Pathophysiology of Heart Failure Flashcards
The pathology of HF is caused by
Structural changes
Functional changes
Released biological substances
Additional Factors
The structural changes in HF can be divided into
Changes affecting the myocytes
Changes affecting the Left ventricle chamber
Changes affecting the Coronary Arteries
Myocyte changes in HF
Abnormal excitation-contraction coupling B-adrenergic desensitization Hypertrophy Necrosis or Apoptosis Fibrosis
Left ventricular changes in HF
Dilation
Remodelling
Increased sphericity
Wall thinning and aneurysm formation
Coronary Artery Changes in HF
Obstruction
Inflammation
Functional Changes in HF
Mitral Regurgitation
Intermittent ischemia or hibernating myocardium
Induced atrial or ventricular arrhythmias
Altered ventricular interaction/reduced synchronicity
Bioactive substances released in HF
Renin-angiotension system mediators Vasodilators Cytokines Noradrenaline Vassopressin
Other factors affecting the pathology of HF
Age, sex and ethnicity
Alcohol, smoking and drugs
Co-morbid conditions
What is the vicious cycle of HF?
Decreased cardiac output leading to:
- sympathetic activation increasing peripheral resistance
- decreased renal perfusion causing fluid retention increasing preload
What are the two stages of remodelling following myocardial infarct?
Stage 1: Infarct causes myocytes death, wall thinning and matrix disruption
Stage 2: Stretching and thinning of non-infarcted myocardium, adaptive hypertrophy and eventual collagen deposition and fibrosis
Why does output drop during HF?
Pressure on the wall increases with size
Reductions in viable myocardium
Failure of starling mechanism and Bowditch effect
What is the Bowditch effect?
Increased force of contraction with increased frequency of stimulation
This does not apply in severe heart failure
Neurohormonal regulation of cardiac output
Sympathetic drive
RAAS
Starlings law
Naturetic peptides
