Heart Failure

Cardiac Output- the volume of blood ejected by the left ventricle per minute

Systole- ventricles contracting

Diastole- Ventricles relaxing

Ejection Fraction- amount of blood pumped out of the ventricle divided by the total amount of blood in the ventricle

SV x HR = CO

Cardiac Functions Concepts

Concept

Definition

Clinical Impact

Stroke Volume

Blood ejected per bet by left ventricle

Cardiac output; affected by preload, afterload, contractility

Preload

End-diastolic ventricular filling/stretch

Increased by fluid overload; influences SV via Frank-Starling law

Afterload

Resistance ventricle must overcome to eject blood

Elevated in hypertension; lowering afterload improves SV

Contractility

Intrinsic myocardial ability to contract

Enhance by sympathetic activity or inotropes; reduced in LV failure

Left Ventricular Ejection Fraction (LVEF)- Volume of blood pumped with each ventricular contraction

  • about 60% to 70% of blood volume in the left ventricle is pumped out with each contraction

    • A LVEF < 40% is indicative of heart failure

Heart Failure

Heart Failure- impaired function of the heart

  • classified by ejection fraction (EF)

  • heart muscle is weak and doesn’t pump effectively or fill with blood properly

Neurohormal activation in HF

  • activation of RAAS

    • BP increases initially

    • Fluid volume increases (NA and water retention)

  • Sympathetic nervous system activated

    • heart rate increases initially

    • Blood vessels constrict

  • Over time heart remodeling and fibrosis occurs

Labs for Heart Failure

  • B-type natriuretic peptide (BNP)

  • Potassium

    • check for hyperkalemia

  • Sodium

    • check for hyponatremia

  • Renal Function

    • BUN

    • Creatinine

  • Troponin (cardiac markers)

Treatment of Heart Failure

  • Low-fat diet

  • nonsmoking

  • low salt

  • physical activity

  • low alcohol use

  • weight loss (if obese)

  • medications

Systolic dysfunction versus Diastolic dysfunction

Systolic HF

  • Weakened ventricle has difficulty ejecting blood out of the chamber

  • ventricle is a poor forward pump causing inadequate ventricular emptying

  • blood accumulates in the weakened ventricle

Diastolic HF

  • Ventricle has difficulty relaxing, is less elastic, and cannot expand fully

  • stiff ventricle cannot fill with blood adequately

  • stroke volume and cardiac output are diminished

Right-sided, Left-sided, or Biventricular Heart Failure

Comparisons of Heart Failure

Feature

Left-sided HF

Right-Sided HF

Main causes

Hypertension, CAD/MI, valve disease, cardiomyopathy

Left-sided HF, chronic lung disease (cor pulmonale), pulmonic valve disease, RV MI

Main problem

Poor forward pumping to systemic circulation

Poor pumping to lungs

Where blood backs up

Lungs

Body/Systemic veins

Key symptoms

Dyspnea, crackles, orthopnea, PND

Edema, JVD, Hepatomegaly, ascites

Left- Sided Heart Failure

  • Causes

    • HTN

    • CAD/MI

    • Cardiomyopathy

    • Valvular Dysfunction

  • Manifestations (blood backs up to the lungs)

    • Crackles

    • Cough

    • Dyspnea

    • Paroxysmal nocturnal dyspnea

    • pulmonary edema

Right-Sided Heart Failure

  • Causes

    • left-sided heart failure

    • Chronic Lung disease (Cor Pulmonale)

    • Right Ventricular MI

    • Pulmonic Valve disease

  • Manifestations (Blood backs up into the systemic venous circulation)

    • peripheral edema

    • jugular venous distension (JVD)

    • Hepatomegaly

    • Ascites

Cor Pulmonale- Right Ventricular Failure caused by lung disease

  1. Chronic hypoxia develops due to lung disease

  2. Chronic hypoxia causes pulmonary arterial vasoconstriction (pulmonary hypertension)

  3. Pulmonary hypertension causes higher resistance against the right ventricle. The ventricle eventually weakens and RVF occurs