July 17, 2012 — St. Jude Medical Inc. announced the results of a new study today, which has linked large-diameter leads to higher rates of erosion than small-diameter leads.
Problems with the leads prompted St. Jude to stop selling its line of Riata defibrillators in 2010. The U.S. Food and Drug Administration (FDA) issued a Class I recall in December of 2011. An estimated 80,000 people are currently implanted with a St. Jude Riata defibrillator.
Erosion refers to a problem where the metal defibrillator leads wear through their silicon insulation prematurely. The lead is the long, thin wire that connects heart tissue to a device that sends a high-voltage electrical shock to the heart. This shock can save a person’s life in case their heart has a sudden irregular rhythm. When the defibrillator leads erode prematurely, they can accidentally deliver an electrical shock, or fail to deliver a shock during an emergency.
The study involved 724 patients in 20 different locations internationally (including the U.S., Canada, and Japan). Researchers found that 24% of the large-diameter Riata 8F leads had erosion from the inside out. This is three times higher than the rate of erosion for smaller-diameter leads (9.4%) on the Riata ST 7F defibrillator leads. St. Jude stresses that the results of this finding are still preliminary, and researchers are currently conducting long-term safety studies that will continue for the next two years. The company has not issued any recommendations to physicians or patients, except to continue monitoring patients for signs of problems with the device.
Recently, St. Jude has asked the Heart Rhythm Journal to retract two articles that published critical studies of the Riata defibrillator. The journal published research linking the St. Jude defibrillators to at least 20 deaths, and a 9-fold increased risk of death compared to another defibrillator lead, the Medtronic Quattro Secure. St. Jude claims this research is flawed, inaccurate, and biased.
Other studies have linked the St. Jude defibrillator to a risk of perforation. If the exposed wires perforate the heart, blood can leak into the sac that surrounds the heart. This can lead to a condition called cardiac tamponade, in which fluid around the heart increases pressure and inhibits normal heart function. Cardiac tamponade can be deadly.
An estimated 80,000 people have the St. Jude Riata defibrillators. The company is the the second-largest manufacturer of heart rhythm devices in the United States.