Aortic Stenosis, Atrial Fibrillation, Cerebral Infarction Flashcards
What is aortic stenosis?
One of the most common and serious valve disease problems.
The narrowing of the aortic valve opening –> restricting blood flow from left ventricle to the aorta
What is normal function of aortic valve?
Opens to allow blood to exit the left ventricle, closes to prevent blood from passing back from aorta to left ventricle
What is it called when blood passes back to ventricle from aorta?
Regurgitation
What is the cause from birth of (congenital) aortic stenosis?
The valve may have 2 cusps (bicuspid) instead of the usual 3 cusps (tricuspid)
What is the cause gradually over the years of aortic stenosis?
Valve becomes calcified (deposition of calcium causing stiffening) and narrowed (stenosed)
What is effect on left ventricle of aortic stenosis?
Left ventricle has to generate more force (pressure) to eject blood through the narrowed aortic valve and becomes more muscular (hypertrophied)
What is the thickening of muscle fibres called when the body has been stressed?
Hypertrophy
Who is mainly affected by aortic stenosis?
Males over the age of 65. Can cause no symptoms for many years
What are the symptoms of aortic stenosis?
SAD
S - Syncope (light-headedness, with exercise)
A - Angina type chest pain (worse with exercise)
D - Dyspnoea (breathlessness, with exercise)
What are the clinical signs of aortic stenosis relating to heart murmur?
Harsh and loud ‘ejection systolic’ heart murmur heard loudest in the top right side of the chest (aortic area)
Aortic area –> right side, between 2nd and 3rd rib (2nd intercostal space)
What are systolic heart murmurs?
Ejection murmurs are murmurs that may arise from narrowing of the semilunar valves or outflow tracts
Systolic murmur begins during or after first heart sound and ends before or during second heart sound
What is effect on pulse pressure during aortic stenosis?
Reduced pulse pressure (difference between systolic blood pressure and diastolic blood pressure)
Normally 120/70 mmHg (50 mmHg difference) changed to 110/90 mmHg (20 mmHg difference)
What is clinical signs during aortic stenosis relating to apex beat?
Forceful apex beat –> felt on left side of chest in mid-clavicular line, 5th intercostal space
Due to hypertrophied LV
What would the abnormal test results of ECG and echocardiogram be during aortic stenosis?
ECG –> evidence of more muscular left ventricle (QRS is increased in size)
Echocardiogram –> shows a narrowed aortic valve and a more muscular left ventricle
What is an echocardiogram?
Ultrasound scan of the heart
When is medical/surgical intervention required for aortic stenosis?
- If pressure difference between left ventricle and aorta remains below 60 mmHg then the patient is kept under observation
- If the left ventricle starts to dilate then surgery is considered
- Aortic valve can be replaced by open chest surgery or using a percutaneous (through skin and via femoral artery) approach
How are surgical valves made?
Either made of metal and plastic (prosthetic) or are pig valves (tissue valves)
What do patients with metallic artificial aortic (and other) valves require after treatment?
Life-long anticoagulant treatment with warfarin
What do patients with tissue valves require after treatment?
Do not require warfarin
What is atrial fibrillation?
Quivering or irregular heartbeat (arrhythmia) characterised by rapid and irregular beating of atrial chambers of heart
The heart is taken out of normal sinus rhythm due to production of electrical impulses originating from the atrial myocytes
What anatomical structures does atrial fibrillation involve?
- Left and right atria of the heart
- Pulmonary veins where meet the left atrium
What is physiologically affected in AF?
- Pacemaker activity of heart (SA node)
- Conduction of electrical depolarisation through atrium
- Stimulation of electrical activity in ventricles
In AF –> atria contract randomly and abnormal electrical impulses start firing in the atria and override heart’s natural pacemaker
What structural abnormalities are present in AF?
- Dilated atria
- Fibrosis (scarring) of atrial muscle
What physiological abnormalities are present in AF?
Pacemaker of heart (SA node) overwhelmed by disorganised atrial electrical discharge (often originating at pulmonary vein insertion)
What prior events could to lead to AF?
- Hypertension (high blood pressure)
- 1ary heart diseases (including coronary artery disease)
- Lung diseases (pneumonia, lung cancer, pulmonary embolism)
- Excessive alcohol consumption
- Hyperthyroidism (overactive thyroid gland)
- Heart failure
What is the difference between atrial flutter and atrial fibrillation?
Similar but rhythm in flutter is more organised and less chaotic
What are symptoms of AF?
- Palpitations (fast, irregular or both)
- Tired / breathless with exercise
- Chest tightness (angina) or ankle swelling (oedema)
What are clinic signs of AF?
- Irregular pulse (irregularly irregular i.e.g random strength and rate)
- Signs of underlying cause (high blood pressure, lung disease, valve murmur, weight loss)
What would weight loss during AF be induced by?
Hyperthyroidism
How would medical intervention be used to control heart rate during AF? What is this achieved by?
Seeks to slow down the heart rate to prevent symptom of
palpitations and to improve efficiency of heart beat
This is achieved with drugs (e.g. beta blockers, calcium channel blockers,
digoxin)
How would heart rhythm be controlled during AF?
