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Flashcards in CV Week 1b Deck (172):
1

What is the primary mechanism of EC coupling? What are the 3 main steps?

CALCIUM cytosolic fluctuations

1) Ca2+ enters cell via DHPR (L-type Ca2+ channel) → activates RyR2 in SR → flux of Ca2+ into myoplasm

2) Ca2+ binds troponin → myosin binds actin → contraction

3) Ca2+ removed from myoplasm by → relaxation

2

3 mechanisms by which Ca2+ is removed from the cytoplasm

In order of most contribution:

1) SERCA2 pump
2) NCX Na+/Ca2+ exchanger
3) ATP Ca2+ pump (PMCA) - minimal contribution

3

SERCA2 pump

-pumps Ca2+ into SR, on longitudinal SR

-Ca2+ binds calsequestrin (low affinity, high capacity) in SR

-Dominant mechanism of removal of Ca2+ because longitudinal SR surrounds each myofibril (requires less energy)

-Inhibited by PLB

4

NCX located in _________

junctional domains of plasma membrane and t-tubules

5

______ muscle REQUIRES entry of external Ca2+ where as _______ muscle does not

Cardiac

Skeletal

6

Explain the bidirectional qualities of NCX

3 Na for 1 Ca

At beginning of AP (phase 0) Na+ out/Ca2+ in (depolarization)

At end of AP (phase 3/4) Na+ in/Ca2+out (repolarization, steady-state)

Maintains balance of Ca2+ entry during steady-state

7

How is NCX arrhythmogenic?

If Ca2+ released from SR when cardiac myocyte at REST (diastole) → causes 3Na+ in/1Ca2+ out → depolarization

→ delayed afterdepolarizations and arrhythmias

8

2 mechanisms of calcium homeostasis

1) NCX exchanger
2) L-type Ca2+ channel and CDI

9

Calcium Dependent inactivation (CDI)

-L-type Ca2+ channel undergoes inactivation dependent on [Ca2+] near cytoplasmic side of channel

-maintains constant SR Ca2+ content
If amount of Ca2+ in SR increases, greater CDI causes less Ca2+ to enter via L-type channel.

-If amount of Ca2+ in SR decreases, less CDI causes more Ca2+ to enter via L-type channel.

10

Sympathetic Activation → (4)

1) Positive Lusitropy: increase rate of relaxation

2) Positive Inotropy: increase contractile force

3) Positive Chronotropy: increased HR by raising pacemaker firing rate in SA node

4) Alter propagation through conduction pathways

11

Targets of PKA

1) L-type Ca2+ channel
2) RyR2
3) Phosphoalmban (PLB)
4) Troponin

12

PKA effect on L-type Ca2+ channel

Phosphorylation → increases amplitude of L-type Ca2+ current → increases size of RyR2 activation

Increase Ca2+ entry → increase quantity of Ca2+ stored in SR

→ Contributes to POSITIVE INOTROPY

13

PKA effect on RyR2 channel

phosphorylation of RyR2 → Ryr sensitized to activation by Ca2+
→ POSITIVE INOTROPY

14

PKA effect on PLB

-Association of PLB with SERCA2 inhibits Ca2+ pumping activity

-Phosphorylation → PLB dissociates from SERCA2 → relieves inhibition and increases Ca2+ pumping into SR

→ Speeds relaxation, increases the quantity of Ca2+ stored in SR

→ Both POSITIVE INOTROPY and POSITIVE LUSITROPY

15

PKA effect on Troponin

phosphorylation → speed rate of Ca2+ dissociation from actin

→ POSITIVE LUSITROPY

16

Timothy Syndrome

Other associated abnormalities?
Associated mutations?
Impact of mutations?
Outcomes?

syncope, cardiac arrhythmias, sudden death

Associated with intermittent hypoglycemia, immune deficiency, and cognitive abnormalities (autism)

De novo mutations in Cav1.2 (L-type Ca2+ channel)

→ profound suppression of voltage-dependent inactivation of Ca2+ channel → prolonged AP

→ AV block, prolonged QT intervals, polymorphic ventricular tachycardia

17

Brugada syndrome (aka sudden unexplained death syndrome)

Associated with a number of ECG alterations (revealed by administration of Class IC antiarrhythmics - Na+ channel blockers)

Mutation in cardiac Na+ channel (Nav 1.5), Transiently outward K+ channel, and L-type Ca2+ channel

→ large reduction in magnitude of L-type Ca2+ current as consequence of impaired membrane trafficking current

→ shortened AP

→ Significantly shortened Q-T intervals.

18

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)

No ECG abnormalities at rest, but abnormalities with exercise or infusion of catecholamines

Mutations in RyR2 (AD inheritance)

Mutation in calsequestrin 2 (CasQ2) (AR inheritance)

19

CPVT mutations + increased SR Ca2+ release (due to increased ___________) → ?

increased B-adrenergic receptor activation

--> Ca2+ release NOT directly triggered by L-Ca2+ current during AP plateau

--> Ca2+ release occurs after repolarization

Extrusion of Ca2+ via NCX → depolarizations that can trigger ectopic APs and initiate arrhythmias

20

Treatment of CPVT

B-blockers are not effective

-Must block aberrant Ca2+ release from RyR2

-Flecainide (class IC antiarrhythmic) possible therapy

21

Mutations in RyR2 in CPVT causes...

