C20 Heart failure Drugs 3 Flashcards
List the Physiologic effects of Ca2+ influx:
- Depolarization of SAN | AVN cells
- Myocardial Contraction
- Constriction vasc smooth muscle
Definition:
Decrease magnitude of Ca2+ current (via L-type channels) and cause bradycardia, vasodilation, decrease contractility
Calcium-channel blockers (CCB’s)
Calcium-channel blockers (CCB’s):
- Vascular selectivity (vasodilate)
- Many drugs end in “-pine”
- Amlodipine (Norvasc) is most often used in dogs and cats for the treatment of systemic arterial hypertension
Dihydropyridines
Calcium-channel blockers (CCB’s):
- Major effects on Nodal tissues
- Diltiazem most often used
- decrease Heart Rate
- decrease AV-nodal conduction
- Mild negative inotropic effects
- Mild vasodilation
Non-Dihydropyridines
CCB’s: Indications
- Atrial Tachyarrhythmias
Beneficial mechanism:
- decrease AVN conduction -> decrease ventr response rate (Afib)
CCB’s: Indications
- Reentrant SVTs
Beneficial mechanism:
- Stop tachycardia due to AVN depression
CCB’s: Indications
- Systemic hypertension
Beneficial mechanism:
- Strong arterial vasodilation
CCB’s: Indications
- CHF (sometimes: amlodipine)
Beneficial mechanism:
- Afterload reduction - dogs
Definition:
Refers to a change in size, shape, structure & function of the heart after injury to the myocardium
Chamber Remodeling
- is progressive & leads to heart failure & cardiac death
- can be slowed down, halted, or reversed by medical treatments
Concept of Cardio-protection:
Protection of the myocardium from injury due to chronic over-stimulation of neurohormonal systems
This may lead to:
Reverse Chamber Remodeling
Drugs:
- ACE inhibitors
- Beta-blockers including Carvedilol
- Spironolactone
- Fish oils (maybe)
(Benefits only after long-term therapy)
(Mostly used in occult canine cardiomyopathy (DCM))
Clinical problem: Chronic Neurohormonal Activation
- RAAS*
- SNS*
- AVP*
- Cytokine cascade*
ACE-inhibitors block Angiotensin Converting Enzyme (ACE) thus reducing the formation of _____
Angiotensin II (ATII)
- The -pril’s (enalapril, benazepril, etc)
- RAAS inhibitors & mixed vasodilators
ACE inhibitors
- The -tan (telmisartan, losartan etc)
- Act at a lower level of RAAS signaling
- AT-I –> AT-II (prevented with ACE inhibitors)
- Cats (and other mammals) have alternative pathways for generation of AT-II (“ACE escape”)
- Selective AT 1receptor blocker
- Telmisartan: ACE-independent RAAS inhibitor and reno-protective agent
- Primarily used for cats with proteinuric kidney disease & systemic hypertension
- Anti-hypertensive effect similar to amlodipine
Angiotensin Receptor Blockers (ARBs)
What’s the clinical problem?
- Relevant to cats with heart disease
- Feline arterial thromboembolism (FATE)
- Indicators: Atrial enlargement & “smoke”
- Plavix (clopidogrel) used for prevention of FATE
- Platelet receptor ADP P2Y 12 -> Platelet paralysis
- +/- Aspirin
Prothrombotic State
