Act In Time

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Act In Time

• Myocardial Infarction and Prehospital Care
• Region VIII EMS Systems
• January 2008
•  
• Content produced by the Good Samaritan EMS System

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Objectives

• Describe the normal coronary anatomy
• Describe chronic and acute changes that happen
  with coronary artery disease
• Given a scenario describing typical and/or
  atypical signs and symptoms, the EMT will be able
  to identify a patient presenting with Acute
  Coronary Syndrome, and choose and apply
  appropriate treatment(s) to that patient
• Discuss current local best practices for handling
  of patients with myocardial infarction
• Review basic concepts of 12-lead
  electrocardiography and how to identify patterns
  consistent with ischemic changes

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FYI
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Cardiac Patient Rights

• Its all about identifying
• the right patient
• in the right time
• getting them to the right place
• for the right therapy

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Prehospital STEMI detection

• S-T segment
• Elevation
• Myocardial
• Infarction
• 12-Lead ECG
• Cardiac Alert

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2005 AHA
Nationally only 10 of EMS services use 12-lead
ECGs in the ambulance
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Act In Time

• There are approximately 1.5 million myocardial
  infarction cases in the US annually, with
  500,000-700,000 deaths related to coronary artery
  disease each year.
• The American Heart Association and the NIH
  National Heart, Lung and Blood Institute have a
  public information initiative to
• raise public awareness of the symptoms of heart
  attack
• reinforce how vital it is that the public access
  9-1-1 at the initial onset and recognition of
  symptoms.
• Their hope is that we will get called earlier,
  when less permanent myocardial damage has
  occurred and when outcomes can be improved.

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Heart Attack Warning Signs

• From Act In Time, layperson education
• Chest discomfort
• Uncomfortable pressure, squeezing, fullness or
  pain in the center of the chest that lasts more
  than a few minutes, or goes away and comes back
• Discomfort in other areas of the upper body
• Can include pain or discomfort in one or both
  arms, the back, neck, jaw or stomach
• Shortness of breath
• Often comes with or before chest discomfort
• Other signs
• May include breaking out in a cold sweat, nausea
  or light-headedness

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Cardiac Anatomy Review
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The Heart

• Four chambers
• Hollow
• Muscular
• Dual Circulation
• feeds the heart muscle itself
• circulates blood outside the heart
• lungs for oxygenation and CO2 offload
• peripheral supply to tissues, organs and organ
  systems

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Myocardial Oxygen Supply

• To remain healthy, the myocardium requires
• the removal of deoxygenated blood
• a fresh supply of oxygenated blood

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Right Heart

• Receives deoxygenated blood from
• systemic circulation
• vena cavae
• coronary circulation
• coronary sinus
• Blood passes from
• right atrium
• through tricuspid valve
• right ventricle
• pulmonic valve
• pulmonary artery
• to lungs

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Left Heart

• Receives reoxygenated blood from pulmonary vein
• Blood passes from
• left atrium
• mitral valve
• left ventricle
• aortic valve
• aorta

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Aorta

• Oxygenated blood in the aortic root can enter the
  coronary arteries
• Most myocardial blood supply occurs during
  diastole
• the aortic valve leaflets are closed and do not
  obstruct the coronary artery roots
• the subendocardial blood vessels are not
  compressed (as they are during systole) allowing
  blood to flow into the myocardium itself
• in the normal cardiac cycle, diastole is longer
  than systole

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Coronary Artery Disease

• Any narrowing of the coronary arteries causes
• diminished blood supply
• restriction of delivery of electolytes and
  nutrients

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LCA

• Left
• Left main divides into two branches
• Left Anterior Descending (LAD)
• Anterior wall of LV
• RBB and portions of LBB
• Associated with Anterior Wall MI
• Circumflex (Cx)
• Lateral and Posterior walls of LV
• Left atrium
• SA node in 30
• Associated with Lateral Wall MI

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RCA

• Right
• Right Atrium (RA)
• Right Ventricle (RV)
• Inferior and Posterior LV
• SA node in 60
• AV node
• Associated with right ventricular MI or
  dysrhythmias affecting SA and AV nodes

