were severe. The difference between the 2 groups was highly significant both for severe events (odds ratio: 17.3, 95% confidence interval: 3.6 to 82.5) and for all cardiac events (odds ratio: 16.1, 95% confidence interval: 7.2 to 36.0; both p < 0.001). The rate of all cardiac events in patients without obstructive CAD was significantly lower than predicted by the Framingham risk score (p = 0.01). CONCLUSIONS In patients with suspected CAD, CCTA has a significant prognostic impact on the prediction of cardiac events for the subsequent 18 months. The exclusion of obstructive CAD by CCTA identifies a patient population with an event risk lower than predicted by conventional risk factors.

Impact of a Reduced Tube Voltage on CT Angiography and Radiation Dose: Results of the PROTECTION I Study

OBJECTIVES The aim of this study was to determine the impact of a reduced 100-kV tube voltage on image quality and radiation exposure in a pre-defined subgroup analysis of the international, multicenter radiation dose survey PROTECTION I (Prospective Multicenter Study on RadiaTion Dose Estimates Of Cardiac CT AngIOgraphy I) study. BACKGROUND Cardiac computed tomography angiography (CCTA) has become a frequently used diagnostic tool in clinical practice. Despite continually improving CT technology, there remain concerns regarding the associated radiation exposure. A reduced tube voltage of 100 kV has been proposed as an effective means for dose reduction in nonobese patients. METHODS The study assessed the relevant radiation dose parameters as well as quantitative and qualitative diagnostic image quality data in a subgroup of 321 patients (100 kV: 82 patients; 120 kV: 239 patients), who were scanned at study sites that applied a 100-kV tube voltage in at least 1 patient. Diagnostic image quality was assessed by an experienced CCTA investigator with a 4-point score (1: nondiagnostic to 4: excellent image quality). Effective radiation dose was estimated from the dose-length-product of each CCTA study. RESULTS The use of the 100-kV scan protocol was associated with 53% reduction in CCTA median radiation dose estimates, when compared with the conventional 120-kV scan protocol (p < 0.001). Although image noise significantly increased by 26.3% with 100 kV, signal- as well as contrast-to-noise ratios also increased by 7.9% (p = 0.254) and 10.8% (p = 0.027), respectively. Reduction of tube voltage did not impair diagnostic image quality (median diagnostic score: 3.5 [3.25 to 3.75] vs. 3.5 [3.0 to 3.75] for 100 kV vs. 120 kV; p = 0.22). CONCLUSIONS In this nonrandomized PROTECTION I dose survey, reducing the CCTA tube voltage to 100 kV in nonobese patients is associated with a significant reduction in radiation exposure while maintaining diagnostic image quality. Thus, the 100-kV scan technique should be considered for CCTA dose reduction in adequately selected patients.

Prognostic value of coronary computed tomographic angiography in comparison with calcium scoring and clinical risk scores.

Background—Several studies have demonstrated a high accuracy of coronary computed tomography angiography (CCTA) for detection of obstructive coronary artery disease (CAD), whereas some studies have also shown a good prediction of cardiac events. However, it remains to be proven whether CCTA is better predictive of events than conventional risk scores or calcium scoring. Therefore, we compared CCTA with calcium scoring and clinical risk scores for the ability to predict cardiac events. Methods and Results—Patients (n=2223) with suspected CAD undergoing CCTA were followed up for a median of 28 months. The end point was the occurrence of cardiac events (cardiac death, nonfatal myocardial infarction, unstable angina requiring hospitalization, and coronary revascularization later than 90 days after CCTA). Patients with obstructive CAD had a significantly higher event rate (2.9% per year; 95% confidence interval, 2.1 to 4.0) than those without obstructive CAD, having an event rate 0.3% per year (95% confidence interval, 0.1 to 0.5; hazard ratio, 13.5; 95% confidence interval, 6.7 to 27.2; P<0.001). CCTA had significant incremental predictive value when compared with calcium scoring, both with scores assessing the degree of stenosis (P<0.001) and with scores assessing the number of diseased coronary segments (P=0.027). Conclusions—In patients with suspected CAD, CCTA not only detects coronary stenosis but also improves prediction of cardiac events over and above conventional risk scores and calcium scoring. This may result in a reclassification of cardiovascular risk in a substantial proportion of patients.

Feasibility of dual-source cardiac CT angiography with high-pitch scan protocols

BACKGROUND Cardiac CT angiography (CCTA) has become a frequently used diagnostic tool in clinical practice, but concern remains about the radiation exposure. Because of the second x-ray acquisition system, dual-source CT systems might allow for high-pitch CT data acquisition and thus for examination of the whole heart during a single heart beat, with the potential for radiation dose reduction. OBJECTIVE We assessed the feasibility of a high-pitch scan mode with a dual-source CT system. METHODS High-pitch modes were used in patients undergoing CCTA with a dual-source CT system. Diagnostic image quality for cardiac structures and coronary arteries was assessed. Radiation dose was estimated from the scanner-generated dose-length product (DLP). RESULTS CCTA was performed in 14 patients during a single heart beat applying a pitch value of 3.4. Mean heart rate during examination was 56.4+/-8.1 beats/min. Diagnostic image quality for the assessment of larger cardiac structures was obtained in all patients, whereas diagnostic image quality could be achieved in 82% of all coronary segments. With a mean DLP of 145+/-47 mGy x cm, the resulting estimated radiation dose was 2.0+/-0.7 mSv. CONCLUSIONS This proof-of-concept study shows the ability of dual-source CT scanners to scan the whole heart during one single heart beat at low radiation dose.

