Systolic vs. Diastolic Heart Failure

Introduction

This lesson focuses on the differences between systolic and diastolic heart failure.
Heart failure involves decreased cardiac function, leading to insufficient blood flow.
Underlying processes determining systolic vs. diastolic failure are not fully understood.

Systolic Heart Failure

Problem with systole (contraction).
Inability of the heart to pump with enough force to meet the body's demands.
Decreased force of contraction = decreased contractility = decreased inotropy.
Decreased stroke volume leads to decreased cardiac output due to decreased force of contraction.
Ejection Fraction (EF):
- Normal EF: 50-70%.
- Systolic heart failure: EF < 40%.
Weakened heart muscle and enlarged ventricles.
Underlying disease leads to muscle cell death, decreasing contraction and ejection.
Compensation mechanisms, such as increased preload, stretch ventricles, which, with less muscle cells, leads to enlarged ventricles.

Causes of Systolic Heart Failure

Decreased Blood Supply to the Heart:
- Most common cause.
- Coronary artery disease impairs blood flow, leading to cardiac muscle cell death.
- Weakened heart leads to compensation, negative feedback, and progression.
Heart Muscle Disease:
- Dilated cardiomyopathy.
- Can be genetic or due to compensatory mechanisms increasing preload.
- Enlarged chambers with weak muscle.
Valve Disease:
- Regurgitation:
  - Incompetent valve (e.g., mitral or tricuspid).
  - Blood flows backward during contraction, decreasing ejected blood.
- Stenosis:
  - Incompetent aortic or pulmonic valves.
  - Smaller pathway for blood ejection.
  - Heart works harder, leading to less ejected blood.
- Both lead to decreased cardiac output.
- Body attempts to increase workload, leading to increased demand on cardiac muscle cells.
- Cell death and weaker heart.
Arrhythmias:
- Too slow, too fast, or uncoordinated.
- Dis-synchrony between ventricles or abnormal rate decreases cardiac output.
- Compensatory mechanisms don't work in heart failure.

Systolic Heart Failure Cycle:

Underlying disease → muscle cell death → decreased pumping ability/force of contraction → decreased cardiac output → compensation → increased workload → increased demand → cell death → decreased force of contraction.
Less muscle cells.

Diastolic Heart Failure

Problem with diastole (filling).
Heart unable to pump enough blood to meet demands due to impaired filling.
Reduced preload.
Hypertrophy occurs, with thicker muscle walls reducing ventricle size.
Limited blood ejection.
Normal ejection fraction (EF) can occur.

Example:

Normal heart: 100 mL ejected from 200 mL volume = 50% EF.
Diastolic heart failure: 50 mL ejected from 100 mL volume = 50% EF.
Normal EF doesn't guarantee sufficient cardiac output.

Myocardial Hypertrophy:

Muscle cells die, leading to remodeling.
Remaining cells enlarge, and the body creates more cells.
Large muscle walls reduce space for filling.

Causes of Diastolic Heart Failure

Hypertension:
- Chronic hypertension constricts blood vessels.
- Heart works harder to pump against resistance.
- Muscle growth leads to forceful contraction.
Stenosis:
- Aortic stenosis reduces valve opening size.
- Heart works harder to eject blood.
- Leads to muscle cell growth.
Restrictive Cardiomyopathy:
- Dead muscle cells lead to fibrotic scar tissue.
- Decreased compliance reduces stretch and filling.
Hypertrophic Cardiomyopathy:
- Genetic myocardial hypertrophy.
- Larger muscle walls reduce ventricle size and filling ability.
Other Causes:
- Coronary artery disease, age, etc.

Diastolic Heart Failure Cycle

Underlying disease leads to death of cardiac muscle cells, decreased force of contraction, decreased cardiac output, increasing workload through compensation, increased oxygen demand, leading to more cell death and decreased force of contraction.
Remodeled growth and increased stiffness.

Conclusion

Both systolic and diastolic heart failure result in decreased cardiac output and decreased ability to meet the body's demands.
Underlying processes and compensation mechanisms differ significantly.

Introduction

This lesson focuses on the differences between systolic and diastolic heart failure, two distinct conditions with different underlying mechanisms and clinical presentations.
Heart failure involves decreased cardiac function, leading to insufficient blood flow to meet the body's metabolic demands. This can result from impaired contraction (systolic dysfunction) or impaired relaxation and filling (diastolic dysfunction).
Underlying processes determining systolic vs. diastolic failure are not fully understood, but involve complex interactions between cellular, molecular, and hemodynamic factors. Further research is ongoing to elucidate these mechanisms.

Systolic Heart Failure

Problem with systole (contraction), characterized by the heart's inability to contract forcefully enough to eject an adequate amount of blood.
Inability of the heart to pump with enough force to meet the body's demands, resulting in reduced cardiac output and tissue perfusion.
Decreased force of contraction = decreased contractility = decreased inotropy, reflecting the weakened ability of the myocardial muscle fibers to generate force.
Decreased stroke volume leads to decreased cardiac output due to decreased force of contraction, triggering compensatory mechanisms to maintain blood pressure and organ perfusion.
Ejection Fraction (EF):
- Normal EF: 50-70%, indicating the percentage of blood ejected from the left ventricle with each contraction.
- Systolic heart failure: EF < 40%, a key diagnostic criterion indicating impaired contractile function.

