- Email: [email protected]
To the Editor—Response
168
Heart Rhythm, Vol 5, No 1, January 2008 St George’s Hospital London, UK
References 1.
Hauser RG, Kallinen LM, Almquist AK, et al. Early failure of a small-diameter high-voltage implantable cardioverter-defibrillator lead. Heart Rhythm 2007;4:892– 896.
To the Editor—Response: The observations by Catanchin et al are of concern for two reasons: 1) their patient almost certainly died as the result of a Sprint Fidelis lead failure, and 2) all 5 failures occurred in relatively young patients. This is the second patient death associated with a Sprint Fidelis lead failure that has been brought to our attention as the result of our report in Heart Rhythm. The first death was suffered by a patient in North Carolina who had a witnessed cardiac arrest and eventually died; pre-mortem interrogation of his Sprint Fidelis model 6949 revealed noise on the ventricular channel. While death caused by a Sprint Fidelis lead failure may still be rare, it is now a known risk. That Sprint Fidelis failures seem to be occurring in younger and presumably more active patients is consistent with our experience. This finding suggests that stress fatigue is the probable mechanism of failure, and hence more Sprint Fidelis failures are likely. We continue to believe that this lead should be avoided, and that implanted leads require close follow-up and continuous monitoring. Given the known risks associated with revision and extraction, we discourage the routine prophylactic replacement of normally functioning leads. Robert G. Hauser, MD Linda M. Kallinen, BS Adrian K. Almquist, MD Charles C. Gornick, MD William T. Katsiyiannis, MD Minneapolis Heart Institute Minneapolis, Minnesota To the Editor: In their recent article entitled “Early failure of a smalldiameter high-voltage implantable cardioverter-defibrillator lead”,1 Hauser and colleagues state that “The Sprint Quattro Secure model 6947 uses the same materials and is similar in construction to the Sprint Fidelis model 6949 except that its lead body diameter is 8.2 Fr.” This statement implies that the high failure rate of the Sprint Fidelis lead is solely due to its smaller diameter and not other differences in design. There are, however, several key differences in the design and construction of the two leads. First, the crush lumens of the Quattro family of leads (Figure 1) are separate whereas the crush lumens of the Sprint Fidelis (Figure 2) are integrated. Second, the insulation of the coil was PTFE for the Quattro family of leads and ETFE for the Sprint Fidelis. Finally, cross sectional analysis reveals that the relationship
Figure 1 Cross section of Sprint Quattro Secure Lead1. Adapted from Medtronic Specifications Sheet on Quattro leads.
Figure 2
Cross Section of Sprint Quattro Secure Lead2.
of the pace coil with the leads is different. Whereas each coil in the Quattro may be considered to be at the corner of a square, the pace coil of the Fidelis lead is separated from the roughly linear alignment of the other coils. In a crush situation, this change in design could potentially lead to the stacking of multiple coils. The composite effects of these changes, in addition to the smaller diameter, should be considered in future analyses of lead design. In addition, such design aspects should be considered in the post-marketing surveillance of other small diameter high voltage leads such as St. Jude’s 6.3 French Riata ST. Kent R. Nilsson, Jr., MD [email protected] Patrick Hranitzky, MD Department of Medicine Division of Cardiac Electrophysiology Duke University Medical Center Durham, North Carolina
Heart Rhythm, Vol 5, No 1, January 2008 St George’s Hospital London, UK
References 1.
Hauser RG, Kallinen LM, Almquist AK, et al. Early failure of a small-diameter high-voltage implantable cardioverter-defibrillator lead. Heart Rhythm 2007;4:892– 896.
To the Editor—Response: The observations by Catanchin et al are of concern for two reasons: 1) their patient almost certainly died as the result of a Sprint Fidelis lead failure, and 2) all 5 failures occurred in relatively young patients. This is the second patient death associated with a Sprint Fidelis lead failure that has been brought to our attention as the result of our report in Heart Rhythm. The first death was suffered by a patient in North Carolina who had a witnessed cardiac arrest and eventually died; pre-mortem interrogation of his Sprint Fidelis model 6949 revealed noise on the ventricular channel. While death caused by a Sprint Fidelis lead failure may still be rare, it is now a known risk. That Sprint Fidelis failures seem to be occurring in younger and presumably more active patients is consistent with our experience. This finding suggests that stress fatigue is the probable mechanism of failure, and hence more Sprint Fidelis failures are likely. We continue to believe that this lead should be avoided, and that implanted leads require close follow-up and continuous monitoring. Given the known risks associated with revision and extraction, we discourage the routine prophylactic replacement of normally functioning leads. Robert G. Hauser, MD Linda M. Kallinen, BS Adrian K. Almquist, MD Charles C. Gornick, MD William T. Katsiyiannis, MD Minneapolis Heart Institute Minneapolis, Minnesota To the Editor: In their recent article entitled “Early failure of a smalldiameter high-voltage implantable cardioverter-defibrillator lead”,1 Hauser and colleagues state that “The Sprint Quattro Secure model 6947 uses the same materials and is similar in construction to the Sprint Fidelis model 6949 except that its lead body diameter is 8.2 Fr.” This statement implies that the high failure rate of the Sprint Fidelis lead is solely due to its smaller diameter and not other differences in design. There are, however, several key differences in the design and construction of the two leads. First, the crush lumens of the Quattro family of leads (Figure 1) are separate whereas the crush lumens of the Sprint Fidelis (Figure 2) are integrated. Second, the insulation of the coil was PTFE for the Quattro family of leads and ETFE for the Sprint Fidelis. Finally, cross sectional analysis reveals that the relationship
Figure 1 Cross section of Sprint Quattro Secure Lead1. Adapted from Medtronic Specifications Sheet on Quattro leads.
Figure 2
Cross Section of Sprint Quattro Secure Lead2.
of the pace coil with the leads is different. Whereas each coil in the Quattro may be considered to be at the corner of a square, the pace coil of the Fidelis lead is separated from the roughly linear alignment of the other coils. In a crush situation, this change in design could potentially lead to the stacking of multiple coils. The composite effects of these changes, in addition to the smaller diameter, should be considered in future analyses of lead design. In addition, such design aspects should be considered in the post-marketing surveillance of other small diameter high voltage leads such as St. Jude’s 6.3 French Riata ST. Kent R. Nilsson, Jr., MD [email protected] Patrick Hranitzky, MD Department of Medicine Division of Cardiac Electrophysiology Duke University Medical Center Durham, North Carolina