Journal
CIRCULATION
Volume 102, Issue 12, Pages 1346-1350Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/01.CIR.102.12.1346
Keywords
cardiomyopathy; hypertrophy; genetics; echocardiography; imaging
Funding
- NHLBI NIH HHS [P50 HL054313, P50 HL054313-080012, P50 HL054313-090012, P50 HL054313-100012, P50 HL054313-070012, P50-HL42267-01, P50 HL054313-08S10012, P50 HL054313-060012] Funding Source: Medline
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Background-Hypertrophic cardiomyopathy (HCM) is diagnosed clinically by the presence of left ventricular hypertrophy (LVH). However, LVH is absent in a significant number of genotype-positive patients. Because myocyte dysfunction and disarray are the primary abnormalities in HCM, we reasoned that tissue Doppler imaging could identify contraction and relaxation abnormalities, irrespective of hypertrophy, in a transgenic rabbit model of human HCM. Methods and Results-M-mode, 2D, Doppler echocardiography and tissue Doppler imaging were performed in nontransgenic (n=24), wild-type beta-myosin heavy chain-arginine(403) (n=14), and mutant beta-myosin heavy chain-glutamic acid(403) (n=24) transgenic rabbits. Mean septal thicknesses were 2.0+/-0.3, 2.0+/-0.25, and 2.75+/-0.3 mm in the 3 groups, respectively (P=0.001). LVH was absent in 9 of the 24 mutant rabbits. Left ventricular dimensions, systolic function, heart rate, mitral inflow velocities, and time intervals were similar in the groups. However, the difference between atrial reversal and transmitral A wave duration was increased in the mutant rabbits (P<0.001). More importantly, systolic and early diastolic tissue Doppler velocities were significantly lower in all mutant rabbits (7.45+/-2.2 versus 10.8+/-2.3 cm/s in nontransgenic and 9.0+/-0.76 cm/s in wild-type; P<0.001), including the 9 without LVH. A systolic velocity <8.5 cm/s had an 86% sensitivity and 100% specificity in identifying the mutant transgenic rabbits. Conclusions-Myocardial contraction and relaxation were reduced in the mutant beta-myosin heavy chain-glutamic acid(403) transgenic rabbit model of human HCM, irrespective of the presence or absence of LVH. In addition, tissue Doppler imaging is more sensitive than conventional echocardiography for HCM screening.
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