W. B. CALHOUN, M.D., ROGER M. MILLS, JR., M.D. WALTER E. DRANE, M.D.. University of Florida, College of Medicine, Gainesville, Florida, USA summary.
Clin. Cardiol. 19, 367-369 (1996)
Clinical Investigations Clinical Importance of Viability Assessment in Chronic Ischemic Heart Failure W. B. CALHOUN, M.D., ROGERM. MILLS, JR., M.D. WALTER E. DRANE, M.D.
University of Florida, College of Medicine, Gainesville, Florida, USA
summary Background and hypothesis: Revascularizationhas provided an effectivetreatment of depressed left ventricularfunction in patients with chronically ischemic or “viable” myocardium. Assessment of viable myocardium can be achieved by several noninvasive techniques including dobutamine stress echo or radionuclides such as flurodeoxyglucose (FlXDG).FlsDG uptake studies are based on the assumption that enhanced glucose uptake in areas of diminished blood flow provides evidence of viable myocardium. To determine the clinical utility of viability assessment in the management of chronic ischemic left venmcular dysfunction, we reviewed the findings and short-term treatment of a series of patients referred for heart fdure evaluation who had subsequent Fi8DG uptake scans. Methods: We retrospectively reviewed 59 consecutive FixDGviability studies in a series of patients who had documented coronary artery disease and depressed left ventricular function. Single photon emission computerized tomography (SPECT)with FI8DG was performed in the patients and these images were compared to SPECT images of resting myocardial perfusion using thallium, sestamibi, or teboroxime.Clinical decisions based on the results of these scans were obtained from chart review. Thirty-day mortality was determined from chart review or contact with the patient’s physician. The patients were divided into those without and with Fi8DGuptake consistent with viable ischemic myocardium. Further analysis included subgroups of patients who were advised to undergo transplantation, revascularization,or to continue medical therapy.
Address for reprints: Roger M. Mills. Jr., M.D. University of Florida College of Medicine Division of Cardiology 1600 SW Archer Road BOX 100277 JHMHC Gainesville, FL 32610-0277, USA Received: October 13. 1995 Accepted with revision: October 18, 1995
Results: Of 34 patients referred for cardiac transplantation, 18 had viable myocardium and 13 underwent revascularization. In the entire study group, 34 of 59 (58%) had evidence of viable myocardium and 29 had subsequent revascularization procedures. Thirty-day survival for all revascularization patients was 86%. Conclusion: Assessment of myocardial viability with FisDGSPECT imaging in patients with ischemic left ventricular dysfunction led to a clinical decision for revascularization in approximately half the patients with severe coronary disease and left venmcular dysfunction who were evaluated for myocardial viability in our institution. Key words: myocardial viability, heart failure, single photon emission computed tomography imaging, revascularization
Introduction Although orthotopic heart transplantation provides effective treatment of end-stage cardiomyopathy,the limited availability of donor hearts’ has prompted investigationof revascularization for reversal of left ventricular (LV) contractile depression as an alternative. Braunwald and mower2 and Rahimtoola3suggested that potentially reversible impairment of LV function may occur secondary to chronically ischemic myocardium in their descriptions of hibernating,or chronically ischemic, viable myocardium. Subsequent studies4-” demonstrated improvement of LV function following revascularization of ischemic areas of myocardium with either catheter-based intervention [percutaneous transluminal coronary angioplasty (PTCA)]or coronary artery bypass grafting (CABG). Assessment of myocardial viability for potential mechanical revascularization may be achieved by several noninvasive techniques including ( 1) radionuclides:thallium201 (201TI), FI*-flurodeoxyglucose,C”-acetate, or (2) dobutamine stress e ~ h o . ’ ~Flurodeoxyglucose -’~ (FigDG)uptake studies are based on the assumption that augmented glucose uptake in areas of diminished blood flow provides evidence of viable myocardium.l8To determine the clinical utility of viability assessmentin the managementof chronic ischemic heart failure, we reviewed the findings from imaging studies and short-term treatment outcomes of a series of 59 consecutive patients, referred for heart failure evaluation,who had subsequent F18DG scans.
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Results The 59 patients included 47 males and 12 females with a mean age of 57 k 8 years and a mean LV ejection fraction of 2 1 k 7%.Figure 2 summarizes our findings. Thirty-four patients originally presented for evaluation as potential heart transplant recipients, while 25 had F18DG scans for other reasons. Of the 34 patients referred for transplant evaluation, 18 (53%) had demonstrable hibernating myocardium. Of these, 13 subsequently had either CABG or PTCA, while 3 were medically managed because of poor target vessels. Two patients with poor distal vessels underwent orthotopic heart transplantation. Eight of the 16 patients referred for transplantation, who had no hibernating myocardium, eventually received transplants, and 8 continued on intensified medical management. In the total group of 59 patients, 34 (58%)had evidence of hibemating myocardium, and 24 of these subsequently had CABG while 5 had PTCA. Thirty-day survival for all revascularized patients was 86%. FIG.I Example of an Fi8DG SPECT study showing significant glucose uptake in the anterior and septa1walls in areas of relative hypoperfusion as shown by sestamibi imaging. Short-axis views, base to apex. Increased uptake of both tracers is shown in red and yellow; compare image pairs 3.4, and 5 in particular.