Increase resting “leak” of Ca2+ out of SR and/or render RyR2 more sensitive to activation by Ca2+

22

Mutations in calsequestrin2 (CasQ2) in CPVT causes...

Homozygous CasQ2 mutations → dramatic loss of luminal Ca2+ buffering, some result in no effect.

CasQ2 has role in regulation of RyR2 function
-This regulation may be altered in CPVT CasQ2 mutations

23

cAMP dependent protein kinase

PKA

24

G protein associated with alpha 1 adrenergic receptor

Gq

25

Signaling pathway associated with alpha 1 adrenergic receptor activation

PLC, PKC-> increase intracellular Ca2+

26

Effect of alpha 1 adrenergic receptor activation

vasoconstriction

27

G protein associated with beta adrenergic receptor

Gs

28

Signaling pathway associated with beta adrenergic receptor activation

stimulates adenylate cyclase, increases cAMP, PKA activation

29

Effect of beta adrenergic receptor activation

heart: increase chronotropy, luisotropy, inotropy, dromotropy

30

G protein associated with muscarinic Ach receptor

Gi/o

31

Signaling pathway associated with muscarinic Ach receptor activation

inhibits adenylate cyclase, decreases cAMP
- releases beta gamma subunits

32

Effect of muscarinic Ach receptor activation

Decrease chronotropy

33

Channels that produce If (funny current)

Hyperpolarization-Activated Cyclic Nucleotide-Gated channels (HCNs)

34

Sympathetic stimulation to SA node cells → increase cAMP → cAMP binds HCN channels → ?

make channels easier to open (shift voltage dependence activation)

→ speeds rate of diastolic depolarization

35

B-adrenergic (sympathetic) stimulation → increased L-type Ca2+ current →

Increase heart rate

36

Sympathetic stimulation → increased SR Ca2+ load via PKA phosphorylation via LTCC, RyR, and PLB→

increase spontaneous Ca2+ release rate → more diastolic depolarization by activating inward current through sodium-calcium exchanger (NCX) → faster firing rate

37

Molecular targets for sympathetic control of chronotropy (3)

1. Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels (HCNs)
2. L-Type Ca2+ channels and RyR
3. RyR and Sodium-Calcium Exchanger (NCX)

38

Parasympathetic control of chronotropy occurs through activation of _____ receptors by _____

M2 muscarinic receptors
Ach

39

M2 receptors coupled to ____ G protein → activation → ____ and ___ subunits released as signals →

Gi/o
Gai/0 and GBy
inhibit AC → reduce cAMP

40

Molecular targets for parasympathetic inhibition of chronotropy

1. GIRKs
2. HCNs, L-type Ca2+ channels, and ryanodine receptors

41

G-Protein Coupled Inwardly Rectifying K+ (GIRKs)

GBy subunit → binds GIRK channel → increase K+ current in → stabilize membrane potential near Ek → dampens excitation, slows firing frequency

42

Parasympathetic effect on HCNs, LTCC, and RyR

Gai/o subunit → inhibit adenylate cyclase → reduce cAMP levels → Reduce inward current via HCN channel, LTCC, and RyR-NCX

43

6 properties of vascular smooth muscle cells (VSMCs) that differentiate them from cardiac myocytes

i. Small, mononucleated cells, electrically coupled via gap junctions

ii.Not striated, NO SARCOMERES

iii.NO TROPONIN OR TROPOMYOSIN

iv.Ca2+ release from SR not essential for contraction in VSMCs

- Ca2+ regulation of smooth muscle contraction via myosin

v.Rate of contraction slower and contractions are sustained and tonic in VSMCs

vi.DIFFERENT CONTRACTILE MECHANISM: Contraction initiated by mechanical, electrical or chemical stimuli

44

3 types of contractile mechanisms in VSMCs

1. Mechanical stretching → contraction via myogenic response

2.Electrical depolarization → contraction via LTCC activation (graded potential sufficient, AP not required)

3. Chemical stimuli (neuronal/hormonal regulators) → directly activate contraction

45

Ca2+ regulation of VSM contraction (5)

1. Ca2+ enters cytoplasm from SR (mainly) and voltage-gated Ca2+ channels on surface membrane

2) Ca2+ binds to calmodulin (CaM), intracellular Ca2+ binding protein

3) Ca2+-CAM binds to myosin light chain kinase (MLCK), activating it

4) Activated MLCK phosphorylates light chain of myosin (myosin head), → permits cross bridge cycling to occur

5) Contraction halted by dephosphorylation of myosin light chain by myosin light chain phosphatase (MLCP)

