Novel algorithms improve arrhythmia detection accuracy in insertable cardiac monitors.

INTRODUCTION: Insertable cardiac monitors (ICMs) are commonly used to diagnose cardiac arrhythmias. False detections in the latest ICM systems remain an issue, primarily due to inaccurate R-wave sensing. New discrimination algorithms were developed and tested to reduce false detections of atrial fibrillation (AF), pause, and tachycardia episodes in ICMs. METHODS: Stored electrograms (EGMs) of AF, pause, and tachycardia episodes detected by Abbott Confirm Rx™ ICMs were extracted from the Merlin.net™ Patient Care Network, and manually adjudicated to establish independent training and testing datasets. New discrimination algorithms were developed to reject false episodes due to inaccurate R-wave sensing, P-wave identification, and R-R interval patterns. The performance of these new algorithms was quantified by false positive reduction (FPR) and true positive maintenance (TPM), relative to the existing algorithms. RESULTS: The new AF detection algorithm was trained on 5911 EGMs from 744 devices, resulting in 66.9% FPR and 97.8% TPM. In the testing data set of 1354 EGMs from 119 devices, this algorithm achieved 45.8% FPR and 97.0% TPM. The new pause algorithm was trained on 7178 EGMs from 1490 devices, resulting in 70.9% FPR and 98.7% TPM. In the testing data set of 1442 EGMs from 340 devices, this algorithm achieved 74.4% FPR and 99.3% TPM. The new tachycardia algorithm was trained on 520 EGMs from 204 devices, resulting in 57.0% FPR and 96.6% TPM. In the testing data set of 459 EGMs from 237 devices, this algorithm achieved 57.9% FPR and 96.5% TPM. CONCLUSION: The new algorithms substantially reduced false AF, pause, and tachycardia episodes while maintaining the majority of true arrhythmia episodes detected by the Abbott ICM algorithms that exist today. Implementing these algorithms in the next-generation ICM systems may lead to improved detection accuracy, in-clinic efficiency, and device battery longevity.

Novel ventricular tachyarrhythmia detection enhancement detects undertreated life-threatening arrhythmias.

BACKGROUND: Ventricular tachyarrhythmias (VTA) with low and varying signal amplitudes and morphologies may not be successfully identified utilizing traditional implantable cardioverter-defibrillator algorithms. OBJECTIVE: Develop and validate a novel algorithm (VF Therapy Assurance, VFTA) to improve detection and timely delivery of high-voltage therapy (HVT) for these arrhythmias. METHODS: Arrhythmia detection was simulated on recorded VTA electrograms (EGMs) utilizing Abbott's Merlin.net database. EGMs where an HVT occurred only when VFTA was enabled, or where VFTA provided an HVT >30 seconds earlier than without VFTA, were readjudicated with physician review. As VFTA never prevents detection or therapy, EGMs where VFTA did not activate or alter HVT were not adjudicated. RESULTS: Among 564,353 recorded VTA EGMs from 20,000 devices, VFTA altered HVT in 105 EGMs from 67 devices. Physician adjudication determined that 81.9% (86/105) of these EGMs were true undertreated VTA episodes and would have received appropriate HVT with VFTA enabled. Furthermore, 65% of the episodes (56/86) were ventricular fibrillation, were polymorphic, did not self-terminate during the recording window, or were not amenable antitachycardia pacing. Of those, 87.5% (49/56) would not have elicited HVT without VFTA. Overall, VFTA provided new or earlier appropriate HVT in 0.27% (53/20,000) of devices with an increase in inappropriate HVT in 0.07% (14/20,000) devices. CONCLUSION: The VFTA algorithm successfully identifies VTA missed by traditional detection algorithms, owing to undersensed ventricular signals resulting in the rate falling below the programmed detection rate. The use of VFTA increases the likelihood of delivering life-saving HVT.

Relation between achieved heart rate and outcomes in patients with atrial fibrillation (from the Atrial Fibrillation Follow-up Investigation of Rhythm Management [AFFIRM] Study).

Many patients with atrial fibrillation (AF) are treated with rate control and anticoagulation. However, the relation between the degree of heart rate (HR) control and clinical outcome is uncertain. We assessed whether lower achieved HR at rest and/or lower achieved exercise HR was associated with improved prognosis, quality of life (QoL), and functional status among patients in the AFFIRM study. Patients in the rate control arm and who were in AF at baseline and 2 months were included. Patients were grouped by quartile of achieved HR at rest (44 to 69, 70 to 78, 79 to 87, 88 to 148 beats/min) and achieved exercise HR following a 6-minute walk (53 to 82, 83 to 92, 93 to 106, 107 to 220 beats/min). QoL measurements and functional status were also analyzed. Complete data were available for 680 patients for achieved HR at rest, 349 patients for achieved exercise HR, and 118 patients for QoL. Survival free from cardiac hospitalization and overall survival were not significantly different among quartiles of achieved HR at rest (p = 0.19 and p = 0.8, respectively) or achieved exercise HR (p = 0.77 and p = 0.14, respectively). After controlling for covariates, there remained no significant relation between either achieved HR at rest or achieved exercise HR and event-free survival (hazard ratio 0.95, p = 0.35 and hazard ratio 0.98, p = 0.81) or overall survival (hazard ratio 1.03, p = 0.70 and hazard ratio 1.22, p = 0.13). Furthermore, there was no significant association between achieved HR and QoL measurements, New York Heart Association functional class, or 6-minute walking distance. After 2 months of drug titration, neither achieved HR at rest nor achieved exercise HR predicted survival free from cardiovascular hospitalization, overall survival, QoL, or functional status among patients with AF.