Cardiomyopathy and Shock
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What are examples of primary cardiomyopathies?
- genetic: HCM
- acquired: stress or peripartum CMP
- mixed: dilated or primary restrictive
What's the difference btw primary and secondary cardiomyopathy?
- Primary: r/t defects confined to heart muscle
- Secondary: cardiac abn as part of a multi-system disorder
What are examples of secondary cardiomyopathies?
infiltrative, storage, toxic, inflammatory, endomyocardial, endocrine, neuromuscular, autoimmune
Describe the anatomic appearance of dilated CMP
- -LV chamber enlarged
- -systolic dysfunction
Describe the anatomic appearance of hypertrophic CMP
- -LV wall thickened
- -diastolic dysfunction
Describe the anatomic appearance of rx CMP
- -stiffened myocardium due to fibrosis or infiltrative process
- -unlike hypertrophic, myocardium is NOT stiff due to build up of muscle fiber itself
- -diastolic dysfunction
- -idiopathic (most)
- -inflammatory (viral or due to CT dz or peripartum)
- -toxic (chronic ETOH)
Major effects of DCM
myocyte injury causing decreasing contractility, decreased SV, causing LV dilation, and eventual MR
hallmark is ventricular dilation and decreased contractile function
DCM causes decreased SV and CO, what s/sx might be seen on physical exam?
Pulmonary and systemic congestion due to increased ventricular filling pressures
DCM has similar symptoms of what dz?
- -treat HF
- -prevent and treat arrhythmias
- -prevention of TE events
- -cardiac transplant
In what pts with DCM is an AICD recommended?
chronic symptomatic DCM and moderately reduced systolic function (EF <=35%), regardless of whether or not arrhythmias were detected
Why are pts with DCM prone to arrhythmias?
The decreased CO and SV leads to ventricular enlargement, MR and TR develop, this causes increased P and V load on the atria, atrial dilation develops, leads to arrhythmias
Does DCM affect only the left side of the heart?
No, it affects all 4 chambers usually, so MR and TR develop and pulmonary and systemic congestion are also seen
Anesthesia implications for HF
- -follow systolic HF guidelines
- -regional anesthesia is a possibility if pt is not anti-coagulated
Genetics associated with HCM
AD with variable penetrance (not all individuals will show the same degree of disease even though the genetics appear the same)
Is HCM caused by chronic pressure overload?
NO! It's a genetic abn characterized by asymmetric or sometimes global LV hypertrophy
What other disease variations are associated with HCM?
HOCM (hypertrophic obstructive) and IHSS (idiopathic hypertrophic subaortic stenosis)
- -asymmetric hypertrophy of ventricular septum in most cases
- -myocyte fibers are disorderly which plays a role in the increased diastolic stiffness and also with the arrhythmias associated with HCM
Effects of HCM
- -marked LVH so decreased diastolic relaxation and impaired filling
- -obstruction to LV outflow in pts with asymmetric septal hypertrophy
How does the diastolic P-V curve look in HCM?
- -EDP is increased (curve is shifted upwards)
- -Similar to LVH
What s/sx might be seen in the pt with HCM WITHOUT obstruction? Why?
- -EDP is increased due to stiff ventricle so pressure is reflected back to LA then to pulmonary system
What % of pts with HCM have asymmetric septal hypertrophy ?
Of those, that % have LVOT and possible MR?
What happens in HCM with LVOT?
- -ejection of blood thru AV is more rapid during systole due to narrowed opening as the septum is enlarged
- -this fast flow decreases the P, so that pulls the anterior mitral valve leaflet over towards the LV (SAM= systolic ant. motion)
- -this causes transient and dynamic obstruction of LVOT
Why does MR occur with HCM with LVOT?
-MR also results as the 2 leaflets should be coming together, but aren't due to SAM
Who's law relates to HCM with LVOT?
Effects of LVOT with HCM
- -Decreased compliance and outflow obstruction cause an increase in LA pressure
- -A P gradient develops between the main body of the LV and the outflow tract distal to the obstruction
- -results in increased LV ESP which causes increased wall stress
- -this leads to increased myocardial O2 consumption
- -angina can result
What factors promote obstruction of the LVOT in HCM and should be avoided?
- -anything that decreases LV cavity size (decreased preload), as this brings the leaflet closer to the septum and causes obstruction
- -increased contractility
Avg age of presentation with HCM
3 reasons angina can occur with HCM in the absence of CAD
- 1) hypertrophy increases O2 demand
- 2) hypertrophy also narrows the small branches of the coronary arteries
- 3) with LVOT the high systolic P will further increase O2 demand due to increased wall stress
- -left sternal border
also possible holosystolic murmur of MR at apex
standard of HCM treatment
- -BB are the standard as they decrease HR and contractility so will decrease both angina and dyspnea and will decrease obstruction (LVOT)
- -despite this they have not been shown to decrease sudden cardiac death
Risk factors for sudden cardiac death due to HCM
- -h/o syncope
- -family h/o sudden death (certain high risk mutations)
- -extreme hypertrophy of LV wall
HCM drugs to avoid
diuretics and vasodilators as they both decrease preload
Incidence of sudden death with HCM in adults? Kids / adolescents?
