ECG Telemetry Viewport (Click any cell to magnify)
25 mm/s
10 mm/mV
TELEMETRY SANDBOX STATUS
Rhythm: Sinus Rhythm
Axis: 60° (Normal)
QRS Width: Normal
ST Shift: None
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Identify Heart Rate Select one:
Bradycardia (<60 bpm)
Normal (60 - 100 bpm)
Tachycardia (>100 bpm)
Identify Cardiac Rhythm Select one:
Sinus Rhythm
Atrial Fibrillation (AFib)
Atrial Flutter
Junctional Rhythm
Ventricular Tachycardia (VT)
Ventricular Fibrillation (VF)
Identify QRS Electrical Axis Select one:
Normal Axis (0° to +90°)
Left Axis Deviation (LAD, -30° to -90°)
Right Axis Deviation (RAD, +90° to +180°)
Extreme Deviation (-90° to -180°)
Identify Hypertrophy / Enlargement Select one:
No Hypertrophy / Normal Chambers
Left Ventricular Hypertrophy (LVH)
Right Ventricular Hypertrophy (RVH)
Left Atrial Enlargement (LAE)
Right Atrial Enlargement (RAE)
Identify Infarction / Ischemia Select one:
Normal (No ST / T Wave changes)
Acute Anterior STEMI
Acute Inferior STEMI
Acute Lateral STEMI
Myocardial Ischemia (ST Dep / T-wave Inv)
Identify Blocks / Anomalies Select one:
Normal conduction / No anomalies
Left Bundle Branch Block (LBBB)
Right Bundle Branch Block (RBBB)
First-Degree AV Block (PR > 0.20s)
Wolff-Parkinson-White (WPW) Syndrome
Brugada Syndrome
Hyperkalemia (Peaked T waves)
Hypokalemia (Prominent U waves)
Creators & Developers
• Jeremias T. Balgua Jr. MD
• Darren Barley C. Terrado (PLM Med Student)
Diagnostic Review
Detail description of correct markers.
Visual Pathophysiology
Simulating this case's cardiac conduction...
Clinical Study Guide
ECG Sandbox Parameters
Conduction Simulator
75 BPM
Simulating cardiac conduction...
Heart Rate (HR)
75 bpm
QRS Axis Angle
60° (Normal)
📖 ECG Reading Guide (RAHIM Method)
A comprehensive manual on the 6 clinical categories of the RAHIM method for ECG interpretation.
⚡ 1. Heart Rate (Rate)
Heart rate represents the frequency of ventricular depolarizations. To calculate rate in a regular rhythm, count the number of large boxes (5mm squares) between consecutive R-waves (R-R interval) and divide 300 by that number: 300 / (large boxes). For irregular rhythms, count the number of QRS complexes on a 10-second strip and multiply by 6.
Normal Heart Rate
R-R spacing 3 to 5 large boxes (60 - 100 bpm)
The heart rate is in the normal physiologic range of 60 to 100 bpm.
Sinus Bradycardia
R-R spacing > 5 large boxes (< 60 bpm)
The heart rate is slow. Count the large boxes between two R-waves: 300 divided by that number is less than 60 bpm, indicating Bradycardia.
Sinus Tachycardia
R-R spacing < 3 large boxes (> 100 bpm)
The heart rate is elevated. The R-R interval is short, and 300 divided by the number of large boxes exceeds 100 bpm, indicating Tachycardia.
🩺 2. Cardiac Rhythm (Rhythm)
Rhythm evaluates where the electrical pacemaker originates and how it conducts through the conduction pathways. Look for regular P-to-QRS relationships, standard PR intervals, and whether R-R spacing is regular or irregular.
Normal Sinus Rhythm
1:1 P-to-QRS ratio + PR interval 120-200ms
Every QRS complex is preceded by a normal, upright P-wave in Lead II, indicating the rhythm originates from the SA Node.
Atrial Fibrillation (AFib)
Variable R-R interval + Absent P-waves
The rhythm is irregularly irregular with no distinct P-waves (replaced by baseline fibrillatory waves). The atria are quivering.
Atrial Flutter
Sawtooth F-waves (Atrial rate 250-350 bpm)
Repeating sawtooth flutter waves are visible, especially in inferior leads II, III, and aVF, with a conduction block (e.g., 3:1 or 4:1).
Junctional Rhythm
Absent/inverted P-wave + Short PR interval (< 120ms)
The pacemaker originates in the AV junction, producing a slow, regular rhythm (40-60 bpm) with retrogradely inverted or hidden P-waves.
Ventricular Tachycardia (VT)
Wide QRS (> 120ms) + Rate > 100 bpm
A rapid, regular rhythm with wide, bizarre QRS complexes originating entirely in the ventricles. This is a life-threatening rhythm.
Ventricular Fibrillation (VF)
Chaotic baseline + Zero cardiac output
A completely disorganized quivering of the ventricles with no identifiable P, QRS, or T waves. Immediate defibrillation is required.
🧭 3. Electrical Axis (Axis)
The electrical axis represents the net vector direction of ventricular depolarization. The standard quadrant method uses Lead I and Lead aVF to find the axis.
Normal Axis (0° to +90°)
Lead I deflection > 0, Lead aVF deflection > 0
Both Lead I and Lead aVF have positive QRS complexes, showing a normal down-and-left electrical activation pathway.
Left Axis Deviation (LAD) (-30° to -90°)
Lead I deflection > 0, Lead aVF deflection < 0
Lead I is positive and aVF is negative (pointing away from each other). This Left Axis Deviation is common in LVH or inferior MI.
