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kardiaggeiako > φυσιολογ. > Flashcards

φυσιολογ. Flashcards

1
Q

Your patient has a heart rate of 80 beats/min with a stroke volume of 62.5 mL/beat. What is her cardiac output?

A

5 L/min, as CO = SV × HR

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2
Q

State the Fick principle/equation.

A

CO = rate of oxygen consumption ÷ (arterial oxygen content - venous oxygen content)

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3
Q

What are the two ways/equations for measuring mean arterial pressure?

A

MAP = CO × total peripheral resistance (TPR); TPR (or MAP) = 1/3 systolic pressure + 2/3 diastolic pressure

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4
Q

How is pulse pressure calculated? What is it proportional to?

A

Systolic pressure - diastolic pressure; it is proportional to stroke volume (and inversely proportional to arterial compliance)

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5
Q

A marathoner has an increased stroke volume while running. What are the two parts of the equation for SV?

A

SV = cardiac output/heart rate = end-diastolic volume - end-systolic volume

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6
Q

↑ ____ and ____ maintain cardiac output (CO) in early stages of exercise. But ↑ ____ maintains CO after prolonged exercise.

A

Stroke volume, heart rate; HR (since SV plateaus)

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7
Q

During late phases of exercise, increase in cardiac output is a result of an increase in what?

A

Heart rate

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8
Q

On physical exam, a patient’s pulse pressure is found to be decreased. Name four conditions that may cause this finding in this patient.

A

Aortic stenosis, cardiogenic shock, tamponade, and advanced heart failure

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9
Q

A patient with ventricular tachycardia experiences syncope. How do the two symptoms relate to each other?

A

At high heart rates, the ventricles are unable to fill completely during diastole (preferentially shortened), causing ↓ CO and syncope

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10
Q

Name five conditions that can cause increased pulse pressure.

A

Hyperthyroidism, aortic regurgitation, aortic stiffening (elderly), obstructive sleep apnea (↑ sympathetic tone), and exercise (transient)

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11
Q

What three variables affect stroke volume?

A

Contractility, Afterload, and Preload (SV CAP)

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12
Q

Increased SV can be caused by ____ preload, ____ afterload, or ____ contractility (choices include increased/decreased).

A

Increased, decreased, increased

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13
Q

By what mechanism do catecholamines increase cardiac contractility and stroke volume?

A

Increased activity of the calcium pump in the sarcoplasmic reticulum, which increases contractility and SV

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14
Q

How does increasing intracellular calcium affect contractility (and thus stroke volume)?

A

It increases contractility

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15
Q

How does decreasing extracellular sodium affect contractility (and thus stroke volume)?

A

It decreases the activity of the sodium/calcium ion exchanger, thereby increasing contractility and SV

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16
Q

A patient on digitalis wants to know how his medicine works and how it affects his heart. Explain.

A

It blocks the sodium/potassium pump, increasing intracellular sodium, which increases intracellular calcium and contractility

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17
Q

How does β1-blockade affect contractility and stroke volume?

A

β1-blockade decreases cAMP, which decreases contractility and stroke volume

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18
Q

A patient presents with a history of congestive heart failure. How does systolic dysfunction affect contractility?

A

It decreases contractility

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19
Q

A patient with congestive heart failure has confusion and shortness of breath. Lactate levels are elevated. What is causing his symptoms?

A

Metabolic acidosis, which decreases contractility and causes volume overload

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20
Q

A woman with known COPD is admitted for pneumonia. Her O2 saturation is 81%. How is her cardiac output affected?

A

Hypoxia and hypercapnia cause a decrease in contractility and in stroke volume

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21
Q

How do calcium channel blockers affect contractility and stroke volume?

A

Non-dihydropyridine calcium channel blockers decrease intracellular calcium, which decreases contractility

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22
Q

How do anxiety, exercise, and pregnancy affect stroke volume?

A

Increase SV

23
Q

Myocardial oxygen demand is increased by what four variables?

A

Myocardial = Contractility, Afterload (proportional to arterial pressure), heart Rate, Diameter of ventricle (increased wall tension)

24
Q

A patient has decreased afterload. The myocardium responds by increasing its thickness. Explain this compensatory response

A

Thicker myocardium decreases wall tension (which is ↑ with elevated afterload) (wall tension = [pressure × radius]/[2 × wall thickness])

25
Q

____ (Preload/afterload) = ventricular end-diastolic volume. ____ (Preload/afterload) = mean arterial pressure.

A

Preload (depends on venous tone and circulating blood volume); afterload

26
Q

Would you expect nitroglycerin to decrease preload or afterload? By what mechanism? What about these questions for hydralazine?

