Overview of Topics:
12 Lead basics.
Heart disease and STEMIs.
Axes.
Hemiblocks.
Phonograms blocks.
Steady look alikes.
Electrolyte imbalances.
Lead II limitations:
While lead II is useful for determining rhythm, it doesn't provide a complete picture of the heart's activity.
Example: A patient showing normal sinus rhythm in lead II had a critical condition revealed only by a 12-lead EKG.
Comprehensive Assessment:
Paramedics need to use 12-lead EKGs as a standard practice for assessing patients.
Ideal Scenario: Apply to almost all patients.
Critical Cases: Any patient with suspected Acute Coronary Syndrome (ACS).
ACS Definition: Acute Coronary Syndrome, indicating potential cardiac issues.
Exceptions:
Trauma patients with immediate life-threatening conditions may not be candidates for immediate 12-lead EKGs.
Prioritization:
High-risk patients, such as older individuals with abdominal pain, should receive a 12-lead EKG.
Asymptomatic patients can also benefit from 12-lead EKGs to detect underlying issues.
Chest Pain Protocol:
For patients presenting with chest pain, aim to perform a 12-lead EKG within 5 minutes of arrival.
In severe cases, immediate 12-lead EKG is necessary to prevent potential cardiac arrest.
Serial EKGs:
Multiple 12-lead EKGs should be conducted to monitor changes in the patient's condition over time.
Electrode Placement:
White and green electrodes: Right arm and leg, “Clouds over grass,”
Black and red electrodes: Left arm and leg, “Smoke over fire,”
Lead Views:
Lead 3: Positive electrode on the left leg.
Lead 1: Positive electrode on the left arm; views the left lateral side of the heart.
Lead 2: Views the inferior (bottom) part of the heart.
Augmented Leads:
These leads (aVR, aVL, aVF) enhance the image for better analysis.
They average two limb leads to create a central point of view.
Lead Views:
aVR: Views from the right shoulder.
aVL: Views from the left shoulder, specifically the lateral side of the heart.
aVF: Views from the inferior aspect. (bottom) of the heart.
Placement and Views:
V1-V2: Located across the septum (or sternum), viewing the septum of the heart.
V3-V4: Positioned on the anterior chest, viewing the anterior part of the heart.
V5-V6: Placed along the side (lateral), viewing the lateral part of the heart.
Alternative Technique:
Used when a 12-lead machine is unavailable.
Involves using lead III and moving the red electrode to V1-V6 positions.
Procedure:
Set the monitor to lead III.
Move the red electrode to each V lead position (V1-V6), recording a strip at each location. Using new electrode each time.
Interpretation:
MCL leads are synonymous with V leads (e.g., MCL5 = V5).
Superiority:
A 12-lead EKG is superior to MCL, but MCL can be a valid alternative.
Skin Preparation:
Hair Removal: Use a razor to remove hair from the electrode sites.
Dryness: Ensure the skin is dry; use a towel to remove sweat, especially for patients on diuretics. Alcohol wipes work for oily patients or removing lotions.
Adhesion: Proper skin preparation improves electrode adhesion and signal quality.
Tip from a nurse I got on clincials: steri-strip (benzoin or clorhexadene) is super sticky and useful in tricky EKG situations where the electrodes won’t stick no matter what you try.
Reducing Artifact:
Minimize Movement: Run the EKG when the patient is still, possibly during brief stops in transport.
Breathing: Instruct the patient to hold still and minimize deep breaths during the reading.
Positioning: Semi-Fowler's position is generally suitable unless the patient requires lying flat.
Lead Reversal:
Check lead I for P, QRS, and T wave inversion, which suggests possible upper limb lead reversal.
R Wave Progression: Confirm the R wave is small to tall getting gradually bigger. In V1 and increases toward V6; poor progression may indicate lead misplacement.
R Wave Progression:
Normally, the R wave should be small in V1 and progressively increase in size towards V6.
The S wave will get shorter.
