CHF Flashcards
What is heart failure?
- disorder in which heart pumps blood inadequately, leading to reduced blood flow, and back up of blood in the veins and the lungs
- as the blood backs up b/c of diminishing CO, pressure in heart chambers and vessels distal to failing pumping chamber increase - creating edema
- add kidneys will respond by retaining fluid and salt
- the body becomes congested
2 main forms of HF?
- systolic: heart contracts less forcefully and can’t pump out as much blood that is returned to it. As a result, more blood remains in the ventricles (still only 40% EF)
- diastolic: heart is stiff and doesn’t relax normally after contracting. Even though it may be able to pump a normal amt of blood out of the ventricles, the stiff heart doesn’t allow as much blood to enter its chambers from the veins. As in systolic dysfxn the blood returning to the heart then accumulates in the veins
- both forms of heart failure often occur together
Why is there a cough in CHF?
- fluid collecting in lungs, in alveoli because of increase in pressure, fluid leaks out into pleural space and causes pleural effusion - increased pressure on lungs and fluid build up cause cough
Common causes and risks of CHF in US?
- ischemic heart disease (62%)
- cigarette smoking (16%)
- HTN (10%)
- obesity (8%)
- diabetes (3%)
- valvular disease (older pts)
What are key risk factors for heart disease?
- high blood pressure
- high LDL cholesterol
- smoking
- other risk factors:
diabetes, overweight and obesity, poor diet, physical inactivity, and excessive alcohol use (decrease contractility of the heart)
What are more rare causes of HF?
- viral myocarditis: (infection of the heart muscle) - coxsackievirus B
- infiltrations of the muscle such as amyloidosis
- HIV cardiomyopathy
- CT diseases such as SLE
- abuse of drugs such as alcohol of cocaine
- pharm drugs such as chemo agents
- arrhythmias
- OSA (independent cause of HF)
What determines pump function of the heart?
- electrical system
- heart muscle excursion - EF
- priming the heart: preload
- resistance to ejection: after load (PVR)
What is cardiac arrest, what is it due to?
- cessation of normal circulation of blood due to failure of the heart to contract effectively. Medical personnel may refer to an unexpected cardiac arrest as a sudden cardiac arrest
- a cardiac arrest is different from (but may be caused by) a heart attack, where blood flow to the muscle of the heart is impaired
- arrested blood circulation prevents delivery of O2 to the body, lack of O2 to the brain causes LOC, which then results in abnorm or absent breathing. Brain injury is likely to happen if cardiac arrest goes untx for more than 5 minutes. Cardiac arrest is a medical emergency!!!
Patho phys of CHF?
reduced force of contraction due to overloading the ventricle. In a healthy heart, increased filling of the ventricle results in increased force of contraction (by Frank-starlying law of the heart) and thus a rise in cardiac output In HF this mechanism fails, as the ventricle is loaded with blood to the pt where heart muscle contraction becomes less efficient. This is due to reduced abilty to cross-link actin and myosin filaments in over stretched muscle.
What is a common cause of systolic dysfunction?
- CAD.
- it can impair large areas of the heart muscle because it can reduce blood flow to large areas of the heart
Most common cause of diastolic dysfunction?
- inadequately tx high blood pressure. High BP stresses the heat because the heart must pump blood more forcefully than normal to force blood into the arteries against the higher pressure. Eventually, the heart’s walls thicken, then stiffen. The stiff heart doesn’t fill quickly or adequately so that with each contraction, the heart pumps less blood than it normally does
What is worse, orthopnea or PND?
- orthopnea is presentation of severe CHF: can’t lay down because fluid fills up the lungs
- PND: earlier manifestation - wake up in middle of the night gasping for air
Why are crackles heard inCHF?
- from the alveoli popping open, from surface tension inside, and from congestion in lungs from back up of pressure.
How does the RAAS mechanism contribute to worsening CHF?
- decreased renal blood flow secondary to low CO triggers renin secretion by the kidneys
- aldosterone is released - this leads to increase of Na+ and then water retention
- preload increases
- worseing failure
2 diff mechanisms that cause systolic LSHF? and examples of each
- impaired contractility:
1. MI
2. transient MI
3. chronic vol overload: mitral or aortic regurg
4. dilated cardiomyopathy - volume overload (increased preload)
1. mitrial insufficiency
2. aortic insufficiency
3. atrial/or ventricular septal defect
2 diff mechanisms that cause diastolic LSHF? examples of each
- impaired ventricular relax:
1. LVH
2. hypertrophic cardiomyopathy
3. restrictive cardiomyopathy
4. transient MI - increased after load (pressure overload)
1. mitral stenosis
2. pericardial constriction or tamponade
3. aortic stenosis
4. uncontrolled HTN
When does CHF occur?
when the pumping efficiency of the heart is so low that blood circulation cannot meet tissue needs
- reflects weakening of myocardium by various conditions which damage it in different ways:
1. coronary atherosclerosis
2. persistent high BP
3. dilated cardiomyopathy
4. valvular heart disease
Mechanism of coronary atherosclerosis?
- clogging of coronary vessels with fatty buildup
- heart becomes increasingly hypoxic and begins to contract ineffectively
- myocardial ischemia occurs when myocardial availability to meet metabolic requirements just doesn’t happen (supply isn’t meeting demand)
- damage to endothelium occurs and this leads to decrease in nitric oxide and prostacyclin production (vasodilators), and increased enodthelin prod (vasoconstrictor) - this leads to vasoconstriction, vasospasm, and thrombosis
What occurs in MI that leads to impaired myocardial contraction and cell death?
- intracellular acidosis - this leads to increased Na/H exchanged which leads to increased intracellular Na and then decreased Na/Ca exchange - to intracellular Ca overload - this is what causes impaired myocardial contraction and cell death
Effects of MI?
- diastolic dysfxn: when a sufficient amt of myocardium is ischemic, then LVEDP rises (first indication of ischemia) so relaxation is impaired and myocardial compliance decreases
- systolic dysfxn: ischemia causes alterations that may range from minimal impairment to absence of movement (akinesis), may have compensation by surrounding areas of normal muscle