Dr. Zachow - Electrophysiology Part 2 Flashcards
Which area of an EKG is most vulnerable to “reentrant loops”/fibrillation?
It is at the end of the T wave. This is the recovery phase otherwise known as the depolarization phase.
What does A-fib look like On an EKG?
1) No P waves 2) Rhythm is irregularly irregular.
- there is also a protective factor in that the AV node has a delay, so the heart rate usually doesn’t go extremely high. However, it is like a traffic cop in that there are a lot of AP’s trying to get through and the AV node can only stop some of them, while other get through without interacting with the AV node.
What do an atrial flutter look like on an EKG?
1) There are P waves 2) they are being fired rapidly, like 300 bpm 3) The ventricles can either respond in a regular rhythm or not as opposed to in a-fib where it is always irregularly irregular. P waves will have the saw-tooth appearance. Usually lives in the right atrium.
What does V-fib look like an an EKG?
1) it just quivers and fibrillates.
What does ventricular tachycardia look like on an EKG?
1) we don’t really see anything except QRS waves. 2) No P waves
- You don’t see anything because there is so much quick depolarization in the ventricle that you just don’t see anything else.
What does a right or left bundle branch block look like on an EKG?
1) You would see widened QRS on the side that is being slowed down. 2) You could sometimes also see a split R.
What does a premature ventricular. Contraction look like on an EKG?
Basically you will see normal QRS, normal QRS, normal QRS, and then you will see a widened QRS out of nowhere. It is kind of like only one bundle branch block QRS. Then it goes back to normal. This is what we often call “skipping a beat”. These waves. Occur due to myocyte-myocyte contraction.
What does hypocalcemia look like on an EKG?
1) The QT interval would be prolonged
- the physiology behind that is that Type L calcium channels are reliant on extra cellular calcium. If there isn’t enough calcium, then the Type L channels get sluggish and the plateau phase lasts longer and the channels stay open for longer.
What does hyperkalemia (increased K+ concentration) look like on an EKG?
1) No P waves 2) There is a “taller tented T Wave”
- physiology is that K+ is responsible for repolarization.
What is the general mechanism of action of antiarrythmic medications and why does that work?
We try to delay depolarization and prolong repolarization. We do this because we want to increase the likelihood of the cells being in a refractory period So that the ectopic AP will not affect these cells. We often use beta-blockers. The other mechanism of action is to target the various ion channels. Can target Na+ to delay rapid depolarization in plateau potentials. You can also target K+ channels to prolong repolarization.
Cardizem
AV nodal type L channel blocker. Causes heart rate to drop. Ca+ is responsible for slow contraction. In the. Pacemaker cells. If there is less Ca+ Then the contraction will be slowed.
Digitalis/Dijoxin
1) Increased inotropy 2) Impedes AV nodal transmission
What does an MI look like on an EKG?
1) Inverted T waves 2) New Q waves 3) Increased ST elevation
Who feeds who?
Left coronary artery:
- left circumflex - left lateral wall
- left anterior descending - anterior, interventricular septum
Right coronary artery:
- right heart, diaphragmatic, posterior
Which leads would pick up MI where?
- (left) Lateral, inferior, anterior, posterior
Lateral - I, aVL, V5, V6
Inferior - II, III, aVF
Anterior - V1-V6
Posterior - reciprocal changes in V1 - Prominent R wave.
