Researchers found a prognostic value from single-photon emission computed topography (SPECT)/computed tomography (CT) monitoring of patients with critical limb ischemia undergoing lower extremity revascularization. These results were published in JACC: Cardiovascular Imaging.
Patients (N=25) with critical limb ischemia and diabetes mellitus scheduled for endovascular revascularization for foot ulcers that were not healing were prospectively enrolled for this study. All patients had resting SPECT/CT imaging at baseline and 1 to 3 days following their revascularization procedure. Clinical outcomes were assessed through 1 year.
Patients received technetium-99m-tetrofosmin (554.6±35.8 MBq) intravenously 15 minutes prior to imaging. A 360° step-and-shoot acquisition protocol (with 140.5 keV±10% window, 3° projection, 30-second stop) was used for SPECT followed immediately by CT images with slice thicknesses of 5 mm (with 140 kVp and 2.5 mA).
Patients had a mean age of 64.7±13.8 years, and 72% were men. Their mean body mass index was 30.1±6.5 kg/m2, and their average glycated hemoglobin (HbA1c) was 8.5%±2.0%. Of these patients, 92% had hypertension, 64% had hyperlipidemia, and 52% had coronary artery disease.
Patients had either single-vessel (n=13) or multivessel (n=12) disease. In total, 39 lesions were treated with percutaneous transluminal balloon angioplasty (n=31) or self-expanding stents (n=8).
The average percent change of angiosome foot perfusion was 9.9%±9.5%. By 3 months, 56% of patients had had 1 or more amputations, all of which were minor (toe or transmetatarsal amputations).
Stratified by amputation, patients who did not require an amputation had higher median profusions (9.99%; interquartile range [IQR], 7.69%-22.47%) compared with patients requiring an amputation (5.78%; IQR, 3.06%-7.55%; P =.011).
At 12 months, 76% of patients had had at least 1 amputation or had died. Two patients died, 12 had minor amputations, and 5 had major amputations (above or below the knee). Among the patients who had had amputations, the median revascularization-induced change of angiosome perfusion was 5.83% (IQR, 3.06%-10.01%) at 12 months.
The 24% of patients who remained amputation free at 12 months had significantly higher median revascularization-induced changes of angiosome perfusion (9.99%; IQR, 7.69%-22.47%; P =.014).
At 3 months, the cutoff for angiosome perfusion change that predicted amputation was 7.55% (area under the curve [AUC], 0.799; 95% CI, 0.613-0.985; sensitivity, 78.6%; specificity, 81.8%). The cutoff at 12 months was 11.56% (AUC, 0.833; 95% CI, 0.670-0.996; sensitivity, 89.5%; specificity, 50%).
High responders at 3 months (48%) and 12 months (36%) had significantly higher amputation-free survival (P =.002 and P =.03, respectively).
Additional predictors of amputation-free survival included percent change of angiosome perfusion (hazard ratio [HR], 0.38; 95% CI, 0.16-0.91; P =.030) and hemoglobin (HR, 0.52; 95% CI, 0.30-0.91; P =.023) and hematocrit (HR, 0.55; 95% CI, 0.30-0.99; P =.047) concentrations.
These results were limited by the small study sample, which necessitated using data from the same individuals to estimate cut-off values and confirm their utility.
The study authors concluded that SPECT/CT imaging was effective for monitoring changes to microvascular foot perfusion after endovascular revascularization and that early changes of angiosome perfusion predicted the likelihood of future amputations.
Chou TH, Alvelo JL, Janse S, et al. Prognostic Value of Radiotracer-Based Perfusion Imaging in Critical Limb Ischemia Patients Undergoing Lower Extremity Revascularization. JACC Cardiovasc Imaging. Published online November 18, 2020. doi: 10.1016/j.jcmg.2020.09.033