Coronary + Cardiac Pathophysiology Flashcards
What is gallop rhythm a sign of?
Heart failure
What is the tilt test?
70 degree head tilt + continuous monitoring of HR + BP
+ve tilt test = vasovagal syncope
How is BP regulated?
Sensors = baroreceptors (monitor high pressure in aorta + carotid) + volume receptors (monitor low pressure in atria + ventricles)
Central control system = hypothalamus + medulla
Effectors = ANS to heart + BV’s
What is the effect of gravity on venous pressure?
Baroreceptor reflex acts to increase sympathetic output but few seconds delay so blood supply to brain reduced briefly
What happens in vasovagal syncope?
Venous pooling > reduced intracardiac vol > arterial hypotension sensed by baroreceptors > afferent nerve stimulated > autonomic drive to increase cardiac rate + LV contractility
BUT
C fibre activation in pressure receptors underfilled > LV triggers overriding centrally mediated paradoxical > slowing HR + reducing LV contractility = sudden arterial hypotension
How does tissue hypoxia lead to vasodilation?
ATP synthesis in SMC decreases = opening of K/ATP channels = hyperpolarisation = restricted Ca entry = relaxation
How does increased local adenosine release lead to vasodilation?
Activated endothelial K/ATP channels > potentiates release NO
How does increased CO2 + H+ lead to vasodilation?
H+ blocks Ca channels = reduced influx
How does increased K+ lead to vasodilation?
Initial depolarisation opens Kc outward rectifier channels = VSMC hyperpolarisation = reduced Ca entry
What is seen on an ECG in IHD?
ST depression
ST elevation
T wave changes e.g. inversion
What is the golden ECG rule?
AP moving > +ve input of amplifier causes upward deflection
What do abnormalities in leads I, III and aVF suggest problems in?
RCA + inferior portion of heart
What do abnormalities in leads V1-V6 suggest problems in?
LAD + anterior portion of heart
What do abnormalities in leads I, V5, V6 and aVL suggest abnormalities in?
Circumflex + lateral portion of heart
