Benefit of CRT-D vs. ICD-only therapy by VTA risk-score
Among all non-LBBB patients enrolled in MADIT-CRT (i.e. with ICD or CRT-D), the 4-year cumulative probability of VTA was highest among CRT-D patients with RF (40%); intermediate in the ICD group (33%); and lowest among CRT-D without RF ([14%], log-rank p < 0.001 for the overall difference during follow-up [Figure 2; left panel]). Similarly, the 4-year cumulative probability of the composite of death or VTA was 51% in CRT-D patients with RF, 42% in the ICD-only group, and 22% in the CRT-D group without RF (log-rank p < 0.001 for the overall difference during follow-up [Figure 2: middle panel]); and the respective rates of appropriate defibrillator shock therapy were 28%, 19%, and 7% respectively (log-rank p = 0.008 for the overall difference during follow-up [Figure 2: right panel]).
Multivariate analysis showed that among non-LBBB patients with no RF, treatment with CRT-D therapy was associated with a statistically significant 61% (p=0.002) reduction in the risk of the primary VTA endpoint compared with ICD-only therapy. Similar results were shown for the secondary endpoints, wherein treatment with CRT was associated with a significant 50% (p=0.011) reduction in VTA/death, and a significant 52% (p=0.079) reduction in the risk of appropriate ICD shock therapy (Table 2). In contrast, among non-LBBB patients who had one or more RF, treatment with CRT-D was associated with a statistically significant 73% (p=0.025) increase in the risk of VTA; a 72% (p=0.014) increase in the composite endpoint of VTA/death; and a 91% (p=0.043) increase in the risk of appropriate defibrillator shock therapy (Table 2).