Updated: 6/28/2020

Atrioventricular (AV) Heart Block

0%
Topic
Review Topic
0
0
N/A
N/A
Questions
10 10
0
0
0%
0%
Evidence
7 7
0
0
Snapshot
  • A 20-year-old man presents to his primary care physician for an annual exam. He is currently feeling well but has some concerns since he occasionally has palpitations. Medical history is unremarkable and he takes a daily multivitamin. He denies any alcohol or smoking history. Family history is significant for his paternal grandfather expiring from a fatal arrhythmia. He is a college student and part of the school's basketball team, which he continued since he was a student in high school. He says that his caffeine intake has increased in these past few weeks due to upcoming final examinations. He is requesting an electrocardiogram (ECG) to ensure his heart is healthy since this worry is interfering with his school work. An ECG demonstrates a PR interval of 0.25 sec and is otherwise unremarkable. (First-degree heart block)
Introduction
  • Clinical definition
    • an impairment of the electrical transmission from the atria to the ventricles
  • Etiology
    • idiopathic (most common)
      • e.g., fibrosis and sclerosis of the conduction system
    • ischemic heart disease (2nd most common)
    • ↑ vagal tone
    • familial causes
    • iatrogenic
      • medications
        • e.g., β-blockers, calcium channel blockers, adenosine, digoxin, and amiodarone
      • cardiac procedures
        • e.g., cardiac surgery and transcatheter aortic valve implantation
  • Differential
    • sick sinus syndrome
      • presents with bradycardia, tachycardia, or alternating bradycardia-tachycardia 
Atrioventricular (AV) Block
 
AV Blocks
Types
Electrocardiogram Findings
Treatment   Comments
First degree AV block
  • ↑ PR interval (> 0.2 secs)
  • 1:1 ratio of P waves and QRS complexes
  • No treatment is required unless other ECG changes (prolonged QRS)  
  • Typically seen in young patients with a ↑ vagal tone
  • Well-trained athletes
Second degree AV block (Mobitz type I) 
  • Progressive ↑ PR interval until a P wave is not followed by a QRS complex (Wenckebach phenomenon)   
    • the sequence then repeats
    • QRS complex is narrow
  • Treatment is unnecessary unless the patient is symptomatic 
    • use atropine or a temporary pacemaker in symptomatic cases
  • Patients are typically asymptomatic
  • Can be seen in patients with
    • drug intoxication (e.g., β-blockers and digitalis) 
    • ↑ vagal tone
Second degree AV block (Mobitz type II) 
  • Fixed PR intervals with occasional dropped QRS complexes  
    • QRS complex is typically wide
  • Permanent pacemaker 
  • May progress to a third-degree heart block
Third degree (complete) AV block
  • Atria and ventricles depolarize independently  
    • P waves and QRS complexes are not rhythmically synchronized
 
  • Atropine 
  • Pacing 
  • Permanent pacemaker unless the cause is reversible (such as medications)
 
  • Can be a complication of Lyme disease
 

 

 

Please rate topic.

Average 4.8 of 11 Ratings

Questions (10)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(M2.CV.15.4172) A 54-year-old man presents to the emergency room with a right humerus fracture. Although he denies chest pain, he undergoes an electrocardiogram (EKG), which is shown in Figure A. Which of the following structures is most likely to be dysfunctional in this patient? Review Topic | Tested Concept

QID: 106985
FIGURES:
1

His-Purkinje system

13%

(3/23)

2

Sinoatrial node

9%

(2/23)

3

Atrioventricular node

74%

(17/23)

4

Mitral valve

0%

(0/23)

5

Tricuspid valve

0%

(0/23)

L 2 E

Select Answer to see Preferred Response

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Evidences (7)
Topic COMMENTS (6)
Private Note