HOCM Long Case - Inter-College ED Presentation Prep

Your Case Summary (from the slides)

Deep-Dive: Apical HCM (Yamaguchi Syndrome)

What is Apical HCM?

• Accounts for ~10% of all HCM cases in Western populations; up to 25% in Japan/Asia
• Predominantly affects males (as in your case)
• Often non-obstructive - no LVOT gradient (your echo confirmed: no significant gradient across LVOT)
• LV cavity takes on the classic "Ace-of-Spade" shape on systolic angiography/echo - which your POCUS identified
• Generally considered to have a more benign prognosis than classical HCM, but still carries risk of sudden cardiac death, AF, and apical aneurysm formation
• The presentation in your patient (young male, exertional cardiac arrest, PEA) represents the serious end of the spectrum

Genetics

• Autosomal dominant, variable penetrance
• Most common mutations: MYH7 (beta-myosin heavy chain) and MYBPC3 (myosin-binding protein C), together accounting for 70-80% of all HCM
• Over 1,400 mutations identified across 9+ sarcomeric genes
• Gain-of-function mutations → myofilament hypercontractility → increased energy demand → compensatory hypertrophy and fibrosis
• Your patient had no family history of sudden cardiac death (important to highlight - it is a documented feature that ~50% of HCM patients have no identifiable family history)

Pathophysiology - Connecting to Your Case

ECG in Detail - Yamaguchi Pattern

• LVH voltage criteria (Sokolow-Lyon: SV1 + RV5/V6 > 35mm)
• Deep, narrow "dagger-like" Q waves in lateral (I, aVL, V5-6) and inferior leads (II, III, aVF) - these represent septal depolarization
• Q wave width < 40ms (vs. infarct Q waves which are > 40ms) - key differentiator
• Left atrial enlargement ("P mitrale")

• Giant negative T-waves (depth often > 10mm, up to 20-30mm) in precordial leads V3-V6, sometimes extending to I and aVL
• LVH voltage criteria
• NO dagger Q waves (because septum is spared)
• This pattern is the hallmark - sometimes the only finding prompting diagnosis

POCUS/Echo Findings - What the Examiners Will Ask

• Apical 4-chamber view: asymmetric LV apical hypertrophy
• Distal IVS thickness 17mm (normal <12mm)
• Ace-of-Spade sign - systolic obliteration of the LV apex giving a characteristic shape
• No LVOT obstruction (distinguishing apical from obstructive HCM)
• Grade II diastolic dysfunction
• LVEF 55-60% (preserved systolic function, typical of HCM)

Resuscitation - CPR Notes

• Airway: ETT 7.5mm secured during CPR
• Ventilation: CMV mode, TV 400ml, RR 18, PEEP 5, FiO2 100% → weaned to 40%
• Hemodynamics: BP 110/80, HR 100 - stable
• GCS improved E4VTM5 on transfer
• ABG on transfer: pH 7.32, PCO2 38, PO2 170, HCO3 16 - partially compensated metabolic acidosis

Management of HCM in ED (Key Points)

• Beta-blockers (metoprolol) - first line, decrease HR, improve diastolic filling, reduce LVOT gradient
• Non-dihydropyridine CCBs (diltiazem, verapamil) - if beta-blocker intolerant
• Disopyramide - sodium channel blocker, added for resting LVOT gradient reduction
• Phenylephrine (vasopressor of choice) - increases afterload without inotropic effect, maintains perfusion in hypotension
• Anticoagulation if AF develops (apixaban, rivaroxaban, dabigatran) - high stroke risk
• Amiodarone - drug of choice for AF and ventricular arrhythmias in HCM (your patient was started on amiodarone infusion post-ROSC)
• IV fluids - cautious use to maintain preload

• Septal myectomy (Morrow procedure) - surgical gold standard
• Alcohol septal ablation - catheter-based, controlled infarction of septal branch
• ICD implantation - secondary prevention after SCD/VT
• Dual-chamber pacing (DDD) - reduces outflow gradient, improves symptoms

Abnormal Labs in Your Case and Interpretation

Questions Faculty May Ask You

Basic/Foundational Questions

1. "What is the difference between HCM and HOCM? Why did we change the terminology?"

