Validation of a dual-isotope technique using 123I-MIBG and 201Tl in the assessment of sympathetic reinnervation following heart transplantation: phantom and patient studies.

Dual-isotope studies using 123I and 201Tl allow the assessment of sympathetic reinnervation in patients following heart transplantation. 123I-meta-iodobenzyl guanidine (123I-MIBG) serves as a tracer of the integrity of the sympathetic nervous system. 201Tl is used for landmarking to allow better delineation of the myocardium due to faint 123I-MIBG accumulation in heart transplants. The aim of this study was to evaluate the influence of parameters such as crossover, attenuation and the 123I/201TI activity ratio on the assessment of the myocardial 123I-MIBG uptake ratio using phantom and patient studies. Crossover was calculated using the ratio: 201TI counts in the 123I energy window/201Tl counts in the 201Tl window. Phantom studies were performed using a rectangular phantom (RP) and a cardiac phantom (CP). The mean crossover from the 201Tl to the 123I energy window was 11.48% (RP) and 11.13% (CP). Depending on attenuation in water (depth of water 0-5 cm), crossover increased from 10.92 to 15.85% (RP) and from 11.05 to 15.79% (CP). In order to confirm that the experimental crossover results were equivalent to those obtained in patient studies, 15 patients underwent myocardial scintigraphy. After injection of 201Tl, a simultaneous dual-window acquisition was performed to assess crossover from the 201Tl to the 123I window. The mean crossover was 15.35%, as high as the crossover assessed in phantom studies, taking into account attenuation and scatter caused by the chest wall. In order to reduce 201Tl crossover, the 123I activities were six times as high as the 201Tl activities.(ABSTRACT TRUNCATED AT 250 WORDS)

[Multiparametric analysis using radionuclide ventriculography in the assessment of left ventricular function following heart transplantation]. / Multiparameteranalyse mittels Radionuklidventrikulographie in der Beurteilung der linksventrikulären Funktion nach Herztransplantation.

Left ventricular systolic and diastolic performance was evaluated by radionuclide angiography in 17 patients following cardiac transplantation and compared with normal persons. Both groups performed supine bicycle exercise during the investigation, the control group at 102 +/- 73 W and the transplanted patients at 61.2 +/- 15 W. The ejection fraction increased in the normal persons from 61 +/- 8 to 69 +/- 10% whereas in the transplanted patients it did not increase significantly. There were no relevant changes in systolic parameters during exercise in the transplant recipients. The changes in diastolic parameters were significantly smaller in transplant patients than in normals. After correction for heart rate-induced changes a significantly different time course of the systolic-diastolic sequence during the cardiac cycle became evident in the transplanted group at rest. During exercise the systolic-diastolic sequence during the cardiac cycle became similar in both groups. It is concluded that the reduced exercise capacity of patients in the late phase after cardiac transplantation is partially due to the absence of an EF increase and a limitation of diastolic reserve during exercise.

Noninvasive assessment of left ventricular performance following transluminal coronary angioplasty.

We studied 36 patients with successful transluminal coronary angioplasty (group 1) noninvasively using exercise electrocardiography, exercise T1-201 myocardial scintigraphy and equilibrium radionuclide ventriculography before and 3-5 days after the procedure. Six patients who underwent aortocoronary-bypass surgery (group 2) and 10 patients with stable angina pectoris (group 3) served as controls. All patients had arteriographically documented coronary artery disease at least in one major coronary vessel (stenosis greater than or equal to 70%). In group 1, average coronary stenosis was 81.1 +/- 8.4% before dilatation and 44 +/- 13.7% after the procedure (P less than 0.001). Ischemia score in the exercise electrocardiography decreased from 2.4 +/- 2.7 before dilatation to 0.4 +/- 0.8 after the procedure (P less than 0.001). Myocardial perfusion in computerized T1-201 myocardial scintigraphy 5-10 min after exercise expressed as vitality index (the ratio of T1-201 uptake in the ischemic region to the region of maximal uptake in the same image analyzed carefully in the same view in 2 studies) increased from 72.9 +/- 8.4% before dilatation to 79.9 +/- 11.7% after the procedure (P less than 0.001). Ejection fraction at rest increased from 47.2 +/- 9.2% to 51.0 +/- 9.7% (P less than 0.001) and during exercise from 39.9 +/- 10.5% to 49.4 +/- 10.9% (P less than 0.001) before and after the procedure. In group 2, noninvasive studies showed a tendency to improvement after surgery. In group 3 no significant changes were noted. We conclude that transluminal coronary angioplasty improves both coronary perfusion to ischemic areas supplied by critical coronary artery stenoses and left ventricular function, especially during exercise, if luminal diameter is dilated by greater than 20%.