Myocardial Extracellular Volume Fraction Adds Prognostic Information Beyond Myocardial Replacement Fibrosis.

BACKGROUND: Cardiac magnetic resonance techniques permit quantification of the myocardial extracellular volume fraction (ECV), representing a surrogate marker of reactive interstitial fibrosis, and late gadolinium enhancement (LGE), representing replacement fibrosis or scar. ECV and LGE have been independently linked with heart failure (HF) events. In deriving ECV, coronary artery disease type LGE, but not non-coronary artery disease type LGE, has been consistently excluded. We examined the associations between LGE, global ECV derived from myocardial tissue segments free of any detectable scar, and subsequent HF events. METHODS: Mid short-axis T1 maps were divided into 6 cardiac segments, each classified as LGE absent or present. Global ECV was derived from only segments without LGE. ECV was considered elevated if >30%, the upper 95% bounds of a reference group without known cardiac disease (n=28). Patients were divided into 4 groups by presence of elevated ECV and of any LGE. Subsequent HF hospitalization and any death were ascertained. Their relationship with ECV was examined separately and as a composite with Cox proportional hazard models. RESULTS: Of 1604 serial patients with T1 maps, 1255 were eligible after exclusions and followed over a median 26.3 (interquartile range, 15.9-37.5) months. Patients with elevated ECV had increased risk for death (hazard ratio [HR] 2.45 [95% CI, 1.76-3.41]), HF hospitalization (HR, 2.45 [95% CI, 1.77-3.40]), and a combined end point of both outcomes (HR, 2.46 [95% CI, 1.94-3.14]). After adjustments for covariates including LGE, the relationship persisted for death (HR, 1.82 [95% CI, 1.28-2.59]), hospitalization (HR, 1.60 [95% CI, 1.12-2.27]), and combined end points (HR, 1.73 [95% CI, 1.34-2.24]). CONCLUSIONS: ECV measures of diffuse myocardial fibrosis were associated with HF outcomes, despite exclusion of replacement fibrosis segments from their derivation and even among patients without any scar. ECV may have a synergistic role with LGE in HF risk assessment.

Is there a need to assess myocardial viability in patients presenting with heart failure?

PURPOSE OF REVIEW: Cardiac MRI is unique amongst the cardiac imaging modalities in its ability to directly image myocardial fibrosis using late gadolinium enhancement techniques. The ability to identify not only the presence of fibrosis but also its pattern of distribution within the myocardium can aid in distinguishing between ischemic and nonischemic causes of left ventricular dysfunction, as well as provide valuable prognostic information for patients with various etiologies of heart failure. RECENT FINDINGS: Amongst patients with ischemic cardiomyopathy, the Surgical Treatment for Ischemic Heart Failure (STICH) trial was attempted to assess the value of coronary artery bypass surgery. Although the early results were disappointing as to the overall utility of surgical revascularization, the recently published 10-year follow-up now demonstrates improved survival amongst patients undergoing surgical revascularization when compared with medical therapy alone. Although a substudy of STICH failed to demonstrate utility of preprocedural viability assessment with dobutamine echocardiography or single-photon-emission computed tomography, other studies support the identification of myocardial fibrosis as carrying important prognostic information. The ongoing development of new techniques, particularly T1 mapping of extracellular volume fraction, holds promise for the future as early studies suggest complementary prognostic value and perhaps the ability to avoid contrast administration. SUMMARY: Cardiac MRI use for viability assessment demonstrates important utility amongst patients with heart failure, regardless of its cause.

Association of Left Ventricular Diastolic Dysfunction with Subclinical Coronary Atherosclerotic Disease Burden Using Coronary Artery Calcium Scoring.

AIM: Diastolic dysfunction is a common problem in patients with obesity, hypertension, diabetes, or coronary artery disease. The purpose of this study was to evaluate the association of left ventricular diastolic dysfunction with an abnormal coronary artery calcium score (CAC score). METHODS: This study considered a cohort of patients ≥ 18 years of age with normal ejection fraction who were admitted to the hospital with chest pain. All patients underwent regadenoson myocardial perfusion stress imaging and had no evidence of ischemia or infarction. Patients then underwent cardiac CT for measurement of CAC score. Patients were excluded if they had prior history of coronary artery disease, ECG findings diagnostic of an acute coronary syndrome, an elevated troponin level, or hemodynamic instability. RESULTS: A total of 114 patients were included and 52 (45.6%) patients had echocardiographic evidence of diastolic dysfunction. Patients with diastolic dysfunction were more likely to have an abnormal calcium score (79.6% vs 20%; OR 15.10, 95% CI 5.70 to 43.85; p ＜ 0.001). In multivariable analysis, the presence of diastolic dysfunction on echocardiogram was significantly associated with an abnormal calcium score (OR 13.82, 95% CI 5.57 to 37.37; p ＜ 0.001) after adjusting for Framingham Risk Score or clinical risk factors (age, gender, diabetes mellitus, dyslipidemia, and obesity; OR 19.06,95% CI 4.66 to 107.97; p ＜ 0.001). CONCLUSIONS: Our study demonstrates that left ventricular diastolic dysfunction is associated with an abnormal CAC score even after adjusting for Framingham Risk Score or clinical risk factors. Patients without known coronary artery disease that present with chest pain and have normal perfusion imaging with evidence of abnormal diastolic function on echocardiogram may warrant more thorough evaluation for coronary atherosclerotic disease with CAC score assessment.