PCTH - Cardiac Ischemia and STEMI Bypass

Question 1

Classification of nitroglycerin and forms it can be found in?

Answer 1

• classified as a nitrate - first used to manage angina pectoria (1879)
• commonly found in spray (most common form in pre-hospital), tablet, ointment and patch forms (patch usually for chronic pain)

Question 2

Dose of one spray of nitro

Answer 2

0.4mg

Question 3

Onset and elimination time for nitro

Answer 3

Onset: 1-4 min

Elimination: up to 10 min

Question 4

Side effects of nitro

Answer 4

headache

hypotension

increased HR

Question 5

Preparing the nitroglycerin

Answer 5

• Go through your 6 rights
• do not shake bottle - you do not want the tube in the spray to fill with bubbles (otherwise you wouldn’t get the full dose)
• point away and sprat a couple times to prime plunger
• 2 fingers width away from the mouth
• deliver SL

Question 6

What is the mechanism of action for nitroglycerin?

Answer 6

• Vasodilation
• reduces preload and afterload to the heart, which causes a decrease in cardiac work, reducing anginal symptoms secondary to demand ischemia

Question 7

Acetylsalicylic acid (ASA) classifications

Answer 7

• analgesic (it’s an NSAID so inhibits prostaglandin synthesis)
• anti-pyretic (so as above^)
• platelet inhibitor
  
  • platelets when activated to form a plug when there is damage will also secrete thromboxane A2
  • thromboxane A2 stimualtes vasoconstriction which reduces blood flow at the site
  • ASA prevents the production of thromboxane A2 thus slowing the aggregation (clumping) of platelets (via inactivating COX-1 which is needed for TXA2 synthesis)
• ASA given within the first 30 minutes of cardiac ischemia will reduce mortality by 30%

Question 8

Dose, onset, and duration of action of ASA

Answer 8

Dose: 80-81mg per tablet

Onset: ~30 min

Duration: 12-24 hours +

Question 9

Steps for delivering medication for ASA

Answer 9

6 rights

2 x 80/81mg tablets

chew into a paste and swallow

Question 10

Cardiac Ischemia Directive

Indications

Conditions

Contraindications

Answer 10

Indications: suspected cardiac ischemia

Conditions:

• ASA: ≥18 years, unaltered LOA, able to chew and swallow
  
  • unaltered LOA because they need to answer OPQRST, hx taking, and chew meds
• Nitroglycerin: ≥18 years
  
  • unaltered LOA
  • HR 60-159 -due to vasodilation properties (and likely if HR is faster than that, it may be something else going on like SVT)
  • SBP Normotensive
  • Prior history of nitro use OR IV access obtained

Contraindications:

• ASA:
  
  • allergy or sensitivity to NSAIDs
  • If asthmatic, no prior use of ASA
  • Current active bleeding
  • CVA/TBI in the previous 24h - consider recent falls, altered LOA, slurred speech, inappropriate behaviour
• Nitroglycerin:
  
  • allergy or sensitivity to nitrates
  • Phosphodiesterase inhibitor use within the previous 48 hours
  • SBP drops by 1/3 or more of its initial value after nitroglycerin is administered
  • 12-lead ECG compatible with Right Ventricular MI

Question 11

Cardiac Ischemia Directive

Treatment

Answer 11

1) Consider ASA: PO route, 160-162 mg (max dose 162mg). Max # of doses: 1

2) Consider 12 lead ECG acquisition and interpretation for STEMI

3) Consider nitroglycerin

• STEMI:
  
  • ​SBP: ≥100mmHg
  • Route: SL
  • Dose: 0.3mg OR 0.4 mg
  • Max single dose: 0.4mg
  • Dosing interval: 5 min
  • Max # of doses: 3
• Not a STEMI:
  
  • ​SBP: ≥100mmHg
  • Route: SL
  • Dose: 0.3mg OR 0.4 mg
  • Max single dose: 0.4mg
  • Dosing interval: 5 min
  • Max # of doses: 6

Question 12

Cardiac Ischemia Directive

Clinical Considerations

Answer 12

a) Suspect a Right Ventricular MI in all inferior STEMIs and perform at minimum V4R to confirm (ST- elevation ≥ 1mm in V4R).
b) Do not administer nitroglycerin to a patient with Right Ventricular STEMI.
c) IV condition applies only to PCPs authorized for PCP Autonomous IV.
d) Apply defibrillation pads when a STEMI is identified.
e) The goal for time to 12-lead ECG from first medical contact is < 10 minutes where possible.

