Heart Failure

Question 0

what are the compensatory mechanisms?

Answer 0

*increased sympathetic activity- increased catacholamine release (epinephrine, norepinephrine, & dopamine). This increases heart rate & force of contraction (Good). But this also increases heart workload, stress, & oxygen demand (BAD).

Question 1

what are some causes of heart failure?

Answer 1

• coronary heart disease (angina, plaques, hardened arteries = ischemia)
• Myocardial infarction (cause ischemic damage to the heart)
• Uncontrolled hypertension (over-exertion of the heart to pump against high blood pressure)
• Renal failure (over-exertion of the heart to pump against increased blood volume)
• Arrhythmias (including bradycardia & tachycardia)
• Age > 65 years

Question 2

what are the compensatory mechanisms of heart failure?

Answer 2

• Decreased cardiac output means decreased blood flow to the kidney. This is interpreted as dehydration and the kidney attempts to compensate with fluid retention. –Kidney releases renin which will cause fluid & Na+ retention & vasoconstriction.
• -This fluid overload & increased BP further strains the heart & leads to edema & pulmonary congestion.

Question 3

what is the compensatory mechanism of heart failure?

Answer 3

• myocardial hypertrophy (enlargement of the heart)
• -heart stretches, dilates, & increases in size to create stronger contractions (good).
• -But, if the muscle fibers are stretched too far, which they eventually will, contractions are weakened (Bad).

Question 4

what drug class does digoxin belong?

Answer 4

Cardiac Glycosides

Question 5

what is the mechanism of action of Digoxin?

Answer 5

• inhibits the Na+/K+ pumps of the cardiac cell membranes. This increases intracellular Na+ levels.
• High intracellular Na+ levels facilitates Ca++ influx into cells.
• Increased intracellular Ca++ equals stronger muscle contractions.

Question 6

what are the signs and symptoms of digoxin toxicity?

Answer 6

• nausea & vomiting, loss of appetite
• Fatigue, confusion, mental disturbances, dizziness, blurred vision, haloes on dark objects, yellow or green tinted vision
• Pulse less than 60 b/m
• Any type of cardiac arrhythmia (AV heart block, asystole, artrial tachycardia with block, AV dissociation, accelerated junctional rhythm, ventricular tachycardia, ventricular fibrillation, PR prolongation, ST segment depression)

Question 7

Digoxin toxicity is common. Why?

Answer 7

• Narrow therapeutic window
• Patient variable pharmacokinetics
• Multiple drug interactions
• Elderly are at increased risk due to decreased renal function, increased myocardial sensitivity, & frequent use of diuretics, laxatives, & other interacting medications.

Question 8

When is it appropriate to obtain digoxin serum levels?

Answer 8

Serum levels should be obtained only for the following reasons:
*Questionable compliance, lack of improvement, lack of ventricular control in A-fib, changing renal function, interacting medications, abnormal ECG, or other suspected toxicity.