Concentric hypertrophy

Concentric hypertrophy represents a specific form of hypertrophic growth observed in hollow organs, characterized by the thickening of the organ's walls without a concurrent increase in its overall size. This results in a reduced internal volume or capacity of the organ.

Gross pathology of left ventricular hypertrophy

FIGURA 10

Histopathology of moderate myocardial hypertrophy - boxcar nuclei

Definition and Characteristics

Concentric hypertrophy arises when sarcomeres, the basic units of muscle contraction, are added in a parallel manner, as seen in conditions like hypertrophic cardiomyopathy. While this process can be observed in multiple hollow organs, its most studied and clinically relevant manifestation occurs in the heart, where the muscle walls thicken in response to increased pressure.

Causes

The primary driver for concentric hypertrophy in the heart is the pressure overload. This overload can arise from various conditions, including:

• Hypertension: Chronic elevated blood pressure requires the heart to exert more force to pump blood, leading to wall thickening.
• Aortic stenosis: This is a narrowing of the aortic valve, creating resistance against which the heart must pump, again leading to hypertrophy.

Clinical Implications

The initial response of the heart to thickening its walls is an adaptive mechanism to reduce stress on the heart muscle. However, the prolonged presence of concentric hypertrophy has detrimental effects:

• Diastolic dysfunction: Thickened walls reduce the heart's flexibility, hampering its filling during the relaxation phase (diastole).
• Ventricular failure and systolic dysfunction: Over time, the heart's ability to contract effectively during the systole phase can also get compromised, leading to heart failure.

Relation to Laplace's Law

Laplace's law provides insights into the wall stress dynamics in spherical structures like the heart. It stipulates that the wall stress (T) is directly proportional to the product of transmural pressure (P) and the cavitary radius (r), while being inversely proportional to the wall thickness (W). Therefore, when the left ventricular wall thickens significantly in conditions like aortic stenosis — and the cavitary radius remains fairly stable — the observed increase in wall tension is mitigated. This phenomenon of adaptive wall thickening in response to increased pressure is termed "concentric hypertrophy."

See Also

• Cardiac muscle
• Cardiomyopathy
• Heart disease
• Cardiac physiology

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