Clinical ECG: Conduction Blocks, Pacemakers, and Electrolyte Disturbances PDF

Clinical ECG: Conduction blocks, Pacemakers, and Electrolyte Disturbances Scott Landman, OMS-III, Academic Medicine Scholar [email protected] Dr. Todd Cohen, Chief of Cardiology and Director of Medical Device Innovation [email protected]  Session Objectives 1. Differentiate and manage the differe...

Clinical ECG: Conduction blocks, Pacemakers, and Electrolyte Disturbances Scott Landman, OMS-III, Academic Medicine Scholar [email protected] Dr. Todd Cohen, Chief of Cardiology and Director of Medical Device Innovation [email protected]  Session Objectives 1. Differentiate and manage the different types of AV blocks. 2. Understand bundle anatomy and identify between left vs right bundle branch block. 3. Recognize ECG changes due to electrolyte imbalances. AV Conduction Blocks Delay or interruption in the transmission of the impulse from the atria to the ventricles Scott’s Tree of AV Blocks 1st Degree 2nd Degree Type 1 First Degree AV Heart Block Delayed conduction from atrium to ventricle (but no interruption) Prolonged PR interval (> 200 msec) All PR intervals are equal Usually asymptomatic Can be caused by medications No treatment required Second Degree AV Block: Mobitz Type I (Wenckebach) The PR interval progressively increases until one p-wave is blocked and isn’t transmitted to the ventricles Notable PR interval lengthening with a P-wave not followed by a QRS complex The cycle starts all over again after that drop (regularly irregular) Treatment is usually not indicated as this rhythm usually is asymptomatic AV Conduction Blocks Delay or interruption in the transmission of the impulse from the atria to the ventricles Scott’s Tree of AV Blocks 1st Degree 2nd Degree Type 1 Second Degree AV Block: Mobitz Type II Dropped QRS complex that is NOT preceded by a lengthening of the PR interval The PR interval is consistent (either normal or prolonged), until one p-wave is blocked and isn’t transmitted to the ventricles Symptoms may be present and are more common than Mobitz Type I and include presyncope, syncope, fatigue, or SOB More serious than type I second-degree AV block May progress to third degree (complete) AV block Often treated with a pacemaker  Third Degree (Complete) Heart Block The atria and ventricles beat independently of each other P-waves are not associated with QRS complexes Atrial pacing is greater than ventricular pacing ECG will show equal RR intervals and equal PP intervals but no association May be caused by MI, degeneration of the conductive tissue, and Lyme Disease Treated with a Pacemaker Third Degree (Complete) Heart Block Pacemaker Summary: AV Blocks Kaltura: Questions related to Objective #1 Cardiac Conduction System: Bundle Branches  Left Bundle Branch Block (LBBB) Normally, the septum is activated from left to right In LBBB, septal depolarization is reversed Leads to QRS duration > 120ms Produces tall R waves in the lateral leads (I, V5-6) and deep S waves in the right precordial leads (V1-3) Produces a broad or notched (‘M’-shaped) R wave in the lateral leads (V5, V6) and (‘W’-shaped) dominant deep S waves in V1 Left Bundle Branch Block (LBBB) Right Bundle Branch Block (RBBB) QRS duration is greater than 120 msec QRS in V1-V2 displays rSR’ pattern “bunny ears” or the letter “M” Lateral leads (I, V6) broad deep S-wave that is greater than R-wave duration. Bundle Branch Block “Turn Signal Theory” Criteria: QRS complex > 120 msec, reference lead V1  Summary of Objective #2 LBBB vs. RBBB: reference lead V1 with the “Turn Signal Theory” LBBB: ‘W’-shaped in V1 RBBB: ‘M’-shaped in V1 Kaltura: Questions related to Objective #2 Wanna talk electrolyte disturbances? K  Hyperkalemia Potassium (K+): 3.5-5.0 mEq/L ECG changes depend on serum level and how rapid of a change K+ = 5.5 - 6.5 mEq/L **Tall, peaked, narrow based T waves** QT interval shortening K+ = 6.5 - 7.5 mEq/L First-degree AV block QRS widening K+ > 7.5 mEq/L Disappearance of P waves  Hypokalemia (HypUkalemia) Severe or symptomatic hypokalemia Depression of the ST segment, decrease in the amplitude of the T-wave, and an increase in the amplitude of U waves U-waves are often seen in the lateral precordial leads V4 to V6 Prolongs the QT interval Increased amplitude and width of the P-wave  Hypercalcemia Calcium, serum (total): 8.5-10.2 mg/dL QT interval shortening (usually due to shortening of the ST segment) Note: Little if any effect on P, QRS, or T wave  Hypocalcemia Prolonged QT interval (earliest and most common finding) due to ST segment prolongation No change in the duration of the T wave (seen only with hypocalcemia or hypothermia)  Hypothermia: Osborne “J” Waves Hypothermia results in sinus bradycardia with widening of the QRS Prolongation of PR and QT intervals Osborne (“J”) waves, which are late upright terminal deflections of the QRS complex (“camel hump” sign)  Summary Hyperkalemia: tall peaked T-waves, QT interval shortening Hypokalemia: ST segment depression, shallow T-waves, U-waves Hypercalcemia: QT interval shortening Hypocalcemia: Prolonged QT interval Hypothermia: Osborne “J” waves Kaltura: Questions related to Objective #3 More “fun” topics: Left Ventricular Hypertrophy Sick Sinus Syndrome  Left Ventricular Hypertrophy (LVH) Response to pressure overload states Increase in size of the myocardial fibers Parallel addition of sarcomeres Causes Hypertension (most common cause) Aortic stenosis Aortic regurgitation Mitral regurgitation Coarctation of the aorta Hypertrophic cardiomyopathy Sick Sinus Syndrome When the SA node is damaged and no longer generates normal heartbeats at a normal rate Another cause of Pathologic Bradycardia Most common caused is gradual loss of SA node function that comes with age Sx: Dizziness, Pre-syncope, Syncope, SOB, Fatigue Tx: Pacemaker How I would approach the lecture: 1. Differentiate and manage the different types of AV blocks. a. What is an AV block? b. How many AV blocks are there? How do we separate them based on tx? c. What are the ECG findings of the different AV blocks? How I would approach the lecture: 2. Understand bundle anatomy and identify between left vs right bundle branch block. a. Know what the bundle branches are. b. Understand that the QRS will be prolonged. c. Identify the ECG findings of the L and R BBBs. How I would approach the lecture: 3. Recognize ECG changes due to electrolyte imbalances. a. Hypokalemia, Hyperkalemia b. Hypocalcemia, Hypercalcemia c. Osborne J Waves Final Slide: Questions: Scott Landman: [email protected] More exposure→ better EKG skills -ECG Lectures Mon 12-1 PM EST with Dr. Cohen via Zoom -Will be sent out to the class each week by Dr. Cohen’s Research Team Feedback on the lecture: https://comresearchdata.nyit.edu/redcap/surveys/?s=HRCY448FWYXREL4R