The Additive Value of Combined Assessment of Myocardial Perfusion and Ventricular Function Studies*
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The Additive Value of Combined Assessment of Myocardial Perfusion and Ventricular Function Studies* Trip J. Meine, MD1; Michael W. Hanson, MD1,2; and Salvador Borges-Neto, MD1,2 1Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, North Carolina; and 2Division of Nuclear Medicine, Department of Radiology, Duke University Medical Center, Durham, North Carolina This review focuses on the combined assessment of myo- In addition to providing quantitative ventricular function infor- cardial perfusion imaging and left ventricular function. Two mation, gated SPECT and radionuclide angiocardiographic clear roles for nuclear imaging in clinical practice include studies can evaluate regional wall motion and ventricular vol- the diagnosis of coronary artery disease (CAD) and assess- umes. This review focuses on the combined assessment of ment of prognosis in patients with known CAD. Combined myocardial perfusion and left ventricular function. Two clear roles for nuclear imaging in clinical practice include the diagno- nuclear imaging can play a role in both these areas, and in sis of coronary artery disease and assessment of prognosis in fact, the addition of left ventricular function data to myo- patients with known coronary artery disease. Ventricular func- cardial perfusion imaging can enhance the clinician’s ability tion information can help differentiate an attenuation artifact to both diagnose CAD and assess prognosis. from an infarct and is helpful in diagnosing 3-vessel coronary disease. Additionally, several studies have highlighted the prog- nostic benefit to combined assessment of myocardial perfusion DIAGNOSIS and ventricular function. Several new modalities have recently Assessment of ventricular function has long been recog- been reported that promise to continue to solidify the place of nuclear imaging in the diagnosis and prognosis of coronary nized as a sensitive means by which to diagnose the pres- artery disease. ence of CAD, as shown in early studies of first-pass radio- Key Words: clinical cardiology; SPECT; myocardial perfusion; nuclide angiocardiography (9,10). More recently, studies nuclear cardiology; ventricular function have evaluated the diagnostic benefit of adding ventricular J Nucl Med 2004; 45:1721–1724 function information to myocardial perfusion imaging. Borges-Neto et al. studied 167 patients with suspected CAD who underwent myocardial perfusion imaging, radionuclide angiocardiography, and cardiac catheterization. They found Early cardiac nuclear imaging studies were hampered by that combined nuclear perfusion and functional studies con- an inability to integrate myocardial perfusion imaging with tributed 31% of the diagnostic information beyond that studies of ventricular function. Though myocardial perfu- provided by clinical and electrocardiographic data alone sion imaging (1) and radionuclide cineangiography (2) have when evaluating for the presence of severe CAD; that is, been possible since the 1970s, it was not until the subse- functional studies had an incremental value of 16% and quent decade that the 2 modalities were used simultaneously myocardial perfusion imaging provided an additional value (3). Since those early reports, other investigators have suc- of 15% above functional studies (11). Other studies have cessfully related the results of using electrocardiogram- confirmed the benefit of ventricular function assessment. gated images to evaluate left ventricular function by com- Flamen et al. evaluated 52 patients undergoing cardiac paring their findings with equilibrium-gated blood pool catheterization after a recent myocardial infarction. All re- measurements (4), conventional radionuclide measurements ceived perfusion imaging as well as first-pass radionuclide (5), and echocardiographic ejection fraction assessments angiocardiography. The authors found that ejection fraction, (6–8). wall motion score, and myocardial perfusion score were all associated with the presence of severe CAD. However, on multivariate analysis, only wall motion score was an inde- Received Feb. 3, 2004; revision accepted Jul. 1, 2004. pendent predictor of severe CAD (12). Similarly, an eval- For correspondence or reprints contact: Salvador Borges-Neto, MD, Duke uation of 70 patients undergoing exercise treadmill as well University Medical Center, Box 3949, Durham, NC 27710. E-mail: [email protected] as myocardial perfusion imaging and radionuclide angiocar- *NOTE: FOR CE CREDIT, YOU CAN ACCESS THIS ACTIVITY THROUGH THE SNM WEB SITE (http://www.snm.org/ce_online) THROUGH OCTOBER diography found that stepwise addition of scintigraphic 2005. data—perfusion followed by ejection fraction—to the tread- COMBINED PERFUSION AND