Related Experiment Videos
Effects of nitroglycerin on transmural energy metabolism in the underperfused canine heart
Insights
Nitroglycerin can be dangerous for underperfused hearts with coronary stenosis. It may worsen energy metabolism by reducing coronary perfusion pressure, highlighting risks in specific cardiac conditions.
Area of Science:
- Cardiovascular Physiology
- Cardiac Metabolism
- Pharmacology
Background:
- Myocardial underperfusion due to coronary stenosis impairs energy metabolism.
- The effects of nitroglycerin on compromised coronary circulation require careful evaluation.
Purpose of the Study:
- To investigate the impact of nitroglycerin on hemodynamics and myocardial energy metabolism during acute coronary stenosis in a canine model.
- To determine the safety and efficacy of nitroglycerin under conditions of reduced coronary perfusion pressure.
Main Methods:
- Induction of acute coronary stenosis to achieve 40% of control coronary perfusion pressure in canine hearts.
- Administration of nitroglycerin via intracoronary and intravenous routes at varying doses.
- Monitoring of hemodynamic parameters, coronary blood flow, and myocardial high-energy phosphate and lactate levels.
Main Results:
- Underperfusion significantly depleted myocardial high-energy phosphates, particularly in the inner layer.
- Low-dose intracoronary nitroglycerin had no direct effect on energy metabolism.
- Higher-dose intravenous nitroglycerin worsened hemodynamics and myocardial energy metabolism by reducing coronary perfusion pressure.
- Releasing constriction to maintain coronary perfusion pressure improved metabolism without increasing coronary blood flow.
Conclusions:
- Nitroglycerin administration can be detrimental in underperfused myocardium caused by severe, undilatable coronary stenosis.
- The drug's vasodilatory effects may dangerously lower coronary perfusion pressure, exacerbating metabolic dysfunction.
- Caution is advised when using nitroglycerin in patients with critical coronary artery disease and autoregulated flow.
Abstract:
Effects of nitroglycerin on hemodynamics and transmural distribution of myocardial metabolites were studied at 40% of control coronary perfusion pressure induced by acute coronary stenosis in the canine heart. At 40% of coronary perfusion pressure, high energy phosphate (ATP, creatine phosphate) contents significantly diminished in all layers, especially in the inner layer. A 0.3 micrograms/kg/min intracoronary infusion of nitroglycerin showed no direct effects on energy metabolism in the underperfused myocardium. A 3 micrograms/kg/min i.v. administration of the drug under fixed coronary constriction resulted in decrease in left ventricular peak systolic pressure and systemic blood pressure, and further decrease in coronary perfusion pressure and coronary blood flow. Left ventricular end diastolic pressure and ST-segment of the epicardial ECG were elevated. High-energy phosphate contents further decreased while inorganic phosphate and lactate showed an increase. Under these conditions, release of the constriction sufficient for retention of the coronary perfusion pressure at about 40 mm Hg resulted in significant improvement of the myocardial energy metabolism without a further increase in coronary blood flow. The results suggest that when the myocardium is underperfused due to undilatable stenotic vessels with maximum autoregulation of the regional flow, it may be dangerous to administer nitroglycerin in a dose sufficient to produce a large decrease in coronary perfusion pressure.