Total Failure to Sense Ventricular Fibrillation with Inappropriate Defibrillator Sensitivity...
3
Total Failure to Sense Ventricular Fibrillation with Inappropriate Defibrillator Sensitivity Adjustment DAVID LIN, SANJAY DIXIT, ANDREA M. RUSSO, and HENRY H. HSIA From the Electrophysiology Service, Cardiovascular Division, University of Pennsylvania Health System, Philadelphia, Pennsylvania LIN, D., ET AL.: Total Failure to Sense Ventricular Fibrillation with Inappropriate Defibrillator Sensitivity Adjustment. Automatic Sensitivity Control, unique to St. Jude defibrillators, allows for programmable sensitivity threshold and refractory periods. However, inappropriate programming can lead to marked undersensing and potentially lethal complications. We report a case of complete failure to sense ventricular fibrillation with inappropriate sensitivity adjustments. Detailed review of the parameters with induction of ventricular fibrillation must be performed to assure adequate safety.(PACE 2004; 27:1321–1323) defibrillation, Sensing, Ventricular arrhythmia Introduction As indications for cardioverter defibrillators (ICD) and the number of implantations continue to expand, the potential for device malfunction and complication may also increase. Oversensing can lead to inappropriate ICD shocks, while under- sensing can cause a delay or failure to deliver ther- apy, with potentially lethal consequences. Various sensing algorithms have been developed to assure adequate sensing and detection of low-amplitude, often oscillating, ventricular signals that occur during ventricular tachycardia (VT) and particu- larly during ventricular fibrillation (VF). 1–4 These algorithms use variable gains of the sensed signals, auto-adjusting sensitivity thresholds, or a combi- nation (4). Unlike pacemakers, programming op- tions of the sensing parameters in defibrillators are limited. Oversensing of T waves, diaphragmatic myopotentials, electromagnetic interference, or other artefacts can occur. 4–7 With the advent of biventricular pacing for cardiac resynchroniza- tion, double-sensing of the ventricular signals and far-field left atrial oversensing also have been re- ported. 8,9 The Automatic Sensitivity Control is a feature unique to the newer generation of St. Jude defibril- lators that allows programmable sensitivity thresh- old and refractory periods. This algorithm may be used to circumvent T wave oversensing or ventric- ular “double-sensing”. 6,9 However, extreme cau- tion must be exercised because significant under- sensing can occur. We report a case of complete failure to sense ventricular fibrillation with inap- propriate defibrillator sensitivity adjustments. Address for reprints: Henry H. Hsia, M. D., Section of Cardiac Electrophysiology, Division of Cardiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, 9 Founders, Philadelphia, PA 19104. Fax: (215) 662–2879; e-mail: [email protected] Received March 18, 2004; accepted April 8, 2004. Case Report A 69-year-old woman with coronary artery disease, left ventricular dysfunction, and nonsus- tained ventricular tachycardia was referred for an electrophysiological study. A dual chamber Photon DR, V-232 defibrillator (St. Jude, Inc., Syl- mar, CA USA) was implanted for inducible sus- tained monomorphic VT and sinus node dysfunc- tion. The lead system consisted of a Ventritex, model SP-02 ventricular defibrillator lead and a Pacesetter Tendril, model 1388T atrial lead. The sensed R wave at implantation was 6.9 mV with a ventricular pacing threshold of 0.75 V at 0.5 ms pulse width. The sensed P wave was 3.1 mV with a pacing threshold of 1.0 V at 0.5 ms pulse width. The atrial and ventricular lead impedances were normal. Postimplant chest X ray demonstrated good lead positions. The Automatic Sensitivity Control was set at the nominal values. Arrhyth- mia induction and the defibrillation threshold (DFT) testing were performed that demonstrated normal sensing and detection during ventricular fibrillation. The patient received multiple ICD shocks ap- proximately 8 weeks after implantation. Interroga- tion of the device demonstrated T wave oversens- ing with “double-counting” of QRS complexes and T waves during sinus rhythm that resulted in in- appropriate tachycardia detection and therapy de- livery. The Automatic Sensitivity Control was re- programmed by the referring cardiologist to rectify the situation. The patient underwent a routine follow-up ICD evaluation 3 months postimplant. Initial ICD interrogation demonstrated no recent arrhythmia episode detection or therapy delivery, and the lead impedance, pacing, and sensing thresholds remained excellent. Noninvasive stimulation and defibrillation threshold testing were performed. The ICD was programmed to a single VF zone with the detection criteria set at 182 beats/min (330 ms). Ventricular fibrillation was induced with PACE, Vol. 27 September 2004 1321
Transcript of Total Failure to Sense Ventricular Fibrillation with Inappropriate Defibrillator Sensitivity...
