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Fatty acids are promptly taken up, metabolised and eliminated by healthy cardiomyocytes. Cardiomyopathy, coronary heart disease and chronic rejection are known to be associated with an impaired fatty acid metabolism. It was the aim of this study to investigate fatty acid metabolism in a rat heart transplant model and to correlate scintigraphic findings with histological changes. After right-side nephrectomy of Lewis recipients Brown Norway cardiac allografts were anastomosed to the renal vessels. Animals were given no immunosuppression. The metabolism of carrier-free 17-123 jodo-heptadecanoic acid (123J-HDA) with a specific activity of > 2 x 10(17) Bq/ml was scintigraphically measured between days 1 and 11. An increase in the grade of rejection was observed over time. Fifty-six frames of 30 s duration each were recorded. For the region of interest (native heart, transplanted heart, left kidney) frames 10-56 were superimposed, time-activity curves generated and monoexponentially fitted. Furthermore, elimination half-life and intercepts were calculated. Following scintigraphic evaluation the animals were killed and graft as well as native hearts excised for histological examination. The uptake of the tracer identified severe grades of rejection. Elimination half-life of the tracer was twice as long from hearts with mild rejection and more than 14 times as long in severe rejection compared with no rejection. Elimination half-life and amplitude did not permit discrimination between grades 1, 2 and 3 a, but significantly decreased in groups 3 b and 4. This method therefore seems to be a valuable tool for the noninvasive detection of severe acute cardiac allograft rejection. Since fatty acid metabolism is clearly stress-dependent it remains to be seen whether this method allows detection of earlier rejection in loaded hearts.

Cardiac troponin I, creatine kinase, and creatine kinase MB activity were tested in serial blood samples from 15 patients with first-time Q wave acute myocardial infarction (2 anterior and 13 inferior wall infarctions). All patients received intravenous thrombolytic therapy. Cardiac troponin I and creatine kinase MB activity were compared with scintigraphic estimates of myocardial scar (single photon emission computed tomography [SPECT] with 99mTechnetium-isonitrile [Tc-sestamibi]) on late images at rest about 5 weeks after myocardial infarction. Scintigraphic defect sizes ranged from 3.2 to 41.2% (median: 27.3%) of left ventricle. Cardiac troponin I increased and peaked in parallel with creatine kinase MB activity, and the peak values correlated with each other (r = 0.76, p = 0.002). Troponin I stayed increased for several days longer than creatine kinase and creatine kinase MB activity. It could be detected at least until the 4th day after admission. Significant correlation coefficients were found between 99mTc-isonitrile defect sizes and areas under cardiac troponin I curves (r = 0.53, p = 0.042) and between 99mTc-isonitrile defect sizes and cumulative creatine kinase MB activity release (r = 0.64, p = 0.01). Animal studies have already shown a very close correlation between histologic infarct size and SPECT 99mTc-isonitrile defect size. Therefore, our results indicate that cardiac troponin I release in patients with acute myocardial infarction is also correlated with infarct size.

A uniform protocol for thallium scintigraphy of the myocardium has been issued in Austria to avoid difficulties in interpreting results and to avoid repeated examinations to save expenses and radiation burden. From the beginning of 1995 this protocol will be used in the Austrian departments of Nuclear Medicine, differences from this protocol have to be mentioned separately. In this protocol the procedure of examination, bicycle and pharmacological stress testing and vasodilatation, acquisition techniques for planar and SPECT imaging, data processing and quality control of devices are defined.

Background: This study compared clinical-chemical estimates of infarct size with scintigraphic estimates of myocardial scar in patients with first-time acute myocardial infarction (AMI)., Methods: Levels of the cardiac isoform of the contractile protein troponin T (TnT), of creatine kinase (CK), and of the isoenzyme MB of CK (CK MB) were tested in serially drawn blood samples from 21 patients (two females and 19 males; median age, 55 years). Of these 21 patients, five had anterior- and 16 had inferior-wall AMI; all patients received intravenous thrombolytic therapy. Single-photon emission computed tomography (SPECT) with technetium-99m-isonitrile (Tc-sestamibi) was performed at rest after the onset of AMI (median time, 5 weeks). Scintigraphic defects were calculated using "bull's-eye" polar coordinate maps. All patients had an uncomplicated course between discharge and myocardial scintigraphy., Results: Scintigraphic defect sizes ranged from 3.2% to 47.8% of the left ventricle (median, 27.3%). Cardiac TnT and CK MB release correlated closely with each other and with scintigraphic estimates of myocardial scar. Significant correlates were found between cardiac TnT and CK MB peak values (r = 0.87, P = 0.0001), CK MB peaks and Tc-sestamibi defect sizes (r = 0.73, P = 0.0014), and TnT peaks and scintigraphic defect sizes (r = 0.73, P = 0.0011)., Conclusions: Because animal studies have already shown a very close correlation between histologic infarct size and SPECT Tc-sestamibi defect size, our results indicate that cardiac TnT is a useful marker to assess infarct size noninvasively in man.

