ECG Vector
Support
Updated October 15, 2026 · Requires macOS 14+ or iOS/iPadOS 17+
This guide covers version 1.3, available on the App Store.
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, Ventricular Action Potential, Cardiac Rhythm, 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.
- In one- and two-lead modes, choose leads inside the 3D panel. In the 12-lead overview, select a waveform card to change the selected lead.
- 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 and 2D views
Excitation and repolarization
Yellow bands schematically show depolarization, while pink bands show ventricular repolarization. Spreading atrial activation is distinguished from septal bundles and a branching ventricular conduction network. Repolarization is not a second excitation.
The cardiac vector and its components
One orange arrow shows either the sum of all components or the selected component. It points from − at its base to + at its tip, not along a literal path of electric current. The direction guide explains each contribution. Opposing contributions can cancel, so a small resultant does not necessarily mean the whole heart is inactive.
Lead axis and projection
A light lead axis points from the negative to the positive electrode; a darker projection arrow of the same hue lies directly on that axis. Projection toward the positive electrode gives an upward deflection, and the opposite direction gives a downward deflection. Arrow length and sign represent projection onto the unit lead axis; ECG voltage also multiplies that projection by lead sensitivity. Two-lead mode distinguishes the leads with green and purple hues.
The adjacent 2D diagrams align each lead’s positive direction upward to show the cardiac vector and its projection. In two-lead mode, both diagrams compare the same source vector at the same scale.
Contraction
Local atrial and ventricular shortening schematically represents mechanical contraction. It follows electrical depolarization with a delay and is not added as a separate ECG voltage component. The heart wall, internal structures, and conduction paths move with the same deformation.
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 cutaway retains a faint front wall at 8% opacity to make the conduction paths’ depth clearer. The initial view fits the heart. Drag the divider between 3D and waveforms to adjust their space, or double-click/double-tap it to restore the default proportions.
- 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. Ventricular Action Potential
Observe membrane voltage, ion currents, and gates at the same time in the Luo–Rudy I (1991) single-ventricular-cell model. Adjust stimulus strength or pause at the sodium-current peak. The standard model and stimulus adjustment are free.
Pro adds conductance adjustment, current-suppression experiments, and standard-trace overlays. This workspace teaches a single cell’s action potential; it does not directly calculate a surface ECG or clinical QT interval.
7. Cardiac Rhythm
View representative membrane voltages and arrival times for the sinus node, atria, AV node, Purkinje fibers, and ventricle. Adjust sinus cycle, conduction speed, and AV delay, or select schematic bradycardia, tachycardia, and AV-block examples. All features are free.
These schematic regional voltage templates are not surface ECG traces. The AV-delay setting is not the PR interval itself, and the 2:1 AV-conduction example does not distinguish Mobitz I from Mobitz II.
8. 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 a heart-rate increase, 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. Model and lead selections remain independent between this workspace and ECG Mechanism.
9. Free access and ECG Vector Pro
The free version includes Adult Normal and Right Bundle Branch Block, all 12 standard leads, fixed standard electrodes, comparison and quiz samples, favorites, and four guided Ion & ECG examples. The standard ventricular action-potential model, stimulus adjustment, and all Cardiac Rhythm features are also free.
ECG Vector Pro is a one-time non-consumable purchase. It includes custom ion-current, extracellular-ion, and pH adjustments with synchronized 12-lead response, pediatric and other patterns, custom leads, electrode editing and misplacement, the full comparison and quiz libraries, plus ventricular conductance adjustment, suppression experiments, and standard-trace comparison. These additions are included in the existing Pro purchase; no new purchase or subscription is required.
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.
10. 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.
11. 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.