FDA May Not Have Adequately Tested Heart Devices for Short-Circuiting, Physician Says

The Food and Drug Administration is about to approve the use of a new electrical component for heart device implants, but it may not have adequately tested the device for potential risks, said Dr. Robert G. Hauser of the Minneapolis Heart Institute in an article he wrote with Dr. Adrian K. Almquist, published in The New England Journal of Medicine.

The problem, Dr. Hauser says, is in the design of a new way of connecting defibrillators to the wires that carry high-voltage electrical volts between the units and the heart. Currently, the two high-voltage wires enter the housing of a device through separate, insulated channels. In the new design, they effectively enter together and are insulated in a different way. This could increase the risk of short-circuiting, which could prevent the defibrillator from giving an electrical jolt to restore an erratically beating heart to a normal rhythm.

The new design will also be used in cardiac resynchronization therapy units, which combine defibrillators and pacemakers.

The FDA reasons that the new wiring connectors are a design modification, and not new technology, so human testing is not required. Instead, producers must carry out mechanical stress tests of the new connectors, and study testing done in animals. The FDA will also require manufacturers to carefully monitor the performance of the new units once they go on sale and are implanted. But Dr. Hauser believes testing should be done before the devices have gone into many patients. “Let’s test it first, before we put it into tens of thousands of people,” he said.

The FDA said in a letter published on the New England Journal of Medicine’s website that the required mechanical and animal testing was adequate to determine the unit’s risks. “Sometimes, nonclinical studies can be more informative than clinical evaluation with regard to device safety and effectiveness,” said the letter. Medtronic, the leading maker of heard devices, said the method of testing the new connectors was the same as the procedure used to develop the models currently in use.

Medtronic had some problems with the adequacy of their testing in 2007, however, when it recalled a new electronic lead for defibrillators called the Sprint Fidelis. The FDA approved the lead in 2004 on the basis of stress tests and animal studies, rather than human trials. The new leads, however, began to fracture and fail at high rates, leading to the recall after 235,000 people had them implanted. Dr. Hauser was one of the first to note a problem with Fidelis.

Dr. Hauser was also one of two cardiologists to go public years ago about short-circuiting problems in defibrillators made by former Guidant Corporation, now Boston Scientific. Those problems resulted in at least six deaths.

FDA officials said they would require manufacturers to conduct post-marketing studies of patients as soon as the sale of the units begins. Dr. William H. Maisel, a heart device expert in Boston, said, “[m]y concern is that the FDA does not have a great history of performing post-marketing studies on a timely basis.”