Question 13

What definitions can fall under “suspected cardiac ischemia” in the Cardiac Ischemia Directive?

Answer 13

a) any pt experingin chest pain consistent with that caused by cardiac ischemia (includes equivalents as well: radiating pain to arm/jaw/back, diaphoresis, nauseous, SOB, pressure, crushing pain)

OR

experiencing his/her typical angina/MI pain

OR

Cardiac ischemia is suspected (via 12 lead diagnostiic)

Question 14

Why is NTG dosing in STEMI decreased (3 doses instead of 6)?

Answer 14

• NTG causes vascular dilatation, increased hepatic perfusion, & liver is the site of drug metabolism
• increased perfusion leads to increased metabolism of ASA & other cardioprotective drugs which makes it less effective therefore you want to limit NTG doses in STEMI

Question 15

Assessment for cardiac ischemia calls

Answer 15

OPQRST

relief (any treatment/own medication taken prior to EMS arrival)

vitals

12 lead

Question 16

“Prior history of nitroglycerin use OR IV access obtained”. Define what this means and what situations would be acceptable or not

Answer 16

Prior history of nitroglycerin use:

• Either from previous calls where they’ve received nitro (from EMS or hospital)
• Previously authorized or prescribed to the patient for use by a certified Medical Doctor (includes prescribed and never used because nitro PRN (still is considered acceptable)
• NOT if they’ve used someone else’s nitro, this does not count

IV access obtained:

• IV must be initiated prior to the administration of nitroglycerin in first time suspected cardiac ischemia patients.
• If the patient already had an IV in place (i.e. outpatient), the IV would need to be assessed for patency and once confirmed, would allow for first time administration.
• This only applies to PCP AIV

Question 17

Why is phosphodiesterase inhibitor use within the previous 48 hours a contraindication for nitro?

Answer 17

• PDE5 is distribute in many tissues (platlets, veins, arterial smooth muscle such as in pulmonary, coronary, and systemic arteries) and acts on the blood vessels to cause narrowing
• PDE5 inhibitors (such as ED drugs) affect the cardiovascular system via vasodilation to cause increased blood flow to certain areas and decrease in BP
• Giving nitroglycerin (a vasodilator) will just exacerbate the already vasodialted vessels in those who have taken PDE5 inhibitors therefore causing a huge drop in BP

Question 18

What are some common reasons as to why phosphodiesterase inhibitors would be prescribed to patients (besides boners)?

Answer 18

pulmontary HTN (helps with lowering BP)

CHF (can cause cardiac stimulation to increase contractility of the heart and thus cardiac output)

Question 19

Why is a RVI contraindicated for nitro administration?

Answer 19

• these patients are often preload dependent (the function of the right side of the heart is often dependent on adequate venous return for appropriate filling pressures to then be able to pump blood into the pulmonary circuit and then left side of the heart)
• these people may experience significiant hypotension due to vasodilation from nitroglycerin administration
• can also further exacerbate tachycardia that is already a side effect of nitro

Question 20

How are you ruling in/out an RVI?

Answer 20

1. perform a 12 lead and if you see inferior MI….
2. then perform a 15 lead moving V4 to V4R
3. Determine if MI has RVI (which will be show via elevation in V4R) - ST elevation ≥ 1mm

Question 21

You are called to a patient complaining of chest pain. You administer ASA and nitroglycerin which fully resolves their chest pain. En route to the hospital, patient states he begins to feel his chest pain again. What are your next steps.

