Defibrillator Leads at a Large-Volume Implanting Hospital
Defibrillator Leads at a Large-Volume Implanting Hospital
This investigator-initiated study confirmed many of the findings of most multicenter or smaller single-hospital trials. Specifically, our study identified a correlation between recalled lead status and mortality that was independent of known mortality risk factors such as age, congestive heart failure, and ejection fraction. Although the etiology of death was largely unknown, it is intriguing to consider that these leads may have impacted patient mortality. Second, this study demonstrated that recalled leads fail sooner than non-recalled leads. In addition, the St. Jude recalled leads (Riata and Riata ST) appeared to perform equivalent to non-recalled leads with respect to lead survival. The same could not be said of the Medtronic Sprint Fidelis lead, which had a significantly higher failure rate than the other non-recalled leads (Medtronic, St. Jude, and Boston Scientific). The present study may be distinguishable from those earlier trials based on it being a single large-volume implanting hospital examining lead performance over 16 years. In addition, this study examined all aspects of the implant procedure including patient characteristics, implant approach, and number of leads implanted, and included a very detailed lead construction design analysis.
A multivariable analysis in the current study demonstrated a number of unique findings. First, for every year increase in patient age, there was a 2% decrease in lead failure. Gerard and colleagues also found that younger age was associated with a higher rate of lead failure in the recalled Medtronic Sprint Fidelis lead. Their analysis looked at certain age cut-offs, whereas we analyzed age as a continuous variable. Our findings appeared to generalize those of Gerard and colleagues to all three US manufacturers regardless of recalled lead status. Second, history of percutaneous coronary intervention was associated with a 74% increase in lead failure. The reason for this is unclear. Third, atrial fibrillation and/or atrial flutter at the time of implant was associated with a lower risk of lead failure than other rhythms (paced rhythm, heart block, bundle branch block, or sinus rhythm). The reason for this finding is not entirely clear; however, it might have been related to the presence of fewer leads, since an atrial lead implant would have been less likely implanted in those with atrial dysrhythmias at the time of the procedure. This appeared to be the case in univariate, but not multivariable analysis. Fourth, the combination of polyurethane and silicone was associated with a higher lead failure rate than silicone alone. Fifth, a single coil lead had a 74% less risk of failure than a dual coil lead. The increased complexity of the latter's lead design might explain this increased failure rate. Interestingly, the Sudden Cardiac Death in Heart Failure trial failed to demonstrate any improved outcome measures from the addition of a second coil lead as compared to a single coil lead. Finally, the presence of a recalled lead status was associated with twice the risk of lead failure vs those without such a status. The increased risk of failure in recalled leads was also demonstrated by the University of Pittsburgh Medical Center team. Importantly, Groarke and his team demonstrated that these lead failures have significant cost implications that undermine the cost effectiveness of implantable defibrillators as a whole.
Surprisingly, the current study failed to demonstrate a significant independent effect of lead diameter, type of fixation, type of lead cable construction, or even lumen design (compression lumens and number of lumens). At first glance, one would think that lead diameter must play a significant role in lead design. Intuitively, a more complicated lead design in a smaller volume must be more prone to more error. But this analysis is complicated by the fact that over 40% of the Medtronic and St. Jude leads in this study were considered small diameter and/or were recalled. Our failure to conclusively prove that diameter is an important variable stands in contrast with other less-detailed lead construction studies which seemed to show an effect of lead diameter on failure.
Our study has a number of important limitations. First, it was a non-randomized retrospective study. There is a need for a large, prospective, independent, longitudinal lead survival trial involving all major manufacturers' leads with consistent detailed follow-up. The outcome of such a trial may shed further insight on lead failure. Second, only known captured lead failures were included in the failure group, and therefore the reported lead failure rates may significantly underestimate the true lead failure number. Third, mortality as determined via the Social Security Death Index is a very accurate survival tool, and thereby the association between mortality and recalled lead status appears real. However, the etiology of that mortality and the cause and effect linking lead failure to mortality remains unclear. Fourth, the study included implants between February 1, 1996 and December 31, 2011. The Medtronic Sprint Fidelis lead recall occurred in 2007, which permitted widespread patient notification and lead surveillance with a significant follow-up period following the notification. A medical device advisory regarding problems with the Riata and Riata ST leads was issued by St. Jude Medical on November 28, 2011 (33 days before the end of our trial). This left almost no time to notify the patients and begin any significant lead surveillance and/or follow-up program.
