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- Lachlan Donnet-Jones
Electrocardiogram, commonly abbreviated to ECG or EKG, is defined as “a graphic tracing of the variations in electrical potential caused by the excitationof the heart muscle and detected at the body surface” (Dorlands). An ECG monitor is the device that has the ability to read and graphically present an ECG reading (Mosby’s Dictionary of Med) via a digital monitor or printed on a strip of special graph paper designed to show the rhythm of the heart over time (Mistovich). There are many different manufacturers of ECG monitors such as Philips and Physio-Control (ASNSW Protocols). An ECG monitor allows two methods of recording electrical activity, a 4-lead reading and a 12-lead reading. The ECG readings consist of three segments; a P wave, QRS complex and a T wave. The PQRST waves are the components that create the ‘waves’ or ‘spikes’ presented on an ECG reading. Electrocardiography has an extensive history dating back many centuries as pioneers of medical science were eager to understand the electrical functionality of the heart.
History of ECG, what was before ECG?
In the year 1600 William Gilbert discovered static electricity, a discovery that would eventuate in the development of one of the most important medical inventions of all time, the electrocardiogram. In the early nineteenth century the first instruments were invented that were sensitive enough to detect small electrical currents in the heart. The first functioning electrocardiogram was created by Willem Einthoven, a Dutch doctor and physiologist, in 1903. Einthoven won the Nobel Prize in medicine in 1924 for his electrocardiogram invention.
Prior to the invention of the electrocardiogram an instrument called the string galvanometer was used to detect electrical activity, it was an earlier invention of Einthoven’s. The string galvanometer could be used to measure cardiac electrical activity in a procedure where patients would submerge three of their limbs into a saline solution creating ‘Einthoven’s Triangle”, a principle still used in contemporary electrocardiogram recording. Before both the electrocardiogram and string galvanometer were invented a device called the capillary electrometer was invented by Gabriel Lippmann in 1872. The capillary electrometer consisted of “sulphuric acid and mercury in a capillary tube with wires at each end” (WEST INDIAN MED JOURNAL). Similar to the string galvanometer Lippmann’s device requires the patient to place limbs into tubs of saline solution and was the first device to read cardiac activity using this method (WEST INDIAN MED JOURNAL). Little did these early inventers know that their inventions would go on to be used thousands of times per day at all corners of the globe with its purpose and functionality continually polished and refined over the years as is evident in modern day ECG monitors.
[Naming the waves of ECG & their genesis.pdf]
[The origins of the electrocardiogram as a clinical instrument.pdf]
Purpose & functionality
The ECG machines purpose and functionality is to provide information and understanding of the heart’s electrical functionality. (MISTOVICH) This includes information on the current rate at which the heart is beating, whether the heartbeat rhythm is regular or irregular, how strong the electrical signals are and the timing between the electrical signals.
There are two methods to procure an ECG reading, a 4-lead and a 12-lead. The main difference is the number of leads used to obtain a reading which in effect allows for a better or worse reading. They are both effective in attaining information on the hearts electrical activity, however they are different and have their advantages and disadvantages. The 4-lead method, sometimes called 3-lead, typically uses three limb-leads: RA (right arm), LA (left arm) and RL (right leg). Each lead is attached to the torso despite the lead labels indicating otherwise. The RA lead (white) is placed ‘to the right side of the anterior chest just under the clavicle at the midclavicular line’ and is the negative lead, meaning it augments the signal of the LA lead. The LA lead (black, brown or green) is placed OPPOSITE?? the RA lead and is the grounding lead. RL lead is the final lead and is placed ‘to the left lower chest at about the seventh intercostal space on the anterior axillary line’ and is the positive lead. 4-lead monitoring is useful as it is quick to apply and …
4-lead monitoring has its benefits however it cannot deliver the same level of comprehensive and detailed information that a 12-lead reading is capable of. The application of a 12-lead ECG monitor requires applying 10 leads, 4 ‘limb leads’ and 6 ‘precordial leads’.
