Extracellular Volume and Global Longitudinal Strain Both Associate With Outcomes But Correlate Minimally.

ABSTRACT

OBJECTIVES: This study examined how extracellular volume (ECV) and global longitudinal strain (GLS) relate to each other and to outcomes. BACKGROUND: Among myriad changes occurring in diseased myocardium, left ventricular imaging metrics of either the interstitium (e.g., ECV) or contractile function (e.g., GLS) may consistently associate with adverse outcomes yet correlate minimally with each other. This scenario suggests that ECV and GLS potentially represent distinct domains of cardiac vulnerability. METHODS: The study included 1,578 patients referred for cardiovascular magnetic resonance (CMR) without amyloidosis, and it quantified how ECV associated with GLS in linear regression models. ECV and GLS were then compared in their associations with incident outcomes (death and hospitalization for heart failure). RESULTS: ECV and GLS correlated minimally (R2 = 0.04). Over a median follow-up of 5.6 years, 339 patients experienced adverse events (149 hospitalizations for heart failure, 253 deaths, and 63 with both). GLS (univariable hazard ratio 2.07 per 5% increment; 95% CI 1.86 to 2.29) and ECV (univariable hazard ratio 1.66 per 4% increment; 95% CI 1.51 to 1.82) were principal variables associating with outcomes in univariable and multivariable Cox regression models. Similar results were observed in several clinically important subgroups. In the whole cohort, ECV added prognostic value beyond GLS in univariable and multivariable Cox regression models. CONCLUSIONS: GLS and ECV may represent principal but distinct domains of cardiac vulnerability, perhaps reflecting their distinct cellular origins. Whether combining ECV and GLS may advance pathophysiological understanding for a given patient, optimize risk stratification, and foster personalized medicine by targeted therapeutics requires further investigation.