Chapter 12 Heart Failure

Chapter 12

Heart failure

Zhao Mingyao BMC.ZZU. 2006-3-22

the concept of heart failure heart pump failure myocardial failure chronic congestive heart failure

• Heart pump function

SV

CO HR

myocardial contractility myocardial relaxility preload (VR) afterload (ejection impedance) Prolonged overload metabolism structure change

Section 1 etiology and classification

1.underling causes (1) myocardium impaired ??? (2) myocardium overload over preload overafterload

2. Precipitating factors • O2 supply of myocardia • O2 consumption and myocardial work • • • • •

Infection Arrhythmia Pregnancy Disorder of water, electrolytes and acid-base Over fatigue

3.Classification • • • • •

Degree: symptomatic heart failure Progress velocity Cardiac output Site Function impaired

Section 2 pathogenesis

1. myocardial contractility↓ (1) Damaged cardiomyocyte (2) Metabolic disorder of energy production utilization

insufficiency of vitamin B1 lead to heart failure

Pyruvic acid

~ decarboxylase

ATP

acetyl Co A Krebs citric acid cycle

(3)Dysfunction of excitationcontraction coupling( Ca2+ delivery disorder ) 1)reduced Ca2+ intake, reserve and release of SR (Ry-R) 2) reduced influx of extracellular Ca2+ 3)dystunction of Ca2+ binding to troponin

Ca2+ waves and oscillations

2. diastolic dysfunction ↓ • (1) delayed reposition of Ca2+ • (2)blocked dissociation of the actin-myosin complex • (3)decresed ventricular diastolic potential • (4)Reduced ventricular compliance

Diastolic properties ↓

Diastolic process = Relaxility

compliance diastolic load

3. Asynergic myocardial contraction and relaxation

asymmetry and asynchronism

4. Endothelial dysfunction • • • •

Vascular contraction and dilation Vascular remodeling Adhesive properties Apoptotic process

Section 3 Compensatory responses

1.cardiac compensation • (1) heart rate • (2) Frank-Starling

mechanism • (3) myocardial hypertrophy

(1) increased in HF CO = SV X HR

(2)Frank-Starling law Contractile power Contractility

Frank-Starling Curve Total Blood Volume Atrial Contribution

Body Position

Intra-Thoracic Pressure

Stretch of Myocardium Venous Tone

Ventricular Performance

Pumping Action of Skeletal Muscle

End-Diastolic Volume

Pericardial Pressure, Compliance

(3)Myocardial hypertrophy concentric eccentric sarcomeres in parallel or in series

concentric

eccentric

2. Systemic compensation (1)blood volume (2) redistribution of blood flow (3)erythrocyte (4)ability of tissue to utilize O2

3. Neurohormonal compensation (1)sympathetic nervous system (2)RAAS (3)atrial natriuretic peptide (4)endothelin

two side effects of heart hypertrophy (myocardial remodeling ) fibril, mit, vol↑ but collagen(~ I, thick ,stiff; ~III ) ↑ phenotype change α- MHC ↓,β- MHC↑

MHC: Myosin heavy chain

myocyte hypertrophy and widening of interstitial spaces due to depostion of collagen, inflammatory cells and amyloid.

Section 4 effects on body myocardial contractility↓ diastolic properties↓

VR↓

CO ↓

?

heart pump↓

pulmonary congestion

systemic congestion

? ?

1.Congestion of pulmonary circulation (1) dyspnea • mechanism:

Types of dyspnea 1) exertional ~: 2) orthopnea 3) paroxysmal nocturnal ~

Orthopnea means shortness of breath while lying down.

Orthopnea means shortness of breath while lying down

(2)Pulmonary edema

2. congestion of systemic circulation (1)systemic venous congestion and hypertension (2)edema (3)hepatomegaly and hepatic dysfunction

3. Low cardiac output • • • • • •

Fatigue and limb weakness Mental confusion and disturbed behavior Cyanosis Nocturia Anasarca Cardiogenic shock

Section 5 Principle of prevention and treatment removal cause prevent predisposing factor improving cardiac function: inotropic agent digitalis Ca 2+ channel antagonist or Ca 2+ receptor blocker vasodilator agents stem cell and heart transplantation

• Brief history about treating heart failure: 1940 times heart + kidney mode 1970 times heart + circulation mode 1990 times heart + endocrine mode ACEI, β-receptor blocker ,α- receptor blocker