- 4 lead
- 12 lead
- Graph paper
- Phillips, lifepak
- Other functions
[Guidelines for electrocardiography.pdf]
ECG contribution to patient assessment
ECG Monitoring is typically used following a primary assessment especially in cases where there is a suspected issue with the heart or cardiovascular system. An ECG provides paramedics with information about the electrical functionality of the cardiovascular system. This is done by analysing the electrical activity displayed on the ECG reading and observing any changes in the waveform in relation to the rate and rhythm. As well as the rate and rhythm the paramedic would note any changes in the P wave, PR intervals, QRS complex, S-T segments and the P to R ratios (REFERENCE). Through this method of analysis the sign and symptoms of a patient assumed to be having cardiac issues can be confirmed for the initial diagnosis (REFERENCE). For example during the primary assessment the patient is suspected of having a myocardial infarction and is showing symptoms of chest pain, hypotension, diaphoresis and a weak and rapid pulse the paramedic’s primary goal would be to obtain an ECG reading which can then confirm the initial assessment by virtue of the PQRST waveform. Ambulance Service New South Wales protocols provides a list of common conditions that may require ECG monitoring, the list includes: “Acute Coronary Syndrome (ACS), Dyspnoea (SOB), trauma, lowered level of consciousness (LOC), post syncope episode, cardiac dysrhythmias” and many other conditions which interfere with the hearts normal capacity to function (ASNSW Protocols).
- Provides paramedic information in a situation (subsequent to primary assessment/surgery) that may involves cardiac issues, events or abnormalities via reading the ECG reading and linking any abnormalities in the PQRST waveform to the patient’s symptoms & condition. (LOOK IN MISTOVICH, PP. 1463ish)
- Situations or indications that may require ECG monitoring include: post syncopal episode, a decreased level of consciousness, chest pain, acute coronary syndrome, shortness of breath, dysrhythmias or if any cardiac occurrence is suspected (ASNSW Skills 2011, 103.5.2).
- FOR EXAMPLES: Myocardial Infarction etc. Use a med journal/article/study?
Strengths, weaknesses & challenges faced by paramedics (critique)
An ECG monitor such as the Phillips carried by Ambulance Tasmania or the Lifepak15 carried by Ambulance Service New South Wales are incredibly versatile diagnostic tools. They are portable and can be taken into the field to patients even in challenging situations such as the small interior of a crumpled car or a in a remote bush area (ASNSW Protocols; AT Protocols). The ECG monitor allows for immediate and continuous monitoring of the electrical functionality of the heart permitting a critical assessment of the patient’s condition to be made. The paramedic can then inform the receiving hospital of the patient’s condition and allow for the necessary measures for treatment to be organised prior to the patient’s arrival. (REFERENCE)
One of the significant faults of an ECG is it can only illustrate the electrical activity of the heart, it does not tell us how well the heart is functioning mechanically (Jones, 2008).
Though there are clear benefits of using an ECG monitor in the paramedic field there are also certain weaknesses in its use such as the unreliability of consistent and accurate ECG readings. It is essential for paramedics to accurately interpret ECG readings to avoid mistaken initial diagnosis which can prove costly for patient well-being in time-critical situations. Contributing factors to inaccurate ECG interpretation include cognitive bias and heuristics (mental shortcuts) (ECG READINGS BY DOCTORS). Properly cleaning skin with swabs, removing any hair in the way and certifying that the area is dry before application of electrodes will help to increase ECG accuracy and reduce inaccuracies (MISTOVICH; ASNSW Protocols). Other environmental factors such as vehicle movement can contribute to inaccurate ECG readings by virtue of unstable leads creating artefacts. Similarly if the patient is in a combative or wrestles state it can interfere with clear ECG readings, so keeping the patient calm, reducing anxiety and eliminating stressful factors can be beneficial to both acquiring vital information and the patient’s well-being. (REFERENCE)
2011 ‘Electrocardiogram‘ inDorland’s illustrated medical dictionary, Elsevier Health Sciences, Philadelphia, USA.
2012 ‘Electrocardiogram (ECG, EKG)‘ inMosby’s dictionary of medicine, nursing, & health professions, Elsevier Health Sciences, Philadelphia, USA. Accessed: 30 March 2014, from Credo Reference
Goy, Jean-Jacques; Staufer, Jean-Christophe; Schlaepfer, Jürg; Christeler, Pierre 2013, Electrocardiography (ECG), e-book, accessed 19 March 2014, <http://UTAS.eblib.com.au/patron/FullRecord.aspx?p=1310813>.
Jones, SA 2008,ECG Success [Electronic Resource] : Exercises In ECG Interpretation / Shirley A. Jones, n.p.: Philadelphia : F.A. Davis Company, c2008., Items in the Library Catalogue, EBSCOhost, viewed 19 March 2014.
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