Lecture 14: HF, Sounds, Shock Flashcards
Define Cardiac failure
Failure of the heart to pump enough v=blood to satisfy the needs of the body
Compensation for acute HF
Number of circulatory reflexes are activated in order to increase activation of the symapthetic innervation to the heart and decrease parasympathicteic innervation
- strengthens muscle contraction
- increases tone of most vessels, esp. veins- increases Psf
3 responses from ANS d/t acute HF :
Baroreceptor reflex
Chemoreceptor reflex
CNS ischemic response
Strong sympathietic stimulation d/t all ventricular function diffuesly damages but still functional:
Also if part of musculature is damaged—
Increases tone of most blood vessel of circulation and therefore increases venous return
Raises Psf!!! To 12-14 mm Hg
This increases tendency for flow from the veins back into the heart
Acute effects following AMI:
Reduced CO
Damming of blood in the veins- increased venous pressures
Causes compensation by sympathetic NS
Chronic compensation for MI- heart failure
Result from partial heart recovery and renal fluid retention.
Max. Pumping ability o the partylt recovered heart is stil depressed to less than 1/2 norm.
Heavy exercise generally causes return of symptoms back to acute HF stage….
Increase in r atrial pressure can maintain the CO at a near norm level despite continues weakness of the heart
Pressure changes in HF:
Increase in R atrial pressure
Decrease in mean Aortic pressure
Fall in capillary pressure reduces :
Chances of peripheral edema
Pulmonary edema and L HF:
L side of heart fails w/o concomitant failure of R side
Blood continues to be pumped to lungs but not adequately out of the lungs
Pulmonary filling pressure rises b/c of shift of large volumes from systemic into pulmonary circulation
Pulmonary capillary pressure increases
If rising to pressure = colloid osmotic pressure of plasma -28mm Hg fluids begins to filter out of capillary into lung lung interstitial spaces and alveoli resulting in pulmonary edema
2 major problems w/ L HF:
Pulmonary vasucular congestion
Pulmonary edema
Pulmonary edema onset:
Can occur so rapidly that if can cause death by suffocation in 20-30min.
What drug may function on a chronically failing heart by increasing the [ca++] in muscle fibers, thereby increasing the strength of contraction
Digitalis
What conditions can lead to high output heart failure?
Arteriovenous fistula: overloads heart-excessive venous return. Curve moves upwards.
Beriberi: heart muscle weakens d/t thiamine deficiency. Shift venous curve to the right. Results in decreased blood flow to kidneys.
What is first sound of heart?
AV valves closing- onset of ventricular systole
What is second sound of heart?
Semilunar valves closing- end of systole.
Distinguish btw left to right and right to left congenital defects
L to R: Patent ductus arteriosus- blood flows backwards and fails to flow through systemic circulation.
R to L: Tetralogy of fallot- blood flows from R to L side of heart- bypassing lungs.
How is a patent ductus arteriosus L to R:
Blood flows backwards [L to R] from aortic arch to pulmonary arch
[essentially, L ventricle to R]
How is tetralogy of FA loot a R to L defect:
W/ a defect in the interventricular wall blood will flow out of the R venticle into the L ventricle
[R to L]
Define circulatory shock
Generalized Inadequate blood flow through the body, to the extent that the body tissues are damaged. Especially because of too little O2 and other nutrients delivered to the tissue cells
List 2 factors that reduce CO and give ex:
Diminished blood volume~20%.
Decreased vascular tone.
Obstruction of blood flow.
Ex: MI, Heart arrhythmia, toxic heart state, severe heart valve dysfunction, circulatory shock that results from diminished cardiac ability-cardiogenic shock.
Negative feedback mechanisms that attempts to return cardiac output and arterial pressure back to normal after cardiac shock?
Sympathetic reflex: initiated by arterial baroreceptors.
autoregulation for art. pressure as long as it doesnt drop elbow 70 mm Hg
What results from sympathetic stimulation reflex after arterial baroreceptor has initiated the reflex?
Results in: arterioles and venous constriction and increase in HR up to 180 bpm
Factors that cause a person to recover from shock:
- baroreceptor reflexes
- central nervous system ischemic response
- reverse stress-relaxation of the circulatory system
- Renin-angiotensin response
What effects does renin cause?
Constricts peripheral arteries and causes DECREASED outputs of water and salt by the kidneys.
