A comparison of standard and high dose adenosine protocols in routine vasodilator stress cardiovascular magnetic resonance: dosage affects hyperaemic myocardial blood flow in patients with severe left ventricular systolic impairment

Abstract

Background Adenosine stress perfusion cardiovascular magnetic resonance (CMR) is commonly used in the assessment of patients with suspected ischaemia. Accepted protocols recommend administration of adenosine at a dose of 140\xa0µg/kg/min increased up to 210\xa0µg/kg/min if required. Conventionally, adequate stress has been assessed using change in heart rate, however, recent studies have suggested that these peripheral measurements may not reflect hyperaemia and can be blunted, in particular, in patients with heart failure. This study looked to compare stress myocardial blood flow (MBF) and haemodynamic response with different dosing regimens of adenosine during stress perfusion CMR in patients and healthy controls. Methods 20 healthy adult\xa0subjects were recruited as controls to compare 3 adenosine perfusion protocols: standard dose (140\xa0µg/kg/min for 4\xa0min), high dose (210\xa0µg/kg/min for 4\xa0min) and long dose (140\xa0µg/kg/min for 8\xa0min). 60 patients with either known or suspected coronary artery disease (CAD) or with heart failure and different degrees of left ventricular (LV) dysfunction underwent adenosine stress with standard and high dose adenosine within the same scan. All studies were carried out on a 3\xa0T CMR scanner. Quantitative global myocardial perfusion and haemodynamic response were compared between doses. Results In healthy controls, no significant difference was seen in stress MBF between the 3 protocols. In patients with known or suspected CAD, and those with heart failure and mild systolic impairment (LV ejection fraction (LVEF)\u2009≥\u200940%) no significant difference was seen in stress MBF between standard and high dose adenosine. In those with LVEF\u2009<\u200940%, there was a significantly higher stress MBF following high dose adenosine compared to standard dose (1.33\u2009±\u20090.46 vs 1.10\u2009±\u20090.47\xa0ml/g/min, p\u2009=\u20090.004). Non-responders to standard dose adenosine (defined by an increase in heart rate (HR)\u2009<\u200910\xa0bpm) had a significantly higher stress HR following high dose (75\u2009±\u200912 vs 70\u2009±\u200914\xa0bpm, p\u2009=\u20090.034), but showed no significant difference in stress MBF. Conclusions Increasing adenosine dose from 140 to 210\xa0µg/kg/min leads to increased stress MBF in patients with significantly impaired LV systolic function. Adenosine dose in clinical perfusion assessment may need to be increased in these patients.