• HCM is the current preferred term. HOCM was used when obstruction was thought to be a defining feature, but only ~25% of cases have resting LVOT obstruction. The majority (75%) are non-obstructive, hence HCM is more accurate.

1. "What gene mutations cause HCM? What is the mode of inheritance?"

• Autosomal dominant, variable penetrance. Most common genes: MYH7 (beta-myosin heavy chain) and MYBPC3 (myosin-binding protein C), together 70-80% of cases. Gain-of-function mutations causing myofilament hypercontractility.

1. "How does HCM cause sudden cardiac death?"

• Cellular disarray creates an arrhythmogenic substrate. Ventricular fibrillation/VT triggered by exertion (sympathetic stimulation + decreased preload). Dynamic LVOT obstruction during exertion further compromises cardiac output. HCM is the #1 cause of sudden cardiac death in young athletes.

1. "What is the Yamaguchi pattern on ECG and how does it differ from classic HCM?"

• Yamaguchi (apical HCM): giant negative T-wave inversions in precordial leads V3-V6 (>10mm deep), LVH voltage, no dagger Q waves. Classic HCM: LVH + narrow "dagger-like" Q waves in lateral/inferior leads (septal depolarization signal), no giant T-wave inversions.

1. "How do HCM Q waves differ from MI Q waves?"

• HCM Q waves are narrow (< 40ms), seen in lateral leads, represent septal depolarization. MI Q waves are wide (> 40ms), follow a coronary territory distribution.

Applied/Clinical Questions

1. "Your patient had PEA. What reversible causes did you consider and how did you address them?"

• Go through the 5 H's and 5 T's, explain what was actively ruled out: PE by absence of risk factors, tamponade by POCUS (no effusion), tension pneumothorax by equal breath sounds, MI by history (young, no risk factors), toxins (no history), hypovolemia/hypoxia addressed immediately.

1. "Why is nitroglycerin contraindicated in HCM chest pain?"

• Nitroglycerin causes systemic vasodilation → reduces venous return (preload) → smaller LV cavity → worsens dynamic LVOT obstruction → hemodynamic collapse.

1. "Your patient was hypotensive. Why did you avoid dobutamine? What vasopressor would you use?"

• Dobutamine is a beta-agonist, increasing contractility and heart rate → worsens LVOT gradient. Phenylephrine (pure alpha-1 agonist) increases systemic vascular resistance without inotropic effect, maintains coronary perfusion pressure without aggravating outflow obstruction. IV fluids also used to improve preload.

1. "What is systolic anterior motion (SAM) of the mitral valve? Does your patient have it?"

• SAM is the movement of the anterior mitral leaflet into the LVOT during systole, caused by Venturi effect from blood flow past the hypertrophied septum. It causes variable MR and worsens LVOT obstruction. Your patient (apical HCM) likely did NOT have significant SAM since obstruction is at the apex, not the LVOT - confirmed by "no significant gradient across LVOT" on echo.

1. "The echo showed Grade II diastolic dysfunction. What does that mean? How do you grade it?"

• Grade I: impaired relaxation (E/A < 0.8, E' low). Grade II: pseudonormalization (E/A 0.8-1.5, PCWP elevated). Grade III: restrictive pattern (E/A > 2, E deceleration time < 160ms, PCWP markedly elevated). Grade II means moderately elevated filling pressures with partially compensated relaxation impairment - consistent with a symptomatic HCM patient.

1. "What is the Ace-of-Spade sign? Have you seen it in other conditions?"

• In apical HCM, during systole the hypertrophied apex obliterates the LV cavity, creating a distinctive spade-shaped cavity resembling the ace of spades on echo or ventriculography. This is considered pathognomonic for apical HCM.

