T. Jared Bunch, MD

Rhythm of Life

The lowdown on heartbeat disorders

Posted in: Heart Disease

What do Israeli Missile Defense Systems and Your Heart Rhythm have in Common? A lot more than you think

Published Sep 4, 2013


We treat many different electrical problems in the heart in ways that don’t require medications.  For fast heart rhythms, we look to find small electrical short circuits in any chamber within the heart or areas outside the normal electrical system of the heart that are beating on their own and ablate them.  The process of ablation means to either significantly heart or freeze a small area of tissue to destroy the target cells that are causing the problem.  For people who have a slow heart rhythm, we a small device in the chest called a pacemaker, placed just under the skin.  We then thread wires or leads into the heart that are connected to the pacemaker.  These leads provide small amounts of electricity when your heart beats too slowly to provide you a normal heart rate.  In people with very week hearts from heart failure, pacemakers can also deliver a high energy shock to stop a heart arrest.  These systems are called implantable cardioverter defibrillators (ICD).

Traditional Minimally Invasive Navigation in the Heart

We use minimally invasive techniques to get into the heart.  This means, we use your arteries or veins as roads to advance our tools to reach the your heart.   Without the use of your arteries or veins, we would need to surgically open the chest and reach the heart directly.

Traditionally, minimally invasive approaches have been guided with x-ray.  We use a machine called a fluoroscope.  These machines rapidly take many x-rays and convert them into an moving image that looks like a movie.  All of our tools are made of material that appears very dark during fluoroscopic imaging.  All of our body tissues look a little different when imaged with fluoroscopy.   Using fluoroscopy we can see a tool as it moves in the body though different organs.  If the distinction between body tissues is not adequate, we give a contrast agent that will make the targeted organ or organ system look dark and thereby separate it from surrounding tissues.  The best example of this is a coronary angiogram.  This is a common procedure performed if you experience chest pain or a heart attack.  Contrast is provided into the coronary arteries and the operator can quickly identify any plaque-related narrowings of the arteries or clots which become distinct from the surrounding heart muscle.

X-ray imaging creates a single plane view, similar to if you are watching a television screen.  So often multiple views are required to get a 3 dimensional understanding of your heart to define where our tools are located in the heart.  A lot of our training involves putting together many single plane views in our mind to create a 3 dimensional understanding.  The problem with taking multiple images with a fluoroscopy or x-ray machine is that these tools use radiation.  X-ray exposure as I discussed in my blog entry “What questions should I ask before my atrial fibrillation ablation” is associated with risk on cancer to the patient, the person performing the procedure, as well as the staff that care for you during the procedure and assist the person performing the procedure.  So it is understandable that it remains of upmost importance to you, and all of us that perform these procedures, that we minimize the amount of radiation exposure and look towards other methods to navigate our tools in the heart to treat abnormal heart rhythms.

3D Virtual Tools that Allow Navigation in the Heart without Radiation Exposure

For nearly all ablations performed in the United States, we have started to rely much more on non-x-ray based imaging tools.  These are computer generated virtual body and heart anatomies.  These work by using a series of patches placed on your back and chest.  These patches communicate continuously with the tools inside the heart.  They do this by measuring small changes in the electrical or magnetic signals between the tools and the patches that occur naturally with movement of the tool and when the tool tip comes in contact with different tissues that have different characteristics.   When we create a 3 dimensional image we need 3 plans (x, y, and z coordinates).  These tools need to be able to sense changes in all of these coordinates and as they do a 3 dimensional real-time image is created.  This is a simple explanation of a complex process that also needs to account for the fact the heart is continuously moving as well as the chest wall itself during breathing.  Since these tools do not require x-ray, you do not receive radiation with their use.  As these tools improve and the anatomies become more accurate and precise, their use is expanded.

