Introduction
In recent years, the electrocardiogram (ECG or EKG) has become a popular tool in healthcare. EKG is a diagnostic equipment used to trace the heart’s electrical activity from different angles to identify and locate any damage (McStay, 2019). The machine can also help spot abnormalities caused by medication or devices that regulate the cardiac system. The 12-lead EKG is shared within the care system because it provides more comprehensive details about the heart condition.
According to research, the EKG is the most frequently conducted cardiovascular test globally, with over 200 million EKGs performed in 2017 (McStay, 2019). This assessment can help detect an urgent need for intervention, lowering additional risk and adverse patient outcomes. Various reasons may necessitate the use of EKG. They include alterations to heart rhythm or rate, blood pressure abnormalities, palpitations, suspected heart failure or acute coronary syndrome, chest pain, and a routine health check (McStay, 2019). This paper aims to describe how EKG tracing works physiologically.
How the EKG Works
The 12-lead EKG assessment generates distinct views of the heart. These ‘views’ are known as ‘leads’; therefore, this EKG provides 12 representations of the heart (Man, 2023). This test involves the attachment of six electrodes on an individual’s chest and four on the limbs to produce the 12 leads (Man, 2023).
The electrodes then identify the transmissions generated by the heart and transfer them to an EKG machine. The machine, in turn, portrays the signals in the form of lines or waves on a computer screen or a piece of paper (Man, 2023). The type of change in the membrane potential combined with the direction in which these alterations occur shapes the structure of the EKG trace.
The Physiology of 12-Lead EKG
The heart is unique due to its electrical conduction network that enables coordinated contraction to pump blood efficiently. The cardiac cycle commences when a pulse is initiated in the sinoatrial (SA) node, the heart’s pacemaker (Man, 2023). The signal is transmitted through specific paths, including the atria, atrioventricular (AV) node, AV bundle, bundle branches, and Purkinje fibers, finally triggering ventricular contraction (Man, 2023). The EKG allows clinicians to assess this transmission activity to detect heart problems and recommend viable solutions.
The basic pattern of the heart’s electrical activity encompasses three waves. They include waves P, QRS, and T, which are prominent points on the EKG (Saclova et al., 2022). Hence, the EKG starts with the P wave, which signifies the atrial depolarization. In this case, the SA node initiates this impulse, prompting the atria to contract and channel blood into the ventricles. The P wave is usually tiny and deflects upwards on the EKG machine, indicating the spread of impulse activity across the atria (Saclova et al., 2022).
The PR interval represents the duration taken by the pulse to move from the atria to the ventricles via the AV node. This interval usually takes 0.12 to 0.20 seconds to guarantee effectively coordinated atrioventricular conduction (Man, 2023). Awareness of the standard time for each wave interval can help identify any anomalies during the diagnosis.
The end of the P wave initiates the ORS complex, which is characterized by ventricular depolarization and contraction. This complex entails three diverse waves: Q, R, and S (Wang et al., 2023). In this context, the Q wave shows an initial downward movement, the R represents the upward peak, and the S wave signifies the subsequent descending deflection (Saclova et al., 2022). The QRS complex indicates that the ventricles have become activated, which readies them for contraction to enable them to remove blood from the heart (Man, 2023).
Following the QRS wave is the ST segment, which signifies the time between ventricular depolarization and repolarization (Wang et al., 2023). Usually, this segment is isoelectric because the ventricles are constricting but not depolarizing or repolarizing. Subsequently, the T wave signifies the ventricles’ repolarization, which occurs when they resume their electrical state to prepare for the next contraction (Saclova et al., 2022). This wave is usually smooth and is represented by an upward curve on the EKG machine. Any anomalies observed in this wave’s structure can suggest different cardiac diseases.
The QT interval represents the period when the ventricles depolarize and repolarize. It comprises the QRS complex, the ST, and the T waves (Indraratna et al., 2020). Research indicates that extended QT intervals can heighten an individual’s risk of arrhythmias, resulting in severe complications such as Torsades de Pointes (Indraratna et al., 2020). The U waves are tiny extra waves that follow the T waves. Even though this wave is not always visible, it signifies that the Purkinje Fibers have been repolarized (Kihlgren et al., 2023). Any deviations in the U wave shape may imply electrolyte imbalances.
When using the EKG, an assessment of its axis can aid in diagnosis. If the axis deviates leftwards or rightwards, it could indicate underlying conditions. The QRS axis is vital to determine: a normal axis ranges between -30° and +90° (Man, 2023). Left axis deviations (LAD) occur when the QRS axis falls lower than -30°, while in the correct axis deviation (RAD), this axis is more than +90° (Man, 2023). Defects linked to LAD may include myocardial infarction, while those associated with RAD comprise ventricular ectopy, fascicular block, and right ventricular hypertrophy (Man, 2023). Thus, a thorough examination of the EKG axis can help determine any pre-existing cardiovascular issues, allowing for prompt treatment plans.
EKG is critical in detecting various abnormalities within the cardiac system. It can help detect blocks within the bundle branch since they manifest through broadened QRS complexes on the machine (Man, 2023). Such irregularities may suggest various underlying cardiac illnesses necessitating evidence-based interventions. In addition, any alterations in the ST segment can signify heart problems. The depression or elevation of ST from the normal morphology may indicate myocardial infarction, ischemia, or injury (Sun et al., 2020). Such deviations might imply an imbalance in the oxygen demand and supply in the cardiac muscle and allow for appropriate diagnosis.
Nevertheless, diverse interferences can distort the EKG tracing, resulting in wrong interpretations. For instance, incorrect lead placement, patient movement, or mechanical problems may result in the retrieval of erroneous data (McStay, 2019). This highlights the need for clinicians to identify and address interferences to ascertain the accuracy of the EKG results.
Conclusion
The 12-lead EKG is an indispensable equipment in contemporary clinical practice. The tool diagnoses cardiac problems such as arrhythmias, facilitating prompt and effective treatment approaches. Several symptoms, including chest pains, blood pressure irregularities, and heart failure, may warrant recording this EKG. Nevertheless, healthcare practitioners must receive adequate training on using an EKG to prevent interferences that can lead to wrong data and misinterpretations. Therefore, EKG will remain a critical piece of equipment in cardiology due to its efficacy in helping care providers identify and manage different heart diseases.
References
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