Cardiac Amyloidosis Causes Concentric Hypertrophy
Amyloidosis causes concentric left ventricular hypertrophy, not eccentric hypertrophy. This is a defining characteristic that distinguishes it from other cardiomyopathies and is critical for early diagnosis.
Morphologic Pattern in Cardiac Amyloidosis
Cardiac amyloidosis results in progressive concentric increase in thickness of the left and right ventricular myocardium, interatrial septum, and atrioventricular valves 1. This pattern is consistent across all types of cardiac amyloidosis, including:
- Light chain (AL) amyloidosis 1
- Hereditary transthyretin (TTR)-related amyloidosis 1
- Wild-type (senile) TTR amyloidosis 1
The concentric pattern means the ventricular walls thicken uniformly in a circumferential manner, maintaining the normal geometric relationship of the left ventricular cavity 2. This contrasts with eccentric hypertrophy, where the chamber dilates with proportionally less wall thickening.
Diagnostic Imaging Characteristics
All patients with cardiac amyloidosis demonstrate concentric left ventricular hypertrophy and right ventricular hypertrophy on echocardiography 3. The specific features include:
- Mean left ventricular wall thickness >12 mm with no other known cardiac cause 1, 2
- Concentric thickening pattern affecting both ventricles 3
- Increased interatrial septum thickness (a specific feature suggesting amyloidosis) 2
- Increased atrioventricular valve thickness (helps differentiate from other causes of hypertrophy) 2
- Preserved ejection fraction in early stages (mean 49.3% in biopsy-proven cases) 3
The American College of Radiology recommends considering cardiac amyloidosis specifically in patients presenting with concentric thickening of the ventricles, atria, interatrial septum, and valves 2.
Clinical Context and Recognition
In patients with multiple myeloma or chronic inflammatory diseases, the concentric hypertrophy pattern should raise immediate suspicion for AL (light chain) amyloidosis 1. The key clinical scenario is:
- Unexplained heart failure with preserved ejection fraction 4, 5, 6
- Concentric left ventricular hypertrophy without adequate hypertensive history 4, 5
- Intolerance to antihypertensive medications 4
- Associated findings: carpal tunnel syndrome, spinal stenosis, or other orthopedic manifestations 4
The concentric type of hypertrophic cardiomyopathy can be challenging to distinguish from concentric hypertrophy caused by hypertension, aortic stenosis, infiltrative disorders, and athlete's heart 1. However, the combination of concentric hypertrophy affecting multiple cardiac structures (ventricles, atria, septum, valves) strongly suggests amyloidosis rather than pressure-overload hypertrophy 2.
Pathophysiologic Distinction
The wall thickening in cardiac amyloidosis is progressive and persistent, reflecting ongoing amyloid protein deposition in the extracellular space 2, 4. This infiltrative process causes:
- Increased myocardial stiffness 4
- Restrictive cardiomyopathy physiology 4, 5
- Diastolic dysfunction (present in 100% of patients, with 69.2% showing restrictive filling patterns) 3
This differs fundamentally from eccentric hypertrophy seen in dilated cardiomyopathy, where chamber dilation predominates with relative wall thinning 1.
Common Diagnostic Pitfalls
Do not assume that concentric hypertrophy with preserved ejection fraction is simply hypertensive heart disease 4, 5. If the degree of hypertrophy seems disproportionate to the hypertensive history, or if the patient shows intolerance to standard heart failure medications, pursue amyloidosis workup immediately 4.
The diagnosis requires exclusion of monoclonal gammopathies and technetium-99m pyrophosphate nuclear scintigraphy with SPECT imaging 4. In the appropriate clinical context with concentric hypertrophy and negative monoclonal protein studies, bone scintigraphy showing cardiac uptake is diagnostic for ATTR amyloidosis without requiring endomyocardial biopsy 1, 4.
Early recognition is critical because disease-modifying therapies (tafamidis for ATTR-CM) reduce cardiovascular mortality and hospitalization, particularly when started in early disease stages 7, 8.