ABCD Trial Key Points
·
MTWA
(non-invasive, low-risk) is comparable to EPS (invasive) in predicting
ventricular tachyarrhythmias and SCD.
·
When
MTWA and EPS are combined, predictive performance is improved even further.
Key
Quotes:
“Recent randomized trials that
selected patients for ICD insertion on the basis of reduced left ventricular
ejection fraction (LVEF) alone (4,5) …
demonstrated an improvement in mortality rates but did so with relatively
low therapeutic efficiency (15 to 17 ICDs/life
saved). Consequently, although guidelines recommend prophylactic ICDs
in
most
patients with LVEF ≤ 0.35, the majority of inserted ICDs never
deliver therapy (6). Concerns regarding device complications, including worsening heart failure,
inappropriate shocks, and device recalls, and the impact on health care
costs (7) have also prompted a re-examination of this strategy (8).”
“The ABCD trial provides a unique
opportunity for comparing risk stratification strategies in a relevant and
large cohort of patients. We found that ICD insertion directed by noninvasive
MTWA testing is comparable to one guided by EPS in predicting the risk of
ventricular tachyarrhythmias or SCD in patients with
coronary artery disease, LVEF ≤ 0.40, and NSVT. In addition, by
using the tests in a complementary fashion, the efficiency of SCD prevention is
increased further.”
“Initial recommendations for ICD
insertion for primary prevention of SCD included NSVT and inducibility
at EPS (1,2). Such a strategy identifies a
high-risk group of patients, but it is costly, invasive, and hence
impractical for broad-based screening. Although EPS is no longer generally used for this
purpose, excellent data show that the cost-effectiveness of primary
prevention of SCD and reduction in total mortality are doubled if risk
stratification is used to guide ICD insertion (9,19). Therefore, despite the
evolution in practice standards, the results of the ABCD trial remain highly
relevant to contemporary issues regarding optimal selection of
patients for primary prevention of SCD. In fact, the comparable
predictive accuracy of noninvasive MTWA testing carries significant clinical
importance, because this
test can obviously be applied more broadly in clinical
practice than EPS.”
Additional
notes:
·
While
the results of ABCD are fairly positive, the majority (87%) of all pts in ABCD
had ICDs; thus, the endpoint issue likely impacted
the results. Hence, the NPV (95%) is slightly lower than previously
reported studies. Dr. Rosenbaum acknowledges the endpoint issue in the
discussion.
“Because most patients (87%) received ICDs (i.e., a very sensitive detector of events) programmed
in a consistent fashion, one can argue that by overestimating the number of SCD
events, the ABCD trial underestimated the potential NPV that could be achieved
by MTWA testing. This highlights an important limitation of surrogate end
points derived from ICDs.”