In an attempt to evaluate the dynamics of fatty acid metabolism after aortocoronary bypass grafting (ACBG), ten patients were investigated after ACBG by 123I-HDA myocardial scintigraphy. Tracer kinetics were followed for 90 min and compared to those of 36 nongrafted patients with different underlying heart diseases, including healthy volunteers. Regional analysis and monoexponential curve fitting were used to evaluate t1/2 (half-life of the early period of tracer elimination); biexponential curve analysis was used to calculate Ca/Cb, the ratio of a fast and a slow component of tracer elimination. Rest and stress MUGA-RNV served as discriminating parameters to discern between patient groups with normal and abnormal ventricular function. Group I (normal controls) encompassed ten patients with normal ventricular function, including three after ACBG, and group II seven patients after ACBG and with abnormal ventricular function. Group III had coronary artery disease (CAD) documented by angiography, and group IV by prior myocardial infarction (MI). Group V included patients with cardiomyopathy (CMP). Regional analysis of group II revealed no significant differences to control regions (Gr I) for t1/2 or Ca/Cb, but showed for Ca/Cb a nonsignificant shift toward group III values. However, group II differed significantly from group III and V. Three patients with normal ventricular function after ACBG showed elimination values that were all well within the range of completely normal individuals. Thus our data support the assumption that a normal function is indicative of a normal metabolism. Following myocardial fatty acid metabolism during rest might be a helpful noninvasive tool for etiologic differentiation of disturbed ventricular function.

Dipyridamole stress is favorable in patients unable to exercise maximally for 201Tl myocardial scintigraphy. Aside from an analysis of uptake defects, proper washout analysis can be limited by heart rate variations when isolated dipyridamole stress is used. Heart rate standardized 201Tl washout kinetics after a combined dipyridamole and submaximal exercise stress protocol (CDSE), feasible in elderly patients as well as in patients with peripheral artery disease, were therefore studied to investigate the 201Tl washout after CDSE in differently defined patient groups: Group I comprised 19 patients with documented heart disease and angiographically excluded coronary artery disease (CAD); group II contained 17 patients with a very low likelihood of CAD determined by both normal exercise radionuclide ventriculography and normal 201Tl uptake. Group III comprised 56 patients with a 50% pretest likelihood of CAD but normal 201Tl uptake. Mean washout values were nearly identical in all groups. Despite similar uptake patterns, however, washout standardized by CDSE was significantly lower than the normal washout values after maximal treadmill exercise. Thus an obviously lower 201Tl washout after CDSE than after maximal treadmill exercise must be considered if washout analysis criteria after dipyridamole are applied to evaluate ischemic heart disease. Nevertheless, heart rate elevation achieved by additional submaximal exercise stress seems necessary, adequate and clinically safe for standardisation of washout analysis in dipyridamole 201Tl scintigraphy.

Radionuclide ventriculography (RNV) indices of regurgitation, Fourier amplitude ratio (FAR) and additional RNV variables were prospectively compared to Doppler echocardiography (DE) in 108 consecutive patients with no or mild left ventricular regurgitation, to assess RNV accuracy in detecting regurgitation in patients with different cardiac disorders. Exclusion of left ventricular or tricuspid regurgitation allowed investigation of the FAR range at rest and during exercise in a sufficiently large appropriate reference group without regurgitation. FAR, as well as other RNV variables, failed to provide more information for the diagnosis of mild (clinically irrelevant) left ventricular regurgitation than the diagnosis upon admission alone. Despite the superiority of DE as a gold standard in the detection of mild regurgitation, at present evaluation of RNV regurgitation indices might be the only method to discover regurgitation arising during dynamic exercise.

A total of 240 survivors of one or more myocardial infarctions were consecutively admitted to perform supine exercise radionuclide ventriculography. Within 3 years after the test, 22 died; this group was compared to an age-matched control group of 22 survivors for left and right ventricular function during rest, exercise, and simultaneously assessed exercise performance as well as ECG variables. Evaluation of 3-year survival by linear discriminant analysis revealed an accuracy of 82% for discriminant models using ECG and exercise performance variables. Implementation of resting left ventricular ejection fraction and change of right ventricular ejection fraction during exercise, as well as scintigraphic presence or absence of dyskinesia, improved the accuracy of the model to 91% of correctly classified patients.

Left ventricular performance at rest and during supine symptom-limited exercise was determined by radionuclide ventriculography (RNV) in 65 subjects of the age of 65 years or older. Eleven subjects had no evidence of coronary artery disease (CAD) by history or submaximal stress ECG. In this control group left ventricular ejection fraction (LV-EF) increased from 0.62 +/- 0.09 (mean +/- SD) to 0.69 +/- 0.08 with a further increase in regional wall motion. There were 10 patients with a history of hypertension or atypical angina without infarction. Left ventricular ejection fraction (LVEF) at rest was 0.65 +/- 0.11 and showed no significant increase during exercise (mean exercise tolerance: 73 +/- 33W). Nineteen patients had an anterior infarction. LVEF at rest was 0.44 +/- 0.16 and as a group showed no change during exercise (mean exercise tolerance: 70 +/- 23W). Only two of 19 patients showed an increase of LVEF greater than 0.10. There were 19 patients with inferior infarction. LVEF at rest was 0.49 +/- 0.08 and showed also no significant change during exercise (mean exercise tolerance: 80 +/- 25W). Four of 19 patients showed an increase of LVEF in response to exercise. The five patients with two or more infarctions showed a markedly decreased resting LVEF of 0.28 +/- 0.11 with a further decline (0.22 +/- 0.09) during exercise (mean exercise tolerance: 45 +/- 32W). Therefore, age by itself does not significantly impair left ventricular ejection fraction at rest and during exercise. RNV appears as a valuable method in evaluating left ventricular performance of older patients with a similar response to exercise as in younger persons without or with comparable disease.