HOCM

Question 1

What is hyperrophic obstructive cardiomyopathy?

Answer 1

• Autosomal dominant disorder of muscle tissue caused by defects in the genes encoding contractile proteins
• Estimated prevalence is 1 in 500
• HOCM is important as it is the most common cause of sudden cardiac death in the young

Question 2

What is the pathophysiology of HOCM?

Answer 2

1. Most common defects involve a mutation in the gene encoding β-myosin heavy chain protein or myosin-binding protein C
2. Results in predominantly diastolic dysfunction
3. Left ventricle hypertrophy → decreased compliance → decreased cardiac output
4. Characterized by myofibrillar hypertrophy with chaotic and disorganized fashion myocytes (‘disarray’) and fibrosis on biopsy

Question 3

What are the features of HOCM?

Answer 3

• Often asymptomatic
• Exertional dyspnoea
• Angina
• Syncope:
  
  • typically following exercise
  • due to subaortic hypertrophy of the ventricular septum, resulting in functional aortic stenosis
• Sudden death (most commonly due to ventricular arrhythmias), arrhythmias, heart failure
• Jerky pulse, large ‘a’ waves, double apex beat
• Ejection systolic murmur:
  
  • increases with Valsalva manoeuvre and decreases on squatting
  • hypertrophic cardiomyopathy may impair mitral valve closure, thus causing regurgitation

Question 4

What are diseases are associated with HOCM?

Answer 4

• Friedreich’s ataxia
• Wolff-Parkinson White

Question 5

What are the ECHO findings of HOCM?

Answer 5

• Mitral regurgitation (MR)
• systolic anterior motion (SAM) of the anterior mitral valve leaflet
• Asymmetric hypertrophy (ASH)

Question 6

What are the ECG findings of HOCM?

Answer 6

1. Left ventricular hypertrophy
2. Non-specific ST segment and T-wave abnormalities, progressive T wave inversion may be seen
3. Deep Q waves
4. Atrial fibrillation may occasionally be seen

Question 7

What is the management of HOCM?

Answer 7

Management:

Amiodarone

Beta-blockers or verapamil for symptoms

Cardioverter defibrillator

Dual chamber pacemaker

Endocarditis prophylaxis*

Drugs to avoid:

• nitrates
• ACE-inhibitors
• inotropes

Question 8

What is hypothermia?

Answer 8

Unintentional reduction of core body temperature below the normal physiological limits

• Mild hypothermia: 32-35°C
• Moderate or severe hypothermia: < 32°C

Question 9

What are some causes of hypothermia?

Answer 9

• Exposure to cold in the environment is the major cause
• Inadequate insulation in the operating room
• Cardiopulmonary bypass
• Newborn babies.

Question 10

What are risk factors of hypothermia?

Answer 10

• General anaesthesia
• Substance abuse
• Hypothyroidism
• Impaired mental status
• Homelessness
• Extremes of age

Question 11

What are signs of hypothermia?

Answer 11

• Shivering
• Cold and pale skin. Frostbite occurs when the skin and subcutaneous tissue freeze, causing damage to cells.
• Slurred speech
• Tachypnoea, tachycardia and hypertension (if mild)
• Respiratory depression, bradycardia and hypothermia (if moderate)
• Confusion/ impaired mental state

Question 12

What are signs of hypothermia in a newborn?

Answer 12

• Babies with hypothermia can look healthy
• However, they may be limp, unusually quiet and refuse to feed
• Heat loss in newborns is extremely common, hence a hat and clothing/blankets will be applied soon after birth

Question 13

What investigations needed in hypothermia?

Answer 13

• Temperature: Special low-reading rectal thermometers or thermistor probes are preferred for measuring core body temperature. The patient’s temperature should be tracked over time, to check for improvement
• 12 lead ECG: As the core temperature approaches 32°C to 33°C, acute ST-elevation and J waves or Osborn waves may appear
• Bloods:
  
  • ​FBC, serum electrolytes
  • Haemoglobin and haematocrit can be elevated (due to haemoconcentration)
  • Platelets and WBCs are low due to sequestration in the spleen
  • Monitoring potassium is advised as hypothermic patients can be hypokalaemic due to a shift of potassium into the intracellular space
• Blood glucose: Stress hormones are increased, and the body can have more peripheral resistance to insulin
• Arterial blood gas
• Coagulation factors
• Chest X-ray

Question 14

What is the initial management of hypothermia?

Answer 14

• Removing the patient from the cold environment and removing any wet/cold clothing,
• Warming the body with blankets
• Securing the airway and monitoring breathing,
• If the patient is not responding well to passive warming, you may consider maintaining circulation using warm IV fluids or applying forced warm air directly to the patient’s body

Question 15

What is the danger of rapid rewarming in hypothermia?

Answer 15

• Can lead to peripheral vasodilation and shock
• In severe cases, be prepared to conduct CPR
• IV drugs should be avoided if possible, as the patient is more likely to have a drastic response to the drug.

Question 16

What should you not do in hypothermia?

Answer 16

Due to the risk of cardiac arrest:

• Don’t put the person into a hot bath.
• Don’t massage their limbs.
• Don’t use heating lamps.
• Don’t give them alcohol to drink.