Week 6 - Cardiac Muscle Dysfunction And Failure Parts 1-3 Flashcards
What is heart failure?
The inability of the heart to pump adequate amounts of blood through the circulation
What is the function of normal cardiac pump?
Pump blood from veins to arteries
How is BP created?
By volume of blood in vessels and the heart pumps out
Systolic pressure
Peak pressure generated
Diastolic pressure
Lowest pressure just before the next contraction
Mean arterial pressure (MAP)
- Measure of BP over time
- MAP = 1/3 x SBP + 2/3 x DBP
Total peripheral resistance (TPR)
- Amount of force exerted against the circulating blood by the vasculature of the body
- Affected by blood volume and resistance to flow in blood vessels
- Less resistance, pump doesn’t have to work as hard to move the blood through the vessels
Pulse
- Rhythmic dilation of an artery that results form beating of the heart
- Norm: 72 bpm
Pulse pressure
- Difference between systolic and diastolic blood pressure
- Norm: 40 mm Hg
Afterload
Amount of pressure that the heart needs to exert to eject the blood during ventricular contraction
What does cardiac pumping increase?
Arterial pressure
TPR decreases at same time as pumping increases to prevent what?
Excessive pressure
What coordinates changes in TPR and cardiac pumping to regulate afterload?
Brain stem centers
Preload
- Volume of blood received by the heart
- Stretch, amount of volume being returned to the heart
- Increase in preload will increase amount of blood returning to heart, which increases pumping force of heart by stretching it out more
What does greater pumping effectiveness do to venous pressure?
Decreases it
More blood is pushed out
How does the sympathetic nervous system maintain venous pressure and preload on the heart?
By constricting veins when pumping increasaes
Controls venous constriction and dilation of veins to maintain venous pressure
Afterload
- Pressure or resistance the heart has to overcome to eject blood
- Squeeze, the amount of resistance the heart has to overcome in order to eject blood
What do the differences in arterial and venous pressure drive?
Stroke volume and cardiac output
- CO = SV x HR
What causes blood to circulate with each beat?
Small decreases in venous pressure and large increases in arterial pressure
Ejection Fraction
% of blood in ventricle ejected into arteries
- Efficiency of cardiac pump (normally 50 or 50-70%
- EF = (EDV - ESV)/EDV
- Measures severity of HF
Stroke volume
Amount in mL ejected from the heart
Cardiac output
Amount of blood ejected/circulated in one minute
End systolic volume
Blood left in the ventricle after contraction
End diastolic volume
Amount of blood in ventricle just before contraction
What is CHF
- Heart is failing to do its job: pumping blood from the veins to the arteries
- Cardiac output is not maintained
- Arterial pressure may not rise enough w/ each contraction or venous pressure may become too high
- EF typically low in HF - used to determine severity
At what percentage of ejection fraction do issues start occurring with HF?
41-49%
What percentage of ejection fraction causes significantly impaired function in HF?
< or equal to 40
How do the two pumps in the heart work in series?
They fill and empty each other
Pulmonary circulation has tremendous branching, low resistance and pressure, what does this result in?
Less work for right ventricle
Left pumps throughout the body
- Tremendous difference in resistance among vascular beds
- Much higher overall resistance than pulmonary
- Results in much more work for left ventricle
Function reflected in anatomy - left ventricle
- Basically a thick cone pumping against a high pressure
- Has a much greater oxygen consumption than the right due to more muscle and pumps harder
Function reflected in anatomy - right ventricle
Basically a thin flap pumping against a very low pressure
Which side of the heart is most likely to fail first?
- Left side unless there’s an injury to the R side
Compensated cardiac output
When cardiac output is balanced regardless of demand on the heart
Decompensated cardiac output
If cardiac output is not balance, or cannot keep up with demand
What happens if right and left-sided cardiac output are not identical over a small time frame?
One side will become backed-up (congested) and the other will have low pressure
- Pulmonary backed up and systemic low pressure
OR
- Systemic backed up and pulmonary low pressure
How does the autonomic nervous system adjust to allow us to exercise?
Greater CO per EDV
True or false: ANS adjustments may allow high level of activity with CHF
False
ANS adjustments may allow LOW level activity with CHF
What happens with further decline in contractility?
- Does not allow activity
- Leads to death
How is cardiac output maintained?
By compensations
What does lack of compensation (decompensation) lead to?
- Too much fluid in the central or pulmonary veins
- Too much blood volume in the heart chambers
- Insufficient cardiac output
Hypertension
- Increased arterial pressure leads to L ventricular hypertrophy
- Leads to overstretched contractile fibers and less effective pump
Medical management of hypertension
ACE inhibitors
Calcium channel blockers
Diuretics
Beta blockers
What is coronary artery disease (myocardial infarction/ischemia) related to?
Dysfunction of the left or right ventricle - or both - as a result of injury
What can cardiac muscle dysfunction cause?
Coordination issues
What can cardiac arrhythmias impair?
Rapid or slow arrhythmias can impair functioning of left and/or right ventricle
Muscle as a cause of poor cardiac performance
- Weakness due to myocarditis, MI or cardiomyopathy
- Partial wall damage from ischemia or infarct
Dyskinesia
Uncoordinated - after MI, if conduction is compromised and one ventricle moves later than the others
Decreased wall movement
Hypokinesia: decreased movement
Akinesia: localized are of no movement
Abnormal conduction
Decreases coordination of contraction
Abnormal automaticity
Pacemaker not regular
- Tachycardia or bradycardia
- Multiple areas of automaticity at once (fibrillation)
Stenosis
Can’t open enough so not enough blood can get out
Aortic stenosis
Tight aortic valve so not enough blood can get through - problem sending enough blood and oxygen to tissues of the body
Regurgitation
- Incompetent
- Doesn’t close properly, can’t close all the way - can cause back leak of blood
Mitral regurgitation
Mitral valve is floppy - blood is going to get backed up to the lungs
Heart valve abnormalities
- Blocked/stenotic valve or incompetent/regurgitant valves cause heart muscle to contract more forcefully
- Associated with myocardial dilation and hypertrophy
- Surgeries: valve replacement and valvuloplasty
What kinds of valve replacements can occur?
