Wednesday, 22 September 2021

Orientation of ECG Leads

On the electrocardiogram, leads are the tracing of the electrical potential difference between two points, either two electrodes (bipolar leads) or a virtual point and an electrode (unipolar leads).

It is important to know leads should not be analysed separately but as a whole, as each lead is a different point of view of the same electrical stimulus.

It is the name given to the electrocardiogram leads that are obtained from the electrodes placed on the limbs. 

This leads provide electrocardiographic data from the frontal plane (not from the potentials which are directed forward or backward).

Limb leads are grouped into bipolar leads - also known as classic or Einthoven leads - and augmented unipolar leads.

Electrocardiogram Standard Bipolar Leads:

  • Lead I: potential difference between right arm and left arm. Vector oriented to 0º
  • Lead II: potential difference between right arm and left leg. Vector oriented to 60º.
  • Lead III: Potential difference between left arm and left leg. Vector oriented to 120º.

Triangle and Einthoven’s law: the three bipolar leads form what is called the Einthoven’s triangle (named so after the inventor of the electrocardiogram). These leads maintain a mathematical proportion explained by the Einthoven’s law, which says: II = I + III.

Unipolar Leads

On the electrocardiogram, the unipolar limb leads register the potential difference between a theoretical null point at the centre of the Einthoven’s triangle and the electrode of each extremity, thus allowing us to know the absolute potential in that electrode.

These leads were initially named VR, VL and VF. The V stands for Vector and R, L and F stand for Right, Left and Foot. Afterwards a lowercase a was added, which stands for augmented (present time unipolar leads are augmented with regard to the initial ones).

  • aVR: right arm absolute potential, vector oriented at -150º.
  • aVL: left arm absolute potential, vector oriented at -30º.
  • aVF: left leg absolute potential, vector oriented at 90º.

Precordial Leads (Chest Leads)

They are unipolar leads, they register the absolute potential of the point where the electrode of the same name is placed. There are six precordial leads. They are designated by a capital V and a number from 1 to 6.

They are the leads best suited for pinning down left ventricle abnormalities, especially of the anterior and posterior walls.

On a normal ECG, QRS are predominantly negative in leads V1 and V2 and predominantly positive in leads V4 to V6 (Rs pattern).

Precordial Leads:

  • V1: This chest lead registers potentials from the atria, part of the septum and the right ventricle anterior wall. The QRS complex is formed by a small R wave (septum depolarization) followed by a deep S wave (ventricles activation).
  • V2: The electrode for this precordial lead rests over the right ventricle wall. Therefore, the R wave is slightly bigger than in V1, followed by a deep S wave.
  • V3: it is the transitional lead between the electrocardiogram left and right potentials, as the electrode rests over the interventricular septum. The R and S waves are almost identical (biphasic QRS complex).
  • V4: The electrode for this chest lead rests over the left ventricle apex, where the walls are thicker. Therefore, it presents a tall R wave followed by a small S wave (right ventricle depolarization).
  • V5 & V6: These electrocardiogram leads are situated over the left ventricle myocardium, which has thinner walls than in lead V4. Therefore, the R wave is not as tall as in lead V4, preceded by a small q wave (septum depolarization).

Thursday, 2 September 2021

ECG Study Cards

Professional created ECG ILLUSTRATIONS: £20 Includes: 2 basic ECG pdf books. Beautiful ECG rhythm strips ECG memo cards. Plus many more. Get all these beautiful illustrations for ONLY £20 These files come in high quality pdf format, that will be sent to your email. PayPal, Revolut: Hey! You can send me money on Revolut by following this link: or bank transfer accepted.

Thursday, 26 August 2021

P axis on an ECG

 What is a normal P axis on an ECG?

The P wave represents atrial depolarisation and is the first positive deflection on the ECG. The normal P wave axis ranges from 0° to +75°. However, the link between P wave abnormalities and cardiovascular death has previously been established.

It can be normal, skewed to the left (left axis deviation, or LAD), skewed to the right (right axis deviation, or RAD), or indeterminate (northwest axis). The most important axis to determine is the QRS axis. The P wave or T wave axis, on the other hand, can be measured. Normally, the QRS axis should be between -30 and +90 degrees.

Sunday, 22 August 2021

ECG parameters in pregnancy

Normal ECG data for pregnancy, which may partially relate to changes in the position of the heart, include:

  • Atrial and ventricular ectopic rhythms.
  • Q-wave (small) and inverted T-wave in lead III.
  • Depression of the ST segment.
  • Shorter than normal, PR interval.
  • Inversion of the T-wave in the lower and lateral directions.
  • Shift to the left of the QRS.
  • The electric axis of the heart is turned to the left.
  • The heart rate is higher than normal.

Monday, 16 August 2021

Right ventricular wall infarction

With inferior AMI, a right sided ECG should be performed which would confirm an RV infarction.



Sunday, 15 August 2021

22-Lead ECG with using only 10 electrodes

The ECGmax provides not only the standard 12 leads, but also an additional ten, providing a much more comprehensive picture of the heart muscle, including its right side and posterior wall. The European Society of Cardiology guidelines recommend that these aspects be monitored whenever possible. Watch the cool 😎 video below for more information.

The benefits of a 22-lead ECG:

> 22 leads for broader diagnostics

> Posterior leads V7–V9

> Right cardiac leads V3r–V6r

> Orthogonal leads X, Y, Z, and Vectorloops

> Only 10 electrodes, extremities, and chest leads

22-lead ECG example with abnormal conduction  

22-lead ECG = 12-lead ECG, right heart,  posterior, Vector cardiogram/XYZ leads and vector loops.*

ECG System leads explained:  


Vectorloops model electrical conduction in the heart as a rotating dipole. The path of this vector's peak is spatially represented as a loop in a three-dimensional individual coordinate system. The loops correspond to the P wave, the QRS complex, and the T wave.

 With a healthy myocardium, the loops are regular and "fluid looking", as opposed to a myocardium with a dysfunction, where the conduction of the dipole is irregular and jagged.

The loops in a healthy myocardium are regular and "fluid looking," whereas in a dysfunctional myocardium, the dipole conduction is irregular and jagged.

Diagnostic Capabilities: until today, Frank’s vector ECG has represented a superior diagnostic possibility. Various ECG changes, e.g. a posterior infarct, are visible on a vector ECG but not on a classic 12-lead ECG. However, this method, although superior, has not caught on, as interpreting the 3D vector loop is extremely difficult and most literature and diagnostic teaching traditionally refers to the classic 12-lead ECG.

Cardiac Electrical Biomarkers:

 Another really cool feature:

ECGmax can also calculate the Cardiac Electrical Biomarker CEB® using the same electrodes. The CEBthree ®'s color-coded areas – normal, conspicuous, and abnormal – make it particularly easy to interpret myocardial ischemia, and the CEB® has comparable sensitivity and specificity to troponin.

   > Simple interpretation using the traffic light concept

     > Measured value is comparable to troponin

     > Fast reaction by measuring the electric field

     > High sensitivity and specificity

     > No additional electrodes required

     > Continuous value

     > Non-invasive measurement