Orthostatic increase in defibrillation threshold leading to defibrillation failure and prolonged cardiac arrest in a sitting position: Lessons from a patient’s near-fatal experience (2016)

Tabled 1KEY TEACHING POINTS•A clinically significant increase in defibrillation threshold (DFT) may occur in the upright body position, especially in patients with severe obesity.•Implantation of an azygos vein coil may substantially reduce DFT.•Orthostatic DFT testing may help identify and reduce the chance of failure to defibrillate in high-risk patients. Open table in a new tab IntroductionIt has previously been reported that patients with an implantable cardioverter-defibrillator (ICD) may have a slightly higher defibrillation threshold (DFT) in an upright position compared to a supine position.1Schauerte P. Diem B. Ziegert K. Franke A. Hanrath P. Stellbrink C. Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.J Cardiovasc Electrophysiol. 1998; 9: 696-702Crossref PubMed Scopus (5) Google Scholar However, the significance of this and the potential impact on clinical practice remains unclear. We report a case of defibrillation failure caused by an increase in DFT in the upright position, leading to prolonged, near-fatal cardiac arrest in a patient who had previous ICD implantation including successful DFT testing in a supine position. ICD system revision with addition of an azygos vein coil successfully corrected this condition, as demonstrated by orthostatic DFT testing.Case reportThe patient is a 47-year-old man with a prior history of nonischemic, dilated cardiomyopathy and ejection fraction 15%–20%. He underwent initial implantation of a single-chamber, single-coil ICD (Protecta VR D334VRG; Medtronic, Minneapolis, MN) for primary prevention in October 2012. The patient’s past medical history is also significant for morbid obesity, hypertension, type II diabetes, and renal insufficiency. Because of the patient’s body habitus, nonischemic cardiomyopathy, and young age, DFT testing was performed at the time of implant. After induction of ventricular fibrillation (VF) by T wave shock, a 15 J shock failed but a follow-up 25 J shock from the ICD successfully restored sinus rhythm. The patient’s device has a 35 J maximal output with a 10 J safety margin maintained. After the uneventful ICD implantation, he remained stable until recently, when he developed an episode of VF during sleep, with successful cardioversion by a single 35 J shock from the ICD. An evaluation including stress echocardiography was negative for ischemia. No additional coronary angiogram was performed owing to baseline renal insufficiency and because he already had two previous coronary angiograms within the last 5 years that showed no significant obstructive coronary artery disease. Conservative medical management was therefore recommended and the patient’s heart failure management was intensified with close follow-up by his cardiologist.Five months after the initial VF event and despite an apparent stable heart failure status, the patient developed sudden syncope without prodrome while sitting in a chair at home and was later found to be in cardiac arrest. According to the family, the patient was able to maintain an upright position in the chair. Subsequent ICD interrogation showed VF that was appropriately detected and six consecutive, maximal-energy shocks at 35 J (including a reversed polarity with the last shock) were delivered but failed to terminate the VF (Figure 1A–C). After exhaustion of device therapy, the patient remained in VF for approximately 6–7 minutes until paramedics arrived with an automated external defibrillator. The patient was immediately placed in the supine position and a single shock from the automated external defibrillator successfully converted the patient back into sinus rhythm (Figure 1D). After the patient was placed in the supine position, he subsequently developed 3 more VF episodes in the field, all of which were successfully detected and treated by the ICD (Figure 1E and F). The patient was initially transferred to a nearby hospital but was subsequently transferred to Borgess Medical Center for definitive management. Two days after the initial event, the patient did develop another episode of VF while supine in the hospital, which was again successfully detected and treated by the ICD with a 35 J shock. Following successful resuscitation including a cooling protocol, he was able to make a complete recovery with minimal residual neurologic deficit. Of note, chest x-ray performed in both the supine and upright positions demonstrated an orthostatic shift in the ICD can position relative to the heart, but no significant change in the lead position was found as compared to the one at initial implant (Figure 2A–D).Figure 2Posterior-anterior (PA) and lateral views of the implantable cardioverter-defibrillator (ICD) system in both supine and upright positions. A, B: Chest x-ray in the supine position. C, D: Patient’s ICD can was seen to be inferiorly (C) and anteriorly displaced (D) in the upright position compared to the supine one (A, B). In the upright position, the shock vector between the right ventricular coil and can (their midpoints connected with dashed lines) appears to encompass less of the cardiac mass, especially the left ventricle (D). E, F: PA (E) and lateral (F) views in the upright position after addition of an azygos vein coil (arrow). The shock vector between the coils and can now encompasses more of the left ventricle in the upright position (F).View Large Image Figure ViewerDownload (PPT)Because of the apparent dependence of successful defibrillation on body position and the relatively high DFT during the initial implant, we elected to revise the patient’s ICD system with addition of an azygos vein coil and subsequently performed DFT testing in a supine as well as in an upright position.The patient was taken to the electrophysiology lab, where the left precordium was prepared and draped in the usual fashion. The axillary vein was accessed and the azygos vein was engaged using a 6 F Judkins-right-4 (JR4) diagnostic coronary catheter, as described by Cooper et al,2Cooper J.A. Latacha M.P. Soto G.E. Garmany R.G. Gleva M.J. Chen J. Faddis M.N. Smith T.W. The azygos defibrillator lead for elevated defibrillation thresholds: implant technique, lead stability, and patient series.Pacing Clin Electrophysiol. 2008; 31: 1405-1410Crossref PubMed Scopus (38) Google Scholar and a Storq wire (Johnson & Johnson Medical, NV, Diegem, Belgium). A 9 F long sheath was advanced over the JR4 and Storq wire, passing the initial torturous portion of the azygos vein. This allowed successful implantation of an azygos coil posterior to the heart (Figure 2E and F). At the end of the procedure, VF was induced and a 15 J shock from the device was able to successfully defibrillate the patient (not shown). The patient underwent further DFT testing the next morning in an upright position. The head of the bed was propped up about 70–80 degrees until the patient was in an upright posture similar to the one that he was in during the initial prolonged cardiac arrest. VF was again induced by T wave shock. Following successful detection of VF, an initial 25 J shock was purposefully delivered using the previous right ventricular (RV) coil–to–ICD can configuration to confirm that the failure to defibrillate was due to an increase in DFT in the upright position (Figure 3A). This indeed failed to terminate the VF. Immediately after that, with the patient still in VF in an upright position, a second 15 J manual shock using the new configuration (B>AX, RV coil to azygos coil/ICD can) incorporating the azygos coil was delivered within 10 seconds and successfully defibrillated the patient (Figure 3B). The patient tolerated the procedure well and was discharged home on amiodarone to suppress ventricular arrhythmias that may trigger further VF. At his post hospital follow-up one month after the event, the patient had completely recovered, with no residual neurologic deficit or recurrent VF episodes.Figure 3Defibrillation threshold testing when patient was in a sitting position with and without the azygos coil in the shock circuit. A: Using the initial right ventricular (RV) coil–to–ICD can configuration, a 25 J shock failed to defibrillate the patient. B: Immediately following the failure using the old configuration, a 15 J manual shock using the new RV coil–to–azygos vein/ICD can configuration successfully converted the patient to a paced rhythm.View Large Image Figure ViewerDownload (PPT)DiscussionThis case illustrates the potential critical impact of orthostatic increase in DFT on survival in certain clinical situations, and it is thought-provoking that orthostatic DFT testing is yet to become part of our routine electrophysiology practice even in patients at high risk for VF. It also demonstrates that modification of the shock vector utilizing an azygos coil can substantially reduce the DFT in both supine and upright positions.Influence of body position on DFT has long been studied by Schauerte et al,1Schauerte P. Diem B. Ziegert K. Franke A. Hanrath P. Stellbrink C. Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.J Cardiovasc Electrophysiol. 1998; 9: 696-702Crossref PubMed Scopus (5) Google Scholar who found a significant increase in DFT in an upright position compared to the supine position. However, the mean magnitude of this increase is relatively small, about 1.9–2.0 J, which would not be expected to cause complete failure to defibrillate in the patient presented here, since a 10 J safety margin was observed during the initial implant.1Schauerte P. Diem B. Ziegert K. Franke A. Hanrath P. Stellbrink C. Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.J Cardiovasc Electrophysiol. 1998; 9: 696-702Crossref PubMed Scopus (5) Google Scholar, 3Marchlinski F.E. Flores B. Miller J.M. Gottlieb C.D. Hargrove 3rd, W.C. Relation of the intraoperative defibrillation threshold to successful postoperative defibrillation with an automatic implantable cardioverter defibrillator.Am J Cardiol. 1988; 62: 393-398Abstract Full Text PDF PubMed Scopus (112) Google Scholar Our patient’s relatively increased DFT at baseline and subsequent treatment with amiodarone in the hospital may have contributed to the failure to defibrillate. However, the main factor in this case appears to be the orthostatic increase in DFT when the patient was in an upright position. This is supported by the three consecutive, successful shocks from the device when the patient was placed in a supine position shortly after he had already failed 6 maximal-energy shocks in a sitting position and after greater than 7 minutes of continuous VF. Presence of VF as short as 10 seconds has been shown to increase DFT significantly, and prolonged cardiac arrest due to VF was reported to markedly increase the energy requirement for successful defibrillation.4Leng C.T. Paradis N.A. Calkins H. Berger R.D. Lardo A.C. Rent K.C. Halperin H.R. Resuscitation after prolonged ventricular fibrillation with use of monophasic and biphasic waveform pulses for external defibrillation.Circulation. 2000; 101: 2968-2974Crossref PubMed Scopus (52) Google Scholar, 5Gradaus R. Bode-Schnurbus L. Weber M. Rötker J. Hammel D. Breithardt G. Böcker D. Effect of ventricular fibrillation duration on the defibrillation threshold in humans.Pacing Clin Electrophysiol. 2002; 25: 14-19Crossref PubMed Scopus (16) Google Scholar All five spontaneous VF episodes (one before the recent cardiac arrest and four afterward) occurring when the patient was supine were successfully defibrillated by the ICD. Additional evidence supporting an orthostatic increase in DFT came from failure to defibrillate at 25 J during repeat DFT testing in an upright position using the original configuration when the DFT was estimated at 25 J or less at initial implant in a supine position, although the patient’s true DFT may have gradually increased over the years.6Martin D.T. John R. Venditti Jr, F.J. Increase in defibrillation threshold in non-thoracotomy implantable defibrillators using a biphasic waveform.Am J Cardiol. 1995; 76: 263-266Abstract Full Text PDF PubMed Scopus (41) Google Scholar, 7Mainigi S.K. Cooper J.M. Russo A.M. et al.Elevated defibrillation thresholds in patients undergoing biventricular defibrillator implantation: incidence and predictors.Heart Rhythm. 2006; 3: 1010-1016Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar We did not observe any other clear etiology (such as significant change in the lead position on x-ray or worsening heart failure and ejection fraction) to explain the increased DFT, other than the change in body position.The mechanism underlying the increased DFT in the upright position remains speculative.1Schauerte P. Diem B. Ziegert K. Franke A. Hanrath P. Stellbrink C. Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.J Cardiovasc Electrophysiol. 1998; 9: 696-702Crossref PubMed Scopus (5) Google Scholar The inferior and anterior displacement of the ICD can relative to the intravenous lead system after the patient assumes an upright position, especially in patients who have severe obesity such as the one presented here, may have contributed to the increased DFT. As shown in Figure 2, owing to the anterior shift in the can position, the shock vector between the can and RV coil may encompass less of the cardiac mass in the upright position compared to the supine one, thereby potentially increasing the DFT. Additionally, hemodynamic changes and increased sympathetic tone in an upright position may also influence the DFT.1Schauerte P. Diem B. Ziegert K. Franke A. Hanrath P. Stellbrink C. Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.J Cardiovasc Electrophysiol. 1998; 9: 696-702Crossref PubMed Scopus (5) Google Scholar, 8Schutzman J. Jaeger F. Maloney J. Fouad-Tarazi F. Head-up tilt and hemodynamic changes during orthostatic hypotension in patients with supine hypertension.J Am Coll Cardiol. 