Post on 07-Jan-2016
description
{ECG in Kwale
Introduction
Prepared by prof. Martin RusnakTrnava University
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http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/chest_leads.php
http://en.wikipedia.org/wiki/Electrocardiography Recommendations for the Standardization and
Interpretation of the Electrocardiogram. J. Am. Coll. Cardiol. 2007;49;1109-1127 http://content.onlinejacc.org/cgi/content/full/49/10/1109
Introduction- Resources
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I n the century since the introduction of the string galvanometer by Willem Einthoven, the electrocardiogram (ECG) has become the most commonly conducted cardiovascular diagnostic procedure and a fundamental tool of clinical practiceHistory
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the diagnosis and prompt initiation of therapy in patients with acute coronary syndromes
the most accurate means of diagnosing intraventricular conduction disturbances and arrhythmias.
recognition of electrolyte abnormalities, particularly of serum potassium and calcium,
the detection of some forms of genetically mediated electrical or structural cardiac abnormalities.
monitor patients treated with antiarrhythmic and other drugs,
preoperative assessment of patients undergoing noncardiac surgery, and in
screening individuals in high-risk occupations.
Used for16. 1. 2011
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Anatomy and Physiology
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Electrical Stimulus16. 1. 2011
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ECG Paper16. 1. 2011
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ECG Recording16. 1. 2011
Different leads result in different recordings. The waves are positive and negative.
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All Leads16. 1. 2011
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Position of the patient16. 1. 2011
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3 limb leads (I, II, and III), 3 augmented limb leads in which the Goldberger modification of the central terminal
of Wilson serves as a derived indifferent electrode that is paired with the exploring electrode (leads aVR, aVL, and aVF),
6 precordial leads in which the Wilson central terminal serves as a derived indifferent electrode that is paired with the exploring electrode (V1 through V6).
The standard 12-lead ECG
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The lead connected to the right ankle is a neutral lead, like you would find in an electric plug. It is there to complete an electrical circuit and plays no role in the ECG itself.
Limb Leads16. 1. 2011
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Standard Leads16. 1. 2011
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AVr Augmented vector right Right wrist
AVL Augmented vector left Left wrist
AVf Augmented vector foot Left foot
Augmented vectors16. 1. 2011
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AVr and AVl is known as lead l.
AVr and AVf is known as lead ll
AVl and AVf is known as lead lll
Bipolar Leads16. 1. 2011
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AVL is on the left wrist or shoulder and looks at the upper left side of the heart.
Lead l travels towards AVL creating a second high lateral lead. AVf is on the left ankle or left lower abdomen and looks at the
bottom, or inferior wall, of the heart. Lead ll travels from AVr towards AVf to become a 2nd inferior
lead Lead lll travels from AVL towards AVf to become a 3rd inferior
lead. V2 V3 and V4 look at the front of the heart and are the anterior
leads. V1 is often ignored but if changes occur in V1 and V2 only,
these leads are referred to as Septal leads. V5 and V6 look at the left side of the heart and are the lateral
leads.
Regions of the Heart16. 1. 2011
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Less muscle means less cells which means less voltage 16. 1. 2011
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The first wave (p wave) represents atrial depolarisation. When the valves between the atria and ventricles open, 70% of the blood in the atria falls through with the aid of gravity, but mainly due to suction caused by the ventricles as they expand.
Atrial contraction is required only for the final 30% and therefore a relatively small muscle mass is required and only a relatively small amount of voltage is needed to contract the atria.
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After the first wave there follows a short period where the line is flat. This is the point at which the stimulus is delayed in the bundle of His to allow the atria enough time to pump all the blood into the ventricles.
As the ventricles fill, the growing pressure causes the valves between the atria and ventricles to close. At this point the electrical stimulus passes from the bundle of His into the bundle branches and Purkinje fibres. The amount of electrical energy generated is recorded as a complex of 3 waves known collectively as the QRS complex. Measuring the waves vertically shows voltage. More voltage is required to cause ventricular contraction and therefore the wave is much bigger.
The QRS Complex16. 1. 2011
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small negative wave immediately before the large QRS complex. This is known as a Q wave and represents depolarisation in the septum.
Whilst the electrical stimulus passes through the bundle of His, and before it separates down the two bundle branches, it starts to depolarise the septum from left to right. This is only a small amount of conduction (hence the Q wave is less than 2 small squares), and it travels in the opposite direction to the main conduction (right to left) so the Q wave points in the opposite direction to the large QRS complex.
The Q Wave16. 1. 2011rusnakm@truni.sk
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the R wave represents the electrical stimulus as it passes through the main portion of the ventricular walls. The wall of the ventricles are very thick due to the amount of work they have to do and, consequently, more voltage is required.
This is why the R wave is by far the biggest wave generated during normal conduction.
More muscle means more cells. More cells means more electricity. More electricity leads to a bigger wave.
R Wave16. 1. 2011
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represents depolarisation in the Purkinje fibres.
The S wave travels in the opposite direction to the large R wave because, as can be seen on the earlier picture, the Purkinje fibres spread throughout the ventricles from top to bottom and then back up through the walls of the ventricles.
S Wave16. 1. 2011
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Both ventricles repolarise before the cycle repeats itself and therefore a 3rd wave (t wave) is visible representing ventricular repolarisation.
T Wave16. 1. 2011
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There is a brief period between the end of the QRS complex and the beginning of the T wave where there is no conduction and the line is flat. This is known as the ST segment and it is a key indicator for both myocardial ischaemia and necrosis if it goes up or down.
ST Segment16. 1. 2011