Myocardial metabolism

Myocardial ischemia and infarction cause abnorma myocardial metabolism, decreased left ventricular (LV) systolic function, diastolic dysfunction, congestive heart failure, and decreased survival. Consequently, revascularization techniques, either surgical or catheter based, have become integral to treatment of severe ischemic heart disease. 

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Ter-Pogossian MM, Klein MS, Markham J, Roberts R, Sobel BE. Regional assessment of myocardial metabolic integrity in vivo by positron-emission tomography with 1 IC-labeled palmitate. Circulation 1980 61 242-255... 

Sobel BE, Geltman EM, Tiefenbrunn AJ, Jaffe AS, Spadaro JJ, Jr., Ter-Pogossian MM et al. Improvement of regional myocardial metabolism after coronary thrombolysis induced with tissue-type plasminogen activator or streptokinase. Circulation 1984 69 983-990... 

Gould KL, Yoshida K, Hess MJ, Haynie M, Mullani N, Smalling RW. Myocardial metabolism of fluorodeoxy-glucose compared to cell membrane integrity for the potassium analogue rubidium-82 for assessing infarct size in man by PET. J Nucl Med 1991 32 1-9... 

Herrero P, Gropler RJ. Imaging of myocardial metabolism. J Nucl Cardiol 2005 12 345-358... 

Andersson B, Lomsky M, Waagstein F. The link between acute haemodynamic adrenergic beta-blockade and long-term effects in patients with heart failure. A study on diastolic function, heart rate and myocardial metabolism following intravenous metoprolol. Eur. Heart J. 1993 14 1375-85. 

D. Neglia, G. Sambuceti, P. lozzo, A. L Abbate, H.W. Strauss, Myocardial metabolic and receptor imaging in idiopathic dilated cardiomyopathy, Eur. J. Nucl. Med. 29 (2002) 1403-1413. 

Avogaro, A., Nosadini, R., Doria, A., Fioretto, P., Velussi, M., Vigorito, C., Sacca, L., Toffolo, G., Cobelli, C., Trevisan, R., et al. 1990. Myocardial metabolism in insulin-deficient diabetic humans without coronary artery disease. Am J Physiol 258(4 Pt 1) E606-E618. 

Pieper GM, Gross GJ. Salutary action of nicorandil, a new antianginal drug, on myocardial metabolism during ischemia and on postischemic function in a canine preparation of brief, repetitive coronary artery occlusions comparison with isosorbide dinitrate. Circulation 1987 76(4) 916-28. 

Figure 19-1 a Normal and ischemic myocardial metabolism of glucose. A total production of 36 moles of ATP results from the aerobic catabolism of 1 mole of glucose and use of NADH and FADH. in the oxidative phosphorylation process in mitochondria. When oxygen is not available, NADH and FADH levels rise and shut off the tricarboxylic acid (TCA) cycle. Pyruvate is converted to lactate. Only 2 moles of ATP are formed from anaerobic catabolism of 1 mole of glucose. (Adapted from Giuliani, E. R., ei al. Cardiology Fundamentals and Practice, 2nd ed. By permission of the Mayo Foundation, Rochester, MN.)... 

Sheu et al. (586) compared the effects of ionic monomer diatrizoate and nonionic monomer iohexol on coronary hemodynamics and myocardial metabolism. In dog hearts, the intracoronary injection of iohexol produced an increase in myocardial contractibility, aortic systolic pressure, and myocardial oxygen consumption. In contrast, the injection of diatrizoate produced a decrease in these parameters. This difference between ionic and nonionic contrast media was significant. Nevertheless, the degree of increased coronary blood flow after coronary injection was similar for both agents. 

Bagger JP, Botker HE. Thomassen A, Nielsen TT. Effects of ranolizine on ischemic threshold, coronary sinus blood flow, and myocardial metabolism in coronary artery disease. Cardiovasc Drugs Ther 1997 11 479M84. 

An insulin infusion should be considered for severe cases of calcium channel blocker toxicity." Case reports suggest that an intravenous bolus of regular insulin (0.5-1 units/kg) with 50 mL dextrose 50% (0.25 mg/kg for children) followed with a continuous infusion of regular insulin (0.5-1 units/kg per hour) may improve myocardial contractility. The effect of insulin is presently unclear, but it may improve myocardial metabolism that is adversely affected by calcium channel blocker overdoses, such as decreased cellular uptake of glucose and free fatty acids and a shift from fatty acid oxidation to carbohydrate metabolism. This insulin regimen is titrated to improvement in systolic blood pressure over 100 mm Hg and heart rate... 

Tracers used for assessment of myocardial metabolism are selected based on the type of metabolism of interest EDO traces glucose metabolism, ["Cjpalmitate traces mitochondrial fatty acid metabolism, and ["Cjacetate is an indirect marker for myocardial oxygen consumption, allowing assessment of ventricular performance. [ CjPalmitate is a useful marker for normal myocardial oxygen consumption because baseline energy needs of the myocardium... 

Coronary blood flow is influenced by multiple factors however, the caliber of the resistance vessels delivering blood to the myocardium and MVO2 are the prime determinants in the occurrence of ischemia. The anatomy of the vascular bed will affect oxygen supply and, subsequently, myocardial metabolism and mechanical function. 

Despite difficulties in determining the precise mechanism of action of drugs possessing calcium inhibitory activity, these compounds exert potent negative inotropic, chronotropic and dromotropic effects upon cardiac tissues. They are excellent coronary and peripheral vasodilators and preserve myocardial metabolism while preventing mitochondrial swelling during cardiac ischemia. Their antiarrhythmic activity in intact animals and isolated tissue preparations is closely linked to their ability to inhibit the slow inward calcium current, interfere with transmembrane sodium ion flux, and indirect effects. 

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