12/9/2014 Medical Physiology CC: Heart Failure Harold Smulyan Flashcards
What is the definition of heart failure?
Inability of the heart to meet the metabolic needs of the body at normal filling pressures
What is important to distinguish HF from?
Cardiac dysfunction with successful adaptation
HF happens when…
…adaptation fails and becomes part of the problem
What is the clinical diagnosis of HF?
- no single finding
* a complex of findings
What are the 2 different diagnosis of which HF becomes the final common pathway?
- Decreased circulatory supply to the body
2. Increased circulatory demand from the body
What are some of the conditions that can decrease circulatory supply to the body?
- coronary heart disease
- MI
- ischemic cardiomyopathy
- valvular heart disease
- cardiomyopathy
What are some of the conditions that can increase circulatory demand from the body?
- hypertension
- thyrotoxicosis
- anemia
- A-V fistula
Adaptive mechanisms
Compensations that maintain pump function in the presence of heart disease or increased demand
What are the 3 main adaptive mechanisms of HF?
- Frank – Starling
(short term) - Neuro-hormonal (intermediate)
a. Renal - Hypertrophy
(long term)
In a ventricular EDV vs. ventricular performance diagram (F-S mechanism):
- Normal curve shows improved ventricular performance when the end-diastolic volume is increased (increased pre-load or venous return)
- Normal curve moves upward and to the left with exercise or increased sympathetic stimulation.
- Abnormal curve (in green) moves down and to the right with impaired ventricular performance.
In a LV filling pressure (left atrial pressure in diastole) vs. LV stroke work diagram:
- groups above and to the left of normal show the effects of exercise and/or sympathetic stimulation
- groups down and to the right of normal show progressive reduction of the change in stroke work with increasing LV filling pressure
- with increasingly severe LV dysfunction the LV filling pressure reaches 25mmHg, where the oncotic pressure of the plasma is exceeded and fluid crosses the alveolar membrane and enters the pulmonary alveoli
The neurohumoral adaptive mechanism of HF is related to:
Sympathetic stimulation -increased plasma NE
- redistribution of CO
- maintains flow to the brain and heart at expense of skin, skeletal muscle, gut and kidneys
What are the adaptive mechanisms of HF in the renal system?
Stimuli:
- decrease GFR
- decrease RBF
- increase aldosterone
Response:
- increase sodium and water retention
- increase plasma volume
- increase venous return
- increase venous pressure
Beta 1 receptor density is ___ and Beta 2 receptor density is ___ by HF
reduced; not reduced
LV contractility (dp/dt) ___ with addition of intracoronary dobutamine in patients with HF
decreases
What is the common theme between the stuff listed below and HF?
PNE = Plasma norepinephrine PRA = Plasma renin activity AVP = Arginine vasopressin ANP = Atrial natriuretic peptide ENDO = Endothelin
They are all increased with HF
- If abnormality can be corrected, hypertrophy will ___
2. If abnormality is not corrected, myocardial dysfunction will ___
- regress
2. worsen and become permanent
Ejection Fraction equals
(EDV-ESV)/EDVx100
What are two responses to hemodynamic overload?
Pressure overload
Volume overload
How does hypertrophy maintain pump function (CO)?
By keeping wall stress near normal
Pressure overload ___ systolic wall stress
increases
Volume overload ___ diastolic wall stress
increases
Both pressure and volume overloads lead to ___
ventricular remodeling
In pressure overload, sarcomeres arranged in ___
parallel
In volume overload, sarcomeres arrange in ___
series
Pressure overload leads to ___
concentric hypertrophy
thicker LV
Volume overload leads to ___
eccentric hypertrophy
greater LV volume
h/R: ratio of wall thickness to chamber radius –> ___ in pressure
overload
greater
Adaptation disadvantage of F-S response
High LVEDP -pulmonary edema
Adaptation disadvantages of neuro-humoral response
- increased myocardial O2 consumption
- arrhythmias
- diminished response to sympathetic stimulation
- blunted baroreceptor function
- increased systemic vascular resistance
Adaptation disadvantages of renal response
- peripheral/organ edema
2. decreased renal function
Adaptation disadvantages of myocardial hypertrophy response
- decreased contractility
- necrosis and apoptosis
- decreased coronary reserve
- changes in matrix (diastole)
What are some of the main failure maladaptations?
- worsening LV function
- fluid retention (pulmonary edema)
- excessive increase in vascular resistance
- renal failure
Therapies range:
- addressing underlying cause
- medications such as diuretics, vasodilators and beta blockers
- LVAD
- transplantation
