Rhythm Discrimination Research Articles

Prospective comparison of discrimination algorithms to prevent inappropriate ICD therapy: Primary results of the Rhythm ID Going Head to Head Trial

Inappropriate therapy for supraventricular arrhythmias remains a significant source of morbidity in implantable cardioverter-defibrillator (ICD) recipients. The Rhythm ID Goes Head to Head Trial (RIGHT) was designed to compare rhythm discrimination and inappropriate therapies among patients with ICDs from 2 manufacturers. Patients with standard ICD indications were randomized to receive a Guidant VITALITY 2 with Rhythm ID or selective Medtronic pulse generators using the Enhanced PR Logic or Wavelet discrimination algorithms. A single- or dual-chamber device was implanted based on clinical indications and programmed in 2 detection zones with detection enhancements enabled for rates between 150 and 200 bpm. Algorithm performance was compared between randomization groups, stratified by single or dual chamber, for the primary end point of first inappropriate therapy (shock or antitachycardia pacing) for supraventricular arrhythmias. There were 1962 patients enrolled and followed for 18.3 ± 9.2 months, with no difference in all-cause mortality between groups. There were 3973 treated episodes where electrograms were available and adjudicated. The primary end point of inappropriate therapy occurred in 246 of 985 VITALITY 2 patients vs 187 of 977 specific Medtronic ICD patients (hazard ratio = 1.34; confidence interval = 1.11-1.62; P = .003). Differences in inappropriate therapy were confined to single-chamber ICDs. Inappropriate shocks were more frequent in VITALITY 2 ICDs (hazard ratio = 1.63; confidence interval = 1.29-2.06; P < .001), with most therapies and performance differences occurring at slower rhythms (rates < 175 bpm). Rhythm discrimination performed better in the specific Medtronic than in VITALITY 2 ICDs evaluated, particularly for single-chamber devices. Inappropriate therapies, and differences in performance, may be reduced with the use of rate cutoff above 175 bpm.

Automated rhythmic discrimination of dysarthria types

This study examines whether features of rhythm, extracted via an automated program, can match the success of hand-extracted metrics in discriminating among control and different types of dysarthric speech. Previously, Liss etal. [J. Speech, Language, and Hearing Res., 52(5), 1334–1352 (2009)] demonstrated that rhythm metrics could successfully separate individuals with perceptually distinct rhythm patterns, with the majority of classification functions more than 80% successful in classifying dysarthria type. However, the hand extracted rhythm measurements are labor intensive and require expertise in acoustic analysis to achieve valid and reliable measures. In this study, digitized speech was automatically segmented into vocalic and voiceless intervals using an autocorrelation-based algorithm, and, from these intervals, rhythm metrics were computed. Discriminant function analyses were performed and revealed the majority of functions were more than 90% successful in classification, matching, or exceeding the success of the hand- extracted measurements. Removing subjectivity, automating this procedure, and verifying its comparability with traditional methods improve the viability of rhythm metrics as a clinical tool in speech therapy intervention. Additionally, the ease of manipulation of the automated program will allow for development of metrics that capture severity and individual speaker differences that will inform models of speech perception.

Can we predict, prevent, and minimize defibrillator shocks? Lessons learned from “remote monitoring”

