Tachycardia Detection Interval Research Articles

Efficacy and Limitations of Tachycardia Detection Interval Guided Reprogramming for Reduction of Inappropriate Shock in Implantable Cardioverter-Defibrillator Patients.

The avoidance of inappropriate shock therapy is an important clinical issue in implantable cardioverter-defibrillator (ICD) patients. We retrospectively analyzed therapeutic events in ICD patients, and the effect of tachycardia detection interval (TDI) and tachycardia cycle length (TCL) guided reprograming on the reduction of inappropriate ICD therapy. The clinical determinants of after reprogramming were also evaluated.A total of 254 consecutive ICD patients were included in the study, and the incidence of antitachycardia therapy was evaluated during the follow-up period of 27.3 ± 18.7 months. When inappropriate antitachycardia therapy appeared, TDI was reprogrammed not to exceed the detected TCL and the patients continued to be followed-up. Various clinical parameters were compared between patients with and without inappropriate ICD therapy. During the initial follow-up period of 18.6 ± 15.6 months, ICD therapy occurred in 127/254 patients (50%) including inappropriate antitachycardia pacing (ATP) (12.9%) and shock (44.35%). Determinants of initial inappropriate therapy were dilated cardiomyopathy (DCM), history of therapeutic hypothermia, and QRS duration. Of the 61 patients with inappropriate therapy, 24 received TCL guided reprogramming. During the additional observation period of 17.0 ± 16.8 months, inappropriate therapy recurred in 5/24 patients (2 ATP, 3 shocks). The determinant of these inappropriate therapy events after reprogramming was the presence of supraventricular tachycardia.By applying simple TCL and TDI guided reprogramming, inappropriate therapy was reduced by 79%. The determinant of inappropriate therapy after reprogramming was the presence of supraventricular tachycardia.

Alternating atrial pacing cycle length during ventricular tachycardia: What is the mechanism?

Case summary A 62-year-old man with a background of ischemic cardiomyopathy and sick sinus syndrome underwent implantation of a cardiac resynchronization therapy defibrillator (CRTD) device (Medtronic Concerto, Minneapolis, MN). Table 1 lists the basic pacing programming of the device. At routine follow-up, a ventricular event was detected that was terminated successfully following 3 antitachycardia pacing therapies. The dot-plot relating to the ventricular event initially demonstrated some variation in the cycle length of the ventricular tachycardia (VT), resulting in V-V intervals drifting above and below the ventricular tachycardia detection interval (VTDI) set at 400 ms (Figure 1). Simultaneous critically short coupled ventricular tracked events during this period of VT were seen in association with those V-V intervals that were just above the VTDI. Careful analysis of the corresponding electrograms also revealed an interesting pattern of atrial pacing with alternating cycle lengths of 680 and 490 ms occurring concurrently in the presence of VT (Figure 2). Further inspection of the episode revealed that once acceleration of the VT occurred with V-V intervals falling consistently below the VTDI, cessation of atrial pacing was seen, followed by the successful detection and subsequent termination of the VT episode with antitachycardia pacing. The questions that arise are as follows. (1) Which algorithm was responsible for the simultaneous critically short coupled ventricular tracked events observed following initiation of VT? (2) Why, despite ongoing VT,

Wide complex tachycardia in a patient with a dual-chamber defibrillator: What is the rhythm? A tale of timing cycles

Case summary A 72-year-old patient with history of ischemic cardiomyopathy and dual-chamber implantable cardioverter-defibrillator (ICD) was evaluated for tachycardia. The patient had undergone surgery for implantation of a HeartMate II left ventricular assist device 1 week prior to the onset of tachycardia. Postprocedure, the patient was persistently in a wide complex tachycardia except during brief episodes, where his heart rate was 80 beats/ min, and the 12-lead electrocardiogram (ECG) of which is shown in Figure 1A. The faster rhythm was at 125 beats/min (Figure 1B) and below the tachycardia detection interval of the ICD. The telemetry strips corresponding to the 2 rhythms are shown in Figure 2. Can a definite diagnosis of his rhythm be obtained from the ECG and telemetry recordings, and what programmed pacing mode of the dual-chamber ICD can explain the findings?

Inappropriate Discharges by Fourth Generation Implantable Cardioverter Defibrillators in Patients With Ventricular Arrhythmias.