Weakened heart muscle and enlarged ventricles, often resulting from damage to the heart muscle or chronic overwork.
Underlying disease leads to muscle cell death, decreasing contraction and ejection, and impairing the heart's ability to function efficiently.
Compensation mechanisms, such as increased preload, stretch ventricles, which, with less muscle cells, leads to enlarged ventricles. While initially helpful, these mechanisms can exacerbate heart failure over time.

Causes of Systolic Heart Failure

Decreased Blood Supply to the Heart:
- Most common cause, often due to coronary artery disease (CAD).
- Coronary artery disease impairs blood flow, leading to cardiac muscle cell death (ischemia and infarction), reducing the heart's contractile ability.
- Weakened heart leads to compensation, negative feedback, and progression, ultimately leading to worsening heart failure.

Heart Muscle Disease:
- Dilated cardiomyopathy, a condition characterized by the enlargement and weakening of the heart muscle.
- Can be genetic or due to compensatory mechanisms increasing preload, as well as factors like alcohol abuse, viral infections, and certain medications.
- Enlarged chambers with weak muscle, leading to impaired contraction and reduced ejection fraction.

Valve Disease:
- Regurgitation:
  - Incompetent valve (e.g., mitral or tricuspid), allowing blood to leak backward into the atria during ventricular contraction.
  - Blood flows backward during contraction, decreasing ejected blood, increasing the workload on the heart.

- Stenosis:
    - Incompetent aortic or pulmonic valves, restricting blood flow out of the heart.
    - Smaller pathway for blood ejection, forcing the heart to work harder to pump blood through the narrowed valve.
    - Heart works harder, leading to less ejected blood and eventual heart failure.

- Both lead to decreased cardiac output, resulting in symptoms like fatigue, shortness of breath, and edema.
- Body attempts to increase workload, leading to increased demand on cardiac muscle cells. This increased demand can cause:
- Cell death and weaker heart.

Arrhythmias:
- Too slow, too fast, or uncoordinated heart rhythms that disrupt the normal sequence of atrial and ventricular contractions.
- Dis-synchrony between ventricles or abnormal rate decreases cardiac output, reducing the heart's ability to pump blood effectively.
- Compensatory mechanisms don't work in heart failure, leading to further deterioration of cardiac function.

Systolic Heart Failure Cycle:

Underlying disease → muscle cell death → decreased pumping ability/force of contraction → decreased cardiac output → compensation → increased workload → increased demand → cell death → decreased force of contraction.
Less muscle cells available for contraction further reduces the heart's pumping capacity.

Diastolic Heart Failure

Problem with diastole (filling), characterized by the heart's inability to relax and fill properly between contractions.
Heart unable to pump enough blood to meet demands due to impaired filling, resulting in reduced preload and cardiac output.
Reduced preload, the volume of blood in the ventricles at the end of diastole, which affects the heart's ability to stretch and contract effectively.
Hypertrophy occurs, with thicker muscle walls reducing ventricle size, decreasing the space available for filling with blood.
Limited blood ejection, as the stiffened ventricles cannot expand fully to accommodate an adequate volume of blood.
Normal ejection fraction (EF) can occur, making diagnosis challenging as EF is typically used to assess systolic function.

Example:

Normal heart: 100 mL ejected from 200 mL volume = 50% EF.
Diastolic heart failure: 50 mL ejected from 100 mL volume = 50% EF.
Normal EF doesn't guarantee sufficient cardiac output, highlighting the importance of assessing diastolic function in patients with heart failure symptoms.

Myocardial Hypertrophy:

Muscle cells die, leading to remodeling of the heart's structure.
Remaining cells enlarge, and the body creates more cells, resulting in thickened ventricular walls and reduced chamber size.
Large muscle walls reduce space for filling, impairing diastolic function and reducing cardiac output.

Causes of Diastolic Heart Failure

Hypertension:
- Chronic hypertension constricts blood vessels, increasing the afterload on the heart.
- Heart works harder to pump against resistance, leading to compensatory hypertrophy of the left ventricle.
- Muscle growth leads to forceful contraction, but also reduces ventricular compliance and impairs diastolic filling.

Stenosis:
- Aortic stenosis reduces valve opening size, increasing the resistance to blood flow out of the heart.
- Heart works harder to eject blood through the narrowed valve, leading to left ventricular hypertrophy.
- Leads to muscle cell growth, reducing ventricular compliance and impairing diastolic filling.

Restrictive Cardiomyopathy:
- Dead muscle cells lead to fibrotic scar tissue, making the ventricles stiff and noncompliant.
- Decreased compliance reduces stretch and filling, impairing diastolic function and reducing cardiac output.

Hypertrophic Cardiomyopathy:
- Genetic myocardial hypertrophy, characterized by abnormal thickening of the heart muscle, particularly the left ventricle.
- Larger muscle walls reduce ventricle size and filling ability, impairing diastolic function and increasing the risk of sudden cardiac death.

Other Causes:
- Coronary artery disease, age-related changes in cardiac function, diabetes, and infiltrative diseases like amyloidosis can also contribute to diastolic heart failure.

Diastolic Heart Failure Cycle

Underlying disease leads to death of cardiac muscle cells, decreased force of contraction, decreased cardiac output, increasing workload through compensation, increased oxygen demand, leading to more cell death and decreased force of contraction.
Remodeled growth and increased stiffness, impairing diastolic filling and reducing cardiac output.

Conclusion

Both systolic and diastolic heart failure result in decreased cardiac output and decreased ability to meet the body's demands, leading to similar signs and symptoms.
Underlying processes and compensation mechanisms differ significantly, requiring different diagnostic and treatment approaches.