Special Populations Flashcards
At rest, how much does the myocardium consume of the oxygen that is delivered to it?
70%
When the oxygen demand in the heart is increased, can the heart meaningfully increase its extraction ratio?
NO
What must increase when the heart requires more O2?
Coronary blood flow and/or CaO2 must increase
What causes decreased oxygen delivery?
Decreased coronary flow:
- tachycardia
-decreased aortic pressure
-decreased vessel diameter
-increased LVEDP
Decreased CaO2:
-Hypoxemia
-Anemia
Decreased Oxygen extraction :
- left shift of Hgb curve (decreased P50
- decreased capillary distention
What increased oxygen demand?
-tachycardia
-HTN
-SNS stimulation
-Increased wall tension
-Increased LVEDV
-Increased afterload
-Increased contractility
What is the definition of heart failure?
Complex physiologic process that causes a clinical syndrome characterized by the hearts inability to fill or eject blood in a sufficient quantity to meet tissue requirements
What does the ventricle not do well in systolic heart failure?
Ventricle doesn’t empty well (problem with ejection)
What is the hallmark of systolic heart failure?
Decreased EF with and increased EDV
since the heart can’t squeeze well, a greater amount of blood remains in the ventricle after each contraction
What kind of hypertrophy does systolic heart failure create?
Eccentric
becomes more spherical shaped
chamber size increases in an attempt to preserve stroke volume
What is the degree of systolic dysfunction expressed as?
ejection fraction (EF)
How is EF calculated?
SV/EDV
what is a normal EF?
> 55%
What is considered a mild EF?
45-54%
What is considered moderate dysfunction in terms of EF?
30-44%
What is considered severe dysfunction in terms of EF?
<30%
What are the causes of systolic HF?
CAD/myocardial ischemia
Volume overload (d/t valve insufficiency
Dilated cardiomyopathy
What is the compensatory mechanism in systolic HF?
When SV is reduced, the body compensates by activating SNS to raise the resting HR in an effort to maintain CO
What should you do to the preload in systolic HF?
already high
avoid overload, give diuretics if too high
What should you do to the afterload in systolic HF?
decrease- to reduce myocardial workload
- coronary perfusion pressure must be maintained
-SNP works well if volume is adequate
What should you do to the contractility in systolic HF?
May be reduced, augment w inotropes as needed
- avoid agents that cause reduced contractility
What should you do to the HR in systolic HF?
Usually high d/t sympathetic activation
- if EF is low, higher HR is needed to preserve CO
Fast, full, forward
What is the problem in diastolic HF?
Filling problem
Slow, full, constricted
Whats the hallmark of diastolic HF?
HFpEF
Diastolic failure occurs when the heart is unable to relax and accept the incoming volume.
What kind of hypertrophy happens in diastolic HF?
Concentric hypertrophy
-chronic pressure overload causes the myocardium to thicken
What are the causes of diastolic HF?
demand ischemia from chronic pressure overload
-myocardial ischemia
-stenotic heart valves
-hypertrophic cardiomyopathy
-chronic HTN
-cor pulmonale
-obesity
What is a preserved EF considered?
> 40%
What should you do to preload in diastolic HF?
volume is required to stretch the non-compliant ventricle
- LVEDP does not correlate with LVEDV
What should you do to afterload in diastolic HF?
Usually already elevated
- if not, need to keep elevated to perfuse thick myocardium
-phenylephrine
What should you do to contractility in diastolic HF?
Usually normal
- caution w agents that depress function
What should you do to HR in diastolic HF?
Slow/normal to maximize diastolic time for coronary perfusion and decrease MVO2
-maintain SR, dependent on atrial kick
** The LV with concentric hypertrophy is prone to ischemia, Maintenace of a high MAP and slow normal HR is crucial. Hypotension should be treated promptly with phenylephrine!
What is the most common cause of right heart failure?
left heart failure
also caused by pulmonary HTN, and right-sided MI
the right heart is thinner, more compliant, and weaker than the left heart
What does right sided HR cause?
systemic congestion, hepatomegaly, peripheral edema
What are things that can increase PVR (which can impair RV function?)
hypoxemia
hypercarbia
acidosis
N2o
desflurane
What is the treatment for right ventricular failure?
Main goal is to improve contractility which reduces right heart afterload
inotropes and decreased PVR
Management of right sided HF can be more difficult than left sided HF because fewer options exist for unloading and supporting the right ventricle
What is ventricular remodeling?
Compensatory mechanism in response to abnormal pressure or volume loads
Failing heart changes size, shape, function in attempts to preserve C.O.
Remodeling can be reversed by Ace Inhibitors/ aldosterone inhibitors
what BP is considered Pre-HTN?
120-129 / < 80
What is stage 1 HTN?
130-139/ 80-90
What is stage 2 HTN?
> 140 / > 90
What is considered HTN crisis?
> 180 / > 120
What are the secondary causes of HTN?
Coarctation of the aorta
Renovascular disease
Cushing syndrome
Conn’s syndrome
Pheochromocytoma
Pregnancy-induced HTN
What are the complications of HTN?
Left ventricular hypertrophy
Ischemic heart disease
Congestive heart failure
Arterial aneurysm (aorta, cerebral)
Stroke
ESRD
A high afterload increases myocardial work and an elevated arterial driving pressure damages nearly every organ in the body