Heart 3 Flashcards
Refractory periods are due to these two things
Voltage- and time-dependence of sodium (fast response) and calcium (slow response) channels
Which response is the more time-dependent? More voltage-dependent?
Time-dependent: slow response (calcium)
Voltage-dependent: fast response (sodium)
Nickname for the RRP
The “vulnerable” period of the heart
R-on-T phenomena
Premature beat (R wave) that occurs during the relative refractory period (T wave) of the previous beat
Two other names for R-on-T phenomenon
Unifocal PVC’s or nonsustained ventriculuar tachycardia
Torsades de pointes
Polymorphic ventricular tachycardia, when the heart starts having circular electrical activity that ranges all around the heart (looks like uneven spikes on an EKG)
Commotio cordis
“Agitation of the heart”; often lethal disruption of heart rhythm that occurs as a result of a blow to the area directly over the heart at a critical time during the cycle of a heart beat, causing cardiac arrest
To what pathology is commotio cordis related?
Ventricular fibrillation (NOT mechanical damage to the heart)
Fatality rate of commotio cordis
65%
Prime population for commotio cordis
Boys and young men at an average age of 15; many of whom play baseball
Post-repolarization refractoriness
Even though all the sodium channels are available again, the calcium channels are time-dependent instead of voltage-dependent, not allowing for another AP to fire even though it is electrically neutral
EKG changes with decrease in systolic time
Decrease in the QT interval
How to measure the action potential time from an EKG
Q-T interval
Prolonged Q-T syndrome
Abnormal prolongation of the Q-T interval
Causes of acquired Q-T syndrome
Bradycardia, hypokalemia, and quinidine
