The Influence of Bradycardia and Normofrequent Ventricular Pacing on Myocardial Blood Flow and Energy Demand in Rats

Abstract

The purpose of the present study was to determine the effect of β-blockade-induced bradycardia and normofrequent ventricular pacing (VP) on regional myocardial (MBF) and cerebral blood flow (CBF) as well as on myocardial oxygen consumption (MVO₂) using colored microspheres. The MBF at sinus rhythm (SR) was 4.60 ± 1.27 ml/g/min and decreased to 3.80 ± 0.74 ml/g/min (p < 0.05) during β-blockade. The MBF was 5.10 ± 1.88 ml/g/min during VP with β-blockade. The endo-/epicardial MBF ratio during VP was significantly reduced. MVO₂ at β-blockade was significantly lower (0.21 ± 0.06 ml/g × min^–1, p < 0.05) than at SR (0.47 ± 0.15 ml/g × min^–1) and during VP with β-blockade (0.54 ± 0.14 ml/g × min^–1). Results: (i) MBF and MVO₂ are reduced with decreasing mean arterial pressure (MAP) during β-blockade-induced bradycardia, but MBF and MVO₂ are significantly increased during normofrequent VP with β-blockade despite a further reduction in MAP. (ii) The MBF ratio is constant during β-blockade but is significantly lower during normofrequent VP with β-blockade. (iii) CBF remained constant during all experimental conditions. Conclusion: Despite β-blockade, the subendocardium is jeopardized during normofrequent VP by ischemia.

d-ribose improves cardiac contractility and hemodynamics, and reduces expression of c-fos in the hippocampus during sustained slow ventricular tachycardia in rats

“…Due to the infusion of 15 ml 0.9% saline to rats in control group as well as 15 ml of D-ribose solution (450 mg/kg) to rats in treatment group at the beginning of the experiments, the mean MAP in control group (129 ± 13 mm Hg) and in D-ribose group (127 ± 10 mm Hg) was during SR significantly (p b 0.01) higher in comparison to the MAP (113 ± 11 mm Hg) of rats without fluid administration in our historic population [15]. After the induction of VT, 8 rats in the control group and 2 rats in the D-ribose group expired.…”