EKG Basics | How to Read & Interpret EKGs: Updated Lecture

This paragraph introduces the topic of EKG basics, emphasizing the importance of understanding the physics and physiology behind EKG readings. It uses an analogy of ventricular myocardium with electrodes to explain how electrical signals are generated and propagated through the heart tissue, leading to positive or negative deflections on an EKG. The explanation also covers gap junctions, depolarization, and the significance of the direction of positive charge flow relative to electrodes.

The speaker delves into how EKG deflections occur, explaining the concept of the heart's axis and its relation to the electrodes. It discusses how the positioning of electrodes affects the EKG's waveform, particularly focusing on lead 2. The paragraph also covers the significance of the P wave, PR segment, and QRS complex in relation to atrial and ventricular depolarization, as well as the importance of the direction of electrical activity in producing EKG readings.

This section explains the PR interval, which is the time from the start of the P wave to the beginning of the QRS complex, indicating the delay at the AV node. The paragraph also discusses the isoelectric line, which represents a lack of net electrical movement or activity perpendicular to the lead axis. It further elaborates on the mean vector of atrial depolarization and its impact on the P wave's appearance.

The focus of this paragraph is on the EKG waveforms, particularly the Q wave, which signifies septal depolarization. It also discusses the R wave, which results from the left ventricle's thicker myocardium generating a larger positive deflection. The explanation includes the role of the left and right bundle branches in depolarization and the concept of the mean QRS vector.

The speaker describes the ST segment as a flat line on the EKG, indicating that the ventricular myocardium is fully depolarized with no net movement of electrical charge. This paragraph emphasizes the importance of the ST segment in pathology and how EKG machines are designed to cancel out equal deflections, resulting in an isoelectric line when electrical activity is perpendicular to the lead axis.

This paragraph introduces the concept of EKG lead systems, explaining how they are positioned on the body and their purpose in capturing the heart's electrical activity. It details the three limb leads (Lead I, II, and III) and their respective electrode placements, creating different axes for EKG readings. The speaker also discusses how these leads provide a comprehensive view of the heart's electrical activity.

The speaker provides an in-depth analysis of EKG waveforms across different leads, noting that Lead II is commonly used in rhythm strips. It explains that while there may be slight variations due to the axis of the leads, the waveforms for Lead I, II, and III should be largely similar. The paragraph also touches on the importance of understanding the direction of electrical activity relative to the positive electrode for each lead.

This section discusses the augmented unipolar limb leads (AVR, AVL, and AVF), which are derived from the same lead system but with modified electrode placements. The speaker explains how the EKG machine switches electrodes to create different views of the heart's electrical activity. It also highlights that AVR is typically the opposite of Lead II, while AVL and AVF resemble Lead I, II, and III.

The speaker focuses on the precordial leads (V1 to V6), which are crucial for identifying various cardiac pathologies. It outlines the specific locations for placing these leads on the chest and explains that they are unipolar, meaning they can detect electrical activity moving towards or away from them. The paragraph emphasizes the importance of understanding the R wave progression and the S wave decrease from V1 to V6 for diagnosing conditions like ventricular hypertrophy.

This paragraph provides a detailed explanation of the EKG's PR interval, QRS complex, QT interval, and ST segment, including their normal measurements and significance. It emphasizes the importance of these intervals for diagnosing different cardiac conditions, such as blocks and arrhythmias. The speaker also provides a method for measuring these intervals using the EKG grid and explains the implications of their durations.