ECG types

normal sinus rhythm

sinus tachycardia

sinus bradycardia

atrial flutter

• No P waves instead flutter waves (sawtooth pattern) are formed at rate of 250-350bpm

• Only some impulses conduct through the AV node, usually every other impulse

  • Heart rate: 75bpm

  • Rhythm: regular

  • P waves: flutter/sawtooth appearance

  • PR interval: none/unable

  • QRS complex: narrow 0.06 seconds

atrial fibrillation

• No organised atrial depolarisation, so no normal P waves (impulses are not originating from the sinus node)

• Atrial activity is chaotic resulting in an irregularly irregular rate, R-R interval is irregular 

• Red flag for blood clots and strokes

  • Heart rate: 100bpm

    • If above classified as fast AF

  • Rhythm: irregular 

  • P waves: unclear, many

  • PR interval: unable

  • QRS complex: narrow at 0.08 seconds

supraventricular tachycardia

• Can’t see P waves

• Narrow QRS

• Continues until broken 

  • Heart rate: 190bpm

  • Rhythm: regular

  • P waves: unknown (rhythm too fast)

  • PR interval: unknown

  • QRS complex: narrow 0.06 seconds

paraoxysmal SVT

• Heart rate suddenly speeds up

• Premature atrial contraction

• P waves are lost

• Narrow QRS

junctional rhythm

• Pacemaker in the AV junction of bundle of HIS region 

• Electrical impulse travels backwards to depolarise atria so if p wave is seen it is inverted

• Normal rate = 40-60bpm

  • >60 = accelerated junctional

  • >100 = junctional tachycardia

  • <40 = junctional escape

• Heart rate: 40-60bpm

• Rhythm: regular

• P waves: inverted or missing

• PR interval: unknown

• QRS complex: narrow <0.12 seconds

sinus rhythm with 1st degree AV block

• Prolonged conduction delay in the AV node or Bundle of HIS

• PR interval = >20 seconds

• Usually asymptomatic

  • Heart rate: 60

  • Rhythm: regular

  • P waves: present 

  • PR interval: 0.36 seconds

  • QRS complex: 0.08 seconds (narrow)

2nd degree type I AV block

• Mobitz 1/wenckebach

• Irregular

• More Ps than QRSs

• PRI progressive lengthens then drops QRS

• Heart rate: 60bpm

• Rhythm: irregular

• P waves: present, more than QRS

• PR interval: progressively lengthens then drops QRS

• QRS complex: narrow

2nd degree type II AV block

• Mobitz 2

• Regular

• More Ps than QRSs

• Consistent PR interval

• Typically very bradycardic 

• Heart rate: 38bpm

• Rhythm: regular

• P waves: present, more than QRS

• PR interval: consistent

• QRS complex: narrow

3rd degree AV block

• There is complete block of conduction in AV junction

• Atria and ventricles form impulses independently of each other

• Without impulses the ventricles intrinsic pacemaker kicks in at around 30-45bpm

• Can result in no pulse eventually

• Heart rate: 38bpm

• Rhythm: regular QRSs and P waves but no relationship between the two

• P waves: present

• PR interval: variable 

• QRS complex: dependent, wide in this example

idioventricular escape rhythm

• Causes: heart blocks, medication side effects, hyperkalemia 

• Rhythm originates in ventricles

• Wide QRS complexes >0.12 seconds

• Heart rate: 25bpm

• Rhythm: regular

• P waves: absent

• PR interval: absent 

• QRS complex: wide, 0.16 seconds

accelerated idioventricular rhythm

has a faster rate

ventricular tachycardia

• Impulse originating in ventricles

• No P waves, wide QRS

• Re-entrant pathway looping in a ventricle

• “Normal” rate = >100bpm

• <100bpm = accelerated idioventricular rhythm or ventricular escape

ventricular fibrillation

• Completely abnormal

• No rhythm

• Coarse or fine:

sinus tachycardia causes

• exercise, pain, anxiety

• shock (hypovolaemic, septic, cardiogenic)

• pulmonary embolism

• anaphylaxis

• fever/infection

• heart failure

• drugs (salbutamol, stimulants)

sinus bradycardia causes

• inferior myocardial infarction

• increased vagal tone

• drugs (beta-blockers, digoxin)

• hypothermia

atrial fibrillation causes

• hypertension

• ischaemic heart disease

• mitral valve disease

• hyperthyroidism

• infection/sepsis

ventricular fibrillation

• myocardial infarction

• severe electrolyte disturbance

• cardiomyopathy

• cardiac arrest