46

cAMP causes _____ of VSMCs via:

relaxation
via inhibition of MLCK

47

Autonomic regulation of vasculature is primarily ___

sympathetic
leading to vasoconstriction

48

Sympathetic stimulation in VSMCs occurs through ____ receptors

alpha 1 adrenergic

49

A1 adrenergic receptors

GPCRs coupled to Gq G protein

→ Ga1 subunit → activates PLC → produces DAG and IP3

IP3 → activates IP3 receptors on SR of VSMCs → IP3R channel releases Ca2+ into cytoplasm from SR → VSMC contraction

PKC furthers VSMC contraction by activating inward current via LTCCs → CICR

50

Sympathetic innervation of vascular beds _____ in skin and kidneys but ____ in cerebral and coronary circulations

abundant
sparse

51

Arterial baroreceptor reflex

acute, short-term neural mechanism for control of BP

i.Pressure-sensitive NEURONS in aortic arch and carotid sinus.

1.Adapt to prolonged changes in BP

2.Sensitivity ↓ in hypertension and aging

52

Baroreceptors respond to stretch in arterial walls by

Increasing firing RATE

1.MECHANOsensitive epithelial Na+ channels (eNaC) open in response to stretch induced by high BP → Na+ current depolarizes baroreceptor neurons → fire APs

53

Baroreceptor neurons fire APs that project into the ____

“Cardiovascular Control Center”

1.CV control center integrates signals from baroreceptors and other brain brain regions

2.Output projections of sympathetic and parasympathetic fibers to heart and sympathetic fibers to vasculature

54

Arterial baroreceptor reflex arc:

↑BP→↑baroreceptor firing rate
→ CV control center → ↓sympathetic output and ↑parasympathetic output from CV center

1.→ ↓heart rate, ↓inotropy and ↓vascular tone (vasodilation)

2.→ ↓blood pressure

55

Primary mechanism of blood flow matched to metabolic demand of tissue

Vasoactive metabolites

56

Vasoactive metabolites (4)

all act to cause vasodilation

1.↓ PO2

2.↑PCO2/pH

3.↑ extracellular K+: in active skeletal muscle, Na+ enters cell and K+ leaves during APs

a.High level of activity → Na+/K+-ATPase can’t keep up → K+ accumulates in interstitial space

4.↑Adenosine: produced by hydrolysis of ATP

a.In VSMCs, binds A2 purinergic receptors (GPCR) coupled to Gs

b.↑ Adenosine = ↑cAMP levels in VSMCs → vasodilation by inhibition of MLCK

57

Myogenic response


Feedback mechanism that maintains constant flow despite changes in pressure


1.Independent of metabolic demand

EX) postural change

58

Mechanism of myogenic response

Intrinsic to VSMCs - occurs in denervated vessels

Stretch → open stretch-activated Trp ion channels → inward Ca2+ current → VMSC contraction → vasoconstriction and depolarization of VSMC → further increase in intracellular Ca2+ via LTCC

Myogenic response can be overcome by vasoactive metabolites

59

Nitric oxide (NO) regulation of VSM tone

VASODILATOR produced in vascular endothelium by nitric oxide synthase

1.Short half life → local response

2.Basal release of NO sets resting vascular tone (↓ NO = ↑ increase BP)

3.Agonist stimulated release = MAJOR mechanism for vasodilation

60

NO and disease: (4)

1. Susceptible to CV disease risk factors (smoking, oxidative stress, etc.)

2.NO is anti-atherosclerotic, inhibits development of plaques

3.↓NO is associated with greatly increased risk for atherosclerosis

4.Pts with HTN often have ↓NO, which worsens their condition

61

NO pathway

i. Vascular endothelial cells → produce NO via NO synthase (NOS)
- Humoral regulators (ACh, bradykinin) stimulates activity of NOS

ii.VSM cells → site of NO action

iii. NO → activate guanylate cyclase → produce cGMP → cGMP activate Protein Kinase G (PKG)
→ reduce intracellular Ca2+ via activation of SERCA and inhibition of LTCC
→ Relaxation of VSMC → vasodilation

62

Endothelin regulation of VSM tone

i. VASOCONSTRICTOR produced by vascular endothelium with Endothelin Converting Enzyme (ECE)

1.Endothelin binds ET receptors (GPCRs on VSMCs)
- ET receptors coupled to Gq → increase intracellular Ca2+ in VSMC → Vasoconstriction

ii.Has both a transient (a-adrenergic effect) and a longer lasting effect

63

Primary system for long term control of BP

Renin-angiotensin-aldosterone system

64

Renin

proteolytic enzyme released by juxtaglomerular (JG) cells in renal glomerulus

65

Renin release stimulated by (3)

1) Sympathetic stimulation of JG cells

2) Decreased BP in renal artery

3) Decreased Na+ resorption in kidney

66

What does renin do?

