LABORATORY INVESTIGATION CINE CT SCANNING Determination of left ventricular mass in dogs with rapid-acquisition cardiac computed tomographic scanning

The development of left ventricular hypertrophy in patients with heart disease often has far-reaching clinical implications with respect to overall morbidity and mortality. Approaches used to assess left ventricular mass include electrocardiography, echocardiography, contrast ventriculography, single photon-emission tomography, and conventional computed tomography. However, all of these modalities suffer from some major draw back that precludes widespread application to all patients. In this study we assessed the accuracy of determinations of left ventricular mass in 22 dogs by rapidacquisition (50 msec) computed axial tomography (RACAT), an ultrafast computed tomographic (CT) instrument. Electrocardiographically triggered, end-diastolic, short-axis cardiac scans were obtained from apex to base during administration of intravenous iodinated contrast. Myocardial edges were determined for each tomographic scan by two methods: the regional half-contour method (the CT density half way between that of the left ventricular myocardium and adjacent ventricular cavities or lung) and "interactive plateau thresholding" of the cardiac borders. Left ventricular mass by RACAT was calculated as the sum of the mass of each individual scan from apex to base (modified Simpson's rule). Postmortem left ventricular mass ranged from 58 to 160 g. The correlation between true left ventricular mass and tomographically determined mass was excellent (r = .99), with the slope and y intercept not statistically different from 1 and 0, respectively. The standard error of the estimate was 4.1 g. Interobserver and intraobserver variability for determining left ventricular mass demonstrated excellent agreement (r = .99 and r = .99, respectively). We conclude that quantitative assessment of left ventricular mass can be accurately and reproducibly performed in dogs by rapid acquisition CT scanning. It is likely that this technique will be readily transferable to the clinical settings and prove to be an important method for quantifying left ventricular mass in patients. Circulation 72, No. 6, 1355-1364, 1985. DEVELOPMENT of left ventricular hypertrophy is often a harbinger of adverse clinical consequences. It is known that the incidence of sudden death associated with acute myocardial infarction is increased threefold among patients with concomitant left ventricular hyFrom the Cardiovascular Center, Departments of Internal Medicine, Electrical and Computer Engineering and Radiology, University of Iowa, Iowa City VA Medical Center, and Department of Radiology University of California at San Francisco. Supported by grants NIH HL20827, Ischemic SCOR HL32295, PPG HL14388-145, and by Imatron, Inc. Address for correspondence: Andrew J. Feiring, M.D., Department of Internal Medicine, Cardiovascular Division, University of Iowa Hospitals and Clinics, Iowa City, IA 52242. Received Jan. 3, 1985; revision accepted Aug. 22, 1985. Dr. Feiring is a recipient of the Veterans Administration Associate Investigator Award. Dr. Rumberger is a recipient of the American Heart Association Clinician Scientist Award. Dr. Skorton is a recipient of a Research Career Development Award from the National Heart, Lung and Blood Institute. Vol. 72, No. 6, December 1985 pertrophy and hypertension. ' Regardless of the cause, left ventricular hypertrophy has recently been implicated as a cause for diminished coronary artery reserve.' 3 Furthermore, in patients with left ventricular hypertrophy the functional integrity of the ventricle tends to deteriorate over time and may eventually result in overt heart failure. Determination of left ventricular mass in vivo has been attempted by various techniques, including electrocardiography,4 biplane left ventricular angiography,5 6 M mode and two-dimensional echocardiography7-12 and 20'T1 imaging in conjunction with single photon-emission tomography'3 and gated and dynamic computed tomography,'4' '5 however, none are ideal. A rapid-acquisition computed axial tomographic (RACAT) system is now available that is capable of obtaining real-time, stop-action tomographic images of the left ventricle in conjunction with excellent spa1355 by gest on July 6, 2017 http://ciajournals.org/ D ow nladed from