Adenoscan

Adenosine (Adenoscan™, Sanofi-Synthelabo, Berlin, Germany) will be infused at 140 μg/kg/min [13 (link)], via a 20-gauge cannula sited in an antecubital vein, using a syringe pump (Graseby™ 3500; Graseby Medical LTD, Watford, Hertfordshire, UK). Adenosine will be infused for a minimum of 6 minutes before acquiring stress images. Indications for terminating adenosine infusion are persistent or symptomatic third degree atrioventricular block, severe hypotension (systolic blood pressure <90 mmHg), or bronchospasm. Scans will be supervised by an MRI trained clinician with access to immediate resuscitation facilities.

All data were acquired using a 3T Verio system (Siemens AG, Healthcare Sector, Erlangen, Germany). Standard cardiac imaging planes and a short axis stack of left ventricular cine data were acquired using routine steady state free precession (TrueFISP) acquisitions. Native T₁ relaxation rates (i.e. in the absence of CA) were calculated using the modified Look-Locker inversion (MOLLI) recovery technique [13 (link)]. Stress imaging was performed by intravenous infusion of 140 μg/kg/min of adenosine (Adenoscan, Sanofi Aventis). Fifty dynamic perfusion images were obtained at diastole across three short-axis view slices: basal, mid-ventricular and apical slices according to the standard 16-segment heart model [14 (link)]. Perfusion images were acquired using a turbo-fast low angle shot (FLASH) saturation recovery prepared single-shot gradient echo pulse sequence (repetition time/ echo time 2.20 ms/1.07 ms, flip angle 12^o, slice thickness 8 mm, preparation pulse delay (PD) to central line of k-space 100 ms, matrix size 192 × 108 and FoV 330 mm × 440 mm). With the application of GRAPPA (accelerator factor of 3) and partial Fourier acquisition of 0.75, each dynamic frame consisted of 48-phase encoded lines. All CMR perfusion data were acquired using electrocardiogram-gating.