Clinical Flashcards by Jennifer Simpson

What is the P wave?

atrial depolarization

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What is the PR interval? Normal interval?

start of atrial depolarization to start of ventricular depolarization; .12-.20 seconds (3-5 small boxes)

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What is the QRS complex? Normal duration?

ventricular depolarization; 0.05-0.10 seconds (1-3 small boxes)

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What is the ST segment?

end of QRS complex to beginning of T wave; plateau phase 2 for ventricles (rapid ejection phase)

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What do ST depressions represent?

subendocardial ischemia

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What do ST elevations represent?

subepicardial or transmural injury/ischemia

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What is the T wave? What do inverted T waves and tall upright T waves represent?

ventricular repolarization
inverted T wave = ischemia
tall upright T wave = hyperkalemia

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What is QT duration?

reflects time of ventricular activity (both depolarization and repolarization)

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What is the PR segment?

reflects time delay between atrial depolarization and ventricular depolarization

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What does sinus tachycardia look like?

sinus rhythm (P wave before every QRS) but HR is above 100bpm

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What does premature atrial contraction (PACs) look like?

QRS complex is the same throughout but there will be occasional extra beats w/ abnormal P wave and then a lengthy pause afterwards

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Physiology of PACs

atrial depolarization somewhere other than SA node (closer to AV node b/c P wave is closer to QRS); long pause b/c SA node is depolarized when it would normally fire

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What do premature ventricular contractions (PVCs) look like?

widened QRS complex; too many in a row can turn into Vtach

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Physiology of PVCs

ventricular depolarization somewhere other than His/Purkinje system; myocardial muscle has slower conduction rate (widened QRS)

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What does atrial fibrillation (Afib) look like?

irregularly irregular rhythm; variable rate w/ no P waves present; R to R interval is all over the place

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Physiology of Afib

multiple foci depolarizing in atria; can also have rapid ventricular response (tachycardia)

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Multifocal PVCs

PVCs coming from different regions of ventricular muscle; each will look different

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What does ventricular tachycardia (Vtach) look like?

extremely high HR w/ widened QRS

What does non-sustained monomorphic ventricular tachycardia look like?

Vtach with occasionally normal beats; all runs of Vtach look the same b/c they come from same loci

What does supraventricular tachycardia (SVT) look like?

fast HR w/ narrow QRS (not Vtach) and R to R interval will be the same (not Afib)

What does 1st degree AV block look like?

more than 1 large box between P wave and QRS complex

What causes a deflection on an ECG?

when part of cardiac tissue is at a different membrane potential than the rest of the heart; will be at isoelectric point when all cardiac tissue has same membrane potential

What are inferior leads?

II, III, aVF

What are septal leads?

V1 and V2

What are anterior leads?

V2, V3, and V4

What are lateral leads?

V4, V5, V6, I, and aVL

What is normal axis?

between -30 and +90 -> current moves from RA to apex (down and to the left)

How would you determine LAD? What does it mean physiologically?

left axis deviation = lead I upright and aVF inverted (up and to the left); generally means left ventricular hypertrophy

How would you determine RAD? What does it mean physiologically?

right axis deviation = lead I inverted and aVF upright (down and to the right); generally means right ventricular hypertrophy

What do you call inverted I and aVF?

extreme right axis deviation

What is the J point?

first point of the ST segment (junction between QRS complex and ST segment)

Describe the difference between unstable angina (UA) and NSTEMI

both have ST depressions, T wave inversion, and chest pain UA or NSTE acute coronary syndrome (ACS) has normal cardiac enzymes NSTEMI has elevated cardiac enzymes

What indicates a STEMI is occurring?

ST elevation of 2mm (2 boxes) or > at J point | ST elevation of 1.5mm or > in women or 1mm or > in 2 or more contiguous chest or limb leads

What appears on ECG if there is an infarction?

Q waves -> dead tissue lacks depolarization

What appears on ECG if there is an injury?

ST segment shifts -> deficient blood supply means there is an inability to fully polarize

What appears on ECG if there is ischemia?

T wave changes -> impaired repolarization due to deficient blood supply

Where would you see an anterior MI? What artery is involved?

V1-V4; LAD or anterior interventricular A.

Where would you see an inferior MI? What artery is involved?

II, III, aVF; right coronary A.

Where would you see a lateral MI? What artery is involved?

I, aVL, V5-V6; circumflex A. (also diagonal A. of LAD)

Where would you see a posterior MI? What artery is involved?

V1-V3; posterior descending A/posterior interventricular A.

How would you actually determine a posterior MI had occurred?

Pt would have ST depressions in V2-V3 b/c leads are on anterior side of heart (would mirror the MI); flip the ECG upside down to see elevations

What might you also see with an MI on ECG besides ST elevations?

ST depressions -> reciprocal changes in different leads

What may become permanent on pt's ECG after having a STEMI?

Q waves; would appear days after infarct