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Elimination of short RR intervals during atrial fibrillation by a ventricular pacing algorithm
Journal of Electrocardiology Vol 28 Supplement
Session V Posters A SequemtialTechniquefor CardiacArrhythmia Discrimination Szi-WenChert, PeterM. Clarksoaand Qi Fan BiomedicalEngineeringCenter The Ohio Sta~eUniversity,Columbus,OH A novelalgorithmforarrhythmiadiscriminationbasedon a modifiedform
Insight into Myocardial FuncZion from the Pacemaker QRS Complex Siegfried H. Recke,MD,Universi~y Heart Centre 91054 Erlangen, Fed~ Rep. of Germany The information derived from the paced QRS may be essential in the absence of n o r m a l ly conducted beats of poor echo subjects.To address its value in assessing left ventricular ejection f r a c t i o n (EF) 83 patients (65.9+9 y) with normal a n g i o EF -~ 60% (Group I) are compared w i t h @7 patients (64.2+9 y) with depressed EF<60 % (Group 2). G~oup 2 patients reveal h i g h l y significant increases of the end-~iastolic volume iDdex (EDVI) (I ~0.8+60.9 ml/m z vs 87.5+25.5 m/mm)and paced QRS d ~ r a t i o n (191.8+19.4- m~ vs 167.9+15.6 ms), a significamt i~crease of the pa~ed amplitudes RI+SVS, but no difference of RaVL+SaVF+maximum precordial S. To examine whether the increased E_DVI or the decreased EF might be responsible for the findings, 66 subjects with normal EF and EDVI -~ 100 ml/mZ(Group 5) are compared with217 patients with normal EF but E D V I > I O0 ml/m .Although there are highly significant differences of the ED¥I between the groups, the paced QRS dumations and the paced QKS voltages are not significantly affected. If Group 3 is compared with 14- subjects h a v i n g EDVI-ZI00 m l / m 2 and depressed EF, the low EF group again showed a highly significant increase of the oaced ORS duration.
of the sequential probability ratio test (SPRT) is described. The algorithm
avoidsdependenceon heartrateby utilizinga aew irregularity measure, dubbed bla,~ng variability (BV), as the basis for discrimination. BV is computed as the normalized change of rate as a function of the blanking inte~al (BI). BV corresponds to the normalized change in mean rate as
theBI isvaried.RatesforthreeseparateBig in the range60-100ms are computedand BV iscalculatedfroma movingwindowofthesevalues.The SPRT algorithmcomparesBV valuesobtainedsequentiallywithmi-lmum probability of error thresholds derived from empirical distributions for the arrhyehmias considered. This comparison is repeated as each new BV value is computed until a decision is reached. The potential for the proposed method is demonstrated using the examplesof ventricular tachycerdia (VT) and ventricular fibrillation (VF). A set of ECG data vectors of VF and VT obtained from the malignant arrhythnfia subset of the MIT-BIH database was adopted for evaluation purposes. The orig4.nat data were divided into ~wo groups corresponding to episodes of VF and VT contain{n~ 30 and 70 ECG data segments, respectively. Each segment comprises a 20-second recording. Applying the proposed algorithm to perform the classification usingdatafrom theMIT-BIIIdatabase,we haveobtaineda tota2 2redlctive accuracy (TPA) of 95% (VF=93%, VT=96%). This is significantly higher ~han was obtained by applying ~be algorithm using average rate as the parameter, which produced a TPA of 84% (VF=90%, VT=gI%) for the same datab~.~e.
Elimination of Short RK Intervals Dvxing Atrial PibfiUafion by" a Ventficular Pacing Algoritl~ Saul Greenhut Phl), Albert Dawson PhD, Brace Steinhaus PhD, Telectronics Pacing Systems, Eng/ewood, CO USA
A Robust Adaptive Estimator of Rate for Cardiac Arrhyt hmia Detection Qi Fan and PeterM. Clarkson,BiomedicalEngineeringCenter, The Ohio StateUniversity,Columbus,Ohio 43210
previous wozk has shown that ventricular pacing during atrial fibrillation (AP) at pacing intervals greater than the minimum intrinsic ventdcular interval stabilizes the rate by eliminating shorter RR intervals. The purpOse of this smdF was to develop and test a ventricular rate stabilization (V'RS) pacing algorithm suitable for pacemakerimplementadon. The algodtlma increases the pacing rate by 5 pul..ms/min when RR variability over 8 cycles exceeds a threshold and decreases the pacing rate by 5 pulses[n0n when the threshold has not been exceeded for 128 cycles. The ability 0£ the VRS pacing algorithm to eliminate shorter RR intervals was examined in 6 dogs. Sustained AF was induced by increasing vagal tone using morphine IM as a pre-anesthetic, followed by atrial burst (45 Hz, 1 sec) pacing. Four thresholds (5, 10, 20, 30%), representing the allowed variability without a pacing rate increase, were stu~ed. AF control passages (no VRS pacing) preceded and followed each episode of V'RS pacing. The VRS algorithm was also tested using a previous computermodel of the venUiculerre~jense to AF. Results: Measure Threshold: 5% 10% 20% ] 30% % R R Intervals, Less Than 90_+7 8 2 + 1 2 52+21 I 25±15 p~cln~ Interval, Eliminated Mean % Heart Rate Increase 7+17 0±t2 -44_-8 -4~7 % Facing 96±3 9t!-6 69+18 45+_22 Conclusions: 1) The VRS algorithm eliminated a considerable percent of RR intervals less than the ventricuh'tr pacing interval with little change in heart rate; 2) Lower variability thresholds eliminated a greater percent of sho~ RR cyctes than higher thresholds, but pacing was at higher rates and for a greater percent of cycles. Computer model testing verified that pacing suppression of AV nodal automaticity is a possible mechamsm for this phenomenon.
