The Silent Death of the Young: Hypertrophic Obstructive Cardiomyopathy (HOCM)

You have a 14 year old male patient who experienced a syncopal episode. You quickly obtain a 12-lead and this is what you see:

Based off of the title, you can gather that this is hypertrophic obstructive cardiomyopathy (HOCM). This is the most common type of genetically transmitted cardiomyopathy. Many primary care physicians now acquire 12-leads on athletes in an effort to pick up this finding early. HOCM works by causing structural defects in myocytes and myofibril. This interferes with conduction which in turn causes the left ventricle and the septum to become asymmetrical and hypertrophied. These patients have poor diastolic filling. Due to the poor diastolic filling, patient’s hearts are often unable to keep up with physically demanding activities. This is an oxygen supply/demand issue. When patients are straining themselves (running to catch a bus or playing a sport), the oxygen demand increases and the heart isn’t able to keep up. This ultimately leads to ischemia and eventually deadly dysrhythmias. A lot of these patients will go into ventricular tachycardia and degenerate into ventricular fibrillation. If they’re lucky, they will spontaneously convert from ventricular tachycardia back into a sinus rhythm. Now what do you look for on the 12 lead?

  1. High voltage
  2. Deep narrow Q waves (most common in the lateral leads I, aVL, V5, V6 Note: can also occur in the inferior leads).

The 12-lead above is often interpreted by the monitor as: “sinus rhythm with LVH and an old lateral myocardial infarction.” Generally, LVH shouldn’t be diagnosed in patient’s under 40-45 y/o. Not saying it’s impossible, but it’s very unlikely that a 14 y/o has experienced an MI.

Key point: Infarction Q waves need to be 1/3 the size of the QRS complex and at least one box wide. Dagger Q waves can easily be 1/3 the size of the QRS complex but you’ll notice that they aren’t wide enough.

The hypertrophy of the ventricles and septum causes the high voltage you see on the 12-lead. The Q waves are sometimes called “dagger Q waves” because of how narrow they are. These Q waves look sharp and ominous…. They should remind you of Michael Myers standing behind someone with a knife.

Some symptoms include:

  1. Syncope
  2. Palpitations (secondary to an arrhythmia
  3. Dizziness
  4. Pre-syncope
  5. Chest pain

As with any patient, you need to conduct a thorough physical exam and history. Is there anyone in the patient’s family who has been diagnosed with HOCM? Any early familial deaths?

Now what does this patient need? Prehospital care includes keeping the patient calm and not allowing them move around a lot. Notify the hospital of your findings.

This next part is going to be more for the hospital folks and not as much for the prehospital medical professionals. So what do you look for on doppler ECHO?

You look for septal hypertrophy and an outflow obstruction by the left ventricle (due to it being asymmetrical). These patients need to get a doppler ECHO done as soon as possible. If this can’t be done for some reason, arrange an appointment with a cardiologist and advise them to basically be a couch potato. Beta blockers will slow down the heart and improve diastolic filling.

Emergency medicine and primary care are on the front lines of saving these patients. We must be skilled enough to catch this sign on the ECG. As the great educator Amal Mattu says “syncope and sudden death are the same disease along the spectrum of how lucky you are”.

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This site is meant to be used for educational use only. We strive to push evidence based medicine with no bias to help you obtain all the important information. You should always follow your protocols that have been set in place.

Scopeducation Team (Matt)


Hypertrophic Cardiomyopathy (HCM). (n.d.). Retrieved June 25, 2020, from

Raj, M. (2020, April 27). Hypertrophic Obstructive Cardiomyopathy. Retrieved June 25, 2020, from

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