s I o f 9 f Beyond their principal role of successfully detecting and treating ventricular tachycardia (VT) and ventricular fibrillation (VF) with overdrive antitachycardia pacing and defibrillation shocks, modern implantable cardioverter-defibrillators (ICDs) are capable of providing sophisticated pacing and resynchronization therapy. They store enormous amounts of technical and patient-related data, such as arrhythmia burden and heart failure status. Device manufacturers recently introduced “remote monitoring” technology, which allows home transmitters to interrogate devices and to download and transmit collected and stored data via the Internet to a protected network. Remote monitoring not only has rapidly shifted the paradigm in device follow-up but has heightened interest in exploring the wealth of available information to better understand device functionality and disease substrates. Irrespective of the indications for ICD placement, given the associated risk factors and comorbidities, the majority of recipients also would be prone, if they have not already experienced, to develop atrial fibrillation (AF). The presence of AF, with its 5% to 30% incidence in the ICD population, is not merely a “nuisance” because it has many detrimental effects. Paroxysmal, persistent, and permanent AF have hazard ratios (HRs) (95% confidence interval] of 1.3 (0.7–2.5), 1.2 (0.6–2.2), and 1.7 (1.0–2.7), respectively, for mortality and 1.2 (0.6–2.2), 1.1 (0.5–2.4), and 2.4 (1.5–4.0), respectively, for appropriate ICD shocks. A ewly detected AF within the first 3 months of ICD placeent carries a significant risk for death with HR of 2.86 1.02–8.05). In patients with left ventricular dysfunction, persistent AF has been shown to cause appropriate ICD shocks and deterioration of heart failure. Furthermore, AF ay be proarrhythmic. In the Jewel AF trial, 8.6% of all T/VF episodes were found to have AF as a preceding or oncomitant rhythm. Interestingly, for consecutive episodes of VT/VF, time to next episode of VT/VF was longer when AF terminated than when it persisted.

From TEMPO+ to OPUS 2: What can music tests tell us about processor upgrades?

Tests for quantifying the music perception abilities of cochlear implant users are currently being developed and trialled at the South of England Cochlear Implant Centre. In addition to measures of speech perception, tests of rhythm, and pitch have been administered to MED-EL C40+ implant users before and after upgrading from the TEMPO+ processor with continuous interleaved sampling strategy to the OPUS 2 processor with fine structure processing strategy, with the aims of comparing device performance and evaluating the potential of music perception tests for informing processor upgrades and tuning. Eight experienced adult C40+ implant recipients performed tests of rhythm and pitch discrimination using the TEMPO+ processor and, after a minimum of 6 weeks acclimatization, using the OPUS 2 processor. Stimuli included piano and sine tones in two note ranges for the pitch tasks, and drum beats for the rhythm task. Rhythm, pitch, and speech perception scores were comparable for both processors. An effect of note range was observed (z = −2.52, p = 0.008 (two-tailed), r = −0.63), which indicated that the higher range of notes used for the pitch tasks was easier for participants than the lower range. Measures of pitch discrimination in different frequency ranges further informed changes made to one participant's map, resulting in improved pitch discrimination and speech perception scores. The outcomes of this study demonstrate that music perception tests can provide important additional measures for tuning cochlear implant parameters and assessing the impact of changes to device type and processing strategy.

Congenital amusia in childhood: A case study

Here we describe the first documented case of congenital amusia in childhood. AS is a 10-year-old girl who was referred to us by her choir director for persisting difficulties in singing. We tested her with the child version of the Montreal Battery for the Evaluation of Amusia (MBEA) which confirmed AS’s severe problems with melodic and rhythmic discrimination and memory for melodies. The disorder appears to be limited to music since her audiometry as well as her intellectual and language skills are normal. Furthermore, the musical disorder is associated to a severe deficit in detecting small pitch changes. The electrical brain responses point to an anomaly in the early stages of auditory processing, such as reflected by an abnormal mismatch negativity (MMN) response to small pitch changes. In singing, AS makes more pitch than time errors. Thus, despite frequent and regular musical practice, AS’s profile is similar to the adult form of congenital amusia.

Apparent motion enhances visual rhythm discrimination in infancy

Many studies have demonstrated that infants exhibit robust auditory rhythm discrimination, but research on infants' perception of visual rhythm is limited. In particular, the role of motion in infants' perception of visual rhythm remains unknown, despite the prevalence of motion cues in naturally occurring visual rhythms. In the present study, we examined the role of motion in 7-month-old infants' discrimination of visual rhythms by comparing experimental conditions with apparent motion in the stimuli versus stationary rhythmic stimuli. Infants succeeded at discriminating visual rhythms only when the visual rhythm occurred with an apparent motion component. These results support the view that motion plays a role in infants' perception of visual temporal information, consistent with the manner in which natural rhythms appear in the visual world.

