Evaluating Myocardial Injury for Defibrillation Threshold Testing Methods for ICD Implantation (ULV)

Evaluating Myocardial Injury During ICD Implantation Using the Upper Limit of Vulnerability (ULV) Method vs. Standard Defibrillation Threshold Testing

The objective of this study is to evaluate myocardial injury, if any, as quantified by cardiac markers (Troponin-T) in defibrillation threshold (DFT) testing during implantation of implantable cardioverter defibrillators (ICDs) using the upper limit of vulnerability (ULV) method vs. standard defibrillation threshold method.

This is a prospective, randomized (1:1 DFT vs ULV testing), controlled clinical research trial. Patients undergoing ICD implant or device change out will be candidates for this study. Medical records for these patients will be screened prior to enrollment to ensure eligibility for the study. Each patient who is a candidate and who agrees to participate in the study will undergo the standard of care pre-procedure evaluation including a complete medical history evaluation, a complete physical examination and routine laboratory testing including chemistry panel, hematology panel, coagulation panel, a 12-lead electrocardiogram, and a urine pregnancy test (all females of child-bearing age). A candidate patient will be randomly assigned to either the standard DFT testing method group or the ULV testing method group. For the standard DFT testing group, per routine standard of care, the patient will be admitted to the hospital. The study requires a pre-procedure blood test of 3 ml for Troponin-T (TnT) which will be drawn prior to any DFT testing. The blood sample will be sent to the University of California, San Diego (UCSD) central laboratory for processing. The patient will then undergo the scheduled ICD implant procedure in a standard fashion. The standard defibrillation threshold testing will be performed using a low energy shock delivered on T-wave to induce ventricular fibrillation (VF). If VF is induced, the first shock is 25 Joules (J). If success, we will wait 5 minutes and repeat the process. If the 2nd shock yields success, the DFT testing is complete and a 10J safety margin achieved (device shock energy is set at 35J or as clinically indicated determined by treating Cardiac Electrophysiologist). A back-up external defibrillator will always be immediately available in case transvenous shocks fail. Blood pressure will be monitored before and immediately after each shock. After 4 hours, 8 hours and 16 hours post DFT testing, blood samples (3 ml for Troponin-T) will be drawn and sent to the UCSD central laboratory for processing. For the ULV testing group, per routine standard of care, the patient will be admitted to the hospital. The study requires a pre-procedure blood test (3 ml for Troponin-T.) which will be drawn prior to any ULV testing. The blood sample will be sent to the UCSD central laboratory for processing. The patient will then undergo the scheduled ICD implant procedure as is standard clinical care. The ULV testing is performed as follows: for single coil device, a 18J shock will be delivered at 0msec, +20 msec, -20msec and -40msec measured from the peak of the T-wave; for dual coil device, a 18J shock will be delivered at 0msec, -20msec, +20msec, and +40msec measured from the peak of the T-wave. If VF is not induced with any of the above mentioned shocks, the ULV will be considered as 18J and the ICD will be implanted with the first shock strength set at 30 joules or as clinically indicated determined by treating Cardiac Electrophysiologist. If VF is induced, a 25J rescue shock will be delivered as is standard and if successful, the device will be programmed to the maximum output of 35 joules or as clinically indicated determined by treating Cardiac Electrophysiologist. Blood pressure will be monitored before and immediately after each shock. After 4 hours, 8 hours and 16 hours post ULV testing, blood samples (3 ml for Troponin-T) will be drawn and sent to the UCSD central laboratory for processing. Other than the blood tests for Troponin-T, there is no change in routine post-operative management. Patients will be followed every three months, as is standard management for patients with ICDs. The TnT blood draws at 4-hour, 8-hour and 16-hour post implantation will not require longer hospital stay than is standard for patients undergoing ICD implantation. The results of Troponin-T measurement for the study patients will be reviewed by the cardiac electrophysiology (EP) research staff. If myocardial injury is noted (any TnT value >0.1 as per current assay at the UCSD laboratory), the patient will be monitored as is deemed clinically necessary by treating Cardiac Electrophysiologist, including possible repeat TnT measurements for evaluation of myocardial infarction. We will follow standard of care for management of myocardial injury as recommended by the American Heart Association and the American College of Cardiology. Elevated TnT measurements may delay hospitalization, if determined to be clinically necessary. If the repeat TnT measurement is <0.1, then myocardial injury is most unlikely and the positive TnT value is likely due to DFT shocks.

Defibrillation testing, Upper Limit of Vulnerability, ULV, DFT, ICD, implantable cardioverter defibrillator, cardiomyopathy, cardiac arrhythmia, cardiac device testing

Standard Defibrillation Threshold Testing is a procedure in which a low energy shock will be delivered to the heart to induce ventricular fibrillation (VF) followed by a rescue shock to restore sinus rhythm. Process is repeated after 5 minutes.

Upper Limit of Vulnerability Testing is a procedure in which four 18J shocks will be delivered at specified intervals. If VF is induced, then a 25 J rescue shock will be delivered.

Once the ICD is implanted, Standard Defibrillation Threshold (DFT) testing will begin. A low energy shock will be delivered to the heart at the peak of the T wave to induce ventricular fibrillation (VF). Once VF is induced, a rescue shock of 25J will be delivered to restore sinus rhythm. This process will be repeated once more after 5 minutes.

Once the ICD is implanted, Upper Limit of Vulnerability (ULV) testing will commence. An 18 J shock will be delivered will at different points from the t-wave. If VF is not induced with any of these shocks, then the ULV will be considered to be 18J. If VF is induced, then a 25 J rescue shock will be delivered.

