Post on 20-Jan-2016
Heart failure
Results from any structural or functional cardiac disorder that impairs the ability of the ventricle to fill with or eject blood to meet the body,s needs at rest or during exercise.
Low out put failure
Factors affecting cardiac output
Intrinsic factors which regulate myocardial contractility .
Extrinsic factors including contractile state of arterioles & veins.
Pathophysiology of cardiac performance in heart failure
- Intrinsic changes .- Extrinsic changes.
Intrinsic changes:Myocardial hypertrophy to maintain cardiac
performance in the face of adverse effects as decrease in myocardial contractility.
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Extrinsic changes:Decrease in cardiac outputrenal blood
flow renin release , angiotensin 11 in after load, preload ,sympathetic
dischargecardiac output Remodeling: Proliferation of connective tissue
cells, abnormal myocardial cells.
Clinical manifestations of heart failure
Tachycardia, decreased exercise tolerance with rapid muscular fatigue, dyspnea ( pulmonary congestion) peripheral edema, cardiomegaly.
Classification of Low out put Failure
Left Heart Failure :Most common due to L.V.S . Dysfunction
Right Heart Failure : In Pulmonary hypertension
Classification of Heart Failure
According to NYHA
Class 1: No limitations on ordinary activities and symptoms occur only with greater than ordinary exercise.
Class11: Slight limitation of ordinary activities , that result in fatigue & palpitation
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Class 111: No symptoms at rest, fatigue occur with less than ordinary physical activity
Class 1V : Is associated with symptoms even at rest
High output failure
Even though there is an increase in cardiac output; still not enough to meet all the body needs as in hyperthyroidism, anemia.
Drugs used in treatment of heart failure
Drugs with positive inotropic effect as : Cardiac glycosidesPhosphodiesterase inhibitors β- adrenoceptor agonist
Drugs without positive inotropic effect
Diuretics
Aldosterone antagonist
ACEI & Angiotensin receptor blockers
Vasodilators
β- adrenoceptor blockers
Vasodilators
The chose of vasodilators according to signs and symptoms and hemodynamic changes : Selective venodilators as nitrate group is used
when the main symptoms is dyspnea due to pulmonary congestion.
Selective arteriodilators as hydralazine is used when the main complain is rapid fatigue due to low cardiac output.
Non-selective vasodilators as ACEI
Clinical uses of vasodilators
1. Acute heart failure 2. Chronic heart failure
Long-term use of hydralazine & isosorbide dinitrate can reduce remodeling of heart
ACEI & Angiotensin11 receptor blockers
afterload
preload
sympathetic activity
remodelingmortality rate
β-adrenoceptor blockers
Antagonism the enhancing action of sympathetic overactivity .Reduce mortality ( reduce the remodeling changes through inhibition the mitogenic activity of catecholamines.Inhibit renin releaseSome of them have antioxident activityE.g. carvedilol & metoprolol
Diuretics
Reduce salt and water retentionventricular preload .Reduction of edema and its symptomsReduction of cardiac size improve cardiac performanceSpironolactone has two benefits:potassium sparing effect & inhibit the action of aldosterone .
β-agonist
Dopamine :acts on α ,β1 and dopamine receptors.
Dobutamine :selective β1- agonist.
Both of them are given intravenously & used in acute cardiac emergencies.
Dopamine is effective in patients with impaired renal function.
Adverse effects
TachycardiaAngina Tachyphylaxis
Phosphodiesterase inhibitors
Bipyridines : (Amrinone ,Milrinone )
They are given only intravenously.
Half-life 3-6hrs.
10-40% excreted in urine.
Mechanism of action
Inhibit phosphodiesterase enzyme (isozyme 3) in both cardiac & smooth muscles resulting an ↑ in cAMP leading to:
- Positive inotropism .
- Dilation in both resistance & capacitance vessels (reduction in after load & preload.)
Therapeutic uses
Used only for acute heart failure
( Short term use )
Adverse effects
Nausea ,vomiting
Arrhythmias (less than digitalis )
Thrombocytopenia
Liver toxicity
Milrinone less hepatotoxic and less bone marrow depression than amrinone.
Digitalis (cardiac glycosides )
Origin
Chemistry
Preparations
Structure o of cardiac glycoside
Pharmacokinetics
Oral availabilityOuabain Digoxin Digitoxin 0 75 > 90 Half- life 21 40 168 Plasma protein binding 0 20-40 > 90Percentage metabolized 0 < 40 > 80
Pharmacodynamics
At the molecular level cardiac glycosides inhibit Na+ / K+ ATP ase (sodium pump ).
Cardiac effects :
A) Mechanical
B) Electrical
Mechanism of action Mechanism of action
(A) MECHANICAL EFFECT(A) MECHANICAL EFFECT
Increase in myocardial contractility
(B) ELECTRICAL EFFECTS(B) ELECTRICAL EFFECTS
At Therapeutic DosesAt Therapeutic Doses
A) Slow conduction through S.A.N. & A.V.N.
prolong conduction time between atrium and ventricles ( prolong P-R interval in ECG.) .
B) Short duration of action potential & refractory periods
of both atrium & ventricles (Short in QT interval ).
At Toxic DosesAt Toxic Doses
in automaticity of ectopic focus All forms of arrhythmias can be detected : -
- Second-degree of A-V block.
- In Purkinje conducting system leading bigeminy rhythm.
Extra cardiac effectsExtra cardiac effects
GIT :Anorexia, nausea,vomiting, diarrhea.
C.N.S. :Disorientation,hallucination,visual disturbances, agitation, convulsions.
Gynecomastia
Kidney : Diuretic effect
I. Improve renal function .
II. Inhibit Na+ reabsorption from P.C.T.
Adverse effects
Heart
All forms of cardiac arrhythmias
GIT
C.N.S.
Skin : rash
Gynecomastia
Contraindications
Toxic myocarditis
Constrictive pericarditis
Cardioversion
Digitalis are effective in H.F. due to hypertension, atherosclerosis or ischemic heart diseases.
Factors increase digitalis toxicity
Small Lean body massRenal diseaseHypothyroidismHypokalemia Hypomagnesemia Hypercalemia
Treatment of digitalis toxicity
Stop drug
Potassium therapy
Cholestyramine
Atropine
Lidocaine
Fab antibodies in life-threating or severe cases.
Clinical uses
Heart failure ( LVSD)
2-Atrial flutter or fibrillation
Drug interactions
Diuretics hypokalemia (arrhythmia)Quinidine : plasma level of digitalis through (1) displaces from protein binding sites (2) renal clearance.Antibiotics that alter intestinal flora digoxin bioavailability Agents that release catecholamines sensitize myocardium to digitalis to induce arrhythmias.
Management of chronic heart failure
Reduce work load of the heart
Limit activity
Reduce weight
Control hypertension
Restrict sodium
Diuretics
ACEI or receptor blockers
Cont.
Digitalis
β- blockers ( class II-IV stable HF)
Vasodilators
Management of acute heart failure
Volume replacement
Diuretics
Positive inotropic drugs
Vasodilators