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Cardiac Rhythm Disturbances

• Rhythm disturbances can hamper delivery of blood
  to the myocardium
• HR (heart rate) x SV (stroke volume) CO
  (cardiac output)
• CO has a direct affect on CPP (coronary perfusion
  pressure), particularly diastolic blood pressure
  (and Mean Arterial Pressure MAP)
• Bradycardia
• ? HR ? CO
• Tachycardia
• ? HR ? SV (decreased preload) ? CO
• Interrupted Synchronicity
• ? SV (loss of atrial kick) ? CO
• Although not every patient in Af, or brady- or
  tachycardias has decreased CPP, patients with
  pre-existing decreased coronary artery blood flow
  can be negatively affected by those dysrhythmias

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Collateral Circulation

• If coronary artery disease and stenosis develop
  slowly, collateral circulation can develop
• When the stenosis is acute, collateral
  circulation does not have time to develop

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Myocardial Ischemia

• Oxygen deprivation to the heart muscle
• Inadequate removal of metabolites
• Reduced blood flow / perfusion
• Patients with myocardial hypoxia (oxygen
  deprivation) do not exhibit ischemic symptoms
• No reduction of clearance of metabolites
• Congenital heart disease
• Cor pulmonale
• Severe anemia
• Asphyxiation
• CO poisoning

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Ischemic Symptoms

• O May come on at rest, or with exertion or
  stress
• P Breathing or changing posture does not
  notably influence the severity of the pain
• Q - Pressure or heaviness, or as a sensation of a
  tight band around the chest
• R - Retrosternal area, possibly radiating to the
  arms (usually to the left arm), back, neck, or
  the lower jaw
• S Usually severe, similar to previous ischemic
  episodes
• T - Duration usually over 20 minutes, continuous,
  and its intensity does not alter

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Other Findings

• The symptoms (pain beginning in the upper
  abdomen, nausea) may resemble the symptoms of
  acute abdomen. Nausea and vomiting are sometimes
  the main symptoms, especially in inferoposterior
  wall ischemia.
• In inferoposterior wall ischemia, vagal reflexes
  may cause bradycardia and hypotension, presenting
  as dizziness or fainting.
• Electrocardiogram (ECG) is the key examination
  during the first 4 hours after pain onset, but
  normal ECG does not rule out an imminent
  infarction

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Other Cardiac Chest Pain

• Can also be caused by angina pectoris and its
  derivatives
• A typical occurrence of angina happens when
  myocardial oxygen demand exceeds supply
• This is commonly caused by the disease processes
  atherosclerosis and arteriosclerosis, and
  uncommonly by a variation called Prinzmetals
  angina
• Prinzmetals angina is commonly accompanied by ST
  elevation, which often resolves with
  nitroglycerine administration (along with the
  relief of the pain).
• Classic angina is not usually associated with
  ST-segment changes
• Most patients with angina pectoris report
  retrosternal chest discomfort rather than
  describing pain

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Angina

• Anginal pain may be localized primarily in the
  epigastrium, back, neck, jaw, or shoulders.
• Typical locations for radiation of pain are arms,
  shoulders, and neck.

• Typical angina
• precipitated by exertion, eating, exposure to
  cold, or emotional stress
• lasts for approximately 1-5 minutes and is
  relieved by rest or nitroglycerin
• pain lasting only a few seconds is not usually
  angina pectoris
• the intensity of angina does not change with
  respiration, cough, or change in position
• pain above the mandible and below the epigastrium
  is rarely anginal in nature

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Myocardial Infarction

• Myocardial infarction (MI) is the irreversible
  necrosis of heart muscle secondary to prolonged
  ischemia.
• MI is commonly diagnosed in the field by patient
  symptoms and ECG findings, known as ST-segment
  Elevation MI (STEMI).
• MI is also is considered part of a spectrum
  referred to as acute coronary syndrome (ACS),
  which also includes unstable angina and
  nonST-elevation MI (NSTEMI).
• Patients with ischemic discomfort may or may not
  have ST-segment elevation.
• Those without ST elevations will ultimately be
  diagnosed with unstable angina or NSTEMI based on
  laboratory tests such as cardiac enzymes

