Supraventricular arrhythmias: Pathology review

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Supraventricular arrhythmias: Pathology review

Cardiovascular system

Vascular disorders

Arterial disease

Angina pectoris

Stable angina

Unstable angina

Myocardial infarction

Prinzmetal angina

Coronary steal syndrome

Peripheral artery disease

Subclavian steal syndrome

Aneurysms

Aortic dissection

Vasculitis

Behcet's disease

Kawasaki disease

Hypertension

Hypertensive emergency

Renal artery stenosis

Coarctation of the aorta

Cushing syndrome

Conn syndrome

Pheochromocytoma

Polycystic kidney disease

Hypotension

Orthostatic hypotension

Abetalipoproteinemia

Familial hypercholesterolemia

Hypertriglyceridemia

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Chronic venous insufficiency

Thrombophlebitis

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Lymphedema

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Shock

Vascular tumors

Human herpesvirus 8 (Kaposi sarcoma)

Angiosarcomas

Congenital heart defects

Truncus arteriosus

Transposition of the great vessels

Total anomalous pulmonary venous return

Tetralogy of Fallot

Hypoplastic left heart syndrome

Patent ductus arteriosus

Ventricular septal defect

Coarctation of the aorta

Atrial septal defect

Cardiac arrhythmias

Atrial flutter

Atrial fibrillation

Premature atrial contraction

Atrioventricular nodal reentrant tachycardia (AVNRT)

Wolff-Parkinson-White syndrome

Ventricular tachycardia

Brugada syndrome

Premature ventricular contraction

Long QT syndrome and Torsade de pointes

Ventricular fibrillation

Atrioventricular block

Bundle branch block

Pulseless electrical activity

Valvular disorders

Tricuspid valve disease

Pulmonary valve disease

Mitral valve disease

Aortic valve disease

Cardiomyopathies

Dilated cardiomyopathy

Restrictive cardiomyopathy

Hypertrophic cardiomyopathy

Heart failure

Heart failure

Cor pulmonale

Cardiac infections

Endocarditis

Myocarditis

Rheumatic heart disease

Pericardial disorders

Pericarditis and pericardial effusion

Cardiac tamponade

Dressler syndrome

Cardiac tumors

Cardiac tumors

Cardiovascular system pathology review

Acyanotic congenital heart defects: Pathology review

Cyanotic congenital heart defects: Pathology review

Atherosclerosis and arteriosclerosis: Pathology review

Coronary artery disease: Pathology review

Peripheral artery disease: Pathology review

Valvular heart disease: Pathology review

Cardiomyopathies: Pathology review

Heart failure: Pathology review

Supraventricular arrhythmias: Pathology review

Ventricular arrhythmias: Pathology review

Heart blocks: Pathology review

Aortic dissections and aneurysms: Pathology review

Pericardial disease: Pathology review

Endocarditis: Pathology review

Hypertension: Pathology review

Shock: Pathology review

Vasculitis: Pathology review

Cardiac and vascular tumors: Pathology review

Dyslipidemias: Pathology review

Assessments

Supraventricular arrhythmias: Pathology review

USMLE® Step 1 questions

0 / 11 complete

Questions

USMLE® Step 1 style questions USMLE

of complete

A 73-year-old female presents to the emergency department with shortness of breath. She is concerned her “COPD is flaring up.” Past medical history is notable for hypertension, chronic obstructive pulmonary disease, and type II diabetes mellitus. She has been smoking one pack of cigarettes per day for twenty years. Temperature is 37.0°C (98.6°F), pulse is 136/min, respirations are 22/min, blood pressure is 104/72 mmHg, and oxygen saturation is 92% on room air. The patient is currently speaking in three to four word sentences and demonstrates increased work of breathing. There are bilateral rales throughout the lung fields, and the electrocardiogram from triage is shown below:  


Based on this patient's electrocardiogram, which of the following is the most likely diagnosis?  