Abnormal R Wave Progression:
Inconsistent or reversed R wave progression may indicate incorrect lead placement.
Pathological Q Waves:
Previous myocardial infarctions (MI) can cause pathological Q waves that skew the R wave progression.
Example 1: Poor R wave progression suggests incorrect lead placement (e.g., V3 in the V1 position).
Example 2: If R wave progression is absent, double-check lead placement.
Example 3: Global negativity (inverted P, QRS, and T waves) in lead I indicates switched limb leads.
Dextrocardia:
In dextrocardia (heart on the right side), invert the lead placement to obtain a clear reading.
Flip all leads to the opposite side to accommodate the reversed heart position.
ACS Overview: ACS includes non-ST segment elevation ACS (NSTEMI) and ST-segment elevation myocardial infarction (STEMI). ACS is further described shortly in the next few paragraphs.
STEMI is typically more severe.
Occurs when a ruptured plaque causes a significant or complete coronary artery occlusion.
Early recognition and rapid response are critical (First 15 minutes are crucial)
Strong public education, AED availability, and STEMI systems of care improve outcomes.
Heart disease is the leading cause of death in the U.S.
Thrombus: Consider coronary thrombus as a likely cause of death in cardiac arrest scenarios.
Key point: When tempted to diagnose a third-degree heart block, verify if the PR interval changes. A consistent PR interval suggests it's likely not a third-degree heart block.
In the case discussed, the regular R-R interval and consistent PR interval, despite seemingly independent P waves, indicate a Mobitz Type II second-degree block.
Confirmation: Several P waves don't conduct, fitting Mobitz II criteria.
Narrow QRS Third-degree heart blocks can occur with narrow QRS complexes if the impulse originates in the AV node.
Distinguishing Third Degree Heart Block from Mobitz II:
In a third-degree heart block, there's no communication between the P waves and QRS complexes.
It's crucial to assess whether the PR interval varies.
If the PR interval remains constant, the likelihood of it being a third-degree block is very low.
If the PR interval is constant, it is more likely a Mobitz II second-degree block.
Mobitz II Characteristics (Second Degree Type II):
Some P waves are not followed by a QRS complex.
Example: One QRS gets through, then two don't, then one gets through, then two don't.
QRS Complex Width in Third Degree Heart Block:
A third-degree heart block can present with a narrow QRS complex.
This indicates that the impulse is generated in the AV node.
The block occurs around the northern part of the AV node.
The Bundle of His can still fire, resulting in a narrow QRS.
Systole
> Ventricles contract.
> Tricuspid and mitral valves are closed.
> Blood is pushed towards the pulmonary artery and aorta.
> Oxygenated blood circulates.
Diastole
> Tricuspid and mitral valves open and ventricles fill.
> Aortic and pulmonary valves close.
> Atrial kick
> Represented by the P wave on an ECG, helps overfill the ventricles.
> Overfilling the ventricle is valuable because of the Starling principle (increased stretch leads to stronger contraction).
Definition: The amount of blood expelled from the ventricle.
Normal EF: 55-70%.
Cardiac Output (CO) is determined by stroke volume and heart rate.
Reduced EF (e.g., 20%) is associated with heart failure and poor cardiac output.
Preload: The amount of blood returning to the heart (atria).
Drugs that reduce preload: Nitroglycerin, Morphine.
Anything that drops blood pressure reduces preload.
Afterload: The resistance the heart must overcome to eject blood into circulation.
Vasoconstriction increases afterload.
Drugs that increase afterload: Norepinephrine, Epinephrine, Dopamine.
Valves
Know what’s happening with each of the valves during Systole and Diastole.
Coronary arteries receive blood during diastole since the leaflets cover the entrances during systole.
Right Coronary Artery (RCA):
Feeds the inferior and posterior parts of the left ventricle, and the right ventricle.
In about 50% of the population, it feeds the SA node
Almost exclusively feeds the AV node.
Implications of RCA blockage can cause AV blocks because of the irritable AV node
Inferior MI can also involve the right ventricle and posterior.
