Haemodynamics and Heart Failure Flashcards

1
Q

What is the juxtaglomerular apparatus?

A

A specialised structure in the kidney formed by the distal convoluted tubule and the glomerular afferent arteriole. Its main function is to regulate blood pressure and the filtration rate of the glomerulus.

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2
Q

Where is renal perfusion pressure sensed?

A

At the glomerulus

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3
Q

Where is sodium concentration sensed?

A

In fluid surrounding convoluted tubule

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4
Q

If renal perfusion or Na+ concentration reduction is sensed, what is released?

A

Renin

Inactive prorenin –> renin + active prorenin

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5
Q

What is diastolic dysfunction?

A

Known as heart failure with preserved ejection fraction (HFPEF)

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6
Q

What is systolic dysfunction?

A

Known as heart failure with reduced ejection fraction (HFREF)

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7
Q

Steps of heart failure

A
  1. Back pressure in LV causes raised pressure in pulmonary circulation
  2. Increased hydrostatic pressure forces fluid outside vascular compartment
  3. Interstitial space in lungs fills with fluid (Pulmonary oedema / Pleural effusions)
  4. Patient becomes breathless, oxygen sats drop
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8
Q

Does lying flat worsen or better symptoms of heart failure?

A

Lying flat worsens symptoms (orthopnoea)

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9
Q

What happens when heart failure affects the RV?

A
  1. Back-pressure transmits to venae cavae
  2. Internal jugular venous pressure rises
  3. Gravity and raised orthostatic pressures force fluid from vascular compartment to peripheral tissue
  4. Ankles / sacrum swell
  5. Hepatomegaly / ascites
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10
Q

What happens when LV stretch eventually exceeds physiological levels?

A
  • Decompensation (move to descending limb of sarcomere tension curve)
  • Small rises in LVEDP (i.e. fluid retention) cause large drops in sarcomere tension, i.e. LV contractility and stroke volume
  • Reduces CO, further impact on ANS and RAS
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11
Q

Summary so far:

A
  • Heart failure may be diastolic, systolic or both
  • Reduced cardiac output detected by baroreceptors, JGA etc.
  • Sympathetic and RAAS activation to compensate
  • Chronic overactivation of both is pathological
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12
Q

What is a key value calculated on an echocardiogram when assessing heart failure?

A

Left Ventricular Ejection Factor (LVEF) for assessment of severity

≥55% is normal
45-54% is mildly impaired
36-44% is moderately impaired
≤35% is severely impaired

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13
Q

What is the equation for LVEF?

A

Stroke Volume / End Diastolic Volume

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14
Q

Given End Diastolic Volume is 111.45ml and End Systolic Volume is 44.76ml, find stroke volume

A

Stroke Volume = EDV - ESV

= 66.69ml

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15
Q

Given Stroke Volume is 66.69ml and End Diastolic Volume is 111.45ml, find the ejection fraction

A

Ejection Fraction = Stroke Volume / End Diastolic Volume

= 59.8% (normal)

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16
Q

Effects of diuretics?

A
  • Limit reabsorption of fluid
  • Offloads the ventricles
  • Moves us back along the Starling curve
  • Can maximise LV contractility
17
Q

Side effects of diuretics?

A

Renal dysfunction
Reduces Na, K, Mg
Can induce diabetes (thiazides)

18
Q

Effects of ACEi?

A

Block conversion of angiotensin I to angiotensin II

  • Reduces effects of AgII on vasculature
  • Diminishes release of aldosterone
  • Can cause bradykinin accumulation  cough
19
Q

Effect of Angiotensin receptor blockers (ARB)?

A

Work on the AgII – receptor interaction

20
Q

Effects of beta-blockers?

A

Beta-receptors are involved in myocardial and renal responses to reduced CO
Blockade of these can reduce HR
Moves back along the Bowditch curve
Allows LV more relaxation time, so better filling
Also blunts RAAS overactivation
Concomitant effects on fluid retention

21
Q

Conditions where caution must be taken with beta blockers?

A

Asthma, low HR, heart blocks

22
Q

What is Valsartan?

A

An ARB

23
Q

What is Sacubitril?

A

A neprilysin inhibitor

  • Enhances action of natriuretic peptides
  • Promotes sodium/water excretion
24
Q

Is Valsartan/Sacubitril combination good?

A

Combination has good evidence above ACEI/ARB