Right Axis Deviation (RAD) (+90° to +180°)
Lead I deflection < 0, Lead aVF deflection > 0
Lead I is negative and aVF is positive (pointing towards each other). This Right Axis Deviation suggests RVH or lateral wall injury.
Extreme Axis Deviation (-90° to -180°)
Lead I deflection < 0, Lead aVF deflection < 0
Both Lead I and aVF are negative (pointing upwards-right), a presentation typical of VT, severe hyperkalemia, or lead reversal.
🫀 4. Chamber Hypertrophy / Enlargement
Enlarged atria or ventricles affect the amplitude, shape, and duration of the waves on the ECG trace (P-waves for atria, QRS complexes for ventricles).
Normal Chamber Voltage
S(V1) + R(V5/V6) <= 35mm
Voltages and P-wave shapes are within standard physiological limits, indicating normal chamber sizes.
Left Ventricular Hypertrophy (LVH)
S(V1) + R(V5 or V6) > 35 mm (Sokolow-Lyon)
The sum of the S-wave depth in V1 and the R-wave height in V5/V6 exceeds 35mm. It is often accompanied by lateral ST-depression and T-wave inversion (LV strain pattern).
Right Ventricular Hypertrophy (RVH)
V1 R/S deflection ratio > 1 (R-wave > 7 mm)
V1 displays a dominant R-wave that is taller than the S-wave depth, combined with Right Axis Deviation, signaling Right Ventricular Hypertrophy.
Left Atrial Enlargement (LAE)
P-wave duration in Lead II > 120 ms (P-mitrale)
The P-wave is prolonged and notched in Lead II, or shows a deep terminal negative deflection in V1, indicating Left Atrial Enlargement.
Right Atrial Enlargement (RAE)
P-wave amplitude in Lead II > 2.5 mm (P-pulmonale)
The P-wave in Lead II is abnormally tall and peaked, indicating Right Atrial Enlargement.
🚨 5. Infarction and Ischemia
ST segment changes and T-wave anomalies reveal occlusion of specific coronary arteries (causing STEMI) or myocardial ischemia due to decreased blood flow.
Normal ST Segment (No ST/T Changes)
Isoelectric ST segment (deviation < 0.5 mm)
No ST elevations or depressions are present. The ST segment remains flat at the baseline level.
Acute Anterior STEMI
ST elevation > 2 mm in anterior leads V1-V4
Acute ST-segment elevation in precordial leads V1, V2, V3, and V4 indicates acute myocardial injury due to occlusion of the Left Anterior Descending (LAD) coronary artery.
Acute Inferior STEMI
ST elevation > 1 mm in inferior leads II, III, aVF
ST elevation in inferior leads II, III, and aVF represents acute inferior wall infarction, usually due to occlusion of the Right Coronary Artery (RCA). Frequently accompanied by reciprocal ST-depression in I and aVL.
Acute Lateral STEMI
ST elevation > 1 mm in lateral leads I, aVL, V5-V6
ST elevation in the lateral leads represents acute injury, typically due to occlusion of the Left Circumflex (LCx) coronary artery.
Myocardial Ischemia
ST depression > 0.5 mm or deep T-wave inversion
Horizontal or downsloping ST-segment depression or deep, symmetric, inverted T-waves indicate localized myocardial ischemia (oxygen strain).
🧪 6. Miscellaneous Conduction Blocks & Electrolytes
This category includes bundle branch blocks, AV block, pre-excitation accessory pathways, genetic channelopathies, and metabolic/electrolyte disturbances.
Normal Conduction
QRS width < 100 ms + PR interval 120-200 ms
Conduction times are normal. The electrical impulses traverse the AV node and ventricles without block.
Left Bundle Branch Block (LBBB)
QRS width > 120 ms + QS/rS in V1
A wide QRS complex with a broad, notched lateral R-wave (Leads I, aVL, V5-V6) and a deep negative deflection in V1, indicating Left Bundle Branch Block.
Right Bundle Branch Block (RBBB)
QRS width > 120 ms + rsR' peak in V1-V2
A wide QRS with a classic 'M' pattern (rabbit ears) in the right precordial leads V1-V2, and a wide slurred S-wave in Lead I and V6, indicating Right Bundle Branch Block.
First-Degree AV Block
PR interval > 200 ms (constant prolongation)
A prolonged PR interval (more than 5 small boxes) that remains constant for all conducted beats, representing First-Degree AV Block. Every P-wave still conducts to a QRS.
Wolff-Parkinson-White (WPW)
PR interval < 120 ms + Delta-wave slurring
A short PR interval and slurred upstroke (delta wave) of the QRS complex, diagnosing Wolff-Parkinson-White syndrome via pre-excitation through an accessory pathway (Bundle of Kent).
Brugada Syndrome
ST elevation > 2 mm in V1-V2 with inverted T-wave
A genetic sodium channelopathy showing coved ST-segment elevation in right precordial leads V1-V2, ending in a negative/inverted T-wave, placing the patient at high risk of sudden cardiac death.
Hyperkalemia (Severe)
Tall, narrow, peaked 'tent-shaped' T-waves
Elevated extracellular potassium slows repolarization, producing narrow, peaked T-waves, flattened P-waves, and widening of the QRS complex at higher levels.
Hypokalemia
ST depression + Prominent U-wave
Low potassium impairs repolarization, causing ST-segment depression, flat T-waves, and a prominent U-wave following the T-wave.