Coronary Hemodynamics And Fractional Flow Reserve Flashcards
What is the primary determinant of coronary blood flow control?
a) Blood pressure
b) Heart rate
c) Local metabolites like adenosine and nitric oxide
d) Myocardial contractility
c) Local metabolites like adenosine and nitric oxide
What does the coronary flow reserve (CFR) measure?
a) The ratio of maximal coronary flow to resting coronary flow
b) The pressure difference across a coronary artery
c) The heart rate during maximal hyperemia
d) The change in blood pressure during exercise
a) The ratio of maximal coronary flow to resting coronary flow
Which of the following is a physiological cause of decreased CFR?
a) Increased myocardial contractility
b) Progressive obstruction of a coronary artery
c) Increased heart rate
d) Decreased systemic blood pressure
b) Progressive obstruction of a coronary artery
Fractional Flow Reserve (FFR) is based on which principle?
a) Changes in heart rate are proportional to blood flow
b) Resistance changes with vessel diameter
c) Changes in pressure are proportional to changes in blood flow when resistance is constant
d) Blood flow remains constant despite pressure changes
c) Changes in pressure are proportional to changes in blood flow when resistance is constant
What is the current FFR threshold used in clinical practice?
a) 0.75
b) 0.80
c) 0.85
d) 1.00
b) 0.80
Which of the following is NOT a scenario in which FFR is shown to be useful?
a) Left main lesions
b) Nonculprit lesions in acute coronary syndromes
c) Bifurcation lesions
d) Single-vessel coronary artery disease
d) Single-vessel coronary artery disease
What does FFR correlate with?
a) Maximum myocardial blood flow in the absence of stenosis
b) The ratio of maximal blood flow to basal blood flow
c) Maximum myocardial blood flow in the presence of stenosis compared to normal vessel flow
d) The difference between resting and maximal coronary pressure
c) Maximum myocardial blood flow in the presence of stenosis compared to normal vessel flow
What percentage of myocardial oxygen demand is used by systolic wall tension?
a) 50%
b) 30%
c) 75%
d) 15%
b) 30%
Which of the following is NOT a determinant of myocardial oxygen demand?
a) Preload
b) Afterload
c) Myocardial wall thickness
d) Arterial-venous oxygen difference
d) Arterial-venous oxygen difference
How much of the cardiac output does the heart receive through the coronary arteries when at rest?
a) 10%
b) 25%
c) 5%
d) 50%
c) 5%
What is the approximate basal oxygen extraction rate of the myocardium?
a) 50%
b) 25%
c) 75%
d) 90%
c) 75%
What is unique about the oxygen consumption of the heart compared to other organs?
a) The heart has the lowest oxygen consumption per tissue mass
b) The heart has the highest arterial-venous oxygen difference
c) The heart receives the most oxygenated blood
d) The heart’s oxygen consumption equals that of skeletal muscle at rest
b) The heart has the highest arterial-venous oxygen difference
Which of the following factors directly affects wall tension?
a) Basal metabolic rate
b) End-diastolic volume
c) Oxygen saturation in the coronary sinus
d) Oxygen extraction rate
b) End-diastolic volume
Under basal conditions, the myocardium extracts approximately how much of the delivered oxygen?
a) 90%
b) 50%
c) 75%
d) 30%
c) 75%
How does the heart primarily meet increased metabolic demands?
a) Increasing oxygen extraction
b) Shifting to anaerobic metabolism
c) Increasing coronary blood flow
d) Decreasing basal metabolic rate
c) Increasing coronary blood flow
What is the primary controller of coronary blood flow in the absence of obstructive coronary artery disease (CAD)?
a) Changes in oxygen consumption
b) Resistance in the microvasculature (small arteries and arterioles)
c) Arterial-venous oxygen difference
d) Heart rate and preload
b) Resistance in the microvasculature (small arteries and arterioles)
What happens to microvascular resistance in the presence of hemodynamically significant epicardial disease?
a) It decreases at baseline to maintain coronary blood flow
b) It increases to prevent further obstruction
c) It remains unchanged
d) It increases to support greater oxygen extraction
a) It decreases at baseline to maintain coronary blood flow
What limits the myocardium’s ability to increase coronary flow in response to increased demand when there is obstructive epicardial disease?
a) Decreased microvascular resistance at baseline
b) Decreased coronary sinus oxygen saturation
c) Increased heart rate and afterload
d) Increased anaerobic metabolism
a) Decreased microvascular resistance at baseline
Why can’t the heart significantly increase oxygen extraction during increased demand?
a) The heart already extracts a high percentage of delivered oxygen
b) The heart relies primarily on anaerobic metabolism
c) The coronary arteries limit oxygen extraction
d) The basal metabolic rate limits oxygen consumption
a) The heart already extracts a high percentage of delivered oxygen
During which phase of the cardiac cycle does coronary blood flow primarily occur?
a) Systole
b) Diastole
c) Both systole and diastole equally
d) Isovolumetric contraction
b) Diastole
Which coronary artery has the greatest diastolic predominance in blood flow?