We propose a robust, adaptive caxdiac rate estimation algorithm for use in automatic implautable cardioversion/defibrillation devices. The algorithm consists of a two-stage processor applied to raw heart rate measurements. The processor comprises outlier detection and remowd followed by adaptive trimmed mean filtering. Outliers axe detected by comparing raw rate values with the Median Absolute Deviation ( M A D ) calculated over a moving window of observations. The residual data axe subjected to a trimmed mean filter, where the trimming para~meter is adapted according to a local measure of the ~ra,R behavior' of the observations. The performance characteristics of the proposed estimator aze examined. The concept of breakdown point is utilized to quaatlfy robustness. The estimator is shown to be as robust as the median filter, and capable of closely tracking rapid changes in rate, while at same time improving efficiency comma,red to other robust estimators. The algorithm has been tested using both simulated data from known distributions and experimental data from the electrophysiology laboratory. For simulated data, we have obtained significa~ut reductions in mean-squared estimation error in comparison to averaging and other simple estimators, and performance that is close to the minimum mean-squaxed error corresponding to the fixed optimal estimator, but u~/~hout prior knowledge of the data distribution. Observations from experimental data confirm that the algorithm effectively removes outliers from rate observations, and can also track step-like transient changes i= rate, resulting in significantly improved estimates.
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162
Session V Posters A SequemtialTechniquefor CardiacArrhythmia Discrimination Szi-WenChert, PeterM. Clarksoaand Qi Fan BiomedicalEngineeringCenter The Ohio Sta~eUniversity,Columbus,OH A novelalgorithmforarrhythmiadiscriminationbasedon a modifiedform
Insight into Myocardial FuncZion from the Pacemaker QRS Complex Siegfried H. Recke,MD,Universi~y Heart Centre 91054 Erlangen, Fed~ Rep. of Germany The information derived from the paced QRS may be essential in the absence of n o r m a l ly conducted beats of poor echo subjects.To address its value in assessing left ventricular ejection f r a c t i o n (EF) 83 patients (65.9+9 y) with normal a n g i o EF -~ 60% (Group I) are compared w i t h @7 patients (64.2+9 y) with depressed EF<60 % (Group 2). G~oup 2 patients reveal h i g h l y significant increases of the end-~iastolic volume iDdex (EDVI) (I ~0.8+60.9 ml/m z vs 87.5+25.5 m/mm)and paced QRS d ~ r a t i o n (191.8+19.4- m~ vs 167.9+15.6 ms), a significamt i~crease of the pa~ed amplitudes RI+SVS, but no difference of RaVL+SaVF+maximum precordial S. To examine whether the increased E_DVI or the decreased EF might be responsible for the findings, 66 subjects with normal EF and EDVI -~ 100 ml/mZ(Group 5) are compared with217 patients with normal EF but E D V I > I O0 ml/m .Although there are highly significant differences of the ED¥I between the groups, the paced QRS dumations and the paced QKS voltages are not significantly affected. If Group 3 is compared with 14- subjects h a v i n g EDVI-ZI00 m l / m 2 and depressed EF, the low EF group again showed a highly significant increase of the oaced ORS duration.
