Pathophysiology of Heart Failure Flashcards
Describe the New York Heart Association Classification of Heart Failure
Class 1 - No limitation of physical activity
Class 2 - Slight limitation of physical activity but comfortable at rest
Class 3 - Marked limitation of physical activity
Class 4 - Unable to carry out any physical activity without discomfort and symptoms of HR at rest.
Describe the differences between systolic and diastolic dysfunction?
Classification is based on ejection fraction.
Systolic ventricular dysfunction (impaired cardiac contractility which leads to decreased ejection fraction). Diastolic ventricular dysfunction (normal ejection fraction but impaired diastolic ventricular relaxation so decrease filling.)
What are some of the causes for systolic dysfunction?
- Contractility (ischaemic heart disease or cardiomyopathy)
- volume overload
- Pressure overload (valvular stenosis or hypertension). This results in increased EDV, ventricular dilation and ventricular wall tension
What are some causes of diastolic dysfunction?
- Independent ventricular expansion (constrictive pericarditis)
- Increased wall thickness,
- Delayed diastolic relaxation (aging),
- Increased heart rate.
What type of dysfunction is more common?
Systolic dysfunction and left sided heart dysfunction. However long-term heart failure usually involves both sides of heart.
Describe what occurs as a result of right sided heart failure
You have congestion of peripheral tissues as blood pools in the veins of systemic circulation. This changes starlings forces and increases venous hydrostatic pressure. This promotes more fluid loss than the lymphatic system can take on board so you have more fluid in the tissues leading to oedema and ascites, and liver congestion which leads to impaired liver function. It also leads to GI tract congestion which can lead to issues absorbing nutrients so anorexia, GI distress and weight loss can occur.
What occurs as a result of left sides heart failure
Accumulation of blood in the lungs resulting in changes in starlings forces so more fluid loss from capillaries, so fluid accumulation in the lungs. This causes orthopnoea, cough with frothy sputum and paroxysmal nocturnal dyspnoea. Also causes decrease in cardiac output which can lead to activity intolerance and signs of decreased tissue perfusion such as cyanosis and hypoxia.
What are some of the causes of right ventricular dysfunction?
- Conditions impeding flow into lungs (PH, valve damage/stenosis/incompetence).
- Pumping ability of right ventricle (cardiomyopathy and infarction).
- Left ventricular failure (biggest cause)
- Congenital defects
What are some causes of left ventricular dysfunction?
- Hypertension
- Acute myocardial infarction
- Aortic or mitral valve stenosis/incompetence,
What are the issues with compensatory mechanisms?
While they try to maintain cardiac output, long term them contribute to worsening the condition. This is because the heart already cannot cope with the normal volume of blood.
What is the problem with the frank-starling compensatory mechanism?
An increase in vascular volume leads to increased EDV which increases muscle stretch and oxygen consumption. However this can lead to an overstretch in ventricular wall meaning the actin-myosin overlap is too far stretch it cannot generate force.
What is the problem with the sympathetic activity as a compensatory mechanism?
- It causes tachycardia, vasoconstriction, decreased perfusion of tissues, cardiac arrhythmias and renin release. This increases the workload of the heart. It can also lead to desensitisation of beta receptors, not alpha.
What are the problems with the renin-angiotensin compensatory mechanism?
Decrease in renal blood flow stimulates release of renin which increases formation of angiotensin 2. This causes vasoconstriction and stimulates aldosterone release. This therefore causes sodium and water reabsorption. Angiotensin 2 and aldosterone are also involved in inflammatory responses leading to depositions of fibroblasts and collagen in the ventricles. Increases the stiffness and decrease contractility - myocardial remodelling and progressive dysfunction.
What are some of the stratigies for treating heart failure?
Increase cardiac contraction. Decrease preload/afterload to decrease cardiac work demand, by relaxing vascular smooth muscle and reducing blood volume. Inhibit the RAAS and prevent inappropriate increase in HR.