Treatment: Address possible STEMI and treat bradycardia (atropine, pacing, epinephrine, dopamine)
Left Coronary Artery (LCA):
Left Anterior Descending (LAD):
Feeds the anterior wall of the left ventricle.
Blockage here is often called the "widowmaker."
Also feeds the right and left bundle branches; blockage can cause bundle branch blocks.
Left Circumflex (LCX):
Feeds the lateral and some posterior parts of the left ventricle.
Left bundle branch blocks + chest pain are red flags = needs to go to the cath lab fast. (Buzzwords! Be sure to say “presumably new LBBB”)
Vessels can expand to feed areas not receiving enough blood, but this is a long-term adaptation. Blockage can lead to arrhythmia (possibly junctional escape rhythms).
Left Bundle Branch Block (LBBB) gets more attention because it skews the ST segment, masking STEMI, and because the left bundle branch is the bigger player.
LBBB may suggest an impending STEMI/blockage - this is something we need to bring attention to consideration during differential / upon arrival at ED. RBBB is still concerning and should be addressed later on by ED MD, Primary care, etc, but not an emergent issue at any time in our care typically.
ACS: An acute onset of heart-related symptoms related to the coronary vessels.
Umbrella Term: Includes STEMI, NSTEMI, and unstable angina.
Coronary Artery Disease (CAD) and Coronary Heart Disease (CHD): Chronic conditions, not acute.
MI is often referred to as a heart attack.
Ischemia: Lack of blood supply causing O2 shortage.
ECG: T wave inversion.
Injury: Cell damage due to prolonged ischemia.
ECG: ST segment elevation (STEMI).
Infarction: Irreversible cell death. Cannot regenerate itself.
ECG: Pathological Q waves (may indicate a previous MI).
Three Layers of Heart Tissue: Endocardium, Myocardium, Epicardium.
STEMI: Usually involves all three layers of heart tissues.
Plaque buildup narrows vessels.
Plaque rupture exposes collagen, leading to clot formation and acute blockage.
Stenosis: Narrowing of a vessel.
Lesion: Abnormal change in tissue, often due to a clot.
Cardiac Catheterization (Cath): Procedure to access coronary arteries (diagnostic or interventional).
Stress Test: “Stressing” the heart out in a controlled enviornment to assess severity or presence of blockage. Can be a physical test where the patient is running on a treadmill or doing exercise, or can be a chemical stress test.
Stent (or Balloon): Device to open blocked vessels.
Not the same as a balloon pump (for cardiogenic shock).
Coronary Artery Bypass Graft (CABG): Surgical rerouting of blood vessels to bypass blockages. A triple or quadruple bypass is a type of CABG.
More on ACS
Don't exclude people outside typical parameters for ACS.
Age:
Women over 55.
Men over 45.
High blood pressure or high cholesterol: Increases the probability of ACS.
Diabetes:
Causes vessels to narrow.
Connected to hypertension.
More prone to vascular disease.
Unhealthy Lifestyle: Increases risk.
Family history: Increases risk.
Classic Symptoms:
Chest pain (but can be absent).
Jaw pain.
Levine's sign (clutching chest).
Atypical Categories:
Females.
Elderly.
People with diabetes.
Silent MI: Symptoms aren't chest pain related.
Nausea.
Weakness.
Women notably present different during cardiac episodes across medical studies from every country. Dehnert told a story of a family member having an MI and the only symptom being intense fatigue. Some women present with heavy fatigue, minor GI symptoms, or other very vague symptoms that seem unrelated to cardiac issues at first glance.
Basic Checks:
Chest pain.
Shortness of breath.
Nausea.
Document if denied or present.
Chest pain or discomfort when the heart doesn't get enough oxygen.
It's a symptom, not a disease.
Usually caused by CHD (Coronary Heart Disease) or CAD (Coronary Artery Disease).
Also referred to as exertional angina.
Chest pain upon exertion.
Predictable.
Example: Chest pain when walking up stairs that resolves with rest.
