Cardiovascular Physiology Lecture 6

Front 1

what causes cardiac arrhythmias?

Back 1

abnormalities of impulse generation or abnormalities of impulse conduction

Front 2

why do arrhythmias arise?

Back 2

organic disease of the intrinsic conduction system or extrinsic influence upon the activity of the intrinsic conduction system or the contractile myocardium

Front 3

what do abnormalities of impulse generation cause?

Back 3

cardiac arrhythmias

Front 4

what do abnormalities of impulse conduction cause?

Back 4

cardiac arrhythmias

Front 5

a disruption of normal sinus rhythm does what to the heart?

Back 5

renders it a less efficient pump

Front 6

what does NSR stand for?

Back 6

normal sinus rhythm

Front 7

what do arrhythmias do to the heart?

Back 7

render it a less efficient pump

Front 8

what is the major clinical relevance of any arrhythmia?

Back 8

negative impact upon cardiac output, which is a hemodynamic consideration

Front 9

what are the relevant genereric concepts that apply to any arrhythmia?

Back 9

location, frequency, timing

Front 10

what does naming the location of an arrhythmia lead to?

Back 10

an implication of the potential hemodynamic outcome or severity of the lesion

Front 11

what does location of arrhythmia affect in treatment?

Back 11

drug therapies because cells in different anatomical locations exhibit differing sensitivities to the mechanisms of action

Front 12

what is frequency as it applies to arrhythmia?

Back 12

how often and at what rate a rhythm disturbance occurs

Front 13

what does 'how often' an arrhythmic event occur affect hemodynamics?

Back 13

if the event renders the heart hemodynamically inefficient at ejecting blood, the more often it occurs, the more hemocynamically compromising (thereby clinically relevant) the arrhythmia will be for the individual

Front 14

what does 'at what rate' an arrhythmic event occurs affect hemodynamics?

Back 14

both brady- and tachy-arrhythmias can negatively affect cardiac output (by decreasing it)

Front 15

what does the term brady- mean?

Back 15

slow

Front 16

what does the term tachy- mean?

Back 16

fast

Front 17

how do brady arrhythmias affect cardiac output?

Back 17

because a decrease in heart rate results in lower cardiac output as shown by CO = HR * SV

Front 18

how do tachy arrhythmias affect cardiac output?

Back 18

because increased HR can negatively affect ventricular filling, leading to decreased stroke volume in CO = HR * SV

Front 19

what is timing as it applies to arrhythmias?

Back 19

the juxtaposition of an arrhythmic event in relation to what has preceded it

Front 20

what is reentry?

Back 20

Return of the same impulse into an area of heart muscle that it has recently activated but that is now no longer refractory, as in reciprocal rhythm

Front 21

how does reentry affect arrhythmias as a timing event?

Back 21

critical timing element for unidirection depolarization

Front 22

why is the period of ventricular repolarization vulnerable to arrhythmia?

Back 22

this is the time when the ventricular myocardium is vulnerable because cells repolarize at different rates

Front 23

during ventricular repolarization, what states might individuals cells be in?

Back 23

fully repolarized, relative refactory period, absolutely refractory

Front 24

what might occur to myocardium if an electrical impulse is transmitted during ventricular repolarization?

Back 24

cells that are fully repolarized will depolarize while cells that are in the relative refractory period may or may not depolarize depending on their membrane potential at that moment and strength of the impulse, while those in absolute refractory will not depolarize

Front 25

what does the differences in depolarization between cells in the myocardium after an electrical impulse result in?

Back 25

the timing situation facilitates the development of ventricular fibrillation

Front 26

what is a ventricular fibrillation?

Back 26

a lethal arrhythmia characterized by random cellular discharge rather than organized impulse propagation

Front 27

what doe the electrical activity of the heart determine?

Back 27

the mechanical activity

Front 28

what does ventricular fibrillation do to the electrical and mechanical activity of the heart?

Back 28

the electrical activity is random and obliterates mechanical pumping efficiency

Front 29

what could cause ventricular fibrillation?

Back 29

electrical shocks from power cords or lightening strikes, and with PVC (an internal event) occuring during ventricular repolarization

Front 30

A NSR followed by a PVC during a T-wave is problematic because of?

Back 30

timing

Front 31

what is a sinus tachycardia?

Back 31

increase in heart rate

Front 32

what is sinus bradycardia?

Back 32

decrease in heart rate

Front 33

an animal at rest should manifest the BLANK end of the HR range for that species?

Back 33

lower

Front 34

an animal actively exercising should manifest the BLANK end of the HR range for that species?

Back 34

higher

Front 35

what is the normal HR range of dogs?

Back 35

60-160 bpm

Front 36

what is the normal HR range of cats?

Back 36

120-220 bpm

Front 37

what is the normal HR range of horses?

Back 37

24-60 bpm

Front 38

what may cause sinus bradycardia?

Back 38

excessive cholinergic influence relative to adrenergic influence

Front 39

what may cause sinus tachycardia?

Back 39

excessive adrenergic influence relative to cholinergic influence