RESUMEN
The use of cardiovascular magnetic resonance imaging left atrial late gadolinium enhancement (LA LGE) is increasing for fibrosis evaluation though the use is still limited to specialized centres due to complex image acquisition and lack of consensus on image analyses. Analysis of LA LGE with image intensity ratio (IIR) (pixel intensity of atrial wall normalized by blood pool intensity) provides an objective method to obtain quantitative data on atrial fibrosis. A threshold between healthy myocardium and fibrosis of 1.2 has previously been established in 3T scans. The aim of the study was to reaffirm this threshold in 1.5T scans. LA LGE was performed using a 1.5T magnetic resonance scanner on: 11 lone-AF patients, 11 age-matched healthy volunteers (aged 27-44) and 11 elderly patients without known history of AF but varying degrees of comorbidities. Mean values of IIR for all healthy volunteers +2SD were set as upper limit of normality and was reproduced to 1.21 and the original IIR-threshold of 1.20 was maintained. The degree of fibrosis in lone-AF patients [median 9.0% (IQR 3.9-12.0)] was higher than in healthy volunteers [2.8% (1.3-8.3)] and even higher in elderly non-AF [20.1% (10.2-35.8), p = 0.001]. The previously established IIR-threshold of 1.2 was reaffirmed in 1.5T LA LGE scans. Patients with lone AF presented with increased degrees of atrial fibrosis compared to healthy volunteers in the same age-range. Elderly patients with no history of AF showed significantly higher degrees of fibrosis compared to both groups with younger individuals.
Asunto(s)
Fibrilación Atrial/diagnóstico por imagen , Función del Atrio Izquierdo , Remodelación Atrial , Medios de Contraste/administración & dosificación , Atrios Cardíacos/diagnóstico por imagen , Imagen por Resonancia Cinemagnética , Compuestos Organometálicos/administración & dosificación , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Fibrilación Atrial/fisiopatología , Estudios de Casos y Controles , Femenino , Fibrosis , Atrios Cardíacos/fisiopatología , Humanos , Masculino , Valor Predictivo de las PruebasRESUMEN
BACKGROUND: The measurement of late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) intensity in arbitrary units limits the objectivity of thresholds for focal scar detection and interpatient comparisons of scar burden. OBJECTIVE: To develop and validate a normalized measure, the image intensity ratio (IIR), for the assessment of left atrial (LA) scar on LGE-MRI. METHODS: Electrocardiogram- and respiratory-gated 1.5 Tesla LGE-MRI was performed in 75 patients (75% men; 62 ± 8 years) before atrial fibrillation ablation. The local IIR was defined as LA myocardial signal intensity for each of the 20 sectors on contiguous axial image planes divided by the mean LA blood pool image intensity. Intracardiac point-by-point sampled electroanatomic map points were coregistered with the corresponding image sectors. RESULTS: The average bipolar voltage for all 8153 electroanatomic map points was 0.9 ± 1.1 mV. In a mixed effects model accounting for within patient clustering, and adjusting for age, LA volume, mass, body mass index, sex, CHA2DS2-VASc score, atrial fibrillation type, history of previous ablations, and contrast delay time, each unit increase in local IIR was associated with 91.3% decrease in bipolar LA voltage (P < .001). Local IIR thresholds of >0.97 and >1.61 corresponded to bipolar voltage <0.5 and <0.1 mV, respectively. CONCLUSIONS: Normalization of LGE-MRI intensity by the mean blood pool intensity results in a metric that is closely associated with intracardiac voltage as a surrogate of atrial fibrosis.