Heart failure and cardiomyopathies Flashcards
What is HF
Inability to adequately fill or empty the ventricle
Cause of HF
CAD Cardiomyopathy Valve problems HTN Diseased pericardium Pulmonary HTN (cor pulmonale)
What are two examples of high-output HF
Pregnancy and anemia
HF patho
Pressure overload Volume overload Ischemia/Infarct Myocardial inflammatory disease Restricted diastolic filling
HF adaptive responses
Frank-Starling relationship
SNS activation
Alterations in contractility, HR, afterload
Humorally mediated responses
Eventually these responses become maladaptive and myocardial remodeling takes place
Frank-Starling curve basics
Up/Left- Good, more stretch, more contractility (early, acute, compensated HF)
Down/Right- Bad, too much/too little stretch leads to decreased contractility (later, decompensated HF)
SNS activation does 4 basic things for HF
Arteriolar constriction: Maintains BP despite decrease in CO. Blood flow is redirected to coronary/cerebral circulation.
Venous constriction: Increases preload–> CO maintained according to FS relationship (more stretch–> greater contractility)
RAAS: Decrease in renal BF activates RAAS (Na+ H2O retention)–> increased volume–> increased CO
Increased HR: HRxSV=CO
Other adaptive responses
CO increased: Contraction velocity increased, afterload decreased, HR increased
B-type natriuretic peptide- feedback to protect against too much volume/pressure. Weak in humans, but levels can tell you about the state of HF.
Myocardial remodeling
Bad. Big, hypertrophied heart (pressure load) results from long term activation of compensatory mechanisms for HF.
Myocardial dilation, wall thinning (volume load)
Interstitial collagen deposition increased (inflammation)–> leads to fibrosis/scarring and stiffening of the heart
Clinical features of HF
Dyspnea, orthopnea, paroxysmal nocturnal dyspnea
Fatigue, weakness at rest
Tachycardia, A-fib, S3 gallop (indicates filling problem)
Oliguria, edema, JVD, lung rales, tachypnea
HF Dx
CXR
Elevated BNP
Echo
MRI
HF management
ACE/ARBs Aldosterone blockers Diuretics Digoxin Inotropes BB Vasodilators Bivent pacing Nesiritide Assist devices
**4 Things to remember about anesthetic management in HF **
- HR- Normal to high (very rate dependent)
- Preload- Normal to high
- Afterload- Low to normal
- Contractility- Increase it
Be very careful of high MAC anesthesia
Other management considerations in HF
Maintain medication regime (esp. BB) unless contraindicated (ACE inhibitors)
Treat hypotension judiciously- ephedrine, phenylephrine, vasopressin are all good
May need to decrease general anesthetic doses, balanced approach is advised
Positive pressure ventilation beneficial
Regional is ok
Avoid fluid overload, keep track of fluids
+/- A-line
Give a run down of HF
Decreased contractility–> ventricle stretches, dilates–> increased ventricle radius increases work–> increased work means increased O2 consumption–> Cardiac output falls–> SNS outflow to increase HR, SVR–> Stroke volume falls