Answer 21

You may complete the full directive again (ensure all parameters and conditions are met) but ONLY FOR NITROGLYCERIN not ASA

Question 22

You get called to a patient for chest pain. On arrival, patient states he has taken 3 ASAs while waiting for EMS to arrive. According to your directive, how many ASA are you then allowed to give?

Answer 22

The full dose :) 160-162mg

doesn’t matter what the patient took prior to, apply the medical directive as if no care has been rendered prior to your arrival (unless it was administered by another on-duty paramedic).

ASA is a safe medication with a wide therapeutic index (effective dose without side effects can be from 80-1500mg) so additional doses will not exceed therapeutic doses and you as a paramedic can ensure that patient has taken the right amount of ASA and properly (aka chew as a paste and swallow)

Question 23

If a patient’s chest pain symptoms fully resolve prior to EMS arrival, are you allowed to complete your cardiac ischemia directive?

Answer 23

If patient meets all the parameters, administer ASA even if pain fully resolves because you only 100% know there’s no MI through bloodwork looking for elevate troponin levels so give it just in case)

If patient doesn’t have pain, no nitro (Patient must 100% have some sort of discomfort or pain on the pain scale to receive nitro)

Question 24

What is the significance of the patient’s vitals when determining whether or not to continue the cardiac ischemia medical directive?

Answer 24

If a patient’s vitals drop out of the parameters (HR, BP), the directive immediately ends and no furthr doses are administered. This still applies if the patient’s vitals return to applicable values (this is due to risk of recurrent decompensation)

Question 25

Every ____ minutes someone in Ontario suffers a cardiovascualr event.

Answer 25

7 minutes

Question 26

There are ______ STEMIs annually in Ontario in the pre-hospital setting.

Answer 26

7000

Question 27

In the pre-hospital setting, approximately ____% of STEMIs have cardiac arrests before receiving any help.

Answer 27

50

Question 28

What portion of potential MIs are STEMIs?

Answer 28

1/3

Question 29

What treatment do STEMIs require?

Answer 29

require timely perfusion of the affect side of the heart

a) Percutaneous Coronary intervention (PCI) - aka angioplasty; the preferred intervention due to treating the LT problem with increased chance of recovery, reduced risk of recurrence. Also an available option for patients that cannot receive clot busters (i.e. if bleeding, recent surgery, etc.)

b) Fibrinolysis therapy

Question 30

What is percutaneous coronary intervention (PCI)?

What is the door-to-balloon (D2B) time for a patient who is transported to a PCI center vs non-PCI center?

Answer 30

An intervention that mechanically opens the artery using a balloon. May include the placement of a stent in blocked arteries to restore blood flow

D2B for patient transported directly to PCI center: 90 minutes or less

D2B for patient transported directly to non-PCI center: 120 minutes or less

Question 31

What is fibrinolysis therapy and what is the door to needle time for this type of treatment?

Answer 31

Use of clot busting medications (thrombolytics/fibrinolytics) to breakdown the clot

30 minutes door to needle time

Question 32

Mortality is reduced by ____ when paramedics recognize and transport directly to a reperfusion facility (cath lab),

Answer 32

1/3

Question 33

How many 12-leads should you be getting?

Answer 33

minimum 3 as long as they are not diagnostic

once diagnostic, you can stop getting more 12-leads

Question 34

At what points during the call should you be getting 12 leads and what % of the time will the 12-leads be diagnostic of a STEMI if there is one?

Answer 34

1) within 10 min on scene - 30% of time STEMI will show up on first 12-lead
2) in ambulance, prior to leaving scene - 60% on second 12 lead
3) right before you arriva at hospital - 10% of the time will be showing up on third 12 lead

Question 35

STEMI Hospital Bypass Protocol

Indications

Answer 35

1) ≥18 years of age;
2) experience chest pain or equivalent consistent with cardiac ischemia or MI
3) time from onset of the current episode of pain <12 hours; and
4) the 12-lead ECG indicates an acute MI/STEMI, as follows:
* At least 2 mm ST-elevation in leads V1-V3 in at least two contiguous leads;

AND/OR

• At least 1 mm ST-elevation in at least two other anatomically contiguous leads; OR
• 12-lead ECG computer interpretation of STEMI and paramedic agrees.