FUNCTION STUDIES • Meine et al. 1721 mill score provided significant incremental value in predict- Thus, the diagnostic benefits of nuclear modalities that ing the extent of CAD (13). determine ventricular function cannot be overstated. These The benefit of ventricular function information is not benefits encompass enhanced sensitivity and specificity for limited to first-pass radionuclide angiocardiography. An significant coronary artery stenoses. Furthermore, the addi- evaluation of 99 patients with suspected CAD who were tion of ventricular function information to myocardial per- undergoing gated SPECT in addition to myocardial perfu- fusion imaging can aid in the interpretation of clinically sion imaging found that postexercise wall motion abnormal- complex studies, such as those involving multivessel dis- ities added significant incremental value over stress myo- ease and attenuation artifacts. cardium perfusion alone for the identification of severe CAD in patients with normal resting myocardial perfusion PROGNOSIS findings. The sensitivity for identifying severe CAD by wall motion abnormality was 78%, versus 49% for myocardial An equally, if not more, useful role for the adjunctive use perfusion imaging (P Ͻ 0.0001), and specificity was not of myocardial perfusion and ventricular function studies is significantly different. The authors suggested that decreases in determining cardiac prognosis. The prognostic value of in subendocardial blood flow, as might be seen in severe SPECT alone has long been recognized. Machecourt et al. CAD, could result in severe impairment of myocardial evaluated the prognostic information gleaned from SPECT function without causing an observable perfusion defect myocardial perfusion imaging and found that cardiovascular survival was related to the number of perfusion abnormal- (14). ities present, with a cumulative 32-mo survival of 83% in Much of the benefit of the addition of ventricular function patients with 4 or more abnormal cardiac segments (19). data to myocardial perfusion imaging may relate to the Similarly, another group of investigators found that the ability of gated SPECT and radionuclide angiocardiography extent of reversible defects on SPECT added information to to help differentiate attenuation from infarct. This finding clinical and catheterization data (20). Hachamovitch et al. was confirmed by DePuey et al., who performed myocardial studied 2,200 patients without known CAD and found that perfusion imaging and gated SPECT on 551 patients. Thirty- SPECT added prognostically even after clinical and exer- three percent of these patients had isolated fixed defects on cise variables had been utilized (21). myocardial perfusion imaging. By using gated SPECT to As with myocardial perfusion imaging, ventricular func- evaluate these areas of decreased perfusion, the percentage tion assessment has been found—in numerous studies of of patients with “unexplained fixed defects,” that is, no both radionuclide angiocardiography and gated SPECT—to clinical myocardial infarction, was decreased from 14% to provide prognostic value. Several early studies provided 3%. About half of these unexplained defects were anterior evidence that evaluation of left ventricular function, specif- abnormalities in women, which were believed to be related ically by radionuclide angiocardiography, adds significantly to breast attenuation. The authors thus concluded that gated to the prognostic value of clinical variables. Pryor et al. at SPECT could potentially improve specificity (15). Another Duke University followed 386 patients for up to 4.5 y. The evaluation of 285 patients undergoing gated SPECT found investigators examined 6 variables, including rest and ex- that the addition of ventricular function information to myo- ercise ejection fraction by radionuclide angiocardiography, cardial perfusion data decreased the number of “borderline” change in ejection fraction with exercise, left ventricular interpretations from 89 to 29 (16). Similarly, Taillefer et al. wall motion abnormalities, and exercise time and found that studied 115 with known coronary anatomy. They performed exercise ejection fraction was the variable most associated thallium myocardial perfusion imaging as well as gated with future cardiac events (P Ͻ 0.01) (22). SPECT and found that specificity for coronary stenoses Later studies continued to evince the predictive benefits improved by greater than 50%, from 86% to 94%, and that of radionuclide angiocardiography over clinical variables. specificity for stenoses improved by greater than 70%, from The Duke group studied 571 patients with symptomatic 84% to 92% (17). CAD and followed them for a median of 5.4 y. The inves- Another potential use of this additional technology is in tigators found that the most important radionuclide angio- identifying