Recognizing Normal Variations and Artifacts on an EKG

While identifying pathological findings is essential, recognizing normal variations and artifacts is equally important to prevent misdiagnosis. This article explores several common normal variations and artifacts encountered during EKG interpretation, providing detailed insights to help clinicians distinguish between benign patterns and true abnormalities.

Normal Variations in EKGs

Early Repolarization

Overview

Early repolarization is usually a benign EKG pattern commonly seen in healthy young adults, especially athletes. The changes are typically seen in the precordial leads. However, in some individuals, it may be associated with an increased risk of sudden cardiac death, making accurate recognition vital.

Characteristics

• J-Point Elevation: A subtle elevation of the J-point, which is the junction between the end of the QRS complex and the start of the ST segment.
• Upwardly Concave ST-Segment Elevation: The ST segment shows a concave upward elevation.
• Concordant T-Waves: Upright T-waves that are in the same direction as the QRS complex.
• J-Point Notching: A small notch at the J-point may be present.

Differentiation from Pericarditis

Early repolarization can mimic pericarditis but can be distinguished by:

• Absence of PR Segment Changes: Unlike pericarditis, early repolarization does not exhibit PR depression in most leads or PR elevation in aVR and V1.
• Stable Pattern Over Time: Early repolarization patterns are usually consistent and do not evolve, whereas pericarditis shows dynamic changes.
• Lack of Clinical Symptoms: Patients are typically asymptomatic, whereas pericarditis presents with chest pain.

Non-Specific ST-T Changes

Overview

Non-specific ST-T changes are subtle alterations in the ST segment and T-waves that do not meet criteria for specific cardiac disorders.

Characteristics

• ST-Segment Deviations: Slight elevations or depressions that are not indicative of a particular condition.
• T-Wave Changes: Relatively flat or minimally inverted T-waves.
• Distribution: These changes can occur in one or multiple leads.

Clinical Significance

• Common Causes: Can result from electrolyte imbalances, medications, or be a normal variant.
• Interpretation: Should be considered in the context of the patient’s clinical history and symptoms.

Juvenile T-Waves

Overview

Juvenile T-waves refer to negative T-waves in the right precordial leads (V1-V3) seen in children and adolescents, sometimes persisting into young adulthood.

Characteristics

• Inverted T-Waves: Negative T-waves in leads V1 to V3.
• Symmetry: Typically symmetrical and shallow.

Differentiation from Pathological T-Wave Inversions

• Age Consideration: Normal in younger individuals; persistence into adulthood is a benign variant.
• Clinical Correlation: Absence of symptoms or risk factors for heart disease supports a benign interpretation.

S1S2S3 Pattern

Overview

The S1S2S3 pattern is characterized by S waves in leads I, II, and III and is often a normal finding.

Characteristics

• Presence of S Waves: Prominent S waves in all three limb leads.
• Normal Variant: Common in young, healthy adults.

Clinical Significance

• Differential Diagnosis: Must be distinguished from conditions like right ventricular hypertrophy or pulmonary embolism, which may present similarly but are associated with clinical symptoms.

Changes Due to Hyperventilation

• Effects on EKG: Can cause ST-segment depression and T-wave inversions.
• Mechanism: Alterations in autonomic tone and electrolyte shifts during rapid breathing.
• Clinical Relevance: temporary changes that may mimic more serious conditions.

Changes Due to Hyperventilation or Large Carbohydrate Meals

• Effects on EKG: May lead to transient ST-T changes.
• Mechanism: Postprandial metabolic changes affecting cardiac repolarization.
• Clinical Relevance: temporary changes that may mimic more serious conditions.

Artifacts in EKG Interpretation

Artifacts are extraneous markings on the EKG tracing that are not generated by the heart’s electrical activity. Recognizing artifacts is crucial to avoid misdiagnosis.

Tremor Artifacts

Causes

• Muscle Tremors: Conditions like Parkinson’s disease can cause rhythmic muscle activity.
• Shivering: Due to cold or fever.

Appearance on EKG

• Erratic Baseline: Wavy or fuzzy baseline mimicking arrhythmias like atrial flutter.
• Identification: Normal P-waves and QRS complexes may be visible amidst the artifact.

Differentiation

• Consistency: True arrhythmias will have consistent patterns, whereas artifacts are irregular.
• Patient Observation: Noting tremors or shivering during EKG recording.

Artifacts from Patient Movement

Causes

• Physical Activity: Combing hair, brushing teeth, or other movements during EKG recording.

Appearance on EKG

• False Tachyarrhythmias: Rapid, irregular waves that may mimic ventricular tachycardia.
• Identification: Presence of normal complexes within the artifact; correlation with patient activity.

Skeletal Muscle Interference

Causes

• Voluntary Muscle Contractions: Tensing muscles can introduce noise.
• Involuntary Movements: Such as spasms or twitches as in shivering.

Appearance on EKG

• Baseline Distortions: Irregular, high-frequency noise superimposed on the tracing.
• Identification: Artifact is often localized to specific leads corresponding to the area of muscle activity.

Equipment Issues

Causes

• Poor Electrode Contact: Due to dried gel, oily skin, or hair.
• Faulty Leads: Damaged cables or connectors.
• Machine Malfunction: Calibration errors or defective hardware.

Appearance on EKG

• Unstable Baseline: Wandering or drifting baseline making interpretation difficult.
• Sudden Changes: Abrupt shifts or loss of signal in one or more leads.

Resolution

• Equipment Check: Ensuring all leads are properly connected and the machine is functioning.
• Skin Preparation: Cleaning the skin and reapplying electrodes as needed.

An interesting question: If you see a flat line, how do you know if it is because of sinus arrest or a third degree block or a disconnected lead?

A flatline could be seen in one of the three conditions:

• When a lead is connected to the chest, there is usually a “noise” even when it appears that the recording is a flat line- we would see some degree of activity because of reasons such as interference from other muscles, poor electrode contact from skin oil/ hair, etc. A perfectly flat line should prompt the consideration of a disconnected lead.
• A flat line with small deflections may suggest a third degree heart block with asystole (the deflections being the p-waves) while a flat line would suggest sinus arrest.

Unstable Baseline (Baseline Wander)

Causes

• Respiration: Deep breathing can cause the baseline to move up and down.
• Movement: Shifting position or talking during the recording.

Appearance on EKG

• Slow Oscillations: The entire tracing appears to undulate over several seconds.
• Identification: Baseline wander is typically synchronized with respiratory cycles.

Management

• Breath Holding: Asking the patient to hold their breath briefly can stabilize the baseline.
• Comfortable Positioning: Ensuring the patient is relaxed and still.

Understanding and recognizing normal variations and artifacts in EKGs are essential components of accurate interpretation. By being aware of these common patterns and their characteristics, clinicians can differentiate between benign findings and true abnormalities, thereby improving diagnostic accuracy and patient care.