VCG Visualization Using VRML 2.0

Diagnosis of cardiac disease have much to do with the ability of the clinician to visualize the condition of the heart through various means. One common and usually the first procedure used to "image" the heart is the standard 12-lead electrocardiogram. This 12-lead electrocardiogram provides the clinician with a 2D scalar representation of the electrical activity of the heart.The heart however is a 3-dimensional organ, therefore mapping this 2D representation onto the 3D physical organ is left to the cognitive skill of the clinician. One approach to facilitate this 3D visualization of the electrical activity of the heart is to either take a VCG in place of the standard 12-lead electrocardiogram or to transform the 12-lead 2D representation into the 3D VCG representation.

Below are example VCG output from an ECG analysis program that automatically generates VCG loops from standard 12-lead electrocardiograms. The VCG output is in VRML 2.0 format, thus allowing anyone with a Web-browser and a VRML 2.0 plug-in to view and "examine" the VCG loop.

In addition to visualizing simple VCG loops, this program also generates serial VCG loops to help the clinician visualize the evolving state of the heart. The examples shown here include patients with evolving acute myocardial infarction.The serial ECGs are animated to help the clinician visualize the location and loss of electrical potential over the regions of infarction.

Below are example VCG data in animated VRML 2.0 format. There are two sets:

Single VCG loop with "moving ball" that traces the trajectory of the VCG loop.
Serial VCG loops that morph from the earliest VCG to the final VCG

You will need to have a VRML 2.0 browser plug-in installed in your browser. If you do no have one already installed, you can obtain a BETA version of SGI's COSMO Player at:

SGI's VRML 2.0 COSMO Player

Once the VRML 2.0 models have been loaded, adjust your view and click near the origin to start the animation.

Single VCG VRML 2.0 Files

VCG Loop 590d8bfb.wrl
VCG Loop 46eac189.wrl
VCG Loop b500faba.wrl
VCG Loop 05e3077d.wrl
VCG Loop a31830a2.wrl

Serial VCG VRML 2.0 Files

The examples below represents a series of VCGs taken for an individual patient. The animation shows how the morphology of the vector loop changes over hours to days. Some of these patients are normal, some are undergoing an acute myocardial infarction.The X-axis is represented in red (dimmer red color represents negative X), the Y-axis is represented by green, and the Z-axis is represented by blue. Click on the VCG near the origin to start the animation.

Example 1: This is a 67 yr old Male presenting to the ED. The series of EKGs were collected over a 4 day period. Notice the change in T-wave mean vector and loss of R-wave voltage in the anterior region.
Example 2: This is a 82 yr old Male, with blood pressure of 145/78 presenting to the ED. The series of EKGs were collected over a 4 day period.
Example 3: This is a 87 yr old Male, with blood pressure of 136/54 presenting to the ED. The series of EKGs were collected over a 6 hour period.
Example 4 : This is a 89 yr old Female, with blood pressure of 212/67 presenting to the ED. The series of EKGs were collected over a 7 hour period.
Example 5: This is a 67 yr old Female presenting to the ED. The series of EKGs were collected over a 2 day period.
Example 6: This is a 78 yr old Male, with blood pressure of 180/92 presenting to the ED. The series of EKGs were collected over a 2 day period.
Example 7: This is a 52 yr old Male, with blood pressure of 74/51 presenting to the ED. The series of EKGs were collected over a 2 hour period.

About these EKGs

The moving ball traces the single VCG in about 1/20th real time.

These VCGs were derived from standard 12-lead ECG data sampled at 500 sps on a Hewlett Packard PageWriter XLi cardiograph. The transform used was published by Palm et al some time ago. It is also available in Peter McFarlane's three volume text book on Electrocardiography.

The Serial ECGs were signal processed to identify the normal QRS complexes and averaged. Each of the averaged ECGs were then "normalized" to a common heart rate. Only the QRS and STT segment were normalized. The PR segment was not used. The standard 12-lead averaged ECGs were then converted to VCG format and transformed into VRML 2.0 format for display.