CV Cardio Pathophysiology

Question 1

Right Axis Deviation

Answer 1

> 100 Degrees
Lower Right Quadrant
Pathogenesis: Pulmonic Stenosis

Question 2

Left Axis Deviation

Answer 2

< -30 Degrees
Upper left quadrant
Pathogenesis: Aortic Valve Stenosis, LVH, Essential HTN, Pregnancy

Question 3

First Degree AV Heart Block

Answer 3

Consistent, Prolonged P-R interval (> 0.2 sec)

All impulses get through.

Question 4

Second Degree AV Heart Block

Answer 4

2 P waves per 1 QRS wave
2:1 Pattern of AV conduction
Some P-waves from AV impulse gets through to the ventricles. The PR intervals get longer each cycle (drop a QRS)

Question 5

Tertiary (Complete) AV Heart Block

Answer 5

Features a random (variable) pattern of P: QRS [4:3:2…]
-Ventricles start their own “slower rhythm”
-SA node’s transmission does not get to the ventricles
-SA node still DRIVES atrial function though
Treatment: Bypass the AV node with a pacemaker

Question 6

Describe what occurs in a sinus block?

Answer 6

SA node has prolonged periods of no firing.

SA node would relay in a few P-waves, then stop for a moment, then continue firing.

Question 7

What is sinus arrhythmia?

Answer 7

The irregular firing in the SA node that may lead to the formation of numerous P-waves.

Question 8

What occurs in AV nodal reentry?

Answer 8

AV firing can go back into the atria to wreak havoc.

Can cause potential “circus rhythms” in the atria.

Question 9

What occurs in bundle branch blocks?

Answer 9

Left or right bundle branch blocks can cause significant delay in ventricular depolarization and subsequent ventricular contraction of the left or right heart, depending on the block. Contraction from apex to base may not synchronize.

Question 10

What occurs in premature ventricular contractions?

Answer 10

PVCs have ventricles fire on their own.
Wide QRS >0.12 seconds
No P-waves are present

Question 11

What occurs during Atrial Fibrillation? What are some features in the ECG?

Answer 11

The AV node is disrupted leading to ectopic (abnormal outside) pacemakers in the atria.
*There are NO P-WAVES!
Instead, F-waves (noise) precedes QRS, which is an indication of uncoordinated depolarization.
PR interval is absent and rhythm is irregular.

Question 12

What occurs in an atrial flutter? Name some features on the ECG.

Answer 12

Atria go crazy due to the lack of SA nodal control. On the ECG, expect to see multiple “Saw-tooth P-waves”.

Question 13

What is an AV Junctional Rhythm?

Answer 13

Where the AV node does not fire at the same rhythm as the SA node to relay conductance to the Bundles
Fires at 40 bpm, instead in order to restore some hemodynamic stability.

Question 14

What occurs in a Ventricular Escape Rhythm?

Answer 14

Where the ventricles control their rhythm in order to maintain “hemodynamic stability”. (20-30 bpm)
Last resort, perhaps from a complete heart block, where no conductance reaches the ventricles.

Question 15

What are the ECG features of Junctional Escape Rhythm? What caused this to occur?

Answer 15

Irregular Rhythm marked with MISSING P-waves.
It is caused by a SA Nodal Arrest, where no depolarization of the atria occurs in the conduction path. Instead, the AV node picks controls the QRS-wave.

Question 16

Describe the events that occur in a Circus Rhythm.

Answer 16

1. Instead of in a normal impulse where the AP is unidirectional and prevented by an “effective refractory period”, a REENTRANT loop forms.
2. Damaged myocytes provide a path for “retrograde conduction”. This forms a self-sustaining “Ectopic pacemaker”.
3. The reentry circuit conducts FAST impulses and may take depolarize adjacent cardiac tissue.
   * This is the cause of atrial and ventricular arrhythmia*

Question 17

What occurs in the normal sequence of cardiac impulse?

Answer 17

1. Impulse travels down excitable tissue in one direction.
2. Myocytes that undergo depolarization are in absolute refraction.
3. Time and voltage dependence of Refractory Period prevents retrograde conduction.

Question 18

What are the ECG features and possible causes of Ventricular Fibrillation?

Answer 18

Presence of multiple QRS signals at a very FAST rate.
Heart doesn’t pump blood (Cardiac Output = 0; Very Serious)
Can be caused by a Ventricular Escape (irregular) Rhythm
Tx: Defibrillator Paddles to reset sinus rhythm.

Question 19

What occurs during Monomorphic Ventricular Tachycardia. Describe what shows on the ECG.

Answer 19

Myocytic transmission is SLOWER.
Scarred myocardium can trigger 3 or more consecutive PVCs.
Hidden P-waves are not 1:1 so NOT SINUS!
Multiple WIDENED-QRS complexes occurs at FAST but REGULAR rhythm.
Not enough time for ventricular filling. Can lead to Cardiac Arrest.

Question 20

What occurs in a Bundle Branch Block and how does it show on the ECG?

Answer 20

One of the Bundle Branches is disrupted causing the conduction being relayed from the unaffected side to the healthy side. 2 Fused R-waves make a WIDE QRS
RBBB: Rabbit Ears
LBBB: Notched R; sharp down S-wave.

Question 21

What happens in Premature Ventricular Contractions? How does this present on the ECG?

Answer 21

“Rogue” ventricular contractions occur from a problematic tissue, such as ischemic tissue. This features 1 or more WIDE QRS-complexes and “no distinguishable” P-waves. This can be caused by an ectopic pacemaker.

Question 22

What is “Supraventricular Tachycardia” and how might it present in an ECG?

Answer 22

This is caused by some disruption above the ventricles (such as in AV node or His Bundle) that DRIVES the tachycardia.
Examples include A-fib or A-flutter.
*It features NARROW QRS in the ECG.

Question 23

What are the ECG manifestations of Hypocalcemia?

Answer 23

PROLONGED QT interval. This imbalance has a direct effect on the channels due to the higher amount of extracellular Calcium.
Channels stay open for a longer time (allosteric effect).
The time before repolarization starts is prolonged.

Question 24

What should be expected in the ECG from Hypercalcemia?

Answer 24

NARROW QT interval because the channels become more irritable (excitable even in refraction due to A LOT of Ca+ outside the myocyte -> Quick Depolarization)

Question 25

What does the ECG show in a patient with Hyperkalemia?

Answer 25

Features TENTED (or T-peaked) T-WAVES due to a Repolarization anomaly (repolarization takes longer)

• No P-waves precede QRS-complexes.
• ALL HEART REGIONS are affected.

Question 26

What can we expect in an ECG with Hypokalemia? What is the significance of this

Answer 26

Low K+: Inverted and FLATTENED T-wave; U-wave in precordial (V-leads); long QT interval.
Myocardium is hyper excitable and can develop into re-entrant arrhythmias.

Question 27

What are the indications of a Myocardial Infarction in an ECG?

Answer 27

1. T-wave inversion - repolarization is disrupted in Leads 2,3
2. New Q waves appear - signal irreversible Myocardial Death in Leads 2 and 3
   OR…
3. ST elevation (STEMI) in Leads 2 and AVF