ECG Leads:
- Body act as a conductor of electricity; the recording electrodes in the arms, legs, and chest wall show the differences in voltage (potential) among electrodes
- Different views of the same event leads to different ECG patterns
ECG Limb Leads:
- 6 Limb leads (extremity leads) and 6 chest (precordial)
- 3 bipolar limb leads: I, II, III
- 3 augmented unipolar: aVR, aVL, and aVF
- 6 precordial leads: V1-V6
Einthoven’s Triangle:
Lead I: LA - RA
Lead II: LL - RA
Lead III: LL - LA
Remember: Lead I + Lead III = Lead II
Should double check if the R-lead in lead II = sun of the R-waves in lead I and lead III (1 + 3 = 2)
ECG Leads:
- Unipolar leads record the electrical voltage at one location relative to an electrode with close to 0 potential
- aVR + aVL + aVF = 0
ECG Limb Leads
- V1: 4th intercostal space (right)
- V2: 4th intercostal space (left)
- V3: Mid-way b/w V2-V4
- V4: Mid-clavicle line in 5th intercostal space
- V5: Anterior axillary line
- V6: Mid-axillary line
*Placement is key, but can be highly variable*
Let me know what you think and stay tuned for the next ECG thread!
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Pre-Rounding Tips 3d: How to think about Troponin? (
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Pro-Tip: If you can print out a pre-rounding sheet with the labs auto-populated, that is always helpful.
One of the most common consults from the Emergency Room to Cardiology is 'elevated troponin.'
Yes, elevated troponin can be scary, but here is the framework that I use to analyze / consider troponin.
1. Patient Presentation? 2. Patient's risk factors and prior cardiac history? 3. What is the troponin trend? 4. What does the ECG look like? 5. What are some non-cardiac reasons troponin may be elevated?
1. Patient Presentation?
In Cardiology, the clinical presentation is the most important part of the story when determining the significance of an elevated troponin! In many situations, clinical decisions (whether to pursue a LHC) may be made in the absence of having a troponin available.
Key Questions: 1. If the patient presents with chest pain, how does he/she describe it?
- Some common worrisome symptoms associated with angina. Elevated troponin in the setting of these symptoms should always be taken seriously.
a) Chest pressure, constant, sub-sternal.
b) Radiation of pain to the neck or jaw
c) Diaphoresis
d) Numbness to the left arm
e) New onset dyspnea
f) Worse with exertion, better with rest
2. What makes the pain better?
- If the patient got improvement with nitroglycerin more likely to be consistent with cardiac chest pain.
- If patient's pain improves with muscle relaxers, IV toradol, IV PPI, IV Ativan, less likely to be a cardiac etiology.
3. Has the patient had this type of pain before?
- If similar recent presentation with a negative work-up, this might be reassuring. However, you don't want to have anchor bias and should keep an open perspective.
When I was an intern, pre-rounding was one of the most stressful parts of the day. I would take too long and be inefficient. Part 1.
Now as a PGY7 (long-time, right?), here is 3 parts of my system that I use for new patients.
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1) Why is the patient here / chief concern?
- This seems like the most basic question that is often overlooked. What made the patient decide to leave his/her house to come to the hospital?
- When reading the overnight H&P, the abundance of clinical documentation can create confusion.
- Simplicity is key. What is the chief concern? Is it chest pain? Is it dyspnea on exertion? Knowing this information will help frame your thoughts.
2) What are the relevant past medical problems?
- Most patients will have chronic medical problems that will contribute to the current presentation.
- It is easy to get lost in the weeds of this presentation. In Cardiology, I typically focus on (but not limited to) coronary artery disease, atrial fibrillation, hypertension, hyperlipidemia, diabetes mellitus, history of CVA. Again, this is not all inclusive but it is a start.
- Although patients may present to the hospital with a new diagnosis, it is more likely that the presentation may be an exacerbation of a previous problem.