Heart blocks: Pathology review
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Heart blocks: Pathology review
Prerequisite basic sciences
Prerequisite basic sciences
Supraventricular arrhythmias: Pathology review
Ventricular arrhythmias: Pathology review
Prerequisite basic sciences
Chest X-ray interpretation: Clinical sciences
Prerequisite basic sciences
ECG axis
ECG basics
ECG cardiac hypertrophy and enlargement
ECG cardiac infarction and ischemia
ECG intervals
ECG normal sinus rhythm
ECG QRS transition
ECG rate and rhythm
Coronary artery disease: Pathology review
Electrolyte disturbances: Pathology review
Heart blocks: Pathology review
Supraventricular arrhythmias: Pathology review
Ventricular arrhythmias: Pathology review
Prerequisite basic sciences
Anatomy clinical correlates: Anterior and posterior abdominal wall
Anatomy clinical correlates: Inguinal region
Anatomy clinical correlates: Other abdominal organs
Anatomy clinical correlates: Peritoneum and diaphragm
Anatomy clinical correlates: Viscera of the gastrointestinal tract
Appendicitis: Pathology review
Diverticular disease: Pathology review
Gallbladder disorders: Pathology review
GERD, peptic ulcers, gastritis, and stomach cancer: Pathology review
Inflammatory bowel disease: Pathology review
Pancreatitis: Pathology review
Anatomy clinical correlates: Anterior blood supply to the brain
Anatomy clinical correlates: Cerebellum and brainstem
Anatomy clinical correlates: Cerebral hemispheres
Anatomy clinical correlates: Posterior blood supply to the brain
Amnesia, dissociative disorders and delirium: Pathology review
Central nervous system infections: Pathology review
Cerebral vascular disease: Pathology review
Dementia: Pathology review
Drug misuse, intoxication and withdrawal: Alcohol: Pathology review
Drug misuse, intoxication and withdrawal: Hallucinogens: Pathology review
Drug misuse, intoxication and withdrawal: Other depressants: Pathology review
Drug misuse, intoxication and withdrawal: Stimulants: Pathology review
Mood disorders: Pathology review
Seizures: Pathology review
Traumatic brain injury: Pathology review
Anatomy clinical correlates: Breast
Anatomy clinical correlates: Heart
Anatomy clinical correlates: Mediastinum
Anatomy clinical correlates: Pleura and lungs
Anatomy clinical correlates: Thoracic wall
Aortic dissections and aneurysms: Pathology review
Coronary artery disease: Pathology review
Deep vein thrombosis and pulmonary embolism: Pathology review
GERD, peptic ulcers, gastritis, and stomach cancer: Pathology review
Pleural effusion, pneumothorax, hemothorax and atelectasis: Pathology review
Anatomy clinical correlates: Viscera of the gastrointestinal tract
Gastrointestinal bleeding: Pathology review
Anatomy clinical correlates: Bones, fascia and muscles of the neck
Anatomy clinical correlates: Skull, face and scalp
Anatomy clinical correlates: Temporal regions, oral cavity and nose
Anatomy clinical correlates: Trigeminal nerve (CN V)
Anatomy clinical correlates: Vessels, nerves and lymphatics of the neck
Headaches: Pathology review
Anatomy clinical correlates: Anterior blood supply to the brain
Anatomy clinical correlates: Cerebellum and brainstem
Anatomy clinical correlates: Cerebral hemispheres
Anatomy clinical correlates: Posterior blood supply to the brain
Cerebral vascular disease: Pathology review
Anatomy clinical correlates: Female pelvis and perineum
Cervical cancer: Pathology review
Complications during pregnancy: Pathology review
Ovarian cysts and tumors: Pathology review
Sexually transmitted infections: Vaginitis and cervicitis: Pathology review
Urinary tract infections: Pathology review
Uterine disorders: Pathology review
Vaginal and vulvar disorders: Pathology review
Anatomy clinical correlates: Heart
Anatomy clinical correlates: Mediastinum
Anatomy clinical correlates: Pleura and lungs
Anatomy clinical correlates: Thoracic wall
Apnea, hypoventilation and pulmonary hypertension: Pathology review
Deep vein thrombosis and pulmonary embolism: Pathology review
Heart failure: Pathology review
Lung cancer and mesothelioma: Pathology review
Obstructive lung diseases: Pathology review
Pleural effusion, pneumothorax, hemothorax and atelectasis: Pathology review
Pneumonia: Pathology review
