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Cardiology - FA > Physiology of the Heart > Flashcards

Physiology of the Heart Flashcards

1
Q

Stroke Volume is affected by

A

Contractility
Afterload
Preload

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2
Q

Increased contractility results in an ________________ stroke volume

A

Increase

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3
Q

Increased pre-load results in an ___________ stroke

A

Increase

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4
Q

Increased after afterload results in an ____________ in stroke volume

A

Decrease

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5
Q

A failing heart has decreased systolic function due to

A

Systolic and/or diastolic dysfunction

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6
Q

Equation for Stroke Volume

A

Stroke Volume = End Diastolic volume - End Systolic Volume

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7
Q

Contractility (and Stroke volume) increase with

A

1) Increased intracellular Calcium
2) Decreased extracellular Na+ ( decreased activity of the Na+/Ca2+ exchanger
3) Catecholamine stimulation via stimulation of Beta receptors

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8
Q

Contractility (and Stroke Volume) decrease with

A

1) Beta 1 blockade (decreased cyclic AMP)
2) Heart failure with systolic dysfunction
3) Acidosis
4) Hypoxia/ Hypercapnia (decreased Po2/ increased Pco2)

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9
Q

What class of drug can decrease the contractility of the heart

A

Non-dihydropyridine Ca2+ blockers

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10
Q

How does Catecholamine stimulation via B1 receptors increased stroke volume

A

1) Catecholamines stimulate B1 receptors resulting the Ca2+ channel phosphorylation -> Calcium ions enter channel -> Ca2+ induced Ca2+ release occurs and increases storage in sacroplasmic reticulum
2) Phospholamban phosphorylation -> active Ca2+ ATPase which increases calcium storage in sacroplasmic reticulum

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11
Q

Preload is approximated by

A

the Ventricular End Diasytolic Volume

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12
Q

Preload depends on

A

Venous tone and the Volume of circulating blood

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13
Q

What class of medication can decrease the preload

A

Vasodilators such as (Nitroglycerin)

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14
Q

Afterload is approximated by the

A

MAP (Mean Arterial Pressure)

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15
Q

Increased Afterload results in an __________ pressure which leads to _________ wall tension according to ___________ Law

A

Increase, Increase, Laplace Law

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16
Q

What class of medication decreases the Afterload

A

Arterial Vasodilators ( Hydralazine)

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17
Q

What class of medication decreases both preload and afterload

A

ACE inhibitors and ARB’s

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18
Q

How does the heart comensate for increased Afterload

A

LV hypertrophy in oder to decrease wall tension

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19
Q

What is the effect of Chronic Hypertenion on MAP

A

Increases the MAP which leads to LV hypertrophy

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20
Q

Myocardial Oxygen demand is increased by

A

1) Increased contractility
2) Increased Afterload (proportional to Arterial pressure)
3) increased Heart Rate
4) Increased diameter of the Ventricle (Increase wall tension)

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21
Q

Wall tension follows which Law

A

Laplace Law

22
Q

Equation for wall tension

A

Wall tension = Pressure x Radius

23
Q

Equation for Wall Stress

A

Wall stress = Pressure x Radius / 2 x wall thickness

24
Q

Equation for Stroke Volume

A

End Diastolic Volume - End systolic volume

25
Q

Equation for Ejection Fraction

A

Stroke Volume / End Diastolic Volume

26
Q

EF is an index of Ventricular contracility how is EF affected in Systolic vs Diastolic HF

A

Decreased EF in systolic HF and usually Normal in Diastolic EF

27
Q

Cardiac Output

A

Stroke Volume x HR

28
Q

Fick’s Principle

A

Cardiac Output = Rate of O2 consumption / ( arterial O2 content - venous O2 content)

29
Q

How is Cardiac Output affected in Early exercise vs late exercise

A

Early Exercise CO maintained by increased Heart rate and Stroke Volume
Late exercise CO maintained by Heart rate only as Stroke volume plateaus

Diastole is shortened with increased HR which decreases diastolic filling time which decreases SV which decreased CO

30
Q

Pulse Pressure equation

A

Systolic Blood pressure - Diastolic blood pressure

31
Q

Pulse pressure is directly proportional to ______________ and indirectly proportional to ______________.

A

Stroke volume, arterial compliance

32
Q

Pulse pressure is inreased in

A

1) hyperthyroidism
2) Aortic regurgitation
3) Aortic Stiffening (isolate systolic hypertension in the elderly)
4) Obstuctive Sleep Apnea ( due to increased sympathetic tone)
5) Anaemia
6) Exercise (transient)

33
Q

Pulse Pressure is decreased in

A

1) Aortic Stenosis
2) Cardiogenic Shock
3) Cardiac Tamponade
4) Advanced Heart Failure

34
Q

MAP equation

A

Cardiac Output x Total peripheral resistance

35
Q

MAP ( at resting HR) =

A

2/3 Diastolic BP + 1/3 Systolic BP = 2/3 Diastolic BP + 1/3 PP

36
Q

Starling curve (pg 283 FA)

A

Force of contraction is proportional to the End diastolic length of cardiac fibres ( preload)

37
Q

What factors increase Contractility

A

Catecholamines and Positive Inotropes (Digoxin)

38
Q

What factor decrease cardiac contractility

A

Loss of myocardium ( post MI )
Beta blockers ( acutely)
Non - dihydropyridine Ca2+ channel blockers
Dilated cardiomyopathy

39
Q

Pressure =

A

Volumetric flow rate x resistance

40
Q

Volumetric flow rate ( Q) =

A

Flow velocity (v) x cross-sectional area (A)

41
Q

Resistance =

A

Driving pressure (P) / Volumetric flow rate = 8n (viscosity ) x length / pi r ^4

42
Q

Total resistance of vessels in series

A

Rt = R1 + R2 + R3 …

43
Q

Total resistance of vessel in parallel

A

Rt = 1/R1 + 1/R2 +1/R3 …

44
Q

Capillaries have the ___________ cross - sectional are and the __________flow velocity

A

Highest, Lowest

45
Q

What types of vessels account for the highest TPR

A

Arterioles

46
Q

What provide most of the blood storage capacity

A

Veins

47
Q

Viscosity depends mostly on

A

Hematocrit

48
Q

Viscosity increases in hyperproteinemic states such as

A

Multiple myeloma and polycythemia

49
Q

Viscosity decreases in

A

anaemia

50
Q

Compliance =

A

V/P

Cardiology - FA (4 decks)

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