What is a microvolt T-wave alternans test?
Microvolt T-wave alternans (TWA) is a noninvasive test of arrhythmia vulnerability. The results of previous observational studies showed that TWA predicts ICD shocks or arrhythmic events in diverse patient populations,12–17 including those with heart failure and ischemic cardiomyopathy.
What are wave alternans?
T-wave alternans is a beat-to-beat alternation of the amplitude and/or shape of the T-wave on the surface ECG. These fluctuations of the T-wave are primary and not related to alternans of other components of the ECG (i.e. QRS alternans).
What does electrical alternans indicate?
Electrical alternans is defined as alternating QRS amplitudes in any or all leads on an electrocardiogram (ECG) with no additional evident changes in conduction pathways of the heart. This rhythm is typically associated with pericardial effusion from fluid surrounding the heart.
What is a notched T wave?
Notched T waves, also called bifid waves or humps, were defined as a bulge or protuberance just beyond the apex or on the descending limb of an upright T wave.
What is the T wave?
T-wave alternans has long been recognized as a marker of electrical instability in acute ischemia, where it may precede ventricular tachyarrhythmia. Studies have shown that T wave (or ST-T) alternans can also precede non-ischemic ventricular tachyarrhythmias.
What is MTWA in medical terms?
Aetna considers microvolt T-wave alternans (MTWA) diagnostic testing using the spectral analytic method medically necessary for the evaluation of persons at risk of sudden cardiac death who meet criteria for implantable cardioverter-defibrillator placement.
What is MTWA test?
Puljevic and colleagues (2019) noted that MTWA testing is a beat-to-beat fluctuation in the amplitude of T wave. These investigators examined if MTWA could be a new non-invasive tool for detecting reversible ischemia in patients with suspected coronary artery disease (CAD) without structural heart disease; if MTWA could detect ischemia earlier and with greater test accuracy compared with exercise electrocardiogram (ECG) ST-segment testing, and if threshold value of MTWA and heart rate at which the alternans is estimated could be different compared to standard values. A total of 101 patients with suspected stable coronary disease, but without structural heart disease, were included. Echocardiography, exercise ECG test, MTWA with classical and modified threshold alternans values, and coronary angiography were performed. Approximately 33.3 % patients had a false-positive (FP) result on exercise ECG test. The sensitivity of exercise ECG ST-segment test in the detection of CAD was 97.8 %, and the specificity was 42.5 % (diagnostic odds ratio [DOR] 33.89). In a group of angiographically positive patients, standard MTWA accurately identified 60 % of patients, while 40 % had a false-negative (FN) result. Approximately 91.8 % patients with negative angiography result were accurately identified with 8.2 % FPs). The sensitivity of MTWA was 59.61 % and specificity 91.83 %. Best ratio of sensitivity and specificity (86.53 % and 95.91 %, DOR 151.06) had modified criteria for positive MTWA (MTWA greater than 1.5 µV at heart rate of 115 to 125/min). The authors concluded that the findings of this study showed that MTWA could be the new non-invasive tool for the detection of reversible ischemia in patients with suspected CAD without structural heart disease. Furthermore, MTWA can detect ischemia earlier and with greater accuracy compared with exercise ECG testing.
What is sustained MTWA?
Cheung et al (2002) stated that sustained MTWA is a marker of increased risk for malignant ventricular arrhythmia (VA). There is a significant risk of arrhythmia and sudden death after repair of congenital heart disease. These researchers determined the prevalence and characteristics of TWA after repair of tetralogy of Fallot (TOF). T-wave alternans was evaluated during bicycle exercise in 49 subjects who had consecutively undergone transatrial-transpulmonary repair. Median values for age, age at repair, and follow-up duration were 14.9 years (11.5 to 20.8), 1.6 years (0.2 to 4.9), and 11.6 years (9.4 to 17.2), respectively. All patients were in New York Heart Association (NYHA) functional class I and were asymptomatic. Median QRS duration was 120 msec (80 to 150). Sustained TWA was detected in 7 (23 %) of 31 subjects with adequate tests. In these 7 subjects, median onset heart rate (HR) was 120 (98 to 155). Median HR threshold as a percentage of predicted maximum HR (220 – age) was 58 % (48 to 77). Sustained TWA prevalence was not significantly different compared with normal subjects (7/31 versus 9/83; p = 0.1). Onset HR in the TOF group was significantly lower [mean (SD) of 122 (20) versus 139 (12), p < 0.05]. In the TOF group with sustained TWA, the TWA occurred in 4 of 7 at less than 60 % predicted maximum HR versus 1 of 9 normal subjects (p < 0.05); 3 of 7 had onset HR less than 120 versus 0 of 9 normal subjects (p < 0.03). There was no significant difference in age, gender, transannular patch use, restrictive right ventricular physiology, QRS duration, QTc, QT/QRS dispersion, or non-sustained ventricular tachycardia in subjects with or those without sustained TWA. The authors concluded that the onset HR for sustained TWA was significantly lower after repair of TOF. They stated that further study is needed to examine if this represents an increased risk for arrhythmia in this patient group.