Cleaves circulating inactive protein angiotensinogen → angiotensin I

Angiotensin I cleaved by Angiotensin Converting Enzyme (ACE) to Angiotensin II

67

Angiotensin II (5)

ACTIVE FORM, potent vasoconstrictor

1.Systemic vasoconstriction via binding to GPCRs on VSMCs

2.Stimulates sympathetic activity (thus more vasoconstriction)

3.Stimulates aldosterone release from adrenal cortex

4. Stimulates release of endothelin from vascular endothelium

5. Stimulates release of ADH from pituitary

68

Aldosterone

produced in adrenal cortex

i.Hormone, acts on receptors in kidney collecting ducts

ii.Promotes resorption of Na+ and water → increase blood volume → increase BP

69

Antidiuretic hormone

formed in hypothalamus, released from pituitary in response to hypovolemia, hypotension, high osmolarity, angiotensin II and sympathetic stimulation

i.Binds kidney receptors, increases water reabsorption

ii.Binds vasculature receptors, causes vasoconstriction

70

Atrial natriuretic peptide (ANP)

i. VASODILATOR peptide

ii.Released by atria following mechanical stretch → endocrine function of heart

iii.Long-term sodium regulator, water balance, blood volume, and arterial pressure

- ANP acts on ANPRs throughout the body

- ANPRs are receptor guanylate cyclases (NOT GPCRs)

- Produce cGMP → activates SERCA to stimulate Ca2+ uptake

71

ANP affects (3)

i. Kidney: ↑glomerular filtration rate and ↑secretion of sodium and water.

ii.Vasculature: ↑ vasodilation

iii.Adrenal gland: inhibits release of aldosterone and renin release.

72

Heart failure in the United States

Prevalence: approx 5,000,000
Annual incidence: 550,000
Mortality: 250,000
Cost: $37.5 billion

73

Compliance

relaxation

Worse compliance = same filling pressure (preload) of LV produces less filling → reduce SV

Compliance allows for greater diastolic filling at same pressure

74

Definition of heart failure:

forward vs. backward failure

Inability of heart to pump blood forward at a sufficient rate to meet metabolic demands of the body (forward failure)

OR ability to do so only if cardiac filling pressures are abnormally high (backward failure)

75

Two components of HF syndrome

1) Poor forward blood flow
-Low flow → ↓CO

2) Backward buildup of pressure
-Congestion → ↑filling pressure
-Typically a response to low flow

76

Systolic dysfunction two major hallmarks

1) Decreased ejection fraction
-Heart failure with reduced ejection fraction = HFrEF
-Left ventricular systolic dysfunction = LVSD

2) Ventricular enlargement
-Dilated cardiomyopathy = DCM (heart tends to get bigger and bigger)

77

Systolic vs. diastolic dysfunction

Systolic = problem with squeeze → ↓contraction (↓inotropy)

Diastolic = problem with filling → ↓lusitropy/decrease in relaxation

78

Primary causes of systolic dysfunction (3)

1) Direct destruction of heart muscle cells (myocardial infarction, viral myocarditis, peripartum cardiomyopathy, idiopathic dilated cardiomyopathy, alcohol)

2) Overstressed heart muscle (tachycardia-mediated HF, meth abuse, catecholamine mediated)

3) Volume overloaded heart muscle (mitral regurgitation, high CO)

79

2 Hallmarks of Diastolic dysfunction

1) Normal ejection fraction:
-HF with preserved ejection fraction = HFpEF
-Preserved systolic function = PSF

2) Ventricular wall thickening:
-Left ventricular hypertrophy = LVH
-Hypertrophic cardiomyopathy = HCM→genetic

80

Primary causes of diastolic dysfunction (3)

1) High afterload/pressure afterload (HTN, aortic stenosis, dialysis/inadequate volume removal)

2) Myocardial thickening/fibrosis (HCM, primary restrictive cardiomyopathy)

3) External compression (may not be HF since it doesn’t involve heart itself)
Pericardial fibrosis/constrictive pericarditis, pericardial effusion

81

2 main features of Right-Sided Heart Failure

stress to RV causes inadequate blood pumped through lungs

1) Decrease circulating blood flow (forward RV HF)

2) Increased venous pressures (backward RV HF)

82

Primary causes of right-sided heart failure (4)

1) Left heart failure → increase pulmonary venous pressure

2) Lung disease → pulmonary HTN

3) RV volume overload

4) Damage to RV myocardium

83

4 main compensatory mechanisms for low CO

1) Sodium/fluid retention --> increase preload
2) hypertrophy --> increase contractility
3) dilation --> increase contractility
4) Tachycardia --> increase HR

84

Compensatory responses to decreased CO (3)

1) Neurohormonal activation --> vasoconstriction, Na+ retention, increase HR

2) Frank-Starling increase in preload --> increase end diastolic filling/pressure

3) Ventricular hypertrophy and dilation --> increase contractility

85

Juxtaglomular apparatus response to low CO

Juxtaglomerular apparatus in kidney senses lower flow → renin-angiotensin-aldosterone (RAAS) activation

-↑Sodium retention
-Vasoconstriction

86

Carotid sinus/aortic baroreceptors response to low CO

sense lower pressure → autonomic nervous system/adrenergic activation

-↑HR (tachycardia)
-Vasoconstriction

87

Chornic neurohormonal activation in response to low CO causes what?