Total Failure to Sense Ventricular Fibrillation withInappropriate Defibrillator Sensitivity AdjustmentDAVID LIN, SANJAY DIXIT, ANDREA M. RUSSO, and HENRY H. HSIAFrom the Electrophysiology Service, Cardiovascular Division, University of Pennsylvania Health System,Philadelphia, Pennsylvania
LIN, D., ET AL.: Total Failure to Sense Ventricular Fibrillation with Inappropriate Defibrillator SensitivityAdjustment. Automatic Sensitivity Control, unique to St. Jude defibrillators, allows for programmablesensitivity threshold and refractory periods. However, inappropriate programming can lead to markedundersensing and potentially lethal complications. We report a case of complete failure to sense ventricularfibrillation with inappropriate sensitivity adjustments. Detailed review of the parameters with inductionof ventricular fibrillation must be performed to assure adequate safety.(PACE 2004; 27:1321–1323)
defibrillation, Sensing, Ventricular arrhythmia
IntroductionAs indications for cardioverter defibrillators
(ICD) and the number of implantations continueto expand, the potential for device malfunctionand complication may also increase. Oversensingcan lead to inappropriate ICD shocks, while under-sensing can cause a delay or failure to deliver ther-apy, with potentially lethal consequences. Varioussensing algorithms have been developed to assureadequate sensing and detection of low-amplitude,often oscillating, ventricular signals that occurduring ventricular tachycardia (VT) and particu-larly during ventricular fibrillation (VF).1–4 Thesealgorithms use variable gains of the sensed signals,auto-adjusting sensitivity thresholds, or a combi-nation (4). Unlike pacemakers, programming op-tions of the sensing parameters in defibrillators arelimited. Oversensing of T waves, diaphragmaticmyopotentials, electromagnetic interference, orother artefacts can occur.4–7 With the advent ofbiventricular pacing for cardiac resynchroniza-tion, double-sensing of the ventricular signals andfar-field left atrial oversensing also have been re-ported.8,9
The Automatic Sensitivity Control is a featureunique to the newer generation of St. Jude defibril-lators that allows programmable sensitivity thresh-old and refractory periods. This algorithm may beused to circumvent T wave oversensing or ventric-ular “double-sensing”.6,9 However, extreme cau-tion must be exercised because significant under-sensing can occur. We report a case of completefailure to sense ventricular fibrillation with inap-propriate defibrillator sensitivity adjustments.
Address for reprints: Henry H. Hsia, M. D., Section ofCardiac Electrophysiology, Division of Cardiology, Hospitalof the University of Pennsylvania, 3400 Spruce Street, 9Founders, Philadelphia, PA 19104. Fax: (215) 662–2879; e-mail:[email protected]
Received March 18, 2004; accepted April 8, 2004.
Case ReportA 69-year-old woman with coronary artery
disease, left ventricular dysfunction, and nonsus-tained ventricular tachycardia was referred foran electrophysiological study. A dual chamberPhoton DR, V-232 defibrillator (St. Jude, Inc., Syl-mar, CA USA) was implanted for inducible sus-tained monomorphic VT and sinus node dysfunc-tion. The lead system consisted of a Ventritex,model SP-02 ventricular defibrillator lead and aPacesetter Tendril, model 1388T atrial lead. Thesensed R wave at implantation was 6.9 mV witha ventricular pacing threshold of 0.75 V at 0.5 mspulse width. The sensed P wave was 3.1 mV witha pacing threshold of 1.0 V at 0.5 ms pulse width.The atrial and ventricular lead impedances werenormal. Postimplant chest X ray demonstratedgood lead positions. The Automatic SensitivityControl was set at the nominal values. Arrhyth-mia induction and the defibrillation threshold(DFT) testing were performed that demonstratednormal sensing and detection during ventricularfibrillation.
