Lecture 5

Question 1

Hypertrophy (aka enlargement)

Answer 1

-More muscle = more signal on the EKG
-Can involve the ventricles or atria
-Atrial Hypertrophy
-Left ventricular hypertrophy (LVH)→
most common
▪Causes: HTN, valvular dz, Ischemia,
cardiomyopathy, nutritional disorder,
endocrine disorder, drugs/meds (stimulants)

Question 2

Ventricular hypertrophy

Answer 2

• Potentially life-threatening pressure/volume overload

- Increased risk for major CV complications

Question 3

R wave progression

Answer 3

-NORMAL Left ventricle predominance
▪ Right chest leads=prominent S waves in V1, V2
▪ Left chest leads = tall R waves in V4, V5

Question 4

LVH abnormal R wave progression

Answer 4

In LVH, electrical forces tipped even further to left
▪ Abnormally deep S waves in right chest leads (V1, V2)
▪ Abnormally tall R waves seen in left chest leads (V5, V6)

Question 5

Left ventricular hypertrophy

Answer 5

▪Tall R wave in lead aVL > 11 to 13 mm
▪ LAD may also be seen
▪ May develop incomplete or
complete LBBB pattern
▪ Abnl deep S waves in R chest leads (V1, V2)
▪ Abnl tall R waves seen in L chest leads (V5, V6, AVL)
▪ S wave (V1 or V ) + R wave (V5
or V6) > 35 mm

Question 6

cardiac pacemakers

Answer 6

-Monitor & control rate & rhythm
-Temporary pacemakers
-Permanent (Implanted)
pacemakers

Question 7

indications for cardiac pacing - temporary

Answer 7

• Slow HR caused by MI
• Cardiac surgery
• Med Overdose
• Emergencies

Question 8

indications for cardiac pacing - permanent

Answer 8

• Sick Sinus Syndrome
• Symptomatic brady- arrhythmias
• High Grade Heart Block
• Atrial Fibrillation/Flutter with excessively slow ventricular response

Question 9

cardiac pacemakers: fixed vs demand

Answer 9

Two modes: fixed rate vs. demand pacemakers

1) Fixed pacemaker
▪ Fires at a specific preset rate regardless of patient’s own heart rate
▪ Only pacing mechanism

2) Demand pacemakers (rate-responsive)
▪ Fires only when patient’s heart rate fall below a preset value
▪ Sensing + pacing mechanisms

Question 10

Pacemaker EKG patterns

Answer 10

• Atrial pacemaker produces a spike followed by a P wave

- Ventricular pacemaker produces a sharp vertical spike followed by QRS complex

Question 11

problems with pacemakers

Answer 11

-Failure to capture 
▪ Occurs when a pacing stimulus is generated,
but fails to trigger myocardial depolarization ▪ Causes:
▪ Oversensing
▪ pacing lead problems (dislodgement or
fracture)
▪ battery or component failure 
▪ electromagnetic interference

-Failure to sense
▪ Undersensing: fails to recognize spontaneous myocardial depolarization
▪ generation of unnecessary pacing spikes
▪ Oversensing: Inappropriate sensing of extraneous
electrical signals (mostly skeletal mm activity)
▪ signals are interpreted by pacemaker as intrinsic activity & as a result pacemaker does not fire - large P or T waves, skeletal muscle activity or lead contact problems
▪ absent pacemaker spikes & ventricular asystole
▪ Undersensing
▪ Oversensing

Question 12

pacemaker vs AICD

Answer 12

-Heart rate too slow→ Pacemaker
▪ High Grade Heart Blocks
▪ Symptomatic Brady- arrhythmias

-Heart rate too fast→ Automatic Implantable Cardioverter Defibrillator (AICD)
▪ Tachy-arrhythmias
▪ V-tach, V-fib