1) ↑sodium retention + vasoconstriction + ↑HR →↑volume

2) →↑LV filling → supranormal filling pressures (cause congestion)

Low CO output → fluid retention to maintain SV/CO → congestion in CHF

Chronic neurohormonal activation begets worsening HF

88

Adverse cardiac remodeling includes:

1) Ventricular hypertrophy/dilation

2) Myocardial damage/apoptosis and fibrosis

Result of long term increase in cardiac workload and increased metabolic demands

89

Overtime remodeling causes (3)

1) Decreased contractile force

2) Decreased dynamic function

3) Increased diastolic stiffness (decreases preload)

90

Neurotransmitters of ANS

Preganglionic sympathetic and parasympathetic = ACh

Post ganglionic sympathetic = NE

Post ganglionic parasympathetic = ACh

91

Receptor subtypes for ACh (2)

Nicotinic
Muscarinic

92

Nicotinic Receptors

in cell body of postganglionic neurons of autonomic ganglia

Ligand gated, non-selective cation channel (Na+ and K+) → depolarization and excitation

93

Muscarinic receptors

in effector cells of cardiac and smooth muscle, and glands

G-Protein Coupled Receptor - 5 subtypes of M receptors

ACh binds → conformational change in receptor → activation of G protein → stimulates or inhibits other intracellular effectors

94

Receptor subtype for NE?

Adrenergic receptors (alpha or beta)

95

Sympathetic nervous system:

Preganglions located in _______ and ______

Postganglions located where?

myelinated? NT?

Fight or Flight

Preganglions located in thoracic and lumbar spinal cord

Postganglionic neurons in ganglia of sympathetic trunk (NEAR SPINAL CORD)
-Project to target organs → innervate smooth muscle, cardiac muscle, or glands

Preganglionic = myelinated (ACh)
Postganglionic = unmyelinated (NE)

96

Adrenal medulla

neuroendocrine gland of sympathetic nervous system

Secretes epinephrine and NE → bind adrenergic receptors in bloodstream (act as HORMONES)

97

Sympathetic nervous system main actions on CV system (3)

1) Primary control of vasodilation (decreased sympathetic input) and vasoconstriction (increased sympathetic input)

2) Increases HR

3) Increase force of contraction

98

Parasympathetic nervous system:

Preganglions located in _______ and ______

Postganglions located where?

long or short axons? NT?

Preganglions located in brainstem nuclei and sacral spinal cord
-long axons
-ACh

Postganglions located in ganglia NEAR OR IN target organ
-short axons
-ACh

99

Parasympathetic nervous system main actions on CV system (3)

1) decrease HR
2) decrease force of contraction
3) small amount of vasodilation

100

How does sympathetic NS increase HR and force of contraction?

Sympathetic stimulation (increased NE) → increase BP (increased HR and contractile force)

NE → B1-adrenergic → increase cAMP → PKA → Ca2+ channels, HCN channels

1) Steeper AP depolarization → time between AP decreased = increased HR

2) Increased AP amplitude = increased contractility

101

How does parasympathetic NS decrease HR and force of contraction

Parasympathetic stimulation (increased ACh) → decreases BP (decreases HR and contractility)

ACh → M2 muscarinic receptors → decrease cAMP → activates K+ channels

1) Shallower slope of AP → decreased HR

2) Decreased AP amplitude → decreased contractility

102

ANS maintenance of homeostasis to control BP via what mechanisms?

1) Sympathetic stimulation to increase HR and force of contraction (NE --> B1 adrenergic receptors --> increase cAMP)

2) Parasympathetic stimulation to decrease HR and force of contraction (ACh --> M2 receptors --> decrease cAMP)

3) Baroreceptor Reflex:
-Low BP → increase in sympathetic output
-High BP → increase in parasympathetic output

103

Hypothalamic regulation of CV system

Controls Humoral Response to Low BP: controls release of hormones via pituitary

Head Ganglion of ANS - Integrates information from several brain regions to convey needs of of body to preganglionic autonomic centers in brainstem and spinal cord

104

Hypothalamic humoral response to low BP

Low BP detected by hypothalamus → release of ADH (vasopressin) from posterior pituitary → vasoconstriction
→ kidneys increase water retention

Low BP detected by kidneys → renin released → angiotensin II → constrict blood vessels, increase water retention → activate neurons in hypothalamus

105

What happens when you stand up? (postural accommodation - lying down to sitting/standing)

4 steps

1) More blood pools in LE but skeletal musculature acts as venous pump with movement

2) → Increase venous return

3) → Increased End Diastolic Volume (stretching heart more)

4) → increased force of contraction and thus SV

106

What happens during isotonic exercise? (4 things)

biking, jogging, swimming

1) Decrease peripheral vascular resistance → decrease afterload

2) → Increased venous return (Frank-Starling) → increased EDV --> increased inotropy

3) Increase HR

4) Increased preload AND decreased afterload

107

What happens during isometric exercise?

