Tissue Doppler Imaging of the Fetal Heart: In Utero Detection of Myocardial Alterations in a Dog Model of Dilated Cardiomyopathy
*V. Chetboul, C. Escriou, D.Tessier, J.-L. Thibault, J.-L. Pouchelon, S. Blot, G. Derumeaux
*U. de Cardiologie - E.N.V. d'Alfort
Maisons-Alfort Cédex, FR
Tissue Doppler imaging (TDI) is a recent ultrasound technique allowing quantification of regional myocardial function by measurement of myocardial velocities. In humans, TDI has been proved to be a more sensitive and specific technique than conventional echocardiography for detecting mild myocardial dysfunction both in diastole and systole. Golden Retriever Muscular Dystrophy (GRMD) is related to a spontaneous X-linked mutation of dystrophin gene. GRMD cardiomyopathy is characterized by myocardial necrosis, mineralization and fibrosis, leading to late progressive left ventricular dysfunction. The aim of this study was to evaluate the accuracy of TDI to detect in utero GRMD myocardial dysfunction.
14 fetuses of normal Labrador Retriever females (control group) and 16 fetuses of GRMD carrier females (GRMD group) were examined both by conventional echocardiography and TDI using a Sequoia system (Siemens Acuson) equipped with a 7 MHz phased-array transducer. Left ventricular end-diastolic and end-systolic diameters were measured, then ejection fraction was calculated. TDI parameters, including endocardial and epicardial systolic velocities and subsequent myocardial velocity gradient (MVG), were determined within posterior wall using a left ventricular short-axis view. Conventional echo and TDI data were analyzed using a t-student test without knowledge of the genotype determined by PCR after fetal blood punction under echo control. A p value < 0.05 was considered as statistically significant.
No significant difference between control and GRMD fetal groups was observed on conventional echographic parameters. The control group of 14 fetuses demonstrated very homogeneous systolic MVG values (mean MVG: 1.2±0.1s-1). In GRMD group, using PCR diagnosis, 2 normal fetuses, 7 carrier females and 7 fetuses with mutant dystrophin gene were identified. Normal fetuses had comparable systolic MVG as controls (1.15±0.07s-1). Conversely, carrier females and fetuses with proven X-linked muscular dystrophy had lower systolic MVG than controls (0.8±0.4 and 0.6±0.2, respectively; p< 0.001), despite normal left ventricular dimension and function.
These results show that TDI accurately identifies in utero both the dystrophin mutant and the GRMD heterozygous fetuses. So, TDI is more sensitive than conventional echocardiography in assessing in utero subtle regional myocardial function abnormalities, and might be used as an accurate technique of antenatal screening for cardiomyopathies.