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Questions and Answers
What is the normal range for heart rate in beats per minute?
Which phase of the cardiac cycle involves the contraction of the right and left ventricles?
What initiates the electrical signal in the heart?
What is the average amount of stroke volume per heartbeat?
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During which phase of the heart cycle do the ventricles fill with blood?
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What distinguishes the 'lub' sound during the heart cycle?
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Which of the following describes the event of blood being ejected from the ventricles?
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What is the term used to describe the muscle tone of the arterial wall?
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Which of the following describes arteries with good muscle tone?
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What is a key factor that contributes to good perfusion in the body?
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What does a healthy lumen lining facilitate in arterial blood flow?
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How is perfusion most accurately defined?
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What blood pressure range is typically considered normal?
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What is the relationship between cardiac output and perfusion?
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Which of the following would NOT be associated with good perfusion?
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Which symptom is NOT typically associated with decreased perfusion in the periphery?
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What is a potential consequence of low perfusion to the skin?
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Which risk factor for arterial disease is considered modifiable?
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What alteration occurs in the heart due to decreased perfusion?
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What specific sign might indicate transient ischemia in the brain?
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Which of these statements about Type II diabetes mellitus is true?
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What is a classic symptom seen in peripheral ischemia?
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Which factor is a known contributor to increased circulating LDLs?
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What does an elevated serum BNP level indicate in heart failure?
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What primarily triggers the secretion of BNP?
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Which of the following is true about the relationship between BNP levels and heart failure severity?
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How do kidneys respond to ANP and BNP in the context of heart failure?
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What would a BNP level of 130 pg/ml typically indicate?
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What hormone is primarily responsible for the diuresis response in heart failure?
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What does a BNP level of 1000 pg/ml indicate?
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What physiological change is occurring at the heart during fluid overload?
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What is the purpose of using positive inotropic drugs in the treatment of heart failure?
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Which of the following is a primary characteristic of heart failure that necessitates the use of diuretics?
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How do natriuretic peptides function in the body during fluid overload?
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Which drug class is primarily used to decrease resistance to forward flow in heart failure treatment?
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What are the two types of natriuretic peptides secreted by the heart?
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Which mechanism does the natriuretic system oppose?
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When might it be necessary to decrease heart rate in heart failure management?
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What role do ACE inhibitors play in heart failure treatment?
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Study Notes
Heart Rate
- Normal heart rate: 60-100 beats per minute
- Heart rate may increase during activities like running or decrease during sleep
The Heart Cycle
-
Systole: The phase where the right and left ventricles contract and eject blood into the pulmonary artery and aorta, respectively.
- Occurs between the "lub" (closure of AV valves) and the "dub" (closure of pulmonic and aortic valves)
- Begins with an electrical signal from the SA node, spreading through the atria to the AV node and ventricles
- Depolarization of cardiac muscle cells leads to contraction and ejection of blood
- Stroke volume (SV) refers to the amount of blood ejected per contraction, averaging ~70ml/beat
-
Diastole: The phase where the right and left ventricles receive blood from the right and left atria, respectively, filling with blood.
Arterial Vasomotor Tone
- Arterial walls contain muscle cells/fibers that respond to various influences and needs of the body
- Muscular elements can constrict and dilate arteries as needed, maintaining a certain muscle tone
- Normal muscle tone results in flexible and compliant arteries, neither too constricted nor too dilated - "just right"
- Good blood pressure is often dependent on appropriate vasomotor tone of arteries
Lumen Patency
- A healthy lumen lining is smooth and patent (open), free of blockages
- This allows for smooth and uninterrupted forward blood flow
Perfusion
- Perfusion is the process of delivering oxygen and nutrients via the arterial system to tissue beds throughout the body
- Good perfusion leads to good tissue oxygenation. Good or bad perfusion is determined by factors like:
- Cardiac output
- State of arterial vessels: vasomotor tone and lumen patency
Signs and Symptoms of Good Perfusion
- Desired blood pressure: ~110/60 to 115/70 ("normal" is under 120/80)
Signs and Symptoms of Decreased Perfusion or Ischemia
-
Peripheral (mainly arteries in arms and legs):
- Diminished/absent pulses
- Delayed capillary refill (>2 sec)
- Pale, cool skin, sometimes mottled or blue-ish
- Delayed healing, potentially leading to ischemic skin ulcers
- Heart: Altered function, usually less cardiac output
- Brain: Altered level of consciousness; stroke
- Kidneys: Diminished urine output
Risk Factors of Arterial Disease
-
Non-modifiable risk factors:
- Family history (inherited tendency towards atherosclerosis or familial hypercholesterolemia)
- Advancing age (stiffer arteries)
-
Modifiable risk factors:
- Diet / obesity / sedentary lifestyle (increased LDLs circulating)
- Heavy alcohol consumption (toxic byproducts affecting arterial walls)
- Type II diabetes mellitus (increased circulating LDLs, toxic glucose molecules affecting arterial walls)
Heart Failure (HF)
- Causes: Coronary artery disease often causes HF
-
Pathophysiology: Decreased pumping ability of the heart, leading to reduced forward blood flow, resulting in the following:
- Increased preload: Fluid backs up in the circulatory system causing increased pressure
- Increased afterload: The heart has to work harder to pump blood through the stiffened vessels, leading to further weakening of the heart muscle.
- Reduced cardiac output: The heart is not effectively pumping blood to the body
-
Signs & symptoms:
- Pulmonary congestion (cough, shortness of breath, wheezing)
- Peripheral edema (edema in the legs and feet)
- Dizziness (due to decreased blood flow to the brain)
- Fatigue (lack of energy)
- Nocturia (frequent urination at night)
-
Treatment:
-
Increase strength of "pump" and forward blood flow:
- Positive inotropic drugs like digoxin
- Decrease heart rate if too high to lessen workload
-
Decrease resistance to forward flow (afterload):
- Vasodilator drugs like nitroglycerin
-
Inhibit RAAS (Renin-Angiotensin-Aldosterone System):
- ACE inhibitors
-
Decrease preload:
- Diuretics (key part of treatment because fluid overload is a major component of heart failure)
-
Increase strength of "pump" and forward blood flow:
Natriuretic Peptides
- The natriuretic system acts opposite to the RAAS, triggered by fluid overload
- It increases sodium excretion into the urine, with water following. Natriuretic peptides are "natural diuretics"
- Two substances secreted by the heart:
- Atrial natriuretic peptide (ANP) - secreted by the atria
- b-type natriuretic peptide (BNP) - secreted by the ventricles
- Both substances help increase sodium and water secretion from the kidneys to eliminate excess fluid
Diagnosis and Measurement of Severity of HF
- Gold standard: Blood test measuring BNP (b-type natriuretic peptide)
- Elevated BNP confirms HF
- High BNP levels indicate the heart is "frantically" trying to compensate for fluid overload, which is always a part of HF
- Clinical examples:
- Healthy man: BNP level = 50 pg/ml
- Mild HF: BNP = 130
- Severe HF: BNP = 1000
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Description
Test your knowledge of heart rate, the phases of the heart cycle, and arterial tone. Understand the differences between systole and diastole, as well as the factors that influence heart rate and blood flow. Get ready to dive into the intricacies of cardiovascular physiology!
