Clin Prac 5 HR needed (slit up)

Question 1

Av node re-entrant rhythms
define overall

Answer 1

The AV node has the role of slowing conduction between the atria and the ventricle to allow time for blood to flow and fill the chambers ready for ejection.

Within the AV node are fast and slow channels – these allow for variable conduction and repolarisation within the AV node itself. They also allow the potential for re-entrant rhythms.

A quickly arriving electrical impulse can arrive and trigger the faster repolarising cells in the AV node to set up a new QRS complex before the SA node is itself ready to go again. An atrial ectopic beat is an example of such a quickly arriving impulse

Question 2

Atrial re-entrant tachycardia
define

Answer 2

Atrial re-entrant tachycardia involves the impulse spreading from the AV node, through the ventricle and finding an aberrant way to return to the atria. This is usually via an accessory pathway. This allows it to travel a loop and return to the AV node before the SA node has fired again. It enters the AV node and stimulates the faster repolarising cells that are ready. In this fashion a rapid loop is established between AV node – aberrant channel – AV node again forming an SVT

Typically involves an accessory pathway outside the AV node. In AVRT, there is an abnormal conduction pathway that connects the atria and ventricles, bypassing the AV node. This accessory pathway can create a reentry circuit that causes the rapid heart rate characteristic of SVT

Question 3

Atrial re-entrant tachycardia
rate/rhythm ect.

Answer 3

Rate: 140-250
Rhythm: Vent. (R-R): irregular / regular
P-Wave: hidden, non-discernible
P-R Interval: unmeasurable
QRS Complex: <0.12sec (<3 small squares), a delta wave, which is an early upstroke of the QRS complex due to pre-excitation of the ventricles by an accessory pathway (bypassing AV)
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 4

AV nodal re-entrant tachycardia
define

Answer 4

The AV nodal re-entrant tachycardia is a fast channel repolarised and ready to conduct. It can trigger the slow channel thus setting up not only a new QRS, but also starting a loop within the AV node itself

In AVNRT, there is a reentry circuit within the AV node that allows electrical impulses to continuously cycle through it and cause a rapid heart rate

Question 5

AV nodal re-entrant tachycardia
rate/rhythm ect.

Answer 5

Rate: 150-250
Rhythm: Vent. (R-R): regular
P-Wave: hidden, non-discernible
P-R Interval: unmeasurable
QRS Complex: <0.12sec (<3 small squares), narrow
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 6

First-degree atrioventricular (AV) block
define

Answer 6

First-degree atrioventricular (AV) block is an arrhythmia where there is a constant delay in electrical impulse conduction through the AV node. It may not be serious and in many cases does not require treatment. The pathophysiology of first-degree heart block is related to a delay in the conduction of electrical impulses from the atria to the ventricles (PR). A prolonged transmission of the electrical impulse through the AV junction (AV node and the Bundle of His). The significant finding of this rhythm is a prolonged PR interval of more than .20 (one square) seconds.

Question 7

First-degree atrioventricular (AV) block
rate/rhythm ect.

Answer 7

Rate: underlying rhythm
Rhythm: Atrial (P-P): regular / Vent. (R-R): regular
P-Wave: present, upright
P-R Interval: >0.20sec (>5 small squares)
QRS Complex: <0.12sec (<3 small squares)
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 8

Second-degree, type 1 AV block (Wenckebach)
define

Answer 8

Second-degree, type 1 AV block (Wenckebach) is an arrhythmia with progressive lengthening (delay) of the PR intervals until a QRS complex fails to appear after a P wave (the AV node completely blocks the impulse from passing to the ventricles). The pathophysiology in second-degree heart block is, there is a delay in the conduction of the electrical impulses from the atria to the ventricles. This is due to a delay or blockage within the AV node.

Question 9

Second-degree, type 1 AV block (Wenckebach)
rate/rhythm ect.

Answer 9

Rate: underlying rhythm
Rhythm: Atrial (P-P): regular / Vent. (R-R): irregular with the dropped beat
P-Wave: present, upright, precede each QRS complex when they are present
P-R Interval: progressively lengthens until missed QRS
QRS Complex: <0.12sec (<3 small squares)
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 10

Second-degree, type II AV block (Mobitz type II)
define

Answer 10

Second-degree, type II AV block (Mobitz type II) is similar to type I except there is no progressive lengthening of the PR interval before the QRS is missed. Second degree heart block type 2 is a type of heart block in which some atrial impulses are not transmitted to the ventricles, resulting in occasional dropped beats. Unlike in type 1, the PR interval remains constant before the dropped beat. This is because the block is located below the level of the AV node, typically in the bundle branches or the His-Purkinje system. It may progress quickly to complete heart block and require prompt intervention.

