Author + information
- Colette E. Jackson, MB ChB, PhD⁎ (, )
- Rachel C. Myles, MB ChB, PhD,
- Stuart M. Cobbe, MD,
- Mark C. Petrie, MB ChB and
- John J.V. McMurray, MD
- ↵⁎British Heart Foundation Cardiovascular Research Centre, University of Glasgow, 126 University Place, Glasgow G12 8TA, United Kingdom
Verrier et al. (1) review the evidence regarding clinical utility of microvolt T-wave alternans (MTWA) testing, suggesting that it may be used to identify patients at risk of life-threatening ventricular arrhythmias. In light of conflicting results from recent clinical studies, an overview for the practicing clinician is much needed. However, there are important issues that are not addressed.
In their review, the authors do not mention that patients with atrial fibrillation, which is highly prevalent in heart failure (10% to 50%) (2), are unsuitable for spectral MTWA testing. Furthermore, exercise intolerance and continuous ventricular pacing also preclude MTWA testing. Even if MTWA was demonstrated to improve risk stratification, alternative strategies would be required for the significant proportion of ineligible patients.
The authors also admit that MTWA is not consistently predictive of arrhythmic events in patients with an implanted cardioverter-defibrillator (ICD), suggesting 2 possible explanations for this anomaly: use of appropriate ICD discharge as an endpoint, and differences in beta-blocker use. However, the possibility that MTWA does not accurately predict ventricular arrhythmias is not addressed. The authors correctly point out that an appropriate ICD discharge is not a surrogate for sudden cardiac death, but do not acknowledge that it is a more accurate record of ventricular arrhythmias than can be obtained in patients without ICDs. If MTWA cannot accurately predict ventricular arrhythmias, then it follows that it cannot predict ICD benefit. Indeed, Verrier et al. (1) acknowledge that MTWA has no utility in guiding therapy.
Despite the fundamental deficiencies in the evidence base for MTWA as a risk stratification tool, and their clear statement that it cannot be used to guide therapy, the authors conclude that it is reasonable to consider MTWA testing in patients at risk of lethal arrhythmias. This is inappropriate in a clinical guideline. It is not economical, potentially harmful, and therefore unethical to subject patients to a futile investigation that can have no influence on their subsequent management. With the currently available evidence, MTWA cannot be endorsed as having any role in identifying patients at high risk of a lethal arrhythmia who may benefit from an ICD. The alternative strategy of using a negative MTWA test to identify patients unlikely to benefit from an ICD requires testing in a prospective study. Arrhythmia risk stratification remains challenging, and efforts to optimize our approach must continue, but until evidence demonstrates that MTWA results are clinically meaningful, then we believe that its use, other than in clinical research, is not reasonable and should not be encouraged.
- American College of Cardiology Foundation