CHAPTER 13 CHF Flashcards
What is Heart Failure?
What is the most common cause of Heart Failure?
Heart failure means the demands are not meeting the demands of the tissues.
Most common cause: Coronary Artery Disease
What are the types of Heart Failure?
Systolic Failure - reduce cardiac function, heart not pumping adequately
Diastolic Failure - reduced cardiac filling, usually do the the heart walls being too thick.
What is Congestive Heart Failure?
Increased left ventricle pressure at the end of diastole that results in increase pulmonary pressure (pulmonary edema). Blood backs up into the lungs
What are the 4 factors of cardiac performance?
Preload
Afterload
Contractility
Heart Rate
What contributes to Stroke Volume?
Preload
Afterload
Contractility
What is preload?
Preload is the end diastolic pressure that stretches out the ventricles.
The EDV is an indirect way to measure preload.
What is the formula for EDV/preload?
ESV (volume left after contraction) + passive filling + atrial contraction = EDV
What happens when we have an altered preload greater than 20-25 mm Hg in the Left Ventricle?
Normal Preload of LV is between (4-12 mmHg)
Back flow to the lungs result in pulmonary congestion.
Increase HF
Increase Blood Volume
Increase Venous Tone
What are ways to decrease preload?
Salt restriction
Diuretics
Venodilation (Nitroglycerin)
What is afterload?
What happens to afterload as CO decreases?
Deals with arterial resistance which heart must pump blood against.
Afterload increases as CO decreases.
Describe vicious spiral of progression of HF.
- Early stages of HF will decrease CO
- Decrease in CO will activate SNS response
- Increase NE, ANGII, ET
- Increase BP, Increase Afterload
- Decrease CO, go back to #2.
What is the first compensatory mechanism to respond to decrease CO?
Increase in HR maintain adequate CO to brain, heart, and kidneys
_________in preload and contractility will increase Stroke Volume.
Increase
Increase in afterload will ____________ cardiac output.
Decrease
What contributes to remodeling of the heart that leads to heart failure?
Chronic increases in preload
Chronic increase in afterload
Describe the Pathway of Normal Cardiac Contractility.
- Wave of depolarization will cause Ca2+ to enter the myocyte through L-type Channels.
- The small amount of Ca2+ that enters the cell is called “trigger Ca2+”, will bind to the Ryanodine Receptors (RyR) causing them to open.
- Calsequestrin holding the Ca2+ in the SR is released and goes through the RyR.
- Ca2+ bathes the actin and myosins, causing the contraction to occur.
- For relaxation of the myocytes, the Sarcoplasmic Endoplasmic Reticulum Calcium ATPase (SERCA) pump will pump Ca2+ back into the SR so that this cycle can be repeated during the next depolarization. This process requires ATP.
- Trigger Ca2+ goes back out into the interstitium using a NCX. Which will get rid of one Ca2+ for 3 Na+ into the cell.
- The 3 Na+ difference will need to be pumped out using the Na/K/ATPase Pump. 3 Na+ out, 2 K+ in.
List types of drugs that can be given to CHF patients to increase contractility?
- Calcium (CaCl, CalGlugonate)- if abnormal blood levels
- Cardiac Glycosides (Dig)
- PDE-3 Inhibitors (Milrinone)
- Catecholamines
What remains the ONLY oral (+) inotropic agent for HF?
Digoxin
How does Digoxin work?
- Competes with K+ on the sodium potassium ATPase pump, and inhibits it.
- Na+ builds up and reverses the NCX exchanger.
- More Ca2+ is pumped in, increasing contractility.
What are the toxicity of Digoxin?
VERY narrow TI (2)
Affects all excitable tissues
CNS: Disorientation, Hallucination, Visual, Agitation, Convulsion
May not be effective or more arrhythmogenic in patients with:
Hyperkalemia
Hypercalcemia
Hypomagnesia
Electrical Effects of Digoxin?
What can toxic doses lead to?
Increase PR interval (overall decrease in rate, make sure HR>60 bpm before digoxin administration)
Decrease QT Interval (downward swoop)
Tachycardia, fibrillation, Arrest
What are the main action of PDE3 inhibitors?
How does PDE3 inhibitors work?
Drugs?
Vasodilation, decreases afterload by decreasing BP.
Vasodilation will also decrease preload w/ less blood returning to the heart.
PDE3 prevents the breakdown of cGMP in the smooth muscle, increasing relaxation.
But PDE3 inhibitors also have a positive inotropic effect
by preventing breakdown of cAMP in the cardiac muscle, increasing contraction.
Drug Class Bipyridines: Milrinone
How do Beta Adrenergic Stimulants work with CHF patients?
Drugs?
Beta1 selective drugs are positive inotropes and chronotropes.
Less arrthymogenic than digitalis.
Beta1 selective drugs: Dopamine and Dobutamine
Dobutamine is most widely used
Increased CO and decrease ventricular filling pressure
What are the four stages of Heart Failure?
Stage A- High Risk/ No Sx
Stage B- Structural Heart Dz/ No Sx
Stage C- Structural Heart Dz/ Prev or Current Sx
Stage D- Refractory Sx that require special interventions
