Extended functional relevance of significant coronary stenoses visualized by TI-201 Myocard SPECT: additional information obtained from reinjection studies in the presence of collaterals

Abstract

A second Tl-201 injection under resting conditions is able to improve differentiation between myocardial scar and ischemia compared to simple redistribution imaging. The aim of this study was to evaluate the dependence of this fill-in effect on the degree of stenosis and the presence of collaterals. SPECT studies under exercise, redistribution (RD, 4 h p.i.) and reinjection (RI, 24 h p.i.) conditions were performed in 62 patients with 132 stenotic vessels (50 LAD, 35 LCX, 47 RCA). The left ventricle was divided into 17 segments and for each segment, the results of angiography and scintigraphy were independently classified by two pairs of observers. From angiography, the degree of stenosis, the segments dependent on this vessel and the degree of collateralization were classified. Further wall motion abnormalities and the myocardium supplied by each of the coronary arteries were determined. Based on the scinitigraphy all segments were scored according to their perfusion in the stress, RD and RI study. The perfusion score (PS) range from 0 to 3.

43 of the “> 90% narrowed” vessels were collateralized (56%), but only 2 of the 56 “< 90% narrowed” vessels were collateralized (3.6%). 39 of the collateralized stenoses showed a fill-in effect (91%), but only 3 of the not collateralized (3%). The dependence of fill-in effect, collateralization and stenosis > 90% was highly significant (Chi²-test: < 0.0001%). In our patient group, only in vessels with stenoses > 90% was there a benefit from the reinjection study. The fill-in effect was closely correlated to the presence of collaterals. In these cases, the fill-in may be an indication for hibernating myocardium.

Zusammenfassung

Für die Indikationsstellung revaskularisierender Maßnahmen ist es von besonderer Bedeutung, die Vitalität eingeschränkt perfundierter Myokardbezirke zu kennen, um beurteilen zu können, ob der einzelne Patient von einem entsprechenden Eingriff zur Perfusionsbesserung profitiert. Die Tl-201 SPECT-Untersuchung kann diese Diskrimination leisten, jedoch zeigen neuere Untersuchungen, daß sie im Vergleich zur Positronenemissionstomographie, die direkt myokardiale Stoffwechselprozesse lokalisiert nachweist, bei einem nicht unerheblichen Anteil zu falsch negativen Ergebnissen führt [7]. Um die Sensitivität zu erhöhen, wurden sogenannte Reinjektionsstudien eingeführt [4,12].