Non-Invasive Detection of Reduced Regional Myocardial Perfusion at Rest in Patients with Unstable Angina Pectoris: Increased Regional ^81mKr Deposition following Intravenous Injection of ⁸¹ Rb^[*]

The present study was to investigate whether combined imaging of ⁸¹ Rb and ^81mKr distributions after i.v. injection of ⁸¹ Rb at rest might improve the differentiation between ischemic and irreversibly damaged myocardium as compared to ²⁰¹TI scintigraphy at rest. In 21 patients who had undergone diagnostic cardiac catheterization for evaluation of chest pain, 148 MBq ultrapure ⁸¹ Rb were injected i.v. at rest immediately following ²⁰¹TI scintigraphy at rest. Of 14 patients with earlier myocardial infarction, 10 patients revealed decreased regional tracer uptake of ⁸¹ Rb and/or ^81mKr, compared to 12 patients with regional ²⁰¹TI uptake abnormalities. In 3 patients with unstable angina pectoris, however, an evident mismatch between either the regional ²⁰¹TI or ⁸¹ Rb distributions and the distribution of ^81mKr was observed: in contrast to the reduced uptake of ²⁰¹TI and/or ⁸¹ Rb, ^81mKr activity was increased in 3 myocardial segments with normal left ventricular performance but supplied by coronary arteries with high-grade stenoses. In patients with contraindications to exercise tests (e.g. unstable angina) ⁸¹Rb/^81mKr rest scintigraphy may therefore assist the differentiation between malperfused but potentially viable and irreversibly damaged myocardium.

Zusammenfassung

Bei 21 symptomatischen Patienten mit vorausgegangener diagnostischer Koronarangiographie wurde untersucht, ob die getrennte Erfassung der myokardialen ⁸¹Rb- und ^81mKr-Aktivitätsverteilungen nach i.v. Applikation von hochreinem ⁸¹Rb eine im Vergleich zur ²⁰¹T1-Ruheszintigraphie verbesserte Differenzierung zwischen ischämischem und irreversibel geschädigtem Myokard gestattet. Unmittelbar im Anschluß an die ²⁰¹T1-Ruheszintigraphie wurden hierzu 148 MBq ⁸¹Rb ebenfalls unter Ruhebedingungen i.v. appliziert. Bei 10 von 14 Patienten mit bekanntem Myokardinfarkt zeigte sich eine Aktivitätsverminderung von ⁸¹Rb und/oder ^81mKr im Infarktareal, mit ²⁰¹T1 bei 12 der 14 Patienten. Bei 3 Patienten mit instabiler Angina pectoris ergab sich jedoch ein »Mismatch« zwischen der myokardialen Aktivitätsverteilung von ²⁰¹T1 bzw. ⁸¹Rb einerseits und ^81mKr andererseits: im Gegensatz zur reduzierten ²⁰¹T1-bzw. ⁸¹Rb-Belegung war die ^81mKr-Aktivität in poststenotischen Myokardsegmenten (Stenosegrad >»99%«) mit angiographisch normaler linksventrikulärer Funktion vermehrt. Damit könnte die ⁸¹Rb/ ^81mKr-Ruhemyokardszintigraphie einen diagnostischen Beitrag zur Differenzierung zwischen minderperfundiertem, aber potentiell vitalem und irreversibel geschädigtem Myokard - insbesondere bei Patienten mit Kontraindikationen zur ergometrischen Belastung (z.B. bei instabiler Angina pectoris) - liefern.suffering from unstable angina; of these, 4 complained of progressive angina (frequent anginal attacks during the last 6 weeks) and 5 patients had angina at rest. Of the 9 patients with unstable angina, 4 patients gave a history of earlier myocardial infarction.

^* Supported in part by a grant from the Deutsche Forschungsgemeinschaft/Bonn within the SFB 320 »Herzfunktion und ihre Regulation«, Ruprecht-Karls-Universität Heidelberg.

• REFERENCES

• 1 Berger BC, Watson DD, Burwell LR. et al. Redistribution of thallium at rest in patients with stable and unstable angina and the effect of coronary artery bypass surgery. Circulation 1979; 60: 1114-25.
• 2 Braunwald E, Kloner RA. The stunned myocardium: prolonged, postischemic ventricular dysfunction. Circulation 1982; 66: 1146-9.
• 3 Campeau L. Grading of angina pectoris. Circulation 1976; 54: 522-3.
• 4 Goldstein RA. Wanted: Dead or alive - The search for markers of myocardial viability. J Am Coll Cardiol 1990; 16: 486-8.
• 5 Gould KL, Lipscomb K, Hamilton GW. Physiologic basis for assessing critical coronary stenosis. Instantaneous flow response and regional distribution during coronary hyperemia as measures of coronary flow reserve. Am J Cardiol 1974; 33: 87-94.
• 6 Idoine JD, Holman BL, Jones AG. et al. Quantification of flow in a dynamic phan-tom using ⁸¹Rb-^81mKr, and a Nal detector. J Nucl Med 1977; 18: 570-8.
• 7 Jones T, Matthews CME. Tissue perfusion measured using the ratio of ⁸¹Rb to ^81mKr in the tissue. Nature 1971; 230: 119-20.
• 8 Jones T, Pettit JE, Rhodes CG, Waters SL. The measurement of spleen perfusion in man: a non-invasive method using the ratio between rubidium-81 and its decay product krypton-81m. Eur J Nucl Med 1977; 02: 219-24.
• 9 Klocke FJ. Coronary blood flow in man. Prog Cardiovasc Dis 1976; 19: 117-66.
• 10 Mtiller M, Oberhausen E, Stoll HP. et al. ⁸¹Rubidium ^81mKrypton-SPECT-Untersuchungen zur Beurteilung hochgradiger Koronarstenosen. Herz/Kreislauf 1986; 03: 128-33.
• 11 Nishiyama H, Sodd VJ, Adolph RJ. et al. Intercompnrison of myocardial imaging agents: ²⁰¹T1, ¹²⁹Cs, ⁴³K, and ⁸¹Rb. J Nucl Med 1976; 17: 880-9.
• 12 Peek NF, Hegedus F, DeNardo GL, Lagunas MSolar, Berman DS. Production and characteristics of ⁸¹Rb for myocardial studies. Int J Nucl Med Biol 1978; 05: 273-8.
• 13 Schroth HJ, Bialy J, Hans FJ. et al. Determination of cerebral blood flow using an ⁸¹ Rb/ ^81mKr generator system. Nucl-Med 1990; 29: 7-12.
• 14 Shea MJ, Wilson RA, de Landsheere CM. et al. Use of short- and long-lived rubidium tracers for the study of transient ischemia. J Nucl Med 1987; 28: 989-97.
• 15 Wackers FJT, Lie KI, Liem KL. et al. Thallium-201 scintigraphy in unstable angina pectoris. Circulation 1978; 57: 738-42.
• 16 Zimmermann R, Tillmanns H, Knapp WH. et al. Regional myocardial N-13 glutamate uptake in patients with coronary artery disease: inverse post stress relation to thallium-201 uptake in ischemia. J Am Coll Cardiol 1988; 11: 549-56.