Systolic Heart Failure Lecture Notes

Overview

• Systolic heart failure occurs when the heart can't pump as effectively, failing to meet the body's demands.
• Related to systole, the phase of the cardiac cycle where the heart contracts and pumps blood.

Mechanism

• The heart's force of contraction, or inotropy, is reduced.
• Lowered ventricular inotropy means the heart can't eject as much blood, leading to reduced stroke volume.
• Weakened heart muscle is often due to the death of cardiac muscle cells or cardiomyocytes.

Causes of Weakened Heart Muscle

• Underlying diseases cause muscle weakening, leading to systolic heart failure.
• Cardiomyopathies (heart muscle diseases):
  • Often have unknown causes.
  • Generally weaken the heart muscle.
• Reduced blood supply to the heart:
  • Coronary artery disease is a major cause.
  • Plaque buildup narrows blood vessels, reducing oxygen supply and causing cell death.

Valve Diseases

• Regurgitation:
  • Valves between chambers allow blood backflow, reducing blood pumped to the body.
  • Causes the heart to work harder, demanding more oxygen, leading to more cell death.
• Stenosis:
  • Narrowed valve openings make it harder to pump blood.
  • Similar impact as regurgitation: more work, more oxygen needed, and more cell death.

Arrhythmias

• Abnormal heart rhythms (too slow, too fast, uncoordinated) reduce pumping efficiency.
• Increased workload on the heart leads to more cell death and weakened pumping ability.

Ejection Fraction

• A measure of pumping ability, expressed as the percentage of blood ejected with each beat.
• Normal range: 55-70%
• Abnormal range: 40-55%
• Heart failure evidence: <40%

Summary

• Systolic heart failure involves a cycle of reduced pumping ability, increased oxygen demand, and further muscle cell death.
• Maintaining ejection fraction is crucial for heart health and function.