Other Arrhythmias

Ventricular Tachycardia-
-appears like a run of PVC's
-usually is significant for coronary artery disease or poor oxygenation of the coronaries
-originates from a single ventricular ectopic focus
-rate 150-250 beats per minute

Ventricular Fibrillation-
-disorganized rhythm of multiple ectopic ventricular foci
-needs to be defibrillated

Torsades de Pointes-
-"Turning on a point"
-can be from magnesium deficiency

Atrial Flutter-
-originates from a single atrial ectopic focus
-Atrial rate of 250-350 beats per minute
-saw tooth pattern

Atrial Fibrillation-
-originates from multiple atrial foci
-atrial rate of 350-450 beats per minute
-irregularly irregular rhythm

Miscellaneous

Pulmonary Embolus-
-Commonly see large S wave in lead I, ST depression in lead II, and a Q wave with an inverted T in lead III.
-there is commonly T wave inversion in lead V1-V4
-may cause a right bundle branch block

Hyperkalemia
-with elevated K the P wave is flattened, the QRS complex is widened, and the T wave becomes peaked

Hypokalemia
-with low K the T wave becomes flattened, and there can be a U wave

Hypercalcemia
-the QT interval becomes shortened



Hypocalcemia
-the QT interval becomes prolonged

Ischemia, Injury, and Infarction

Myocardial Ischemia-
-when myocardial oxygen supply does not meet demand.
-there is no tissue death
-the T wave is inverted or ST segment is depressed
-since the ventricles are closest to the chest leads, the T wave changes will be most prominent there

Injury-
-Injury indicated the acuteness of an infarct
-the ST segment elevation denotes injury
-the ST segment may be only elevated as much as 10 or more mm above the baseline

Infarction-
-if there is a ST elevation, this means that the infarction is acute
-the ST segment will elevate with an acute infection, and then return to the baseline
-Pericarditis can cause diffuse ST segment elevation
-A ventricular aneurysm can cause ST segment elevation
-The diagnosis of a MI is usually made by the presence of Q waves with the St elevation
-It is important to be able to recognize the location of the infarction


Anterior STEMI
-See ST elevation in leads V1, V2, V3, and V4.  V1 and V2 is sometime referred to as septal leads

Lateral STEMI
-See ST elevation in leads I, avL, V5 and V6.  Will see Q waves

Inferior STEMI
-See ST elevation in leads II, III and avF and Q waves

Posterior Wall STEMI
-there is ST depression in leads V1 and V2
-since the posterior wall of the left ventricle depolarizes in a direction of the anterior infarction

Hypertrophy

Hypertrophy-
-Refers to increase in size and muscle mass

Atrial Hypertrophy
-since the P wave denotes contraction of both atria we look at the P wave to determine hypertrophy
-Lead V1 is directly over the atria, so it is the best indicator of hypertrophy
-With atrial hypertrophy we have a biphasic P wave in V1
-If the initial component of the P wave in V1 is the largest, it is right atrial hypertrophy
-If the terminal portion of the biphasic P wave in lead V1 is large and wide, this is left atrial hypertrophy

-Right Atrial Hypertrophy

-Left Atrial Hypertrophy

Right Ventricular Hypertrophy-
-See a large R Wave in lead V1
-With RVH there is more positive deflection toward the V1 electrode and would expect the QRS complex more upright than normal
-The S wave in lead V1 is smaller than the R wave
-The R wave gets progressively smaller in leads V2-V6

Left Ventricular Hypertrophy-
-Hypertrophy of the left ventricle causes QRS complexes to be bigger in both height and depth in leads V1-V6 (chest leads)
-The S wave will be even deeper in V1
-In LVH there is a large S wave in lead V1 and large R wave in lead V5
-Lead V5 is directly over the left ventricle
-The T wave often shows inversion or asymmetry

Axis

Axis
-Refers to the direction of electrical depolarization
-It is determined by the direction of the QRS complex in lead I and avF

Normal Axis
-Positive deflection of QRS complex lead I
-Positive deflection of QRS complex lead avF

Left Axis Deviation
-Positive deflection of QRS complex in lead I
-Negative deflection of QRS complex in lead avF

Right Axis Deviation
-Negative deflection of QRS complex in lead I
-Positive deflection of QRS complex in lead avF

Extreme Right Axis Deviation
-Negative deflection of QRS complex lead I
-Negative deflection of QRS complex lead avF

Heart Blocks

Heart Blocks Can occur in the SA node, AV Node, or in larger sections of the ventricular condition system

Types of Heart Blocks:
1.  Sinus Block
2.  AV Blocks
3.  Bundle Branch Blocks
4.  Hemiblocks


Sinus Block-an unhealthy SA node quits pacing activity for at least one compete cycle.  The P waves before and after the block are identical because the same SA node pacemaker is functioning before and after the pause.

