LGE-CMR positivity associates with higher sudden cardiac death risk in ICD and CRT candidates

This systematic review and meta-analysis investigated the association between late gadolinium enhancement (LGE) assessed by cardiovascular magnetic resonance (CMR) and the risk of sudden cardiac death (SCD). The study population comprised 2,494 patients who were selected for the implantation of an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT). The specific setting of the studies included in this meta-analysis was not reported. The primary exposure was LGE-CMR positivity, which was compared against LGE-CMR negativity. The primary outcome of interest was the occurrence of sudden cardiac death.

The meta-analysis reported that patients with LGE-CMR positivity faced a 72% higher risk of SCD compared to those with LGE-CMR negativity. The hazard ratio (HR) for this association was 1.72, with a 95% confidence interval (CI) of 1.18 to 2.50. When the analysis was restricted to patients with non-ischemic cardiomyopathy, the association remained significant, with an HR of 2.42 and a 95% CI of 1.99 to 2.94. In contrast, the analysis of patients selected for CRT-only implantation showed no statistically significant difference in SCD risk between LGE-positive and LGE-negative groups. The HR for this subgroup was 1.17, with a 95% CI of 0.82 to 1.68.

Further analysis compared SCD risk based on the duration of follow-up in the included articles. The results indicated comparable SCD risk between short-term and long-term follow-up periods. The odds ratio (OR) for short-term follow-up was 7.47 (95% CI 0.54 to 103.12), while the OR for long-term follow-up was 6.15 (95% CI 0.96 to 39.45). The wide confidence intervals in these subgroup analyses suggest considerable uncertainty in the estimates derived from these specific comparisons. No secondary outcomes were reported in the available data.

Safety and tolerability findings were not reported in the source data for this meta-analysis. Consequently, adverse event rates, serious adverse events, discontinuations, and overall tolerability of the imaging protocol could not be assessed. The limitations of this study include the lack of reported funding or conflicts of interest. A key methodological limitation identified was that the difference in risk reduction between LGE-positive and LGE-negative patients was statistically not significant specifically in the CRT candidate subgroup. This finding highlights the heterogeneity of risk profiles within the CRT population.

The practice relevance of these findings suggests that LGE-CMR before device implantation could be crucial for identifying high-risk patients, even in cases of non-ischemic etiology. However, clinicians must interpret these results with caution, particularly regarding the lack of significance in the CRT-only cohort. The evidence indicates that LGE-CMR positivity was associated with an increased SCD risk, but the certainty of this association varies by patient subgroup. Questions remain unanswered regarding the optimal timing of LGE-CMR assessment and whether the imaging findings should alter management strategies for patients already selected for CRT. The wide confidence intervals in the follow-up comparisons also underscore the need for further research to clarify risk stratification in different clinical contexts.