Question 36

STEMI Hospital Bypass Protocol

Contraindications

Answer 36

1) CTAS 1 and the paramedic is unable to secure the patient’s airway or ventilate
2) 12-lead is consistent with a LBBB, ventricular paced rhythm, or any other STEMI imitator;
3) Transport to a hospital capable of performing PCI ≥60 minutes from patient contact;
4) Pt is experiencing a complication requiring primary care paramedic (PCP) diversion, as follows:

• Moderate to severe respiratory distress or use of continuous positive airway pressure (CPAP);
• Hemodynamic instability (e.g. due to symptomatic arrhythmias or any ventricular arrhythmia) or symptomatic SBP <90 mmHg at any point; or
• VSA without ROSC

5) The patient is experiencing a complication requiring ACP diversion, as follows:

• Ventilation inadequate despite assistance;
• Hemodynamic instability unresponsive to advanced care paramedic (ACP) treatment or not amenable to ACP management; or
• VSA without ROSC.

notwithstanding paragraphs 3, 4, 5 above, attempt to determine if the interventional cardiology program at the PCI centre will still permit the transport to the PCI centre;

Question 37

STEMI Hospital Bypass Protocol: If the patient does not meet any of the contraindications listed in paragraph 2 OR the interventional cardiology program permits the transport to the PCI centre, what are the paramedics’ next steps?

Answer 37

1) inform CACC/ACS of the need to transport to a PCI centre
2) provide the PCI center with the follow information as soon as possible:

• patient is a “STEMI patient”
• initials
• age
• sex
• paramedic’s concerns regarding clinical stability (mostly re: hemodynamics)
• ETA
• catchment area of patient pickup

3) upon arrival at PCI center, provide additional info:

• time of Sx onset
• time of ROSC, if applicable
• hemodynamic status
• medications give and procedure
• Hx of acute MI/PCI/CABG, if applicable
• A copy of the qualifying ECG; and
• A copy of the ACR

Question 38

As per the STEMI hospital bypass protocol, if you have initiated the protocl and the ECG normalizes after the initial assessment, what should you do?

Answer 38

continue to follow the STEMI bypass protocol

Question 39

STEMI Hospital Bypass Protocol

Guidelines

Answer 39

Once a STEMI is confirmed, the paramedic should apply defibrillation pads due to the potential for lethal cardiac arrhythmias.

If IV access is indicated and established as per the ALS PCS, then the left arm is the preferred site.

If the ECG becomes STEMI-positive en route to a non-PCI destination, the patient should still be evaluated under this STEMI Hospital Bypass Protocol.

If, in a rare circumstance, the PCI centre indicates that it cannot accept the patient (e.g. equipment failure, multiple STEMI patients), then the paramedic may consider transport to an alternative PCI centre as long as they still meet the STEMI Hospital Bypass Protocol.

Question 40

Common phosphodiesterase inhibitors (aka ED drugs)

Answer 40

• Viagra, Revatio (sildenafil)
• Cialis (Tadalafil)
• Levitra (vardenafil)
• Stendra (avanafil)
• Zydena (Udenafil)
• Helleva (Lodenafil)
• Mirodenafil
• Acetildenafil
• Aildenafil
• Benzamidenafil
• Zaprinast
• Icariin (a natural product)

Question 41

What are the STEMI imitators?