The study prospectively investigated the incidence, cause and efficient management of inappropriate discharge by the fourth generation implantable cardioverter-defibrillator (ICD) system in 45 patients (mean age, 57+/-16 years). During the follow-up period of 27+/-17 months, 18 patients (40%) experienced one or more inappropriate therapies: sinus and supraventricular tachycardia (15 patients) and T wave oversensing (3 patients). In the 15 patients, re-programming of the tachycardia detection interval and/or additional treatment with beta-blocking agents were effective. In the 3 patients with T wave oversensing, the arrythmia was associated with an increase in T wave amplitude, change in T wave morphology and decreased R wave amplitude, and re-programming of the sensitivity of the local electrogram or changing the number of intervals to detect ventricular tachycardia decreased the number of inappropriate discharges in all 3 patients. In conclusion, inappropriate therapies are common problems in patients treated with the fourth generation ICD system, but most of them can be resolved using the dual-chamber ICD system. However, in patients with T-wave oversensing, it is difficult to avoid inappropriate discharge completely, even if the dual-chamber ICD system is implanted.

Ventricular tachycardias above the initially programmed tachycardia detection interval in patients with implantable cardioverter-defibrillators: Incidence, prediction and significance

OBJECTIVESThis retrospective study was performed to provide data on ventricular tachycardias (VT) with a cycle length longer than the initially programmed tachycardia detection interval (TDI) in patients with implantable cardioverter defibrillators (ICDs).BACKGROUNDIt has been clinical practice to program a safety margin of 30 to 60 ms between the slowest spontaneous or inducible VT and the TDI.METHODSBaseline characteristics of 659 consecutive patients with ICDs were prospectively; follow-up information was retrospectively collected.RESULTSDuring a mean follow-up of 31 ± 23 months, 377 patients (57.2%) had at least one recurrent VT or ventricular fibrillation; 47 patients (7.1%) suffered 61 VTs above the TDI. The risk of a VT above the TDI ranged between 2.7% and 3.5% per year during the first four years after ICD implantation. The difference between the cycle length of the slowest VT before ICD implantation, spontaneous or induced, and the first VT above TDI was 108 ± 58 ms. Fifty-four VTs (88.5%) above the TDI were associated with significant clinical symptoms (angina or palpitation 63.9%, heart failure 6.6% and syncope 8.2%). Six patients (9.8%) had to be resuscitated. Kaplan-Meyer analysis identified New York Heart Association class II or III (p = 0.021), ejection fraction < 0.40 (p = 0.027), spontaneous (p < 0.001) or inducible (p < 0.001) monomorphic VTs and the use of class III antiarrhythmic drugs (amiodarone, p < 0.001; sotalol, p = 0.004) as risk predictors of VTs above the TDI. The risk of recurrent VTs above TDI was 11.8%, 12.5% and 26.6% during the first, second and third year after first VT above TDI, respectively.CONCLUSIONSThe risk of VTs above the TDI is significantly increased in some patients, and many VTs above TDI cause significant clinical symptoms. A larger safety margin between spontaneous or inducible VTs and the TDI seems to be necessary in selected patients. This is in conflict with an increased risk of inadequate episodes and demands highly specific and sensitive detection algorithms in these patients.

Performance of basic ventricular tachycardia detection algorithms in implantable cardioverter defibrillators: implications for device programming.

Around 20% of patients with third generation implantable cardioverter defibrillators receive inappropriate therapy, usually triggered by atrial fibrillation. This is because the criteria used for ventricular tachycardia detection by current implantable cardioverter defibrillators are based on the analysis of a sequence of RR intervals and may be inappropriately satisfied by supraventricular tachyarrhythmias. Algorithms for ventricular tachycardia detection were challenged against the full RR interval sequences from 482 spontaneous episodes of atrial fibrillation and 260 spontaneous episodes of ventricular tachycardia to determine their ability to discriminate between the arrhythmias. The sensitivities and specificities of the algorithms were calculated over a wide range of programmable parameters. For a given window length and detection interval, the most stringent algorithms, that required all beats to be classified as "fast", were more specific than those allowing a proportion of "normal" intervals, even after adjustment for differing sensitivity. These differences were less marked for faster tachycardias. Specificity increased with the detection window length to a limit of approximately 18 beats. We conclude that ventricular tachycardia is detected with the highest specificity if all beats in an analyzed sequence are required to be "fast," even after lengthening of the tachycardia detection interval to maintain sensitivity. Further improvement in algorithm performance may require the incorporation of criteria such as tachycardia onset and stability.

RR interval variability in irregular monomorphic ventricular tachycardia and atrial fibrillation.

