Effects of perfluorochemical hemodilution on coronary blood flow distribution in dogs.

Abstract

To determine the effect of perfluorocarbon (PFC) hemodilution on myocardial vessel capacity to autoregulate, circumflex coronary artery pressure-flow relations were studied in anesthetized dogs under three conditions: maximal vasodilatation before and after PFC; autoregulation before and after PFC with 100% oxygen supplemented with room air ventilation, and autoregulation with PFC hemodilution during either room air or 100% oxygen supplemented with room air ventilation. During coronary vasodilatation, PFC did not modify coronary conductance or zero-flow pressure. During autoregulation after PFC, the lower pressure limit of the autoregulatory pressure-flow relation was shifted leftward. This leftward shift occurred because endocardial blood flow was maintained at a lower coronary perfusion pressure with PFC while epicardial blood flow was unchanged. Endocardial blood flow was also preserved at 50% of control blood flow levels as evidenced by the higher endocardialepicardial blood flow ratio with PFC. After PFC with 100% oxygen supplemented with room air ventilation, oxygen transport increased significantly when coronary perfusion pressure was below the lower pressure limit; the effect was most prominent in the endocardial tissue layer. Thus, PFC shifts the lower pressure limit to the left because of the increased ability of the endocardial vessel to autoregulate. Consequently, PFC can be considered a useful intervention for improving endocardial oxygen transport at low coronary perfusion pressures. (Circulation 1988;78:746-753) C oronary blood flow is maintained over a wide range of coronary perfusion pressures for a given myocardial metabolic demand because of the capacity of the myocardial vessel to autoregulate. 1 At a certain point of the autoregulatory process, coronary blood flow decreases with further reductions in coronary perfusion pressure. This point has been defined as the lower pressure limit of the autoregulatory pressure-flow curve (LPL) by Klocke et al.2 These investigators have also shown that the steady-state pressure-flow relation is likely to be shifted upward and to the right with increases in myocardial oxygen demand. Pressureflow relations vary in the different myocardial layers. The LPL of the endocardial tissue layer is higher than that of the epicardium.3,4 Interventions that modify blood viscosity5 or myocardial oxygen From the Quebec Heart Institute,

Effect of estrogen replacement therapy on distribution of myocardial blood flow in female anesthetized rabbits

“…The atria were removed and the ventricles and septum were divided into subendocardial (Endo) and subepicardial (Epi) tissue layers. Radioactivity was measured as previously described (20).…”

The Quebec Heart Institute: 50 years of excellence in cardiology

“…Fundamental researchers and electrophysiologists collaborated on fruitful studies (30,31). The team dedicated to coronary circulation physiology evaluated the distribution of subendocardial coronary flow under various hemodynanic conditions and pharmacological interventions (32,33). In clinical research, cardiologists determined the diagnostic and prognostic value and limitations of the electrocardiogram during exercise stress testing (34)(35)(36).…”

Effect of angiotensin inhibition on the coronary artery lower pressure limit in anesthetized dogs

“…The atria were removed and the ventricles and septum were divided as previously described (Rouleau et al 1979). Radioactivity in reference arterial blood and in tissue samples was counted using a multichannel pulse-height analyzer (Kingma et al 1988). …”

“…Changes in the lower coronary pressure limit (LPL) occur with increases in myocardial oxygen demand relative to left ventricular (LV) pressure and volume (Rouleau et al 1999), modifications in blood viscosity (Surjadhana et al 1978), perfluorochemical hemodilution (Kingma, Jr. et al 1988), inhibition of nitric oxide synthetase (Smith and Canty 1993;Duncker and Bache 1994), and LV hypertrophy (Hoffman 1987). A coronary perfusion pressure below LPL impairs transmural distribution of blood flow and results in a lower subendocardial : subepicardial blood flow ratio (Rouleau et al 1979;Surjadhana et al 1978).…”