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T Wave Alternans in high arrhythmic risk patients: analysis in time and frequency domains: a pilot study.

Hunt AC - BMC Cardiovasc Disord (2002)

Bottom Line: Time domain, resultant absolute difference vectors (ATA), were calculated for alternate resultant T wave sequences.Cross spectral analysis showed no significant differences in group ATA frequency content.The frequency content and microvolt magnitude of T wave alternans was not significantly different in these two groups.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cardio-Analytics, ITTC 2, Tamar Science Park, Davy Road, Derriford, Plymouth, UK PL6 8BX. tony.hunt@talk21.com

ABSTRACT

Background: T wave alternans (TA) is a repolarisation phenomenon manifesting as a microvolt beat to beat change in the amplitude of the T wave and ST segment. TA has been shown to be a predictor of arrhythmic risk in unselected myocardial infarction populations. TA has not been used to differentiate risk within the ischaemic cardiomyopathy population.

Methods: The subjects investigated comprised, Group 1: 7 stable patients with remote (>20 months) extensive myocardial scarring and no arrhythmic events (NYHA 3 and 4). Group2: 9 post infarction patients with malignant arrhythmia and implantable defibrillator. During breath holding, 20 continuous QRST complexes from each patients X, Y and Z leads were digitally recorded. Time domain, resultant absolute difference vectors (ATA), were calculated for alternate resultant T wave sequences. Group differences between the magnitude and temporal distribution of mean ATAs and their spectral and cross-spectral analysis were compared.

Results: Group 1 v Group 2 mean ATAs were 10.7 (7.17) v 11.7 (8.48) respectively, not significant. Each group had a homogenous temporal distribution of ATAs. Both group's largest mean ATA frequency components were between 0 to 25 Hz, the largest ATA component being at the DC frequency. Cross spectral analysis showed no significant differences in group ATA frequency content.

Conclusion: The frequency content and microvolt magnitude of T wave alternans was not significantly different in these two groups. The specificity of T wave alternans for differentiating arrhythmic risk in post infarction scarring and heart failure needs investigation.

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Cross-Spectral analysis for the resultant vectored absolute mean TA for both groups. The y axis is the magnitude of cross-spectral frequency components and the x axis is in Hertz. Note that all positive values indicate the presence of a common frequency component between both groups with expected large magnitudes in the frequency range between 0 to 40 Hertz.
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Figure 5: Cross-Spectral analysis for the resultant vectored absolute mean TA for both groups. The y axis is the magnitude of cross-spectral frequency components and the x axis is in Hertz. Note that all positive values indicate the presence of a common frequency component between both groups with expected large magnitudes in the frequency range between 0 to 40 Hertz.

Mentions: An example of the time aligned alternate sequences of ST-T waves over 400 milliseconds duration is shown in figure 2. The mean value and standard deviation for each group member ATA are shown in Table 1. There was no significant difference between the means for groups 1 and 2 mean ATAs. The mean value and standard deviation for group 1 v group 2 being 10.7 microvolts (standard deviation= 7.17 microvolts) v 11.74 microvolts (standard deviation= 8.48 microvolts) respectively. All the values for the difference between ensemble averaged T waves for each vector in each patient are shown in table 1. There was no intra or inter-group significant difference in the mean values between the first, second or third time intervals for each groups mean ATA. The mean values for first, second and third intervals for Group 1 v Group 2 being 6.59 v 7.17, 6.37 v 7.96 and 6.06 v 6.18, respectively. The Power Spectrum for each groups resultant absolute difference vector between alternate sequences of ensemble averaged ST-T waves showed the largest values between 0 and 25 Hertz with maximum significant differences at the mean or DC frequency, see figures 3 and 4. The cross spectral density function showed that both groups shared the same frequency components, see figure 5. There was no significant group differences between the mean magnitudes of frequency band 80–500 Hertz for Group 1 v Group 2. The standard deviation in this band for Group 1 (noise) = 0.562, the mean magnitudes for Group 1 v Group 2 in this band being 0.615 v 0.823.