The patient received multiple ICD shocks ap-proximately 8 weeks after implantation. Interroga-tion of the device demonstrated T wave oversens-ing with “double-counting” of QRS complexes andT waves during sinus rhythm that resulted in in-appropriate tachycardia detection and therapy de-livery. The Automatic Sensitivity Control was re-programmed by the referring cardiologist to rectifythe situation.
The patient underwent a routine follow-upICD evaluation 3 months postimplant. Initial ICDinterrogation demonstrated no recent arrhythmiaepisode detection or therapy delivery, and thelead impedance, pacing, and sensing thresholdsremained excellent. Noninvasive stimulation anddefibrillation threshold testing were performed.The ICD was programmed to a single VF zonewith the detection criteria set at 182 beats/min(330 ms). Ventricular fibrillation was induced with
PACE, Vol. 27 September 2004 1321
LIN, ET AL.
Figure 1. The Automatic Sensitivity Control algorithm of the defibrillator. During sinus rhythm,the measured R wave amplitude ranges from 6 to 8 mV with a cycle length of 1000 ms. The nom-inal parameters consist of a sense refractory of 125 ms, a decay delay of 0 ms, and a postsensethreshold starting at 50% of the measured R wave amplitude. The gray line represents the sensi-tivity threshold. The sensitivity decays linearly at a slope of 3 mV/s until the next sensed eventor until it reaches the Maximum sensitivity of 0.3 mV.
a T wave shock; however, the defibrillator failed todetect the arrhythmia and no therapy was deliv-ered. Sinus rhythm was restored after a time lapseof 38 seconds with an external 360 J rescue shock.Interrogation of the ICD revealed total undersening
Figure 2. During ventricular fibrillation, the measured R wave amplitude ranges from 1 to 3mV with averaged cycle length of 233 ms. The Automatic Sensitivity Control was programmedto a sense refractory of 157 ms, a decay delay of 60 ms, and a postsense threshold starting at100% of the measured R wave amplitude. The sensitivity decay remains at a linear slope of 3mV/s with the maximum sensitivity of 0.3 mV. The gray line represents the sensitivity threshold.Reprogramming of the Automatic Sensitivity Control resulted in significant undersensing duringVF with an averaged sensed cycle length of only 525 ms. The defibrillator did not detect thisepisode of ventricular fibrillation.
of the induced VF episode without any tach-yarrhythmia detection during the VF event.Repeated evaluations demonstrated adequatesensing and pacing functions. The sensed R waveamplitude was 4 mV with a ventricular pacing
1322 September 2004 PACE, Vol. 27
UNDERSENSING WITH DEFIBRILLATOR SENSITIVITY ADJUSTMENT
threshold of 2.0 V at 0.5 ms pulse width. Thesensed P wave amplitude was 1.9 mV with a pacingthreshold of 0.5 V at 0.5 ms pulse width. A chestX ray revealed no evidence of lead dislodgment.
The Automatic Sensitivity Control was em-pirically reprogrammed to approximate the nom-inal values. Adequate sensing with VF detectionwas confirmed during repeated episodes of VF in-duction without signal dropout. The defibrillationthreshold was estimated at equal or less than 15 J.Furthermore, no evidence of T wave oversensingwas observed.
DiscussionPrevious studies on permanent ventricular
lead systems have demonstrated a substantialvariability in the sensed R wave amplitude dur-ing sinus rhythm, averaging up to 23.7% of themean R wave magnitude. This variability of sig-nal amplitude is further amplified by suddenchanges in heart rate during ventricular arrhyth-mia, increasing the range of R wave fluctua-tions up to 38.8% of the mean R wave ampli-tude.2,3 Reliable sensing of ventricular arrhythmiais thus critical for the effectiveness of defibrillatortherapy.