Does not resolve with rest and/or nitroglycerin.
Very concerning; it is ACS.
Chest pain on exertion (stable angina): 70-85% blockage.
Chest pain at rest: Approximately 90% blockage.
Chest pain after nitroglycerin: Likely 100% blockage.
Blood vessel spasms, causing it to narrow.
Can occur at rest.
May resolve with nitro or on its own after the spasm stops.
Spasming causes stenosis (narrowing).
Vitals can vary widely:
Tachycardia or Bradycardia.
Hypertension or Hypotension.
Don't rule out ACS based solely on vitals.
EKG never rules out ACS; it only rules it in.
You can have a heart attack even with a "clean" EKG.
Approximately 50% sensitive, meaning it only picks up about half of heart attacks.
Non-MI conditions can mimic MIs.
Highly specific: if a STEMI is seen, it is likely there.
Identifies MI quickly, unlike labs like troponin, which can take up to 6 hours.
Can identify other complications and blockages.
Locate the J point (where the QRS ends).
Measure one small box over from the J point to assess elevation.
Each small box is 1 millimeter.
1 millimeter elevation is enough to call it elevated, except in V1, V2, or V3.
In V1, V2, or V3, at least 2 millimeters of elevation is needed.
Must be in two or more related leads (anatomically related areas of the heart).
Elevation only in lead II (inferior) is not enough to call STEMI.
Need elevation in another inferior lead like AVF.
V1/V2 (septum) and V3/V4 (anterior) are in very similar area, so elevation enough to call STEMI
To evaluate rhythm, look also at the AVR. Usually electricity flows AWAY from AVR, so if electricity is flowing TOWARDS AVR, there is likely an issue with the ventricles.
Evaluate Leads One, Two, and Three. Impulses usually travel TOWARDS these leads, so if the impulses are traveling AWAY from these leads there is likely issues with the ventricles.
"I See All Leads"
Inferior: II, III, aVF
Septal: V1, V2
Anterior: V3, V4
Lateral: I, aVL, V5, V6
Septal and anterior MIs do not have reciprocal changes.
Lateral STEMI: Often has inferior reciprocal changes.
Inferior STEMI: Often has reciprocal changes in lateral leads.
Posterior STEMI: You don't usually see elevation from normal ECG, so it is hard to notice. You might see T wave inversion in leads. Commonly seen in Inferior STEMIs due to the artery that feeds the inferior also needing
To check, move V4 to the right side of the chest (V4R).
Elevation in V4R is indicative of right ventricular infarction.
Do not give nitro if there is right ventricular involvement.
Run right side every time you see an inferior is when I would say to do it whenever there's an inferior
If you suspect the posterior: Move V5 and V6 beneath the scapula; these become V8 and V9. If you see elevation there, that indicates posterior.
Recommend that you should take B4, move it over here, and take B5 and B6, move it around the back. Run your 12 lead 1 more time, and now you will have obtained a 15 lead because of the 3 extra views.
In general, fluids are not given as a treatment for ACS. Fluids will increase the preload and overall workload on an already overworked pump (heart) that is potentially broken or about to break (go into cardiogenic shock)
Nitro lowers preload, get nitro and aspirin on board asap.
Don't give fluid boluses unless the patient is hypotensive.
Downward deflection at the start of the QRS.
Must be able to identify!
Big Q wave suggests likelihood of being a pathological Q wave. Normal waves are small.
More than one little box wide.
More than 1/3 the height of the R wave.
When you see pathological Q waves and ST segment elevation, there is cell injury and tissue death happening in real time. This is an emergency.
Key takeaways:
Stay and play until you can get aspirin and nitro on board, or until you can get proper ACLS protocols underway.
Do not waste time on arrests getting IV access - IOs are great and take little to no time.
When you get to a point where all you can do is just “work the call” i.e. continue compressions and pushing meds, then you can think about transport.
Those first 15 (or less, if you’re speedy) minutes are crucial for compressions, airway, aed, access, and interventions to begin.