T Wave Alternans in high arrhythmic risk patients: analysis in time and frequency domains: a pilot study.

Hunt AC - BMC Cardiovasc Disord (2002)

Cross-Spectral analysis for the resultant vectored absolute mean TA for both groups. The y axis is the magnitude of cross-spectral frequency components and the x axis is in Hertz. Note that all positive values indicate the presence of a common frequency component between both groups with expected large magnitudes in the frequency range between 0 to 40 Hertz.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC101381&req=5

Figure 5: Cross-Spectral analysis for the resultant vectored absolute mean TA for both groups. The y axis is the magnitude of cross-spectral frequency components and the x axis is in Hertz. Note that all positive values indicate the presence of a common frequency component between both groups with expected large magnitudes in the frequency range between 0 to 40 Hertz.
Mentions: An example of the time aligned alternate sequences of ST-T waves over 400 milliseconds duration is shown in figure 2. The mean value and standard deviation for each group member ATA are shown in Table 1. There was no significant difference between the means for groups 1 and 2 mean ATAs. The mean value and standard deviation for group 1 v group 2 being 10.7 microvolts (standard deviation= 7.17 microvolts) v 11.74 microvolts (standard deviation= 8.48 microvolts) respectively. All the values for the difference between ensemble averaged T waves for each vector in each patient are shown in table 1. There was no intra or inter-group significant difference in the mean values between the first, second or third time intervals for each groups mean ATA. The mean values for first, second and third intervals for Group 1 v Group 2 being 6.59 v 7.17, 6.37 v 7.96 and 6.06 v 6.18, respectively. The Power Spectrum for each groups resultant absolute difference vector between alternate sequences of ensemble averaged ST-T waves showed the largest values between 0 and 25 Hertz with maximum significant differences at the mean or DC frequency, see figures 3 and 4. The cross spectral density function showed that both groups shared the same frequency components, see figure 5. There was no significant group differences between the mean magnitudes of frequency band 80–500 Hertz for Group 1 v Group 2. The standard deviation in this band for Group 1 (noise) = 0.562, the mean magnitudes for Group 1 v Group 2 in this band being 0.615 v 0.823.

Bottom Line: Time domain, resultant absolute difference vectors (ATA), were calculated for alternate resultant T wave sequences.Cross spectral analysis showed no significant differences in group ATA frequency content.The frequency content and microvolt magnitude of T wave alternans was not significantly different in these two groups.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cardio-Analytics, ITTC 2, Tamar Science Park, Davy Road, Derriford, Plymouth, UK PL6 8BX. tony.hunt@talk21.com

ABSTRACT

Background: T wave alternans (TA) is a repolarisation phenomenon manifesting as a microvolt beat to beat change in the amplitude of the T wave and ST segment. TA has been shown to be a predictor of arrhythmic risk in unselected myocardial infarction populations. TA has not been used to differentiate risk within the ischaemic cardiomyopathy population.

Methods: The subjects investigated comprised, Group 1: 7 stable patients with remote (>20 months) extensive myocardial scarring and no arrhythmic events (NYHA 3 and 4). Group2: 9 post infarction patients with malignant arrhythmia and implantable defibrillator. During breath holding, 20 continuous QRST complexes from each patients X, Y and Z leads were digitally recorded. Time domain, resultant absolute difference vectors (ATA), were calculated for alternate resultant T wave sequences. Group differences between the magnitude and temporal distribution of mean ATAs and their spectral and cross-spectral analysis were compared.

Results: Group 1 v Group 2 mean ATAs were 10.7 (7.17) v 11.7 (8.48) respectively, not significant. Each group had a homogenous temporal distribution of ATAs. Both group's largest mean ATA frequency components were between 0 to 25 Hz, the largest ATA component being at the DC frequency. Cross spectral analysis showed no significant differences in group ATA frequency content.

Conclusion: The frequency content and microvolt magnitude of T wave alternans was not significantly different in these two groups. The specificity of T wave alternans for differentiating arrhythmic risk in post infarction scarring and heart failure needs investigation.

Show MeSH
Related in: MedlinePlus