Real-time cine and myocardial perfusion with treadmill exercise stress cardiovascular magnetic resonance in patients referred for stress SPECT

Abstract

Background: To date, stress cardiovascular magnetic resonance (CMR) has relied on pharmacologic agents, and therefore lacked the physiologic information available only with exercise stress.

Methods: 43 patients age 25 to 81 years underwent a treadmill stress test incorporating both Tc99m SPECT and CMR. After rest Tc99m SPECT imaging, patients underwent resting cine CMR. Patients then underwent in-room exercise stress using a partially modified treadmill. 12-lead ECG monitoring was performed throughout. At peak stress, Tc99m was injected and patients rapidly returned to their prior position in the magnet for post-exercise cine and perfusion imaging. The patient table was pulled out of the magnet for recovery monitoring. The patient was sent back into the magnet for recovery cine and resting perfusion followed by delayed post-gadolinium imaging. Post-CMR, patients went to the adjacent SPECT lab to complete stress nuclear imaging. Each modality's images were reviewed blinded to the other's results.

Results: Patients completed on average 9.3 +/- 2.4 min of the Bruce protocol. Stress cine CMR was completed in 68 +/- 14 sec following termination of exercise, and stress perfusion CMR was completed in 88 +/- 8 sec. Agreement between SPECT and CMR was moderate (kappa = 0.58). Accuracy in eight patients who underwent coronary angiography was 7/8 for CMR and 5/8 for SPECT (p = 0.625). Follow-up at 6 months indicated freedom from cardiovascular events in 29/29 CMR-negative and 33/34 SPECT-negative patients.

Conclusions: Exercise stress CMR including wall motion and perfusion is feasible in patients with suspected ischemic heart disease. Larger clinical trials are warranted based on the promising results of this pilot study to allow comparative effectiveness studies of this stress imaging system vs. other stress imaging modalities.

Figures

Figure 1

Study Protocol. Patients referred for clinically-indicated treadmill SPECT examination were enrolled in a combined protocol that allowed rest and post-exercise CMR in combination with the SPECT protocol with a single stress procedure.

Figure 2

Normal Treadmill Stress CMR. End-diastolic (A, E) and end-systolic (B, F) frames of cine imaging at rest (top row) and immediately post-stress (bottom row) plus stress myocardial perfusion imaging (C, G) are shown in a 52 year-old postmenopausal female referred for stress SPECT to evaluate dyspnea; both stress modalities were negative for ischemia. In addition, late post-gadolinium enhancement (LGE) CMR imaging (D) showed no myocardial enhancement.

Figure 3

Electrocardiography During Treadmill Stress CMR. Rest (left) and stress (right) electrocardiography obtained in a 64 year-old male with exertional chest pain and remote anteroseptal myocardial infarction demonstrates exercise-induced left bundle branch block with reproduction of symptoms at stage 4 of the Bruce treadmill protocol.

Figure 4

Ischemia by Treadmill Stress CMR and SPECT. Rest and stress CMR and SPECT images in the same patient of Fig. 3 both demonstrate myocardial ischemia, with corresponding obstructive coronary artery disease by angiography. Resting diastolic (A) and systolic (B) cine frames vs. comparable post-exercise cine frames (F, G) show stress-induced inferior wall contractile dysfunction (G, arrowhead). Inferior ischemia is also demonstrated by CMR perfusion imaging (C-rest perfusion vs. H-stress perfusion, arrowhead). Prior MI in the anteroseptum can be seen on late post-gadolinium imaging (E); note some fatty replacement in the infarct region evident as bright intramyocardial signal on noncontrast gradient echo cine frame in panel B. Rest Tc-99 m perfusion SPECT (D) suggests normal perfusion, though somewhat obscured by adjacent bowel uptake; stress Tc-99m perfusion SPECT shows inferior wall defect (I, arrowhead). The patient went on to invasive angiography that showed an occluded right coronary artery (J, arrow) with some left-to-right collateral flow.

Figure 5

Ischemia by Treadmill Stress CMR Not Evident by SPECT. Rest and stress images show ischemia by CMR not evident by SPECT in a 56 year-old male with known coronary artery disease was referred for stress testing to evaluate abnormal stress ECG done prior to starting a supervised exercise program. Exercise-induced ischemia is evident by ST depression on electrocardiography (A-rest, F-stress), lateral wall motion abnormality on end-systolic frames from cine CMR (B-rest, G-stress) and lateral perfusion abnormality on first-pass contrast enhanced CMR (C-rest, H-stress). No myocardial infarct scar was seen by LGE CMR (E). SPECT images obtained during the same stress examination suggest normal myocardial perfusion (D-rest, I-stress). Invasive angiography (J) identified high-grade ostial stenosis of a large ramus intermedius coronary artery leading to percutaneous coronary intervention.

Figure 6

Summary Findings of Treadmill Stress CMR, SPECT and Coronary Angiography. Cardiac catheterization with x-ray coronary angiography (Cath) was performed in a subset of patients; angiographic results are shown in the context of CMR (a) or SPECT (b) indicating presence vs. absence of myocardial ischemia.