However, the diagnosable proportion increased to 80.0 % (at heart rate 60–64 beats/min), 85.7 % (at heart rate

55–59 beats/min), and 100.0 % (at heart rate ≤54 beats/min), showing a positive correlation between the diagnosable proportion for the reconstruction images at optimal conditions and heart rate at CCTA by 16-slice MDCT. Fig. 5 Relationship between diagnosable proportion and heart rate. There was a positive correlation between the diagnosable proportion and heart CP 690550 rate. a images at mid-diastole, b images at optimal conditions 3.6 Safety and Tolerability No subject died and no adverse reaction that required termination of study drug administration occurred during the study period. 4 Discussion In the present study, injection of the study drug was found to be effective to rapidly lower the heart rate soon after

administration. The study drug, with a half-life of only 4 min, did not have a prolonged β-blocking effect after CCTA and lowered the heart rate only during CCTA (Fig. 3); therefore, hemodynamics do not need to be monitored for a long period after CCTA. In fact, in clinical practice using oral agents, patients must attend the hospital to take a β-blocking agent 1–2 h before initiation of CCTA and to monitor their heart rate to determine whether it meets the conditions for CCTA. This means it takes several hours before CP673451 in vitro starting CCTA. In the case of this study drug, in contrast, administration is possible immediately before CCTA, allowing early completion of imaging. The results from the present PF-02341066 in vitro study confirmed that this drug can be administered to patients just before CCTA, in contrast to oral agents requiring administration 1–2 h before CCTA. Thus, this drug appears to increase the efficiency of CCTA. On the other hand, while bradyarrhythmia and hypotension induced by the β1-blocking

effect and bronchoconstriction and peripheral circulatory disorder induced by the β2-blocking effect are known adverse reactions Amisulpride of β-blockers, the primary adverse reactions to the study drug are likely to be bradyarrhythmia and hypotension because of the high selectivity of this drug for β1-receptors (β1/β2: 251/1) [23, 24]. In the present study, no subject developed bradyarrhythmia and hypotension. Furthermore, this drug was shown to lower the heart rate only during CCTA (for approximately 30 min) and not to have a prolonged effect after the completion of CCTA, confirming its safety. Meijboom et al. [25] and Marano et al. [26] confirmed the high diagnostic performance of CCTA in multivendor, multicenter clinical studies using other CT models. In the present study using 16-slice CTs from Siemens, Toshiba, and GE, which are widely used in Japan, CCTA was performed only in subjects with a pre-CT heart rate as high as 70–90 beats/min, confirming the efficacy and safety of injection of the short-acting β1-receptor blocker landiolol hydrochloride.