P040 Effect on Heart Rate Reduction of Prolonged Apnea Technique in Coronary CTA with a 320-Detector-Row Scanner

Abstract

Objective: To evaluate the effectiveness of prolonged apnea technique in lowering heart rate for coronary CTA performed with a 320-detector-row scanner. Methods: With background history of chest pain or positive treadmill results, a total of 307 patients for coronary CTA between March and June 2010 were included retrospectively. The patients’ heart rates (HRs) were sampled at three different timings: upon their arrival at our unit, pre-imaging after oral beta-blocker intake and at the time when coronary CTA acquisition began after prolonged apnea. The patients were then divided into two groups: Group A with baseline HR>65bpm and were put on oral beta-blocker according to our protocol before scanning, whereas Group B with baseline HR<65bpm and acted as control without oral intake of beta-blocker. Prolonged Apnea Scanning Protocol was used, as the patients were instructed to hold breath at 75% maximum lung capacity about 10–12 s after iv contrast injection, and manual triggering of the coronary CTA acquisition was made when the optimal contrast enhancement was seen on descending aorta with the lowest HR reduction or with the lowest HR below target achieved. Results: The mean breath-hold time was 11.5 s (SD 4.5 s) and the mean delay time was 23.5 s (SD 4.5 s). In Group A (n =208) with baseline heart rate more than 65bpm, the mean HR at arrival was 77.995bpm, at pre-imaging after oral beta-blocker was 64.928bpm and at CTA with prolonged apnea technique was 58.144bpm. About 84% of the patients showed reduction in HR, and the mean reduction of HR was 19.85bpm (p=0.0001). In Group B (n =99) with baseline heart rate less than 65bpm, the mean HR at arrival was 57.91 bpm and at CTA with prolonged apnea technique was 55.33bpm. About 66% of the patients showed reduction in HR, and the mean reduction of HR was 2.58 bpm (p=0.0036). Conclusion: In coronary CTA with a 320-detector-row CT scanner, prolonged apnea technique with 11.5 s during CCTA acquisition is an efficient mean in significantly lowering patients’ heart rate during the procedure. This technique is not only easy and safe to perform, but also allows wide range of HR selection and optimizes contrast enhancement, which will eventually leads to reduction in radiation dose and improvement in image quality.