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Non-Ischemic Causes of Chest Pain

• Esophageal reflux or spasm
• Pulmonary embolism
• Hyperventilation
• Pneumothorax
• Aortic dissection
• Pericarditis
• Pleuritis
• Costochondritis
• Early herpes zoster
• Peptic ulcer, cholecystitis, pancreatitis

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Review procedures in place at your transporting
hospitals for STEMI or Cardiac Alerts
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12-Lead Tips

• Lead Placement is crucial
• The lower limb leads should be placed on the
  distal extremities.
• The upper limb leads should either be placed on
  the wrists, biceps, or as close to the
  claviculohumeral junction as possible (for proper
  axis).
• Excessive artifact or motion can make the ECG
  difficult or impossible to obtain and interpret.

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Lead Placement

• v1 - 4th ICS, R sternal border
• v2 - 4th ICS, L sternal border
• v3 - midway between v2 v4
• v4 - 5th ICS, L MCL
• v5 - 5th ICS, between v4 v6
• v6 - 5th ICS, L mid-axillary line
• Tip
• Some find it easier to put the leads on in this
  order v1, v2, v4, v6 then put v3 and v5 on
  between their contiguous leads

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Site Prep

• To obtain a high quality ECG to interpret, you
  must prepare the electrode site properly.
• Remove excess hair and dry the skin.
• Apply electrodes carefully so that the gel
  surface is properly contacting the patients
  skin.
• Make sure the lead wire is not tugging on the
  electrode, which may affect contact.
• Avoid bony prominences when placing electrodes.
• For females with large breasts, place lead v3 on
  the breast, and v4/5/6 below the breast.
• Wavy baselines can be caused by patient movement,
  poor electrode contact, dry electrodes,
  respiratory (chest wall) interference, and
  electrode movement. Consider changing
  electrodes, encourage the patient to relax / hold
  still / not talk for the acquisition time (3 10
  seconds), or even holding his breath.

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Other 12-Lead Stuff

• The leads of a 12-lead ECG correlate with the
  walls of the myocardium, which in turn are
  related to coronary arteries that feed each
  specific region. Coronary artery anatomy is
  slightly different in each individual, but there
  is a high correlation between ischemia / damage
  patterns and which coronary artery is most likely
  compromised.
• Remember that conduction system abnormalities
  such as heart blocks and bundle branch blocks can
  be a sign of an underlying coronary blood supply
  problem.

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You Lookin at Me?

• It is important to look at contiguous leads to
  determine which area of the heart is affected.
  Each lead is like a camera lens that looks at
  an area of the heart.

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ECG Patterns

• As contiguous leads look at different parts of
  the heart, you may see an ischemic pattern that
  covers a large area or border area between two
  regions.
• For example, if there is ST-segment elevation in
  leads II/III/aVF/V5/V6, the ischemia appears to
  be on both the inferior and lateral areas,
  referred to as inferolateral.
• Likewise, there are anterolateral and
  anteroseptal (like the illustration here)
  ischemic patterns.
• What is an ischemic pattern? The AHA cites
  typical ST-segment elevation as gt 1 mm in 2 or
  more contiguous leads

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Treat The PatientNot The Monitor

• If the patients symptoms do not match the ECG,
  you need to do more detective work
• ECG is nondiagnostic in 50 of patients with
  chest discomfort

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Really Really Basic 12-Lead

• Assess the quality of the tracing
• Identify the rate and underlying rhythm
• Examine each lead for the presence of ST-segment
  displacement (elevation or depression)
• Assess the areas of displacement by lead
  groupings