Comparison of a Novel, Single-Lead Atrial Sensing System With a Dual-Chamber Implantable Cardioverter-Defibrillator System in Patients Without Antibradycardia Pacing Indications

Background— Supraventricular tachyarrhythmias are the main cause for inappropriate therapy by implantable cardioverter-defibrillators (ICDs). For better rhythm discrimination, an atrial electrogram is helpful and usually obtained from an additional atrial lead, even in the absence of sinus node or atrioventricular nodal disease. An A+-ICD system with integrated atrial sensing rings mounted 15 to 18 cm from the tip of an ICD lead may obviate the need to implant a separate atrial lead. The aim of the study was to compare the novel A+-ICD and a conventional dual-chamber (DR)-ICD. Methods and Results— Two hundred forty-nine patients with standard ICD indications but no requirement for antibradycardia pacing were randomized to receive an A+-ICD (n=124) or a DR-ICD (n=125). Implantation details, need for ICD system revision, long-term sensing, documented arrhythmia episodes, and the respective rhythm discrimination during follow-up were analyzed. The implantation time was significantly shorter in the A+-ICD group (67±30 vs 79±30 minutes, P =0.003). Mean P-wave amplitudes were 3.5±0.8 mV (A+-ICD) and 3.2±0.6 mV (DR-ICD) and remained stable during the follow-up period of 12 months. Surgical revision was necessary in 13 patients in the DR-ICD and 10 in the A+-ICD group. All 593 ventricular tachyarrhythmia episodes were correctly discriminated. Sensitivity and specificity of supraventricular tachyarrhythmia discrimination were not different between the study groups. Conclusions— The novel A+-ICD system can be implanted faster and is equivalent to a standard DR-ICD with regard to the detection of ventricular tachyarrhythmias and supraventricular tachyarrhythmias. It represents a useful alternative to obtain atrial sensing. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00324662.

The MuSIC perception test: A novel battery for testing music perception of cochlear implant users

This study was undertaken to evaluate the musical sounds in cochlear implants (MuSIC) perception test, created to assess the music-listening abilities of cochlear implant (CI) users. Thirty-one unilateral MED-EL COMBI 40+/PULSARCI100 users and a control group of 67 adults with normal hearing (NH) participated. The MuSIC test comprises six objective and two subjective modules employing approximately 2800 musical files recorded from non-synthesized instruments. A subset was used for comparing CI and NH participants’ results. CI and NH participants performed significantly differently on: pitch discrimination, melody discrimination, chord discrimination, instrument detection, and instrument identification. No significant difference in performance was seen on the subtests of rhythm discrimination or dissonance rating and emotion rating. The MuSIC test was found to be a valuable tool for assessing music perception in CI users and NH participants, whether investigating one aspect of music perception in depth or conducting a broad survey of music perception.

Temporal fine structure for sequential segregation.

Pitch based sequential segregation is reputed to benefit from spectral cues and temporal envelope cues. However, some previous results with hearing impaired listeners raised the possibility that other cues could promote segregation. These other cues could be responsible for the high inter‐subject variability across hearing impaired listeners in streaming experiments. Temporal fine structure cues appeared then to be a valuable candidate. The current study is dedicated to assess the potential benefit from temporal fine structure cues for sequential segregation. Unresolved complex tones (A) and unresolved complex tones with the same F0 in which all components were shifted upward by the same number of Hertz (B) were presented in ABA‐ABA‐ sequences. Using these stimuli, a rhythm discrimination task was used to estimate the amount of primitive segregation. Cochlear models will be applied first to the stimuli to establish the respective amount of spectral, temporal envelope and temporal fine structure cues. The results from the discrimination task will then be discussed at the light of the outputs of the models.