1) Increased peripheral vascular resistance (maintain blood flow to exercising muscle group) → increased afterload → decreased SV

2) Increase HR

3) No increase (or decrease) in CO

108

what happens during the acute pahse of a myocardial infarction (3 main things)

1) Loss of functional myocardium

2) Increased catecholamine surge (Sweating, tachycardia, +/- HTN)

→ Increased inotropy to maintain CO despite increased BP (afterload)

3) Heterogenous cellular environment

-Local/regional changes in pH, membrane potential and secondary effect on cytosolic calcium

109

Physiologic hypertrophy

due to: chronic exercise, pregnancy

1) Increase myocyte length > increase myocyte width

2) Increase in ATPase and in aa dimer of myosin heavy chain

110

Pathologic hypertrophy

due to: chronic HTN (diastolic HF), fibrosis

1) Increase myocyte width > myocyte length

2) Decrease in ATPase activity and increase in BB dimer of myosin heavy chain

111

Cardiac dilation occurs due to _______ or ______ and results in what changes to the myocyte

MI or DCM (systolic HF)

Increase myocyte length >> increase in myocyte width

112

Contemporary view of the heart's ability to adapt

1) cardiac adaptation is dynamic, involving structural and architectural changes

2) In response to environment, both quantity and quality of contractile elements altered

3) programmatic alterations in gene and protein expression occur in response to pathologic or physiologic triggers --> both phenotypic and genotypic plasticity

113

Left Ventricular Hypertrophy is often due to _______.

Mechanism?

longstanding HTN (increased afterload = decreased SV)

Mechanism:
-Increase in Ca2+ via LTCC
-Reduced SERCA2 function (due to increased PLB)

--> impaired relaxation and increased cytosolic Ca2+ (new steady state)

114

LVH can lead to ______

CHF

115

SERCA2 Gene transfer study

SERCA2 gene transfer sufficient to correct mechanical defects in cardiocytes from animals with HF

-Increasing SERCA2 --> increase lusitropy BUT also increases inotropy

116

Altered NFAT transcriptional regulation study

Increased Ca2+ steady state present in LVH --> Ca2+ activates calcineurin --> calcinueirn cleaves phosphate from NFAT

--> Activates NFAT

--> NFAT affects cardiac growth and remodeling genes

--> NFAT upregulation drastically increases muscle mass and decreases inotropy

117

Positive feedback of CHF and worsening cardiac function

1) Primary muscle damage → pump dysfunction → decreased CO

2) Decreased CO → hypertrophy, myocyte remodeling, dilation, adrenergic stimulation, neurohormonal stimulation

a) Neurohumoral activation
→ apoptosis and further muscle damage
→ RAS and sympathetic activation → Edema, tachycardia, congestion

b) Ventricular remodeling
-Left ventricular hypertrophy and myocyte remodeling → edema, tachycardia, congestion

118

Symptoms of HF are due to (3)

1) Decreased CO --> decreased perfusion of organs

2) Increased pulmonary venous pressure --> dyspnea

3) Increased central venous pressure (increased R-sided filling pressures) --> peripheral edema, hepatic congestion, ascites

119

Orthopnea

immediate SOB when lying flat (blood pooling in legs now poolling in abdomen/thorax)

120

Paroxysmal nocturnal dyspnea (PND)

delayed SOB, waking patients from sleep → mobilization of edema from tissue through lymphatics back into bloodstream and into lungs

121

Acute pulmonary edema

acute, intense SOB

-Occurs once fluid retention/left atrial pressure overwhelms compensatory mechanisms → fluid spills from pulmonary vasculature into interstitial space and then into alveoli→hypoxia

-“fluffy” infiltrates on CXR

122

NY heart association functional class system

I: asymptomatic
II: symptomatic with moderate exertion
III: symptomatic with minimal exertion
IV: symptomatic at rest

123

ACC/AHA HF Stages

A: At high risk for HF but without structural heart disease or symptoms of HF

B: Structural heart disease but without symptoms of heart failure.

C: Structural heart disease with prior or current symptoms of heart failure.

D: refractory heart failure requiring specialized interventions.

124

Common precipitants of worsening HF (6)

1) Increased circulating volume (preload)

2) Increased pressure (afterload)

3) Worsened contractility (due to MI, intotrope, B-blocker, etc.)

4) Arrhythmia

5) Increased metabolic demands

6) non-adherence with HF meds

125

Physical signs of low flow include...(3)

1) Cool extremities—peripheral vasoconstriction to redirect what existing blood flow there is to vital organs.

2) Tachycardia—compensate for low stroke volume

3) Low pulse pressure—reflection of low output.

126

Signs of elevated LEFT-sided filling pressures (6)

1) Dyspnea, orthopne, paroxysmal nocturnal dyspnea, hypoxia, rales

2) Tachypnea, Tachycardia

3) Diaphoresis

4) Fatigue

5) S3 gallop --> systolic dysfunction

6) S4 gallop --> diastolic dysfunction

127

Signs of elevated RIGHT-sided filling pressures (3)

1) Peripheral edema

2) RUQ discomfort due to hepatic congestion/enlargement

3) JVD (increased central venous pressure)

128

JVP = ?

