Prospective and Retrospective ECG-gating for CT Coronary Angiography Perform Similarly Accurate at Low Heart Rates

OBJECTIVE: To compare, in patients with suspicion of coronary artery disease (CAD) and low heart rates, image quality, diagnostic performance, and radiation dose values of prospectively and retrospectively electrocardiography (ECG)-gated dual-source computed tomography coronary angiography (CTCA) for the diagnosis of significant coronary stenoses.

METHODS: Two-hundred consecutive patients with heart rates <70bpm were retrospectively enrolled; 100 patients undergoing prospectively ECG-gated CTCA (group 1) and 100 patients undergoing retrospectively-gated CTCA (group 2). Coronary artery segments were assessed for image quality and significant luminal diameter narrowing. Sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and accuracy of both CTCA groups were determined using conventional catheter angiography (CCA) as reference standard. Radiation dose values were calculated.

 RESULTS: Both groups were comparable regarding gender, body weight, cardiovascular risk profile, severity of CAD, mean heart rate, heart rate variability, and Agatston score (all p>0.05). There was no significant difference in the rate of non-assessable coronary segments between group 1 (1.6%, 24/1404) and group 2 (1.4%, 19/1385; p=0.77); non-diagnostic image quality was significantly (p0.05). Mean effective radiation dose of prospectively ECG-gated CTCA (2.2+/-0.4mSv) was significantly (p<0.0001) smaller than that of retrospectively ECG-gated CTCA (8.1+/-0.6mSv).

CONCLUSIONS: Prospectively ECG-gated CTCA yields similar image quality, performs as accurately as retrospectively ECG-gated CTCA in patients having heart rates <70bpm while being associated with a lower mean effective radiation dose.



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  1. Important take home messages for us all! Lower heart rate, is better for dose reduction, but also for image quality (practically, regardless of your scanner type). In patients with low heart rates, good image quality and low radiation dose, do not contradict each other; especially, when using prospective ECG- gating.

  2. See also:

    Comparison of sequential and helical scanning for radiation dose and image quality: results of the Prospective Multicenter Study on Radiation Dose Estimates of Cardiac CT Angiography (PROTECTION) I Study.
    Bischoff B, Hein F, Meyer T, Krebs M, Hadamitzky M, Martinoff S, Sch├Âmig A, Hausleiter J.
    AJR Am J Roentgenol. 2010 Jun;194(6):1495-9.
    PMID: 20489088

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