What can we learn from this 3-channel ECG?
A sinus rhythm can be seen in the left half of the image, which merges into a ventricular tachycardia on the right. The QRS complexes of the VT change their shape and polarity, this is called polymorphic.
The question is: can this be called TdP (Torsade de Pointes) tachycardia or not? The clear answer is: no! A polymorphic VT may only be called TdP if there is a prolonged QT/QTc duration in the native rhythm. This is obviously not the case here. Therefore, the term polymorphic VT is retained here

This ECG was sent to me by a friend, I don't know if he did it himself. The question was whether a heart attack can be recognized here.
The patient is a 55-year-old man who has typical angina pectoris lasting more than 1 hour.
What can you answer?

This ECG (3 rhythm strips) initially shows a sinus rhythm with 1st degree AVB grade I and wide QRS complexes (presumably RBBB pattern). A PAC (P-wave premature, different form than in sinus rhythm) appears approximately in the middle of the ECG, this is not conducte . Due to the strong prematurity, this is not surprising. But why is the 2nd PAC also blocked? The answer can be found inthe second picture.

Sometimes in a simple 1-lead ECG strip, various interesting ECG phenomena can be recognized, such as here.
One could briefly look over the ECG, make the diagnosis of ventricular bigeminus and then be satisfied.
On closer inspection, however, 3 questions arise:
1. Is the P wave behind the PVC a sinus node P or an atrial extrasystole?
2. + 3. after one comes to the conclusion that it is a sinus node P: why is it not conducted and why is the PP distance smaller when there is a QRS complex in between than when there is not.

Atrial fibrillation is a very common arrhythmia, affecting hundreds of millions of people worldwide. The diagnosis of atrial fibrillation is of great importance, as the timely initiation of oral anticoagulation can in many cases significantly reduce the risk of embolism (which is associated with this arrhythmia).
The risk of cardiac embolism is particularly high in the presence of paroxysmal atrial fibrillation, in which there is frequent alternation between sinus rhythm and atrial fibrillation.
Such a sequence is recorded here in a 3-lead ECG.

This 3-lead ECG comes from an 80-year-old gentleman who went for a cardiological examination after a syncope.
The ECG shows a sinus rhythm with wide QRS complexes, the QRS morphology in lead I suggests an LBBB, heart rate here just under 60 bpm. After 3 sinus node beats there is a pause of just under 2 seconds.
There are no P waves during this pause. Then sinus rhythm again for 6 beats, followed by a pause of just under 3 seconds, then sinus rhythm again.
How can the pauses be explained?

This ECG is from a 65-year-old woman who had previously had no cardiac abnormalities but has now suffered several syncopes within 2 weeks. During the last syncope she suffered a fracture of the left femur.

Here we see a 30 s long strip of a 1-lead ECG rhythm strip, recorded with a modern Smartwatch (Apple watch). The ECG has been graphically processed for better visualization. The paper speed is 25 mm/s as usual. The lead shown corresponds to ECG lead I of the limb leads.

Especially in the social media, one sees again and again similar EKGS like the one shown here with the question: What type of AV block is present here? 2nd degree AVB block type I (Wenckebach) or type II (Mobitz)? It is neither one nor the other!
Here, a PAC can be seen under the blue arrow, which is not conduced because the AV node is still refractory (the refractory period of the AV node depends on the preceding heart rate). Therefore, it is not an AV block, but a physiologically non conducted PAC.