When does an upward pattern in an ECG occur?

An upward pattern in an ECG occurs when there is a flow of electrical activity towards the positive electrode. This upward deflection indicates that the depolarization wave, which represents the electrical activation of the heart muscle, is moving towards the electrode placed on the skin. In the traditional lead systems, positive electrodes are configured to receive signals from specific areas of the heart, and when the electrical impulse travels towards these electrodes, it results in an upward reading on the ECG trace.

The other scenarios don't produce an upward deflection. For instance, if electrical activity flows away from a positive electrode, it would lead to a downward deflection. When the heart is at rest, there is little to no electrical activity occurring, thus there are no significant upward or downward deflections. Lastly, a block in electrical conduction would typically cause abnormalities or changes in the waveform, but not consistent upward patterns unless there's a specific pattern of repolarization or ischemia involved.