cardiovascular Flashcards
afterload
-resistance in the aorta/ pulmonary artery.
-increased afterload heart works harder to pump blood out.
preload
-pressure from venous system into R side heart by great veins.
-too much preload (excess blood in the heart ) decrease CO. heart cant stretch anymore leading to hypertrophy.
hypertrophic cardiomyopathy HCM
-most common form of heart failure in CATS
-excess afterload, increase ventricular pressure leads to venticular concentric hypertrophy
-increased systole
-smaller volume in chamber, muscle is thick
Dilated cardiomyopathy DCM
-most common form of heart failure in DOGs
-ecentric hypertrophy
-increased diastolic
-certain breeds predisposed (boxers, pinchers)
-cats develop if low taurine diet.
cardiac insufficiency/ failure
-due to reduced stroke volume/ cardiac output caused by: reduced preload, impaired contractility, increased afterload, inadequate valve function, abnormal rates.
heart failure symptoms
-cardiomegaly (enlargement)
-LV failure: not filling properly or not enough force to generate SV. blood accumulates in lungs, edema.
-RV failure: blood backs up into great veins, leads to brisket edema, ascites, hepatojugular refelx.
-FAILURE ON ONE SIDE LEADS TO FAILURE ON OTHER SIDE.
positive inotrophic agent
Pimobendan
-great for heart failure, extends life in dogs with DCM and mitral valve insifficiency.
-phosphodiesterase inhibitor which increases CAMP, Ca++
-positive inotrope (increase contractility) and arterial vasodilator (decreases afterload)
-increases well being and appetite.
positive inotrophic agent
digoxin
-digitalis glycosides isolated from foxglove
-inhibits Na/K atpase (sodium pump)
-increases contractility non selectively
-negative chronotrophic and dromotrophic effects decreases HR, increase CO.
-HIGHLY TOXIC
-increases peripheral tissue perfusion
digoxin mechanism of action
-acts on conductor cells to decrease chrono and domotrophy, HR, contractility.
-inhibits Na pump which resets ion gradient in cytoplasm.
-increases Na/Ca exchanegr and leads to ore Ca+ released Ca and contraction.
digoxin effects
-increased parasympathetic tone and decreased sympathetic tone (baroreceptor)
-ADE: death, anorexia, vomiting, diarrhea, AV block and arrythmias which can be made worse by hypokalemia.
-so using diaretics which decrease K can make even normal dose toxic.
-hyperkalemia blocks digoxin effects.
B blockers in heart failure
-end in LOL
-are useful in HCM and DCM due to inhibition of B1 stimulated renin release.
-B1 selective antagonists are prefered. ex metoprolol
vasodialators in Heart failure
-ends in pril
-ACE inhibitors
-enalapril, benzapril, imidipril
-prevent Ang II and Ang I formation by inhibiting angiotensin.
-ang I receptor antagonists (ARB’S) (valsartan or telmisaran)
effects of vasodialators ACE inhibitors and AT1 receptor blockers
-cause vasodilation-from no angII, reduce venous and arterial pressure and edema.
-prevent aldosterone release and decrease fluid retention and edema
-enalapril extends life 92% in HR
-Ace inhibitors prevent breakdown of bradykins which can lead to tickle cough
vasodialators best use of treatment/ misc
-acute treatment or in severe cases.
-ex. nitroglycerin, sodiul nitripusside break down into NO which can decrease pre and afterload.
-all vasodialators may cause hypotension, refelx tachycardia and activation of the RAAS system.
-best for short term decompensated animals
diuretics in heart failure therapy
-pulmonary edema is a huge problem as animal cant breath and is uncomfortable
-best treatment for pulmonary edema
-excessive use can lad to loss of venous return so you need to hydrate
-beware of hypokalemia making digoxin more toxic
digoxin
-use: heart failure, but mostly atrial fibrilation
-inhibits Na-L atpase and secondarily increases Ca+
-effects: positive ionotrope, negative chrono and domotrophe
dobuatamine
-used in acute treatmentof severe HF
-B1 agonist
-positive ionotrope
pimobendan
-best HF drug
-phosphodiasterase inhibitor (PDE3) in heart and BV
-positive inotrope, vasodilator
meteprolol
-used for hypertrophic cardiomyopathy
-slows HR and relaxes ventricales for better diastolic filling and increased CO
-B1 blocker.
Enalapril, Benazepril, Imidipril
-used for HR, hypertension
-inhibits angiotension converting enzyme
-reduced ang II –> vasodialtion and decreased aldosterone
valsatan, telmisatan
-AT1 receptor antagonists
-inhibiting actions of ang II
-causes vasodilation and reduces aldosterone release
nitroglycerine, nitroprusside
-used for HF
-exogenous sources of nitric oxide
-venodilation and reduced prelaod
prazosin and hydralazine
-used for HF and hypertension
-A1 ardenergic receptor agonsits
-arteriole dialaton and reduced afterload
sildenafil
-used for pulmonary hypertension
-phosphodiesterase inhibitor prevent cGMP breakdown.
-vasodilation in the lung and penile circulation and pulmonary pressure
supraventricular tachycardia
-any change which decreases the time required for depolarization from the maximal diastolic potential and threshold potential. which causes increased automaticity.
premature venticular contractions ventricular tachycardia
-afterdepolarzations from abnormal Ca+ influx into cardiac cells or after phase 3 of ventricular AP.