A wave = ?

C wave = ?

V wave = ?

Right atrial pressure

A wave = atrial contraction (absent in AFIB)

C wave = closing of tricuspid valve early in systole

V wave: movement of RV annulus and tricuspid valve backward at very end of systole (before valve opens)

129

S3 gallop

Symptom of systolic HF

rapid expansion of ventricular walls in early diastole

HFrEF/dilated heart

Ken-tuc-ky (S1-S2-S3)

Implies high LA filling pressure

130

S4 gallop

Symptom of diastolic HF

atria contracting forcefully in an effort to overcome abnormally stiff or hypertrophic LV

Ten-ne-ssee (S4-S1-S2)

Absent in AFIB

131

B-type natriuretic protein (BNP)

BNP secreted by myocardium in response to:
-Ventricular stretch
-Hyperadrenergic state, RAAS activation, ischemia

BNP/NT-proBNP assays used to rule out HF (unlikely you have HF with a low BNP)

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Right heart catheterization

-measures pressure and flow and thus can calculate resistance as well

1) Catheter placed into major vein, floated through R heart into pulmonary artery

2) Balloon on end helps blood flow carry it to lungs

3) Balloon occludes branch of pulmonary artery so downstream pressure can be measured = LA pressure / left sided filling pressure

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Echocardiocraphy

Provides: LVEF, chamber size (dilation), LV wall thickness (hypertrophy), measures of relaxation (diastology), valvular anatomy and function, filling pressures, pulmonary pressures.

Advantages: real time, non-invasive, no radiation, inexpensive

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Specific goals of HF treatment (5)

1) Correct underlying cause of HF (ex-revascularization for ischemia)

2) Eliminate precipitating factors (acute infection, arrhythmias, salt)

3) Reduce pulmonary and systemic congestion (salt restriction, diuretics)

4) Improve forward CO (flow) (vasodilators and positive inotropic drugs)

5) Modulate neurohormonal action (prevent negative remodeling)

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Diuretics

promote elimination of Na+ and H2O → reduce intravascular volume and venous return to heart = VOLUME CONTROL

-DECREASE ventricular end-diastolic pressure by increasing salt and water excretion → decrease venous congestion → decrease dyspnea and edema

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Arterial Vasodilators

↓ systemic vascular resistance → ↓ LV afterload, ↓ cardiac work, ↓ mitral regurgitation

137

Venous vasodilators

increase venous capacitance → ↓ venous return → ↓ preload and LV diastolic pressure

--> decreased oxygen demand by cardiac myocytes (useful during ischemic event - use of NTG with CP)

138

Pulmonary vasodilators

↓ RV afterload

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ACE inhibitors

"pril"

1) Inhibit conversion of ATI --> ATII
-prevent vasoconstriction (decrease afterload)
-prevent release of ADH
-prevent absorption of Na+ and H2O

2) Inhibit breakdown of Bradykinin
-promote vasodilation (via NO)
-reduce sympathetic activity

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Angiotensin receptor blockers (ARBs)

"artan"

Selective inhibition of AT1 Receptor (Ang II receptor)

Similar effects as ACE inhibitors

Advantages over ACEI:
-no cough/angioedema from kinin --> use ARB if pt has cough on ACE inhibitor
-blocks non-ACE pathways also

Disadvantages:
-no kinin vasodilation, blocks just AT1 (no AT2)
-more expensive

141

Aldosterone receptor blockers

-Block aldosterone in collecting tubules → increase sodium excretion → diuretic

-Also antifibrotic

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B-blockers

"olol"

Antagonize effects of Sympathetic nervous system → ↓chronotropy ↓inotropy (short term loss for long term gain)

143

Side effects of ACE inhibitors

hypotension, worsening renal failure, hyperkalemia, **cough (kinin production), angioedema

144

Inotropes

administered via IV agents short term in ICU to reverse shock (cold and wet)

Long term = worsen remodeling ↑mortality

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OVERALL TREATMENT of Chronic (stable) HFrEF patients

1) ACE inhibitors / ARBs
+ 2) B-blockers
+ 3) diuretics

→ Anti-remodeling + Decreased hypertrophy, fibrosis, and apoptosis
--> decreased volume (reduce congestion, edema, etc.)

146

Implanted cardioverter defibrillator is used in patients with _______ or _____ and acts to...

