- Email: [email protected]
P2-59
S158
Heart Rhythm, Vol 3, No 5, May Supplement 2006
bpm. Shock energy programming was left to the implanting physician’s discretion in the tailored arm. Episodes were retrospectively separated based on the arrhythmia type and median ventricular rate at initial detection. A ‘low’ energy shock was defined as a delivered shock energy: A) ⬍ 18 J for monomorphic VT (MVTs) ⱕ 200 bpm, and B) ⬍ 28J for MVTs ⬎ 200 bpm and polymorphic VT/VF (PVT/VF). P-values were calculated with Fisher’s exact test. Results: ICDs were implanted for a mixture of primary (46%) and secondary (54%) prevention indications. A high energy first shock significantly decreased the first shock failure rate from 36% to 7% for PVT/VF (p ⫽ 0.01). High energy first shocks had a similar efficacy to low energy shocks for both fast and slower MVTs. First shock failure rate by rhythm and shock energy Delivered energy of first shock
PVT/VF MVT V rate ⬎ 200 bpm MVT V rate ⱕ 200 bpm
Low
High
P-value
36% (5/14) 13% (2/16) 19% (6/32)
7% (5/70) 17% (10/58) 20% (18/89)
0.01 1.00 1.00
% 1st shocks failed (# episodes with 1st shock failure / # shocked episodes) Conclusions: A high energy first shock reduces the need for multiple shocks for PVT/VF but not for MVT. High energy (ⱖ28J) first shocks programmed for faster ventricular arrhythmias may help reduce patient morbidity by reducing the need for multiple shocks. P2-59 ADVANCES IN DEFIBRILLATION THRESHOLD REDUCTION: RESULTS OF THE SHORT SUBCUTANEOUS COIL CLINICAL STUDY Roland W. M. Bullens, PhD, Slawomir Sielski, MD, Jacek Kubica, MD, PhD, Wojciech Krupa, MD, Ryszard Dobosiewicz, MD, Boguslaw Grzegorzewski, MD, Artur Filipecki, MD, Janusz Prokopczuk, MD, Karel F. A. A. Smits, MS and Michael R. S. Hill, PhD. Medtronic, Maastricht, The Netherlands, Academic Hospital Bydgoszcz, Bydgoszcz, Poland, Silesian Medical University, Katowice, Poland and Silesian Center of Heart Diseases, Zabrze, Poland. Background: Patients who receive an ICD system undergo defibrillation threshold (DFT) testing at implant. For those patients who have a DFT which is unacceptably high, a subcutaneous (SQ) lead can be used to lower the DFT. A new SQ lead (model 6996S, based on the 6996) was designed, with the major difference of a shortened electrode coil from 25 to 15 cm. This allows easier implantation of the lead using a shorter implant tool and less length of the lead exposed to external forces, thereby limiting the potential chance of a lead fracture. Purpose: The purpose of the study was to investigate whether the addition of a short SQ lead is able to reduce the DFT when compared to a standard ICD system (without SQ lead) in a clinical setting. Methods: The investigation was performed in patients undergoing the implantation of an ICD system. The DFT was determined twice during the implantation with a binary search protocol, once with only the transvenous ICD system (RV-⬎Can) and once with the system including the short SQ lead (RV-⬎Can⫹SQ). The order in which the implanted systems were tested was randomized. Results: Eighteen patients were included in this analysis. The average DFT and standard deviation of RV-Can and RV-Can⫹SQ were 12.5 ⫾ 8.7 and 9.8 ⫾ 6.3 respectively. The DFT (p⫽0.2950, Wilcoxon signed rank test) and the standard deviation (p⫽0.154, Levene’s test) were reduced with the addition of the short SQ lead. The addition of the short SQ lead significantly reduced the DFT in patients with a high DFT (DFT higher than the median) in a Can-⬎RV system (p⬍0.05, Wilcoxon signed rank test).