Improving contemporary algorithms for implantable cardioverter-defibrillator function

Implantable cardioverter-defibrillators (ICDs) have been shown in various clinical trials to prevent mortality from sudden cardiac death due to unstable rhythms or ventricular fibrillation. Modern ICDs use sophisticated algorithms to not only deliver therapy on the detection of a malignant rhythm but also reduce the incidence of inappropriate shocks through rhythm discrimination. Current algorithms for detection of malignant rhythms use sophisticated techniques such as real-time processing and analysis of electrograms from a transvenous lead system. The Rhythm ID feature in Boston Scientific ICDs is an example of one such algorithm used for rhythm discrimination. Rhythm ID uses the vector timing and correlation algorithm, which incorporates both timing as well as morphology information for supraventricular tachycardia discrimination. Clinical trials demonstrated high sensitivity and specificity of this feature in discriminating between ventricular tachycardia and supraventricular tachycardia (results published previously). On detection of the unknown rhythm (when the ventricular tachycardia rate detection criteria is met), the vector timing and correlation algorithm compares the unknown rhythm beat-by-beat to a stored template of normal sinus rhythm. The feature correlation coefficient computed over more than 8 points in the time-aligned signals is used for the comparison. The specific discrimination procedure of Rhythm ID depends on the mode (VR or DR) and on whether the test rhythm is an initial detected rhythm or a postshock rhythm. The normal sinus rhythm template against which the suspected rhythm is compared can be periodically updated. This article will cover some of the key aspects of the Rhythm ID feature's decision-making process and the algorithm for template update. The results of previously published clinical studies involving the algorithm's performance also will be reviewed.

Implantable and surface electrocardiography: complementary technologies

Combining information obtained from the surface electrocardiogram and implantable devices represents an emerging trend in electrocardiology. Important potential applications include ischemia detection and localization, continuous monitoring of cardiac cycle parameters, and telemedicine. This article presents an overview of these emerging applications, focusing on our recent studies that combine the electrograms obtained from body surface and implantable devices to reconstruct a full 12-lead electrocardiogram from the implanted device. These technologies have broad application for detection of ischemia, improvement of the accuracy of ischemic localization, and rhythm discrimination.

Crossmodal congruency effects based on stimulus identity

We investigated whether the crossmodal congruency effect, normally observed in spatial compatibility tasks, would also affect performance on a task based on discriminating stimulus identity (i.e., a non-spatial dimension). Two rhythms were presented to participants' eyes, ears, and/or hands in a 4-alternative rhythm discrimination task. Stimulus identity and stimulus modality were varied orthogonally. When the target and distractor rhythms were presented in different sensory modalities, significant crossmodal congruency effects were observed in all conditions (i.e., performance on the incongruent distractor trials was significantly more error-prone than on the congruent distractor trials). In contrast to the results of previous studies, these crossmodal distractor effects were neither based on the spatial compatibility of the stimuli nor on an abstract semantic matching of stimulus identity, but instead on the identity of the target rhythm. Intriguingly, the magnitude of the crossmodal congruency effects differed as a function of the target modality, but were unaffected by the modality of the distractor.

Combined Atrial and Ventricular Antitachycardia Pacing as a Novel Method of Rhythm Discrimination

Inappropriate and unnecessary implantable cardioverter-defibrillator shocks continue to be highly prevalent. We prospectively evaluated a new algorithm for discriminating supraventricular (SVT) and ventricular (VT) tachycardias with 1:1 atrioventricular association that is based on the response of the arrhythmia to simultaneous or convergent dual-chamber antitachycardia pacing. Patients undergoing dual-chamber cardioverter-defibrillator implantation were randomized to the simultaneous atrioventricular and convergent atrioventricular arms with crossover at 3 months. Sixty-three patients had 1407 1:1 antitachycardia pacing sequences suitable for analysis (1381 1:1 SVT episodes in 32 patients and 26 1:1 VT episodes in 6 patients). Antitachycardia pacing terminated 66 of 1381 SVT (5%; generalized estimating equations adjusted, 23.8%) and 20 of 26 VT (77%; generalized estimating equation adjusted, 68.6%) episodes. After the exclusion of sinus tachycardia, the new software terminated 40 of 57 (70%; generalized estimating equation adjusted, 70.2%) SVT episodes. The new algorithm terminated or correctly classified 1379 of 1381 SVT sequences for an overall specificity of 99.9% (generalized estimating equation adjusted, 99.8%) and 23 of 26 VT for an overall sensitivity of 88.5% (generalized estimating equation adjusted, 82.1%). There were no statistically significant differences between the simultaneous and the convergent atrioventricular antitachycardia pacing sequences in their ability to confirm VT or reject SVT. No significant proarrhythmias were noted. We describe here a new pacing algorithm in dual-chamber defibrillators that can terminate arrhythmias or discriminate between 1:1 SVT and VT if the arrhythmia persists. Testing this new algorithm in larger patient populations is warranted. CLINICAL TRIAL REGISTRATION INFORMATION- URL: http://ftp.resource.org/gpo.gov/register/2007/2007_15297.pdf. IDE No. G060230.

