Pathophysiology of cardiac failure Flashcards
Cardiac Output =
SV x HR
What determines preload?
venous return
What is afterload?
Force the contracting heart muscle must generate to eject blood from the heart
What are the main components of afterload?
- Vascular resistance
- Ventricular wall tension
What determines myocardial contractility?
Sympathetic nervous system
What does an increase in contractility generate?
increases CO independent of preload and afterload
Classify stage 1 heart failure
No limitation on physical activity
Classify stage 2 heart failure
Slight limitation on physical activity
Physical activity results in fatigue, palpitation, dyspnoea
Classify stage 3 heart failure
Marked limitation of physical activity
Classify stage 4 heart failure
Unable to carry on any physical activity without discomfort. Will experience symptoms of heart failure at rest
What is systolic ventricular dysfunction?
Impaired cardiac contractility therefore a decreased ejection fraction
What is diastolic ventricular dysfunction?
Normal ejection fraction but impaired diastolic ventricular relaxation and decreased filling. Heart is pumping less volume than normal
What are the 3 factors that cause systolic dysfunction when affected?
- Contractility
- Volume overload
- Pressure overload - valvular stenosis
What are the results of systolic dysfunction?
- Increased EDV
- ventricular dilation
- Increased ventricular wall tension (leads to long term remodelling)
What is more common; systolic or diastolic dysfunction?
systolic dysfunction
What are the causes of diastolic dysfunction?
- Impedance of ventricular expansion - constrictive pericarditis
- Increased wall thickness; hypertrophy
- Delayed diastolic relaxation; aging, ischaemia
- Increase HR; less opportunity for the heart to relax
What does cardiac tamponade cause in the pericardium?
reduces the space that the heart occupies
What conditions cause impaired diastolic filling?
- Left ventricular hypertrophy
- Restrictive cardiomyopathy
- Myocardial fibrosis
- Transient myocardial ischaemia
- Pericardial constriction or tamponade
What causes impaired contractility in systolic dysfunction?
- Coronary artery disease
- Myocardial Infarction
- Transient myocardial ischaemia
- Chronic volume overload
- Mitral regurgitation
- Aortia regurgitation
- Dilated cardiomyopathies
What causes increase afterload (chronic pressure overload) in systolic dysfunction?
- Advanced aortic stenosis
- Uncontrolled severe hypertension
What is LHS HF most likely to cause?
RHS heart failure
What occurs in RHS heart failure?
Congestion of peripheral tissues:
- Oedema and ascites
- Liver congestion; impaired liver function
- GI tract congestion; anorexia, GI distress, weight loss
What is an ascites?
swelling of abdominal region due to back up of fluid in the portal system
What occurs in LHS heart failure?
- Decreased cardiac output
- Activity intolerence and signs of decreased tissue perfusion; cyanosis and hypoxia
- Pulmonary congestion
- Othopnea
- Parxysmal nocturnal dyspnoea
- Cough with frothy sputum
What conditions mpede flow into the lungs in RV dysfunction?
- Pulmonary hypertension
- Valve damage/stenosis/incompetence
What conditions affect the pumping ability of the RV?
- Cardiomyopathy
- Infarction
What are the causes of Left ventricular dysfunction?
- Hypertension (increase TPR)
- Acute MI
- Aortic or mitral valve stenosis or regurgitation
- Increase in pulmonary pressure can lead to RV failure if you have LV failure
What are the main compensatory mechanisms that ultimately contribute to heart failure?
- Sympathetic nerve activity
- Renin-angiotensin-aldosterone
- Frank-Starling (length-tension) mechanism
- Fluid movements
What is the problem with the frank-starling mechanisms in systolic dysfunction
- Increased vascular volume –> increased EDV
- Increase in muscle stretch and O2 consumption
- Walls of the ventricles are stretch beyond the optimal length resulting in an decreased force of contraction
- Increasing HR has very little impact on SV
What are the problems with sympathetic activity in systolic dysfunction?
- Tachycardia, vasoconstriction, decreased perufsion, cardiac arrhythmias, renin release
- Increase the workload of the heart - causes ischaemia, damage to myoctes and decreased contractility
- Desensitisation of beta but not alpha receptors
**Numb to the effect of adrenaline
What are the problems with Renin-Angiotensin system in systolic dysfunction?
- Decrease in renal blood flow stimulate renin
- Renin –> Angiotensin II (constriction and remodelling)
- Angiotensin II = vasocontrictor and stimulates aldosterone release
- Sodium and water retention increase
What are the other functions of angiotensin and aldosterone and what are the results of this on the heart?
- Angiotensin II and aldosterone are involved in inflammatory responses leading to the deposition of fibroblasts and collagen in the ventricles
- Increase in stiffness and decrease contractility of the heart leading to remodelling and progressing dysfunction
Strategies for the treatment of heart failure
- Increase cardiac contractility
- Decrease proload or afterload
- By relaxing vascular smooth muscle
- Reducing blood volume
- Inhibit RAAS
- Prevent inappropriate increase in HR