of the sequential probability ratio test (SPRT) is described. The algorithm
avoidsdependenceon heartrateby utilizinga aew irregularity measure, dubbed bla,~ng variability (BV), as the basis for discrimination. BV is computed as the normalized change of rate as a function of the blanking inte~al (BI). BV corresponds to the normalized change in mean rate as
theBI isvaried.RatesforthreeseparateBig in the range60-100ms are computedand BV iscalculatedfroma movingwindowofthesevalues.The SPRT algorithmcomparesBV valuesobtainedsequentiallywithmi-lmum probability of error thresholds derived from empirical distributions for the arrhyehmias considered. This comparison is repeated as each new BV value is computed until a decision is reached. The potential for the proposed method is demonstrated using the examplesof ventricular tachycerdia (VT) and ventricular fibrillation (VF). A set of ECG data vectors of VF and VT obtained from the malignant arrhythnfia subset of the MIT-BIH database was adopted for evaluation purposes. The orig4.nat data were divided into ~wo groups corresponding to episodes of VF and VT contain{n~ 30 and 70 ECG data segments, respectively. Each segment comprises a 20-second recording. Applying the proposed algorithm to perform the classification usingdatafrom theMIT-BIIIdatabase,we haveobtaineda tota2 2redlctive accuracy (TPA) of 95% (VF=93%, VT=96%). This is significantly higher ~han was obtained by applying ~be algorithm using average rate as the parameter, which produced a TPA of 84% (VF=90%, VT=gI%) for the same datab~.~e.
Elimination of Short RK Intervals Dvxing Atrial PibfiUafion by" a Ventficular Pacing Algoritl~ Saul Greenhut Phl), Albert Dawson PhD, Brace Steinhaus PhD, Telectronics Pacing Systems, Eng/ewood, CO USA
A Robust Adaptive Estimator of Rate for Cardiac Arrhyt hmia Detection Qi Fan and PeterM. Clarkson,BiomedicalEngineeringCenter, The Ohio StateUniversity,Columbus,Ohio 43210
previous wozk has shown that ventricular pacing during atrial fibrillation (AP) at pacing intervals greater than the minimum intrinsic ventdcular interval stabilizes the rate by eliminating shorter RR intervals. The purpOse of this smdF was to develop and test a ventricular rate stabilization (V'RS) pacing algorithm suitable for pacemakerimplementadon. The algodtlma increases the pacing rate by 5 pul..ms/min when RR variability over 8 cycles exceeds a threshold and decreases the pacing rate by 5 pulses[n0n when the threshold has not been exceeded for 128 cycles. The ability 0£ the VRS pacing algorithm to eliminate shorter RR intervals was examined in 6 dogs. Sustained AF was induced by increasing vagal tone using morphine IM as a pre-anesthetic, followed by atrial burst (45 Hz, 1 sec) pacing. Four thresholds (5, 10, 20, 30%), representing the allowed variability without a pacing rate increase, were stu~ed. AF control passages (no VRS pacing) preceded and followed each episode of V'RS pacing. The VRS algorithm was also tested using a previous computermodel of the venUiculerre~jense to AF. Results: Measure Threshold: 5% 10% 20% ] 30% % R R Intervals, Less Than 90_+7 8 2 + 1 2 52+21 I 25±15 p~cln~ Interval, Eliminated Mean % Heart Rate Increase 7+17 0±t2 -44_-8 -4~7 % Facing 96±3 9t!-6 69+18 45+_22 Conclusions: 1) The VRS algorithm eliminated a considerable percent of RR intervals less than the ventricuh'tr pacing interval with little change in heart rate; 2) Lower variability thresholds eliminated a greater percent of sho~ RR cyctes than higher thresholds, but pacing was at higher rates and for a greater percent of cycles. Computer model testing verified that pacing suppression of AV nodal automaticity is a possible mechamsm for this phenomenon.
We propose a robust, adaptive caxdiac rate estimation algorithm for use in automatic implautable cardioversion/defibrillation devices. The algorithm consists of a two-stage processor applied to raw heart rate measurements. The processor comprises outlier detection and remowd followed by adaptive trimmed mean filtering. Outliers axe detected by comparing raw rate values with the Median Absolute Deviation ( M A D ) calculated over a moving window of observations. The residual data axe subjected to a trimmed mean filter, where the trimming para~meter is adapted according to a local measure of the ~ra,R behavior' of the observations. The performance characteristics of the proposed estimator aze examined. The concept of breakdown point is utilized to quaatlfy robustness. The estimator is shown to be as robust as the median filter, and capable of closely tracking rapid changes in rate, while at same time improving efficiency comma,red to other robust estimators. The algorithm has been tested using both simulated data from known distributions and experimental data from the electrophysiology laboratory. For simulated data, we have obtained significa~ut reductions in mean-squared estimation error in comparison to averaging and other simple estimators, and performance that is close to the minimum mean-squaxed error corresponding to the fixed optimal estimator, but u~/~hout prior knowledge of the data distribution. Observations from experimental data confirm that the algorithm effectively removes outliers from rate observations, and can also track step-like transient changes i= rate, resulting in significantly improved estimates.
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162