Unstable Bradycardia Part 2

Causes of Bradycardia

• Acute myocardial infarction 

• Drugs:  blockers, digoxin, Amiodarone 

• Increased intracranial pressure 

• Sick sinus syndrome 

• Hypothermia 

• Hypothyroidism

Common Bradycardic Rhythms

• Sinus bradycardia

• NSR with sinus arrest

• 2nd degree heart block type II

• 3rd degree heart block

Sinus Bradycardia

Note:  

Rate: The atrial and ventricular rates are equal; the heart rate is less than 60 beats per minute

Rhythm: the rhythm is regular

P Wave: The P waves are uniform. There is one P wave in front of every QRS complex.

PRI: 0.12 - 0.20 seconds and constant. 

QRS: less than 0.12 seconds

Sinus Arrest

Note:

Rate: The rate varies according to the number and length of pauses

Rhythm: The rhythm is regular except during pauses

P Wave: The P waves are uniform. There is one P wave in front of every QRS complex.

PRI: 0.12 - 0.20 seconds and constant.

QRS: less than 0.12 seconds

Second Degree Heart Block Type II

Note:

Rate: Atrial rate is typically normal. Because many of the atrial impulses are blocked, the ventricular rate will be in the bradycardia range, usually with a 2 - 1, 3 - 1, or a 4 - 1 conduction rate.

Rhythm: If the conduction rate is consistent, the R - R interval will be constant, and the rhythm will be regular. If the conduction ratio varies, the R - R will be irregular.

P Wave: Upright and uniform. There are more P waves than QRS complexes

PRI: Will be constant on conducted beats. 

QRS: less than 0.12 seconds

Third Degree Heart Block

Notes:

Rate: The atrial rate is typically normal. The ventricular rate will be slower. If a junctional focus is controlling the ventricles, the rate will be 40 - 60. If the focus is ventricular, the rate will be 20 - 40.

Rhythm: Since the atrial and ventricular foci are firing regularly, the P - P and the R - R intervals will be regular.

P Wave: Upright and uniform. There are more P waves than QRS complexes

PRI: There is no PRI, because the block at the AV node is complete. There is no association between the P waves and the QRS complexes.

QRS: If the focus is junctional, less than 0.12 seconds. If the focus is ventricular, the QRS will be > 0.12.

Types of Bradycardia

• Absolute Bradycardia: Defines bradycardia by heart rate (below 60)

• Relative Bradycardia: Defines bradycardia by symptoms (i.e.. hypotension with HR of 65)

Symptomatic Bradycardia

• Symptomatic implies that an arrhythmia is causing symptoms, such as palpitations, lightheadedness, or dyspnea, but the patient is stable and not in imminent danger. 

• In such cases more time is available to decide on the most appropriate intervention

Unstable Bradycardia

• Refers to a condition in which vital organ function is acutely impaired or cardiac arrest is ongoing or imminent. 

• When an arrhythmia causes a patient to be unstable, immediate intervention is indicated

Serious signs and symptoms

• Chest pain

• Syncope

• Shortness of breath

• Cold and clammy skin

• Decreased level of consciousness

• Hypotension

• Pulmonary congestion 

• Congestive Heart Failure 

• Acute Myocardial Infarction

Primary Survey

• Assess ABCs

• Breathing-secure noninvasive airway

• Call for monitor/defibrillator

Note:

Because hypoxemia is a common cause of bradycardia, initial evaluation of any patient with bradycardia should focus on signs of increased work of breathing (tachypnea, intercostal retractions, suprasternal retractions, paradoxical abdominal breathing) and oxyhemoglobin saturation as determined by pulse oximetry

Secondary Survey

• Oxygen

• IV access-monitor-fluids

• Vital signs, pulse oximeter, BP

• Obtain 12 lead

• Differential diagnosis