Physiology of the Heart

Question 1

Stroke Volume is affected by

Answer 1

Contractility
Afterload
Preload

Question 2

Increased contractility results in an ________________ stroke volume

Answer 2

Increase

Question 3

Increased pre-load results in an ___________ stroke

Answer 3

Increase

Question 4

Increased after afterload results in an ____________ in stroke volume

Answer 4

Decrease

Question 5

A failing heart has decreased systolic function due to

Answer 5

Systolic and/or diastolic dysfunction

Question 6

Equation for Stroke Volume

Answer 6

Stroke Volume = End Diastolic volume - End Systolic Volume

Question 7

Contractility (and Stroke volume) increase with

Answer 7

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

Question 8

Contractility (and Stroke Volume) decrease with

Answer 8

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

Question 9

What class of drug can decrease the contractility of the heart

Answer 9

Non-dihydropyridine Ca2+ blockers

Question 10

How does Catecholamine stimulation via B1 receptors increased stroke volume

Answer 10

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

Question 11

Preload is approximated by

Answer 11

the Ventricular End Diasytolic Volume

Question 12

Preload depends on

Answer 12

Venous tone and the Volume of circulating blood

Question 13

What class of medication can decrease the preload

Answer 13

Vasodilators such as (Nitroglycerin)

Question 14

Afterload is approximated by the

Answer 14

MAP (Mean Arterial Pressure)

Question 15

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

Answer 15

Increase, Increase, Laplace Law

Question 16

What class of medication decreases the Afterload

Answer 16

Arterial Vasodilators ( Hydralazine)

Question 17

What class of medication decreases both preload and afterload

Answer 17

ACE inhibitors and ARB’s

Question 18

How does the heart comensate for increased Afterload

Answer 18

LV hypertrophy in oder to decrease wall tension

Question 19

What is the effect of Chronic Hypertenion on MAP

Answer 19

Increases the MAP which leads to LV hypertrophy

Question 20

Myocardial Oxygen demand is increased by

Answer 20

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

Question 21

Wall tension follows which Law

Answer 21

Laplace Law

Question 22

Equation for wall tension

Answer 22

Wall tension = Pressure x Radius

Question 23

Equation for Wall Stress

Answer 23

Wall stress = Pressure x Radius / 2 x wall thickness

Question 24

Equation for Stroke Volume

Answer 24

End Diastolic Volume - End systolic volume

Question 25

Equation for Ejection Fraction

Answer 25

Stroke Volume / End Diastolic Volume

Question 26

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

Answer 26

Decreased EF in systolic HF and usually Normal in Diastolic EF

Question 27

Cardiac Output

Answer 27

Stroke Volume x HR

Question 28

Fick's Principle

Answer 28

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

Question 29

How is Cardiac Output affected in Early exercise vs late exercise

Answer 29

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

Question 30

Pulse Pressure equation

Answer 30

Systolic Blood pressure - Diastolic blood pressure

Question 31

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

Answer 31

Stroke volume, arterial compliance

Question 32

Pulse pressure is inreased in

Answer 32

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)

Question 33

Pulse Pressure is decreased in

Answer 33

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

Question 34

MAP equation

Answer 34

Cardiac Output x Total peripheral resistance

Question 35

MAP ( at resting HR) =

Answer 35

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

Question 36

Starling curve (pg 283 FA)

Answer 36

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

Question 37

What factors increase Contractility

Answer 37

Catecholamines and Positive Inotropes (Digoxin)

Question 38

What factor decrease cardiac contractility

Answer 38

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

Question 39

Pressure =

Answer 39

Volumetric flow rate x resistance

Question 40

Volumetric flow rate ( Q) =

Answer 40

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

Question 41

Resistance =

Answer 41

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

Question 42

Total resistance of vessels in series

Answer 42

Rt = R1 + R2 + R3 ...

Question 43

Total resistance of vessel in parallel

Answer 43

Rt = 1/R1 + 1/R2 +1/R3 ...

Question 44

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

Answer 44

Highest, Lowest

Question 45

What types of vessels account for the highest TPR

Answer 45

Arterioles

Question 46

What provide most of the blood storage capacity

Answer 46

Veins

Question 47

Viscosity depends mostly on

Answer 47

Hematocrit

Question 48

Viscosity increases in hyperproteinemic states such as

Answer 48

Multiple myeloma and polycythemia

Question 49

Viscosity decreases in

Answer 49

anaemia

Question 50

Compliance =

Answer 50

V/P