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Practice Cardiac Scenario 1

• The patient is a 58 year old male c/o tightness
  in the chest. You arrive at the patient at 1000
  am. He describes the sensation as a squeezing,
  non-radiating, 7/10, pain that started about an
  hour ago, while he was sitting in his office
  writing checks to send out with bills, and has
  gotten steadily worse. Nothing makes it better
  and he is visibly uncomfortable, rubbing his
  sternum and left side ribs. There is no history
  of trauma.
•  
• He claims to have no acute medical problems, does
  not identify a history of high cholesterol or
  blood pressure. The patient takes one aspirin
  a day, on the advice of Readers Digest. He
  claims no allergies.
•  
• He is pale, diaphoretic and normal temperature.
  Pupils are 4 mm and PERL. Lungs are bilaterally
  clear. His trachea is midline, no JVD, no pedal
  edema. BP 136/88, P 56, R 14, T 99.4? F.
  Abdomen is soft and non-tender.

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Scenario 1

• What would your actions be?
• IMC
• Oxygen FiO2?
• Inquire about Viagra or other rx
• Baby ASA 324 mg unless taken within 8 hours
• If SBP gt 100 mmHg, NTG 0.4 mg SL spray
• Reassess VS including pain
• You have five minutes to
• Obtain 12-lead if so equipped
• Establish IV before next rx

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Scenario 1 ECG
Do you see any pattern?
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• Sinus Bradycardia _at_ 56
• ST-segment elevation in I, aVL, v2, v3, v4, v5,
  v6
• Apparent anterior ischemic pattern with lateral
  extension

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• Clinically Significant?
• You knew that already based on symptoms
• The 12-lead tends to confirm your clinical
  impression
• Lead II alone would not have been helpful
• What is next?

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Scenario 1 What is next?

• Second round actions, in home
• If SBP gt 100 mmHg and pain not relieved to zero,
  repeat NTG
• Contact Medical Control with assessment and ECG
  findings. Depending on receiving hospital
  protocol and availability, consider initiating
  Cardiac Alert
• Reassess VS including pain
•  
• Something to consider if symptoms (anything in
  the OPQRST) change, consider doing another
  12-lead, if available.
• Third round actions, in home or ambulance
• Consider morphine if pain not relieved to zero

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Practice Cardiac Scenario 2

• The patient is a 49 year old male c/o tightness
  in the chest. You arrive at the patient at 915
  am. He describes having a period of irregular
  heartbeats which seemed rhythmic for about five
  minutes. There was no syncope or dizziness with
  the irregular heartbeats.
•  
• The patient reports that the irregular heartbeat
  pattern ended, followed immediately by the onset
  of a squeezing or tightness sensation
  substernally, without radiation. His wife
  immediately called 911 when the discomfort began.
  He describes the discomfort as 3 or 4 out of
  10, beginning about ten minutes prior to your
  arrival, with no relation to exertion. It has
  remained constant intensity, has no provocation
  or palliation. He is visibly upset and
  uncomfortable.
•  
• He claims a history of borderline high
  cholesterol and blood pressure. His medications
  are Avapro, one multivitamin, one vitamin E, one
  garlic tab, and one adult aspirin per day, all of
  which he took this morning. He denies allergies.
•  
• He is pale, with slight diaphoresis. Pupils are
  4 mm and PERL, lungs are bilaterally clear,
  trachea is midline, no JVD, no pedal edema. BP
  139/76, P 84, R 12, T 98.4? F. Abdomen is soft
  and non-tender.

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Scenario 2

• What would your actions be?
• IMC
• Oxygen 4 L NC
• Pt denies Viagra, etc.
• ASA? - No
• NTG 0.4 mg SL spray
• Reassess VS including pain
• Obtain baseline 12-lead

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Scenario 2 ECG
Do you see any pattern?
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• Sinus Rhythm _at_ 85
• ST elevation in I, II, aVL, v3, v4, v5
• Inferolateral ischemia suggestive of MI (with
  symptoms)

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• Clinically Significant?
• You knew that already based on symptoms
• Lead II alone might have made you suspicious
• What is next?

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Scenario 2 What is next?

