MRCP revision battle 34.1: The first heart sound

I've just had a whole week off revising.  Very bad from a passing MRCP point of view.  Very good from a remaining sane, keeping friends and staying up-to-date with all the other bits of paper medicine in the UK requires.  Since the exam is now under a month away however I'd better buckle down to it...


MRCP revision battle 34.1: The first heart sound
MRCP revision battle 34.2: The second heart sound
MRCP revision battle 34.3: The third and fourth heart sounds
MRCP revision battle 34.4: Sodium Valproate
MRCP revision battle 34.5: Salicylate overdose
MRCP revision battle 34.6: Haemodialysis in overdose
MRCP revision battle 34.7: Cyanide poisoning
MRCP revision battle 34.8: Phentolamine





MRCP revision battle 34.1: The first heart sound



The first heart sound is made by the closure of the mitral and tricuspid valves.



A loud S1 may be due to:

• mitral stenosis
• hyperdynamic states
• short PR

A soft S1 may be due to:

• long PR
• mitral regurgitation

A    s p l i t  S1 is caused by:

• RBBB
• LBBB
• VT 
• inspiration
• Ebsteins abnormality

A variable S1 is caused by:

• complete heart block
• AF

On to the second heart sound....

MRCP revision battle 34.2: The second heart sound

The second heart sound comprises of the closure of the aortic and pulmonary valves.They usually close <0.05secs apart and in alphabetical order, with the aortic valve closing first.



A loud S2 may be due to:

• systemic hypertension (=loud A2)
• pulmonary hypertension (=loud P2)
• tachycardia

A soft S2 may be due to aortic stenosis.



A  w i d e l y   s p l i t  second heart sound occurs in:

• RBBB
• deep inspiration
• mitral regurgitation
• pulmonary stenosis

A reverse split (=paradoxical split) second heart sound occurs in:

• LBBB
• severe aortic stenosis
• right ventricular pacing
• WPW type 2
• patent ductus arteriosus

Onwards for the third and fourth heart sounds...

MRCP revision battle 34.3: The third and fourth heart sounds

Third heart sound

Third heart sound, AKA gallop rhythm, can be perfectly normal in children and young adults.

It is due to passive filling of the ventricles when the atrioventricular valves open.


In the over 40s it is pathological and may indicate:

• mitral regurgitation
• VSD
• CCF
• constrictive pericarditis

S1          S2  S3

The sound of the 3rd heart sound may be remembered as 'Kentucky' or 'SLOSH-ing in'




Fourth heart sound

A 4th heart sound is caused by atrial contraction against stiff ventricles.

It occurs in:

• aortic stenosis
• HOCM
• hypertension

S4  S1     S2

It can be remembered as 'Tennessee' or  'a STIFF wall'




I thoroughly recommend this website to listen to them http://www.wilkes.med.ucla.edu/Rubintro.htm



Now away from cardiology and to a bit of pharmacology - sodium valproate....

MRCP revision battle 34.4: Sodium valproate

Sodium valproate is a drug used in epilepsy.


It is a P450 inhibitor.


It has the highest risk of birth defects of any of the anti-epileptic drugs.


Sodium valproate also has an impressive plethora of unfortunate side effects which often appear in MRCP questions:

• alopecia
• nausea
• gynaecomastia
• weight gain
• tremor
• hepatitis
• pancreatitis
• tetratrogenic
• ataxia
• thrombocytopenia

As always with long lists of side effects its probable best to try and imprint on your mind a cartoon image of an unfortunate patient who is suffering from all of these side effects.   Personally I have a bald man who has big breasts and a fat, pregnant stomach, who is walking along in an ataxic way, covered in bruises (from his thrombocytopenia and crashing into things with his ataxic gait) while also vomiting and pointing with his trembling fingers to his liver and pancreas.



On that pretty image, lets move on to battle 33.5...

MRCP revision battle 34.5: Salicylate overdose

Patients who have taken a salicylate overdose are potentially more interesting than those who have taken a paracetamol overdose as salicylate poisoning actually has early clinical features you can look out for,  such as:

• sweating
• tinnitus
• dizziness
• pyrexia
• hyperventilation

A blood gas should show a mixed respiratory alkalosis and metabolic acidosis, and potentially a low potassium.


The sweating and pyrexia are due to uncoupling of oxidative phosphorylation.




The effects of salicylate are dose related:

• 150mg/kg: mild
• 250mg/kg: moderate
• >500mg/kg: severe

Later features of salicylate poisoning include:

• renal failure
• hypo or hyperglycaemia
• seizures
• acidosis

Treatment:

• activated charcoal if within 1 hr
• correct acidosis with 1.26% sodium bicarb
• haemodialysis if:
• conc >700mg/l
• metabolic acidosis resistant to treatment
• acute renal failure
• pulmonary oedema
• seizures
• urinary alkalinization is rarely used and is contra-indicated in cerebral or pulmonary oedema

Lets move on to consider use of haemodialysis in overdoses in general...

MRCP revision battle 34.6: Haemodialysis in overdose

Haemodialysis is not helpful in removing a drug if:

• the drug has a large volume of distribution (eg amiodarone, paraquat)
• the drug is highly protein-bound (digoxin, phenytoin)

The drugs that are appropriate for haemodialysis can be remembered as BLAST:

• Barbituates
• Lithium
• Alcohol (methanol/ethanol)
• Salicylate
• Theophylline

Charcoal haemoperfusion may be considered for:

• paracetamol
• theophylline

Now for a touch of cyanide poisoning....

MRCP revision battle 34.7: Cyanide poisoning

Cyanide is used in insecticides, photography and found in some metals.


It's toxicity comes from inhibition of oxidising enzymes, which happily is reversible.


The classical features of cyanide poisoning are:

• brick red skin
• smell of bitter almonds

Acute signs of cyanide poisoning include:

• hypotension
• hypoxia
• headache
• confusion

Chronic signs of cyanide poisoning include:

• ataxia
• peripheral neuropathy
• dermatitis

Treatment is with 100% oxygen and IV dicolbalt edetate



Onwards for a very brief final battle of the day: phentolamine

MRCP revision battle 34.8: Phentolamine

Phentolamine is a non-selective alpha-antagonist.

Its main action is vasodilation due to alpha-1 blockade.



In the context of MRCP the most important snippet to remember is that phentolamine is used to treat adrenaline-induced ischaemia (eg idiot houseofficer uses lidocaine with adrenaline in ring block, what ya gonna do? or clumsy dentist stabs little finger with his anaesthetic needle and its going blue, how will you treat it?)


In a broader context it can also be helpful in hypertension due to phaeochromocytoma or cocaine.



Thats all for today, more tomorrow!