Tissue Doppler Imaging for Detection of Radial and Longitudinal Myocardial Dysfunction in a Family of Cats Affected by Dystrophin-Deficient Hypertrophic Muscular Dystrophy

Abstract

Diagnosis of feline hypertrophic cardiomyopathy currently is based on the presence of myocardial hypertrophy detected using conventional echocardiography. The accuracy of tissue Doppler imaging (TDI) for earlier detection of the disease has never been described. The objective of this sudy was to quantify left ventricular free wall (LVFW) velocities in cats with hypertrophic muscular dystrophy (HFMD) during preclinical cardiomyopathy using TDI. The study animals included 22 healthy controls and 7 cats belonging to a family of cats with HFMD (2 affected adult males, 2 heterozygous adult females, one 2.5-month-old affected male kitten, and 2 phenotypically normal female kittens from the same litter). All cats were examined via conventional echocardiography and 2-dimensional color TDI. No LVFW hypertrophy was detected in the 2 carriers or in the affected kitten when using conventional echocardiography and histologic examination, respectively. The LVFW also was normal for 1 affected male and at the upper limit of normal for the 2nd male. Conversely, LVFW dysfunction was detected in all affected and carrier cats with HFMD when using TDI. TDI consistently detects LVFW dysfunction in cats with HFMD despite the absence of myocardial hypertrophy. Therefore, TDI appears more sensitive than conventional echocardiography in detecting regional myocardial abnormalities.

Evaluation of Feline Cardiomyopathies

“…This observation, made during both spontaneous "classical" and dystrophic HCM, confirms the high sensitivity of tissue Doppler imaging (TDI) in the diagnosis of regional myocardial dysfunction as well as its importance in early HCM screening [31,32].…”

“…They include [29][30][31][32][33] • Reduced early diastolic endoepicardial and left ventricular free wall base-apex gradients • Increased end-diastolic endoepicardial and left ventricular free wall base-apex gradients • Increased radial and especially longitudinal IVRT In Maine Coon cats, heterozygous for the MyBPC3 mutation but free of LV hypertrophy, a significant decrease in E DTI /A DTI was demonstrated in the longitudinal movement of the basal interventricular septum (in comparison to wild homozygous animals).…”

Prevalence of the MYBPC3-A31P mutation in a large European feline population and association with hypertrophic cardiomyopathy in the Maine Coon breed

“…These data suggest that unaffected mutated cats, in particular, need to be followed up to determine whether and when HCM occurs or when the first tissue Doppler imaging signs appear in asymptomatic cats. 16,21,22 In humans, symptoms of HCM are heterogeneous even when mutations occur in the same gene. 23 Mutations in MYBPC3 lead mainly to truncation of the protein which gives a relatively mild phenotype, but mutations in MYBPC3 are also correlated with severe phenotypes.…”

Myocardial Tissue Doppler, Derived Techniques, and Speckle Tracking Imaging

“…Early radial and longitudinal systolic and diastolic TDI alterations were then demonstrated with this same model in color 2D TDI mode [37]. A greater TDI sensitivity to detect myocardial injury early was then demonstrated in cats with a similar model of hypertrophic cardiomyopathy (linked to a dystrophin coding gene mutation) [38], in cases of spontaneous hypertrophic cardiomyopathy in cats of various breeds and in Maine Coons [39,40], and in the presence of systemic hypertension [39]. TDI was also shown to be more sensitive than the ultrasound exam and conventional Doppler in the diagnosis of systolic pulmonary hypertension in dogs [41].…”