Heart failure pathophysiology Assignment 2022

1. Heart failure pathophysiology
Congestive Cardiac Failure - “Heart failure is a complex
clinical syndrome that is frequently, but not exclusively,
characterised by an underlying structural abnormality or
cardiac dysfunction that impairs the ability of the left ventricle
(LV) to fill with or eject blood, particularly during physical
activity. Symptoms of CHF can occur at rest or during physical
activity.
CCF is the inability of the heart to maintain an output, at rest or
during stress, necessary for the metabolic needs of the body.
End Diastolic Volume (EDV) - The amount of blood returning
to the heart and filling the ventricle
End Systolic Volume (ESV) - The volume of blood that
remains in the ventricle at the end of systole
Stroke Volume (SV) - Volume of blood pumped out of the
heart by the left ventricle with each beat (measured in mL), Not
all the blood that is in the ventricle is ejected, usually just over
half or 1mL/kg.
SV= EDV-ESV
=120mL/beat- 50 mL/beat
=70 mL/beat
Preload - The amount of blood at the end of diastole prior to
contraction AND A measure of the degree of the ventricular
stretch at the end of diastole prior to contraction (is influenced
by the factors just prior to ventricular contraction and is
determined by the end-diastolic volume (and the associated
end-diastolic pressure).

Contractility - Ability of the myocardial fibres to shorten or
contract when loaded. Determines the force of contraction
Afterload - The force which the ventricle must overcome to eject blood.
The resistance to the ejection of blood from the left ventricle. E.g.
Systemic Vascular Resistance (SVR)
Cardiac Output (CO) - The amount of blood pumped around the body in one
minute.
CO = SV x Heart Rate (HR)
E.g for a healthy person weighing 70kg SV 70mL x HR 70bpm = CO 4.9L/minute
Frank-Starling law of the heart - ↑ stretch= ↑cardiac output, more
volume (blood) in the left ventricle increases the stretch of the cardiac
myocytes, which will increase the force of contraction
Ejection Fraction (EF) - Percentage of blood the left ventricle pumps
out with each contraction OR blood ejected during systole.
E.g. In a healthy person weighing 70kg, Normal End Diastolic Volume
(EDV) is about 120mls and SV 70mls the EF is 58%
Normal EF is 55-70%
Causes of HR: disorders that increase the workload of the heart and
disorders that interfere with the pumping ability of the heart.
When RASS is activated, the JUXTA GLOMERULAR cells in the
kidneys produce RENIN which converts to
ANGIOTENSINOGEN in the liver to ANGIOTENSIN 1.
ANGIOTENSIN 1 is then converted to ANGIOTENSIN 2 using the
enzymes called Angiotensin-converting enzyme (ACE).

Angiotensin 2 now stimulates the adrenal cortex to produce
ALDOSTERONE. It also stimulates the PITUITARY GLAND to
produce anti-diuretic hormone (ADH). Both of these INCREASE
the reabsorption of sodium water. This increases the
reabsorption of the BLOOD VOLUME and the cardiac output.
Renin Angiotensin Aldosterone (RAAS) is one of the
compensatory mechanisms in early stages of heart failure.
RAAS causes - increased reabsorption of sodium and water.
Stroke volume can be calculated using: End-diastolic volume
and end-systolic volume.
Increased venous return is caused by stimulation of: Alpha
receptors
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2. Heart failure clinical features and management
Decreased contractility causes left heart myocardial damage
releasing B-NATRIUERETIC PEPTIDE from the atria. This
reduces the EJECTION FRACTION of the left ventricle. Blood
backs up into the pulmonary circulation using an increase in
PULMONARY VENOUS PRESSURE. This causes an increase
in the HYDROSTATIC PRESSURE which causes the fluid to
move into the interstitial space. This results in PULMONARY
EDEMA. This DECREASES the gas exchange. Hypoxia is
sensed by CHEMORECEPTORS sending signals to the
respiratory centre in the medulla oblongata which in turn
INCREASES the respiratory rate.

Blood back up in the inferior vena cava can result in:
Hepatomegaly
Crackles in the lungs are typically due to fluid in this space:
Interstitial
Inability to breathe in supine position is called: Orthopnoea
Congestion in the superior vena cava can result in distension of
this vein: Jugular
ECHOCARDIOGRAM is the most useful investigation to
determine heart failure.
FRUSEMIDE is a common loop diuretic used in patients with
heart failure.
CAPTOPRIL is an example of an ACE inhibitor used for heart
failure.
DIGOXIN is a cardiac glycoside used in heart failure.
Daily weighs are used to adjust the dosage of
FRUSEMIDE/DIURETIC medication administered in heart
failure.
Side effects of DIGOXIN toxicity is: DYSRYTHMIAS.
HYPERKALEMIA is a side-effect of ACE inhibitor group of
medications.

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3. Asthma pathophysiology
Elastic recoil is the tendency of the lungs to return to the
resting state after inspiration, in a similar way that an elastic
band springs back into place after being stretched.
Compliance is the measure of lung and chest wall distensibility
(stretchiness) and is defined as volume change per unit of
pressure change.
Airway resistance is determined by the length, radius and
cross-sectional area of the airways and density, viscosity and
velocity of the gas (Poiseuille's law).
Ventilation is the mechanical movement of gas or air into and
out of the lungs.
Tidal volume: The amount of gas inspired or exhaled each
breath
Partial pressure: is directly proportional to the percentage of
that gas in the mixture of gases
The partial pressure of arterial oxygen is less than the partial
pressure of arterial carbon-dioxide in deoxygenated blood
entering the lungs for gas exchange. True

Decreased level of oxygen at the tissue level is called
hypoxemia. False
In a normal lung the ventilation perfusion ratio will be 4:5. True
Mast cells _____ to release histamines, leukotrienes, and
prostaglandins. Degranulate
These predominantly release cytokines and leukotrienes in
asthma. Eosinophils
Cell-mediated immune response is also called Type 1 _____.
Hypersensitivity
The effect of inflammatory mediators on the bronchus causes
_____. Bronchoconstriction
The functional unit of lungs: Alveoli
The oxygen haemoglobin dissociation curve shifts in asthma
towards the: right.
The cause of mucosal oedema can be attributed to which of the
following factors: leukotrienes, histamines, prostaglandins
Wheezing occurs due to: Inability of air to move in and out
through obstructed passage.