Hypertrophic Cardiomyopathy Does NOT Typically Cause Septal Hypokinesia
Classic HCM is characterized by a hypertrophied, hypercontractile left ventricle with preserved or increased ejection fraction, not hypokinesia of the septum 1, 2. The septum in typical HCM demonstrates vigorous, often excessive contraction rather than reduced motion.
Why the Septum is Typically Hyperkinetic in HCM
The fundamental pathophysiology involves hypercontractility: HCM is defined by a nondilated left ventricle with preserved or increased ejection fraction, indicating enhanced rather than diminished contractile function 1, 2.
Asymmetric septal hypertrophy is the hallmark: The most common pattern involves severe hypertrophy of the basal interventricular septum, which contracts vigorously and can create dynamic left ventricular outflow tract obstruction 2, 3.
The obstruction mechanism requires active septal contraction: While historically thought to be caused by systolic contraction of the hypertrophied basal septum encroaching on the LVOT, the septum must be actively contracting (not hypokinetic) to contribute to the dynamic obstruction 4.
When Septal Hypokinesia DOES Occur in HCM: Red Flags for Advanced Disease
Global LV hypokinesia (including the septum) can occur in advanced or "end-stage" sarcomeric HCM, representing disease progression with adverse prognosis 4.
Critical distinguishing features when hypokinesia is present:
This represents the "burned-out" phase: Advanced sarcomeric HCM can progress to global LV hypokinesia with or without LV dilatation, indicating transition to a dilated cardiomyopathy phenotype 4.
Alternative diagnoses must be considered: According to the 2014 ESC Guidelines, global LV hypokinesia should prompt evaluation for phenocopies including mitochondrial disease, TTR-related amyloidosis, PRKAG2 mutations, Danon disease, myocarditis, Anderson-Fabry disease, or Noonan syndrome 4.
This finding carries prognostic significance: The presence of reduced ejection fraction with restrictive physiology suggests infiltrative disease or storage disorders rather than typical sarcomeric HCM 4.
Clinical Pitfalls to Avoid
Do not diagnose typical HCM if septal hypokinesia is present at initial evaluation: The combination of septal hypertrophy with hypokinesia should trigger a comprehensive workup for HCM phenocopies, particularly infiltrative or storage diseases 4.
Regional wall motion abnormalities may indicate ischemia: Severe myocardial ischemia and even infarction can occur in HCM due to supply-demand mismatch from intramural arteriolar disease, which could cause segmental hypokinesia 4.
Post-septal reduction therapy is an exception: Following surgical myectomy or alcohol septal ablation, iatrogenic septal hypokinesia or akinesia is expected and does not represent the natural disease state 4.
Diagnostic Algorithm When Encountering Septal Hypertrophy with Hypokinesia
Assess global versus regional dysfunction: Global hypokinesia suggests advanced HCM, phenocopy, or alternative diagnosis; regional hypokinesia suggests ischemia or prior intervention 4.
Evaluate for infiltrative disease markers: Look for sparkling/granular myocardial texture, pericardial effusion, thickened interatrial septum, and restrictive physiology on echocardiography 4.
Obtain cardiac MRI with late gadolinium enhancement: Pattern of LGE can distinguish sarcomeric HCM (RV insertion points, segments of maximum thickness) from amyloidosis (diffuse subendocardial) or other infiltrative diseases 4, 5.
Consider genetic testing and specialized metabolic workup: If hypokinesia is present with hypertrophy, testing for storage diseases (Fabry, Danon, Pompe) and infiltrative conditions becomes essential 4.