Methods We retrospectivelyanalyzed 59 consecutive F18DG viability studies performed between April 1992 and October 1994.
All patients had angiographic evidence of coronary artery disease and impaired LV function. Single photon emission computed tomography (SPECT) imaging with Fi8DG was performed at approximately 60 min after glucose loading and 3 W 5 min after the intravenousinjection of 10mCi of FI8DG. Images were then compared with SPECT images of resting myocardial perfusion using thallium, sestamibi, or teboroxime. Hibernating myocardium was defined as present when increased FI8DG uptake occurred in an area of compromised resting blood flow. Figure 1 illustrates typical SPECT images indicating viable myocardium and markedly impaired perfusion. Determination of the results of the scan and clinical decisions involving management based on these results were obtained from chart review. Left ventricularejection fraction was determined by left ventriculogram, gated cardiac blood pool scan, or two-dimensional (2-D) echocardiography. For those who underwent revascularization,30-day mortality was determined by chart review or contact with the patient's personal physician. The study patients were classified into those with significant evidence of viability versus those without viability in areas of depressed coronary flow. These groups were further subdivided into those who were advised to pursue transplantation, those who underwent revascularization with CABG or WCA, and those who continued medical therapy.
Discussion Our data demonstrate that myocardial viability assessment with SPECT imaging to evaluate resting blood flow and FL8DGuptake provided clinically useful information in a large series of patients with depressed LV ejection fraction (LVEF) due to chronic ischemic heart disease. At this time, follow-up is limited to 30-day data in those patients who underwent a revascularizationprocedure; we did, however, obtain 100%followup from chart records, clinic notes, and contact with the patient's local physician. Thirty-day survival in this group, with a mean LVEF of 21%, was 86%, with only one patient experiencing very early postoperative death 3 days after CABG. Positron emission tomography (PET) studies using FIXDG as an indicator of myocardial viability have demonstrated im-
Heart-transplant referred
Total patients = 59 Not heart-transplant referred 25 (42%)
34 (58%)
Not viable
Viable
Not viable
Viable
16/34 (47%)
18/34 (53%)
9/25 (36%)
16/25 (64%)
Medical 3'
Tx
2"
FIG.2 Clinical outcome of viability assessment in 59 patients with documented coronary disease and left ventricular dysfunction. "No conduits or inoperable distal vessels. CABG = coronary artery bypass graft, PTCA = percutaneous transluininal coronary angioplasty, Medical = medical therapy, Tx = transplantation.
W. B. Calhoun et al.: Viability assessment in chronic ischemic heart failure
provement in LV function with revascularizationof viable but hypoperfused myocardium.I9We have used SPECT for determination of F18DG uptake, and our data suggest that these studies provide clinically important information in the management of patients with ischemic heart disease and LV systolic dysfunction.Fi8DGSPECT is a cost-efficientway to perfomi FI8DGimaging. The break-even cost of Fi8DGSPECT is approximately 25 to 33% that of PET, with adequate imaging capabilitiesfor cardiac imaging.*(’In a population of patients with end-stage heart failure, revascularization probably representscost-effectivetherapy even with the costs of screening studies and CABG. Critique
This was a retrospectiveobservational study, not a randomized prospectivetrial. The objective, however, was not to confirm or exclude a hypothesis, but to evaluate the role of the test in clinical practice. Further follow-up to evaluate the response of LVEF after revascularization in long-term survivors is planned. A study of FI8DG SPECT in which all patients proceeded to revascularizationwould allow determination of the predictive value of the test. However, the F18DG PET data available in the literature preclude the use of F’*DGimaging in a blinded fashion on ethical grounds, since excessive risk and no benefit would be expected for revascularizationprocedures in patients with no evidence of viable but hypoperfused myocardium. This introduces a degree of selection bias in the choice of therapy for those referred for an F18DG scan and who demonstrated increased glucose uptake in the face of compromised blood flow. Long-term follow-up data for this group are critical to validate the hypotheses on which treatment is now based.
Conclusion Our retrospective analysis indicates that assessment ofmyocardial viability using F18DG uptake by SPECT imaging in patients with ischemic heart disease and depressed LV function led to a clinical decision for revascularization in approximately half of the patients referred to our center for heart failure management.These data suggest that LV dysfunction due to chronically hypoperfused but viable myocardium occurs with clinicallyimportant frequency. In a particularly important subset, demonstration of hibernating myocardium in 18 of 34 patients referred for heart transplant evaluation lead to revascularizationas an alternative in 13 patients.
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