ECG 2

Common causes of inverted U waves

- Early MI - Coronary artery disease - Hypertension - Valvular heart disease - Congenital heart disease - Cardiomyopathy - Hyperthyroidism

Most common causes of AVB: (7)

- Fibrosis of conduction system - Medications (Verapamil, Diltiazem, Amiodarone and Adenosine) - Cardiac surgery (AVR or TAVR) - Vagal tone (sleep, sports, pain) - Cardiomyopathies - Myocarditis (septal scarring) - Hyperkalemia

Cardiac events represented by the PR Interval:

- Impulse initiation - Atrial depolarization & repolarization - AV node stimulation - His bundle stimulation - Bundle branch and Purkinje system stimulation

Differential for PR segment depression includes: (3)

- Normal variant: d/t atrial repolarization which pulls the PR segment downward - Pericarditis - Atrial infarction: extremely rare

QRS Assess: Size of vector reflects _______ Depends on:

- Number of action potentials in a certain direction - number of cells and size of ventricles

4 things that cause shorter QRS complexes:

- Pericardial effusions - Obesity - Amyloid deposits - Pleural effusion (decreased amp in V5-V6 where effusions accumulate)

P Pulmonale: caused by ________(from pulmonic stenosis, TR, pulmonary hypertension) P wave amplitude ____

- R atrial enlargement - >2.5mm

QRS Height: altered by ____ and ______ of vectors

- Size & direction

Normal duration of P wave:

0.08 to 0.11 sec

Normal duration of PR interval

0.12-0.20 sec

Large U waves are abnormal (max normal amplitude is _______)

1-2 mm

P waves are normally positive in leads ____, negative in _____+ and positive or negative in other leads

1. I, II and V4 through V6 2. aVR

P wave abnormalities: P Mitrale: caused by ________ (often from mitral stenosis) Duration of P wave will be ____ in Lead II

1. L atrial enlargement 2. >120 ms

Tp wave usually obscured by ____. When might it be seen?

1. QRS 2. non-conducted beats or AV dissociation

WPW Tx:

1. Radiofrequency catheter ablation in EP lab 2. Consider procainamide, flecainide or shock

P wave starts with firing of _____ and includes impulse through _____

1. SA Node 2. 3 intranodal pathways, the Bachmann bundle and atrial myocytes

PR interval covers all events from initiation of impulse in ______ up to ______

1. SA node 2. ventricular depolarization

WPW syndrome: a _________ of the QRS complex immediately follows the P wave it is also known as a "delta wave,". The duration of the QRS is usually lengthened to ____

1. slurred upstroke 2. 0.12 s.

WPW: Individualized assessment is important—pathways that have R:R intervals of less than ________ confer higher risk of sudden death

220 ms

Mobitz type ___ has a higher risk of complete heart block compared to Mobitz type ___

2; 1

Shortened PR interval?

<0.11 seconds

Abnormally short QTc?

<350 ms

First Degree AV Block: PR interval; Caused by

> .20 seconds(5 small boxes); diseased AV Node

PR interval indicative of 1° AVB

>0.20 seconds

A QTc longer than _____ is associated with increased risk of TdP

>500

3rd Degree HB results from: (3)

AMI, Digitalis toxicity, degeneration of conduction system

Third Degree AV Block:

AV dissociation (usually b/tw AV junction & Bundle of His)

Mobitz II: block occurs after the _______ within the _______, or within both bundle branches

AV node; bundle of His

What meds should you avoid with WPW tx? (1 gen, 5 specific)

AVOID ALL AV NODAL BLOCKERS. Do not give: Amiodarone, beta-blockers, calcium channel blockers, adenosine or digoxin!

Which med might you consider for assessment (only in narrow complex non-WPW tachyarrhythmias)

Adenosine

The normal U wave is asymmetric with the (ascending/descending) limb moving more rapidly than the (ascending/descending) limb (just the opposite of the normal T wave)

Ascending; descending

SVT: Impulse originates in ____ & passes through ____

Atria; Bundle of His

P wave: (atrial/ventricular) (repolarization/depolarization)

Atrial depolarization

Tx (3) for LQTS?

BB, Mg (TdP), AICD

P-wave in V1 may be ______ d/t negative deflection caused by depolarization of the LA

Biphasic

Congenital vs Acquired LQTS:

Congenital: malfxn of cardiac ion channels from gene mutations Acquired: Metabolic abnormalities or drugs

______ has been found to be associated with an increased risk of paroxysmal atrial and ventricular fibrillation and sudden cardiac death

Congential short QT syndrome

What causes AV Blocks?

Diseased conduction system (temp or perm)

T/F: T wave should be symmetrical

F: Asymmetrical- 1st part rising or dropping slowly and latter part moving faster

T/F: T wave represents ventricular depolarization & should be in the same direction as the QRS complex

F: Ventricular REpolarzation

The WPW pt in Afib (3)

FBI: fast, broad, irregular

QTc corrects QT for ___

HR

Mobitz type II is secondary to disease involving the ______, in which there is a failure to conduct impulses from the atria into the ventricles

His-Purkinje system

______ create taller or deeper QRS complexes

Hypertrophied ventricles & areas of infarct (d/t scar tissue)

J wave: Long slow deflection that can sometime occur in ____

Hypothermia

Benign Q waves commonly found in leads ___ d/t ________

I, aVL & V6 d.t septal innervation (septal Qs)

Biatrial Enlargement: large P wave in Lead ___ and large biphasic p wave in ____

II; V1

The QT interval is (directly/inversely) proportional to HR

Inversely

U wave is (directly/inversely) proportional to HR (usually becomes visible when HR____)

Inversely; <65

Causes 40% of AVB

Ischemia/infarction

What's the useful rule of thumb to be known about a normal QT?