Algorithms to reject irregular tachyarrhythmias are available in implantable cardioverter-defibrillator devices to discriminate ventricular tachycardia (VT) from atrial fibrillation (AF). The hazard of underdetection of irregular monomorphic VTs using these algorithms has not yet been fully evaluated. The purpose of this study was to determine the ability of a commonly used stability algorithm to reject AF and to correctly detect VT with a high RR interval variability. The electrophysiological studies from 232 patients with induced monomorphic VT (cycle length > 250 ms) and 21 with AF were reviewed. A preliminary analysis was performed to classify the VT episodes in irregular (successive RR differences > 20 ms after 4 seconds from onset) or regular (otherwise). Three study groups were defined: group 1 (27 patients with irregular VT), group 2 (22 randomly selected patients with regular VT), and group 3 (21 patients with AF). A computer program analyzed the first 50 RR intervals of the induced VT (AF), resetting a VT counter if the interval was greater than a tachycardia detection interval (TDI) or if its absolute difference with the preceding three beats exceeded a programmed stability value (STAB). The VT was detected when the VT counter reached a preset number of intervals (NIDs). Different combinations of TDI, STAB, and NID were analyzed. All VTs in group 2 were correctly detected. In contrast, up to 10 VTs from group 1 were not detected when high NIDs and low STAB parameters were programmed. With usual values (10 to 16 beats and 50 to 60 ms, respectively), only 1 to 2 VTs remained undetected, but 20% to 50% had a detection delay > 8 seconds. Undetected VTs were significantly slower than early detected VTs for most STAB and NID combinations. With usual stability and NID values, 10% to 20% of episodes of AF were inappropriately detected. Changes in TDI had a small impact on sensitivity and specificity when currently used values for stability were programmed. Animplantable cardioverter-defibrillator tachycardia detection algorithm with a stability criterion of 50 to 60 ms and 12 to 14 RR intervals is able to detect over 90% of monomorphic irregular VTs. Nevertheless, significant VT detection delays may arise, and inappropriate detection of AF cannot be totally prevented.

Long-term multicenter experience with a second-generation implantable pacemaker-defibrillator in patients with malignant ventricular tachyarrhythmias

A second-generation implantable pacemaker-cardioverter-defibrillator was evaluated in 200 patients with sustained ventricular tachycardia, ventricular fibrillation or prior cardiac arrest. The device permits demand ventricular pacing for bradyarrhythmias and for long QT interval or tachycardia suppression, uses programmable (3 to 30 J) energy shocks for conversion of ventricular tachycardia and ventricular fibrillation and is used with conventional pacing and defibrillation leads. Ventricular tachycardia/fibrillation recognition is based on the ventricular electrogram rate and requires reconfirmation before shock delivery. Two hundred patients (mean age 62 years, mean left ventricular ejection fraction 36%) were enrolled and followed up for 0 to 23 months (mean 12). Epicardial lead system implantation was performed with use of an anterolateral thoracotomy (38%), median sternotomy (26%) and subxiphoid (20%) or subcostal (16%) approach. Perioperative mortality rate was 5.5% (all nonarrhythmic deaths). Implant defibrillation threshold ranged from 3 to 30 J (mean 15), with initial programmed shock energy ranging from 3 to 30 J (mean 22). Ventricular tachycardia/fibrillation sensing threshold ranged from 0.7 to 1.8 mV (median 1) and the tachycardia detection interval from 288 to 416 ms (median 320). Reprogramming of implant variables was necessary for reliable electrographic sensing (54 patients), programmed shock therapy (61 patients) and tachycardia detection rate (63 patients). Device activation for potential shock delivery occurred in 111 patients (55.5%) with actual shock delivery after ventricular tachycardia/fibrillation reconfirmation in 66 patients (33%). During follow-up study, there was a 1% arrhythmia mortality rate, 6.5% cardiac mortality rate and 10.5% total mortality rate. This study demonstrates that the programmable implantable pacemaker-cardioverter-defibrillator is effective in preventing arrhythmic death, yet reduces patient exposure to repeated shock therapy. Reprogramming is usually necessary during follow-up for optimal function.

Percutaneous double balloon valvuloplasty for severe tricuspid stenosis

pacemaker function was normal, and no ventricular tachycardia was observed on Holter monitoring. A multiprogrammable telemetric implantable automatic defibrillator with a multiprogrammable VVI bradycardia support system (Telectronics Guardian, model 4201, Telectronics, Inc., Englewood, Colo.) was implanted and the original VVI pacemaker was explanted. The defibrillation threshold was 18 joules. The device was programmed with an initial energy of 28 joules (650 V, 8 msec) (safety margin = 10 joules). The tachycardia detection interval was 320 msec (Fig. 2) and after defibrillation, the VVI bradycardia support system could be observed (Fig. 3). One month after implant, ventricular fibrillation was induced and automatic defibrillation was successful. The patient is doing well 4 months after implant. No discharge has been registered and the bradycardia support of the defibrillator is working as a VVI pacemaker. This is the first report of an automatic implantable defibrillator in Chagas disease. Because bifascicular or total atrioventricular block are present in almost 50% of chagasic patients who present with sustained ventricular arrhythmias,” automatic defibrillators with pacemaker function will probably be very useful in selected cases of chronic Chagasic myocarditis.