Cardiac Flashcards
What are the phases of cardiac pacemaker potential
Phase 0 - Spontaneous baseline drift, threshold achieved at -40mV. Slow L type Ca channels cause depolarisation.
Phase 3 - slow Ca channels close and K channels open causing repolarisation
Phase 4 - hyperpolarisation from K efflux. Then Na leak into cell causes a baseline drift
How does the nervous system affect the pacemaker cardiac potential
Sympathetic system causes an increased gradient of phase 4 to increase HR
Parasympathetic causes a decreased gradient - decreasing HR
Which nerves are involved in the sympathetic action on the heart
to the SAN right sympthaetics
to the AV node left sympathetics
Which nerves are involved in decreasing HR
to SAN - right vagus
AV node - left vagus
In which situations may indirect acting sympathomimetics not work
Heart transplant as the heart has lost para sympathetic innervation
resting heart rate will be 100bpm
Glyco and Atropine will have no effect
direct acting drugs - adrenaline and isoprenaline can be used
Define shock
a pathophysiological condition where there is insufficient perfusion to maintain normal function of vital organs
What types of shock are there
Hypovolaemic shock - loss of circulating volume and reduce in preload and afterload
Cardiogenic shock - caused by myocardial dysfunction and subsequent reduction in cardiac output and systolic function
Obstructive shock - physical obstruction to filling of the heart reduction in preload and CO
distributive shock - caused by significant reduction in SVR such that organ perfusion cannot be maintained
Cytotoxic shock - caused by the uncoupling of tissue oxygen delivery and mitochondrial oxygen uptake.
What is the dicrotic notch
Small dip in the arterial waveform where the aortic valve closes and successive back flow
What is the equation for SVR
SVR = MAP - CVP/ CO x80
What is the systolic and diastolic pressure in the aorta, left ventricle and right ventricle?
Aorta ~120/80mmhg
Left Ventricle~ 121/0mmhg
Right Ventricle~ 25/0mmhg