Seeks to convert the heart rhythm back to normal, regular
sinus (pacemaker) rhythm
This may be achieved with drugs (e.g. amiodarone) or by an electrical shock
treatment called DC (direct current) cardioversion
Why does electrically isolating / insulating pulmonary veins help in AF?
From the left
atrium by surgery or catheter (tube placed in heart from arm or leg) ablation
(use of an energy pulse to make atrial cells unable to conduct electricity
How can AF be treated?
- Treat underlying cause (high blood pressure, lung disease etc)
- Avoidance of excess alcohol, caffeine, stimulants
How can formation of blood clots in atrium associated with AF be treated?
Direct oral anticoagulant or warfarin
How can AF lead to stroke?
Chaotic rhythm may cause blood to pool in your heart’s upper chambers (atria) and form clots. Could dislodge from your heart and travel to your brain. There it might block blood flow, causing a stroke.
What is cerebral infarction?
An area of necrotic tissue in the brain resulting from a blockage or narrowing in the arteries supplying oxygen to the brain. The restricted oxygen due to the restricted blood supply causes an ischemic stroke that can result in an infarction if the blood flow is not restored within a relatively short period of time
What anatomical structures are affected in cerebral infarction?
- All parts of the brain (right or left cerebral infarction)
- Arteries to brain
- Large and small arteries within brain
What arteries to the brain are affected in cerebral infarction?
Internal and external carotid, vertebral arteries
What structural abnormalities can result in cerebral infarction?
- Disease of wall of arteries going to or within brain
Which arteries are problematic will determine which area of the brain is affected
- Dilated atria of the heart (with AF) that allows clots to form
What can disease of wall of arteries going to or within brain be caused by?
Atherosclerosis caused by cholesterol and inflammatory cells
What are in brain due to cerebral infarction?
- Ischaemia (reduced blood /oxygen supply) of brain tissue
- Necrosis (death of cells) of brain tissue
- Raised intracranial (within skull) pressure due to brain swelling (oedema) which can further damage nerve cells
What is ischaemia?
Inadequate supply of blood to organ or part of body, especially heart muscles
What risk factors can lead to cerebral infarction?
- Smoking, high blood pressure, high cholesterol, diabetes (cardiovascular risk
factors) - Atrial fibrillation (clot)
- Possible warning TIAs
How can atrial fibrillation lead to cerebral infarction?
Blood not pumped properly and pools in atria to form a clot which can travel to brain and block flow to part of brain which can result in stroke
What are TIAs?
Transient ischaemic attack –> a reversible ‘mini stroke’ that does no lasting obvious damage. Caused often by very small blood clots that temporarily block an artery.
What are symptoms of cerebral infarction?
- Weakness of the arm and / or leg – usually on one side of the body
- Slurring of speech (dysarthria)
- Drooping of corner of mouth
- Difficulty swallowing (dysphagia)
- Inability to find the right words to speak (expressive dysphasia)
- Inability to understand the words of others (expressive dysphasia)
What is dysarthria?
Slurring of speech
What is dysphagia?
Difficulty swallowing
What is expressive dysphasia?
Inability to find right words to speak / inability to understand words of others
What are clinical signs of cerebral infarction?
- Possible evidence of atrial fibrillation (irregular pulse)
- Possible high blood pressure (hypertension)
- Possible bruit (noise of turbulent blood flow caused by atherosclerosis with
narrowing) heard over a carotid artery in the neck
What may ECG show in cerebral infarction?
May show evidence of atrial fibrillation (irregular heart
beat with absent “P waves”)
What may echocardiogram of heart show in cerebral infarction?
May show evidence of a blood clot in the atrial appendage
What would ultrasound of carotid artery show in cerebral infarction?
May show evidence of narrowing (atherosclerosis
plaque caused by cholesterol)
What would brain CT or MRI show in cerebral infarction?
Shows changes of brain ischaemia (reduced blood flow) swelling and infarction (necrosis or death or brain cells)
What drugs can be given during cerebral infarction and why?
Thrombolytic drugs (dissolve blood clot from within artery and restoring flow)
What are thrombolytic drugs?
Dissolve blood clot from within artery and restore blood flow
How can patients with AF be treated?
Direct oral anticoagulant or warfarin
How can patients with carotid atherosclerosis be treated?
With antiplatelet drugs (aspirin)
What are the clinical signs of aortic stenosis?
- Harsh and loud ejection systolic murmur
- Forceful apex beat
- Reduced pulse pressure
What are the abnormal test results of aortic stenosis?
- ECG (QRS increased)
- Echocardiogram (narrowed aortic valve and more muscular LV)
What are abnormal ECG results in atrial fibrillation?
No p waves as SA node not functioning –> instead replaced by fibrillatory waves (look like squiggly lines)
Normal QRS complex
Why does an ECG in AF show fibrillatory waves?
Atria generating lots of stimuli where each can be picked up by ECG
Why is there irregular rhythm in AF?
Not all stimuli are strong enough to depolarise AV node hence irregular rhythm –> irregular gaps in ECG
Why is QRS normal in AF?
AV node not affected so ventricles contract normally
Where is AF thought to be initiated?
In the myocardial sleeves of the pulmonary veins –> presence of automaticity in cells within myocardial tissues of the pulmonary veins
Pacemaker activity from these cells is thought to initiate AF
