Bradycardia

Under the guidance of Dr Murali Mohan NT

PROF & HOD, EMD By Dr. Soumya Nath Maiti (IMO)

Overview

Definition

Bradycardia - causes

Criteria for symptomatic bradycardia

Signs and Symptoms

The Bradycardia Algorithm

Treatment Sequence

Definition

Bradycardia – Bradycardia from the Greek  (bradys "slow", and kardia, "heart"), is the resting heart rate of under 60 beats per minute (BPM),

although it is seldom symptomatic until the rate drops below 50 BPM.

Bradycardia - causes

BRADYCARDIA MAY HAVE MULTIPLE CAUSES .

Physiological - A well trained athlete may have a heart rare in the range of 40- 50 beats / min. This are called as functional or relative bradycardia. It occurs as a sport adaptation and helps prevent tachycardia during training.

Bradycardia - causes

Pathological – Divided into cardiac and non-cardiac causesNon-cardiac causes are usually secondary Recreational drug use or abuse.  Metabolic or endocrine disorders, especially

 thyroid disorders. An electrolyte imbalance.  Neurological factors Situational factors such as prolonged bed

rest Autoimmunity. 

Bradycardia - causes

Cardiac causes Acute or chronic ischemic heart disease Vascular heart disease, Valvular heart disease, Degenerative primary electrical disease.

Ultimately, the causes act by three mechanisms: Depressed automaticity of the heart, Conduction block & escape pacemakers and rhythms.

Bradycardia - causes

In general, two types of problems result in bradycardias: disorders of  SA node, and disorders of the AV node.

With sinus node dysfunction (sometimes called sick sinus syndrome), there may be disordered automaticity or impaired conduction of the impulse from the sinus node into the surrounding atrial tissue

Bradycardia - causes

Atrioventricular conduction disturbances may result from impaired conduction in the AV node, or anywhere below it, such as in the Bundle of His.

The clinical relevance pertaining to AV blocks is greater than that of sinoatrial blocks

Relative Bradycardia

The term relative bradycardia is used in explaining a heart rate that, although not actually below 60 BPM, is still considered too slow for the individual's current medical condition.

For example A heart rate of 70 beats/min is too slow for a patient in cardiogenic or septic shock

Criteria for symptomatic bradycardia

A symptomatic bradycardia exists only when three criteria are present

1. The hart rate is slow.2. The patient has symptoms. 3. The symptoms are due to slow

heart rate.

Symptoms

A. Chest DiscomfortB. Shortness of breathC. Decreased level of consciousness, D. Weakness & fatigueE. Light headedness & dizzinessF. Presyncope or syncope

Signs

Hypotension, orthostatic hypotension Pulmonary congestion on Xray &

auscultation Features of Frank congestive heart

failure Features of pulmonary oedema

The Bradycardia Algorithm

The bradycardia algorithm outlines the steps for assessment and management of a patient presenting with symptomatic bradycardia

The primary point in the bradycardia algorithm is determination of adequate perfusion.

Identification of Bradycardia

Present by definition

ie Heart rate < 50/ min

Inadequate for the patients condition

BLS and ACLS Survey

A. Maintain patent airwayB. Assist breathing as

needed. C. Monitor vitals, obtain

and review a 12 lead ECG. Establish IV access

D. Conduct a problem focused history and physical examination . Search for contributing factors.

Are sings & symptoms caused by Bradycardia ?

Look for adverse signs and symptoms of bradycardia. Sometimes the

symptom is not due to bradycardia. Ex – Hypotension associated with Bradycardia may be due to myocardial dysfunction rather than braycardia.

Adequate Perfusion

Decision should be taken if the patient has adequate or poor perfusion

1. If the patient has

adequate perfusion, observe and monitor (Box 4).

2. If the Patient has poor perfusion Proceed to Treatment sequence. (Box 5 )

Treatment Sequence

1 •Atropine 0.5 mg iv •May repeat dose upto 3 mg

2• If atropine

is ineffective

3 • Transcutaneous pacing or• Dopamine 2 – 10 mcg/kg per min. or• Epinephrine 2 – 10 mcg / min

Treatment sequence: Atropine

In the absence of immediately reversible causes, atropine remains the first-line drug for acute symptomatic Bradycardia.

For bradycardia, give atropine 0.5 mg IV every 3 to 5 mins to a total dose of 0.04mg/kg.

Treatment sequence: Atropine

Atropine should be used cautiously in the presence of MI. An atropine induced increase in heart rate may worsen ischemia or increase infract size.

Atropine can not be relied upon in case of Mobitz type II 2nd or 3rd degree AV block or in patients with 3rd degree AV block with a new wide QRS complex.

Treatment sequence: Pacing

Immediate pacing should be considered in critical patients when IV access is unavailable or patient is unresponsive to Atropine.

Following initiation of pacing, confirm electrical and mechanical capture. Reassess the patient for symptom improvement and Haemodynamic stability.

Pacing Technique2. Set the demand rate to 60/min. The rate can be adjusted.

3. Set the current output 2 mA above the dose at which consistent capture is observed.

Treatment sequence: Epinephrine & Dopamine

Both epinephrine and dopamine are vasoconstrictors as well as chronotropes, patients intravascular volume status must be assessed to avoid hypovolemia.

Begin epinephrine infusion at a dose of 2-10mcg/min and titrate to response.

Begin dopamine infusion at 2-10mcg/min and titrate to response. Lower dose of dopamine has a more selective effect on inotropy and heart rate.

Next actions

Prepare the patient for transvenous

pacing

Treat the contributing

factors.

Consider expert consultation

Referances

AHA SELS manual 2013

Harrison’s principal of internal medicine 17th episode