It should be less than half the preceding RR interval

This syndrome can present as syncope, seizures, or sudden cardiac death 2/2 polymorphic Vtach

LQTS

In which leads should the QT interval be measured?

Lead II or V5-6

2 main types of preexcitation syndromes:

Lown-Ganong-Levine syndrome & WPW

During the ST segment, ventricles are b/tw depolarization & repolarization. What is the myocardium doing?

Maintaining contraction to push the blood out of the ventricles

Measuring QT interval: Several successive beats should be measured w/ _____ taken

Maximum interval

Prolonged QTc in men & women

Men: >440ms Women: >460 ms

(Majority/Minority) of patients with WPW features on EKG will experience WPW syndrome

Minority

Why might pts w/ LQTS need EP study or long term monitoring?

Only 60% of patients show long QT on initial ECG

Second degree AV blocks are occasional non-conducted _______ with prolonged ________.

P waves; RR intervals

beginning of P wave to beginning of QRS complex

PR Interval

Mobitz II:

PR intervals constant between dropped beats, can precede 3° AVB—be prepared to pace

Mobitz I (Wenckebach):

PR intervals lengthen progressively until a beat is dropped, usually benign

The normal U wave has the same ________ as the T wave and is usually ______ the amplitude of the T wave

Polarity; less than one-third

If rhythm is sinus rhythm, P-wave is always (positive/negative) in lead II

Positive

Intrinsicoid deflection reflects amount of time it takes an electrical impulse to travel from _____ in the endocardium to ____

Purkinje system;epicardium

First downward deflection after the P wave (can be present or absent)

Q wave

LGL syndrome: characterized by a ________ that immediately follows the _____. The ________ of the QRS complexes are normal.

QRS complex; P wave;appearance and duration

J point: Where ____ ends & ____ begins

QRS complex; ST segment

Components of QT interval

QRS, ST segment and T wave (beginning of Q to end of T)

Intrinsicoid deflection is measured from beginning of ____ to beginning of ______ in leads that begin with an ____ and do not contain a ____

QRS; negative downslope of R wave; begin w/ R wave but no Q wave

1st (+) deflection after P wave

R wave

1st (-) deflection after R wave

S wave

3rd Degree AVB: High risk of ______. What should you prepare for?

Sudden cardiac death; Temporary pacing available and plan for permanent pacemaker

T/F: 2 degree AVB are usually benign & do not require tx

T

T/F: Can present with syncope due to auditory stimulation or exertion, may have been diagnosed with epilepsy or sensorineural hearing loss

T

T/F: in Mobitz type II there are no changes in the PR interval, even after the non-conducted P wave

T

What is the maximum slope intercept method is used to define?

The end of the T wave

Which HB is caused by AV nodal dz or a dz involving the His-Purkinje system caused by: CAD, enhanced vagal tone, structural heart disease (MI hypertrophy, post-cardiac surgery, cardiomyopathies, rheumatologic diseases, autoimmune diseases, amyloidosis, sarcoidosis, muscular dystrophy)

Third Degree HB

Depolarization of the atria, deflects in opposite direction of P wave

Tp wave

T/F: Most patients with SVT are hemodynamically stable

True

T/F: Symmetrical T waves are often a sign of pathology

True

T/F: many of the conditions causing prominent U waves will also cause a long QT

True

T/F: J point- Any ST segment elevation in a symptomatic patient should be considered significant

True (Attempt to obtain old EKG to compare)

In a normal EKG T wave is always upright in leads ____ and always inverted in leads ___

Upright: I, II, V3-V6 Inverted: aVR

An abnormally prolonged QT is associated w/ an increased risk of ______

Ventricular arythmies (est. TdP)

QRS complex: (atrial/ventricular) (repolarization/depolarization)

Ventricular depolarization

Tp wave can draw the ST segment downward in which condition?

Very fast tachycardias

When measuring the QT interval, should large U waves fused to the T wave be included in the measurement?

Yes (smaller U waves or ones separate from T wave should be excluded)

PR interval abnml- Preexcitation syndromes: an ___________ conducts the impulse down from the atria to the ventricles; its conduction speed is (faster/slower) than in the AV node

additional bundle; faster

PR segment should be on ______. Note elevation or depression.

baseline

Why is intrinsicoid deflection shorter (0.035 seconds) in R precordial leads (V1 & V2)?

because RV is less muscular than LV

A negative U wave is highly specific for the presence of _________

heart disease

2 instances when Q wave is significant:

if 0.03 seconds or wider or height is >/= 1/3 height of R wave

PR segment should be _____

isoelectric

ST Segment: end of QRS to beginning of T wave, should be electrically ____ time for the heart

neutral

Pts with WPW can go into extremely rapid Afib, which can cause sudden cardiac death due to ______

rapid conduction down an accessory pathway

Where are U-waves usually best seen?

right precordial leads especially V2 and V3

Third Degree AV Block:Awake patients can be symptomatic, usually _______ due to low ________

syncopal; cardiac output

Intrinsicoid deflection is longer when there is:

ventricular hypertrophy or bundle branch block