ECG Vector
Support
Updated October 4, 2026 · Requires macOS 14+ or iOS/iPadOS 17+
ECG Vector is an educational simulator for learning how electrical activity in the heart relates to the waveform recorded by each lead. Do not use it for diagnosis, treatment decisions, or patient-specific waveform prediction.
1. Getting started
- Choose ECG Mechanism, Ion & ECG, ECG & Conditions, or Learn & Quiz. Use the top tabs on Mac and iPad, or the feature menu shown at launch on iPhone. On iPhone, the upper-left back button returns to the feature menu.
- In ECG Mechanism, choose Adult Normal, Right Bundle Branch Block, Pediatric Normal, or another typical pattern under Waveform Model.
- Select a waveform card in the 12-lead overview. That lead becomes the 3D lead axis and enlarged trace.
- Select Play, then choose 0.05× to 1.0× under Speed. Dragging the timeline pauses playback and moves every waveform cursor to the selected time.
- Use the two 10 ms controls to step backward or forward while paused.
- Drag the 3D view to rotate it, and pinch or scroll to zoom. Select Reset View to return to the standard orientation.
2. Reading the 3D view
Excitation and repolarization
The yellow luminous trail approximates the depolarization wavefront. The pink trail approximates ventricular repolarization—the electrical recovery associated with the T wave, not a second excitation.
Microdipoles and the cardiac vector
Relative extracellular − and + regions appear across a wavefront. Each local arrow points from − to + and represents a microdipole. Components in the same direction add, opposing components cancel, and the remaining orange arrow is the cardiac vector M(t).
Lead axis and projection
Lead axis L points from the negative to the positive electrode. The projection arrow shows the component of M(t) along that axis: toward the positive electrode gives an upward deflection, and the opposite direction gives a downward deflection. Its length is the magnitude of the projection onto the unit direction; ECG voltage V(t) = M(t) · L also includes lead sensitivity. Two-lead comparison uses different colors for each lead axis and its projection.
Contraction
Shortening and slight twisting of the atria and ventricles represent mechanical contraction. Contraction follows electrical depolarization with a delay and is not added as a separate ECG voltage component.
3. Waveform breakdown and two-lead comparison
At the top of ECG Mechanism, choose the one-lead, two-lead, or 12-lead mode. One-lead mode enlarges the selected trace and offers component breakdown. Two-lead mode compares the waveforms and 3D lead-axis projections at the same time. The 12-lead mode shows synchronized standard ECG traces.
In component breakdown, dashed traces show the selected component and solid traces show the sum. Select atrial, septal, main ventricular, delayed, or repolarization components to explore their contribution to the waveform.
The number of peaks is not the number of excitations. It is the time-varying result of projecting each vector onto a lead axis. The same electrical activity can therefore be monophasic, biphasic, positive, or negative in different leads.
4. Display items, cutaway, and opacity
Open Display inside the 3D panel to switch between Cutaway and Exterior and independently show or hide the heart, internal structures, conduction system, electrical activity, mechanical contraction, lead measurement, and electrodes. Heart opacity is in the same panel.
- The default is Cutaway, with internal structures and electrodes hidden.
- Selecting a legend entry highlights the matching element in 3D.
- The orientation compass uses the patient’s right, left, superior, inferior, anterior, and posterior directions.
- The front electrode map faces the patient: screen left is the patient’s right.
A standard 12-lead ECG uses 10 electrodes: RA, LA, LL, RL, and V1–V6. RL is the neutral electrode, not part of the standard lead-voltage differences or Wilson central terminal. Moving RL does not change the idealized ECG in this app; the instrument’s noise-rejection circuitry is not simulated.
5. Ion & ECG
Choose a representative example from the preset selector. Increased Late Sodium, for example, shows the modeled link between a longer action potential and a longer QT. Pro allows free adjustment of major currents and extracellular K⁺, ionized Ca²⁺, Na⁺, and H⁺ (pH), with baseline and modified traces in one or 12 leads. The ECG stays visible while you adjust settings on iPhone.
Changes from baseline separates the combined numerical result from the effect of changing each factor alone. Multiple settings can offset one another. The condition links below the ECG explain representative low-calcium, high-potassium, and other examples. The high-potassium example also includes reduced P-wave amplitude and a longer PR.
Quantitative model output separates cellular calculations, including Nernst equilibrium potentials, from educational whole-heart ECG estimates. The direct ECG effect of Na⁺ alone is generally small within usual clinical ranges, so the trace may change very little. The direct repolarization effect of pH alone is not assigned a fixed direction and is marked as unmodeled.
This is not a patient-specific prediction model. The displayed model ranges are neither physiological normal ranges nor confidence intervals. Use the app’s information button to read About for the modeling limitations and educational-use notice.
6. ECG & Conditions
Choose a condition or reference example, then compare it with Adult Normal in one or 12 leads. Read the waveform features and their mechanisms while using the common time scale to identify differences. In the 12-lead comparison, I, II, III, aVR, aVL, and aVF form the left column, and V1–V6 form the right.
Pediatric Normal is a representative child around age five. The fever example shows sinus tachycardia, and the higher-BMI example illustrates population-level body-habitus tendencies—not a prediction from an individual’s temperature or weight alone. Condition examples are not diagnostic criteria.
7. Free access and ECG Vector Pro
The free version includes Adult Normal and Right Bundle Branch Block, all 12 standard ECG leads, fixed standard electrode positions, comparison and quiz samples, favorites, and four guided Ion & ECG examples.
ECG Vector Pro is a one-time non-consumable purchase, not a subscription. It unlocks free adjustment of ion currents, extracellular ions, and pH with synchronized 12-lead response, pediatric and other condition examples, custom leads, electrode editing and misplacement presets, and the complete comparison and quiz libraries.
Purchase Pro
- Select the crown or PRO control in the top bar.
- Wait for Apple to load the localized price.
- Select the price button and complete Apple’s purchase sheet.
Restore a purchase
On a Mac, iPhone, or iPad signed in with the Apple Account used for purchase, open the Pro screen and select Restore Purchases. Syncing across devices can take a short time.
8. Troubleshooting
Only Reload Purchase Information and Restore Purchases are shown
StoreKit has not loaded the product. Check your connection, confirm that the App Store is signed in, update ECG Vector, and confirm that the purchase is available in your country or region. Wait briefly, then select Reload Purchase Information. Purchases in TestFlight builds are handled in Apple’s test environment.
Pro is not active after purchase
Confirm that you are using the same Apple Account, select Restore Purchases, then quit and reopen the app. A pending purchase activates after Apple approves it.
The 3D view is slow
Open Display and hide internal structures, electrodes, or other overlays you do not need. Close the explanation and other demanding apps, then reopen ECG Vector.
The top items in the Display panel cannot be selected
Update to the latest app version. The panel should remain fixed on screen while its contents scroll. If the issue remains, contact support with the device model, display zoom, and orientation.
Change the interface language
ECG Vector follows the device or per-app language. Open Settings → ECG Vector → Language and choose a supported language.
9. Contact
Do not include patient or personal information in a report. Include the ECG Vector version and build, device and OS, selected waveform model and lead, steps leading to the issue, and any message shown.