• LVOTO by septal muscle hypertrophy
• similar pathophysiology and anaesthetic considerations to AS
• HOCM = hypertrophic obstructive cardiomyopathy
  • no longer used
• HCM = hypertrophic cardiomyopathy
  • preferred nomenclature
• very difficult Mx
  • can give fluid and metaraminol, but that's it
• crucial to maintain AL for coronary perfusion BECAUSE very high IVP
• HCM is different to LVH from Hypertensive Heart Disease (HHD) / other causes of LVOTO
  • HCM is genetic, septal LVH / LVOTO
  • the other causes can be considered "secondary HCM", but not in a strict aetiological sense

• LVH > 15 mm
  • asymmetric or localised LVH > 15 mm
• in the absence of another cause of LVH
• Echo + FH + ECG

• 33% have LVOTO at rest = Obstructive at rest = PG > 30 mmHg
• 33% have LVOTO on exercise = Labile = PG > 30 mmHg only on provocation
  • this is dynamic LVOTO
  • avoid precipitants / triggers
• 33% have non-obstructive phenotype = Non-obstructive = no LVOTO / PG < 30 mmHg

• Overview
  • most common purely genetic CV disease
  • prevalence ~ 1:200
• Incidence
  • once considered a rare disease of the young
  • now recognised as relatively common and in middle-aged and older adults (AHA 2020)
• Prevalence
  • 0.2-0.5% = 2-5:1000
• Gender

• commonest cause of sudden cardiac death in young
• most are asymptomatic with normal life expectancy
• prognostic profiles
  • benign / stable
  • AF / stroke
  • sudden cardiac death
  • heart failure

• considered a genetic disease

• Familial 70%

  • Autosomal dominant = 60% cases
  • variable penetrance

• 1500 mutations in 11 genes

• causes

  • primary = HCM
  • secondary = as below

• secondary causes

  • Acquired = HTN / AS / Athlete's heart
  • Congenital = Subaortic stenosis, LV noncompaction (LVNC, another CM)
  • Systemic disease = Fabry disease, cardiac amyloidosis, hypereosinophilic syndrom

• sarcomeric proteins
• hypertrophy
  • prone to ischaemia
  • primary problem = diastolic failure
• fibrosis
  • pro-arrhythmic > ventricular arrhythmias
• LVOTO
  • 20% involves hypertrophy of septum = LVOTO
  • interventricular septum hypertophy
    • this causes dynamic LVOTO
    • due to SAM = systolic anterior motion of the anterior leaflet of mitral valve
      • from drag forces in LVH LV lead to SAM
      • Anterior leaflet gets pulled into LVOT causing obstruction
    • with mitral-ventricular contact
    • SAM also typically results in MR (mild-mod, posterior direction)
  • elongated anterior mitral leaflet
  • abnormal papillary muscle anatomy
  • apicoseptal bands
  • obstruction is WORSE with
    • ⬆INO = exercise, ENS+
    • ⬇SVR = hypotension, vasodilator, eg. amyl nitrate
• arrhythmias (VT, AF)
• heart failure

• asymptomatic
  • often not diagnosed until a significant cardiac event
• sudden cardiac arrest
• DEA = dyspnoea, syncope, angina

• systolic murmur

• important to establish LVOTO
  • PG > 50 mmHg = surgical intervention
  • at rest
  • provocative manoeuvre = exercise, Valsalva, amyl nitrite
• echo
  • septal thickness > 15 mm
• cardiac MRI
  • better
• ECG
  • STD/TWI
  • LVH
  • Dagger Q waves inf-lat
  • Arrhythmias are common = AF / SVT

• Non-pharmacological
  • Avoid dehydration and excess alcohol
• Pharmacological
  • BB = relieve angina, dyspnoea
• Surgical
  • AICD = VT
  • septal ablation
  • myomectomy
  • cardiac TX

• Pre-op
  • defib pads before induction
  • continue BB
  • management plan for IED
  • management plan for ATT
• Intra-op
  • similar to AS
  • optimise HF therapy
  • optimise fluid balance
  • defend PL and AL
  • 1:PL
    • maintain PL for adequate SV
    • hypovolaemia exacerbates LVOTO, worsens MR = HDI / collapse
  • 2:HR
    • avoid ⬆HR (⬇diastolic filling = ⬇CO)
  • 3:rhythm
    • maintain SR
    • avoid ⬆HR and ⬇HR
  • 4:INO
    • avoid ⬆INO (will worsen LVOTO) ***
      • reduce contractility
    • avoid ketamine (⬆ENS)
  • 5:AL
    • Maintain AL for coronary perfusion
    • high LV luminal / intraventricular pressures = requires adequate SVR to maintain CPP
      • IVP may be 200+ if PG 120
    • Avoid ⬇SVR, will worsen LVOTO ***
• Post-op

• cardiac arrest
  • a-agonists, IVF, correct arrhythmias
  • AVOID inotropes

HCM and pregnancy

• usually well tolerated
• continue BB
• protect SR
• spinal is relatively CIN due to ⬇SVR
• EDB usually well tolerated
• tolerate 2nd stage well, as ⬆SVR helps HCM
• PPH = oxytocin ok, ergot great (⬆SVR)

HCM and intraoperative AF

• DCCV is best
• consider BB, eg. esmolol infusion

https://www.healio.com/cardiology/learn-the-heart/cardiology-review/topic-reviews/hypertrophic-obstructive-cardiomyopathy-hocm

Cardiomyopathy and anaesthesia, BJAE 2009

https://asecho.org/wp-content/uploads/2016/02/Freeman-Hypertrophic-Cardiomyopathy.pdf

https://www.anesthesiaconsiderations.com/hypertrophic-obstructive-cardiomyopathy-

Anesthetic management of a patient with hypertrophic cardiomyopathy with atrial flutter posted for percutaneous nephrolithotomy, 2015

https://www.uptodate.com.acs.hcn.com.au/contents/anesthesia-for-patients-with-hypertrophic-cardiomyopathy-undergoing-noncardiac-surgery

Temporal Trend of Age at Diagnosis in Hypertrophic Cardiomyopathy, Circulation: Heart Failure 2020