Summary
The influence of coronary stenosis on resting blood flow (201Tl-uptake) and myocardial flow reserve (bicycle regometry) is studied in 18 patients with coronary disease. Severe coronary stenosis of 75–90% caused a reduced201T-u[pake both at rest and peak exercise. In contrast to this group patients with a 50–60% stenosis have a normal scintigram at rest but focal defects of201Tl-uptake at peak exercise.
Results are compared with experimental data obtained after acute coronary constriction and simultaneous coronary dilatation (myocardial flow reserve, MFR) in 12 dogs. 60% coronary constriction causes a 37% decrease of poststenotic MFR measured with tracer microspheres. Changes of transmural flow distribution (endo/epi ratio) are minor in the left ventricular free wall but significant in the poststenotic septum (endo/epi=.84).
It is concluded that even a moderate coronary stenosis of 60% not affecting resting blood flow becomes “critical” under conditions of high flow velocities.
Zusammenfassung
Bei 18 Koronarpatienten wird der Einfluß unterschiedlich schwerer Koronarstenosen auf die myokardiale Ruhedurchblutung (201Tl-Szintigraphie) und die myokardiale Durchströmungsreserve (MFR) unter Arbeitsbelastung auf dem Fahrrad-Ergometer geprüft. Koronarstenosen von 75–90% vermindern die myokardiale201Tl-Aufnahme sowohl in Ruhe als auch unter Belastung. Dagegen ist das Szintigramm bei 50–60% iger Stenose in Ruhe normal, bei Belaastung aber pathologisch.
Die Ergebnisse werden mit dem Befund bei akuter experimenteller Koronarstenose bei 12 Hunden verglichen. Bei 60%iger Koronarstenose und Koronardilatation fällt die MFR im abhängigen Bereich um 37%. Das Verhältnis von Innenschichtzur Außenschichtdurchblutung ändert sich in der freien Wand des linken Ventrikels wenig, fällt aber im drosselabhängigen Bereich des Septums auf 0,84.
Die klinischen und experimentellen Befunde zeigen, daß eine nur mittelgradige Koronarstenose von 60% in Ruhe die myokardiale Durchblutungsverteilung nicht beeinflußt, bei hoher Strömungsgeschwindigkeit unter Belastung dagegen zur “kritischen” Stenose wird.
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Wirth, R.H., Brückner, U.B., Keller, K. et al. Effects of moderate coronary stenosis on myocardial flow reserve in man and in the dog. Basic Res Cardiol 74, 351–360 (1979). https://doi.org/10.1007/BF01908389
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DOI: https://doi.org/10.1007/BF01908389