Lecture 12- Rate and Sinus Rhythms

how to determine rate

• recall that EKG paper should pass at a rate of 25mm/sec

• 300 large boxes /minute

• each small box is 0.04sec; large box is 0.2sec

3 methods to determine rate (with regular rhythms)

1) 300, 150, 100, 75, 60, 50

2) 300 divided by number of large boxes btwn cycles

3) 1500 divided by number of small boxes btwn cycles

rates for irregular or slow rhythms

• 6 second strip x10

• 10 sec strip x 6

• (#Rs in 6 sec strip)

300, 150, 100, 75, 60, 50 method

• find R wave most closely lies on dark line

• recite numbers on each large box until get to the next R wave

• doe NOT work foe irregular rhythms

300/large boxes vs 1500/small boxes

• 300 divided by number of large boxes btwn R-R interval

• 1500 divided by number of small boxes btwn R-R

  • more precise

ANS and HR variation

• vagus nerve provides parasympathetic input to SA and AV nodes

• sympathetic stimulation:

  • reduces vagal tone

  • increases HR
    seek on EKG as sinus tachy

• parasympathetic stimulation

  • increase vagal tone

  • slows heart rate, esp at rest

possible EKG presentation for increased vagal tone

• sinus brady

• sinus pauses

• AV block

characteristics of normal sinus ryhythm

• P wave: upright- indicates SA node is functioning properly

• PR interval: <0.20 sec- normal conduction from SA node through AV node

• QRS complex: narrow (<0.12sec)- impulse originates above bundle of his (supreventricular)

• rate: 60-100bpm

• rhythm: regular- consistent spacing btwn R waves

arrhythmia

any rhythm other than normal sinus

sinus bradycardia

• P wave: upright- normal sinus origin

• PR interval: 0.12-0.20 sec- normal conduction SA node-AV node

• QRS complex: narrow (<0.12 sec)- normal impulse origin

• RATE: <60 bpm- slower than normal resting HR

• rhythm: normal

when might bradycardia be normal/non concerning

• well trained athletes or during sleep

• can also occur with meds or vagal stimulation

  • beta blockers

  • digoxin

sinus tachycardia

• P wave: upright- normal sinus origin

• PR interval: 0.12-0.20 sec- normal conduction SA node-AV node

• QRS complex: narrow (<0.12 sec)- normal impulse origin

• RATE: >100 bpm- faster than normal resting HR

• rhythm: normal

when might tachycardia be normal/non concerning

• normal physiological response to exercise, pain, fever, anxiety, o rhypovolemia

• may also occur secondary to stimulants, anemia, or heart failure

sinus arrhythmia

• P wave: upright- normal sinus origin

• PR interval: 0.12-0.20 sec- normal conduction SA node-AV node

• QRS complex: narrow (<0.12 sec)- normal impulse origin

• rate: usually 60-100bpm- normal; may be slightly slower with respiratory variation

• RHYTHM: irregular- R-R intervals vary, often INCREASING with inspiration and decreasing with expiration (respiratory sinus arrhythmia)

when might sinus arrhythmia be normal/non concerning

• common in young, healthy individuals

• considered normal physiological variation due to vagal tone changes with breathing