Electrical Physiology 2

Question 1

correlation of chest leads to part of heart/blood supply?

Answer 1

V1/V2 are septal, RV. V2, 3, 4 anterior mostly LV. V5, 6 anterolateral so LV. all supplied by left anterior descending artery

Question 2

correlation of limb leads and part of heart/blood supply?

Answer 2

I, aVL are lateral –> circumflex. II, III, aVF are inferior –> circumflex or PDA branch from right coronary

Question 3

lead vectors mostly get signal from?

Answer 3

left ventricle area closest to chest wall in direction of leads

Question 4

order of conduction in heart

Answer 4

SA node, AV node, His bundle, left and right bundle branches

Question 5

P wave generated by? direction of signal?

Answer 5

atrial depolarization from SVC/RA junction; signal spreads left and down –> P wave is the fusion of signal when RA then LA depolarize

Question 6

QRS is the fusion of? but what is more important?

Answer 6

fusion of RV and LV firing but LV has more muscle so overwhelms RV signal

Question 7

systole vs. diastole: what de/repolarizes first and what signal do you get

Answer 7

systole: endocardium depolarizes first = positive QRS. diastole: epicardium first so negative way going away = positive T wave

Question 8

ECG defs: P? Q? R? S? R’? T? U?

Answer 8

P = atrial repolarization. Q = first negative deflection, R = 1st positive deflection, S = 2nd negative, R’ = 2nd positive –> all with ventricular depol. T = ventricular repol. U= occasional finding, areas of very delayed depolarization

Question 9

PR/PQ interval? represents? due to?

Answer 9

PR/PQ = distance from start of P to start of QRS. represent delay between atrial and ventricular depolarization –> due to AV nodal delay

Question 10

ST segment? J point?

Answer 10

ST segment = plateau line from J point to T wave onset. J-point is the QRS/JT junction.

Question 11

QT interval is what?

Answer 11

start of Q to end of T: time from ventricular depolarization to full repolarization; rough measure of ventricular mechanical systole

Question 12

ventricular depolarization: which leads?

Answer 12

lateral leads I, aVL, V5 and C6 looks at signal going left. inferior leads II, III, avF, V5 and V6 look at signal going down

Question 13

small Q waves are common in what leads? why do we see them?

Answer 13

the left sided (lateral) leads. initial septal depolarization goes away from the leads.

Question 14

when are Q waves in inferior leads normal?

Answer 14

if initial septal depolarization is a bit superior as well as going from left to right

Question 15

large Q waves mean?

Answer 15

myocardial damage or scar –> dead tissue doesn’t have electrical activity; will only see depolarization going away from it in the tissues around the scar

Question 16

anything that disrupts depolarization will affect? which affects? examples of things that will disrupt this?

Answer 16

repolarization –> will see ST and T changes. electrolyte abnormalities, temperature/pH, drugs, abnormal source of electrical depol. structurally abnormal myocardium.

Question 17

most important cause of ST/T changes

Answer 17

lacking oxygen or blood supply = ischemia

Question 18

what does ischemia look like (AP tracing)

Answer 18

less positive in systole, less negative in diastole; slightly longer AP

Question 19

worst area of ischemia is where? why?

Answer 19

sub-endocardium because it’s the farthest away from the epicardial artery blood supply and it’s exposed to the highest pressures in systole

Question 20

subendocardial ischemia vs trans mural ischema: what happens to ST?

Answer 20

subendocardial = ST depression and abnormal T. trans mural = ST elevation