Answer 41

E - electrolytes (hyperkalemia)

L - left BBB

E - early repolarization

V - ventricular hypertrophy (left)

A - aneurysm (ventricular)

T - Thailand Brugada

I - inflammation (pericarditis)

O - Osborn waves (hypothermia)

N - non-atherosclerotic vasospasm

Question 42

Describe what hyperkalemia is and its role in cardiac function

Answer 42

Hyperkalemia: abnormally high level of potassium in the blood

K+ is essential for normal cardiac electrical activity; an increased amount in the ECF reduces myocardial excitability, affecting both conductive tissue and pacemaker function

Question 43

Causes of hyperkalemia may include:

Answer 43

• excessive administration of potassium
• excessive use of salt substitutes
• wide spread cell damage (eg. crush injuries, burns)
• metabolic or respiratory acidosis
• acute or chronic renal failure - eg. missed dialysis treatments (they may be confused, weak, and SOB)

Question 44

Describe potential ECG changes in patients with hyperkalemia vs those who have normal potassium serum levels.

Answer 44

Normal K+ serum: 3.5 - 5.0 mEq/L

• Hyperkalemia patients may be asymptomatic but typical ECG changes may occur including

Mild cases: <6.5 mEq/L - normal p waves; tall, tented peaked T waves (Best seen in II, III, V2, and V4)

• looks similar to hyperacute phase of STEMI evolving (so STEMI imitator)

Moderate cases: <8 mEq/L - p wave starts to flatten; prolonged PR interval

• no ST segment with peaked T waves
• widened QRS Complex
• Broad S wave in V leads
• Left axis deviation

Severe cases: >8.5 mEq/L - absent P waves, sine wave (which can be mistaken for V-tach)

VF or asystole: 10-12 mEq/L

Question 45

Examine the following 12-lead and determine what characteristics would indicate hyperkalemia?

Answer 45

tall, tented, peaked T waves (best seen in II, III, V2, V4)

Question 46

Describe what a left BBB is and how it may be a STEMI imitator.

Answer 46

Left BBB: an interruption in the left bundle branch conduction causing an unsynchronized depolarization (the LV depolarizes slightly later than the RV causing two separate depolarizations seen as a wide QRS)

• A left BBB can look like a AMI so typically people do not even attempt to diagnose an AMI in the presence of a LBBB because you just can’t tell (therefore reperfusion therapy is commonly delayed or withheld)
• Reasons why:
  
  • LBBB with or without AMI typicall presents with ST elevation
  • As Q wave patterns are altered, it is difficult to diagnose a previous MI in the presence of a LBBB

Question 47

Describe the “Sgarbossa” criteria for AMI with LBB

Answer 47

1) Concordant ST Elevation - ≥ 1mm in ANY lead(s) - SCORE 5

2) Concordant ST Depression - ≥ 1mm in V1-V3 - SCORE 3

3) Excessive Disconcordant ST Elevation - ≥ 1mm in ANY lead(s) (defined as ≳ than 25% of the depth of preceding S) - SCORE 2

This test has a 90% specificity for diagnosing an MI when a patient scores ≳3

Question 48

What is Benign Early Repolarization (BER) and who does it typically occur in?

Answer 48

• aka “high take off J point elevation”
• Typically occurs in
  
  • 1% of total population
  • young healthy males (often resolves with age)
  • chest pain patients who have used cocaine

Question 49

Benign Early Repolarization is characterized by:

Answer 49

• Notched or “slurred” J point (best seen in V4, V5, and V6)
• Concave ST elevation (best seen in inferior and lateral leads)
• No reciprocal depression to suggest STEMI

Question 50

What two conditions can often be difficult to differentiate between as they are both associated with concave ST elevation?

Answer 50

pericarditis and benign early repolarization

Question 51

Examine the following 12-lead and describe which STEMI imitator is illustrated here. Provide your rationale.

Answer 51

Benign Early Repolarization

Question 52

Describe LVH characteristics on a 12-lead and why it causes these ECG changes.

Answer 52

• Characterized by:
  
  • ST elevation in leads with deep S waves (usually V1-V3)
  • ST depression/T wave inversion in leads with tall R waves (lateral leads)
• An increase in muscle mass causes increase in the amount of depolarizing myocardial cells which results in tall R waves in V5 and deep S waves in V1
• most commonly associaed with HTN

*note: differentiating ST elevation due to LVH vs due to an AMI is difficulty due to little literature

Question 53

Describe Left Ventricular Aneurysm and how it can be a STEMI imitator.

