Cardiac Rhythms and EKG Interpretation MS unit 5

Introduction to Cardiac Rhythms and EKG Interpretation

• Course Structure: The material covers Chapter 24 (Occlusions and Disorders) and Chapter 25 (Rhythms and Electricity). Due to the importance of memorization, the first section of Chapter 25 is covered early, followed by Chapter 24, with a return to Chapter 25 later.
• Study Objective: Students must master the basics of the normal cardiac cycle to identify abnormalities accurately in patients.
• Terminology:     * EKG/ECG: Both terms are interchangeable and refer to the recording of the electrical activity of the heart. These are usually performed using a 12-lead or 18-lead system.     * Arrhythmia/Dysrhythmia: These terms are used interchangeably to describe abnormal heart rhythms.
• Electrical vs. Mechanical Activity:     * Every cardiac event involves an electrical trigger followed by a physical (mechanical) action.     * Depolarization (Electricity): Corresponds to Depress or Contract (Mechanical). This is when the heart muscle squeezes.     * Repolarization (Electricity): Corresponds to the "RRR" mnemonic: Relax, Refill, Repolarize (Mechanical).
• EKG Measurement Tools:     * Calipers: Tools used to measure specific time frames and intervals on the EKG's red lined paper.     * The paper consists of individual small boxes representing specific time durations. At this introductory level, students are not required to know the exact time value of every small box, but they must know that these boxes provide the basis for rhythm measurement in advanced EKG classes.

The Cardiac Cycle and EKG Waves

• Single Cardiac Cycle: Represented on page 405 of the text, this covers a single heartbeat and reflects both electrical firing and mechanical response.
• Wave Components:     * $P$ Wave: The first wave in the cycle.         * Mechanical Action: Atrial contraction.         * Electrical State: Atrial depolarization.         * Electrical Origin: This is when the $SA$ node (Sinoatrial node) fires.     * $QRS$ Complex: A larger wave structure consisting of a downward dip ($Q$), a tall peak ($R$), and a return/dip ($S$).         * Visual Mnemonic: When viewed upside down, the $R$ peak resembles a "V," which signifies it is all about the Ventricles.         * Mechanical Action: Ventricular contraction.         * Electrical State: Ventricular depolarization.         * Conduction Path: The impulse travels from the $AV$ node (Atrioventricular node) through the ventricles.         * Atrial State during $QRS$: While the ventricles contract, the atria are relaxing and refilling to maintain pressure.     * $T$ Wave: The wave found at the end of the cardiac cycle.         * Mechanical Action: Ventricles are refilling and relaxing.         * Electrical State: Ventricular repolarization.         * Purpose: Prepping the heart for the next electrical impulse.

EKG Segments and Clinical Implications

• Intervals and Segments: Various measurements exist, including the $PR$ interval, $QRS$ interval, $QT$ interval, and the $ST$ segment.
• The $ST$ Segment: The short line connecting the end of the $S$ wave to the beginning of the $T$ wave.     * STEMI (ST Elevated Myocardial Infarction): A specific and critical type of heart attack.     * Identification: On an EKG, the $ST$ segment will "jump up" or be elevated above the baseline (isoelectric line) toward the peak of the $R$ wave.     * Hospital Protocol: A "Code STEMI" is called when an EKG confirms this elevation in a patient presenting with symptoms like chest pain.

Determining Cardiac Rhythms: The Stepwise Process

• Conceptual Distinction:     * Rhythm: Relates to electricity; the pattern of the cardiac cycle.     * Rate: Relates to the heart rate or mechanical "beat"; the physical squeeze/pump of the ventricles.
• The Three Essential Assessment Questions: While there is a six-step process on page 407, students must memorize the first three:     1. Is the rhythm regular or irregular?: Look for a consistent pattern in the electrical activity.     2. What is the heart rate?: Determine if the rate is:         * Bradycardia: Slow rate.         * Normal: Standard rate.         * Tachycardia: Fast rate.     3. Is there a $P$ wave for every $QRS$ complex (and vice versa)?: These waves should be "buddies" and match up to ensure the atria and ventricles are working in coordination.

Educational Resources

• Khan Academy: Recommended for visuals of cardiac activity.
• RegisteredNurseRN.com (Sarah): Recommended for clear explanations and nursing-specific EKG study material.

Questions & Discussion

• External Guest (Skills Assistant): Announced a blood drive taking place next Friday. Students can sign up with their name, phone number, and email. If a student does not know their blood type, the drive staff will identify it for them. The assistant is located in Miss Kat’s cosmetology class for those who wish to sign up later.
• Student Experience Discussion: The instructor noted that third-term students recently participated in an intensive resuscitation event at a county ER. The students had to perform one hour of "bag only" compressions. The instructor used this to emphasize the importance of staying "CPR ready" at all times.
• Specific Inquiry regarding EKG Boxes: A student asked if "sterile points" or specific boxes represent four seconds. The instructor clarified that the boxes represent time increments, which will be counted and measured in advanced classes using calipers.