Restrictive lung diseases: Pathology review
Tuberculosis: Pathology review
Drug misuse, intoxication and withdrawal: Alcohol: Pathology review
Drug misuse, intoxication and withdrawal: Hallucinogens: Pathology review
Drug misuse, intoxication and withdrawal: Other depressants: Pathology review
Drug misuse, intoxication and withdrawal: Stimulants: Pathology review
Environmental and chemical toxicities: Pathology review
Medication overdoses and toxicities: Pathology review
Prerequisite basic sciences
Shock: Pathology review
Prerequisite basic sciences
Anatomy clinical correlates: Arm, elbow and forearm
Anatomy clinical correlates: Axilla
Anatomy clinical correlates: Bones, fascia and muscles of the neck
Anatomy clinical correlates: Cerebral hemispheres
Anatomy clinical correlates: Clavicle and shoulder
Anatomy clinical correlates: Eye
Anatomy clinical correlates: Female pelvis and perineum
Anatomy clinical correlates: Heart
Anatomy clinical correlates: Hip, gluteal region and thigh
Anatomy clinical correlates: Male pelvis and perineum
Anatomy clinical correlates: Mediastinum
Anatomy clinical correlates: Pleura and lungs
Anatomy clinical correlates: Skull, face and scalp
Anatomy clinical correlates: Spinal cord pathways
Anatomy clinical correlates: Thoracic wall
Anatomy clinical correlates: Vertebral canal
Anatomy clinical correlates: Vessels, nerves and lymphatics of the neck
Anatomy clinical correlates: Viscera of the neck
Anatomy clinical correlates: Wrist and hand
Eye conditions: Inflammation, infections and trauma: Pathology review
Spinal cord disorders: Pathology review
Pleural effusion, pneumothorax, hemothorax and atelectasis: Pathology review
Traumatic brain injury: Pathology review
Assessments
Heart blocks: Pathology review
USMLE® Step 1 questions
0 / 3 complete
Questions
USMLE® Step 1 style questions USMLE
of complete
Reproduced from: Wikimedia Commons
Which of the following is the most likely cause of this patient’s symptoms?
Transcript
Content Reviewers
Mikey is a 22 year old male college student from Vermont who was sent to the emergency department after passing out.
His vital signs show a heart rate of 40 beats per minute and a blood pressure of 90/50. On examination, there is an erythematous circular rash with central clearing.
His friends mention they recently went on a hiking trip. His ECG is as follows.
Natasha is a 60 year old female with chronic hypertension, diabetes, and peripheral vascular disease who comes to the emergency room complaining of sudden-onset, squeezing retrosternal chest pain accompanied by shortness of breath and sweating.
Her ECG is as follows. On laboratory evaluation, her troponin levels are significantly elevated.
Alright, so the normal electrical activity of the heart starts in the sinoatrial or SA node located near the opening of the superior vena cava into the right atrium.
Electrical activity is then conducted through the atrium to the atrioventricular, or AV node, after which it goes through the Bundle of His, then the right and left branches of the Bundle, and finally through the Purkinje fibers which deliver the current to the right and left ventricles.
Now, normally there is delay in conduction at the AV node and the Bundle of His, which gives some time for ventricular filling before the ventricle contracts.
A “heart block”, or AV block, occurs when conduction is delayed for too long at the AV node or the bundle of His. Also, electrical activity may be blocked at the level of the bundle branches, which are called bundle branch blocks.
Sources
- "Pathophysiology of Heart Disease" Wolters Kluwer Health (2015)
- "Chou's Electrocardiography in Clinical Practice" Saunders (2008)
- "Clinical electrophysiology of atrioventricular block" Cardiol Clin (1983)
- "Left Bundle Branch Block: Current and Future Perspectives" Circ Arrhythm Electrophysiol (2020)
- "2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society" J Am Coll Cardiol (2019)
- "Bradycardias and atrioventricular conduction block" BMJ. 2002 (2002)
- "Observations on second degree atrioventricular block, including new criteria for the differential diagnosis between type I and type II block" The American Journal of Cardiology (1972)
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