Multi-Modality Imaging in Dilated Cardiomyopathy: With a Focus on the Role of Cardiac Magnetic Resonance

Risk stratification of patients with nonischemic dilated cardiomyopathy is primarily based on left ventricular ejection fraction (LVEF). Superior prognostic factors may improve patient selection for implantable cardioverter-defibrillators (ICDs) and other management decisions. To determine whether myocardial fibrosis (detected by late gadolinium enhancement cardiovascular magnetic resonance [LGE-CMR] imaging) is an independent and incremental predictor of mortality and sudden cardiac death (SCD) in dilated cardiomyopathy. Prospective, longitudinal study of 472 patients with dilated cardiomyopathy referred to a UK center for CMR imaging between November 2000 and December 2008 after presence and extent of midwall replacement fibrosis were determined. Patients were followed up through December 2011. Primary end point was all-cause mortality. Secondary end points included cardiovascular mortality or cardiac transplantation; an arrhythmic composite of SCD or aborted SCD (appropriate ICD shock, nonfatal ventricular fibrillation, or sustained ventricular tachycardia); and a composite of HF death, HF hospitalization, or cardiac transplantation. Among the 142 patients with midwall fibrosis, there were 38 deaths (26.8%) vs 35 deaths (10.6%) among the 330 patients without fibrosis (hazard ratio [HR], 2.96 [95% CI, 1.87-4.69]; absolute risk difference, 16.2% [95% CI, 8.2%-24.2%]; P < .001) during a median follow-up of 5.3 years (2557 patient-years of follow-up). The arrhythmic composite was reached by 42 patients with fibrosis (29.6%) and 23 patients without fibrosis (7.0%) (HR, 5.24 [95% CI, 3.15-8.72]; absolute risk difference, 22.6% [95% CI, 14.6%-30.6%]; P < .001). After adjustment for LVEF and other conventional prognostic factors, both the presence of fibrosis (HR, 2.43 [95% CI, 1.50-3.92]; P < .001) and the extent (HR, 1.11 [95% CI, 1.06-1.16]; P < .001) were independently and incrementally associated with all-cause mortality. Fibrosis was also independently associated with cardiovascular mortality or cardiac transplantation (by fibrosis presence: HR, 3.22 [95% CI, 1.95-5.31], P < .001; and by fibrosis extent: HR, 1.15 [95% CI, 1.10-1.20], P < .001), SCD or aborted SCD (by fibrosis presence: HR, 4.61 [95% CI, 2.75-7.74], P < .001; and by fibrosis extent: HR, 1.10 [95% CI, 1.05-1.16], P < .001), and the HF composite (by fibrosis presence: HR, 1.62 [95% CI, 1.00-2.61], P = .049; and by fibrosis extent: HR, 1.08 [95% CI, 1.04-1.13], P < .001). Addition of fibrosis to LVEF significantly improved risk reclassification for all-cause mortality and the SCD composite (net reclassification improvement: 0.26 [95% CI, 0.11-0.41]; P = .001 and 0.29 [95% CI, 0.11-0.48]; P = .002, respectively). Assessment of midwall fibrosis with LGE-CMR imaging provided independent prognostic information beyond LVEF in patients with nonischemic dilated cardiomyopathy. The role of LGE-CMR in the risk stratification of dilated cardiomyopathy requires further investigation.

We studied the prognostic implications of midwall fibrosis in dilated cardiomyopathy (DCM) in a prospective longitudinal study. Risk stratification of patients with nonischemic DCM in the era of device implantation is problematic. Approximately 30% of patients with DCM have midwall fibrosis as detected by late gadolinium-enhancement (LGE) cardiovascular magnetic resonance (CMR), which may increase susceptibility to arrhythmia and progression of heart failure. Consecutive DCM patients (n = 101) with the presence or absence of midwall fibrosis were followed up prospectively for 658 +/- 355 days for events. Midwall fibrosis was present in 35% of patients and was associated with a higher rate of the predefined primary combined end point of all-cause death and hospitalization for a cardiovascular event (hazard ratio 3.4, p = 0.01). Multivariate analysis showed midwall fibrosis as the sole significant predictor of death or hospitalization. However, there was no significant difference in all-cause mortality between the 2 groups. Midwall fibrosis also predicted secondary outcome measures of sudden cardiac death (SCD) or ventricular tachycardia (VT) (hazard ratio 5.2, p = 0.03). Midwall fibrosis remained predictive of SCD/VT after correction for baseline differences in left ventricular ejection fraction between the 2 groups. In DCM, midwall fibrosis determined by CMR is a predictor of the combined end point of all-cause mortality and cardiovascular hospitalization, which is independent of ventricular remodeling. In addition, midwall fibrosis by CMR predicts SCD/VT. This suggests a potential role for CMR in the risk stratification of patients with DCM, which may have value in determining the need for device therapy.

Left ventricular (LV) ejection fraction (LVEF) is a simple measure of global systolic function that pervades the risk evaluation and management of many cardiovascular diseases. However, this parameter is limited not only by technical challenges, but also by pathophysiological entities where the ratio of stroke volume to LV cavity size is preserved. The assessment of global longitudinal strain (GLS) from speckle-tracking analysis of 2-dimensional echocardiography has become a clinically feasible alternative to LVEF for the measurement of myocardial function. Evidence gathered over the last decade has shown GLS to be more sensitive to left ventricular dysfunction (LVD) than LVEF and to provide additional prognostic information. The technology is validated, reproducible within an acceptable range, and widely available. GLS has been proposed as the test of choice in guidelines for monitoring of asymptomatic cardiotoxicity related to chemotherapy. It also has the potential to improve risk stratification, redefine criteria for disease classification, and determine treatment in asymptomatic LVD resulting from a variety of etiologies. GLS provides utility across the spectrum of heart failure (and LVEF) as well as in the evaluation of valvular heart disease. There is a strong case for incorporation of GLS into clinical decision making. This review appraises the evidence addressing the utility of GLS as a complementary metric to LVEF for incorporation into mainstream clinical practice.