AV Blocks-when minimal delays the impulse within the AV node, making a longer than normal pulse before stimulating the ventricles.
-Types of AV Blocks
1.  First Degree AV Block
2.  Second Degree AV Block Type I
3.  Second Degree AV Block Type II
4.  Third Degree AV Block


First Degree AV Block-prolonged PR interval greater than 0.2 seconds.  There is no dropped QRS complex

Second Degree Type I AV Block-the PR interval become lengthened until the P wave does not elicit a responding QRS complex.  The PR interval is greater than 0.2 seconds.  Also called Wenckebach

Second Degree Type II AV Block-also called Mobitz II is when an occasional ventricular  depolarization (QRS complex) is not conducted but dropped.  The P waves are normal and normal PR intervals are present.

Third Degree AV Block-also called complete heart block.  This is when none of the atrial depolarizations conduct to the ventricles.  The P wave rate and the QRS complex rate are independent and will march out with calipers uniformly.

Bundle Branch Blocks-
-Normally the right and left bundles transmit the electrical change to the right and left ventricles at the same time.
-When there is a bundle branch block, there is a delay in the depolarization stimulus that creates the widened QRS complex in the classic rabbit ear pattern (R and R' waves)
-If there is a bundle branch block, look at the chest leads right (V1 and V2) and left (V5 and V6)


Right Bundle Branch Block
-If there is a R,R' waves in V1 or V2 there is a right bundle branch block
-If it is only present in one of the leads it is an incomplete right bundle branch block

Left Bundle Branch Block
-Sometimes the R R' waves will only be seen as notch in the wide QRS complex in V5 and V6
-In a left bundle branch block the left ventricle fires late so the first portion of the QRS complex is right ventricle activity.  We cannot see Q waves originating from the left ventricle because they are buried in the QRS complex

Right Bundle Branch EKG:

Left Bundle Branch EKG:

Wolff Parkinson White:
-There is an accessory pathway for ventricular stimulation causing a delay in ventricle stimulation
-This occurs between the SA node and AV junction
-This produces a delta wave
-These patients are prone to SVT

Delta Wave:

Hemiblocks:
-These are blocks of the anterior and posterior division of the left bundle branch
-These are mostly due to loss of blood supply to the anterior or posterior branches of the left bundle branch

Rate

Rate-

-Normal Rate from SA Node 60-100

-Bradycardia- rate less than 60 originating from the SA node

-Tachycardia- rate greater than 100 originating from the SA node 

-When the pacemaker changes from the SA node it is referred to as an ectopic focus (different pacemaker)

-AV Node (Junctional Ectopic Focus)- also called junctional rhythm when comes from here.  Has an inherent rate of 40-60 beats per minute.  Faster than 60 is called junctional tachycardia.  Slower than 40 is referred to as junctional bradycardia.

-The ventricles have ectopic foci and are potential pacemakers.  The ventricular ectopic foci have an inherent rate of 20-40 beats per minute

Rhythm

Normal Sinus Rhythm=equal distance between similar waves (P, QRS, and T waves)

Four Varieties of Arrhythmias
1.  Sinus Arrhythmia- the pacemaker still originate from SA node but the pacemaking activity is irregular varying with inspiration and exhalation

2.  Wandering Atrial Pacemaker-the pacemaker wanders from focus to focus.  The P waves are various shapes since the origin of the pacemaker varies from within the atria.

3.  Atrial Fibrillation-multiple ectopic foci in the atria emit electrical impulses.  Since no single impulse depolarizes both atria there is a rapid series of tiny waves

4.  Escape Beat-the response to a pause in pacemaking activity.  Premature beats are made by an ectopic focus discharging spontaneously causing a beat earlier than expected.

Premature Beats
1.  Premature Atrial Contraction (PAC)-originates from an ectopic focus in the atrium that appears much earlier than normal P wave on an EKG

2.  Premature Junctional Contraction (PJC)-originates in an ectopic focus in the AV junction which fires before the normal cycle.  Usually inverted P wave occurring before, during, or immediately after the QRS complex

3.  Premature Ventricular Contraction (PVC)-originates from an ectopic focus, an occurs very early before a P wave.

With Premature beats there usually is a compensatory pause.



Tachycardias
1.  Paroxysmal Atrial Tachycardia-a rapid sudden heart rate originating from an ectopic focus from on of the atria.  The rate is usually between 150-250 beats per minute.

2.  Paroxysmal Junctional Tachycardia-a rapid sudden heart rate originating from an ectopic foci in the AV junction.  The P wave is inverted occurring before, during or immediately after the QRS complex.  Rate is between 150-250 beats per minute

-Collectively PAT and PJT are referred to as supraventricular tachycardia

3. Paroxysmal Ventricular Tachycardia-sudden ectopic focus occurring from the ventricles.  Wide complex.  Rate between 150-250 beats per minute

4.  Atrial Flutter-the ectopic focus in the atria fires at a rate between 250-350 beats per minute.  There is one ectopic focus that is why the p waves look the same.  The QRS complexes are usually equal distances between each other

Basic EKG Tracing

EKG Waves:

-P Wave-atrial depolarization
-QRS Complex-ventricular depolarization
-T Wave-ventricular repolarization
-U Wave-atrial repolarization (often absent)



-Upward deflection of the QRS complex is referred to as a positive deflection
-Downward deflection of the QRS complex is referred to as a negative deflection

Normal PR Interval-0.12-0.2 seconds (3-5 small boxes)

Normal QRS Complex-less than 0.12 seconds (less than 3 small boxes)