Assessment of Myocardial Scarring Improves Risk Stratification in Patients Evaluated for Cardiac Defibrillator Implantation

Abstract

Objectives We tested whether an assessment of myocardial scarring by cardiac magnetic resonance (CMR) would improve risk stratification in patients evaluated for implantable cardioverter-defibrillator implantation. Background Current SCD risk stratification emphasizes left-ventricular ejection fraction (LVEF), however the majority of patients suffering SCD have a preserved LVEF and many with poor LVEF do not benefit from ICD prophylaxis. Methods One hundred thirty-seven patients undergoing evaluation for possible ICD placement were prospectively enrolled and underwent CMR assessment of LVEF and scar. The prespecified primary endpoint was death or appropriate ICD discharge for sustained ventricular tachyarrhythmia. Results During a median follow-up of 24 months the primary endpoint occurred in 39 patients. Whereas the rate of adverse events steadily increased with decreasing LVEF, a sharp step-up was observed for scar size >5% of LV mass (HR=5.2 [95% CI, 2.0-13.3]). On multivariable Cox proportional hazards analysis, including LVEF and electrophysiological-study results, scar size (as a continuous variable or dichotomized at 5%) was an independent predictor of adverse outcome. Among patients with LVEF >30%, those with significant scarring (>5%) had higher risk than those with minimal-or-no (≤5%) scarring (HR=6.3 [1.4-28.0]). Those with LVEF >30% and significant scarring had similar risk to patients with LVEF ≤30% (p=0.56). Among patients with LVEF ≤30%, those with significant scarring again had higher risk than those with minimal-or-no scarring (HR=3.9 [1.2-13.1]). Those with LVEF ≤30% and minimal scarring had similar risk to patients with LVEF >30% (p=0.71). Conclusions Myocardial scarring detected by CMR is an independent predictor of adverse outcome in patients being considered for ICD placement. In patients with LVEF >30%, significant scarring (>5% LV) identifies a high-risk cohort similar in risk to those with LVEF ≤30%. Conversely, in patients with LVEF ≤30%, minimal-or-no scarring identifies a low-risk cohort similar to those with LVEF >30%.

Late Gadolinium Enhancement and the Risk for Ventricular Arrhythmias or Sudden Death in Dilated Cardiomyopathy

“…The majority of studies evaluated the presence or absence of LGE by visual analysis. 4,6,7,10,[13][14][15][16][17][18][19][20]22,[24][25][26][27][28][29]30,32 Duration of follow-up ranged from 1 year to 5.3 years; mean follow up was 3 years. The majority of reports considered a composite arrhythmic end-point formed by sudden cardiac death and/or aborted cardiac arrest, sustained ventricular arrhythmias and/or appropriate ICD therapies.…”

“…The majority of reports considered a composite arrhythmic end-point formed by sudden cardiac death and/or aborted cardiac arrest, sustained ventricular arrhythmias and/or appropriate ICD therapies. 4,5,7,8,10,13,14,[16][17][18]20,22,25,[28][29][30][31] In two reports history of arrhythmic events was the end-point analyzed. 9,32 These data were not used to calculate annual event rates, but were included in the evaluation of pooled OR.…”

Myocardial Damage Detected by Late Gadolinium Enhancement Cardiac Magnetic Resonance Is Uncommon in Peripartum Cardiomyopathy

“…CMR has emerged as an important tool to identify the etiology of nonischemic cardiomyopathies,27 and predict risk of adverse outcomes based on the extent of LGE 4, 8, 10, 14, 15, 27. LGE can detect foci of myocardial damage as small as 0.7 g of myocardial tissue 28.…”

“…Since LGE indicates irreversible focal myocardial damage, even when ejection fraction is preserved,8, 9, 10 the overall low prevalence of LGE in this study represents an optimistic finding. Indeed, the CMR literature consistently indicates that LGE is associated with persistent myocardial dysfunction despite medical therapy,11, 12 arrhythmia,4, 13, 14 and in turn, adverse clinical events such as hospitalization for heart failure, arrhythmia, and mortality 4, 8, 10, 14, 15. In the setting of severe heart failure from PPCM, the low prevalence of LGE might inform decision making when contemplating advanced heart failure therapies such as mechanical circulatory support as a bridge to recovery and heart transplantation.…”

“…While LGE can occur even when ejection fraction is preserved,8, 9, 10 LGE is generally associated with persistent myocardial dysfunction despite medical therapy,11, 12 arrhythmia,4, 13, 14 and in turn, hospitalization for heart failure, arrhythmia, and mortality 4, 8, 10, 14, 15. Regardless of etiology, LGE is prognostically adverse across the spectrum of left ventricular ejection fraction (LVEF), even when preserved 4, 8, 9, 10.…”