Answer 53

• myocardial wall thinning and/or bulging
• persistent ST elevation remaining in 1 in 4 patients following a STEMI (these patients may present with chest pain and be misdiagnosed with an AMI)
• Characterized by:
  
  • ST elevation with varying morphologies (i.e. convex and concave)
  • Pathological Q waves in affected ST elevation leads
  • Inverted T wave of minimal magnitude

The absence of STEMI evolution may suggest a left ventricular aneurysm therefore serial ECGs are invaluable

Question 54

Describe what Brugada Pattern is and what could cause it.

Answer 54

Brugada Pattern: aka thailand - a rare gene mutation (function loss of sodium channels) in patients with structurally normal hearts

Typically occurs in:

• 1 in 25 000 people (high incidence in southeast Asia)
• Males (70%)
• Can occur at any age, but typically 41 y.o.

May be exacerbated by:

• fever
• hypokalemia
• medications - antiarrhythmic medications are potent sodium channel blockers

Question 55

How is Brugada Pattern characterized on a 12-lead/clinical presentation?

Answer 55

• coved or “saddle back” ST segment in V1 and V2
• Possible syncope
• No chest pain

Question 56

Define pericarditis, identify potential causes, and describe the typical demographic in whic pericarditis affects.

Answer 56

• *Pericarditis:** inflammation of the pericardium
• *Acute pericarditis:** pericardium and myocardium just beneath it are inflamed, causing repolarization abnormalities
• Typically occurs in:
  
  • young patients without cardiac risk factors but can occur in all ages
• Caused by:
  
  • viral and autoimmune causes (most common)
  • Bacterial diseases eg. TB
  • Cancer
  • Other sources of inflammation

Question 57

Signs and Symptoms of pericarditis?

Answer 57

• Chest pain - sharp, severe radiating to back, neck and jaw; often pleuritic pain, made worse by breathing
  
  • pain lasts hours to days
• Symptoms made worse by lying flat and better by sitting up
• Tachycardia
• Fever
• Weakness
• Fever/chills

Question 58

Describe how pericarditis is characterized in a 12-lead.

Answer 58

• Concave ST elevation in almost all leads (except aVR and V1)
• T wave elevation above the isoelectric line
• 90% of pericarditis cases have the above ^ ECG evidence
• since periarditis DOES NOT involve coronary artery blockage, the ST elevation will NOT be limited to leads overlying area fed by certain coronary artery (i.e. it will be widespread through many leads

Question 59

Examine this 12-lead and determine what STEMI imitator would produce such characteristics & rationale.

Answer 59

Pericarditis - widespread ST elevation (in almost all leads) & T wave elevation above isoeletric line

Question 60

Describe hypothermia

Answer 60

• Core body temp (CBT) < 35 deg
• result of decreased heat production, an increase in heat loss, or a combo of both
• “Osborn waves” may be present in an ECG when CBT reaches 30 deg
  
  • transient and will resolve when CBT returns to normal

Question 61

ECG findings for hypothermia

Answer 61

• J point elevation (“Osborn wave”) - most prominent in precordial leads
• Prolonged PR, QRS, and QT interval

Question 62

Examine the following 12-lead and determine what STEMI imitator produced such characteristics. Provide rationale.

Answer 62

Hypothermia - osborn waves present in V2, V3, and V4

Question 63

What is Prinzmetal Angina? Describe the demographic is occurs in and when it occurs.

Answer 63

• an intense spasm in a segment of the coronary artery
• an atypical form of angina characterized by ST segment elevation in a 12-lead that disappears when pain subsides
• no clear demographic and occurs anywhere in the arteries; often associated with tobacco and cocaine use
• Typically occurs:
  
  • at rest
  • early morning or late night (may awake patient)
  • in episodes lasting a few minutes (a duration long enough to cause dangerous dysrhythmias)