Answer: If the patient is able to exercise and achieve his or her target heart rate, single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is generally preferred. Asthma may be a contraindication for administering adenosine and related pharmacologic stress agents to obtain a hyperemic response for stress imaging. Asthma also can be a contraindication to administer beta blockers to have heart rate control for coronary computed tomography angiogram (CTA). However, if a dual source CT scanner is available, diagnostic coronary CTA may be obtained without the use of beta blockers.
In a patient with inhaler-dependent asthma, dobutamine cardiovascular magnetic resonance (CMR) could be a good option. Dobutamine stress echocardiography is known to have limitations in the setting of left bundle-branch block (LBBB), and it can be expected that dobutamine CMR might be similarly limited. However, dobutamine CMR might be the only safe option if the patient is inhaler dependent and unable to exercise to achieve their target heart rate. Results of a study presented at the 2011 American Heart Association Scientific Sessions demonstrated the prognostic value of dobutamine CMR in patients with known CAD and peripheral vascular disease (Figure 1). This study included 215 consecutive patients with CAD and peripheral arterial disease who had undergone dobutamine CMR in a 4-year period.2 Sixty-five patients had early revascularization and were excluded from analysis. The remaining 140 patients were followed for a mean of 39 ± 18 months. Fifty-two patients (37%) experienced stress-induced wall motion abnormalities (WMA) during testing, and 15 cardiac events were reported. In multivariate analysis of clinical data, stress-induced WMA on dobutamine CMR (HR = 5.8; 95% CI, 1.6-21.3; P = .008) was an independent predictor of late cardiac events. Patients without inducible WMA demonstrated a good prognosis, with a 48-month event-free survival of 95.5%.
The nature of the ECG abnormality must also be taken into consideration. The presence of baseline ECG abnormalities, such as electronically paced ventricular rhythm or left bundle-branch block (LBBB), may interfere with interpretation of exercise ECG testing. For example, patients with nonspecific