HOCM for the Final SOE

• Dilated
• Restrictive
• Hypertrophic

• It is the most common genetic cardiac condition
• 1 in 500
• Double the incidence in men

• Autosomal dominant
• Penetrance and expression is variable

• Genetic mutations in sarcomeres and muscle fibres lead to left ventricular hypertrophy
• This means poor ventricular compliance and impaired ventricular filling during diastole, leading to diastolic dysfunction
• Septal hypertrophy and abnormal systolic anterior leaflet motion of the mitral valve cause dynamic left ventricular outflow obstruction
• The abnormal anterior leaflet leads to mitral regurgitation
• The hypertrophic muscle is disordered, predisposing to arrhythmias and has a huge oxygen requirement, leading to ischaemia

• Often completely asymptomatic and detected as an incidental finding
• Or it can present as sudden death

If there are symptoms present, they're usually:

• Chest pain
• Palpitations
• Syncope
• Exertional dyspnoea

Signs include:

• Hypotension
• Low volume pulse
• Left ventricular heave
• Ejection or pan systolic murmur

• Aortic stenosis
• Mitral insufficiency
• Glycogen or lysosome storage disease

• Family history of sudden death
• Left ventricular hypertrophy of greater than 30 mm
• Sustained runs of VT
• Abnormal heart rate or blood pressure response to exertion

• Left ventricular hypertrophy
• Left axis deviation
• Q waves suggestive of old infarct (often not actually an infarct, especially in young men, but looks like one)
• ST depression or T wave inversion if current ischaemia

• Left ventricular hypertrophy
• Septal hypertrophy
• Small left ventricle chamber size
• Dilated left atrium (as fluid backs up during diastole)
• Left ventricular outflow obstruction

Mitral valve

• Abnormal SAM of mitral valve
• Prolapse or regurgitation

Obstruction of blood flow through as it attempts to leave the ventricle into the aorta.

• In HOCM a dynamic obstruction is seen
• Bulky myocardium around the left ventricular outflow tract compresses the tract during systole, causing a temporary restriction to flow
• This is particularly likely if the patient has septal hypertrophy
• If there is significant obstruction, the velocity of the blood increases, and this drags the anterior leaflet of the mitral valve towards the septum (SAM)
• This then causes mitral regurgitation

• If the peak gradient is <30 mmHg then it is non-obstructive
• If peak gradient >30 mmHg on exertion/valsalva then it is labile obstruction
• If peak gradient >30 mmHg at rest, it's obstruction at rest

• Hypertrophy of the ventricle and septum, especially at the apex

• Genetic counselling and screening of first degree relatives

Pharmacological

• Beta blockers to reduce contractility
• Verapamil or diltiazem to reduce contractility
• Amiodarone to control arrhythmias
• Anticoagulation if in AF
• Treat as heart failure if ejection fraction <50% (ACEi, ARB, Spironolactone, SGLT2 inhibitors)

Avoid vasodilators and digoxin if evidence of LVOT obstruction.

Surgical and procedural

• Myotomy
• Myomectomy
• Mitral valve replacement
• Septal ablation (using alcohol)
• ICD to prevent sudden death
• Transplant

You need to think particularly about the risks of:

• Arrhythmia
• LVOT obstruction
• Ischaemia
• Heart failure
• Sudden death

If the patient is symptomatic prior to their operation, they are much more likely to suffer intra-operative problems as well.

Alongside a full anaesthetic history and examination, including your usual airway assessment, you should involve cardiology for advice on minimising perioperative risk.

General principles

• Maintain adequate preload (avoid prolonged dehydration, first on list)
• Reduce sympathetic tone (consider anxiolytic premedication)
• Regional anaesthesia carries risk of dropping SVR and is thus relatively contraindicated

Set up:

• Monitoring - ECG, Sats, BP
• Awake arterial line
• Consider defib pads
• If you have the facilities and skillset to use it, then transoesophageal echo can be useful too

Induction

• Lots of opioid to reduce hypnotic requirement
• Minimise tachycardia
• Maintain preload and SVR

Ventilation

• Lower tidal volume, lower PEEP, higher resp rate to avoid compression of venous return

Cardiovascular support

• Maintain sinus rhythm as much as possible
• Cautious fluids and vasopressors for hypotension
• Avoid inotropes that will increase myocardial oxygen demand
• If hypertensive, use beta blockers in favour of vasodilators

• Thorough pain control to reduce sympathetic drive
• Ensure normothermia
• Antiemesis
• Maintain hydration