Prognostic Value of Coronary Computed Tomographic Angiography in Diabetic Patients without Known Coronary Artery Disease

OBJECTIVE Diabetic patients have a high prevalence of coronary artery disease (CAD), but timely diagnosis of CAD remains challenging. We assessed the ability of coronary computed tomography angiography (CCTA) to detect CAD in diabetic patients and to predict subsequent cardiac events. RESEARCH DESIGN AND METHODS We analyzed 140 diabetic patients without known CAD undergoing CCTA; 1,782 patients without diabetes were used as a control group. Besides calcium scoring and the degree of the most severe stenosis, the atherosclerotic burden score counting the number of segments having either a nonstenotic plaque or a stenosis was recorded. The primary end point was a composite of hard cardiac events defined as all-cause death, nonfatal myocardial infarction, or unstable angina requiring hospitalization. RESULTS During a mean follow-up of 33 months, there were seven events in the diabetic group and 24 events in the control group. The best predictor in diabetic patients was the atherosclerotic burden score: the annual event rate ranged from 0.5% for patients with <5 lesions to 9.6% for patients with >9 lesions, resulting in a hazard ratio (HR) of 1.3 (95% CI 1.1–1.7) for each additional lesion (P = 0.005). For comparison, in nondiabetic patients the annual event rate ranged from 0.3 to 2.2%, respectively, resulting in an HR of 1.2 (95% CI 1.1–1.3, P < 0.001). The atherosclerotic burden score improved the prognostic value of conventional risk factors significantly (P < 0.001). CONCLUSIONS In diabetic patients without known CAD, CCTA can identify a patient group at particularly high risk for subsequent hard cardiac events.

Prognostic value of coronary computed tomographic angiography in asymptomatic patients.

To assess the value of coronary computed tomographic angiography (CCTA) in the prediction of cardiac events in asymptomatic patients, 451 consecutive asymptomatic patients who underwent CCTA from December 2003 to November 2007 were retrospectively analyzed. The primary end point of the study was the occurrence of cardiac events, defined as cardiac death, nonfatal myocardial infarction, unstable angina requiring hospitalization, and late revascularization (>90 days after CCTA) during a median follow-up period of 27.5 months. Secondary end points were the prevalence of nonobstructive coronary lesions and the number of patients reclassified regarding their cardiovascular risk. Two hundred twenty-nine patients (54%) had nonobstructive coronary lesions, and 107 patients (24%) obstructive coronary artery disease. During follow-up, there were 2 cases of unstable angina and 8 revascularizations for stable angina. Patients with obstructive coronary artery disease had a significantly higher event rate than those without obstructive CAD (risk ratio 13.9, 95% confidence interval 4.0 to 48.0). In 217 patients (48%), the clinically assessed cardiovascular risk could be reclassified by CCTA from intermediate or high to low risk. In conclusion, although the event rate was low in asymptomatic patients, CCTA could reliably predict further cardiac events and could reclassify 2/3 of patients regarding their cardiovascular risk.

Cardiovascular risk assessment based on the quantification of coronary calcium in contrast-enhanced coronary computed tomography angiography

AIMS The extent of coronary artery calcification (CAC) has been shown to be a strong and independent predictor for cardiovascular events. Usually, CAC scoring is performed in non-contrast-enhanced computed tomography (CT) examinations. The ability and accuracy of cardiovascular risk classification according to the degree of CAC determined in contrast-enhanced coronary CT angiography (CCTA) has not been investigated so far. The aim of this analysis was to develop and validate a method for CAC risk classification in CCTA. METHODS AND RESULTS In a test series of 100 patients who underwent both non-enhanced CAC scoring and CCTA, we developed a method to assess the extent of coronary calcification and the associated cardiovascular risk category in CCTA. The accuracy of the developed approach of CAC assessment in CCTA was determined in 500 consecutive patients in comparison to CAC scoring in the non-enhanced scan. CAC scoring results in the non-enhanced scan and CCTA scan showed a high correlation (r = 0.954; P < 0.001). CAC quantification in CCTA correctly identified 98% of patients without CAC as shown in the non-enhanced scan (184 of 188 patients). When compared with non-enhanced CAC scoring, CAC scoring in CCTA grouped more than 95% of high-risk patients correctly into the same risk category according to the 75th age- and gender-specific percentiles or the absolute calcium scores. CONCLUSION Assessing cardiovascular risk associated with CAC is feasible and accurate in contrast-enhanced CCTA. This new technique may allow for reducing the radiation exposure of coronary CT studies while maintaining an accurate cardiovascular risk assessment, because the addition of non-enhanced scans to CCTA becomes unnecessary for comprehensive coronary CT studies.