In 5 to 20 percent of cases, however, the anti-tachycardia pacing can result in an accelerated heart rate or induction of ventricular fibrillation.
When pacing pulses accelerate tachycardia, current ICD devices usually deliver a strong and painful shock, he said. Further study of the engineered tissues might lead to more reliable and less painful strategies for halting arrhythmias, Bursac said. For example, preliminary observations suggested that pacing the engineered tissue at rates slightly below the rate of tachycardia may still slow down the accelerated rhythm.
The results in general demonstrated the promising utility of engineered tissue in the laboratory for studying the complex electrophysiological properties of the heart in both health and disease, they said.
"Implanted defibrillators can protect many patients, but sometimes the devices instead accelerate rapid heart beats," Bursac said. "The mechanism responsible for this had remained unclear. We've now been able to show in these cardiac cell cultures that electric pulses sometimes break rotating waves rather than block them."
Engineered cardiac tissues also might prove a useful testing ground for potential drug and gene therapies that could restore normal heart rhythms, he added.
"Bursac and Tung have presented a convincing mechanistic explanation for a clinically important phenomenon that they reproduced in a Petri dish," Igor Efimov and Crystal Ripplinger, both of Washington University in St. Louis, wrote in an editorial. "Their study showed that, as in clinical therapy, anti-tachycardia pacing is highly successful; yet in some cases, it may result in acceleration of reentrant arrhythmia instead of its termination."