- Procine valve (open heart surgery)
- Metallic valve (open heart surgery)
- TAVR (minimally invasive)
Cardiomyopathy
Contraction and relaxation of myocardial muscle fibers are impaired
Primary cause of cardiomyopathy
Problems with conduction and infection
Secondary causes of cardiomyopathy
Diabetes, autoimmune disorders, alcohol, heavy metal or drug toxicity
- More common
Blockage/Compression of Vessels/Chambers
- Pulmonary (or other) embolus
- Valsalva collapsing vena cavae
- Accumulation of fluid in pericardium compressing R ventricle — cause heart failure
- Tumors blocking heart chambers or compressing vessels
Saddle pulmonary embolus
Result in total or near blockage of pulmonary arteries —> no pulmonary blood flow —> no filling of L ventricle —> no output of L ventricle —> rapid onset of dyspnea, LOC, death
Hemopericardium
- Pressure inside pericardium prevents filling of R ventricle (cardiac tamponade)
- Decrease in pulmonary blood flow can be life threatening
- L ventricle cannot be filled
- Same consequences as saddle embolus, develops more gradually
- Drain pericardium to relieve pressure (pericardiocentesis)
NYHA Class I
- Mild
- No limitation is experienced in any activites
- No symptoms from ordinary activities
NYHA Class II
- Slight, mild limitation of activity
- Patient is comfortable at rest or with mild exertion
NYHA Class III
- Marked limitation of any activity
- Patient only comfortable at rest
NYHA Class IV
- Most severe
- Any physical activity causes discomfort
- Symptoms present at rest
Common signs of CHF
- R sided elevated jugular venous pressure
- Hepatojugular reflex
- Third heart sound
- Bilateral pulmonary wheezes
- Retention of excessive body fluid
- Peripheral edema
- Weight gain
Common symptoms of CHF of the inability to compensate
Fatigue
Dyspnea on exertion
Decreased exercise tolerance
Common symptoms of CHF due to fluid backup in the pulmonary system
Paroxysmal nocturnal dyspnea
Orthopnea
Orthopnea
Inability to sleep unless partially upright
Quantified by number of pillows used to allow one to sleep
Cyanosis
Due to lack of perfusion to the tissues
Chronic heart failure
Long-term problem with many of the symptoms described
Signs and symptoms of chronic heart failure depend on what?
Left vs. right
Forward vs. backward
Systolic vs. diastolic
Acute heart failure
- Life threatening condition
- Results in Cardiogenic shock and death w/o intervention
- Catastrophic loss of one-way valve system or other structural integrity
- Perforation, blockage by foreign object or tumor, poisoning of cardiac muscle
- Serious arrhythmias: V-fib, V-tach
Left sided acute heart failure
Rupture of aorta, blow out of aortic valve
Right sided acute heart failure
Blockage by saddle embolus or hemopericardium
Right-sided heart failure
- Results of failing to empty vena cave
- Jugular distention
- Systemic congestion
- Dependent edema
- Sacral edema and ascites
- Nocturia as fluid is displaced from LEs to thorax while asleep
- Congestion of liver and spleen
- Impaired liver function and immunity: further edema and decreased blood clotting
Left sided HF
Results from failure of LV to empty pulmonary veins and fill systemic arteries
What does congestion of pulmonary veins and capillaries cause in left sided HF
- Dyspnea
- Orthopnea
- Paroxysmal nocturnal dyspnea
What does low cardiac output cause in left sided heart failure
Symptoms of decreased cerebral perfusion
Cool extremities may progress to rubor of dependency and to cyanosis
What is the most common cause of RHF?
LHF because it usually starts first
Interaction of RHF and LHF
Low systemic cardiac output causes fluid retention by kidneys - excess fluid increased preload on R side
Congestion of pulmonary circulation increased afterload on R ventricle
Forward heart failure
Problems primarily due to low cardiac output
Ischemic injury in tissues
Cool, cyanotic extremities and face
Backward heart failure
Problems primarily due to venous congestion
Increased venous pressure w/ leakage of fluid from capillaries
Pulmonary edema with LHF
Peripheral edema with RHF
1+ Pitting edema
Not obvious w/o checking
About 2 mm pit
Pit lasts a few seconds
2+ pitting edema
Obvious to trained person
About 4mm pit
Pit lasts several seconds
3+ pitting edema
Obvious to eye
About 6 mm put
Pit lasts a few minutes
4+ pitting edema
Grossly distorted limb
“Sausage fingers or toes”
About 8 mm pit
Pit lasts several minutes
Systolic failure
Insufficient myocardial muscle strength relative to conditions to pump the blood throughout the body
Signs and symptoms of heart failure more likely to be experienced
Diastolic failure
Insufficient filling/low SV
May not be noticeable except during heavier exertion
Ventricle(s) too stiff to allow sufficient filling
May lead to sudden onset of tachycardia, arrhythmias and flash pulmonary edema
Mean arterial pressure
Often used to monitor perfusion of organs
MAP = CO x TPR
Normal ranges from 65 to 110 mmHg
Common causes of decompensation
Superimposed illness like pneumonia
Myocardial infarction
Arrhythmia
Uncontrolled HTN
Failure to comply with treatment
Excessive fluid or salt intake
Anemia, thyrotoxicosis, other problems that increase myocardial work
