Week 9- Failing heart 1 Flashcards
What are the three functions of the cardiovascular system?
- Delivery of substances
- Removal of substances
- Distribution (heat, hormones, cells, bioactive agents)
What are the two fundamental mechanical functions of the heart?
- Eject enough blood into the aorta in order to meet perfusion requirements
2.To receive blood from the systemic and pulmonary veins in order to provide adequate drainage of capillary beds
What is preload?
The volume of blood returning to the ventricle (ventricular enddiastolic volume)
* Affected by venous blood pressure and the rate of venous return, which are affected by venous tone and
volume of circulating blood.
What is afterload?
The tension, force or stress acting on ventricular wall myocytes
after onset of shortening.
* Affected by arterial and arteriolar vascular smooth muscle constriction or dilation
What is heart rate?
: Determined by the rate of spontaneous sinoatrial nodal discharge
* Under autonomic control
What is the frank starling law?
» Greater amount of blood in the ventricles
results in greater contractile strength of the
ventricles and therefore increase in stroke
volume.
» Due to the more cross-bridges cycling, and a
greater availability of Ca++ to initiate this
cycling.
What is the definition of heart failure?
Heart failure – pathophysiological state when it is unable to function to meet the animals requirements.
what is myocardial failure
Impaired contractility – primary (dilated cardiomyopathy) or secondary (related to causes below leading
to myocardial failure)
what are the two common causes of volume overload
- valvular insufficiency
- shunts
What are the main causes of valvular insufficiency?
- Most common cause of volume overload
- Incompetence of atrio-ventricular valves (endocardiosis, endocarditis, congenital) – allow for regurgitation to
occur - Can be primary (myxomatous valve degeneration) or secondary (ventricular hypertrophy, ischemia, obstruction)
What are the main causes of shunts?
- Septal defects
- Overloading a particular heart chamber
What does excessive afterload cause?
- Short increases in afterload helps with contractility but chronic increases will depress myocardial
contractility. - Overtime – reduced rate of ejection if afterload is always high, leads to also reduced volume of ejection.
- Pulmonary or systemic hypertension, obstruction of ventricular outflow tracts, stenosis cause increase
afterload
What does inadequate preload and diastolic dysfunction cause?
- Reduction in preload represent inability to adequately fill the heart and diastolic dysfunction represent the
inability to relax (expand the chambers) – somewhat interrelated. - Inadequate preload – pericarditis, pericardial effusion.
- Diastolic dysfunction – myocardial fibrosis, restrictive cardiomyopathy, failure of adequate ventricular
relaxation. - Increases in ventricular end diastolic pressure which exerts stress on the heart and lead to remodelling.
When would a cardiac cough most typically occur?
Typically occurs when there is pulmonary oedema and the fluid accumulates in the airway
* occurs with tachypnoea and dyspnoea
* acute onset, soft, moist, blood tinged sputum
How might an enlarged atrium cause coughing?
mechanical compression of the trachea