A realistic computer model of the human heart is expected to make treating heart diseases more effective: doctors will be able to test medicines and surgical techniques on the computer heart and determine the most effective therapy. Olaf Dössel, director of the Institute of Biomedical Engineering at the Karlsruhe Institute of Technology, believes that his team's heart model is among the top five in the world.
The older we get, the greater the risk of contracting heart disease: blood vessels might constrict or clog up completely, the heart could become out of sync. Although a number of robust techniques for diagnosing cardiac conditions are available (e.g., ECGs that record heart activity, ultrasound that visualises blood flow and therefore leaky heart valves), cardiologists are unable to predict the likelihood of success of a particular therapy. Olaf Dössel, director of the Institute of Biomedical Engineering at the Karlsruhe Institute of Technology (KIT), believes that all this could change over the next few years. "The search for a suitable therapy usually follows the principle of trial and error, it is usually apparent in hindsight which therapy is best. Our motto is: get it right the first time. We hope that the model we are working on will be able to effectively predict whether a particular therapy will be successful or not."
Olaf Dössel and his team have been working with cardiologists for many years to develop a realistic computer heart: "Our contribution to the project is mathematics and software," says Dössel. However, the mathematical simulation of the human heart is an enormous challenge. With four chambers, four valves, inflows and outflows, the heart is not only a complex structure, it has equally complex pumping movements: First, the atria and ventricles relax and blood flows in. Then the chambers contract. The left chamber pumps oxygen-rich blood through the aortic valve out to the rest of the body; the right chamber pumps oxygen-poor blood through the lung arteries into the lungs.
All this must be calculated to be able to produce a "real" three-dimensional heart on the screen. "As the heart itself also moves, the model we have created is what we call a 4D model," explains Dössel. The reason the image of the organ looks so realistic is also down to the enormous progress made in imaging: only computed tomography (CT) and magnetic resonance (MR) images enable the reconstruction of the heart with such high precision. Data from countless scans are included in the calculation of an average virtual heart.
"Our model of a healthy heart is already very good. When we demonstrate how the heart model works, cardiologists usually tell us that they have never been able to see the complex electrical and mechanical processes of the heart so clearly," says Dössel.
The next step is still under development, i.e. personalised heart models. In order to achieve this, the Karlsruhe-based researchers need to turn the virtual average heart into a virtual patient heart, i.e. all data obtained from a specific patient using ECG, catheters, CT, MRI and ultrasound have to be included in the computer model. When all that has been done, the patient heart with all its characteristics, including scar tissue after a heart attack or conduction disorders then has to be visible on the screen. "If the model is accurate, we can calculate the consequences of a cardiac infarction in patient X or how his or her heart is likely to react to different types of treatment," says Dössel.
Dössel and his team specialise in heart models showing cardiac infarctions and arrhythmias. So-called atrial fibrillation is the most common type of arrhythmia. Around 800,000 people in Germany suffer from these conditions, which particularly affect the elderly. Atrial fibrillation is an abnormal heartbeat rhythm. The electrical impulses, which cause the heart to pump blood, arise in the so-called sinus node, which is the actual impulse generator in the heart, as well as other areas of the heart.
Cardiac probes are applied when medicines no longer alleviate the condition. In such cases, cardiologists will use the probes to heat tissues in order to obliterate the areas where electrical noise is created. If everything goes to plan, abnormal conduction pathways are interrupted and normal heart rhythm is restored. "Abnormal heart rhythm reoccurs in 4 out of 10 patients within a few weeks after treatment," says Dössel who would like to be able to use his model to determine prior to operation where scars need to be placed to ensure lasting success.
Using such computer models might also help generate cost savings: "Although we still have to improve the imaging process before the model is perfect, it already helps save surgery time. Time spent in the operating theatre can generally be reduced from four hours to one," says Dössel who is convinced that in future many medical issues will be solved with computer models. In fact, scientists around the world are working on kidney, blood circulation and brain simulation models. Such methods have long been applied in industry. Engineers, for instance, always build aircraft and cars on a computer before going on to develop the real thing.
Dössel believes that a personalised heart computer will be available for patient use in about five years' time. Meanwhile, the Karlsruhe scientists' model is being used for research purposes to gain a better understanding of heart diseases, optimise therapies and develop new drugs, amongst other things.