G. Schulz

Imaging of β-oxidation by static PET with 14(R,S)-[18F]-fluoro-6-thiaheptadecanoic acid (FTHA) in patients with advanced coronary heart disease : A comparison with 18FDG-PET and 99Tcm-MIBI SPET

14(R,S)-[18F]-fluoro-6-thiaheptadecanoic acid (FTHA) has been proposed as a PET tracer of the beta-oxidation pathway. The aim of this study was to investigate the diagnostic value of FTHA using static PET imaging in patients with ischaemically reduced left ventricular function. Twenty-one patients with angiographically proven advanced coronary heart disease were examined. All patients underwent SPET with 400 MBq [99Tcm]-2-methoxy-isobutyl-isonitrile (MIBI) for perfusion assessment and PET with 250 MBq FTHA under fasting conditions and with 150 MBq 2-[18F]-fluoro-2-deoxyglucose (FDG) following an oral glucose load. The uptake of FTHA and FDG was analysed quantitatively in 33 regions. Regional uptake was normalized to the region with highest MIBI uptake and expressed as a percentage. FTHA uptake paralleled MIBI uptake (r = 0.80) but not FDG uptake (r = 0.57). Mean FTHA uptake (38.1 +/- 16.3%) in 190 regions with severely reduced perfusion (MIBI uptake < 50%, mean uptake 36.8 +/- 9.4%) was significantly lower compared to FDG uptake (54.6 +/- 25.0%). FTHA uptake was preserved (> or = 70%) in 8 of 52 (13%) regions only with severely reduced perfusion but preserved glucose metabolism (FDG uptake > or = 70%). The similarity between FTHA and MIBI uptake suggests that static PET imaging with FTHA is of limited value when distinguishing between ischaemic or hibernating myocardium and scar. The underestimation of viability may be caused both by the dependence of uptake on flow and the suppression of beta-oxidation in regional chronic ischaemia under fasting conditions.

DIAGNOSTIK DER MYOKARDVITALITAT BEI CHRONISCHER MYOKARDISCHAMIE MIT NUKLEARMEDIZINISCHEN VERFAHREN

Nichtinvasive Verfahren zur Vitalitätserkennung haben in den letzten Jahren zunehmende Bedeutung bei der Frage der präoperativen Risiko- und Nutzenabschätzung von koronarrevaskularisierenden Verfahren erhalten. An nuklearmedizinischen Untersuchungsmethoden haben sich im klinischen Alltag die Thallium-201-Myokardszintigraphie sowie die Positronen-Emissions-Tomographie mit Fluor-18-Fluorodeoxyglukose bewährt. Neben der Vorhersage der Reversibilität von regionalen Wandbewegungsstörungen und damit auch der globalen Ventrikelfunktion erlauben beide Methoden die Identifizierung von Patientenpopulationen, die hinsichtlich ihrer Prognose am meisten von revaskularisierenden Verfahren profitieren werden. Diese Übersicht faßt den derzeitigen klinischen Stellenwert beider Methoden bei der Diagnostik der Myokardvitalität in Regionen mit chronischer Ischämie zusammen. Non-invasive methods to identify absent or persistent myocardial viability have gained increasing importance in the therapeutic management and risk stratification of patients with ischemic left ventricular dysfunction. Myocardial scintigraphy using thallium-201 and positron emission tomography with metabolic imaging of myocardial glucose metabolism, using fluorine-18 fluoro-deoxyglucose, are today the most widely used nuclear methods for the assessment of myocardial viability. Besides the prediction of reversible regional and global myocardial dysfunction following coronary revascularization, both methods have demonstrated the ability to identify patient subgroups who will benefit most with regard to cardiac prognosis and survival and those patients in whom coronary revascularization has a limited effect with regard to survival and cardiac events. This short review summarizes the clinical impact of both imaging modalities on todays diagnostic approach in patients with ischemic left ventricular dysfunction.