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Ischemia Miocardica e
Cardiopatia Ischemica Cronica
Raffaele De Caterina
12-12-00
Cattedra di Cardiologia
Università G. D’Annunzio Chieti
Domande preliminari -
test di autovalutazione
• Ipossia vs ischemia
• Perché nel miocardio sono quasi equivalenti
• Origine dell’ischemia miocardica (e di
organo in generale)
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The Supply/Demand Balance
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Determinants of Myocardial
Oxygen Consumption
TABLE 36-2 DETERMINANTS OF MYOCARDIAL OXYGEN
CONSUMPTION
1. Tension development
2. Contractile state
3. Heart rate
4. Shortening against a load (Fenn effect)
5. Maintenance of cell viability in basal state
6. Depolarization
7. Activation
8. Maintenance of active state
9. Direct metabolic effect of catecholamines
10. Fatty acid uptake Cattedra di Cardiologia
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Determinants of Myocardial
Oxygen Consumption
TOTAL: 6-8 cc/min/100 gm
DISTRIBUTION
Basal 20% Volume work 15%
Electrical 1% Pressure work 64%
EFFECTS ON MVO2 of 50% INCREASES IN
Wall stress 25% Heart rate 50%
Contractility 45% Volume work 4%
Pressure work 50%
The table demonstrates the dominant contribution to MVO2
made by pressure work and prominent effects of increasing
pressure work and heart rate on MVO2.
From Gould, K. L.: Coronary Artery Stenosis, New York, Elsevier, 1991, p. 8.
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The Myocardium-Vascular
Resistance Coupling
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Coronary Blood Flow Regulation
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Epicardial/Endocardial
Inhomogeneity
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Epicardial/Endocardial
Differences in Coronary Reserve
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Stenosis vs Flow
Relation between pressure reduction
across a stenosis (DP) and flow through
the stenosis (Q). Relations are shown for
concentric stenoses of 30, 50, 70, 80, and
90 per cent internal diameter. The
numbers in parentheses below each per
cent diameter stenosis represent residual
luminal cross-sectional area, calculated on
the basis of a normal internal diameter of
3 mm and cross-sectional area of 7.1
mm2. The level of flow corresponding to
basal metabolic needs is represented by
the vertical dotted line; stenosis
resistances for this level of flow are shown
as the dashed tangent lines to the
individual pressure-flow relations. In the
inset on the right, stenosis resistance (R) is
plotted as a function of degree of stenosis.
(From Klocke, F. J.: Measurements of
coronary blood flow and degree of
stenosis: Current clinical implications and
continuing uncertainties. Newsletter of the
Council on Clinical Cardiology of the
American Heart Association. Vol 7, No. 3,
July 1982.)Cattedra di Cardiologia
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Epicardial vs. Myocardial Resistances
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Lesion Diameter vs Flow
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Reactive Hyperemia
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Myocardial Consequences of
Ischemia
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The Proposed Mechanisms of
Myocardial Stunning1. Insufficient energy production by mitochondria
2. Impaired energy use by myofibrils
3. Impaired sympathetic neuronal responsiveness
4. Impaired myocardial perfusion
5. Damage to the extracellular collagen matrix
6. Decreased sensitivity of myofilaments to calcium
7. Calcium overload
8. Excitation-contraction uncoupling due to dysfunction of sar-
coplasmic reticulum
9. Generation of damaging oxygen free radicals
Modified from Bolli, R.: Postischemic myocardial stunning. In Yellon, D. M., and
Jennings, R. B. (eds.): Myocardial Protection: The Pathophysiology of Reperfusion
and Reperfusion Injury. New York, Raven Press, Ltd., 1992.
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The wavefront of myocardial
necrosis
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Ischemia and
Necrosis
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Potential Causes of
Irreversibility
High-energy phosphate depletion/cessation of anaerobic glycolysis
Catabolism without resynthesis of macromolecules
Reduced transsarcolemmal gradients of Na+ and K+
Cell Swelling
Calcium overload
Activation of phospholipases/proteases
Impaired mitochondrial function
Activation of ATPases
Catabolite accumulation (lactate, H+ (acidosis), fatty acid derivatives, free
radicals, ammonia, inorganic phosphate, etc.)
Enzyme denaturation
Membrane damage
Increased intracellular osmolarity
Cell swelling
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The
spectrum of
myocardial
ischemia
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Variable supply-demand ratios
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L’informazione con test
diagnostici
• Test da sforzo: presenza d’ischemia miocardica - non
localizzazione
• ECO basale: presenza di anomalie di contrazione (necrosi-
stunning-ibernazione)
• stress ECO: presenza d’ischemia - localizzazione - vitalità
• scintigrafia da stress (Tl201-99mTc-sestamibi):
ipoperfusioni/vitalità
• angiografia: anatomia delle coronarie
• riserva coronarica: significato funzionale di una stenosi
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Stress ECG test
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