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Microvolt T-wave alternans during exercise and pacing are not comparable
Karin Kraaier1, Patrick M J Verhorst, Job van der Palen
1Department of Cardiology, Thoraxcentrum Twente, Medisch Spectrum Twente, Haaksbergerstraat 55, 7513 ER Enschede, The Netherlands.
Summary
Microvolt T-wave alternans (MTWA) testing during pacing reduces indeterminate results compared to exercise. However, concordance between different MTWA testing protocols needs further investigation for high-risk patients.
Area of Science:
- Cardiology
- Electrophysiology
- Biomedical Engineering
Background:
- Microvolt T-wave alternans (MTWA) absence indicates low risk for ventricular arrhythmia and sudden cardiac death.
- Exercise-assessed MTWA yields indeterminate results in 20-40% of cases, limiting its clinical utility.
- Pacing protocols may offer a more reliable method for MTWA assessment.
Purpose of the Study:
- To investigate whether MTWA testing during atrial-pacing (A) and atrioventricular-pacing (AV) protocols results in fewer indeterminate findings compared to exercise (E) testing.
- To evaluate the concordance of MTWA results between different testing modalities (E, A, AV) in patients with ischaemic cardiomyopathy.
Main Methods:
- Thirty patients with ischaemic cardiomyopathy and implanted cardioverter-defibrillators underwent sequential MTWA testing.
- Testing protocols included exercise (E), atrial-paced (A), and atrioventricular-paced (AV).
- Indeterminate and positive results were analyzed for concordance across protocols.
Main Results:
- Indeterminate MTWA test results were significantly lower during pacing (A: 17%, AV: 3%) compared to exercise (37%) (P < 0.015).
- Concordance rates between protocols were moderate, with the highest agreement between A and AV pacing (70%).
- Excluding indeterminate results did not substantially improve agreement between protocols.
Conclusions:
- Pacing protocols for MTWA testing significantly reduce the occurrence of indeterminate results compared to exercise testing.
- Low concordance rates between different MTWA testing protocols highlight the need for further research.
- The predictive value of each MTWA testing method in high-risk ischaemic cardiomyopathy patients requires additional investigation.
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