Detection algorithms for intracardiac electrograms in implantable cardioverter defibrillators

Since their first clinical application by Mirowski in the 1980s, implantable eardioverter defibrillators(ICDs) has become an important choice of therapy for decreasing mortality in patients with high risk of life-threatening arrhythmias. However, the misclassifieation of the tachycardias is still a major problem among current ICDs. At present, many different rhythm discrimination algorithms, such as rate threshold, sudden onset, rate stability, morphological analysis, time-frequency analysis, neural networks, and covarianee-based algorithm,have been proposed to distinguish taehycardias. The cardiac rhythm detection algorithms and correlation waveform analysis are commonly used in ICDs as the detection methods, which are also the basis of other detection methods. With the development of the technology, some new algorithms, including artificial neural network, are expected to be applied in ICDs in the future. Key words: Implantable eardioverter defibrillators; Intraeardiac eleetrograms; Detection algorithms

Perception of strong-meter and weak-meter rhythms in children with spina bifida meningomyelocele.

Neurodevelopmental disorders such as spina bifida meningomyelocele (SBM) are often associated with dysrhythmic movement. We studied rhythm discrimination in 21 children with SBM and in 21 age-matched controls, with the research question being whether both groups showed a strong-meter advantage whereby rhythm discrimination is better for rhythms with a strong-meter, in which onsets of longer intervals occurred on the beat, than those with a weak-meter, in which onsets of longer intervals occurred off the beat. Compared to controls, the SBM group was less able to discriminate strong-meter rhythms, although they performed comparably in discriminating weak-meter rhythms. The attenuated strong-meter advantage in children with SBM shows that their rhythm deficits occur at the level of both perception and action, and may represent a central processing disruption of the brain mechanisms for rhythm.

Sequential stream segregation using temporal periodicity cues in cochlear implant recipients

Sequential stream segregation involves the ability of a listener to perceptually segregate two rapidly alternating sounds into different perceptual streams. By studying auditory streaming in cochlear implants (CIs), one can obtain a better understanding of the cues that CI recipients can use to segregate different sound sources, which may have relevance to such everyday activities as the understanding of speech in background noise. This study focuses on the ability of CI users to use temporal periodicity cues to perform auditory stream segregation. A rhythmic discrimination task involving sequences of alternating amplitude-modulated (AM) noises is used. The results suggest that most CI users can stream AM noise bursts at relatively low modulation frequencies (near 80 Hz AM), but that this ability diminishes at higher modulation frequencies. Additionally, the ability of CI users to perform streaming using temporal periodicity cues appears to be comparable to that of normal-hearing listeners. These results imply that CI subjects may in certain contexts (i.e., when the talker has a low fundamental frequency voice) be able to use temporal periodicity cues to segregate and thus understand the voices of competing talkers.

Implantable defibrillators in hypertrophic cardiomyopathy

The implantable defibrillator (ICD) is one of the transformational technologies defining contemporary procedural cardiology. Advances in all aspects of device design have facilitated implantation and the detection, discrimination and correction...

Inappropriate ICD Discharges in Single‐Chamber Versus Dual‐Chamber Devices in the Pediatric and Young Adult Population

