Comparison of adenosine, dobutamine and bicycle exercise on intracoronary physiological indices in patients with myocardial bridges

Abstract Background We have recently demonstrated that patients with angina and nonobstructive coronary arteries (ANOCA) with myocardial bridges (MBs) exhibit maladaptive exercise physiology, due to abnormal wave energies arising at the tunnelled segment (1). Intracoronary pressure-derived indices in response to dobutamine and adenosine are used to identify an ischaemic substrate in these patients in clinical practice (2). However, it remains unknown if the changes induced by dobutamine and adenosine are comparable with physical exercise. Methods Patients with ANOCA and a MB in the left anterior descending artery underwent simultaneous acquisition of intracoronary pressure and flow sequentially during rest, supine bicycle exercise and intravenous adenosine and dobutamine infusion. We compared coronary perfusion efficiency (accelerating energy/total energy flux) and changes in specific wave energies in response to these three stressors. Results Twenty-five patients were enrolled (36% females, 59±9 years old). Patients had a high symptom burden (88% CCS II-IV) and myocardial bridge muscle index (79±30). Fractional flow reserve and coronary flow reserve were 0.86±0.05 and 2.5±0.5. Microvascular resistances during adenosine, dobutamine and exercise were 2.0±0.7, 3.4±1.4 and 4.3±1.3 mmHg.cm-1.s-1 respectively (p