Sudden cardiac death: How would you know your risk?
IBM is working with scientists to use computers that predict risk of sudden cardiac death from dangerous heart rhythm problems that you may not know could strike. Using a computer to analyze genetic mutations in heart cells provides extra information for clinicians that goes beyond just getting a routine electrocardiogram at your doctor's office.
The study result published “The Journal of the American College of Cardiology” is the first to report use of a computer that incorporates cardiac models to predict risk of heart rhythm problems.
The risks can be calculated over a lifetime and can help physicians target drug therapy and aid in drug development.
IBM scientists first used canine heart cells as a computer model and then refined the model cells to act more like a human heart.
Matthias Reumann, Ph.D., and J. Jeremy Rice, Ph.D., included 192 heart cells made to function electrically like the ventricle or lower heart chamber wall by assigning different properties to the cells inside various locations within and outside of the heart wall.
Simulating the human heart requires the computer to recognize 100,000 complex mathematical equations at least 1,000 times over for a single heartbeat.
To test the model, the researchers used registries of patients with an inherited disorder known as long QT syndrome that puts them at high risk for sudden cardiac death. The disorder stems from mutations in the gene, KCNQ1.
The researchers used blood samples to determine the characteristics of different mutations and the defects they cause. The team then recreated the mutated proteins and tested them in lab cell lines.
Next they plugged each mutation’s electrical profile into the computer model to mimic the effect on the heart wall. The model produced an EKG for each mutation, showing the electrical activity of each contraction and relaxation of the heart.
When they analyzed the data, the team found the model predicted mutations that put patients at higher risk of death from prolonged repolarization of the heart or the time the heart takes to recover after each beat.
For every 10 millisecond delay in repolarization, risk of sudden cardiac death increased by one-third.
The authors say the computer model can predict risk of death from arrhythmia over a lifetime versus what can be gleaned from an EKG or electrocardiogram which only shows what’s happening with the heart at that moment.
In all, four high-risk mutations were identified that put people at particularly high risk for cardiac events.
Coeli M. Lopes, Ph.D., lead study author and assistant professor at the Aab Cardiovascular Research Institute at the University of Rochester Medical Center said in a press release, “With this model we can determine the influence of a single mutation on the much bigger overall response of the heart.”
The next step is to produce an even more sophisticated computer model that can help with safer drug development. The authors explain it’s difficult to keep potentially dangerous drugs off the market. You can watch an interview with Dr. Lopes here.
About sudden cardiac death
Sudden cardiac death, or SCD, happens when the heart rhythm suddenly becomes chaotic. Normally the upper chambers of the heart or the atrium contract to squeeze blood to the lower chambers and then relax. When the lower chambers that are the ventricles fill with blood electrical signals tell the heart to contract to push blood flow throughout the body. Then the ventricles relax and the process resumes.
Reasons for SCD include inherited heart diseases, electrical disturbances within the heart walls and weak heartbeat from previous or inherited damage.
The most common reasons for sudden cardiac death are electrical diseases known as “long QT syndrome” and “Brugada syndrome. Sudden death in athletes that has been in the news usually occurs from a thickened heart muscle, known as hypertrophic cardiomyopathy.
The incidence of SCD was highlighted in a review published in 2007 in “Current Problems in Cardiology”. Background information from the study states “Sudden cardiac death is a major public health problem affecting 500,000 patients annually in the United States alone” and can happen even when the heart appears to be “grossly” normal.
Preventing heart disease can lower your risk of sudden cardiac death that can occur from heart disease.
Maintaining a normal body weight, regular daily activity and consuming plenty of fruits and vegetables and a diet low in saturated fat are heart healthy interventions that should start early in life. It's also important to have your cholesterol checked regularly, in addition to avoiding tobacco - especially women who are recently found to be at higher risk for SCD from even moderate smoking.
The researchers plan to use IBM’s Blue Gene/Q, ‘supercomputer’ to develop a model of the whole human heart. The computer model will help understand who is at risk from sudden cardiac death in ways that aren’t currently available. The model is expected to help predict the success and safety profile of drugs to treat cardiac disorders that put patients at risk for sudden life-threatening arrhythmias.
University of Rochester
December 12, 2012
Image credit: Wikimedia Commons