11 Haemodynamic and hyperaemic effects of adenosine in patients with atrial fibrillation undergoing quantitative myocardial perfusion cardiovascular magnetic resonance

<h3>Introduction</h3> Patients with atrial fibrillation (AF) may have an attenuated response to adenosine during vasodilator stress testing. We sought to investigate the haemodynamic and hyperaemic effects of adenosine in patients with AF undergoing adenosine-stress cardiovascular magnetic resonance (CMR) assessment. <h3>Materials and Methods</h3> We retrospectively examined 318 patients (AF n=158, sinus rhythm [SR] n=160) referred for clinical adenosine-stress CMR at 3-Tesla equipped with an automated quantitative perfusion sequence.¹ Baseline and peak heart rate (HR) and quantitative myocardial perfusion were compared between groups. <h3>Results</h3> At peak stress, the haemodynamic response was blunted in patients with AF (HR increase 7±10 bpm vs. 17±11 bpm in SR, p&lt;0.001). Fewer patients in AF met the threshold for a satisfactory HR response ≥10 bpm (40% in AF vs. 76% in SR, p&lt;0.001). There were no intergroup differences in hyperaemic myocardial blood flow (MBF) (1.52±0.65 mL/min/g in AF vs. 1.55±0.64 mL/min/g in SR, p=0.716) or myocardial perfusion reserve (2.65±1.12 in AF vs. 2.65±1.08 in SR, p=0.996). When the criterion for adequate hyperaemia was applied (stress MBF &gt;1.43 mL/min/g in ≥1 myocardial segment²), more patients in AF met the threshold for a satisfactory hyperaemic response than for a satisfactory HR response (70% vs. 40% respectively, p&lt;0.001). In patients with AF, the HR response poorly predicted an adequate hyperaemic response (area under the curve 0.50±0.06, p=0.956). AF (odds ratio [OR] 0.29 [0.17–0.50], p&lt;0.001) and left ventricular ejection fraction (OR 1.03 [1.00–1.05], p=0.023) were independently associated with achieving an adequate HR response on multivariable analysis, but only ejection fraction (OR 1.05 [1.02–1.09], p=0.002) predicted a satisfactory hyperaemic response. <h3>Discussion</h3> In patients with AF, the HR response to adenosine is blunted and poorly discriminates hyperaemia. Hence, it should not be used as a surrogate for an adequate stress response. Despite this, the majority of AF patients generated an adequate hyperaemic response to adenosine. However, the trend towards less hyperaemia in AF indicates that a larger study is required to investigate any marginal impact on diagnostic accuracy. <h3>Conclusion</h3> Most patients with AF generate an adequate hyperaemic response to adenosine: this confirms the validity of adenosine-stress CMR in AF in assessing ischaemia. <h3>Acknowledgements</h3> Nil <h3>References</h3> Kellman P, Hansen MS, Nielles-Vallespin S, Nickander J, Themudo R, Ugander M, <i>et al</i>. Myocardial perfusion cardiovascular magnetic resonance: optimized dual sequence and reconstruction for quantification. <i>Journal of Cardiovascular Magnetic Resonance.</i> 2016;<b>19</b>(1):43. Kotecha T, Monteagudo JM, Martinez-Naharro A, Chacko L, Brown J, Knight D, <i>et al</i>. Quantitative cardiovascular magnetic resonance myocardial perfusion mapping to assess hyperaemic response to adenosine stress. <i>European Heart Journal-Cardiovascular Imaging.</i> 2021;<b>22</b>(3):273–81.