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Evaluation of myocardial and coronary blood flow
1. EVALUATION OF MYOCARDIAL & CORONARY BLOOD FLOW
& ITS ROLE IN CORONARY INTERVENTION
PRESENTED BY : DR SAYAR AHMAD PANDIT ,SR2 CARDIOLOGY LPSIC .
DATED: 1 MARCH 2023
2. INTRODUCTION
Fundamental concepts of coronary physiology and myocardial blood flow, once the subject of research
studies, are now used in daily clinical practice.
The adoption of invasive coronary physiologic lesion assessment before percutaneous coronary
intervention (PCI) has become routine in many catheterization laboratories (cath lab).
The rationale for the use of physiology in the cath lab is the necessity to overcome the limitation of
angiography in reflecting the true ischemic potential of a coronary luminal narrowing.
3. HOW MUCH ENERGY HEART UTILIZE ?
The total metabolism of an arrested, quiescent heart is approximately 1.5 mL/min per 100 g, as required
to support the physiologic processes not directly associated with contraction.
In contrast, a beating canine heart has MVO2 ranging from 8 to 15 mL/min per 100 g.
At rest, the rate of force development -60% of myocardial energy use;
• myocardial relaxation -15% of energy use;
• electrical activity accounts for 3% to 5%; and
• basal cellular metabolism accounts for the remaining 20% of energy use.
Any compromise in substrate availability causes the myocardium to minimize energy expenditure on
mechanical work
• divert the remaining high-energy substrates for the continued maintenance of cellular integrity, thus
setting the stage for myocardial “hibernation.”
4. DETERMINANTS OF MVO2
Heart rate
Contractile state
Tension development
Activation
Depolarization
Direct metabolic effect of catecholamines
Family history of coronary artery disease
Fatty acid uptake
Maintenance of active state
Maintenance of cell viability in basal state
Muscle shortening against a load (the Fenn
effect)
5. MEASUREMENT OF MYOCARDIAL METABOLISM
Measurement of myocardial metabolism may be performed:
noninvasively (e.g., positron emission tomography scanning) or
invasively by transmyocardial sampling techniques that involve acquisition of simultaneous arterial and
coronary venous (e.g., coronary sinus) blood.
43. CFR
Normal >3
Hypertension/ T2DM/ Hyperlipidemia 2.7± 0.64
CFR< 2.0 associated with inducible myocardial ischemia on stress testing
Changes in heart rate , BP and contractility alter CFR by changing resting basal flow or maximal
hyperemic flow