Question 11

Second-degree, type II AV block (Mobitz type II)
rate/rhythm ect.

Answer 11

Rate: Atrial (P-P): 2 or more / Vent. (R-R): 1
Rhythm: Atrial (P-P): regular / Vent. (R-R): usually regular
P-Wave: present, upright
P-R Interval: >0.12 and consistent (>3 small squares) (more P waves than QRS - pr interval longer than normal constantly the same length but a qrs will drop)
QRS Complex: <0.12sec (<3 small squares) slightly wider than normal as this AV block involves part of the underlying bundle branch as well
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 12

Third-degree AV
define

Answer 12

Third-degree AV (or complete) block is the complete absence of conduction of electrical impulses through the AV node, bundle of His, or bundle branches. It is the most serious of AV blocks and may be transient or persist.
In third degree (complete) heart block, there is complete dissociation between the atria and ventricles, resulting in independent electrical activity of the two chambers. The atria and ventricles beat independently, and the ventricular rate is typically slower than the atrial rate. The key ECG characteristic of third degree heart block is a regular atrial rhythm with a ventricular rhythm that is slower and usually regular, but can also be irregular.

Question 13

Third-degree AV
rate/rhythm ect.

Answer 13

Rate: Atrial (P-P): 60-100 / Vent. (R-R): <60
Rhythm: Atrial (P-P): regular / Vent. (R-R): regular No relationship
P-Wave: present, upright (do not relate to the QRS) more p eaves than qrs
P-R Interval: varies, inconsistent
QRS Complex: <0.12sec (<3 small squares) usually wider given its origin in the ventricles; may be normal if the point of origin is in the AV junction
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 14

Second-degree 2:1 and advanced AV block
define

Answer 14

Are arrhythmias caused by the defective conduction of electrical impulses through the AV node or the bundle branches or both. This produces an AV block characterized by regularly or irregularly absent QRS complexes, commonly producing an AV conduction ratio of 2:1, 3:1, or greater, with or without a bundle branch block. 2:1 and advanced AV blocks are not considered to be of the classic type I or type II AV block.

Question 15

A right bundle branch block (RBBB)
define

Answer 15

A right bundle branch block (RBBB) occurs when there is an obstruction in the right bundle branch of the heart’s electrical conduction system. The right bundle branch is responsible for transmitting electrical impulses from the atrioventricular node to the right ventricle. When this pathway is blocked or delayed, the impulse is forced to travel through the left bundle branch first before reaching the right ventricle, resulting in a characteristic pattern on the electrocardiogram (ECG). MORROW (“RR” right, QRS W shape) (V2)
The pathophysiology of RBBB is characterized by the delayed depolarization of the right ventricle due to the blockage of electrical impulses through the right bundle branch. The left ventricle is activated first, followed by the right ventricle, which results in a delay in the onset of the QRS complex.

Question 16

A right bundle branch block (RBBB)
rate/rhythm ect.

Answer 16

Rate: underlying rhythm
Rhythm: Atrial (P-P): regular / Vent. (R-R): regular
P-Wave: present, upright
P-R Interval: 0.12 - 0.20sec (3-5 small squares)
QRS Complex: >0.12sec (>3 small squares)
- RSR’ pattern in V1-3 (“M-shaped” QRS complex)
- Wide, slurred S wave in lateral leads (I, aVL, V5-6) resulting in a rabbit ear appearance.
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical (the ST-segment depression and T-wave inversion in leads V1 to V3, reflecting delayed ventricular depolarization)

Question 17

Left bundle Branch (LBBB)
define

Answer 17

(LBBB)
In a healthy heart, electrical signals start in the SA node in the right atrium, travel through the atria, and then pass through the AV node to reach the ventricles. The ventricles then contract, pushing blood out to the body. The left and right bundle branches are specialized structures that conduct the electrical signals to the left and right ventricles, respectively.

In left bundle branch block (LBBB), the electrical signals to the left ventricle are delayed or blocked as they travel through the left bundle branch. This results in the left ventricle contracting later than the right ventricle (delayed depolarization), which can cause a number of changes on the electrocardiogram (ECG).
WILLAM (“LL” left , QRS M shape) (V1)

Question 18

Atrial flutter
define

Answer 18

Atrial flutter is a type of cardiac arrhythmia that is characterized by a rapid and regular atrial rhythm with an atrial rate typically between 250-350 beats per minute, and a ventricular rate that may be regular or irregular depending on the degree of atrioventricular block.