Conclusions: The preliminary results show that the addition of the short SQ lead can reduce DFT in patients with a high DFT. P2-60 MECHANISMS OF DEVICE MISCLASSIFICATION OF ARRHYTHMIC EPISODES IN THE SINGLE CHAMBER ARM OF THE DETECT SVT TRIAL Michael Glikson, MD, David Luria, MD, Robyn McClelland, PhD, Bill Bamlet, MS, E Wayne Grogan, MD, Michael Pelini, MD, Charles Lanzarotti, MD, Scott Sakaguchi, MD and Paul A. Friedman, MD. Sheba Medical Center, Tel Hashomer, Israel, University of Washington, Seattle, WA, Mayo Clinic, Rochester, MN, Wisconsin Heart, Madison, WI, Summa Health System, Akron City Campus, Akron, OH, Wisconsin Center for Clinical Research, LLC, Milwaukee, WI and University of Minnesota, Minneapolis, MN. Introduction: Implantable defibrillator (ICD) inappropriate shocks are common, but the mechanisms in some current generation ICDs have not been thoroughly studied. The Detect SVT trial was a randomized controlled study which compared arrhythmia diagnosis using single chamber (SC) vs. dual chamber (DC) detection in 400 DC ICD recipients followed for six months. The purpose of this substudy was to analyze the cause of diagnosis errors in ICDs programmed using single chamber detection. Methods: All pts had standard ICD indications, and received a DC device manufactured by St Jude Medical. In the single chamber arm of the study, detection was programmed using strictly specified parameters, with a combination of 2 of 3 discriminators required to diagnose ventricular tachycardia (VT). Discriminators included sudden onset (SO) of 100 msec, interval stability (IS) of 80 msec and morphology discrimination (MD) mismatch of 5/8 beats at a 60% level. All episodes were diagnosed as VT or supraventricular arrhythmia (SVT) based on blinded core lab review. The cause of inappropriate diagnosis was determined by the site investigator. Results: Of 819 (417/402 VT/SVT ) episodes analyzed, 191 (23%) were misclassified by the device using the 2/3 requirement to diagnose VT . Causes of misclassifications are listed in the Table Adjudicated rhythm during the episode
Reason for misdiagnosis by device SO misclassification IS misclassification MD misclassification Ventricular oversensing * Other
Normal sinus rhythm (NSR) (N⫽27)
SVT (N⫽160)
VT (N⫽4)
1 2 3 26
119 (74%) 86 (54%) 62 (39%) 0
2 (50%) 1 (25%) 3 (75%) 0
(4%) (7%) (11%) (96%)
1 (4%)
5 (3%)**
0
* The main cause of misclassification of NSR was T wave oversensing. ** Others included expired timers and SVT in VF zone Conclusions: Individual single chamber discriminators frequently misdiagnose SVT as VT. Use of a combination of discriminators improves their performance. Programming sensing to prevent T wave oversensing should be used liberally in these devices, and careful tailoring of detection criteria should be considered. P2-61 PREVALENCE OF POST-SHOCK PACING IN PATIENTS WITH IMPLANTABLE DEFIBRILLATORS William J. Havel, PhD, Athula I. Abeyratne, PhD and Paul J. De Groot, MS. Medtronic, Inc., Minneapolis, MN. Background: The occasional presence of asystolic pauses following monophasic defibrillation shocks in recipients of 1st & 2nd generation ICDs
Heart Rhythm, Vol 3, No 5, May Supplement 2006
bpm. Shock energy programming was left to the implanting physician’s discretion in the tailored arm. Episodes were retrospectively separated based on the arrhythmia type and median ventricular rate at initial detection. A ‘low’ energy shock was defined as a delivered shock energy: A) ⬍ 18 J for monomorphic VT (MVTs) ⱕ 200 bpm, and B) ⬍ 28J for MVTs ⬎ 200 bpm and polymorphic VT/VF (PVT/VF). P-values were calculated with Fisher’s exact test. Results: ICDs were implanted for a mixture of primary (46%) and secondary (54%) prevention indications. A high energy first shock significantly decreased the first shock failure rate from 36% to 7% for PVT/VF (p ⫽ 0.01). High energy first shocks had a similar efficacy to low energy shocks for both fast and slower MVTs. First shock failure rate by rhythm and shock energy Delivered energy of first shock
PVT/VF MVT V rate ⬎ 200 bpm MVT V rate ⱕ 200 bpm
Low
High
P-value
36% (5/14) 13% (2/16) 19% (6/32)
7% (5/70) 17% (10/58) 20% (18/89)
0.01 1.00 1.00
% 1st shocks failed (# episodes with 1st shock failure / # shocked episodes) Conclusions: A high energy first shock reduces the need for multiple shocks for PVT/VF but not for MVT. High energy (ⱖ28J) first shocks programmed for faster ventricular arrhythmias may help reduce patient morbidity by reducing the need for multiple shocks. P2-59 ADVANCES IN DEFIBRILLATION THRESHOLD REDUCTION: RESULTS OF THE SHORT SUBCUTANEOUS COIL CLINICAL STUDY Roland W. M. Bullens, PhD, Slawomir Sielski, MD, Jacek Kubica, MD, PhD, Wojciech Krupa, MD, Ryszard Dobosiewicz, MD, Boguslaw Grzegorzewski, MD, Artur Filipecki, MD, Janusz Prokopczuk, MD, Karel F. A. A. Smits, MS and Michael R. S. Hill, PhD. Medtronic, Maastricht, The Netherlands, Academic Hospital Bydgoszcz, Bydgoszcz, Poland, Silesian Medical University, Katowice, Poland and Silesian Center of Heart Diseases, Zabrze, Poland. Background: Patients who receive an ICD system undergo defibrillation threshold (DFT) testing at implant. For those patients who have a DFT which is unacceptably high, a subcutaneous (SQ) lead can be used to lower the DFT. A new SQ lead (model 6996S, based on the 6996) was designed, with the major difference of a shortened electrode coil from 25 to 15 cm. This allows easier implantation of the lead using a shorter implant tool and less length of the lead exposed to external forces, thereby limiting the potential chance of a lead fracture. Purpose: The purpose of the study was to investigate whether the addition of a short SQ lead is able to reduce the DFT when compared to a standard ICD system (without SQ lead) in a clinical setting. Methods: The investigation was performed in patients undergoing the implantation of an ICD system. The DFT was determined twice during the implantation with a binary search protocol, once with only the transvenous ICD system (RV-⬎Can) and once with the system including the short SQ lead (RV-⬎Can⫹SQ). The order in which the implanted systems were tested was randomized. Results: Eighteen patients were included in this analysis. The average DFT and standard deviation of RV-Can and RV-Can⫹SQ were 12.5 ⫾ 8.7 and 9.8 ⫾ 6.3 respectively. The DFT (p⫽0.2950, Wilcoxon signed rank test) and the standard deviation (p⫽0.154, Levene’s test) were reduced with the addition of the short SQ lead. The addition of the short SQ lead significantly reduced the DFT in patients with a high DFT (DFT higher than the median) in a Can-⬎RV system (p⬍0.05, Wilcoxon signed rank test).
