Heart Failure (HF)
Decreased pumping or filling ability of the heart
Results in:
- Decreased CO
- Fluid build-up in the lungs (LHF) and/or peripheries (RHF)
- Hypoperfusion
Pathophysiology of HF
RAAS over-activity:
- HF
- Decreased CO (decreased effective circulating volume)
- Excess secretion of renin, angiotensin II, and aldosterone
- Increased sodium and water reabsorption
- Increased plasma volume
- Increased preload and afterload
- Increased pulmonary (LHF) and peripheral edema (RHF)
SNS over-activity:
- HF
- Decreased CO (decreased effective circulating volume)
- Excess secretion of (1) catecholamines and (2) insulin
- Increased (1) HR, BP, muscle tone etc., and (2) sodium and water reabsorption
- Vasoconstriction
- Increased preload and afterload
- Further decreases CO
Causes of HF
CAD (most common cause), MI, HTN, smoking, obesity, DM, cardiomyopathy, heart valvular disease
Other causes: Congenital heart disease, dysrhythmias, endocarditis, anemia, lung disease, drugs/medications
Cardiac Output (CO)
The amount of blood the heart pumps through the circulatory system in a minute (SV x HR)
Factors:
- Preload: ventricular stretch prior to contraction
- Afterload: resistance to ejection of blood from the heart
- Cardiac contractility
- HR
Stroke Volume (SV)
Volume of blood ejected during systole
Factors:
- Preload
- Afterload
- Nervous system alterations
- Myocardial oxygen supply
Frank-Starling Law
Increased preload results in INCREASED (1) contractility, (2) force of contraction, and (3) SV (to a limit)
However, if preload continues to rise, muscle fibers become over-stretched and ultimately DECREASE contractility, force of contraction, and SV (and CO)
Laplace’s Law
Contractile force within a chamber is directly proportional to (1) the RADIUS of the chamber and (2) the THICKNESS of its wall
Ex.: Small, thick-wall chamber = Increased contraction force; compared to a thin-wall chamber
Neurohumoral mechanisms in response to HF
- Catecholamines: SNS attempts to compensate for decreased CO by increasing HR, BP, and PVR (blood flow from pulmonary artery to LA)
- Vasopressin (ADH): causes water reabsorption in renal tubules (increases plasma blood volume), which results in vasoconstriction; increases preload and afterload
- RAAS: decreased renal blood flow and BP promotes sodium and water reabsorption; increases preload and afterload
- Brain natriuretic peptides: increase to attempt to decrease preload (by promoting sodium and water EXCRETION); compensation is generally inadequate
- Cytokines: inflammatory; cause vasoconstriction
Right-sided HF (RHF)
Reduced output from the RV; inability of the heart to provide adequate blood flow into the pulmonary circulation at a normal central venous pressure
Common cause: LHF
Right = Rest-of-body (back flow)
S/S: JVD, peripheral edema, hepatosplenomegaly, ascites, GI venous congestion (anorexia, bloating, N/, constipation), continued fatigue and weakness
Left-sided HF (LHF)
Reduced output from the LV; inability of the heart to generate adequate CO to perfuse vital tissues
More common; LHF typically ends up involving both ventricles
Left = Lungs (back flow)
S/S: DOE and PND (paroxysmal nocturnal dyspnea), blood-tinged sputum, orthopnea, cough, cyanosis, rales/crackles, fatigue, S3 gallop, oliguria
Systolic LHF
Pathway:
- LV pumping is impaired
- Blood is backed up into the LA
- LA has reduced filling capacity to accept blood from pulmonary veins
- Back flow of blood into the pulmonary vascular bed
- Increased hydrostatic pressure in the pulmonary vascular bed
- Accumulation of fluid in interstitial and alveolar spaces (pulmonary congestion)
Diastolic LHF
HF characterized by:
- Impaired LV diastolic filling
- PRESERVED ejection fraction
Clinical manifestation: DOE, fatigue
Pulmonary edema
Capillary fluid moves into alveoli; decreased gas exchange
S/S: Lungs become stiffer, harder to inhale, crackles, frothy pink sputum, “wet cough”, hypoxemia
Diagnosing HF
H&P
Lab (CMP)
EKG (Visualized electrical activity)
CXR
Echocardiography
BNP
FACES
Fatigue
Activities impaired
Chest congestion
Edema or ankle swelling
SOB