The pathophysiology of atrial flutter involves the presence of a re-entrant circuit within the atria that causes the rapid and regular atrial contractions.

The circuit is usually initiated by a premature atrial beat or a focus of automaticity that generates an ectopic impulse that travels along a slower conducting pathway, creating a loop of conduction. The loop of conduction can continue to circulate around the atrium at a very fast rate, producing a regular, sawtooth-shaped pattern of flutter waves on the electrocardiogram.

Determine the number of impulses conducted through the AV node – expressed as a conduction ratio e.g. 2:1 3: 1 4:1etc.
The most common presentation is 2:1 making a heart rate of 150bpm typical finding

Question 19

Atrial flutter
rate/rhythm ect.

Answer 19

Rate: Atrial: 250-400bpm / Vent.: variable (may be slower in patients with atrioventricular block around 150bpm)
Rhythm: Atrial (P-P): regular / Vent. (R-R): regular (The atrial and ventricular rates may be different due to varying degrees of atrioventricular block)
P-Wave: many, regular, sawtooth (sawtooth-shaped pattern of flutter waves on the ECG, with a repeating sequence of negative and positive deflections)
P-R Interval: variable
QRS Complex: <0.12sec (<3 small squares)
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 20

Atrial Fibrillation
define

Answer 20

Atrial fibrillation (AF) is a supraventricular tachycardia (SVT) and is the most common sustained dysrhythmia in the elderly and is characterised by multiple pacemaker focal points in the atria resulting in an “irregularly irregular” ventricular response (no pattern). Atrial fibrillation is a chaotic rhythm with recognizable QRS complexes. The chaotic rhythm pattern and the absence of P waves are the hallmarks of this dysrhythmia.

Atrial Fibrillation can become problematic when very fast with the combination of reduced time for ventricular filling and loss of atrial input

There is a huge association between atrial fibrillation and acute stroke. The fibrillating atria have small pockets within them where static blood, normally ejected with contraction, allows clots to form. These emboli can break off, particularly with reversion and be ejected into the aorta. This allows high likelihood of the clot travelling upward into the brain. Anticoagulant drugs are used to minimize the risk of this happening

Atrial fibrillation can spontaneously appear and revert. It is a common rhythm for patients to briefly deteriorate into when hypothermic and post-return of spontaneous circulation.

Question 21

Atrial Fibrillation
rate/rhythm

Answer 21

Rate: will vary
Rhythm: Atrial (P-P): irregular / Vent. (R-R): irregular “regularly irregular”
P-Wave: many/non-discernable (absent however
may actually look like there are lots of different-looking P waves, known as the fibrillation baseline)
P-R Interval: <0.12/unmeasurable/ (<3 small squares)
QRS Complex: <0.12sec (<3 small squares) can be narrow (the electrical activity is originating from the atria rather than the ventricles)
ST Segment: Level w isoelectric line
T-wave: rounded, slightly asymmetrical

Question 22

Ventricular tachycardia (VT)
define

Answer 22

Ventricular tachycardia (VT) is a potentially life-threatening arrhythmia that originates from the ventricular myocardium (mussel tissue). The pathophysiology of VT is characterized by the presence of a reentry circuit within the ventricular tissue, which causes the electrical impulses to circulate repeatedly through the ventricles at a rapid rate, resulting in a wide QRS complex on the electrocardiogram (ECG).

Ventricular tachycardia is more than just simply accelerated idioventricular rhythm even faster. The rate of 100 per minute is carefully chosen when discussing the cut off point between one and the other

At 100 or less, the sinus node, at least in theory, can depolarise that quickly and remain the dominant pacemaker in the heart

The strategy to deal with that slower arrhythmia is then based on the fact that the SA node has not taken over and looking for ways to deal with it

With VT on the other hand, it is firing faster than the SA node will normally fire. In this case, the response strategy is to eradicate the VT and let the SA node have a chance to reassert itself.

If high in the ventricle and near the AV node, the QRS may point in a similar direction to the normal observed pathway in that lead. Conversely, if low in the ventricle Purkinje network, the QRS might appear to be entirely in the opposite direction

Question 23

Ventricular tachycardia (VT)
rate/rhythm ect.

Answer 23

Rate: >100bpm (101 - 250 bpm)
Rhythm: Vent. (R-R): regular and irregular
P-Wave: absent or not associated with the QRS
P-R Interval: unmeasurable (no p-wave)
QRS Complex: >0.12sec (>3 small sq.) wide and bizarre
ST Segment: none
T-wave: none