This study evaluated the prevalence of left main or triple vessel CAD using a multicenter registry of comatose OHCA survivors and assessed their outcome based on the revascularization strategy. We found that left main or triple vessel CAD was seen in 25.3% of comatose OHCA patients and that the rate of neurologically intact survival at 1 month was 34.0%. Using crude and IPTW analysis suggested that compared with no immediate or incomplete revascularization, complete revascularization improves neurologically intact survival in OHCA patients with left main or triple vessel CAD. Also, the IPTW analysis showed that complete revascularization resulted in better 1-month survival compared with no immediate or incomplete revascularization.
Our study is the first to specifically report the role of revascularization strategy in resuscitated OHCA patients with multivessel CAD. Our findings are in contrast with those of a recent trial on patients with multivessel CAD and cardiogenic shock that showed a superior survival benefit of culprit-lesion-only PCI over immediate multivessel PCI (6, 7). This discrepancy in the results may be due to differences in the patient population, primary endpoint, and the revascularization strategy. OHCA patients with multivessel CAD tend to be refractory to resuscitative effort and have hemodynamic instability after the return of spontaneous circulation; consequently, such patients constitute a more complex and higher-risk group owing to the prolonged systemic ischemia/reperfusion damage, including hypoxic-ischemic brain injury and myocardial dysfunction (9, 10).
In our study, the overall rates of neurologically intact survival and survival at 1 month were 34.0% and 50.0%, respectively, which were worse than the ~ 60% short-term survival rate reported in recent trials on patients with OHCA or cardiogenic shock with multivessel CAD (5, 6). Only the complete revascularization group in our study showed a comparable 1-month survival rate of 62.5% and a neurologically intact survival rate of 53.1%. The complete revascularization strategy had a more favorable effect on neurologic outcomes than on survival. After early stabilization in OHCA survivors, the withdrawal of life-sustaining therapy owing to perceived unfavorable neurological prognosis is the leading cause of death in OHCA patients (16, 17), which suggests that neurologically intact survival should be considered as the primary therapeutic endpoint for comatose OHCA patients. A recent study suggested that the prolonged procedural duration and a higher dose of contrast materials outweigh the potential benefit of myocardial salvage in immediate multivessel PCI for patients with cardiogenic shock with multivessel CAD (6). Although we provided statistically unbiased results using IPTW analysis, it should be noted that the complete revascularization group in our study had a significantly less complex CAD in terms of disease extent and the presence of chronic total occlusion (18.8%), which implies that procedural duration and the amount of contrast material in the complete revascularization group might not have been significantly different from those in the no immediate or incomplete revascularization group. The left main-only CAD accounted for 12.5% of the complete revascularization group, and there was an overlap between the complete revascularization group and culprit-lesion-only PCI. Moreover, chronic total occlusion was the main obstacle for achieving complete revascularization. Owing to the observational nature of our study, we categorized the patients based on the results of the revascularization regardless of the recanalization attempts. However, these are only speculative because the specific data on the procedure progress records and the amount of contrast material were not obtained in this study. The possibility of unknown confounders affecting the decision of immediate CABG should be considered when interpreting our results.
Primary PCI strategy is recommended for OHCA patients with suspected cardiac causes (18, 19), but there are no specific guidelines for OHCA patients with CAD who are not amenable to PCI. Furthermore, recent guidelines recommend CABG over PCI for patients with stable left main CAD with high anatomical complexity or stable multivessel CAD with intermediate-to-high anatomical complexity (19, 20), but they do not suggest a specific type of revascularization for patients with left main or multivessel CAD with cardiogenic shock (4). The demanding and resource-intensive nature of CABG and a tendency for therapeutic nihilism in the comatose OHCA patients contribute to the low rates of CABG surgery as a revascularization strategy; consequently, the potential benefit of CABG remains unclear (4, 21). In our study, the revascularization strategy was based on the individual decision of the interventional cardiologists and cardiac surgeons. Among the 32 (21%) patients in the complete revascularization group, 5 (16%) OHCA patients with CAD not amenable to PCI received immediate CABG, and 4 of those patients showed neurologic recovery after the surgery. Due to the limited number of patients and unknown confounders, our results regarding the positive effect of immediate CABG for comatose OHCA patients with left main or triple vessel CAD should be regarded as hypothesis-generating and highlighting the need for further research. Our results suggest that for incomplete or no immediate revascularization strategy with an absolute risk reduction of 24% for a neurologically intact survival, the number needed to treat would be 4.2.
This study has several limitations. First, as this was an observational study, our results should be considered as showing an independent association between revascularization and neurologically intact survival and not a causal relationship thereof. Second, the technical and medical advances in cardiovascular and post-resuscitation care during the study period should be considered. Since the guidelines have been updated, subsequent interventions and treatment strategies should have been applied differently during the study period, which could have affected the clinical outcomes and acted as potential confounding factors. Third, the small sample size limits the internal and external validity of the study results, and our results were underpowered for detecting significant differences in the clinical outcomes between the no immediate group and the incomplete revascularization group. Larger studies are needed to conclusively confirm these findings. Moreover, post-resuscitation care for OHCA patients involves a complex series of clinical decisions and could have acted as a potential confounding factor. Lastly, although we adjusted for confounding clinical covariates using IPTW analysis, the intergroup differences may have been due to other unknown confounders.