44 - Cardiac Failure Flashcards
Afterload
Resistance to flow
Effect of increasing sarcomere length 1) 2)
1) Increase number of cross bridges 2) Increase Ca2+ sensitivity of troponin This increases force of contraction
Starling’s law
Increased preload (end diastolic volume) leads to increased cardiac contraction which leads to increased stroke volume and cardiac output
Important things derived from Starling’s law 1) 2)
1) Cardiac output = venous return 2) Left heart output = right heart output
How can right ventricular end diastolic pressure be measured? 1) 2)
1) Catheter inserted through a vein across the tricuspid valve 2) Measure right atrial pressure, because at end of diastole, atrial pressure = ventricular pressure = JVP
How can left ventricular end diastolic pressure be measured? 1) 2)
1) Catheter inserted via artery across aortic valve. 2) Measure left atrial pressure because at the end of diastole atrial pressure = ventricular pressure = pulmonary artery wedge pressure
What is pulmonary artery wedge pressure? 1 2 3 4
1) A measure of pulmonary venous pressure. 2) Catheter inserted into pulmonary artery. 3) Balloon on catheter inflated, occludes pulmonary artery. 4) This means the pressure measured will be from pulmonary vein
Name of catheter used to measure pressures in heart
Swan-Ganz catheter
Preload
Left ventricular end diastolic pressure
Equivalents of LVEDP 1) 2) 3)
1) Left atrial pressure diastolic 2) Diastolic pulmonary venous pressure 3) Pulmonary venous pressure
Equivalents of RVEDP 1) 2)
1) JPV 2) right atrial end diastolic pressure
*Pressures across the capillary wall
Starling forces 1) 2) 3) 4)
1) Movement of fluids in or out of capillaries across capillary length 2) Tends to leak out at arterial end 3) Tends to enter at venous end 4) Excess fluid is removed by lymphatics
What increases fluid leaving capillaries?
Increased venous pressure. This results in oedema
Causes of oedema 1) 2) 3) 4)
1) Increased venous pressure (EG: heart failure) 2) Decreased osmotic pressure (renal, liver failure) 3) Blocked lymphatics (cancer) 4) Increased capillary permeability (infection)