1994; 24: 454-461Abstract Full Text PDF PubMed Scopus (25) Google Scholar Having a dual venous coil system, especially with addition of an azygos coil, not only improves the shock vector but may also mitigate these position-related changes. In our own experience of six patients including this one, addition of an azygos shocking coil was successful in all and led to substantially reduced DFT in most cases (unpublished personal observation). There are other potential alternatives to reduce the DFT and increase the safety margin, such as addition of a superior vena cava coil or subcutaneous array, switching to a higher-energy device with 41 J output, or utilizing alternative devices that allow adjustable tilt.9Uyguanco E.R. Aaron Berger A. Budzikowski A.S. Gunsburg M. Kassotis J. Management of high defibrillation threshold.Expert Rev Cardiovasc Ther. 2008; 6: 1237-1248Crossref PubMed Scopus (7) Google Scholar, 10Epstein A.E. Ellenbogen K.A. Kirk K.A. Kay G.N. Dailey S.M. Plumb V.J. Clinical characteristics and outcome of patients with high defibrillation thresholds. A multicenter study.Circulation. 1992; 86: 1206-1216Crossref PubMed Scopus (163) Google Scholar However, a superior vena cava coil may not lead to as much reduction as the azygos coil,11Aoukar P.S. Poole J.E. Johnson G.W. Anderson J. Hellkamp A.S. Mark D.B. Lee K.L. Bardy G.H. No benefit of a dual coil over a single coil ICD lead: evidence from the Sudden Cardiac in Rhythm. Full Text Full Text PDF PubMed Scopus Google Scholar and the subcutaneous or other may not the of orthostatic changes and may not safety margin for this high-risk our this is the report of upright body posture a critical factor for failed defibrillation in an cardiac arrest. It has been long observed that a significant of patients with defibrillators and high of sudden cardiac owing to defibrillation energy or but orthostatic increase in the DFT may have also a as presented in this K. P. Clinical and survival in patients with the automatic implantable PubMed Scopus Google Scholar this patient had not been successfully the failure to defibrillate would have been to high DFT It is for patients to develop VF and still be able to maintain an upright failure to defibrillate can lead to prolonged VF and may increase the chance of subsequent defibrillation failure even patients and the supine patients who have risk for high DFT, such as severe dilated and orthostatic change can cause clinically significant increase in DFT and may lead to potential sudden cardiac owing to failure to defibrillate. This may be by the DFT testing which patients in a supine position. DFT testing in such patients may help defibrillation ICD system revision with addition of an azygos vein coil may help an orthostatic increase in DFT. IntroductionIt has previously been reported that patients with an implantable cardioverter-defibrillator (ICD) may have a slightly higher defibrillation threshold (DFT) in an upright position compared to a supine position.1Schauerte P. Diem B. Ziegert K. Franke A. Hanrath P. Stellbrink C. Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.J Cardiovasc Electrophysiol. 1998; 9: 696-702Crossref PubMed Scopus (5) Google Scholar However, the significance of this and the potential impact on clinical practice remains unclear. We report a case of defibrillation failure caused by an increase in DFT in the upright position, leading to prolonged, near-fatal cardiac arrest in a patient who had previous ICD implantation including successful DFT testing in a supine position. ICD system revision with addition of an azygos vein coil successfully corrected this condition, as demonstrated by orthostatic DFT testing.Case reportThe patient is a 47-year-old man with a prior history of nonischemic, dilated cardiomyopathy and ejection fraction 15%–20%. He underwent initial implantation of a single-chamber, single-coil ICD (Protecta VR D334VRG; Medtronic, Minneapolis, MN) for primary prevention in October 2012. The patient’s past medical history is also significant for morbid obesity, hypertension, type II diabetes, and renal insufficiency. Because of the patient’s body habitus, nonischemic cardiomyopathy, and young age, DFT testing was performed at the time of implant. After induction of ventricular fibrillation (VF) by T wave shock, a 15 J shock failed but a follow-up 25 J shock from the ICD successfully restored sinus rhythm. The patient’s device has a 35 J maximal output with a 10 J safety margin maintained. After the uneventful ICD implantation, he remained stable until recently, when he developed an episode of VF during sleep, with successful cardioversion by a single 35 J shock from the ICD. An evaluation including stress echocardiography was negative for ischemia. No additional coronary angiogram was performed owing to baseline renal insufficiency and because he already had two previous coronary angiograms within the last 5 years that showed no significant obstructive coronary artery disease. Conservative medical management was therefore recommended and the patient’s heart failure management was intensified with close follow-up by his cardiologist.Five months after the