Pathophysiology of Heart Failure Flashcards
What is afterload?
The force the contracting heart must generate to eject blood from the heart
What are the patients symptoms in Class I HF as defined by th New York Heart Association?
No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea
What is ascites?
An abnormal buildup of fluid in the abdomen
What can right sided heart failure cause?
- Conjestion of peripheral tissues
- Oedema and ascites
- GI tract conjestion
anorexia, GI distress, weight loss - Liver conjestion
Impaired liver function
What can left sided heart failure cause?
- Decreased CO
- Activity intolerence, signs of decreased tissue perfusion
- Cyanosis and signs of hypoxia
- Pulmonary conjestion
- Cough with frothy sputum
- Orthopnea
- Paroxysmal nocturnal dyspnea
- Right heart failure
What is class II HF as defined by the NYHA?
Slight limitation of physical activity. Comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnoea
What is class III HF as defined by the NYHA?
Marked limitation of physical activity. Comfortable at rest. Less than ordinary activity causes fatigue, palpitations, or dyspnea
What is class IV HF as defined by the NYHA?
Unable to carry on any physical activity without discomfort. Symptoms of HF at rest. If any physical activity is undertaken, discomfort increases.
What is preload?
Determined by venous return; EDV.
What are the main components of afterload?
Vascular resistance; ventricular wall tension
What is the normal ventricular ejection fraction?
~50-60%
What is systolic ventricular dysfunction?
Impaired cardiac contractility therefore decreased ejection fraction (<40%)
What is diastolic ventricular dysfunction?
- Normal ejection fraction but impaired diastolic ventricular relaxation and decreased filling
- Therefore decrease in SV and CO
Systolic dysfunction commonly results from conditions that affect what?
- Contractility
- Volume overload
- Pressure overload
Diastolic dysfunction commonly results from what?
- Impedance of ventricular expansion
- Increased wall thickness
- Delayed diastolic relaxation
- Increased HR
What does systolic dysfunction result in?
- Increased EDV (preload)
- Ventricular dilation
- Increased ventricular wall tension
What is more common diastolic or systolic dysfunction?
Systolic dysfunction
What are the causes of right ventricular dysfunction?
- Conditions impeding flow into the lungs
- Pumping ability of right ventricle
- Left ventricular failure
- Congenital heart defects
What are the causes of left ventricular dysfunction?
- Hypertension (increased TPR)
- Acute MI
- Aortic or mitral valve stenosis or regurgitation
- Increase in pulmonary pressure can lead to right ventricular failure
Are the body’s intrinsic mechansisms good for dealing with HF?
- In they early stages they are good as the compensatory mechanisms maintain cardiac output.
- Longer-term, they contribute to the worsening of the condition
What receptors are desensitised by sympathetic activity?
Beta but not alpha receptors
How does increased sympathetic activity affect the heart long term?
- Tachycardia, vasoconstriction, decreased perfusion of tissues, cardiac arrhythmias, renin release
- Increased workload of the heart which leads to ischaemia and damage to myocytes which decreases contractility
- Dessensitisation of B1 receptors
What are the strategies for treating HF?
- Increasing cardiac contractility
- Decreasing preload and/or afterload to decrease cardiac work demand
By relaxing smooth muscle
By reducing blood volume - Inhibit the RAAS
- Prevent inappropriate increase in HR
What are the problems with the RAAS in treating HF?
- Decreased renal blood flow stimulates release of renin
- Renin release therefore increases angiotensin II formation (vasoconstrictor, plus stimulates aldosterone release)
- Sodium and water reabsorption is increased both directly (decreased flow rate through the kidney) and indirectly (via aldosterone)
