Systems Pathology: Heart failure Flashcards
Two main problems/failures in heart failure:
- Fluid congestion (backward failure)
- Inadequate blood flow to tissues (forward failure)
What happens in actute heart failure?
In acute failure events take place rapidly and consequence is forward (shock)
What happens in chronic heart failure?
In chronic failure compensatory mechanisms may be brought into play and backward failure dominates (congestion)
3 Compensatory Mechanisms in Heart Failure
- Ventricular chamber enlargment: increases amount of blood in ventricle, so ejeccts more, but at cost of fluid retention
- Muscle mass increases: can eject more, but requires more oxygen to larger muscle
- Sympathetic stimulation: increases heart rate, contractility, redistribution and retention of fluid
Ways of stimulation renin release from kidney
- Sympathetic stimulation(b-adrenoceptors)
- Renal artery hypotension
- Decreased somdium delivery to distal tubules
Functions of angiotensin II
- Constricts resistance vessels, thereby increasing systemic vascular resistance and arterial pressure
- Causes aldosterone release from adrenal cortex; acts on kidney to increase sodium and fluidd retention
- Stimulates ADH release, increases fluid retention
- Stimulates thirst
- NA release from sympathetic nerve endings, and inhibits its reuptake; Enhances sympathetic adrenergic function
- Stimulates hypertrophy of cardiac muscle and arterial smooth muscle
What happens in cardiac remodelling and what brings it on?
- Hypertrophy in response to increased demands
- Adrenergic stimuli, cytokines (TNFa), and Angiotensin II mediate effects
- Beneficial in increasing cardiac output but these stimulants also have adverse effects
Benefits and harm brought about by adrenergic stimuli in cardiac remodelling
+ve: Contractility, Hypertrophy
-ve: Myocyte apoptosis, Myocyte toxicity
Benefits and harm brought about by angiotensin II in cardiac remodelling
+ve: hypertrophy
-ve: Changes expression of contractile proteins
Benefits and harm brought about by Ctyokines(TNFa) in cardiac remodelling
+ve: hypertrophy
-ve: Remodelling of matrix, dilation
A dilating chamber is a failing chamber
Signs of LVF
- Raised end diastolic BP
- Raised left atrial pressure
- Raised pulmonary capillary pressure
- Increased diffusion barrier for gas exchange
- Increased pulmonary oedema
- Breatlessness
Causes of LVF
- Acute ventricular dysrhytmias (VF)
- Myocardial infarction and ichaemic heart disease
- Longstanding hypertension
- Valve disease (aortic and mitral)
- cardiomyopathies and drugs
- congenital heart disease
Insufficient pump power- problem with heart muscle
Obstruction of outward flow- valve, aorta, arteries, arterioles
Obstruction of inflow- pericardial effusion, constrictive pericarditis
Signs and symptosm of RVF
- Raised end diastolic pressure
- Raised right atrial and JVP
- Raised central venous pressure
- Liver distension (abdominal discomfort)
- Increased interstitial fluid formation (peripheral oedema)
Causes of RVF
- Most common cause is LVF
- Acute right ventricular failure - massive pulmonary thromboembolism
- Chronic right ventricular failure due to chronic lung disease and pulmonary hypertension (cor pulmonale)