Is MTWA associated with sudden cardiac death?
Koo and colleagues (2019) stated that MTWA is known to be associated with arrhythmia or sudden cardiac death in high-risk patients. These investigators examined the relationship between MTWA and post-operative mortality in 330 cardiac surgery patients. Electrocardiogram, official national data and electric chart were analyzed to provide in-hospital and mid-term outcome. MTWA at the end of surgery was significantly associated with in-hospital mortality in both uni-variate analysis (OR = 27.378, 95 % CI: 5.616 to 133.466, p < 0.001) and multi-variate analysis (OR = 59.225, 95 % CI: 6.061 to 578.748, p < 0.001). Cox proportional hazards model revealed MTWA at the end of surgery was independently associated with mid-term mortality (HR = 4.337, 95 % CI: 1.594 to 11.795). The area under the curve (AUC) of the model evaluating MTWA at the end of surgery was 0.764 (95 % CI: 0.715 to 0.809) and it increased to 0.929 (95 % CI: 0.896 to 0.954) when combined with the EuroSCORE II. The authors concluded that MTWA positive at the end of surgery had a 60-fold increase in in-hospital mortality and a 4-fold increase in mid-term mortality. Moreover, MTWA at the end of surgery could predict in-hospital mortality and this predictability was more robust when combined with the EuroSCORE II. Moreover, these researchers stated that additional studies on the robustness of MTWA as predictive marker in a larger cohort are needed.
Decision Summary
CMS was asked to reconsider our national coverage determination (NCD) on microvolt T-wave alternans (MTWA) diagnostic testing to extend coverage to the modified moving average (MMA) method. CMS' interest in MTWA testing is in the risk stratification of Medicare beneficiaries who may be at risk for sudden cardiac death (SCD).
Proposed Decision Memo
CMS was asked to reconsider our national coverage determination (NCD) on microvolt T-wave alternans (MTWA) diagnostic testing to extend coverage to the modified moving average (MMA) method. CMS' interest in MTWA testing is in the risk stratification of Medicare beneficiaries who may be at risk for sudden cardiac death (SCD).
Bibliography
Adam DR, Smith JM, Akselrod S, Nyberg S, Powell AO, Cohen RJ. Fluctuations in T-wave morphology and susceptibility to ventricular fibrillation. J Electrocardiol. 1984;17 (3):209-218.
I. Proposed Decision
- CMS was asked to reconsider our national coverage determination (NCD) on microvolt T-wave alternans (MTWA) diagnostic testing to extend coverage to the modified moving average (MMA) method. CMS' interest in MTWA testing is in the risk stratification of Medicare beneficiaries who may be at risk for sudden cardiac death (SCD). CMS proposes that there...
II. Background
- A. Sudden Cardiac Death SCD is generally defined as a sudden and unexpected pulseless event due to an underlying primary cardiac event (Chugh 2004, Myerburg 1994). A National Institutes of Health (NIH) work group has provided operational definitions for established and probable SCD (NIH workshop 2009, Fishman 2010). An established case of SCD is an unexpected death witho…
III. History of Medicare Coverage
- A. Prior Requests CMS has previously reviewed the scientific literature for MTWA as a diagnostic test for beneficiaries at risk of SCD. On March 21, 2006, CMS established national coverage for MTWA using the SA methodology only. That NCD was based on the SA method's predictive value of who was thought to not likely benefit from ICD therapy (http://www.cms.gov/medicare-covera…
v. FDA Status
- The FDA has cleared two methods of MTWA testing through the 501(k) process: Cambridge Heart’s spectral analysis (SA) method and General Electric’s modified moving average (MMA) method. While the focus of this NCD is the MMA method, we discuss both devices for purposes of comparison. The FDA cleared GE’s initial device for MTWA testing using the MMA method on De…
VI. General Methodological Principles
- When making national coverage determinations, CMS evaluates relevant clinical evidence to determine whether or not the evidence is of sufficient quality to support a finding that an item or service falling within a benefit category is reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member consist…
VII. Evidence
- The evidence reviewed includes the published medical literature on pertinent clinical studies using the MMA method for MTWA testing. Is the evidence sufficient to conclude that MTWA testing using the MMA method improves health outcomes for Medicare beneficiaries who are candidates for ICD placement? 2. External Technology Assessments CMS did not request an external techn…
VIII. CMS Analysis
- A. General National coverage determinations (NCDs) are determinations by the Secretary with respect to whether or not a particular item or service is covered nationally by Medicare (§1869(f)(1)(B) of the Act). In order to be covered by Medicare, an item or service must fall within one or more benefit categories contained within Part A or Part B, and must not be otherwise excl…
Appendices
- General Methodological Principles of Study Design (Section VI of the Decision Memorandum) When making national coverage determinations, CMS evaluates relevant clinical evidence to determine whether or not the evidence is of sufficient quality to support a finding that an item or service is reasonable and necessary. The overall objective for the critical appraisal of the eviden…
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