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Case Scenario Case Scenario An 87-year-old woman reports feeling weak and short of breath for 2 hours while walking short distances. She feels exhausted moving from the car to the ED stretcher. Case 7 Bradycardia On physical exam she is pale and sweaty; HR = 35 bpm; BP = 90/60 mm Hg; RR = 18 rpm. Rhythm: see next slide. © 2001 American Heart Association 1 2 87-Year-Old Woman: Symptomatic Bradycardia 3 87-Year-Old Woman: Symptomatic Bradycardia Identify A, B, and C Which one is most likely A to be her rhythm? Learning Objectives She experienced no chest pain or ischemic symptoms A prior to the onset of her weakness and shortness of breath. Therefore, the only rhythm not associated with acute pain, rhythm A, is the more likely cause of her symptomatic bradycardia. B 1. By the end of Case 7 be able to discuss • Asymptomatic vs symptomatic bradycardia • Signs and symptoms of symptomatic bradycardia • Intervention agents and sequences to use • Recognition criteria for heart blocks: 1st, 2nd (types I and II), and 3rd degree • Pathology of conduction system in heart blocks C 4 5 Learning Objectives 6 What is Symptomatic? 2. By the end of Case 7 be able to discuss • Significance of bradycardia in AMI patients • Significance of RV infarction plus bradycardia • Atropine pharmacology: why atropine helps some heart blocks and not others • Set up, start, troubleshoot transcutaneous pacing 7 What is Symptomatic? Bradycardia is symptomatic when: • Heart rate is “slow” (absolute or relative) • Patient has symptoms • Symptoms are caused by bradycardia aa 8 Symptoms • Chest pain • Dyspnea • Weakness • Altered LOC aa 9 1 What is Symptomatic? What is Symptomatic? Signs • Hypotension • Diaphoresis • Pulmonary congestion • PVCs • Unstable angina aa What is Symptomatic? Drugs to Learn 12 Drugs to Learn Sinus bradycardia Heart blocks • 1st degree • 2nd degree type I • 2nd degree type II • 3rd degree 13 If the etiology is AMI: • Treat the AMI (MONA) aa 11 Rhythms to Learn Key point: • Treat the patient and NOT the monitor. aa Key question: • Is the bradycardia causing the patient to be ill? OR • Is there some illness that is causing the bradycardia? aa 10 What is Symptomatic? The actions, indications, administration, and precautions for these drugs and therapies: • Atropine • Dopamine • Epinephrine • Transcutaneous pacing • Isoproterenol (rarely used) 14 Cardiac Conduction System 1 15 Cardiac Conduction System 2 Bachmann’s bundle Remember: Relationship of ECG to anatomy Sinus node • Atropine – will not work on denervated hearts. Why? • Epinephrine – must be used with caution with some patients. Why? Internodal pathways AV node Bundle of His Left bundle branch Posterior division Anterior division Right bundle branch 16 Purkinje fibers 17 18 2 Determining the Rate Analyzing Rhythm Strips 19 Relationship of P Waves and QRS Complexes Key questions • Are QRS complexes present? • Are P waves present? • How is the P wave related to the QRS complex? 20 What Is This Rhythm? 21 AV Block Every P wave is followed by a QRS complex with a normal P–R interval Every P wave is followed by a QRS complex but the P–R interval is prolonged Some P waves are not followed by a QRS complex; more P waves than QRS complexes First-degree AV block Delay This is First Degree Block. 22 Diagnosis? 23 Diagnosis? 24 AV Block Second-degree type I AV block This is Sinus Bradycardia. This is Second-degree type I AV block. Note the progressive PRI. 25 26 27 3 Diagnosis? Differentiation of Second- and Third-Degree AV Blocks AV Block Second-degree type II AV block More P’s than QRSs yes Non-Conducting P waves PR fixed? yes 2nd-degree AV block Fixed Mobitz II no QRSs that look alike regular? This is Second-degree type II AV block. Note the non-conducting Ps. 29 Bradycardia Algorithm (1 of 2) Primary ABCD Survey • Assess ABCs • Secure airway noninvasively • Ensure monitor/defibrillator is available Secondary ABCD Survey Assess secondary ABCs (invasive airway management needed?) Oxygen–IV