Ulkumen Rodoplu, MD EuSEM

ELECTROCARDIOGRAPHY

Plan

A Normal ECG Basic ECG Waveform Initiation of Spread of

Electrical Activation in the Hearth

The Magnitude and Direction of the Activation Process

Activation Vectors

Introduction

- Essential tool in the investigation of heart disease.

- No cardiological assessment is complete without a 12-lead ECG.

- One hundred million ECGs are recorded worldwide each year.

History

19th century. The heart generated electricity. Augustus Waller, working in St Mary's Hospital in London:

The first systematical approach about the heart from an electrical point-of-view.

Willem Einthoven, working in Leiden, The Netherlands, invented the string galvanometer, which was much more precise than the capillary galvanometer that Waller used.

Einthoven assigned the letters P, Q, R, S and T to the various deflections, and described the electrocardiographic features of a number of cardiovascular disorders. He was awarded 1924 Nobel Prize for Physiology and Medicine for his discovery.

Initiation and Spread of Electrical Activation in the Heart

In normal circumstances the whole process begins in the sino-atrial node.

Initiation and Spread of Electrical Activation in the Heart SA Node normally

initiates activation of the atrial myocardium

AV Node transmits activation received from the SA Node to the common bundle

HIS Bundle forms the electrical connection between the atria and the ventricles

Initiation and Spread of Electrical Activation in the Heart The right and left

bundle branches run below the endocardial surfaces of their respective ventricles

The Purkinje network spreads over the endocardial surfaces of the ventricles

The Basic ECG Waveform

P wave - spread of electrical activation through the atrial myocardium.QRS Complex – spread of electrical activation through ventricular myocardium.T wave – electrical recovery of the ventricular myocardium.

Electrical Activity & ECG

P Wave

< 0.10 sec. wide < 2.5 mm. amplitude (+)……DI, II, aVF (+) (-)… aVL (-)… aVR VI , biphasic or (-)

PR interval

0.12 – 0.20 sec

QRS

Depolarisation of

ventricles < 0.10 sec. wide

T Wave

Repolarisation of ventricles

0.12-0.25 sec. wide (+)…DI, II, V2-6 (+) (-)…aVL, aVF (-)….aVR

Calculation of Rate

Activation Vectors- A vector is simply something which has magnitude and direction.

- Direction in which the arrow points represents the direction of the vector.

- Length of the arrow represents the magnitude of the vector.

- The apparent magnitude of the activation wave will depend on the direction from which it is sensed.

Polarisation and Depolarisation

- Activation is actually the process of depolarisation and the spontaneous spread of this process over the myocardial cells.

- Resting, healthy mycardial cells are polarised.

- The surface membrane of each cell has an accumulation of charges – positive ones on the outside and an equal number of negative ones on the inside.

The QRS Complex

- The central oblong is the myocardial strip.

- The arrow shows the depolarisation vector in magnitude and in direction.

- The deflection recorded by each lead is shown at the side of that lead.

A Normal 12 - Lead Electrocardiogram

ECG Derivations

Bipolar…DI, DII,DIII Unipolar…aVR, aVL, aVF Precordial….V1….V6

Precordial Electrodes

Einthoven Triangle

A Normal Vectorcardiogram

Electrical Axis

Electrical Axis-Triaxial Method

Electrical Axis- Hexaxial Method

Electrical Axis-Practical Method

I,II,III,aVF.. QRS(+).... Normal I…QRS(-), aVR…QRS(+)…RAD II,III,aVF.. QRS(-)....30º LAD

Normal ECG Leads

Normal Sinus Rhytm

Sinus Tachycardia

Sinus Bradycardia

Sinus Arrhytmia

Atrial Escape Beat

Nodal Escape Beats

Nodal Rhythm in Complete AV Block

Atrial Tachycardia

Supraventricular Tachycardia

Atrial Flutter – atrial rate 300

Atrial Flutter – 2:1 Conduction, Atrial rate 300

Ventricular Premature Contractions

Multiform VPBs

Ventricular Couplets

Ventricular Flutter

Ventricular Fibrilation

First degree AV Block

Second degree AV BlockWenckebach or Mobitz Type I

Second degree AV BlockMobitz Type II