Description

1. Introduction

Hypertrophic cardiomyopathy (HOCM) is a genetic myocardial disease characterized by unexplained left ventricular hypertrophy (LVH) in the absence of secondary causes such as hypertension, valvular obstruction, or infiltrative disease. Today, HOCM is understood not merely as a structural cardiomyopathy but as a molecular disorder of the sarcomere, producing a cascade of biomechanical, microvascular, and electrical abnormalities.

Its anesthetic significance is profound:

Why HOCM Is High-Risk for Anesthesia

• Dynamic LVOT obstruction that worsens with standard anesthetic actions

• Extreme preload dependence

• Catastrophic hemodynamic collapse possible from routine triggers such as induction, intubation, spinal anesthesia, pneumoperitoneum, positioning, or emergence

• Substrate for malignant ventricular arrhythmias

• Sympathetic surges (pain, intubation, hypoxia) can precipitate collapse

• Frequent misdiagnosis and mismanagement, especially in hypotension

HOCM is an “inversion physiology disease”:
Almost everything anesthesiologists instinctively do in hypotension (give inotropes, lower afterload, use ephedrine) worsens the patient.

Clinical Orientation Box — How to Think Like an Anesthesiologist in HOCM

HOCM is the one cardiac condition where the following reflex actions can cause cardiac arrest:

• Giving inotropes

• Treating hypotension with ephedrine

• Reducing afterload with vasodilators

• Allowing tachycardia

• Allowing hypovolemia or aggressive diuresis

• Giving a single-shot spinal

The central mental model:

Any intervention that makes the LV smaller, faster, or stronger will worsen obstruction.
Any intervention that makes it fuller, slower, and less contractile will improve hemodynamics.

References

1. Maron BJ, Gardin JM, Flack JM, et al. Prevalence of HCM. Circulation. 1995;92:785-789.

2. Maron MS, Rowin EJ, Casey SA, et al. Risk stratification in older HCM. Circulation. 2013;127:585-593.

2. Molecular Biology, Sarcomere Dysfunction, and Genetic Basis

2.1 Sarcomeric Protein Mutations: The Root Cause

HOCM arises primarily from autosomal dominant mutations in sarcomeric contractile proteins, including:

• MYH7 – β-myosin heavy chain

• MYBPC3 – myosin binding protein C

• TNNT2 – troponin T

• TNNI3 – troponin I

• TPM1 – α-tropomyosin

• ACTC1 – cardiac actin

These mutations affect:

A. Cross-Bridge Cycling

Mutant myosin has increased ATPase activity, generating excessive force and triggering compensatory hypertrophy.

B. Myofilament Calcium Sensitivity

Increased Ca²⁺ sensitivity means:

• More contraction for the same Ca²⁺

• Impaired relaxation → diastolic dysfunction

• Elevated intracellular Ca²⁺ in diastole → arrhythmogenic effects

C. Energetics and Mitochondrial Stress

HOCM myocardium is energy-starved, showing:

• ↓ Phosphocreatine/ATP...