Transcript

Content Reviewers

Antonia Syrnioti, MD

Contributors

Antonella Melani, MD

Evan Debevec-McKenney

Talia Ingram, MSMI, CMI

Melissa is a 21 year old college student who is having the time of her life at a party. It’s late, and unfortunately she has class the next morning, so she drinks a ton of coffee to sober up. On her way out, Melissa collapses to the floor, but wakes up after a couple of seconds. On her way to the emergency room, she tells the paramedics that she’s “aware of her heartbeat”. Then comes Taylor, a 32 year old female who is brought to the emergency room by her partner because she suddenly collapsed for a couple of minutes while cooking dinner. Taylor is now awake, and she tells you that right before collapsing she was feeling dizzy and like her heart was racing, but now she’s fine. They are both placed on different monitors. Melissa’s heart rate is 200 beats per minute and regular, and this is Melissa’s ECG. On the other hand, Taylor’s heart rate is 80 beats per minute and regular, so everything seems fine. However, her ECG shows this.

All right, so both Melissa and Taylor experienced palpitations and syncope, and their ECGs reveal they both have some form of arrhythmia. The best way to approach arrhythmias is to first: know what a normal ECG looks like, and second: have a good classification system to narrow down the diagnosis.

First, let’s review the normal electrical conduction pathway in the heart, and how it looks like on an ECG. An ECG tracing specifically shows how the depolarization wave flows through the heart during each heartbeat. The normal electrical activity of the heart starts in the sinoatrial or SA node and is then conducted through the atrium, creating the P wave on ECG. From the atrium, electrical activity goes 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. On an ECG, this will create the QRS complex, which represents the depolarization of the ventricles; and finally the T wave, which represents the repolarization of the ventricles. To help identify an irregular rhythm you can look at the morphology of the waveform and make sure that there is a P wave before every QRS complex, and a QRS complex after every P wave.

Now let’s take a look at the heart rate. The resting heart beats at a rate between 60 to 100 times per minute, and each of those beats starts off with depolarization of the sinoatrial node, and so we call it a normal sinus rhythm. For your exams, you should be able to figure out the heart rate on an ECG. To do that, you can count the number of boxes between R waves. Each small box represents 0.04 seconds, and each big box is five small boxes, so each big box is 0.2 seconds. One quick way to estimate the heart rate on an ECG, is to remember that the heart rate is 300, 150, 100, 75, 60, 50 depending on whether there’s 1, 2, 3, 4, 5, or 6 boxes between R waves. It's also important to know that there is normally a delay in conduction at the AV node and the Bundle of His, which gives some time for ventricular filling before the ventricle contracts. On the ECG, this is represented by the PR interval, which should be less than 5 small boxes, or 200 milliseconds.

Summary

An arrhythmia is any disturbance in the rate, rhythm, site of origin, or conduction of the cardiac electrical impulse. Supraventricular arrhythmias are a group of cardiac arrhythmias that originate at or above the atrioventricular node and have a narrow QRS complex (<120 ms). Supraventricular arrhythmias include atrial fibrillation, atrial flutter, and supraventricular tachycardia.

Supraventricular arrhythmias can cause a patient's heart rate to become too fast (tachycardia) or too slow (bradycardia). They can also cause stasis of blood flow in the atrial compartment and increase the risk of clot formation, especially in the left atrial appendage. These clots can dislodge, and travel into the systemic circulation, causing potentially life-threatening pathologies like embolic strokes, acute limb ischemia, central retinal artery occlusion, or acute mesenteric ischemia.

Common symptoms seen in supraventricular arrhythmias include palpitations, dizziness, shortness of breath, and chest pain. Treatment for these arrhythmias usually involves medications like beta-blockers, calcium channel blockers, digoxin, and other antiarrhythmic drugs; or procedures like electrical cardioversion and catheter ablation. In some cases, lifestyle modifications may be recommended to reduce the risk of developing arrhythmias.

Sources

  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Josephson's Clinical Cardiac Electrophysiology" Lippincott Williams & Wilkins (2015)
  3. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  4. "Novel PRKAG2 Mutation Responsible for the Genetic Syndrome of Ventricular Preexcitation and Conduction System Disease With Childhood Onset and Absence of Cardiac Hypertrophy" Circulation (2001)
  5. "Josephson's Clinical Cardiac Electrophysiology" Lippincott Williams & Wilkins (2015)
  6. "Multifocal Atrial Tachycardia" New England Journal of Medicine (1990)
  7. "Risk Factors and Genetics of Atrial Fibrillation" Cardiology Clinics (2014)
  8. "Alcohol and Atrial Fibrillation" Journal of the American College of Cardiology (2016)
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