Different ICD manufacturers have differ-ent sensing algorithms for ventricular tachycar-dia/fibrillation detection.1,2,4,7 Appropriate ICDsensing function is dependent on prompt arrhyth-mia detection, while avoiding oversensing of in-tracardiac or extracardiac signals and artefactsthat can lead to inappropriate therapy. The Au-tomatic Sensitivity Control consists of a set ofprogrammable parameters that is available in thenew generation of St. Jude ICDs and provides agreater flexibility in sensing function programma-bility. It may allow the clinicians to circumventT wave, ventricular and atrial oversensing by ex-tending the sensing refractory periods and/or el-evating the sensitivity thresholds. However, sig-nificant arrhythmia undersensing can result with
inappropriate programming, as demonstrated inthis example.
The nominal parameters of the AutomaticSensitivity Control consists of a sense refractoryperiod of 125 ms, a decay delay of 0 ms, and apostsense threshold starting at 50% of the mea-sured ventricular signal amplitude (if the R waveis between 2 and 6 mV). The postsense thresholddecreases linearly at a slope of 3 mV/s until thenext sensed event or until it reaches the maximumsensitivity of 0.3 mV. If the sensed maximum Rwave amplitude is > 6 mV or < 2 mV, the post-sense threshold starts at 3 mV or 1 mV, respectively(Fig. 1).
In this patient, the sense refractory period wasincreased from 125 to 157 ms, the decay delaywas increased from 0 to 60 ms, and the postsensedthreshold was reprogrammed from starting at 50%to starting at 100% of the measured ventricularsignal amplitude (Fig. 2). This resulted in a 92ms delay in sensing due to the increase in thesense refractoriness. Furthermore, the sensitivitywas always determined by the largest sensed sig-nals (at 100% of the sensed amplitude). In combi-nation, these parameters caused a persistently ele-vated sensitivity with long refractoriness after eachsensed event. During an illustrated episode of ven-tricular arrhythmia with an averaged cycle lengthof 233 ms, significant undersensing was noted withthe “sensed” events occurring at only 525 ms cyclelength (Fig. 2).
Extreme caution must be exercised in adjust-ing any sensing parameters of a defibrillator. Onemust keep in mind the potential ramifications ofaltering the refractory period or sensitivity thresh-old, as well as the interactions of those parameters.Inappropriate programming can lead to markedundersensing and potentially lethal complica-tions. Detailed review of defibrillator parameterswith repeated induction of ventricular tachycar-dia/fibrillation must be performed to assure ade-quate sensing and effective defibrillator function.
References1. Panotopoulos P, Krum D, Axtell K, et al. Ventricular fibrillation
sensing and detection by implantable defibrillators: Is one betterthan the others? A prospective, comparative study. J CardiovascElectrophysiol 2001; 12:445–452.
2. Callans D, Hook B, Marchlinski F. Effect of rate and coupling in-terval on endocardial R wave amplitude variability in permanentventricular sensing lead systems. J Am Coll Cardiol 1993; 22:746–750.
3. Jung W, Manz M, Moosdorf R, et al. Changes in the amplitude ofendocardial electrograms following defibrillator discharge: Com-parison of two lead systems. PACE 1995; 18(Pt. 1):2163–2172.
4. Olson W. Tachyarrhythmia sensing and detection. In Singer I.Implantable Cardioverter-Defibrillator. Armonk, NY, Futura Pub-lishing Company, Inc., 1994, pp. 71–107.
5. Mann D, Otto L, Kelly P, et al. Effect of sensing system onthe incidence of myopotential oversensing during bradycardia
pacing in implantable cardioverter-defibrillators. Am J Cardiol2000; 85:1380–1382.
6. Schimpf R, Wolpert C, Bianchi F, et al. Congenital short QT syn-drome and implantable cardioverter defibrillator treatment: Inher-ent risk for inappropriate shock delivery. J Cardiovasc Electrophys-iol 2003; 14:1273–1277.
7. Schulte B, Sperzel J, Schwarz T, et al. Detection of ventricularfibrillation in implantable defibrillators with automatic gain con-trol amplifiers: Effects of programming sensitivity. Europace 20002:160–162.
8. Garcia-Moran, E, Mont L, Brugada J. Inappropriate tachycardia de-tection by a biventricular implantable cardioverter defibrillator.PACE 2002; 25:123–124.
9. Lipchenca I, Garrigue S, Gilkson M, et al. Inhibition of biventricularpacemakers by oversensing of far-field atrial depolarization. PACE2002; 25:365–367.
PACE, Vol. 27 September 2004 1323
