Topic: Electrocardiograph (ECG)

I. Introduction

• Elec­tro­car­dio­graph (ECG): A machine used to obtain an elec­tro­car­dio­gram.
• Elec­tro­car­dio­gram (ECG): A graph­i­cal rep­re­sen­ta­tion of the elec­tri­cal activ­i­ty of the heart dur­ing a car­diac cycle.
• Stan­dard ECG: Typ­i­cal­ly uses three leads:
  • One to each wrist.
  • One to the left ankle.
• Detailed Eval­u­a­tion: May involve mul­ti­ple leads attached to the chest region.
• Focus: These notes focus on the stan­dard three-lead ECG.

II. ECG Waveform and Components

• Each peak in the ECG is labeled with a let­ter from P to T, cor­re­spond­ing to spe­cif­ic elec­tri­cal activ­i­ty.

A. P‑wave

• Rep­re­sents: Elec­tri­cal exci­ta­tion (depo­lar­iza­tion) of the atria.
• Leads to: Con­trac­tion of both atria.

B. QRS Complex

• Rep­re­sents: Depo­lar­iza­tion of the ven­tri­cles.
• Ini­ti­ates: Ven­tric­u­lar con­trac­tion.
• Con­trac­tion Start: Short­ly after the Q wave.
• Marks: The begin­ning of sys­tole (ven­tric­u­lar con­trac­tion).

C. T‑wave

• Rep­re­sents: Return of the ven­tri­cles from the excit­ed to the nor­mal state (repo­lar­iza­tion).
• Marks: The end of sys­tole.

III. Clinical Significance

• Heart Rate Deter­mi­na­tion: Count the num­ber of QRS com­plex­es with­in a giv­en time peri­od.
• Nor­mal ECG: ECGs from dif­fer­ent indi­vid­u­als have rough­ly the same shape for a giv­en lead con­fig­u­ra­tion.
• Devi­a­tions: Devi­a­tions from the nor­mal shape indi­cate pos­si­ble abnor­mal­i­ties or dis­eases.
• Clin­i­cal Impor­tance: ECG is of great clin­i­cal sig­nif­i­cance in diag­nos­ing heart con­di­tions.