For patients with suspected stable CAD, a tiered cardiac CT protocol offers an effective and safe alternative to functional testing. Incorporating the calcium scan into the diagnostic workup was safe and lowered diagnostic expenses and radiation exposure.

In patients with suspected stable CAD, a tiered cardiac CT protocol with dynamic perfusion imaging offers a fast and efficient alternative to functional testing. (Comprehensive Cardiac CT Versus Exercise Testing in Suspected Coronary Artery Disease 2 [CRESCENT2]; NCT02291484).

, which resulted in a K i value for MB of 0.58+0.02 mmol l 71. 6 In conclusion, MB may be considered as a cholinesterase inhibitor with additional, relevant anity for muscarinic binding sites at concentrations at which MB is used for investigations into the endothelial system. In our opinion these interactions between MB and the cholinergic system invalidate the use of MB as a tool for the investigation of the L-arginine-NO-pathway, in particular when muscarinic receptor stimulation is involved.

The role of muscarinic (M)-receptor subtypes in the regulation of vascular tone has not yet been defined in humans. To analyze the role of M-receptor subtypes in the forearm resistance vasculature of normotensive volunteers (n = 20), we infused acetylcholine (ACh) and methacholine (MCh) in the presence of saline and the antagonists atropine (nonselective), pirenzepine (M1 selective), and AF-DX 116 (M2 selective), using automated R-wave-triggered venous occlusion plethysmography. Schild analysis was applied by calculating plasma concentrations of the infused compounds and determining EC50 values. ACh and MCh both caused dose-dependent vasodilation, with EC50 values of 537 and 52 nmol/L, respectively. The apparent 10-fold higher potency of MCh compared with ACh may be explained by rapid degradation of ACh in plasma. The concentration-response curve of MCh was shifted to the right by atropine, pirenzepine, and AF-DX 116, with apparent pA2 values of 8.03 +/- 0.03, 6.71 +/- 0.08, and 5.32 +/- 0.05, respectively, and slopes not different from unity. The present technique enabled us to perform M-receptor characterization by Schild analysis in humans. The affinity constants and rank order of potency--atropine > pirenzepine > AF-DX 116-suggest that cholinergic vasodilation in this vascular bed is predominantly mediated by the M3-receptor subtype. The EC50 value of MCh and the pA2 values of pirenzepine and AF-DX 116 are comparable to values reported for in vitro experiments.