a) Right coronary artery
b) Left anterior descending artery
c) Circumflex artery
d) Left circumflex artery
b) Left anterior descending artery
What is the reason for greater diastolic predominance of flow in the left coronary artery compared to the right?
a) The left ventricle has lower compressive forces than the right ventricle
b) The compressive forces of the left ventricle are greater than those of the right ventricle
c) The right ventricle is more relaxed during diastole
d) The right coronary artery has more branches
b) The compressive forces of the left ventricle are greater than those of the right ventricle
What percentage of blood flow in the left anterior descending artery occurs during diastole?
a) 50%
b) 100%
c) 85%
d) 25%
c) 85%
Why does myocardial ischemia worsen during tachycardia?
a) Increased oxygen demand is met by decreased coronary blood flow
b) Diastole is shortened, reducing oxygen supply while demand increases
c) Systole is prolonged, reducing overall coronary blood flow
d) The right ventricle compresses the coronary arteries more during tachycardia
b) Diastole is shortened, reducing oxygen supply while demand increases
How does blood flow in the right coronary artery differ from the left anterior descending artery?
a) Flow in the right coronary artery occurs more in systole than in diastole
b) Right coronary artery flow is more or less equal in systole and diastole
c) Right coronary artery flow is greater during diastole than in systole
d) Right coronary artery flow is minimal compared to the left
b) Right coronary artery flow is more or less equal in systole and diastole
What is the term used to describe the heart’s ability to maintain coronary blood flow despite changes in perfusion pressure?
a) Afterload regulation
b) Vasoconstriction
c) Autoregulation
d) Contractility control
c) Autoregulation
Over what range of perfusion pressures does autoregulation maintain consistent coronary flow?
a) 40 to 120 mm Hg
b) 60 to 150 mm Hg
c) 50 to 140 mm Hg
d) 70 to 160 mm Hg
b) 60 to 150 mm Hg
What happens to coronary blood flow in the setting of maximum vasodilation of resistance vessels?
a) It is maintained by autoregulation
b) It varies linearly with perfusion pressure
c) It decreases despite increased perfusion pressure
d) It becomes independent of perfusion pressure
b) It varies linearly with perfusion pressure
Why is autoregulation particularly important in the presence of epicardial coronary stenoses?
a) It ensures the heart reduces oxygen demand
b) It helps maintain coronary blood flow despite decreased perfusion pressures
c) It increases resistance in the coronary arteries
d) It limits blood flow to areas without stenosis
b) It helps maintain coronary blood flow despite decreased perfusion pressures
What is the effect of coronary resistance vessel vasodilation on autoregulation?
a) Autoregulation becomes more effective
b) Autoregulation is overridden, and blood flow depends on perfusion pressure
c) Autoregulation continues unaffected
d) Blood flow decreases due to increased vascular resistance
b) Autoregulation is overridden, and blood flow depends on perfusion pressure
What would happen to coronary blood flow if perfusion pressures drop below 60 mm Hg without autoregulation?
a) Coronary blood flow would remain stable
b) Coronary blood flow would decrease
c) Coronary blood flow would increase
d) Blood flow would cease entirely
b) Coronary blood flow would decrease
What is the term for the ratio of maximal coronary flow to resting coronary blood flow?
a) Fractional Flow Reserve (FFR)
b) Coronary Flow Reserve (CFR)
c) Oxygen Extraction Ratio (OER)
d) Cardiac Output Reserve (COR)
b) Coronary Flow Reserve (CFR)
What primarily controls coronary blood flow?
a) Neural influences
b) Release of local metabolites like adenosine or nitric oxide
c) Changes in heart rate
d) Blood pressure fluctuations
b) Release of local metabolites like adenosine or nitric oxide
Which of the following is the most potent coronary vasodilator?
a) Acidosis
b) Hypercapnia
c) Hypoxia
d) Neural stimulation
c) Hypoxia
How is maximal coronary blood flow typically achieved in clinical medicine?
a) By increasing blood pressure
b) Through intracoronary or intravenous administration of adenosine
c) By inducing hypercapnia
d) By neural stimulation
b) Through intracoronary or intravenous administration of adenosine
Which of the following agents is NOT typically used to increase coronary blood flow?
a) Papaverine
b) Nitroglycerin
c) Dopamine
d) Regadenoson
c) Dopamine
Which factor has a relatively minor influence on coronary blood flow?
a) Neural influences
b) Local metabolite release
c) Hypoxia
d) Vasodilator agents
a) Neural influences
What happens to the ratio of maximal blood flow to basal blood flow with progressive obstruction of an epicardial coronary artery?
a) It increases
b) It decreases
c) It remains unchanged
d) It fluctuates unpredictably
b) It decreases
What tool is used to measure coronary flow reserve (CFR) in clinical practice?
a) A Doppler ultrasound
b) A coronary catheter with a pressure transducer
c) A 0.014-inch guidewire with a 12-MHz piezoelectric transducer
d) An external EKG monitor
c) A 0.014-inch guidewire with a 12-MHz piezoelectric transducer
Where is the guidewire placed when measuring CFR?
a) In the aorta
b) Proximal to the coronary lesion
c) Distal to the coronary lesion
d) In the left ventricle
c) Distal to the coronary lesion