LETTERS TO THE EDITOR To the Editor:
I read with interest the article in the November Part I1 1991 issue of PACE regarding “Undersensing as a consequence of lead incompatibility: Case report and a plea for universality.” Having spent considerable time working on the IS-1 Standard as a Medtronic technical representative, I am fully aware of the similarities and differences between VS-1 and IS-1 standards. I want to inform you that this incident would not have occurred had the lead connector been designed per the IS-1 requirements. The IS-1 Standard requires that a proximal set screw torqued to 0.15 k 0.01 Newton-Meters (approximately 21.3 ? 1.4 inch-ounces] onto a unipolar connector will not affect the function of the lead. Since most companies supply torque-limiting wrenches with their pulse generators (primarily to prevent stripping connector block set-screws), the torque applied to the wrench is not entirely up to the discretion of
the physician. Unfortunately, this does not preclude the use of nontorque-limiting wrenches that are available! Medtronic uses a high strength alloy ring that electrically isolates a tightened set screw from the unipolar conductor assembly beneath the ring. Interestingly enough, this type of incident was discussed many times during the IS-1 Standard development. To my knowledge, no one on the committee could foresee exactly what would happen without this protection because we felt it was dependent on the unipolarhipolar switching technique used within the pulse generator. We did feel, however, that this was an important consideration in preparation of the Standard. Although the “jury is still out” on the IS-1 Standard, it is gratifying to know that we at least addressed one potential problem! Keith Ufford Medtronic, Inc. Minneapolis, Minnesota
Xenophon F. Costeas Mark H. Schoenfeld Yale University School of Medicine New Haven, Connecticut
To the Editor: We acknowledge that the requirements for devices comforming to the IS-1 Standard are as stated in the letter by Mr. Ufford, and confer significant protection against mechanical lead injury. As we emphasized in our article,’ greater acceptance of one universal standard will allow physically compatible devices to be indeed interchangeable, to whether this or any future standards may be improved remains to be determined.
References 1. Costeas FX, Schoenfeld MH. Undersensing as a consequence of lead incompatibility: Case report and a plea for universality. PACE 1991; 14:1681-1683.
May 1992
PACE, Vol. 15
I read with interest the article in the November Part I1 1991 issue of PACE regarding “Undersensing as a consequence of lead incompatibility: Case report and a plea for universality.” Having spent considerable time working on the IS-1 Standard as a Medtronic technical representative, I am fully aware of the similarities and differences between VS-1 and IS-1 standards. I want to inform you that this incident would not have occurred had the lead connector been designed per the IS-1 requirements. The IS-1 Standard requires that a proximal set screw torqued to 0.15 k 0.01 Newton-Meters (approximately 21.3 ? 1.4 inch-ounces] onto a unipolar connector will not affect the function of the lead. Since most companies supply torque-limiting wrenches with their pulse generators (primarily to prevent stripping connector block set-screws), the torque applied to the wrench is not entirely up to the discretion of
the physician. Unfortunately, this does not preclude the use of nontorque-limiting wrenches that are available! Medtronic uses a high strength alloy ring that electrically isolates a tightened set screw from the unipolar conductor assembly beneath the ring. Interestingly enough, this type of incident was discussed many times during the IS-1 Standard development. To my knowledge, no one on the committee could foresee exactly what would happen without this protection because we felt it was dependent on the unipolarhipolar switching technique used within the pulse generator. We did feel, however, that this was an important consideration in preparation of the Standard. Although the “jury is still out” on the IS-1 Standard, it is gratifying to know that we at least addressed one potential problem! Keith Ufford Medtronic, Inc. Minneapolis, Minnesota
Xenophon F. Costeas Mark H. Schoenfeld Yale University School of Medicine New Haven, Connecticut
To the Editor: We acknowledge that the requirements for devices comforming to the IS-1 Standard are as stated in the letter by Mr. Ufford, and confer significant protection against mechanical lead injury. As we emphasized in our article,’ greater acceptance of one universal standard will allow physically compatible devices to be indeed interchangeable, to whether this or any future standards may be improved remains to be determined.
References 1. Costeas FX, Schoenfeld MH. Undersensing as a consequence of lead incompatibility: Case report and a plea for universality. PACE 1991; 14:1681-1683.
May 1992
PACE, Vol. 15
