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AVMO > Cardiovascular Physiology > Flashcards

Cardiovascular Physiology Flashcards

1
Q

Describe the important aspects of Cardiac function

A 
Transport
Oxygen
CO2
Wastes
Nutrients
Hormones
Heat
Immunity
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2
Q

Determinates and regulation of cardiac output

A
  • Heart rate: Nerves and hormones
  • Contractililty: Stroke volume
  • Preload
  • afterload

Neural control

  • PNS via vagus: Ach on muscarinic receptors affects only HR
  • SNS - T1-4: Noradrenaline -> B1 receptors. Affects HR and Contractility (preload and afterload)

Hormonal : direct via adrenaline and indirectly

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3
Q

Determines of SVR

A

Neural

  • SNS: - noradrenergic (Vasoconstrictor (α1) – eg. gut, skin. β1 inotropy. Vasodilator (β2) – eg. airways, muscle. β3 Heat production)
  • PNS: Cholinergic – vasodilator eg M3 eg gut, M2 negative- chrontropy

Hormonal

  • Systemic factors: Catecholamines, ADH, Angiotensin II, Aldosterone, ANP
  • Endothelial factors: NO, Prostaglandins, thromboxane A2, Leukotrienes, Histamine, bradykinin, serotonin (5-HT)

Local
- Reactive hyperaemia: Adenosine, CO2, PO2, pH, K+, Temp

Myogenic

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4
Q

Describe the processes that facilitate venous return

A 
Intravascular volume
Venomotor tone
Valves
Pumps - MSK, Thoracic and abdominal pumps
Suction by the heart
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5
Q

Describe the central control mechanisms of the CVS

A 
Centro-lateral medulla
Input
- High pressure - baroreceptors
— Carotid sinus
- Low pressure - Volumereceptor
- Chemoreceptors in the kidney
- higher centres - Pain and stress
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6
Q

Cardiovascular physiology in aviation

A

G tolerance: Maintaining arterial blood pressure and cerebral perfusion
Hypoxia: Maintaining tissue oxygenating
Cardiovascular stresses of flight: Thermal, exertional, accident survival
CV disease causing incapacitation

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7
Q

General principles of Haemodynamimcs

A

Pascal’s principle: pressure at a point in a fluid is the same in all directions
Hydrostatic pressure: Ph=pgh

No flow means pressure anywhere at the same horizontal level is the same
Flow occurs from height to low pressure.
Moving fluid has momentum
Dynamic of flow - laminar vs turbulent.

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8
Q

Hydrostatic effects on blood pressure

A 
Heart level 100mmHg
Lower above heart
Higher pressure below heart
22mmHg pressure drop heart to brain in the upright human at +1G
Effects are multiples with G
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9
Q

Pressure in Vein

A

Low pressure 0-15mmHg

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10
Q

Effect of the environment on CVS disorders

A 
Hypoxia of all types
sustained G
G countermeasures
stress
physical activity/workload
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11
Q

Effect of CVS disorders on aviation operations

A 
Distracting symptoms
- pain and palpitations
Suddenly incapacitation, haemodynamic compromise
- hypotension
- syncope
- silent disease
- sudden death
- thromboembolism

medication side effect

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12
Q

questions to ask referring specialist

A

What is the diagnosis
what is the % risk of incapacitation per year
what is the prognosis and risk of recurrence
what treatment, and what side effects?
what follow-up or monitoring is required?

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13
Q

cardiac investigations

A

Resting ECG: very poor sensitivity
Exercise stress ECG: easy, non-invasive, 1st line for CAD
Holter Monitoring: for rhythm and conduction disturbances, syncope and pre-syncope, post-ablation success.
MPS - assesses functional ischaemia even in the absence of anatomical lesions
Echocardiography: useful for ix for murmurs, suspicion of structural heart disease, pressure gradients/velocities, pericardial conditions, cardiomyopathy, EF estimation.
Stress ECHOcardiography: more sensitivity than exercise stress ECG, assesses functional ischaemia. useful if ECG uninterpretable eg LBBB
Coronary angiography: gold standard test for IHD
Calcium score:independent risk factor but expensive. stress echo is a better predictor of events

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14
Q

considerations for treatment of HTN

A

lifestyle changes first
don’t need to TMUFF if <160/100mmHg and overall CVD risk score acceptable
If failure to improve after maximum 6 months trial of conservative Mx then TMUFF and commence on pharmacological therapy

TMUFF 14 days initial
- 7 days with subsequent change

UMECR required

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15
Q

pharmacological tx of HTN

A

ACEi/ARB 1st line agents
Thiazide diuretics
Ca channel blockers - unfit for high-performance flying duties.
Beta - blockers: unfit for high - performance flying duties
alpha blockers NOT permitted for flying duties

some combination therapies may be unfit high performance or multi crew.

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16
Q

Consideration for lipid lowering agents

A

conservative therapy

  • no TMUFF or MECR needed if overall CVD risk score is acceptable
  • eg lifestyle changes and fish oil

Pharmacology

  • statin first line medication option
  • TMUFF 7 days
  • 7 days with which subsequent change
  • UMECR required
  • can add ezetimibe, bile acid sequestrates, fibrate

Nictotinic acid not permitted for flying duties

17
Q

Considerations for antirrhythmics

A 
Underlying condition is likely disqualifying for military aviation
In clivilian aviation, case by case 
- AF increasely common
-rate control vs prophylaxis of AF
- Sotalol and other B-blockers
18
Q

Consideration for anticoagulation

A

Military

  • aspirin acceptable
  • clopidogrel disqualifying
  • warfarin disqualifying
  • Factor Xa inhibitors (NOACs)

Civilian

  • warfarin requires evidence of stable INR control
  • Class 1 multi crew only
19
Q

Consideration for CABG

A

1st year 10% rate with venous grafts
2rd year onwards - 1-3% per annum
at least 6-12 months recovery

waiver consideration

  • cardiology R/V annually
  • EF >50%
  • MPS
  • demonstrates risk factor control
20
Q

Angioplasty +/- stenting considerations

A

Risk of early re-stenosis, easing over times

6-12 months recovery

waiver consideration

  • cardiology R/V annually
  • EF 50%
  • MPS
  • Demonstrates RF control
  • no combination anti-PLT therapy
21
Q

Ground for 6 months post CABG and Angioplasty with stent if what consideration occur

A

Incomplete revascularisation
postoperative graft or stent failure
low output syndrome
post operative arrhythmias: AF 15-40%, most settle within 8 weeks, VT/VF mainly preoperatively with within 1 week.

adverse neurological outcomes

  • major events 21% mortality
  • minor event - 10% mortality
22
Q

Consideration for pacemakers

A

disqualifying for military flying due to potential for EMR interaction with Device

Civilian

  • restricted certification
  • dual chambered, bipolar leads, annual checks.
23
Q

Consideration for radio-frequency and cryoablation for AF

A

relatively high recurrence rate
Ground for 12months
Need to exclude arrhythmias provide to clear for fly

risk for pulmonary vein stenosis

24
Q

what are the baseline need for CASA

A

LVEF >50%
absence f jeopardise myocardium - no reversible ischaemia
Acceptable incapacitation risk

AVMO (49 decks)

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