Discussion
This investigator-initiated study confirmed many of the findings of most multicenter or smaller single-hospital trials. Specifically, our study identified a correlation between recalled lead status and mortality that was independent of known mortality risk factors such as age, congestive heart failure, and ejection fraction. Although the etiology of death was largely unknown, it is intriguing to consider that these leads may have impacted patient mortality. Second, this study demonstrated that recalled leads fail sooner than non-recalled leads. In addition, the St. Jude recalled leads (Riata and Riata ST) appeared to perform equivalent to non-recalled leads with respect to lead survival. The same could not be said of the Medtronic Sprint Fidelis lead, which had a significantly higher failure rate than the other non-recalled leads (Medtronic, St. Jude, and Boston Scientific). The present study may be distinguishable from those earlier trials based on it being a single large-volume implanting hospital examining lead performance over 16 years. In addition, this study examined all aspects of the implant procedure including patient characteristics, implant approach, and number of leads implanted, and included a very detailed lead construction design analysis.
A multivariable analysis in the current study demonstrated a number of unique findings. First, for every year increase in patient age, there was a 2% decrease in lead failure. Gerard and colleagues also found that younger age was associated with a higher rate of lead failure in the recalled Medtronic Sprint Fidelis lead. Their analysis looked at certain age cut-offs, whereas we analyzed age as a continuous variable. Our findings appeared to generalize those of Gerard and colleagues to all three US manufacturers regardless of recalled lead status. Second, history of percutaneous coronary intervention was associated with a 74% increase in lead failure. The reason for this is unclear. Third, atrial fibrillation and/or atrial flutter at the time of implant was associated with a lower risk of lead failure than other rhythms (paced rhythm, heart block, bundle branch block, or sinus rhythm). The reason for this finding is not entirely clear; however, it might have been related to the presence of fewer leads, since an atrial lead implant would have been less likely implanted in those with atrial dysrhythmias at the time of the procedure. This appeared to be the case in univariate, but not multivariable analysis. Fourth, the combination of polyurethane and silicone was associated with a higher lead failure rate than silicone alone. Fifth, a single coil lead had a 74% less risk of failure than a dual coil lead. The increased complexity of the latter's lead design might explain this increased failure rate. Interestingly, the Sudden Cardiac Death in Heart Failure trial failed to demonstrate any improved outcome measures from the addition of a second coil lead as compared to a single coil lead. Finally, the presence of a recalled lead status was associated with twice the risk of lead failure vs those without such a status. The increased risk of failure in recalled leads was also demonstrated by the University of Pittsburgh Medical Center team. Importantly, Groarke and his team demonstrated that these lead failures have significant cost implications that undermine the cost effectiveness of implantable defibrillators as a whole.
Surprisingly, the current study failed to demonstrate a significant independent effect of lead diameter, type of fixation, type of lead cable construction, or even lumen design (compression lumens and number of lumens). At first glance, one would think that lead diameter must play a significant role in lead design. Intuitively, a more complicated lead design in a smaller volume must be more prone to more error. But this analysis is complicated by the fact that over 40% of the Medtronic and St. Jude leads in this study were considered small diameter and/or were recalled. Our failure to conclusively prove that diameter is an important variable stands in contrast with other less-detailed lead construction studies which seemed to show an effect of lead diameter on failure.
Study Limitations
Our study has a number of important limitations. First, it was a non-randomized retrospective study. There is a need for a large, prospective, independent, longitudinal lead survival trial involving all major manufacturers' leads with consistent detailed follow-up. The outcome of such a trial may shed further insight on lead failure. Second, only known captured lead failures were included in the failure group, and therefore the reported lead failure rates may significantly underestimate the true lead failure number. Third, mortality as determined via the Social Security Death Index is a very accurate survival tool, and thereby the association between mortality and recalled lead status appears real. However, the etiology of that mortality and the cause and effect linking lead failure to mortality remains unclear. Fourth, the study included implants between February 1, 1996 and December 31, 2011. The Medtronic Sprint Fidelis lead recall occurred in 2007, which permitted widespread patient notification and lead surveillance with a significant follow-up period following the notification. A medical device advisory regarding problems with the Riata and Riata ST leads was issued by St. Jude Medical on November 28, 2011 (33 days before the end of our trial). This left almost no time to notify the patients and begin any significant lead surveillance and/or follow-up program.
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