Lectura de EKG

Interpretation of EKG

Basic Reading of EKG

• The EKG represents the electrical activity of the heart, recorded between positive and negative electrodes, resulting in 12 leads.

• Understanding the cardiac conduction vector is crucial; it moves from right to left, top to bottom, and back to front. This orientation helps determine which leads should be positive or negative.

Cardiac Conduction Pathway

• The conduction starts at the sinoatrial node in the right atrium, moving to the left atrium before reaching the atrioventricular node and then downwards towards the ventricles.

• It's essential to ensure that EKG machines are calibrated correctly; standard speed should be set at 25 mm per second for accurate readings.

Components of an EKG

• Key components include waves P, Q, R, S, and T:

• P wave indicates atrial depolarization.

• QRS complex signifies ventricular depolarization.

• T wave represents ventricular repolarization.

Phases of Heart Activity

• The heart undergoes several phases:

• Isovolumetric contraction (pressure increases with constant volume).

• Ejection phase (valves open).

• Isovolumetric relaxation (valves close while muscle relaxes).

Rhythm Analysis

• In sinus rhythm:

• P waves must be positive in D2, D3, and aVF.

• Each P wave is followed by a QRS complex indicating proper conduction between atria and ventricles.

• PR interval should remain consistent between 0.12 to 0.20 seconds for normal AV conduction.

Lead Derivations Overview

• Understanding lead placements:

• Lead I connects right arm (RA) and left arm (LA).

• Lead II connects LA and left leg (LL).

• Lead III connects LL and RA.

• Each lead has specific angles associated with them for interpreting cardiac axis:

• Lead I = +0°, Lead II = +60°, Lead III = +120°.

These angles help visualize cardiac orientation on an EKG strip.

Understanding Cardiac Axis and EKG Components

Defining the Normal Cardiac Axis

• The normal cardiac axis is defined between -30º and +90º, indicating a positive complex in leads D1 and ABF.

• An axis below -30º suggests left axis deviation, potentially indicating left ventricular hypertrophy or a bundle branch block.

• Conversely, an axis above +90º indicates right axis deviation, which may suggest right ventricular hypertrophy or pulmonary pathology.

Analyzing QRS Complex Variations

• The QRS complex varies based on vector conduction; if both D1 and D2 are positive, the axis is normal (between -30º and +90º).

• If D1 is positive and D2 negative, the axis lies between -30º and -90º (left deviation); if both are negative with ABF positive, it indicates extreme right deviation.

Understanding Waveforms in EKG

• The P wave represents atrial depolarization; it should be positive in most leads except V1 and AVR. Its duration must be less than 0.12 seconds.

• The RR interval reflects conduction from the atrioventricular node; it should last between 0.12 to 0.20 seconds.

Characteristics of QRS Complex

• The QRS complex signifies ventricular depolarization; its duration should be under 0.12 seconds.

• The first negative wave is the Q wave followed by R (positive), then S (negative).

Importance of ST Segment Analysis

• The ST segment should remain iso-electric; deviations can indicate coronary syndromes with or without ST elevation.

T Wave Dynamics

• The T wave indicates ventricular repolarization; it typically aligns in polarity with the preceding QRS complex.

Monitoring EKG: Clinical Correlation

Evaluating Patient Symptoms Alongside EKG Findings

• Clinical evaluation of patients must accompany EKG monitoring for accurate diagnosis—absence of a QRS complex could indicate systole but requires patient assessment for confirmation.

Identifying Complex Characteristics

• A wide QRS suggests a ventricular origin while a narrow one indicates supraventricular origin—important for diagnosing tachycardia types.

Frequency Assessment

• Heart rate classification: bradycardia (<60 bpm), tachycardia (>100 bpm). Examples illustrate differences between ventricular tachycardia (wide complexes, fast rate) versus supraventricular tachycardia (narrow complexes).

Rhythm Consistency

• Regularity in rhythm shows predictable intervals between complexes—key for distinguishing types of tachycardias effectively.

Understanding Defibrillable and Non-Defibrillable Rhythms

Defibrillable Rhythms

• The discussion begins with the identification of defibrillable rhythms, highlighting that a high frequency and wide QRS complexes indicate potential issues. An irregular rhythm suggests fibrillation.

• Ventricular fibrillation without pulse is introduced as a critical condition characterized by disorganized electrical activity, leading to unpredictable heartbeats.

• This type of fibrillation results in a heart rate exceeding 300 beats per minute, causing hemodynamic instability due to insufficient blood flow to the body.

• Normal heart rates range from 60 to 100 beats per minute; excessively rapid rates hinder ventricular filling, resulting in ineffective pulses and inadequate oxygen delivery.

• Multiple entry circuits cause chaotic electrical activity, often associated with acute myocardial ischemia or structural coronary disease.

Ventricular Tachycardia Without Pulse

• The speaker emphasizes the importance of clinical assessment alongside monitoring; an EKG showing tachycardia must be correlated with patient symptoms for accurate diagnosis.

• Ventricular tachycardia is defined by wide QRS complexes at a rapid and rhythmic pace, leading to inefficient contractions and low cardiac output.

• The absence of detectable pulses indicates severe hemodynamic impact due to reduced oxygenation and glucose perfusion throughout the body.

• Key characteristics include dissociation between atrial and ventricular contractions, which may present as fusion or capture beats on an EKG.

Non-Defibrillable Rhythms

Asystole

• Asystole is described as complete absence of electrical activity in the heart, necessitating immediate CPR since there’s no effective blood circulation.

• Recognizing asystole involves identifying a flat line on the monitor; this indicates no cardiac contraction or pulse presence.

Electrical Activity Without Pulse

• This condition may appear normal on an EKG but lacks corresponding pulses; continuous patient evaluation is crucial despite monitor readings suggesting otherwise.

• The absence of response from the patient despite apparent electrical activity signifies critical underlying issues requiring urgent intervention.