BSOM Physiology: Cardiac Remodeling

Summary

This lecture dives into the different types of cardiomyopathies, focusing on heart failure caused by either systolic or diastolic dysfunction. It covers dilated cardiomyopathy, where heart contractility is impaired, leading to a larger ventricle and reduced cardiac output. The discussion moves on to diastolic dysfunction, marked by an inability to fill the heart adequately, often due to thickened myocardium. Additionally, restrictive cardiomyopathy is briefly mentioned, where myocardial tissue disruption prevents proper relaxation. Key mechanisms and pathophysiological processes are explored, helping students understand how to approach heart failure diagnosis and treatment.

Takeaways

• 😀 Heart failure refers to the heart's inability to generate proper cardiac output to meet the body's needs, which can be acute, chronic, or acute on chronic.
• 😀 Cardiomyopathies involve physical changes in the heart structure, categorized into two main dysfunctions: problems with filling (diastolic dysfunction) and problems with emptying (systolic dysfunction).
• 😀 Dilated cardiomyopathy is a type of systolic dysfunction where the ventricle becomes dilated and has reduced contractility, leading to decreased cardiac output despite increased preload.
• 😀 In dilated cardiomyopathy, the heart may show signs like cardiomegaly (enlarged heart) on an X-ray and an S3 heart sound, which indicates systolic failure.
• 😀 The S3 heart sound is heard during early diastole and is usually a sign of systolic failure, where the ventricle is overly compliant and fills excessively.
• 😀 Diastolic dysfunction occurs when the heart struggles with filling due to a thickened myocardium, leading to increased pressure without a significant increase in volume.
• 😀 Diastolic dysfunction can lead to heart failure with preserved ejection fraction (HFpEF), where the ejection fraction remains normal or even increased but preload is inadequate.
• 😀 Hypertrophy of the myocardium typically occurs in response to increased pressure or afterload, which can cause diastolic dysfunction by stiffening the heart muscle and limiting filling capacity.
• 😀 In cases of restrictive or infiltrative cardiomyopathy (e.g., amyloidosis), the myocardial tissues themselves are disturbed, leading to poor relaxation and diastolic dysfunction.
• 😀 Understanding the underlying pathophysiology of cardiomyopathies is essential for determining appropriate treatments for patients presenting with heart failure symptoms.

Q & A

What is the primary difference between heart failure and cardiomyopathies?

Heart failure refers to the heart's inability to generate a proper cardiac output to meet the body's needs. Cardiomyopathies, on the other hand, involve structural changes in the heart that can lead to heart failure.

What are the two main categories of heart problems based on structure?

Heart problems can be categorized based on issues with either filling or emptying the heart. These are termed diastolic dysfunction (problems with filling) and systolic dysfunction (problems with emptying).

What is dilated cardiomyopathy and how does it affect heart function?

Dilated cardiomyopathy is a type of systolic dysfunction where the heart's ventricle becomes dilated, leading to reduced contractility. This means the heart can't effectively pump blood, despite a large volume of blood filling the ventricle.

How does the Frank-Starling curve relate to dilated cardiomyopathy?

The Frank-Starling curve shows that an increase in preload typically increases cardiac output. However, in dilated cardiomyopathy, the heart loses its ability to contract properly, leading to an increase in preload but a decrease in cardiac output.

What are the key exam findings associated with dilated cardiomyopathy?

Key findings include cardiomegaly (an enlarged heart) visible on an X-ray, and an S3 heart sound, which is heard during early diastole in adults and indicates systolic heart failure.

What is an S3 heart sound, and what does it indicate?

The S3 heart sound is heard in early diastole and typically indicates systolic heart failure, where the ventricle is overly compliant and can accommodate extra volume.

What is the difference between diastolic dysfunction and systolic dysfunction?

Diastolic dysfunction is characterized by a problem with filling the heart due to a stiffened myocardium, while systolic dysfunction involves issues with the heart's ability to contract and pump blood effectively.

What is heart failure with preserved ejection fraction (HFpEF), and how does it occur?

HFpEF occurs when the heart can contract normally but cannot fill adequately due to a thickened myocardium. This results in a preserved ejection fraction but inadequate preload, leading to heart failure.

What factors lead to myocardial hypertrophy in diastolic dysfunction?

Myocardial hypertrophy occurs in response to increased pressure or afterload, often due to conditions like hypertension. In some cases, congenital defects can also lead to a thickened myocardium, contributing to diastolic dysfunction.

What is restrictive cardiomyopathy, and what causes it?

Restrictive cardiomyopathy is a type of diastolic dysfunction caused by infiltration or disturbance of myocardial tissue, often due to conditions like amyloidosis or after chemotherapy and radiation treatments.