Cardiovascular Flashcards
What is the formula for cardiac output?
HR X SV
What increases stroke volume?
Increased end diastolic ventricular volume or decreased end systolic ventricular volume
What affects EDVV and ESVV?
EDVV- preload, compliance, diastolic filling time
ESVV- after load and contractility
What is the difference between bulk flow and osmosis?
Movement of fluid from hydrostatic pressure is bulk flow where as movement from oncotic pressure is osmosis
What does high hydrostatic pressure cause relative to ECF?
Filtration- blood out the capillary into ECF
How can heart contractility be increased?
Sympathetic nervous system- fight or flight
What changes occur in the CV at birth?
First breath leads to large drop in resistance to flow in pulmonary circulation
Increased venous return to left atrium = increased left atrial pressure closing foramen ovale
What is a vector of an ECG?
A vector is measuring the size of individual waveforms, observing direction and comparing size of deflections to give information on the flow of depolarisation
What does a vector show?
The vector points towards the most positive charge indicating the direction the action potential is moving
How can an estimate of a vector be made?
Comparing leads 1,2 and 3 it can be estimated by comparing the size of the deflection
The larger the deflection the more parallel the line
What is the mean electrical axis?
All the vectors create a PQRST waveform which can be averaged to give mean electrical axis
What is the mean electrical axis useful for?
Useful for looking for signs of chamber enlargement, cardiac displacement or interruption of the conduction pathway
What diagram is needed to work out the mean electrical axis?
Bailey’s hexaxial Diagram
What are the three techniques for estimating the mean electrical axis?
1) look for biggest QRS complex (note if +/-), this lead is most parallel to MEA so will be within 30 degrees
2) Look for isoelectric lead (lead with biggest deviation above the baseline equal to deviation above the baseline), this lead will be perpendicular
3) Quadrant graphing method- uses I and AVF to divide circle into 4 quarters
Describe how to estimate the mean electrical axis with the quadrant graphic method
Use lead I and AVF to divide the circle into quarters
Look at the traces for these leads and see if they have a positive or negative QRS
Draw arrows on the hexaxial diagram indicating the quadrant of the MEA
Then compare QRS in these two leads biggest is closer to MEA
What is the normal readings of MEA in dogs and cats?
Dogs- +40 to +100
Cats- 0 t0 + 160
What is the term used to describe an MEA out of the normal ranges?
Axis deviation- can be left of right
What causes axis deviations to MEA?
Heart isn’t sitting in the normal position in relation to limb leads
Size of the chambers of the heart is abnormal
The conduction pathway is abnormal so the AP is travelling a different route