Question Of The Day #25

question of the day
qod25
835 - 3rd degree heart block

Which of the following is the most likely diagnosis of this patient’s condition?

This patient has marked bradycardia on exam with a borderline low blood pressure. These vital sign abnormalities are likely the cause of the patient’s dizziness. Bradycardia is defined as any heart rate under 60 beats/min. The most common cause of bradycardia is sinus bradycardia (Choice A). Other types of bradycardia include conduction blocks (i.e. type 2 or type 3 AV blocks), junctional rhythms (lack of P waves with slow SA nodal conduction), idioventricular rhythms (wide QRS complex rhythms that originate from the ventricles, not atria), or low atrial fibrillation or atrial flutter. About 80% of all bradycardias are caused by factors external to the cardiac conduction system, such as hypoxia, drug effects (i.e., beta block or calcium channel blocker use or overdose), or acute coronary syndromes.

ecg qod25Sinus bradycardia (Choice A) occurs when the electrical impulse originates from the SA node in the atria. Signs of sinus bradycardia on EKG are the presence of a P wave prior to every QRS complex. This EKG shows P waves prior to each QRS complex, but there are extra P waves that are not followed by QRS complexes. Some P waves are “buried” within QRS complexes or within T waves. The EKG below marks each P wave with a red line and each QRS complex with a blue line.

 

First-degree AV Block (Choice B) is a benign arrhythmia characterized by a prolonged PR interval. This patient’s EKG has variable PR intervals (some prolonged, some normal). This is a result of a more severe AV conduction block. Second-Degree AV Blocks are divided into Mobitz type I and Mobitz Type II. Mobitz type I, also known as Wenckebach, is characterized by a progressive lengthening PR interval followed by a dropped QRS complex. This can be remembered by the phrase, “longer, longer, longer, drop.” Wenckebach is a benign arrhythmia that does not typically require any treatment. Mobitz type II (Choice C) is characterized by a normal PR interval with random intermittent dropping of QRS complexes. This patient’s EKG has consistent spacing between each QRS complex (blue lines) and consistent spacing between each P wave (red lines). However, the P waves and QRS complexes are not associated with each other. This phenomenon is known as AV dissociation. These EKG changes are signs of a complete heart block, also known as Third-Degree AV Block (Choice D). Both Second-Degree AV block- Mobitz type II (Choice C) and Third-Degree AV Block (Choice D) are more serious conduction blocks that require cardiac pacemakers. Correct Answer: D

References

  • Brady W.J., & Glass III G.F. (2020). Cardiac rhythm disturbances. Tintinalli J.E., Ma O, Yealy D.M., Meckler G.D., Stapczynski J, Cline D.M., & Thomas S.H.(Eds.), Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=2353&sectionid=218687685
  • Nickson, C. (2020). Heart Block and Conduction Abnormalities. Life in the Fast Lane. Retrieved from https://litfl.com/heart-block-and-conduction-abnormalities/

 

Cite this article as: Joseph Ciano, USA, "Question Of The Day #25," in International Emergency Medicine Education Project, February 5, 2021, https://iem-student.org/2021/02/05/question-of-the-day-25/, date accessed: May 25, 2022

Question Of The Day #24

question of the day
qod24
738.1 - Prior ECG before 738.2 - STEMI

Which of the following is the most appropriate next step in management for this patient’s condition?

This patient is suffering from severe bradycardia with signs of poor cardiac output, shock, and diminished perfusion to the brain. Bradycardia is defined as any heart rate under 60 beats/min. Many individuals may be bradycardic at rest with no danger to the patient (i.e. young patients or athletes). Bradycardia in these scenarios is physiologic and is not associated with difficulty in perfusing the brain and other organs. This patient’s 12-lead EKG shows sinus bradycardia since there is a P wave prior to every QRS complex. Sinus bradycardia is the most common type of bradycardia. Other types of bradycardia include conduction blocks (i.e. type 2 or type 3 AV blocks), junctional rhythms (lack of P waves with slow SA nodal conduction), idioventricular rhythms (wide QRS complex rhythms that originate from the ventricles, not atria), or slow atrial fibrillation or atrial flutter. About 80% of all bradycardias are caused by factors external to the cardiac conduction system, such as hypoxia, drug effects (i.e. beta block or calcium channel blocker use or overdose), or acute coronary syndromes.  

For any patient with a bradyarrhythmia or tachyarrhythmia, it is crucial to determine if the arrythmia is “stable” or “unstable”. Signs that an arrhythmia is unstable include altered mental status, hypotension with systolic blood pressure under 90mmHg, chest pain, or shortness of breath. Patients with a stable arrhythmia can be managed supportively with observation and less invasive medical management. Patients with unstable arrhythmia are managed more aggressively with the use of electricity, often in combination with other medical treatments. This patient has an unstable bradyarrhythmia, given her altered mental status and hypotension. Intravenous metoprolol (Choice D) would make the patient more bradycardic since this medication blocks beta-adrenergic receptors of the heart that control heart rate and contractility. Intravenous Amiodarone (Choice C) is an antiarrhythmic agent used often in wide complex tachyarrhythmias (i.e. Ventricular Tachycardia). Intravenous atropine or epinephrine are agents that can be used in this patient prior to preparing for electric pacing. Transcutaneous pacing (Choice A) should always be attempted prior to Transvenous pacing (Choice B), as Transcutaneous pacing is less invasive and quicker to set up. If Transcutaneous pacing does not result in electrical “capture” or change the heart rate, the next step is Transvenous pacing. Correct Answer: A 

References

  • Brady W.J., & Glass III G.F. (2020). Cardiac rhythm disturbances. Tintinalli J.E., Ma O, Yealy D.M., Meckler G.D., Stapczynski J, Cline D.M., & Thomas S.H.(Eds.), Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=2353&sectionid=218687685
  • Burns, E. (2020). Sinus Bradycardia. Life in the Fast Lane. Retrieved from https://litfl.com/sinus-bradycardia-ecg-library/
Cite this article as: Joseph Ciano, USA, "Question Of The Day #24," in International Emergency Medicine Education Project, December 11, 2020, https://iem-student.org/2020/12/11/question-of-the-day-24/, date accessed: May 25, 2022