Computed tomography angiography of coronary artery bypass grafts: robustness in emergency and clinical routine settings

BACKGROUND

There is a high probability for presence of irregular heart rates and artifacts in patients with previous coronary artery bypass graft (CABG) surgery. Previously reported diagnostic performance of ECG-gated 64-slice dual-source computer tomography angiography (CTA) in this patient group is based on pre-selection for normal heart rate and routine clinical setting.

PURPOSE

To investigate image quality and diagnostic performance of CTA in patients with previous CABG surgery in various clinical settings.

MATERIAL AND METHODS

Fifty-six non-selected, consecutive patients (110 grafts, 44 arterial, 66 venous) with previous CABG surgery were prospectively examined using a dual-source 64-slice CT (Siemens Definition, Forchheim, Germany) without utilization of CT-related pharmaceutical heart rate control. Patients were stratified according to the clinical setting: planned redo-cardiac surgery; emergency CTA within 30 days after CABG surgery; routine follow-up after CABG surgery. A reference standard was available for 30 patients (53.6%; 67/110 grafts). Image quality, artifacts, and graft patency were independently assessed by two observers.

RESULTS

All CTAs were diagnostic despite the presence of irregular heart rhythm (25% of cases) and artifacts (72.7% of grafts). CTA was accurate in all patient groups in assessing graft patency (97.9% sensitivity; 100% specificity; 98.5% accuracy) but artifacts decreased diagnostic performance for stenosis detection (60% sensitivity; 88.6% specificity; 84.1% accuracy). Arterial grafts exhibited more surgical clip artifacts compared to venous grafts, which predominantly showed motion artifacts. Overall diagnostic quality was rated excellent in 70.9%/56.4%, good in 23.4%/39.1%, and sufficient in 5.5%/4.5% by each observer, respectively. CTA detected acute findings in 10 cases (graft bleeding, graft occlusion, pericardial hematoma, sternal instability with retrosternal abscess formation, pericardial effusion, left ventricle thrombus) in the emergency group; seven cases required surgical revision.

CONCLUSION

Dual-source CTA is a robust and accurate method for assessment of graft patency and detection of relevant extra-cardiac pathologies in a non-selected patient population after CABG surgery in routine as well as emergency clinical settings. Artifacts caused by irregular heart rhythm or surgical clips do not impair graft patency evaluation but limit stenosis assessment.

Chamber dimensions and functional assessment with coronary computed tomographic angiography as compared to echocardiography using American Society of Echocardiography guidelines

Background:

The correlation between normal cardiac chamber linear dimensions measured during retrospective coronary computed tomographic angiography as compared to transthoracic echocardiography using the American Society of Echocardiography guidelines is not well established.

Methods:

We performed a review from January 2005 to July 2011 to identify subjects with retrospective electrocardiogram-gated coronary computed tomographic angiography scans for chest pain and transthoracic echocardiography with normal cardiac structures performed within 90 days. Dimensions were manually calculated in both imaging modalities in accordance with the American Society of Echocardiography published guidelines. Left ventricular ejection fraction was calculated on echocardiography manually using the Simpson’s formula and by coronary computed tomographic angiography using the end-systolic and end-diastolic volumes.

Results:

We reviewed 532 studies, rejected 412 and had 120 cases for review with a median time between studies of 7 days (interquartile range (IQR_25,75) = 0–22 days) with no correlation between the measurements made by coronary computed tomographic angiography and transthoracic echocardiography using Bland–Altman analysis. We generated coronary computed tomographic angiography cardiac dimension reference ranges for both genders for our population.

Conclusion:

Our findings represent a step towards generating cardiac chamber dimensions’ reference ranges for coronary computed tomographic angiography as compared to transthoracic echocardiography in patients with normal cardiac morphology and function using the American Society of Echocardiography guideline measurements that are commonly used by cardiologists.

[Oral versus intravenous beta-blockers for computed tomography coronary angiography? A randomized controlled trial]

OBJECTIVES

To determine whether the time employed in the radiological management of outpatients undergoing computed tomography (CT) coronary angiography varies in function of whether oral or intravenous beta-blockers are administered.

MATERIAL AND METHODS

This was a prospective, analytical, randomized controlled trial. A total of 40 patients with heart rates greater than 65 beats per minute were randomly assigned to one of two groups. Patients in group 1 were administered oral beta-blockers and patients in group 2 were administered intravenous beta-blockers. We measured the overall time from entry to the radiology department to exit from the CT examination room. We also measured heart rate, blood pressure, and the number of conclusive studies.

RESULTS

The median (interquartile range) overall time was 120 (100-150) minutes in the 19 patients who received oral beta-blockers compared to 35 (27.5-67.5) minutes in the 21 patients who received intravenous beta-blockers (p<0.001). The median time that patients were in the CT examination room was 10 (6-15) minutes in Group 1 and 10 (9-20) minutes in Group 2 (p = 0.57). The decrease in mean arterial pressure was 10 mmHg after the administration of intravenous beta-blockers compared to 3.3 mmHg after the administration of oral beta-blockers (p = 0.01). No significant differences were found in the diagnostic quality of the examinations.

CONCLUSIONS

The time employed in the radiological management of patients undergoing CT coronary angiography is significantly lower when beta-blockers are administered intravenously. There was no difference in the time patients were in the CT examination room or in the diagnostic quality of the examinations.