Significance of PQ interval in acquisition of coronary multidetector row computed tomography

Abstract Background Since image quality obtained in the mid-diastolic [or slow filling (SF)] phase is generally superior to end-systolic image in coronary multidetector row computed tomography (MDCT), low heart rate (HR) comprises the most important factor for acquisition of high-quality images. However, despite HR 200 ms) were evaluated. RR and PQ were measured on electrocardiogram and systolic and SF phase with 4-chamber cine cardiac computed tomography. SF significantly ( p < 0.0001) correlated with RR (SF = −471 + 0.720RR, r = 0.887) in all subjects. The SF of without 1°AVB (292 ± 97 ms) was significantly ( p < 0.0147) longer than that of with 1°AVB (251 ± 121 ms), although RR was not significantly different between the two groups. The SF/RR of without 1°AVB (27.2 ± 6.1%) was also significantly ( p < 0.0001) higher than that of with 1°AVB (22.7 ± 8.0%). The coefficient of correlation between (RR − PQ) and SF [ r = 0.915, p < 0.0001, SF = −362 + 0.742(RR − PQ)] was significantly ( p < 0.034) higher than that of correlation between RR and SF in all subjects. The SF of rank A image quality was significantly longer than that of rank B ( p < 0.0001) or rank C ( p = 0.0042). In critical HR (60–69 bpm), the optimum phase was ES in 7/139 patients without 1°AVB, and SF in 3/13 patients with 1°AVB ( χ2 , p < 0.0416). Conclusion Since SF depends on (RR − PQ), if PQ is long in critical HR, it might be difficult to reconstruct high quality images in the SF phase.