Standardized noninvasive assessment of myocardial free fatty acid kinetics by means of 15-(p-iodo-phenyl) pentadecanoic acid (123I-pPPA) scintigraphy: II. Clinical results.
Our results establish that myocardial regions supplied by a significantly stenosed coronary vessel can be distinguished with high statistical significance from healthy regions on account of changes in the myocardium/background ratio, i.e. a reduction of regional uptake of 15-(p-iodo-phenyl) pentadecanoic acid (pPPA). The statistical significance applies to patients with coronary artery disease (CAD), to all examined CAD areas without areas of infarction as well as to infarcted regions. Our results also confirm the suitability of labelled fatty acids, such as pPPA, for the visualization of damaged myocardial regions. The results further indicate that pPPA practically is of comparable value to 201Tl with regard to their respective qualities as 'static' imaging agents for the heart muscle. This study, with the help of a simultaneous analysis of regional myocardial perfusion rates (rMBF) and of a parameter for the metabolism of fatty acids, practised here for the first time, could demonstrate interindividual differences between patients and groups of patients with a correlation between perfusion and the utilization of pPPA in patients with CAD. The reciprocal of the rMBF, the mean transit time (MTT), was significantly prolonged after stress in patients with CAD (P less than 0.05), suggesting impaired 'microcirculation' in the patient group. The determination of elimination half-lives (T1/2) contributes little if any information towards delineation of cardiac disease entities. The wide overlap of T1/2 values between various clinical syndromes and entities with extreme standard deviations remained an annoying problem in our studies. Nevertheless, certain trends in T1/2 behaviour could be recorded, but they did not yield any statistical significances, because of the high degree of individual variability. A considerable variability of T1/2 values among healthy controls was recorded as well as intra-individually in different regions of the heart muscle. The wide range of 'normal' values rendered statistical evaluation almost, if not entirely, impossible. It appears that the high degree of variability results amongst others, from technical shortcomings in the external recording instruments, i.e. gamma cameras, as well as from the presence of interfering alternate substrates such as glucose and lactate. Nevertheless, the wide range of measured results in healthy control subjects suggests the presence of a considerable regional intra-individual heterogeneity of cardiac substrate metabolism. One must therefore accept, at least in our opinion, that T1/2 values are not sufficiently reliable as an indicator of myocardial metabolism and are of little value with respect to clinical diagnostic considerations and to prognosis as well. Possible explanations for this finding are offered and discussed in this paper.
Wieler
H
H
Department of Nuclear Medicine, Bundeswehrzentralkrankenhaus, Koblenz, Germany.
Kaiser
K P
KP
Kuikka
J T
JT
Henkel
B
B
Frank
J
J
Ladwein
K
K
D000328:Adult; D000368:Aged; D003326:Coronary Circulation / Q000502:physiology; D003327:Coronary Disease / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000503:physiopathology; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D015588:Observer Variation; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D005230:Fatty Acids, Nonesterified; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; C025391:omega-(4-iodophenyl)pentadecanoic acid