- Adults 2-4 %
- Kids / YA 4-6 %
Anesthesia management of HCM
- -avoid decreased preload and afterload
- -avoid increased contractility
- -some degree of myocardial depression is good- so the volatiles are good in this case
Vent settings with HCM
- -small TV and increased RR to min effects of PPV
- -avoid PEEP (decreases preload)
HCM drug choice for hypotension
neo as it will increase SVR without increasing contractility
HCM HD goals
- preload- full
- afterload- increased
- contractility- prefer depression
- rate- normal, BB useful
- rhythm- SR
Patho and effects of rx CMP
- -abn rigid but not necessarily thickened ventricle due to fibrosis, scarring, or infiltration of the myocardium
- -issue with diastolic filling
- -normal or near normal systolic function
Most common cause rx CMP in non tropical countries
Examples of rx CMP
- -non infiltrative (scleroderma and idiopathic)
- -infiltrative (amyloid and sarcoid)
- -storage diseases (hemochromatosis)
What are the effects of increased diastolic pressure and decreased ventricular filling in rx CMP?
- -increased diastolic P causes venous congestion leading to JVD, hepatomegaly and ascites, edema, pulmonary congestion
- -primarily signs of RV failure
- -decreased ventricular filling leads to decreased CO which causes fatigue and weakness
- -poor prognosis
- -treat underlying cause if there is one
- -salt rx
- -cautious diuresis (if pt is congested)
- -maintain SR
RCM anesthesia implications
- -same as for pts with cardiac tamponade
- -life threatening hypotension can occur from anesthesia and PPV
- -avoid decreased contractility, HR, and SVR
- -avoid bucking and coughing as this causes decreased venous return
what is circulatory shock?
Insufficient blood flow to deliver both O2 and nutrients to tissues
circulatory shock with decreased CO
cardiogenic and hypovolemic
circulatory shock with normal CO
hypermetabolic and abn tissue perfusion
3 stages of circulatory shock based on severity
- 1) non-progressive/ compensated: normal compensatory mechanisms are effective in causing full recovery without intervention
- 2) progressive- compensatory mechanisms are no longer sufficient, without an intervention shock will get worse and progress to death
- 3) irreversible- shock is so progressed that all available treatment is not enough to sustain life
What circulatory compensatory mechanisms are involved with shock?
- -baroreflex and stretch receptors that result in SNS stimulation
- -CNS ischemic response is activated at 50 mmHg
- -reverse stress-relaxation
- -epi and norepi from AM
- -fluid shifts
With an intact SNS what % of blood volume can be lost before irreversible shock occurs?
What about without an intact SNS?
- Intact SNS- 30-40%
- No SNS- 10-15%
In shock, which declines 1st, CO or BP?
CO due to SNS causing arteriolar constriction
How does autoregulation affect the heart and brain?
- -SNS stim does not cause significant VC of heart or brain vessels
- -as long as BP is maintained at 60-70 mmHg, the flow thru heart and brain are maintained even tho flow could be decreased to 25-30% of normal in other tissues
What is the reverse stress-relaxation response?
Blood vessels constrict around a smaller blood volume, tank becomes smaller and hence fuller
What compensatory mechanisms respond in secs to mins in shock?
- -CNS ischemic
- -epi and norepi release from AM
What compensatory mechanisms respond in mins to hours in shock?
- -reverse stress relaxation
What compensatory mechanism responds in hours to days?
How does cardiac depression contribute to progressive hemorrhagic shock?
vicious cycle- low BP means decreased coronary blood flow, decreased O2 and nutrients to myocardium, so heart loses it's ability to pump which further decreases BP
What is the most important factor in the final lethal progression of shock?
Decreased pumping ability of the heart
How does vasomotor failure contribute to progressive hemorrhagic shock?
- -VMC in medulla becomes less active over time
- -intense SNS discharge in 1st 4-8 mins of circulatory arrest
- -after 10-15 mins it becomes depressed and there is no further SNS discharge
How does micro vessel blockage contribute to progressive hemorrhagic shock?
- -in low flow situations tissue metabolism continues and acids (LA and H) build up along with other waste products
- -this causes blood to coagulate and plug the micro circulation
- -"sludged blood"
How does increased tissue permeability contribute to progressive hemorrhagic shock?
- -fluid transudates into surrounding tissues so IV volume is further decreased
- -no ATP is produced so Na/K/ATPase pump doesn't work so electrolyte gradients are disturbed
How does toxin release contribute to progressive hemorrhagic shock?
-shock process causes release of toxic substances like serotonin, histamine, and tissue enzymes that contribute to shock progression
How does cardiac depression by endotoxin contribute to progressive hemorrhagic shock?
- -esp important in septic shock
- -endotoxin is release from GN bacteria in the intestines due to low blood flow
- -causes increased cellular metabolism even tho there's inadequate nutrition
- -this leads to cardiac depression
How does cellular deterioration contribute to progressive hemorrhagic shock?
- -liver especially affected as it has a normal high metabolic rate
- -in shock there's a lack of O2 and nutrients to support the liver's high metabolic rate and hence it can't perform its job of detoxification
- -hence toxins build up
- -enzymes contained in lysosome are released and destroy cell membrane
- -leads to impaired ability of the cell to metabolize glucose in the late stages of shock
How do tissue necrosis and shock contribute to progressive hemorrhagic shock?
- -different parts of a tissue may be more susceptible to necrosis than others
- -liver, heart, kidneys, and lungs will develop acidosis
- -decreased blood flow so CO2 can't be removed as efficiently
- -this further perpetuates shock and acidosis
- -characteristic of later stages of shock as in early stages the compensatory mechanisms of the SNS and BR will overcome this
Is hypovolemic shock always due to red cell loss?
No, can be due to plasma loss (from intestinal obstruction or burns) or from tissue trauma (third space losse or blood loss)
Why will sluggish blood flow develop with plasma loss?
The viscosity of the blood increases significantly
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