initial VF event and despite an apparent stable heart failure status, the patient developed sudden syncope without prodrome while sitting in a chair at home and was later found to be in cardiac arrest. According to the family, the patient was able to maintain an upright position in the chair. Subsequent ICD interrogation showed VF that was appropriately detected and six consecutive, maximal-energy shocks at 35 J (including a reversed polarity with the last shock) were delivered but failed to terminate the VF (Figure 1A–C). After exhaustion of device therapy, the patient remained in VF for approximately 6–7 minutes until paramedics arrived with an automated external defibrillator. The patient was immediately placed in the supine position and a single shock from the automated external defibrillator successfully converted the patient back into sinus rhythm (Figure 1D). After the patient was placed in the supine position, he subsequently developed 3 more VF episodes in the field, all of which were successfully detected and treated by the ICD (Figure 1E and F). The patient was initially transferred to a nearby hospital but was subsequently transferred to Borgess Medical Center for definitive management. Two days after the initial event, the patient did develop another episode of VF while supine in the hospital, which was again successfully detected and treated by the ICD with a 35 J shock. Following successful resuscitation including a cooling protocol, he was able to make a complete recovery with minimal residual neurologic deficit. Of note, chest x-ray performed in both the supine and upright positions demonstrated an orthostatic shift in the ICD can position relative to the heart, but no significant change in the lead position was found as compared to the one at initial implant (Figure of the apparent dependence of successful defibrillation on body position and the relatively high DFT during the initial implant, we elected to revise the patient’s ICD system with addition of an azygos vein coil and subsequently performed DFT testing in a supine as well as in an upright position.The patient was taken to the electrophysiology lab, where the left precordium was prepared and draped in the usual fashion. The axillary vein was accessed and the azygos vein was engaged using a 6 F Judkins-right-4 (JR4) diagnostic coronary catheter, as described by Cooper et al,2Cooper J.A. Latacha M.P. Soto G.E. Garmany R.G. Gleva M.J. Chen J. Faddis M.N. Smith T.W. The azygos defibrillator lead for elevated defibrillation thresholds: implant technique, lead stability, and patient series.Pacing Clin Electrophysiol. 2008; 31: 1405-1410Crossref PubMed Scopus (38) Google Scholar and a Storq wire (Johnson & Johnson Medical, NV, Diegem, Belgium). A 9 F long sheath was advanced over the JR4 and Storq wire, passing the initial torturous portion of the azygos vein. This allowed successful implantation of an azygos coil posterior to the heart (Figure 2E and F). At the end of the procedure, VF was induced and a 15 J shock from the device was able to successfully defibrillate the patient (not shown). The patient underwent further DFT testing the next morning in an upright position. The head of the bed was propped up about 70–80 degrees until the patient was in an upright posture similar to the one that he was in during the initial prolonged cardiac arrest. VF was again induced by T wave shock. Following successful detection of VF, an initial 25 J shock was purposefully delivered using the previous right ventricular (RV) coil–to–ICD can configuration to confirm that the failure to defibrillate was due to an increase in DFT in the upright position (Figure 3A). This indeed failed to terminate the VF. Immediately after that, with the patient still in VF in an upright position, a second 15 J manual shock using the new configuration (B>AX, RV coil to azygos coil/ICD can) incorporating the azygos coil was delivered within 10 seconds and successfully defibrillated the patient (Figure 3B). The patient tolerated the procedure well and was discharged home on amiodarone to suppress ventricular arrhythmias that may trigger further VF. At his post hospital follow-up one month after the event, the patient had completely recovered, with no residual neurologic deficit or recurrent VF episodes.Figure 3Defibrillation threshold testing when patient was in a sitting position with and without the azygos coil in the shock circuit. A: Using the initial right ventricular (RV) coil–to–ICD can configuration, a 25 J shock failed to defibrillate the patient. B: Immediately following the failure using the old configuration, a 15 J manual shock using the new RV coil–to–azygos vein/ICD can configuration successfully converted the patient to a paced rhythm.View Large Image Figure ViewerDownload