Cardiac Hypertrophy: Eccentric vs. Concentric
Basic Definitions
Concentric hypertrophy occurs when the heart muscle walls thicken inward without the chamber enlarging, like adding layers to make the walls stronger but keeping the room size the same. 1 This happens when the heart faces increased pressure, such as in high blood pressure or aortic stenosis (a narrowed heart valve). 2
Eccentric hypertrophy occurs when the heart chamber enlarges and stretches outward, with the walls thickening proportionally to maintain the larger space. 1 This develops when the heart faces increased volume, such as in aortic regurgitation (a leaky heart valve) or chronic anemia. 2
How They Develop at the Cellular Level
Concentric Hypertrophy (Pressure Overload)
- Heart muscle cells (myocytes) add contractile units (sarcomeres) in parallel, making each cell thicker rather than longer 3
- The wall thickens without chamber volume increasing 1
- Systolic wall stress (pressure during contraction) is the primary trigger 4
Eccentric Hypertrophy (Volume Overload)
- Heart muscle cells add sarcomeres in series, making each cell longer rather than thicker 3
- The chamber enlarges and both internal and external circumferences increase 1
- Diastolic wall stress (pressure during filling) is the primary trigger 4
Key Structural Differences
Concentric hypertrophy creates an elliptic (oval-shaped) left ventricle with normal stroke volume but high peripheral vascular resistance. 5 The heart becomes more compact and muscular.
Eccentric hypertrophy creates a more spheric (round) left ventricle with increased stroke volume and lower peripheral vascular resistance. 5 The heart becomes enlarged and dilated.
Associated Tissue Changes
Concentric Hypertrophy
- More significant fibrosis (scarring) develops 4
- Greater apoptosis (cell death) occurs 4
- Activation of multiple stress-related signaling pathways (MAPK, β-arrestin-2, Akt) 4
Eccentric Hypertrophy
- More significant angiogenesis (new blood vessel formation) occurs 4
- Milder activation of stress-related signaling pathways 4
- Better preserved ultrastructure and contractile performance initially 2
Clinical Implications
Eccentric hypertrophy in conditions like aortic stenosis carries worse prognosis than concentric patterns, with increased heart failure readmissions and all-cause mortality. 6 This contradicts older assumptions that concentric patterns were uniformly worse.
In heart failure with reduced ejection fraction, patients with concentric hypertrophy show distinctly different biomarker patterns (elevated inflammatory markers like TNF receptor 1) compared to eccentric hypertrophy (elevated natriuretic peptides). 7 Beta-blocker up-titration provides mortality benefit in eccentric but not concentric hypertrophy patterns. 7
Reversibility
Some forms of eccentric hypertrophy are reversible when the stimulus is removed early enough, such as pregnancy-related changes or exercise-induced enlargement. 1 Early correction of aortic regurgitation can also allow regression. 1
Important Caveat
The terms "concentric" and "eccentric" can be confusing because the hypertrophy itself is actually concentric (uniform) in both cases—the difference lies in whether chamber volume increases (eccentric) or remains normal (concentric). 2 These are fundamentally different biological responses to distinct mechanical stresses, not simply variations of the same process.