CHF Flashcards
1 cause of left heart failure and right heart failure
L: MI
R: PE
What are the 3 determinants of stroke volume
- preload
- afterload
- myocardial contractility
CO=SV x HR
The amount of myocardial stretch at the end of diastole
Preload
*The more a normal ventricle is distended (filled with blood) during diastole, the greater the volume of blood ejected during the next systolic contraction
The resistance a heart must overcome to empty it’s content
afterload
ventricular wall stress increases in response to
- the arterial systolic pressure (i.e. hypertension)
2. Increased chamber size (e.g. dilated heart chamber)
___ serves an initial compensatory role in reducing wall stress
An increase in wall thickness
changes in the force generated by the myocardium for a given set of preload and afterload conditions
contractility
3 causes of heart failure
(decreased Cardiac Output)
- Impaired ventricular filling (Decrease in Preload)
- Increased Afterload
- Impaired Contractility
What happens to preload, afterload, and contractility as SV increases
- Increase in preload
- Decrease in afterload
- Increased contractility
What type of heart failure is more common
systolic (2/3)- Ventricles become enlarged, and pump out less than 40-50% of blood
Cause of diastolic dysfunction and systolic dysfunction
Diastolic: Decreased filling
Ventricles stiff/cannot relax
Normal left ventricular ejection fraction (> 50%)
-CO limited during exertion (cannot take in larger volume in ventricle)
Systolic: Cause: Impaired Contractility or excessive afterload
Ventricles thinned, stretched, enlarged
Decreased LVEF (<40-50%)
-decreased output
Causes of Left sided HF
- MI (#1 cause)
- Aortic stenosis
- uncontrolled HTN
- Mitral stenosis
- percaridal tamponade
- LVH
- dilated cardiomyopathy
(change this card)
__ Ventricle is thinner / highly compliant as it ejects against a low pulmonary vascular resistance.
Right
*Very susceptible with sudden increases in afterload (e.g. PE)
isolated right heart failure is care (called __)
cor pulmonale
Most common cause of right heart failure is
left heart failure
Presentation of left sided heart failure
- Dyspnea,
- Orthopnea,
- Paroxysmal Nocturnal Dyspnea,
- Nocturnal Cough
*Back up comes from lungs therefore lung sx
Presentation of right sided heart failure
- Peripheral Edema,
- RUQ Discomfort / hepatic enlargement
*Back up comes from body therefore sx in body
Describe the cycle of chronic HF
- increased BP/CO
- increased cardiac workload
- LV dysfunction
- Decreased CO/BP
- hemodynamic remodeling, neurohormonal activation
- increased HR, contractility, vasoconstriction, increased volume
* cycle continues
Compensatory mechanism of HF
- ALL in response to decreased BP (BP = CO x TPR)
- Neurohormonal mechanisms (increase TPR)
- Autocrine System of Myocytes (Natriuretic Peptides)
- Ventricular Hypertrophy and Remodeling
*These are targets for treatment!!
Neurohormonal mechanisms (increase TPR)
- Sympathetic Nervous System (Adrenergic mechanisms)
- RAA system
- Increased ADH
How does the sympathetic nervous system compensate in HF
- Decreased CO = Decreased Perfusion pressure to baroreceptors in the heart (low BP)
- Sympathetic and Adrenal Epi / Norepi outflow to the heart and peripheral circulation is increased
-Increased CO: Increased heart rate (B-adrenergic stim.)
contractility
-Increased TPR: Vasoconstriction 2/2 alpha receptors
*Excess norepinephrine “toxic” to myocyte
Excess ___ “toxic” to myocyte
norepinephrine