Myocardial damage will be evaluated by cardiac troponin (cTNT) lab collection before and then after ULV or DFT testing at 4 hours, 8 hours, and 20 hours.

the DFT group cardiac troponin (cTNT) values were compared to the subjects within the ULV group that required VF induction.

The DFT group was compared to the ULV subgroup that did not require ventricular fibrillation (VF) induction. Cardiac troponin (cTNT) levels were analyzed.

Inclusion Criteria: Patients eligible to receive an ICD implant or change out. Patients with a single or dual coil right ventricle (RV) defibrillation lead located in the RV apex. Patients greater than 18 years of age. Patients willing and able to give informed consent. Patients who have insurance which may cover additional hospital stay if myocardial injury resulted from testing Exclusion Criteria: Patients with medical conditions that would limit study participation. Patients that are pregnant

Swerdlow CD, Shehata M, Chen PS. Using the upper limit of vulnerability to assess defibrillation efficacy at implantation of ICDs. Pacing Clin Electrophysiol. 2007 Feb;30(2):258-70. doi: 10.1111/j.1540-8159.2007.00659.x.

Day JD, Doshi RN, Belott P, Birgersdotter-Green U, Behboodikhah M, Ott P, Glatter KA, Tobias S, Frumin H, Lee BK, Merillat J, Wiener I, Wang S, Grogin H, Chun S, Patrawalla R, Crandall B, Osborn JS, Weiss JP, Lappe DL, Neuman S. Inductionless or limited shock testing is possible in most patients with implantable cardioverter- defibrillators/cardiac resynchronization therapy defibrillators: results of the multicenter ASSURE Study (Arrhythmia Single Shock Defibrillation Threshold Testing Versus Upper Limit of Vulnerability: Risk Reduction Evaluation With Implantable Cardioverter-Defibrillator Implantations). Circulation. 2007 May 8;115(18):2382-9. doi: 10.1161/CIRCULATIONAHA.106.663112. Epub 2007 Apr 30.

Chen PS, Shibata N, Dixon EG, Martin RO, Ideker RE. Comparison of the defibrillation threshold and the upper limit of ventricular vulnerability. Circulation. 1986 May;73(5):1022-8. doi: 10.1161/01.cir.73.5.1022.

Chen PS, Feld GK, Kriett JM, Mower MM, Tarazi RY, Fleck RP, Swerdlow CD, Gang ES, Kass RM. Relation between upper limit of vulnerability and defibrillation threshold in humans. Circulation. 1993 Jul;88(1):186-92. doi: 10.1161/01.cir.88.1.186.

Hwang C, Swerdlow CD, Kass RM, Gang ES, Mandel WJ, Peter CT, Chen PS. Upper limit of vulnerability reliably predicts the defibrillation threshold in humans. Circulation. 1994 Nov;90(5):2308-14. doi: 10.1161/01.cir.90.5.2308.

Martin DJ, Chen PS, Hwang C, Gang ES, Mandel WJ, Peter CT, Swerdlow CD. Upper limit of vulnerability predicts chronic defibrillation threshold for transvenous implantable defibrillators. J Cardiovasc Electrophysiol. 1997 Mar;8(3):241-8. doi: 10.1111/j.1540-8167.1997.tb00786.x.

Birgersdotter-Green U, Undesser K, Fujimura O, Feld GK, Kass RM, Mandel WJ, Peter CT, Chen PS. Correlation of acute and chronic defibrillation threshold with upper limit of vulnerability determined in normal sinus rhythm. J Interv Card Electrophysiol. 1999 Jul;3(2):155-61. doi: 10.1023/a:1009825731592.

Swerdlow CD, Davie S, Ahern T, Chen PS. Comparative reproducibility of defibrillation threshold and upper limit of vulnerability. Pacing Clin Electrophysiol. 1996 Dec;19(12 Pt 1):2103-11. doi: 10.1111/j.1540-8159.1996.tb03285.x.

Swerdlow CD, Ahern T, Kass RM, Davie S, Mandel WJ, Chen PS. Upper limit of vulnerability is a good estimator of shock strength associated with 90% probability of successful defibrillation in humans with transvenous implantable cardioverter-defibrillators. J Am Coll Cardiol. 1996 Apr;27(5):1112-8. doi: 10.1016/0735-1097(95)00603-6.

Swerdlow CD. Implantation of cardioverter defibrillators without induction of ventricular fibrillation. Circulation. 2001 May 1;103(17):2159-64. doi: 10.1161/01.cir.103.17.2159.

Green UB, Garg A, Al-Kandari F, Ungab G, Tone L, Feld GK. Successful implantation of cardiac defibrillators without induction of ventricular fibrillation using upper limit of vulnerability testing. J Interv Card Electrophysiol. 2003 Feb;8(1):71-5. doi: 10.1023/a:1022304417889.

Swerdlow C, Shivkumar K, Zhang J. Determination of the upper limit of vulnerability using implantable cardioverter-defibrillator electrograms. Circulation. 2003 Jun 24;107(24):3028-33. doi: 10.1161/01.CIR.0000074220.19414.18. Epub 2003 Jun 16.

Shehata M, Belk P, Kremers M, Saba S, Cao J, Swerdlow CD. Automatic determination of timing intervals for upper limit of vulnerability using ICD electrograms. Pacing Clin Electrophysiol. 2008 Jun;31(6):691-700. doi: 10.1111/j.1540-8159.2008.01072.x.