Implantable cardioverter defibrillator (ICD) use is increasing in young patients and is frequently complicated by inappropriate device discharges (IDs), leading to discomfort, anxiety and, potentially, proarrhythmia. Dual-chamber (DC) ICDs may decrease IDs by improving rhythm discrimination, but are associated with increased size, expense, and implant complications. We examined whether the frequency of IDs was the same in dual- and single-chamber (SC) ICDs in young patients. A multicenter review of patients <or=30 years of age with ICDs was performed. Demographic data and number of appropriate discharges (ADs) and IDs were collected. ADs and IDs were categorized after review of the episode by the primary electrophysiologist. Of 168 subjects (SC = 52; female = 76), 41 patients received 139 ADs, while 35 patients received 159 IDs. There were no differences related to gender or primary diagnosis, but patients with SC versus DC devices were younger (12.3 +/- 5.0 years vs 14.9 +/- 4.4 years, P < 0.0001) at implant. SC and DC devices were implanted with the same frequency for primary and secondary prevention. There were no significant differences in the incidence of IDs or ADs between the patients with SC or DC devices (AD: 12/52 SC vs 29/116 DC, P = 0.79; ID 7/52 SC vs 28/116 DC, P = 0.13). In this cohort of young patients, DC ICDs did not provide added protection from IDs. Hence, the added complexity and cost of an atrial lead appear unwarranted if used solely for assistance with rhythm discrimination in young patients.

Impairment of beat-based rhythm discrimination in Parkinson's disease

Humans often synchronize movements to the beat, indicating that motor areas may be involved in detecting or generating a beat. The basal ganglia have been shown to be preferentially activated by perception of rhythms with a regular beat ( Grahn and Brett, 2007), but their necessity for beat-based rhythm processing has not been proven. Previous research has shown that Parkinson's disease (PD) patients are impaired in timing of isochronous intervals ( Harrington et al., 1998a; O'Boyle et al., 1996), but little work has tested more complex rhythms. In healthy volunteers, behavioural performance is better for rhythms with a beat than without a beat ( Essens, 1986). We tested PD patients and controls on a rhythm discrimination task to determine if basal ganglia dysfunction results in an impairment of processing rhythms that have a beat. Unlike rhythm reproduction, discrimination has no motor requirements that are problematic for patients. Half the rhythms had a beat-based structure, and half did not. Subjects heard a rhythm twice and then indicated if a third presentation of the rhythm was the same or different. We predicted that PD patients would benefit less from beat structure than controls, resulting in a group by rhythm-type interaction, with reduced relative performance for the beat-based sequences in the PD group. Indeed this was the pattern of the results. In the control group, a significant advantage was observed for discrimination of rhythms with a beat compared to those without a beat. This advantage was greatly reduced in the PD group. Discrimination of beat-based rhythms was significantly impaired in PD patients compared to controls, whereas discrimination of non-beat-based rhythms did not differ significantly. This suggests that the basal ganglia are part of a system involved in detecting or generating an internal beat, and that this system is compromised in patients with Parkinson's disease.

Contribution of morphology discrimination algorithm for improving rhythm discrimination in slow and fast ventricular tachycardia zones in dual-chamber implantable cardioverter-defibrillators

Morphology discrimination (MD) is an algorithm based on QRS morphology analysis, that can be used alone or in various combinations with other discriminators in order to diagnose ventricular tachycardia (VT) [the implantable cardioverter-defibrillator (ICD) may be set to diagnose VT if 'Any' or 'All' the discriminators indicate VT)]. We evaluated the contribution of MD in terms of Specificity (SP) and Sensitivity (SE) of rhythm discrimination in slow and fast VT zones (rates <150 bpm and between 150 and 180 bpm, respectively). Detection results (682 spontaneous episodes in 58 patients) were corrected for multiple episodes within a patient (generalized estimating equations method). Rhythm discrimination in slow VT zones was characterized by SE and SP below 80% without MD, while the use of MD alone allowed to enhance SP, maintaining SE at 96%. Use of MD in combination with other discriminators resulted in a decrease in SP (setting 'Any'). In fast VT zones, MD allows an increase in SE for VT detection from around 82% up to approximately 94%, coupled with an SP of 95-96%., although SP is much higher with MD alone (94.8%) than with any other combination (78.4%). Both in slow and fast VT zones, use of multiple discriminators with the setting 'All' resulted in an unacceptable decrease in SE. MD in a dual-chamber ICD in combination with a rate branch classification system makes it possible to achieve a very high SP in discriminating detected events both in slow and fast VT zones, while maintaining SE for VT detection.