Is the dyspnea during adenosine cardiac stress test caused by bronchospasm?

Background: Adenosine cardiac stress is widely used as an alternative to exercise testing during myocardial perfusion imaging (MPI). Dyspnea often accompanies the adenosine stress test. Although known asthmatic patients are excluded from this test because of the danger of bronchospasm, there is incomplete information regarding the role of factors such as chronic obstructive pulmonary disease (COPD) and tobacco smoking in adenosine-induced dyspnea.
Patients and Methods: A total of 122 consecutive patients (75 male, 47 female; mean age 59 years, SD 10 years) undergoing pharmacologic stress testing with an intravenous infusion of adenosine also had volume-flow spirometry (Vitalograph Compact, Vitalograph Ltd) before, during, and after the test. The indices assessed were forced expiratory volume in one second, its ratio to the forced vital capacity, and peak expiratory flow rate.
Results: Mild to severe symptoms were experienced by 81% of patients during adenosine infusion. More than half the patients had dyspnea, but there was no associated bronchospasm. Although the patients with COPD showed parameters indicative of bronchial resistance compared with those without this problem, there was no further deterioration after adenosine infusion. Similarly, patients with a history of tobacco abuse, despite showing a tendency toward increasing airways resistance, had no bronchospasm during the administration of adenosine.
Conclusions: (1) Although dyspnea is a common problem during adenosine stress MPI, it is not associated with any appreciable bronchospasm. (2) COPD and tobacco abuse do not appear to be contraindications to adenosine stress MPI studies. However, it is probably safe to exclude patients with severe COPD from adenosine stress MPI until after further evaluation with larger numbers of patients.