Hybrid Cardiac Single Photon Emission Computed Tomography/Computed Tomography Imaging With Myocardial Perfusion Single Photon Emission Computed Tomography and Multidetector Computed Tomography Coronary Angiography for the Assessment of Unstable Angina Pectoris After Coronary Artery Bypass Grafting
A 73-year-old man was admitted to the cardiology department because of recent-onset angina pectoris. The patient had undergone coronary artery bypass graft surgery 10 years earlier with a left internal mammary artery graft to the left anterior descending artery and 4 saphenous vein grafts to the distal right coronary, first marginal, ramus intermedius, and first diagonal coronary arterial segments, respectively. Three years before the current admission, the patient developed recurrent angina pectoris and underwent angioplasty with stenting of the saphenous vein graft to the first diagonal artery. Because of recurrent symptoms on admission, the patient was referred for noninvasive assessment of the current status of his coronary artery disease with the use of a combined single photon emission computed tomography (SPECT)/computed tomography (CT) research system (Infinia LightSpeed, GE Healthcare Technologies, Milwaukee, Wis) that includes a dual-head variable-angle gamma camera and a 16-slice CT scanner. These components share a common table and are spatially aligned to enable sequential acquisition of both myocardial perfusion imaging and CT coronary angiography (CTCA) without patient motion between the procedures. Myocardial perfusion-gated SPECT studies were acquired using 130 MBq (3.5 mCi) Thallium for rest imaging and 925 MBq (25mCi) technetium 99m sestamibi for stress scintigraphy. The CTCA component of the examination was acquired during a 20-second breathhold at full inspiration with the use of a detector collimation of 16×1.25 mm, a rotation time of 0.5 sec, a tube voltage of 120 kV, and a current of 420 mA.
The Tl-201/technetium 99m sestamibi SPECT study was processed on an Xeleris workstation and the multidetector CT study on an Advantage Workstation (both GE Healthcare Technologies).
Curved multiplanar reformats of CTCA depicted a tight, irregular stenosis of the proximal saphenous vein graft to the first diagonal artery, just proximal to a patent stent that had been inserted 3 years earlier. The other 4 grafts were demonstrated to be patent across their entire lengths (Figures 1 and 2⇓). Myocardial perfusion SPECT images demonstrated the presence of a reversible perfusion defect involving the anterolateral segment, consistent with myocardial ischemia in that area (Figure 3).
Fusion of the native coronary arterial tree extracted from the CTCA study with the left ventricle epicardial surface derived from the myocardial perfusion SPECT study was performed using the application HeartFusion (Emory University, Atlanta, Ga). The fused images associated the large reversible perfusion defect in the anterolateral LV wall with the vascular territory of the first diagonal artery (Figure 4). On the basis of this information, revascularization of the severely stenosed bypass graft was performed with balloon angioplasty and stenting (Figure 5). The patient was discharged 24 hours after the procedure after complete clinical recovery.
A. Soil is an employee of and Dr Israel is a consultant for GE Healthcare Technologies.