• Your partner gets an 18ga IV established in the
  forearm. The patient asks what you are seeing on
  the ECG, and you truthfully (but perhaps too
  bluntly) tell him it looks like youre having a
  heart attack. He becomes more pale and
  diaphoretic and c/o dizziness and feels faint.
  The ECG rhythm appears to have accelerated.
• What do you do?
• Reassessment BP 76/Palp, P 108, R 24, lungs
  clear. He states his pain is worse, now 7/10.
• What now?

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Moving Target!

• Switch SOPs the patient is hypoperfusing, P gt
  60 ? Cardiogenic Shock SOP
• IV fluid challenge 200 ml
• Move to ambulance, reassess
• Contact Medical Control
• BP 80/62, P 96, R 22, lungs clear, pain 8/10
• IV fluid challenge 200 ml, begin transport,
  reassess
• BP 108/66, P 92, R 20, lungs clear, pain 8/10.
• NTG 0.4 mg SL spray
• BP 104/62, P 88, R 20, lungs clear, pain 6/10
• Morphine 2 mg increments, reassess after each

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ECG Strip of the Month

• Bundle Branch Blocks

Not really a rhythm a conduction defect
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Conduction System Review

• Heart mechanical pump with electrical control
• Specialized nerve tissues that generate and
  conduct impulses
• Allows the myocardium to contract in an organized
  and efficient manner

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SA Node

• Located in R atrium
• Normally dominant pacemaker
• Intrinisic rate 60-100

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AV node / Bundle of His

• Located in the junction between the atria and
  ventricles
• Delays impulses so that atrial kick can
  complete
• Backup pacemaker intrinsic rate 40-60
• Bundle of His connects AV node with two bundle
  branches

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Right Bundle Branch (RBB)

• R side of septum
• Conducts impulses to RV
• Long, thin, more fragile than LBB

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Left Bundle Branch (LBB)

• Begins as single structure
• Short, thick
• Called L common bundle
• Divides into 3 fascicles
• Anterior
• feeds anterior and lateral LV
• Thin, vulnerable
• Posterior
• Feeds inferior / posterior LV
• Septal
• Feeds midseptum

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Bundle Branch Conduction

• Normal
• L side of septum is stimulated first
• Impulse crosses over _at_ Bundle of His to stimulate
  RV
• Ventricles depolarize simultaneously

• Delayed
• Impulse travels down unblocked branch and
  stimulates that ventricle first
• Impulse then travels cell-to-cell through the
  myocardium to stimulate other ventricle
• Ventricles depolarize asymmetrically

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BBB

• New onset of BBB is a significant finding
• Infarct-induced BBB carries with it an increased
  mortality rate of between 40 and 60, and the
  rate of cardiogenic shock increases up to 70
• New onset BBB implies extensive infarction
• Tissue lost to the infarct that produces the
  increase in mortality and cardiogenic shock

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Preexisting BBB

• Because the left anterior descending artery
  supplies much of the bundle branches, patients
  experiencing septal and anteroseptal infarctions
  are most likely to develop BBB
• An infarcting patient presenting with BBB may
  have had it as a preexisting condition
• Unless a previous electrocardiogram (ECG) is
  available for comparison or the BBB develops
  during the infarction, it can be difficult to
  determine which came first, the infarct or the BBB

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BBB ? advanced heart blocks

• BBB AMI higher likelihood of developing
  complete AV block
• Standby pacing is indicated when BBB complicates
  infarction
• When BBB is caused by infarct, it can quickly
  progress to a more complete block with a slow
  ventricular rate

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Recognition

• Widened QRS (gt 0.12 sec) on a complex of
  supraventricular origin
• Advanced heart blocks such as 3rd degree may have
  intrinsically wider QRS complexes
• Can be detected in lead II

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Left vs Right BBB
Turn Signal Method Look at the terminal
portion of the QRS (the last 0.04 seconds) Is it
pointing up (positive deflection) or down
(negative deflection)? Remember how your turn
signals work? Up right turn Down left turn

• Positive deflection? RBBB

• Negative DeflectionLBBB

Only applies to lead v1
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Medication of the Month

• Aspirin

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