LVEF less than 35% or with prior dangerous rhythms

Abort sudden cardiac death from ventricular tachycardia/fibrillation

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Cardiac Resynchronization Therapy

-Fixes dyssynchrony caused by LBBB

-LV lead placed from RA through coronary sinus over epicardium of LV (3 leads: RA, RV coronary sinus/LV)

-For patients with QRS > 120 msec (bundle branch block)

Cause lateral wall and septal wall to contract together, which produces:
-More efficient contraction→ ↑ stroke volume
-May also improve mitral valve function→ ↓ regurgitation

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Advanced cardiac therapies include (3)

1) Transplantation
2) Mechanical support devices (LVAD)
3) Hospice

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Treatment of HFpEF

Neurohormonal antagonists, ARB, and ACE inhibitors NOT successful in improving outcomes for HFpEF

1) Treat underlying disorder: HTN, diabetes, kidney dysfunction, aortic stenosis

2) Diuretics: keep volume normal (sodium retention common)

3) Vasodilators: maintain normal BP

150

Drug-drug interactions of ACE inhibitors (2)

-lithium
-NSAIDs

151

Both ACE inhibitors and ARBs are contraindicated in...

pregnancy

152

Hydrochlorothiazide (thiazide diuretics) mechanism of action

Block NaC; reabsorption in distal tubule by inhibiting Na/Cl cotransporter

-increases reabsorption of Ca2+

153

Side effects of Hydrochlorothiazide

1) secretion competes with uric acid secretion (may cause gout attack)

2) Hypokalemia

154

Loop diuretics mechanism of action

-preferred class of diuretics for CHF
-inhibits Na/K/2Cl cotransporter and thus Na+ reabsorption in kidney tubules

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Neprilysin inhibitors

Used in combination with Valsartan (ARB)

-Neprilysin: acts to break down BNP

We don’t want BNP to be broken down because it:
→ vasodilation, decrease BP, decrease sympathetic tone, decrease ADH, decrease fibrosis/hypertrophy, natriuresis/diuresis

**Use recommended for patients with HFrEF, in conjunction with other HF therapies in place of an ACE inhibitor or ARB

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DO NOT use Neprilysin inhibitors with contaminant use of ________

ACE inhibitor

157

Ivabridine

new drug on market

-Effects HR NOT force of contraction

-Blocks funny current channel

-For pts with chronic HFrEF

158

Increased CNS sympathetic outflow results in...

_______ act to prevent this

1) Increase cardiac activity → Myocyte death, increased arrhythmias, B1-receptor downregulation, increased HR
Cardiac myocyte growth
Positive inotropy

2) Increased sympathetic activity to kidney and blood vessels
→ vasoconstriction, sodium retention

B-BLOCKERS

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B-Blockers prevent (4) and act to IMPROVE _________

1) Downregulation of B1-receptors
2) Apoptosis/Oxidative stress and cell death
3) Increased arrhythmic potential
4) Hypertrophy/Fibrosis

will eventually IMPROVE contractility, but can make patients feel worse in short term (must titrate dose up)

160

DO NOT use B-blockers in patients with:

1) Lung disease

2) taking inotropes or vasodilators

161

Use B-blockers in combination with _____ and _____ for patients with _____________

ACE inhibitor and diuretic

HFrEF with current or prior symptoms

162

Digoxin mechanism of action

1) Blocks Na/K+ ATPase exchanger → dec. Na extrusion → inc. Ca influx via NCX→ Ca-induced Ca release → increases inotropy

2) Decrease sympathetic (NE) action in AV node --> slow HR

163

Digoxin reduces _____ but not ________ in terms of patient outcomes and used for what patients?

patient hospitalizations
NOT mortality

HFrEF, NOT for HFpEF
-HF due to reduced contractility
-HF with AFIB

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Pharmacokinetics of Digoxin

Effects are dose-dependent (use LOW doses b/c of narrow therapeutic index)

Oral or parenteral

T ½ = 38hrs (slow onset= don’t use in acute situations)

RENAL excretion with some P-glycoprotein metabolism

165

For severe overdoses of digoxin...

can adminster Digibind (anti-dig Ab)

166

Side effects of digoxin (5)

1) GI = nausea, vomiting, abdominal pain

2) Neuro = weakness, confusion

3) Electrolyte = hyperkalemia

4) Cardiac = bradycardia, heart block, arrhythmias

5) Visual = light sensitivity, blurred vision, yellow halo around lights

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Drug-drug interactions with digoxin

beware of use with drugs that inhibit P-glycoprotein (involved in digoxin metabolism)

Anti-arrhythmics
Antifungals
Ca2+ channel blocker
Macrolides
Quinine

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Dobutamine mechanism of action

B1 receptor agonist (Gs→ cAMP→ PKA → increase Ca) → increase contractility
Slight peripheral vasodilation

-rapid onset (T 1/2 = 2 min)

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ONLY use intoropes when?

ONLY use in acute HF (hypoperfusion with/without congestion)

Use only for acute HF because it’s like “beating a dead horse” – Telling failing heart to pump faster and harder by increasing Ca2+ influx and sympathetic tone

170

Milrinone mechanism of action

PDE inhibitor → inhibit breakdown of cAMP → augment myocyte Ca2+ utilization

171

Dopamine mechanism of action

B-adrenergic agonist

Endogenous precursor of NE → stimulate adrenergic receptors and increase release of NE from nerve terminals

Dose-dependent effects
Continuous infusion via infusion pump

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Acute toxicity associated with digoxin

Second or third degree heart block
-Progressive bradycardia
-Severe ventricular arrhythmias

Elevated serum potassium levels > 5.5 mEq/L