Coronary Circulation - Quiz 9 Flashcards
What are the Major Coronary Arteries?
Right Coronary Artery (RCA) - 85%
Left Main Coronary Artery (LM)
Left Anterior Descending (LAD)
Circumflex Artery (CX)
What is the Ramus Intermedius?
Additional Branch in people who have Trifurcation of the Left Main
37%
Do the Epicardial Arteries contribute significantly to Coronary Vascular Resistance?
No - Intramyocardial Vessels (Arterioles) contribute the most to resistance
What is Capillary Density and is it increased or decreased in the Myocardium?
Number of capillaries per unit cross sectional area.
Capillary Density is increased in the Heart
What are the major determinants of Myocardial Oxygen Demand
Metabolic Activity - HR, Contractility, Systolic Wall Tension
What are the major determinants of Myocardial Oxygen Supply?
Coronary Blood FLow
O2- Carrying Capacity
Vascular Resistance
Is O2 Consumption of the Heart at rest higher or lower than other organs?
Higher
Heart > Kidneys > Brain > Liver
Coronary Perfusion Pressure Formula?
CPP = DBP - LVEDP (or PCWP)
Is Oxygen highly extracted from blood flowing through the heart?
Yes, more than any other organ
What factors control Coronary Blood Flow?
Metabolic Control
Autoregulation
Endothelial Control of Tone
Extravascular Compression
Neural Control
Which stage of the heart cycle does the majority of coronary blood flow occur in the left ventricle?
Most blood flow during Distole b/c the muscles relax & no longer obstructs blood flow
During Systole, there’s strong compression of vessels by LV muscle
Which Layer of the Myocardium is at the greatest risk for ischemia?
Endocardium
What is Coronary Flow Reserve?
The Max increase of blood flow through Coronary Arteries above normal resting volume
4-5x more than at rest
Does Pressure Work or Volume Work cause more Heart O2 Consumption?
Pressure Work is much more costly
A significant decrease in flow happens at what degree of coronary vessel stenosis?
Critical Stenosis
60-75% Reduction
What is the final Intracellular Ion Disturbance that leads to impaired heart contraction & cell death?
Intracellular Calcium Overload
How does Myocardial Ischemia affect Systolic Function?
Akinesis - No Movement
Dyskinesis - Systolic lengthening & Post-Systolic Shortening
How does Myocardial Ischemia affect Diastolic Function?
↑LVEDP
Impaired Relaxation
↓Compliance
What is Myocardia Stunning?
Prolonged Heart Dysfunction after episode of severe Ischemia with gradual return of activity
Stunning is Completely Reversible
What is Myocardial Hibernation?
When heart function is depressed from chronic ishemia
Function can return to normal if blood blow is returned to normal in time
What are some consequences of Myocardial Ischemia?
- Systolic/Diastolic Dysfunction
- Angina
- CHF
- Pulmonary Edema
- MI
- Ventricular Rupture/VSD
- Cardiogenic Shock
- Death
What are some drugs used to treat cardiac ischemia?
Oxygen
B-Blockers
Calcium Channel Blockers
Nitrates
Antiplatelet/Anticoagulant
Analgesic
What are some Interventions used to treat cardiac ischemia?
- CABG
- Percutaneous Coronary Intervention (PCI)
- Balloon Angioplasty
- Bare-Metal Stents
- Drug-Eluting Stents
How Logn should you wait before doing elective surgery for patients w/ Drug-Eluting Stents or Bare-Metal Stents?
Drug-Eluting: 1 Year
Bare-Metal: 90 days
What are some Drugs used to reduce cardiac ischemic events during surgery?
Anesthetic Gas
B-Blockers
CC-Blockers
Statins
Alpha 2 Agonist
NTG
Should Isoflurane be used for Cardiac Surgery?
Causes Coronary Steal
What are Collateral Blood Vessels in the Heart?
New vessels that form in response to impaired coronary blood flow.
Form from pre-existing arterioles that branches b/t occluded & non-occluded arteries
What is Ischemic Preconditioning in the Heart?
Brief periods of Ischemia can be protective against subsequent prolonged ischemic injury
Anesthetic Gas: Mimics IPC
K+ATP channels play important role
What is the main way that the heart compensates for underperfusion?
Increase Coronary Blood Flow - cant extract much more Oxygen
What is Cardiac Autoregulation?
Ability of vascular network to maintain constant blood flow
Tightly coupled to Demand and is location-dependent
What serves as complimentary control of Coronary Blood Flow?
Neural Control
What are the Direct effects of Neural Control of Coronary Blood Flow?
Sympathetic Stimulation - Release norepi & Epi
What are the Indrect Effects of Neural Control of Coronary Blood Flow?
Increased metabolism activates local blood flow regulatory mechanisms to dilate vessels
What is Parasympathetic control of Coronary Blood Flow?
Releases Acetylcholine
Define Myocardial Oxygen Consumption
Volume of Oxygen consumed per minute
