Cardiac Physiology and Failure Flashcards
How is mean arterial pressure calculated?
MAP approximates to diastolic + 1/3 pulse pressure
What is the pulse pressure?
The difference between the systolic and diastolic blood pressures
What is the difference in right and left ventricular pressures?
LV systolic 120mmHg
RV systolic 25 mmHg
What is the right atrial pressure equivalent to?
How is this seen clinically?
Central Venous Pressure
Jugular Venous Pulse
What cardiac events are associated with the first heart sound (S1)?
Closure of mitral and tricuspid valves
What cardiac events are associated with the second heart sound (S2)?
Closure of the aortic and pulmonary valves
Why does a stenotic valve produce a murmur?
Stiff/narrowed valve doesn’t open completely
Blood is forced through the narrowed opening
(ejection murmur)
Why does a regurgitant valve produce a murmur?
Valve edges are scarred
Valve doesn’t close completely
Backflow of blood
What is the Ejection Fraction?
The proportion of LVEDV that is ejected
Why is left sided heart failure more common?
Higher workload
More pressure on the left side
How do you get right sided heart failure?(2)
Secondary - progressed from left sided - most common
Prolonged left ventricular failure can progress to right sided failure – biventricular or congestive cardiac failure
Primary - right side alone
Right ventricular failure usually happens because of a raised pulmonary vascular resistance
What are the two aspects of left ventricular pressure-volume relationship?
Filling - diastolic compliance
Ejecting - systolic contraction
What does the Frank-Starling relationship assume?
What factors explain this?
Assumes after load is constant
Greater contact of actin/myosin interaction
Greater sensitivity of myofibrils to calcium ions from the sarcoplasmic reticulum
Whats is the influence on ejection fraction of heart failure resulting from diastolic dysfunction?
Why is this the result?
Heart failure with preserved ejection fraction
Impaired myocardial relaxation
Heart cannot fill properly
Stiff, fibrotic ventricle - LVEDP rises - reduced stroke volume
Whats is the influence on ejection fraction of heart failure resulting from systolic dysfunction?
Why is this the result?
Heart failure with reduced ejection fraction
Impaired myocardial relaxation
Heart cannot empty properly
Weak ventricle - reduced stroke volume
What is the upstream effect of heart failure, why does this occur and what are the effects of this?
Increased upstream pressure in the circulation
Inability to keep up with the returning venous blood
The rise in hydrostatic pressure in heart failure leads to loss of fluid from the circulation - OEDEMA
In the lungs, the fluid accumulates in the alveoli – PULMONARY OEDEMA
What is the downstream effect of heart failure? What does this have a particular influence on?
Reduced perfusion of vital organs
Especially the kidneys
How is the kidney affected in heart failure?
reduces perfusion of the junta-glomerular cells
aldosterone released - sodium and water retention
angiotensin II released - vasoconstriction
What is the result of an increase in SVR(afterload) resulting from vasoconstriction?
reduced stroke volume
greater systolic contraction required
worsens an already failing heart
In what direction does the hydrostatic pressure cause fund to move?
Out of the blood vessel into the interstitial space
In what direction does the osmotic gradient cause fluid to move?
Pulls fluid into the blood vessel from the interstitial space
What are the main features affected in right sided heart failure?
JVP, Liver, Peripheries - oedema
What are the main features affected in left sided heart failure?
Lungs - pulmonary oedema
Kidneys - reduced renal function
What are some possible causes of heart failure?(8)
Ischaemic heart disease Valvular disease Intra-Cardiac shunts Arrhythmias Drugs Hypertension Cardiomyopathy Fluid overload
What is cardiomyopathy?
Diseases of the heart muscle
Becomes enlarged, think or rigid
How is myocardial ischaemia worsened in terms of coronary blood flow?
A rising wall tension from cardiac failure (especially LV in diastole) will worsen coronary flow / myocardial ischaemia
- coronary arteries occluded during ventricular contraction, most perfusion occurs during diastole
Tachycardia will worsen it further by reducing total diastolic time
What is the mortality of heart failure after diagnosis?
10% within 30 days
30% within 1 year
50% within 5 years
What are the typical symptoms of heart failure?
Breathlessness - on exertion, at rest, on lying flat (orthopnoea), nocturnal cough, or waking from sleep (paroxysmal nocturnal dyspnoea).
Fluid retention (ankle swelling, bloated feeling, abdominal swelling, or weight gain).
Fatigue, decreased exercise tolerance, or increased recovery time after exercise.
Light headedness or history of syncope.
What are the risk factors for hear failure?
Coronary artery disease including previous history of myocardial infarction, hypertension, atrial fibrillation, and diabetes mellitus.
Drugs, including alcohol.
Family history of heart failure or sudden cardiac death under the age of 40 years.
What do you examine for if you suspect heart failure?
Tachycardia (heart rate over 100 beats per minute) and pulse rhythm.
A laterally displaced apex beat, heart murmurs, and third or fourth heart sounds (gallop rhythm).
Hypertension.
Raised jugular venous pressure.
Enlarged liver (due to engorgement).
Respiratory signs such as tachypnoea, basal crepitations, and pleural effusions.
Dependent oedema (legs, sacrum), ascites.
Obesity.
How do you manage suspected heart failure?
Reduce or stop any drugs that could be worsening it
If symptoms are sufficiently severe, start a loopdiuretic such as:
Furosemide 20-40 mg daily.
Bumetanide 0.5-1.0 mg daily.
Torasemide 5-10 mg daily.
What is being assessed when testing cardiac function?
structure of the muscle
competency of the valves
rate and rhythm
What methods are used for physiological stress testing?
treadmill
bicycle ergonometer - patient stays still - less ECG interruption
can measure VO2 max
6 principle mechanisms of cardiac dysfunction
Pump failure: weak systole or poor diastolic relaxation
Flow obstruction: e.g. plaque in vessel, or prevention of valve opening or ↑ ventricular chamber pressure (aortic valvular stenosis, systemic hypertension, aortic coarctation - CHD)
Regurgitant flow: backward flow through incompetent valve
Shunted flow: blood diverted (e.g. congenital defects or acquired post MI)
Disorders of cardiac conduction: uncoordinated transmission of electrical impulses (arrythmias)
Rupture of heart or major vessel: aortic dissection & exsanguination
What does an Echocardiogram measure?
Chamber size
Muscle contractility
Valve function
done at rest
What are the portions for a focus assessed transthoracic echo?
position 1 - subcostal
position 2 - apical 4 chamber
position 3 - parasternal long axis
position 4 - pleural scanning
What is the first-line investigation for cardiac sounding chest pain?
CT coronary angiogram
What is used for 24hr ambulatory heart monitoring?
Holter ECG
What is ARVC and how is it managed?
Arrhythmogenic right ventricular cardiomyopathy
scar tissue replaces normal tissue
CMR
Implantable cardioverter-defibrillator
What is restrictive cardiomyopathy?
idiopathic
impaired ventricular filling during diastole
primary disease in ventricular compliance