Conclusions: The preliminary results show that the addition of the short SQ lead can reduce DFT in patients with a high DFT. P2-60 MECHANISMS OF DEVICE MISCLASSIFICATION OF ARRHYTHMIC EPISODES IN THE SINGLE CHAMBER ARM OF THE DETECT SVT TRIAL Michael Glikson, MD, David Luria, MD, Robyn McClelland, PhD, Bill Bamlet, MS, E Wayne Grogan, MD, Michael Pelini, MD, Charles Lanzarotti, MD, Scott Sakaguchi, MD and Paul A. Friedman, MD. Sheba Medical Center, Tel Hashomer, Israel, University of Washington, Seattle, WA, Mayo Clinic, Rochester, MN, Wisconsin Heart, Madison, WI, Summa Health System, Akron City Campus, Akron, OH, Wisconsin Center for Clinical Research, LLC, Milwaukee, WI and University of Minnesota, Minneapolis, MN. Introduction: Implantable defibrillator (ICD) inappropriate shocks are common, but the mechanisms in some current generation ICDs have not been thoroughly studied. The Detect SVT trial was a randomized controlled study which compared arrhythmia diagnosis using single chamber (SC) vs. dual chamber (DC) detection in 400 DC ICD recipients followed for six months. The purpose of this substudy was to analyze the cause of diagnosis errors in ICDs programmed using single chamber detection. Methods: All pts had standard ICD indications, and received a DC device manufactured by St Jude Medical. In the single chamber arm of the study, detection was programmed using strictly specified parameters, with a combination of 2 of 3 discriminators required to diagnose ventricular tachycardia (VT). Discriminators included sudden onset (SO) of 100 msec, interval stability (IS) of 80 msec and morphology discrimination (MD) mismatch of 5/8 beats at a 60% level. All episodes were diagnosed as VT or supraventricular arrhythmia (SVT) based on blinded core lab review. The cause of inappropriate diagnosis was determined by the site investigator. Results: Of 819 (417/402 VT/SVT ) episodes analyzed, 191 (23%) were misclassified by the device using the 2/3 requirement to diagnose VT . Causes of misclassifications are listed in the Table Adjudicated rhythm during the episode
Reason for misdiagnosis by device SO misclassification IS misclassification MD misclassification Ventricular oversensing * Other
Normal sinus rhythm (NSR) (N⫽27)
SVT (N⫽160)
VT (N⫽4)
1 2 3 26
119 (74%) 86 (54%) 62 (39%) 0
2 (50%) 1 (25%) 3 (75%) 0
(4%) (7%) (11%) (96%)
1 (4%)
5 (3%)**
0
* The main cause of misclassification of NSR was T wave oversensing. ** Others included expired timers and SVT in VF zone Conclusions: Individual single chamber discriminators frequently misdiagnose SVT as VT. Use of a combination of discriminators improves their performance. Programming sensing to prevent T wave oversensing should be used liberally in these devices, and careful tailoring of detection criteria should be considered. P2-61 PREVALENCE OF POST-SHOCK PACING IN PATIENTS WITH IMPLANTABLE DEFIBRILLATORS William J. Havel, PhD, Athula I. Abeyratne, PhD and Paul J. De Groot, MS. Medtronic, Inc., Minneapolis, MN. Background: The occasional presence of asystolic pauses following monophasic defibrillation shocks in recipients of 1st & 2nd generation ICDs