Pathophysiology of Heart Failure Flashcards
Prevalence, Incidence and Mortality of Heart Failure in the US
- prev=~5,000,000
- incidence=550,000
- mortality=250,000
Approximate cost of heart failure in US
$37.5 billion
Reasons for increasing incidence and prevalence
- Aging population
- Increased survival of initial cardiac disease
- Therapies generally stabilize HF, but do not often cure it.
Heart failure syndrome (forward failure) definition
Heart failure is the inability of the hear to pump blood forward at a sufficient rate to meet the metabolic demands of the body.
Heart failure syndrome (backward failure) definition
the ability to pump blood at a a sufficient rate to meet metabolic demands only if the cardiac filling pressures are abnormally high
Major characteristics of heart failure
- Poor forward blood flow
- Low flow →↓CO
- Backward buildup of pressure
- Congestion→↑filling pressure
- Typically a response to low flow.
- Decrease in cardiac output and an increase in filling pressure are fundamental to the pathophysiology of heart disease
Characteristics of systolic dysfunction that leads to heart failure
- Systolic dysfunction: a problem with squeeze→↓contraction→↓inotropy.
- Hallmark: decreased ejection fraction and ventricular enlargement
- Decreased ejection fraction
- Heart failure with reduced ejection fraction=HFrEF
- Left ventricular systolic dysfunction=LVSD
- Ventricular enlargement
- Dilated cardiomyopathy= DCM
- Decreased ejection fraction
Primary causes of systolic dysfunction leading to heart failure (3)
- Direct destruction of heart muscle cells
- Overstressed heart muscle
- Volume overloaded heart muscle
Causes of direct destruction of heart muscle cells
- myocardial infarction
- viral myocarditis
- peripartum cardiomyopathy
- idiopathic dilated cardiomyopathy
- alcohol.
Casues of overstressed heart muscle
- tachycardia-mediated HF
- meth abuse
- catecholamine mediated.
Causes of volume overloaded heart muscle
- mitral regurgitation
- high cardiac output
Characteristics of diastolic dysfunction leading to heart failure
- problem with filling→↓lusitropy/decrease in relaxation.
- Hallmark: normal ejection fraction and ventricular wall thickening.
- Normal ejection fraction:
- HF with preserved ejection fraction=HFpEF
- Preserved systolic function=PSF
- Ventricular wall thickening:
- Left ventricular hypertrophy=LVH
- Hypertrophic cardiomyopathy=HCM
- Normal ejection fraction:
Primary causes of diastolic dysfunction leading to heart failure (3)
- High afterload/pressure afterload
- Myocardial thickening/fibrosis
- External compression
Causes of high afterload/pressure afterload
- hypertension
- aortic stenosis
- dialysis (inadequate volume removal)
Causes of myocardial thickening/fibrosis
- HCM
- primary restrictive cardiomyopathy
Causes of external compression
- pericardial fibrosis/constrictive pericarditis,
- pericardial effusion
Main types of compensatory responses to heart failure (3)
- heart failure –> decreased CO –> mechanisms that aim to increase CO/compensate for other effects
- neurohormonal activation
- frank-starling increases in preload
- ventricular remodeling: hypertrophy and dilation
Characteristics of neurohormonal compensatory response to heart failure
- ↓filling/↓SV→↓CO
- Juxtaglomerular apparatus in kidney senses lower flow→renin-angiotensin-aldosterone (RAAS) activation
- vasoconstriction –> ↑TPR –> helps maintain BP and perfusion of vital organs
- aldosterone –> ↑Sodium retention
- Carotid sinus/aortic baroreceptors sense lower pressure→autonomic nervous system (sympathetic)/adrenergic activation
- ↑HR
- vasoconstriction
- ↑sodium retention + vasoconstriction + ↑HR →↑volume→↑LV filling
Characteristics of Frank-Starling compesatory response to heart failure
- decreased output/ejection fraction → higher ESV in LV + filling during diastole → ↑LV filling
- ↑LV filling→ increased preload → ↑SV
- stroke volume is preserved by increasing the end diastolic filling/pressure.
Types of ventricular remodeling (compensatory response to heart failure) and long-term consequences
- Long term increases in cardiac workload and increased metabolic demands promote adverse myocardial remodelling.
- Ventricular hypertrophy
- Ventricular dilation
- Myocardial damage/apoptosis
- Myocardial fibrosis
- Overtime remodelling causes:
- Decreased contractile force
- Decreased dynamic function
- Increased diastolic stiffness
Major characteristics of right-sided heart failure
- Under normal circumstances, the pulmonary vasculature is a low pressure system
- Stresses to the RV can cause it to fail to adequately pump blood through the lungs:
- ↓ Circulating blood flow (forward RV HF)
- ↑ Venous pressures (backward RV HF)
Major causes of right-sided heart failure (4)
-
Left heart failure
- Backward HF from LV dysfunction stresses the right side by increasing pulmonary venous pressures.
- Lung disease/pulmonary HTN/RV pressure overload
- “cor pulmonale”→primary lung disease causes HF
- COPD, primary pulmonary hypertension, sleep apnea
- RV volume overload
- Shunt
- tricuspid regurgitation
- Damage to the RV myocardium
- Isolated RV infarct (rare)
- myocarditis