1. "Why did you start amiodarone? What is the risk of not starting it?"

• Post-ROSC, this patient has known HCM with documented malignant arrhythmia (PEA/VF). Amiodarone is the drug of choice for both ventricular and supraventricular arrhythmias in HCM (per Rosen's). Without it, high risk of recurrent arrhythmia. It also provides rate control if AF develops.

Advanced/Examiner-Level Questions

1. "Should this patient get an ICD? What are the indications?"

• This patient had a survived cardiac arrest (secondary prevention) - Class I indication for ICD. Primary prevention ICD indications include: prior VT/VF, family history of SCD, unexplained syncope, LV wall thickness ≥ 30mm, hypotensive response to exercise, NSVT on Holter, extensive late gadolinium enhancement on MRI (≥ 15% of LV mass).

1. "What does cardiac MRI add to echo in HCM management?"

• Cardiac MRI gives accurate wall thickness measurements (especially apex, difficult on echo), identifies location and extent of fibrosis via late gadolinium enhancement (LGE). Extensive LGE (>15% LV mass) is associated with increased SCD risk and guides ICD implantation. MRI can also diagnose HCM when echo is inconclusive.

1. "This is a 21-year-old. What about family screening? What would you recommend?"

• First-degree relatives should undergo genetic testing + clinical screening (ECG + echo). If a pathogenic mutation is identified in the proband, cascade genetic testing is recommended. Even without genetic confirmation, clinical screening (ECG + echo) every 1-2 years for children and every 5 years for adults who remain asymptomatic.

1. "The hyperphosphatemia and hypocalcemia in your labs - what is the relationship?"

• Phosphorus and calcium have an inverse relationship. Hyperphosphatemia (11 mg/dL here) causes hypocalcemia via precipitation of calcium-phosphate complexes and suppression of vitamin D activation. Post-arrest rhabdomyolysis or acute kidney injury (Cr 1.6) can cause phosphate release, explaining the electrolyte abnormality.

1. "How would you differentiate apical HCM from Takotsubo (stress/Broken Heart) syndrome or apical ballooning syndrome in this ED setting?"

• Both can present post-stress with ECG changes (T inversions) and wall motion abnormalities. Key differences: Takotsubo has apical akinesis/hypokinesis with ballooning (thin walls), typically older females after emotional/physical stress, LVEF often reduced. Apical HCM has apical hypertrophy with thickened walls (IVS 17mm here), obliterated apex on systole (Ace-of-Spade), persistent LVH on ECG, young male. Your echo distinguishes them definitively.

1. "How does exercise worsen HCM symptoms?" (pathophysiology question)

• Exercise causes: (1) increased contractility and HR → worsened dynamic LVOT obstruction, (2) vasodilation → decreased afterload → more blood sucked out of LV → smaller cavity → Venturi effect worsens SAM, (3) tachycardia shortens diastolic filling time → worsened diastolic dysfunction, (4) increased oxygen demand in a supply-limited myocardium → ischemia. All these converge to cause syncope, dysrhythmia, and collapse during exertion.

Summary Points to Emphasize in Your Presentation

• This case demonstrates that HCM (especially apical variant) can present as the first clinical event being a cardiac arrest - no prior diagnosis, no family history
• The ECG was the key diagnostic clue even before echo - giant T-wave inversions in V1-V6 should immediately raise suspicion for apical HCM in a young patient post-arrest
• POCUS was diagnostic - done quickly in the ED post-ROSC, identified the Ace-of-Spade sign and 17mm IVS
• The Yamaguchi pattern is particularly important for ED physicians because it can be subtle and mistaken for ischemia or Takotsubo
• What you did right: Immediate CPR per AHA, airway secured during CPR, 5H5T evaluation, phenylephrine over dobutamine, amiodarone initiation, prompt cardiology and medicine referral
• Disposition: MICU admission appropriate; this patient needs ICD evaluation, cardiac MRI, genetic counseling, and family screening