A

Preload via venodilation; Afterload via vasodilation (hydralazine)

27
Q

A 60-year-old man mistakenly receives triple the maintenance level of IV fluids for 24 hours. Will his preload increase or decrease?

A

Increase because of increased blood volume

28
Q

A patient has chronic hypertension. How will his left ventricle compensate?

A

LV will hypertrophy to ↓wall tension (pressure × radius/2 × wall thickness) (↑MAP will ↑afterload, thereby ↑pressure & wall tension)

29
Q

ACE inhibitors and ARBs cause ____ preload and ____ afterload (choices are increased/decreased).

A

Decreased, decreased

30
Q

What vital sign may be used to approximate afterload?

A

Mean arterial pressure

31
Q

What are the two ways for measuring ejection fraction? What is the normal value?

A

EF = stroke volume/end-diastolic volume & (end-diastolic volume - end-systolic volume)/end-diastolic volume; normal ≥ 55%

32
Q

How is ejection fraction affected in systolic heart failure and diastolic heart failure?

A

EF decreases in systolic heart failure, whereas it remains normal in diastolic heart failure

33
Q

Ejection fraction is used as an indication of which cardiac parameter?

A

Contractility

34
Q

Do β-blockers increase or decrease contractility?

A

Decrease

35
Q

Does sympathetic stimulation (e.g., catecholamines) increase or decrease contractility of the heart?

A

Increase

36
Q

Does digoxin increase or decrease contractile strength?

A

Increase, similar to catecholamines

37
Q

A patient has an MI and develops dilated cardiomyopathy years later. How does all of this affect contractility of the heart?

A

Both MIs and dilated cardiomyopathies decrease cardiac contractility

38
Q

A patient has heart failure and severe hypertension. Do you treat the hypertension with a non-dihydropyridine calcium channel blocker?

A

No, as this will further reduce contractility and likely worsen the symptoms of heart failure

39
Q

A man w/heart failure enters atrial fibrillation. He is treated with digoxin instead of a non-dihydropyridine calcium channel blocker. Why?

A

Digoxin is a positive inotrope that will help to increase cardiac contractility & that will treat the arrhythmia via AV node inhibition

40
Q

What is the relationship between net changes in pressure, resistance, and flow?

A

Driving pressure (ΔP) = flow (Q) × resistance (R), which is similar to Ohm’s law (ΔV = I × R)

41
Q

• What is the equation for blood vessel resistance that incorporates variables of viscosity, length, and radius?

A

Resistance = (8 × viscosity × length)/(π × r4)

42
Q

In cardiology, by what factor does resistance increase in a vessel whose size is reduced by half?

A

16 times (resistance is inversely proportional to the radius to the fourth power)

43
Q

What is the equation for the total resistance of blood vessels in series?

A

TR = R1 + R2 + R3 and so on

44
Q

What is the equation for the total resistance of blood vessels in parallel?

A

1/TR = 1/R1 + 1/R2 + 1/R3 and so on

45
Q

What parameter does the viscosity of blood mostly depend on? What disease states increase the viscosity of blood?

A

Primarily hematocrit; polycythemia, multiple myeloma, or other hypoproteinemic states (by this logic, viscosity ↓ anemia)

46
Q

Pressure gradient drives flow from ____ (high/low) pressure to ____ (high/low) pressure.

A

High, low

47
Q

You study blood flow in a rat’s capillaries. You find that arteriolar dilators change the TPR and thus capillary blood flow. Why is this?

A

Arterioles regulate capillary flow and account for most of TPR

48
Q

How is volumetric flow rate (Q) related to flow velocity (v) and cross-sectional area (A)?

A

Q = v × A, as capillaries have the highest total cross-sectional area in the body, hence lowest flow velocity

49
Q

A patient undergoes nephrectomy. How will the patient’s cardiac output be affected?

A

Cardiac output will ↓ as organ removal results in increased in TPR, thereby causing a decrease in cardiac output

50
Q

____ (Arteries/veins) provide most of the blood storage capacity.

A

Veins

51
Q

A patient is running on a treadmill. How does her cardiac output change? Why?

A

CO increases; this is due to increased heart rate and decreased total peripheral resistance

52
Q

Narcotic overdose causes ____ (increased/decreased) cardiac output for a particular end-diastolic volume.

A

Decreased, as inotropy (and therefore contractility) decreases

53
Q

Sympathetic activity causes ____ (increased/decreased) right atrial pressure for a given cardiac output.

A

Increased

54
Q

How do catecholamines or digoxin cause increased cardiac output?

A

They increase contractility, so CO increases for a given right atrial pressure

kardiaggeiako (11 decks)

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