The heart is a difficult organ to study in detail because it is such a dynamic, constantly moving organ. Now, Duke engineers have induced rat heart cells in culture to mimic some of the key electrical properties of whole hearts.
They have already used the technique to gain new insight into the mechanisms that spawn irregular heart rhythms. Nenad Bursac, assistant professor of biomedical engineering, and his colleagues reported their findings in the journal Cardiovascular Research.
In their experiments, the researchers sought to understand the characteristics of ventricular tachycardia, a condition characterized by abnormally fast beating of the heart's pumping chambers.
In particular, they sought to understand how such arrhythmia may lead to ventricular fibrillation, in which the heart's electrical activity becomes disordered, causing the ventricles to flutter rather than synchronously beat. As a result, pumping of the blood is inefficient, and death can result within minutes.
"Ventricular tachycardia and fibrillation are the leading causes of sudden death in the developed world," Bursac says. "Yet, in humans and animals the anatomy is so complex that mechanisms of such arrhythmias are difficult to dissect systematically."
In their study, Bursac and his colleagues created a simpler version of cardiac tissue using cells from the heart ventricles of neonatal rats. They transferred the cells into culture dishes on which they had stamped precise patterns of proteins known to support heart-tissue growth. The proteins caused the cells to orient themselves, interconnect, and grow in a manner that mimics normal heart tissue, Bursac explains.
The team then induced the same kind of electrical activity in the engineered tissues that would occur in ventricular tachycardia, and attempted to halt it with pace-setting pulses. The pulses successfully halted the wave 80 percent of the time, they report. In the remaining cases, however, the pulses continued to activate the cardiac cells at an accelerated rate. Should such characteristic patterns hold in patients, Bursac says, physicians could potentially use them to identify those people for whom defibrillators are more likely to worsen abnormal heart rate.
Heart in a Petri Dish
June 1, 2006