2 Heart Failure

Question 1

Heart failure

Answer 1

Common syndrome may caused by any structural or functional cardiac disorder that impairs the ability of the ventricle to fill or eject blood

Question 2

HF clinical significance

Answer 2

Heart insufficient pumping causes:

Blood and fluid to backup in lungs
Buildup of fluid in feet, ankles and legs (edema)
Tiredness/shortness of breath
Common end stage of many forms of chronic heart disease
Progressive condition

Question 3

Precipitates of HF

Answer 3

1. Uncontrolled HT - increase BP - too much pressure on heart - pump fails
2. Myocardial ischemia -muscle not getting good perfusion - cannot function as pump
3. Sever emotional/physical stress

Question 4

Types of HF

Answer 4

Systolic - contractile function abnormality (HFrEF)

Diastolic - relaxation abnormal due to stiffness/filling (HFpEF)

Question 5

HFpEF

Answer 5

Abnormal diastolic function with LV hypertrophy

Preserved ejection fraction - Refers to signs and symptoms of clinical HF in a patient with a normal LVEF and LV diastolic dysfunction

LVEF greater then or equal to 50%

Relaxation is compromised due to stiffness of ventricles/fibrosis - less blood fills the heart so when EF is calculated the proportion is still the same

EF= SV/EDV

Question 6

HFrEF

Answer 6

Reduced EF (restricted) systolic dysfunction

Progressive chamber dilation

LVEF less than or equal to 40%

Decrease SV and decrease CO

Question 7

Pressure-volume relationships in systolic dysfunction in HF

Answer 7

Systolic- decrease in myocardial contractility, decrease SV, decrease CO

Compensations:
Increase SNS
Renal/salt water retention = increase EDV and increase pressure (activated in low BP)
Left ventricle hypertrophy = decrease wall stress, decrease afterload, increase contractility

Question 8

Pressure-volume relationships in diastolic dysfunction in HF

Answer 8

Relaxation - stiff ventricles

LVEDV and SV preserved

Abnormal increase in left ventricular diastolic pressure - decrease in L ventricular dispensability

Question 9

Clinical consequences of an increased LV diastolic pressure

Answer 9

LV diastolic pressure depends on: ventricular blood volume and stretch of ventricular muscle

During diastolic:

When the mitral valve is open - LV, LA and pulmonary vein form a “common chamber” continuous with the pulmonary capillary bed = back flow into lungs and increase pressure on L ventricle

Increase in LV diastolic pressure - increases pulmonary vein/capillary pressure - causing dyspnea, exercise limitation and pulmonary congestion!!

Question 10

Compensatory mechanisms

Answer 10

Signs and symptoms of HF caused in part by compensatory mechanisms

Frank-starling mechanism: increase EDV increase CO

Activation of nuerohumoral systems:
SNS = increase HR, myocardial contractility and vascular resistance - too much contractility heart fails as pump
Activation of renin-Angiotensin-aldosterone system = systemic and renal vasoconstriction - response to low BP and vasoconstriction to increase BP
ADH = increases systemic vascular resistance, potent vasoconstrictor = HT = organ/heart failure

Myocardial adaptation: cardiac hypertrophy is compensatory response of myocardium to an increase in mechanical work

Question 11

Consequences of compensatory hypertrophy

Answer 11

Increase protein synthesis and oxygen demand

As a result of ischemia and chronic workload increase other pathologic changes occur:
Cardiomyocyte loss by apoptosis
Accumulation of excess ECM - fibrosis (HFpEF)
Hypertrophied heart is vulnerable to ischemia related injury = cardiac failure