access–monitor–fluids Vital signs, pulse oximeter, monitor BP Obtain and review 12-lead ECG Obtain and review portable chest x-ray Problem-focused history Problem-focused physical examination Consider causes (differential diagnoses) For example: • OR you can say that each 6 gtts = 1 µg • Prepare for transvenous pacer • If symptoms develop, use transcutaneous pacemaker until transvenous pacer placed aa 32 What Is This Rhythm? Bradycardia Algorithm (2 of 2) Bradycardia Algorithm (2 of 2) signs or symptoms? For example: Serious Due to bradycardia? No • 1 mg Epinephrine or Isuprel inYes100 ccs NS Type II second-degree AV block/ cc or 60 gtts / min – 10 µgs Intervention sequence or Third-degree AV block? • Atropine 0.5 to 1.0 mg pacing if available – 7.5 µgs = 45 gtts / min•• Transcutaneous Dopamine 5 to 20 µg/kg per minute 2 to 10 µg/min – 5 µgs = 30 gtts / min •• Epinephrine Isoproterenol 2 to 10 µg/min No – 2.5 µgs = 15 gtts / min Yes Observe 31 30 Bradycardia Algorithm (2 of 2) Bradycardia •Slow (absolute bradycardia = rate <60 bpm) or •Relatively slow (rate less than expected relative to underlying condition or cause) 3rd-degree AV block 2nd-degree AV block Variable Mobitz I Wenckebach no 28 • • • • • • • • yes aa 33 AV Block Remember that Isoproterenol must only be considered if the patient fails to respond to other therapies. You must exercise extreme caution when using it. Why? Third-degree AV block Consistent P to P interval This is Third-degree AV block. Supranodal – note the atrial rate is between 48 - 70 aa 34 35 36 4 Treatment? What Is This Rhythm? 37 What Is This Rhythm? 38 39 Indications for Transcutaneous Pacing Treatment? Hemodynamically unstable bradycardias In the setting of AMI: sinus node dysfunction, type II 2nd-degree block, 3rd-degree heart block Bradycardia with symptomatic ventricular escape beats 40 Indications for Transcutaneous Pacing Indications for Transcutaneous Pacing 41 In the presence of escape beats, you must decide • if the PVCs are effective contractions • Should they be treated with pacing or medications (rate related fix) aa 42 Transcutaneous Pacing: “Capture” vs “No Capture” Transcutaneous Pacing 25 Feb 88 Lead I Size 1.0 HR=41 Bradycardia: No Pacing 25 Feb 88 Lead I Size 1.0 HR=43 Bradycardia: no pacing However, 3rd degree block should NEVER be treated with lidocaine. Why? Pacing Spike 35 mA Pacing below threshold: no capture Capture: • Spike + broad QRS • QRS: opposite polarity Pacing Below Threshold (35 mA): No Capture 25 Feb 88 Lead I Size 1.0 HR=71 60 mA Pacing above threshold: with capture aa Pacing Above Threshold (60 mA): With Capture (Pacing-PulseMarker 43 44 ) 45 5 Rates of Intrinsic Cardiac Pacemakers Pulse Generators for Transvenous Pacing Primary pacemaker • Sinus node (60-100 bpm) Escape pacemakers • AV junction (40-60 bpm) • Ventricular (<40 bpm) Characteristics Variable output in milliamps Fixed versus demand mode Variable rate setting Firing and sensing indicators Familiarize yourself with the equipment! 46 Dopamine • Add 200 mgs into a 250 cc bag of IV NS • Patient weight is 225 lbs. • The initial dose would be ____ gtts? aa Drug Calculation Dopamine • 200 mgs into a 250 cc bag of IV NS – 200 X 1000 µg = 200,000 µg OR – 800 µg per cc OR – 13.333 µg per gtt • Patient weight is 225 lbs. • The initial dose would be ____ gtts? aa 47 Drug Calculation Drug Calculation 49 Dopamine - effects Dopamine • So…… • Patient weight is 225 lbs. – 225 / 2.2 lbs = 100 kgs – 100 kgs X 5 µg/min = 500 µg/min – 500 µg / 13.333 = 37.5 gtts per minute aa 50 Infarct Location Arrhythmias RV • Often present with increased parasympathetic tone Look for volume problems with associated hypovolemia Determining the pattern 48 alpha • heart:none • arteries:constriction lungs:constriction beta • heart: > rate arteries: dilation lungs: mild dilation Cardiac dosage range is 5 µg - 10 µg/kg/min aa 51 Escape Patterns Regular Premature Speeding/slowing Pause Group beats Irregularly Irregular 52 53 54 6 Action Potential of Pacemaker Cell Second-Degree AV Block Type I 55 56 7