Lowering heart rate with an optimised breathing protocol for prospectively ECG-triggered CT coronary angiography.

OBJECTIVES: The aim was to prospectively characterise the effect of the level of breath-hold on heart rate in CT coronary angiography (CTCA) with prospective electrocardiogram (ECG) triggering and its impact on coronary artery attenuation. METHODS: 260 patients (86 women; mean age 59 ± 11 years) underwent 64-slice CTCA using prospective ECG triggering. Prior to CTCA, heart rates were recorded during 15 s of breath-hold at three different levels of inspiration (normal, intermediate and deep). The inspiration level with the lowest heart rate was chosen for actual CTCA scanning. Coronary artery attenuation was measured, and the presence of backflow of contrast material into the inferior vena cava (as an indicator of increased intrathoracic pressure) was recorded. RESULTS: The mean heart rate at breath-hold was significantly different for the three inspiration levels (normal, 60 ± 8 bpm; intermediate, 59 ± 8 bpm; deep, 57 ± 7 bpm; p<0.001). The maximum heart rate reduction in each patient at breath-hold averaged 5.3 ± 5.1 bpm, and was observed at a normal inspiration depth in 23 (9%) patients, at an intermediate inspiration depth in 102 (39%) patients and at deep inspiration in 135 (52%) patients. Overall, there was no association between the level of breath-hold and coronary vessel attenuation (p-value was not significant). However, the backflow of contrast material into the inferior vena cava (n = 26) was found predominantly at deep inspiration levels (p<0.001), and, when it occurred, it was associated with reduced coronary attenuation compared with patients with no backflow (p<0.05). CONCLUSION: The breath-hold level to best reduce heart rate for CTCA should be individually assessed prior to scanning because a mean heart rate reduction of 5 bpm can be achieved.

First head-to-head comparison of effective radiation dose from low-dose 64-slice CT with prospective ECG-triggering versus invasive coronary angiography.

BACKGROUND: Reduction of radiation burden of multidetector computed tomography coronary angiography (CTCA) has remained an important task. OBJECTIVE: To compare effective radiation dose of low-dose 64-slice CTCA using prospective ECG-triggering versus diagnostic invasive coronary angiography (CA). METHODS: 42 patients referred for elective invasive CA owing to suspected coronary artery disease (CAD) were prospectively enrolled to undergo a low-dose CTCA without calcium scoring within the same day before CA. Dose-area product of diagnostic invasive CA and dose-length product of CTCA were measured, converted into effective radiation dose and compared using Mann-Whitney U tests. In addition, accuracy of CTCA to detect CAD (coronary artery narrowing > or =50%) was assessed using invasive CA as standard of reference. On an intention-to-diagnose basis all non-evaluative vessels were included in the analysis and censored as positive. RESULTS: The estimated mean effective radiation dose was 8.5 (4.4) mSv (range 1.4-20.5 mSv) for diagnostic invasive CA, and 2.1 (0.7) mSv (range 1.0-3.3 mSv) for CTCA (p<0.001). 19 patients (42.9%) had no CAD by invasive CA. 40 (95.2%) patients have been correctly classified as having CAD (23/23) or no CAD (17/19). Over 97% (551/567) of segments were evaluable. Vessel-based analysis revealed sensitivity, specificity, positive and negative predictive value of 94.2% (CI 0.8% to 1.0%), 94.8% (CI 09% to 1.0%), 89.0% (CI 0.8% to 1.0%), 97.4% (CI 09% to 1.0%) and an accuracy of 94.6%. CONCLUSIONS: Low dose CTCA allows evaluation of CAD with high accuracy, but delivers a significantly less effective radiation dose to patients compared to diagnostic invasive CA.

Impact of vessel attenuation on quantitative coronary angiography with 64-slice CT.

The aim of the study was to determine the impact of vessel attenuation on quantitative 64-slice computed tomography coronary angiography (CTCA). CTCA and invasive quantitative coronary angiography (QCA) were performed in 100 consecutive patients (42 women, 58 men; mean age 64.4+/-9.4 years; age range 39-87 years). In QCA, stenoses were quantified with dedicated software, whereas in CTCA, stenosis severity was assessed with an electronic caliper tool: stenoses were graded in 10% steps and assigned as either a calcified or non-calcified lesion. Vessel attenuation in the left main (LMA) and the proximal right coronary artery (RCA) were measured and correlated with differences in quantifications of stenosis grade between QCA and CTCA. A total of 113 coronary stenoses were detected by both methods (94 significant and 19 non-significant); 52 stenoses were rated as non-calcified and 61 as calcified lesions. The mean difference between QCA and quantitative CTCA grading was 5.1+/-16.9% (range -27 to 46%) overall; 1.9+/-14.2% (range -27 to 38%) for non-calcified lesions and 7.8+/-18.6% (range -23 to 46%) for calcified lesions. Mean vessel attenuation was 362+/-76 HU (range 191-584 HU) in the LMA and 333+/-81 HU (range 162-564 HU) in the RCA. Attenuation did not significantly correlate with differences in QCA and CTCA gradings, neither overall nor for calcified or non-calcified lesions. When 64-slice CTCA is used, coronary vessel attenuation had no impact on the quantitative grading of stenoses.

Multislice computed tomography coronary angiography for risk stratification in patients with an intermediate pretest likelihood.

OBJECTIVES: To assess whether multislice computed tomography coronary angiography (MSCTA) may be useful for risk stratification of patients with suspected coronary artery disease (CAD) at intermediate pretest likelihood according to Diamond and Forrester. DESIGN AND PATIENTS: MSCTA images were evaluated for the presence of significant CAD in 316 patients with suspected CAD (60% male, average (SD) age 57 (11) years) and an intermediate pretest likelihood according to Diamond and Forrester. Patients were followed up to determine the occurrence of an event. MAIN OUTCOME MEASURES: A combined end point of all-cause mortality, non-fatal infarction and unstable angina requiring revascularisation. RESULTS: Significant CAD was seen in 89 patients (28%), whereas normal MSCTA or non-significant CAD was seen in the remaining 227 (72%) patients. During follow-up (median 621 days (25-75th centile 408-835) an event occurred in 13 patients (4.8%). The annualised event rate was 0.8% in patients with normal MSCT, 2.2% in patients with non-significant CAD and 6.5% in patients with significant CAD. Moreover, MSCTA remained a significant predictor (p<0.05) of events after multivariate correction (hazard ratio = 3.460 (95% CI 1.142 to 10.480). CONCLUSIONS: The results suggest that in patients with an intermediate pretest likelihood, MSCTA is highly effective in re-stratifying patients into either a low or high post-test risk group. These results further emphasise the usefulness of non-invasive imaging with MSCTA in this patient population.