Which parts of The Action Potential Are Represented On The ECG?

The phases of the cardiac action potential correspond to the surface ECG (ECG) (Figure). The P wave reflects atrial depolarization (phase 0), the PR interval reflects the conduction velocity through the AV node, the QRS complex the ventricular depolarization and QT interval the duration potential ventricular action.

find the sum of the two horizontal vectors and the sum of the two vertical vectors

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