CV Drugs- Dig and Inotropic Drugs Flashcards
digitalis- plant family from which many
cardiac glycosides are derived
digitalis- is an inotrope used for
patients with CHF and to slow ventricular response of patients with SVT (PAT, afib, aflutter)
digitalis- decreases the risk of
death due to heart failure, but increases the incidence of sudden death (arrhythmias)
in the treatment of SVT, dig can be given in combo with
a beta-antagonist at smaller doses of each and yet obtain more rapid control
contraindications for digitalis
- Wolff-Parkinson-White (30% develop vfib from increased conduction down the alternate path)
- hypertrophic cardiomyopathy (sub aortic stenosis) (increased obstruction with increased contractility)
- acute myocardial infarction (increase oxygen demand with increased contractility)
digitalis- has been shown to improve
morbidity without any benefit on mortality
digitalis- may act by
decreasing sympathetic activity
digitalis- may not be effective in patients who have
normal left ventricular systolic function
digitalis- the benefits of dig therapy are greatest in patients with
severe heart failure, an enlarged heart and a third heart sound gallop
digitalis- may be used in patients with
mild to moderate heart failure if they do not respond to an angiotensin converting enzyme inhibitor or a beta blocker
__ of dig can be effective
low dosage
__ and __ must be considered in deciding on an approatire dosage of dig
renal function and possible drug interaction
in general, dig therapy should be avoided in
the acute phase after myocardial infarction
digitalis- directs effects, inhibition of
Na/K ATPase ion transport system- causing increased Na inside the cell
digitalis- direct effects, increased intracellular Na then effects
the Na/Ca exchanger and less Ca is taken out of the cardiac cell; more Ca inside the cell accounts for increased contraction force
digitalis- decrease (less negative) __
resting membrane potential (automaticity)
digitalis- increase in the slopes of
phase 4 (automaticity)
digitalis- decrease in duration of
action potential due to shortening of phase 2 (corresponds to vent contraction)
digitalis- MOA on ANS activity
enhanced parasympathetic nervous activity; SA node activity decreased, slowed conduction through the AV node
digitalis CV effects-
- increased myocardial contractility
- increased CO
- improve tissue perfusion
- increased parasympathetic activity
digitalis CV effects- increased myocardial contractility from
increase SV, decreased heart size(preload), decreased LVEDP
digitalis CV effects- increased CO from
increased renal perfusion, diuresis of newly mobilized edema
digitalis CV effects- improved tissue perfusion
decreased sympathetic outflow, decreased SVR (afterload) leading to even better stroke volume
digitalis CV effects- increased parasympathetic activity
slowed HR- negative chronotropic and negative dromotropic (better coronary artery perfusion)
digitalis CV effects- in the normal heart, increased contractility is offset by decreases in __. __ may remain unchanged or even decrease
heart rate and direct vasoconstriction
CO
digitalis changes in EKG- ___ causes changes shown on EKG
cardiac glycosides
digitalis changes in EKG- prolonged PR
delay through the AV node
digitalis changes in EKG- shortened QT
more rapid ventricular repolarization
digitalis changes in EKG- ST segment depression
decreased slopes of phase 3
digitalis changes in EKG- smaller or inverted T wave
decrease slope and duration of phase 2 and 3
digoxin- onset
5-30 minutes
digoxin- admin route
IV
digoxin- clearance
35% excreted daily via kidneys
digoxin- elimination 1/2 life
31-33 hours
digoxin- prolonged with renal failure to up to
4.4 days
digoxin- __ to protein (skeletal muscle) decreased muscle mass in elderly
25% bound
digitalis toxicity- narrow therapeutic range
0.5-2.5 ng/ml