Israeli Missile Defense Technology

There are many different technologies that are needed to provide real-time assessment of location and movement.  These systems have to be exceptionally accurate and have the capacity to change in the setting of a dynamic environment.   This need is highlighted in efforts to create missile tracking and targeting systems.  Elbit Systems Ltd (, is an Israel based international defense electronics company with expertise in communication systems, surveillance, homeland security, unmanned aircraft systems, simulations, eletro-optics, and aerospace, land, and naval systems.  They have developed many technologies that in the area of homeland defense that do exactly what has been discussed.   As with many defense technologies, there is considerable application elsewhere.  Mediguide ( was a company that was created to advance these 3 dimensional localization and targeting technologies to navigate tools in the body to allow very precise, minimally invasive therapies.  The position sensors created were very small (sub-millimeter sized) and could be mounted on needles, guidewires, pacemaker leads, or ablation tools.  These sensors can be dynamically tracked in the body using computers in the setting of 3 dimensional virtual anatomies.  In 2008, St. Jude Medical announced that they had purchased Mediguide (  St. Jude Medical is a company that already provided many of the tools we commonly used to create 3 dimensional maps of the heart and to perform ablations.    They also have a large line of cardiac pacemakers and ICDs.  With this acquisition there was great enthusiasm that tools would become smaller and more accurate and radiation exposure dramatically reduced.

Are Radiation Free Complex Pacemaker Placements Possible?

Armed with Mediguide technology, a team from Leipzig Germany sought to show that they could implant a complex pacemaker system that require 3 leads (cardiac resynchronization therapy pacemaker) using this technology rather than fluoroscopy.   This study was published this week in the journal, Circulation:  Arrhythmia and Electrophysiology.  These pacemaker systems can be difficult to implant, and at times can consume 20-40 minutes of fluoroscopy.  They can be particularly challenging when a pacemaker lead is required in the left-sided lower heart chamber (left ventricle).  We put leads in this chamber by inserting them in small surface veins in the left ventricle.  Just like the veins on the top of your hands, we all have different vein patterns.  Some veins are big, others are small, and many have small valves that make passage challenging.  We often have to try many different veins to find one that adequately holds the pacemaker lead and when pacing is required uses the least amount of energy possible to preserve the pacemaker battery life.

To perform this procedure, the German team used two orthogonal fluoroscopy images (2 images that were 90 degrees apart).  These were saved by a computer that was directly linked to the Mediguide technology sensors.  When the sensors embedded on a tool or wire were moved in the region that the fluoroscopic image was created, their exact location was tracked.  The two saved images in orthogonal plans allowed for a 3 dimensional image construction.  This tracking was continuous through the region that was imaged.  Normally, with each movement of a tool, an operator would have to perform additional fluoroscopic imaging to see position changes.

In a series of 15 patients, pacemaker leads with tiny Mediguide technology sensor embedded in their tips, were implanted in the heart.  In all cases, this technology allowed the successful placement of the pacemaker lead in the left ventricle.  Most importantly, the complete system placement was done with an average of approximately 5 minutes of fluoroscopy.  This represents a 75-85% reduction in radiation exposure to the patients, operator, and staff.  Since this was their first experience with a new technology and a learning curve is always present, the need for 5 minutes of fluoroscopy will likely be reduced in the future.  As important as the radiation exposure, the German team also did not see an increase amount of time required to complete the procedure or a higher risk of complications.  These findings and this new technology are exciting as we try to replace old antiquated radiation-based systems with new computer generated systems with novel tracking and imaging capacities.

Mediguide Technology Coming to a Location near You

St. Jude Medical has a very large product portfolio.  As their current and new tools and technologies are fitted with Mediguide technologies, each will need review by the federal drug administration (FDA) before we can use them.  However, many tools are already available and there are a number of Mediguide systems currently fully operational in the United States.  As these sensors are applied to a wide variety of heart disorders, we will be able to have a full understanding of their potential benefit and capability.


Richter S, Doring M, Gaspar T, John S, Rolf S, Sommer P, Hindricks G, Piorkowski C.  CRT Implantation Using a New Sensor-Based Navigation System:  Results from the First Human Use Study.  Circulation:  Arrhythmia and Electrophysiology

Posted in: Heart Disease

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