C20 Heart failure Drugs 3 Flashcards
(28 cards)
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
Heart Failure - Stages
“at risk” no current evidence of disease
Stage A
Heart Failure - Stages
- Heart dz present
- B1 (normal heart size or mild increase)
- B2 (remodeling - more severe cardiomegaly)
Stage B
- Treat B2 dogs with MVD or Dobermans with DCM with Pimobdndan
Heart Failure - Stages
Current | past CHF
Stage C
Heart Failure - Stages
Refractory CHF (additional therapies or higher doses needed)
Stage D
Therapy of CHF: Hospital
- Furosimide
- Oxygen
- Nitroglycerine (topical)
- Sedation (butorphanol)
-
Pimobendan (dogs, rarely used in cats)
(FONST-PLUS) - In Severe MR
- May add IV. Na+ -Nitroprusside or hydralazine for aggressive afterload reduction to decrease MR - In cardiogenic shock
- Add IV. Dobutamine for increased inotropy - Large effusions: - centesis to drain
Therapy of CHF (dog): HOME
- Pimobendan
- ACE-inhibitor
- Spironolactone
- Furosemide
-
Exercise modulation
(Pets Are Special For Everyone)
Dietary Modifications & Nutraceuticals
What is a general recommendation for CHF?
Sodium restriction
Dietary Modifications & Nutraceuticals
- Antagonize cytokine cascade - EPA & DHA reduce cachexia & antiarrhythmic effects
Omega-3 Fatty acids
Dietary Modifications & Nutraceuticals
- Essential amino acid in cats (NOT dogs)
- Deficiency dogs eating special diets (vegan, grain-free)
Taurine
