Novel insights into the pathophysiology of different forms of stress testing

Abstract

Background: The impact of different forms of myocardial perfusion imaging on cardiac wall stress and myocardial ischemia is incompletely understood. Methods: In a prospective study, 489 consecutive patients with suspected myocardial ischemia referred for single-photon emission computed tomography (SPECT) were enrolled. 266 underwent bicycle stress testing, 65 stress testing with adenosine alone and 158 combined stress testing. Ischemic electrocardiography (ECG) changes, typical angina symptoms as well as cardiac wall stress quantified by levels of brain natriuretic peptide (BNP) measured before and 1 minute after stress testing were used to compare the 3 testing modalities. Myocardial ischemia was defined as a summed difference score (SDS) of ≥2 detected by SPECT. Results: Median BNP-increases were significantly higher in the bicycle stress group as compared to the adenosine only group (22 vs. -3 pg/ml; p<0.001). In the bicycle group, patients with evidence of myocardial ischemia on imaging more often had ischemic ECG changes (33% vs. 12%, p<0.001) and a greater increase in BNP levels (28 vs. 16 pg/ml, p<0.001) compared to those without ischemia (figure). This was not observed in the adenosine group and in the combined group. Patients in the combined group (28% vs. 15%, p =0.047) and bicycle group (25% vs. 9%, p<0.001) more often had angina symptoms if showing reversible perfusion defects compared to those without. This was not observed in the adenosine only group. BNP-changes in the 3 testing-protocols Conclusion: Bicycle stress but not adenosine stress results in an increase of cardiac wall stress. The lack of increase in cardiac wall stress and the absence of more ischemic ECG-changes in patients with inducible perfusion defects, suggests that stress testing using adenosine alone does not necessarily induce myocardial ischemia.