Cardiac Elecetrophysiology Flashcards
What are the normal intervals and what do they represent for the following on an electrocardiogram... P PR interval QRS ST T QT
P: 0.08-0.12; atrial contraction PR Interval: 0.12-0.20; atrial contraction to beginning of ventricle contraction QRS: 0.10; ventricular contraction T: ventricular depolarization QT: 0.40 ventricular depol to repol
What are common pathologies of the following on electrocardiogram (what do they indicate), and what morphologies or time frames indicate them P PR QRS ST QT
P indicates atrial contraction, a missing “p” or many “p” indicate atrial fib or flutter
PR interval that is > 0.20 is an indication of 1 Heart Block
QRS that is prolonged > 0.10 is an indication of a Bundle Branch Block
ST segment is often where myocardial ischemia shows up and will be raised or depressed by 1 mm
QT that is > 0.40 is associated with ventricular arrythmias
Which direction do leads I, II, III run on a standard 3 lead EKG? And from what pole to pole? Which lead has two negative poles? Which has two positive? Which has a - and a +
Lead I runs R arm to L arm ( - to +)
Lead II runs R arm to Lower Extremity (- to +)
Lead III runs L arm to Lower Extremity (- to +)
Two negatives: right upper
Two positive: lower extremity
-/+: left upper
What is the value in seconds of one small box on an EKG? What is the value of one large box composed of 5 small boxes? How can HR be calculated via large box count from beat to beat?
1 small box: 0.04
1 large box: 0.20
Count the number of large boxes from peak R to peak R, take this number and divide by 300
What are the 12 leads of a 12 lead EKG? Which coronary arteries do they represent? Which aspect of the heart do they monitor?
I - Circumflex of LCA - lateral II - RCA - inferior III - RCA - inferior AVR - nothing AVL - Circumflex of LCA - lateral AVF - RCA - inferior V1 - LAD - septum V2 - LAD - septum V3 - LAD - anterior V4 - LAD - anterior V5 - Circumflex - lateral V6 - Circumflex - lateral
What portion of the heart does the circumflex artery supply? [anterior, posterior, inferior, or lateral]? What about the RCA? What about the LAD
Circumflex: lateral
RCA: Inferior
LAD: Septum and the Anterior
Which coronary artery determine “dominance”? Does it originate from the RCA or LCA?
The Posterior descending artery. It originates from the RCA in a majority of individuals, but may originate from the LCA via the circumflex
Which artery (arteries) commonly supply the AV node?
The SA node is supplied by the RCA in 60% of individuals and the Circumflex of the LCA of 40%
Describe the EKG of 1st degree heart block, 2nd degree types I and II, and 3rd degree block. What part of the conduction system does each effect? What is the appropriate treatment or response for each?
1 HB: presents as a prolonged PR interval of >0.20 sec. It indicates a longer then expected delay at the AV bundle. No treatment is required - monitor
2HB: presents as an absent of 1:1 match of atria to ventricle as conduction through the AV is periodically missed. Type I presents as a progressing PR interval that eventually drops a QRS. Type II presents with drops of QRS without any particular progressing pattern of PR prolongation. Treatment is monitor and any thing that may discourage conduction and further block
3HB: complete AV block, with no particular pattern present on EKG on when QRS appears or not. This rhythm will be driven by the AV or slower ectopic points so HR is generally < 60bpm. Patient may need support via pacer (internal or external) or isopruteronal
Any patient that is hemodynamically unstable may need some support to optimize CO
What does a bundle branch block mean? Which is more concerning LBBB or RBBB? How is a BBB illustrated on EKG?
A BBB is a slowing or block of conduction through one of the branches through the R or L ventricle. Therefore one can have a LBBB or a RBBB. A LBBB is clinically significant and is illustrated by prolonged QRS (>0.10 sec) and “rabbit ears”.
What is a reentry pathway? What arrythmias do they cause? What is the name of the most common pathway associated with WPW Syndrome?
Pathways by which a looping electric circuit is created from atria to ventricle that bypasses normal conduction pathway. Examples include atrial flutter, atrial fibrillation, supraventricular tachycardia, vfib, vtach.
The most common pathway is called “Kents Bundle” and it connects the L atrium and L ventricle in a circuit
What is the difference between conduction of the heart in a normal rhythm and in WPW? What is a “delta wave” on EKG with WPW and why is it there? What other indications present themselves on EKG (PR interval, QRS, etc)
WPW goes through the AV node and the accessory pathway, therefore part of the signal is not delayed. This results in delta waves [early upslope of QRS] and tachyarrythmias. The PR interval is shortened [due to accessory pathway] and the QRS is prolonged.
What is the difference between “narrow” and “wide” QRS WPW Syndrome? How should each by treated and why? What about Afib or Aflutter in WPW?
Narrow complex WPW syndrome indicates that the conduction pathway is primarily using the AV node and thus ventricular conduction is normal.
Wide complex WPW syndrome indicates that the accessory pathway is the primary conduction pathway and ventricular contraction is not normal.
Blocking the AV node with a beta-blocker or calcium channel blocker in wide complex QRS will promote the accessory pathway, tachyarrythmia, and possibly promote an unstable rhythm.
If narrow complex QRS is present then it is ok to use a beta blocker or a CBB to treat the tachyarrythmia. If a wide complex QRS is present then procanimide or amiodarone should be used as to not block the AV node, promote the accessory pathway and possible further unstable arrythmia
Afib or Aflutter should be treated like wide complex WPW; with procanimide or Cardioversion
What medications can be used to treat tachyarrythmia associated with WPW syndrome? Which medications MUST be avoided in wide complex WPW syndrome? Which should be used in wide complex WPW sysyndrome and why?
Beta-Blockers, CCB such as Verapamil, Amiodarone, Flecainide, Adenosine, Cardioversion
AVOID beta-blockers, verapamil or other CCB, adenosine, and lidocaine in wide complex WPW (antidromic). Use flecainide, amiodarone, or Cardioversion in wide complex WPW syndrome as these favor slowing signals through accessory pathways instead of AV node.
What is the most appropriate treatment for hemodynamically unstable WPW syndrome? How much of a “dose”? Before attempting this what should be considered?
Cardioversion. 100 J then 200-360 J. Consider hx or presences of Afib and for how long - risk of clot formation and embolism if converted.
