Brady-arrhythmias

Question 1

What is Bradycardia, and state the different conditions where we can see bradycardia

Answer 1

• Bradycardia is slow heart beats, when an individual has a HR < 60 bpm
• Sinus bradycardia, Sino-atrial blocks, sinus pause (sinus arrest), sick sinus syndrome, AV blocks

Question 2

Sinus bradycardia: def, causes

Answer 2

• SA node fires at least than 60 bpm, normal P waves
• In athletes, not pathologic
• Causes: Drugs (BB, Calcium Channel blocker, Digoxin, morphine), vagal tone, hypothyroidism, hypothermia, ischemic damage, chronic degeneration of the sinus, increased intracranial pressure

Question 3

Sinoatrial block: def

Answer 3

• electrical impulse is delayed or blocked on the way to the atria, thus delaying the atrial beat
• symptoms are usually not severe

Question 4

Sinus pause: def, causes

Answer 4

• Also called sinus arrest -> the SA node failed to generate any impulse
• impulse is not conducted to the atria -> does not generate any P waves
• causes: increased vagal tone, myocarditis, MI, aging, stroke, anti-arrhythmic drugs

Question 5

Sick sinus syndrome, def, D, what is bradycardia-tachycardia syndrome, and its causes

Answer 5

• Sick Sinus Syndrome (SSS): persistent inappropriate bradycardia, sinus arrest, AV conduction disturbances, paroxysms of atrial, supra ventricular, or junctional tachyarrhythmia
• D of SSS: Holter
• Bradycardia-Tachycardia syndrome:a variant of sick sinus syndrome in which slow arrhythmias and fast arrhythmias alternate
• C: ischemic diseases, valve diseases

Question 6

What is the normal electrical pathway of the heart

Answer 6

SA node -> AV node -> bundle of his -> right and left bundle branches -> Purkinje fibers (in the ventricle)

Question 7

How does heart blocks occur, Lev’s disease, RF

Answer 7

• due to damage or fibrosis to the electrical conduction system
• Lev’s disease or Lenegre-lev syndrome: idiopathic cause of heart block, described as progressive cardiac conduction defects
• RF: aging, ischemic heart disease, hereditary (occurs this time in younger patients), myocarditis, cardiomyopayhies

Question 8

What is an AV block, state the different subtypes

Answer 8

• AV block: a delay or blockage of the electrical signal trying to move from the atria to the ventricles

Subtypes:
- 1st degree AV block
- 2nd degree AV block
  type 1 (Mobitz 1 or Wenckebach)
  type 2 (Mobitz 2)
- 3rd degree AV block

Question 9

1st degree AV block: def, ECG, S, T and management

Answer 9

• Signal is delayed, but makes it to the ventricles
• ECG: PR > 200 milliseconds, a constant enlarged PR
• S: not often, well tolerated
• T and management: identifying electrolyte imbalances or causes due to medications, although it usually doesn’t require further treatment

Question 10

2nd degree AV block: Mobitz 1 (Wenckebach): ECG, S

Answer 10

• ECG: PR interval gets progressively longer with each beat until a P-wave is completely blocked
  The P wave that doesn’t get conducted is called the “dropped beat”, and is usually followed by a ventricular escaped beat trying to save the situation
• S: not often, lightheadedness, dizziness, syncope

Question 11

2nd degree AV block: Mobitz 2: ECG, ratio, S

Answer 11

• ECG: PR interval constant, but random beats not conducted
• ratio: for the overall number of beats conducted to not-conducted is 2:1
• S: fatigue, dyspnea, chest pain, syncope. Severity varies

Question 12

3rd degree AV block: def, ECG, S

Answer 12

• Signal is completely blocked when moving from the atria to the ventricles
• complete unpairement between the atrial contraction and ventricular contraction
• ECG: P waves and wide QRS complexes completely uncoordinated
• S: syncope, confusion, dyspnea, severe chest pain, patients are at risk of dying

Question 13

Treatment of AV blocks

Answer 13

• important to find the underlying cause, as it could be an adverse effect from medication, or from an infection
• Atropine: to increase HR
• Transcutaneous pacing: electrical pacing of the heart is done through electrodes placed on the skin
• Permanent pacemaker: device implanted to monitor rhythm, detects delays -> then sends impulses.
  .Pacemakers needed in Mobitz type 2 (not always), and 3rd degree AV blocks

Question 14

Diagnostic methods used for bradycardia

Answer 14

• History
• Physical exam
• Test: ECG, blood test, CXR, holder, loose recorder, electrophysiology, aerometry

Question 15

Management and treatment of: Hemodynamically stable patients

Answer 15

-> continuous ECG indication -> hospital -> atropine and isoproterenol administration -> treat underlying cause -> treat bradycardia if the outcome of the patient will be changed or impacted

Question 16

Management and treatment of: Hemodynamically unstable patients

Answer 16

-> give O2 in hypoxia, severe (cardiac arrest, systole, SBP < 90, pulmonary oedema, end-organ damage) -> immediate treatment (temporary pacing) -> 0,5-1mg atropine + isoprenaline -> set up external cardiac pacing, correct fluid/electrolyte balance as well as acid base imbalance

Question 17

Prognosis

Answer 17

• 40% of patients having a 1st degree AV block will develop a higher degree AV block, so these patients should have regular check-ups
• bradycardia in shock is a poor prognostic sign

Question 18

External cardiac pacing

Answer 18

• Painful, temporary until trans-venous pacing can start
• indicated in patients who received thrombolysis for an AMI, due to high risk of perforation and bleeding from the trans-venous pacing