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Echocardiographic wall-to-cavity ratios in hypertrophic cardiomyopathy and other types of cardiac hypertrophy

Devlin, Anita May; (2001) Echocardiographic wall-to-cavity ratios in hypertrophic cardiomyopathy and other types of cardiac hypertrophy. Doctoral thesis (M.D), UCL (University College London). Green open access

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Abstract

Background - Left ventricular (LV) hypertrophy is diagnosed by increased LV wall thickness or increased LV mass. A single cut-off for echocardiographic wail thickness (>15mm in adults) is commonly used irrespective of gender. This approach has yielded an inexplicable excess in male prevalence of 2-3:1 for hypertrophic cardiomyopathy (HCM) in population based studies. Children's cardiac measurements are referenced to body surface area by nomograms or regression equations which take no account of LV cavity size. LV mass or mass index is a continuous variable in the normal population with no absolute diagnostic cut-off for hypertrophy, whilst published normal values can be seen in hypertrophic cardiomyopathy. Consequently, a need exists for a simpler echocardiographic method to diagnose and sequentially monitor LV hypertrophy at all ages irrespective of gender, which may also help to differentiate between aetiologies. Objectives - To describe a new echocardiographic method for assessing LV hypertrophy which is applicable at all ages and is independent of gender. Methods - 262 normal subjects, 41 patients with hypertrophic cardiomyopathy, 52 first degree relatives from families with familial hypertrophic cardiomyopathy, 26 athletes and 16 patients with hypertension underwent echocardiography. M-mode diastolic and systolic ratios of LV wall thickness to LV diameter were calculated. A subset of 10 patients with HCM had LV wall thickness and mass measurements performed using magnetic resonance imaging (MRI) for comparison with echocardiography. Results - Diastolic and systolic wall-to-cavity ratios show little variation with age and are independent of gender. In adults diastolic ratios are independent of body surface area. A septum-to-cavity ratio of >0.26 identified all HCM patients (100% sensitivity) and no control subjects (0% false positives). A systolic LV wall-to-cavity ratio of > 0.63 performed equally well in subjects > 1 year, Septum-to-posterior wall thickness ratio >1.3 performed less well (90% sensitivity, 10% false positive rate). A septum-to-cavity ratio >0.26 identified all first-degree relatives with an abnormal phenotype suggestive of gene carriage with no obvious false positives. It was also more successful than traditional measures at dividing relatives in to affected and unaffected subjects in the proportions expected for autosomal dominant inheritance. Athletes with marked cardiac hypertrophy showed a 7.7% false positive rate for the diagnosis of HCM using diastolic septum-to-cavity ratio >0.26, but are recognised as showing physiological hypertrophy by the presence of normal systolic function (systolic LV wall-to-cavity ratios). Hypertensive cardiac hypertrophy is also identified by a septum-to-cavity ratio > 0.26. Systolic LV wall-to-cavity ratios are significantly lower than in subjects with HCM as are other measures of systolic function. MRI and echocardiography show good agreement between LV wall thickness measurements, particularly of the anterior interventricular septum. The agreement between the assessments of LV mass was poor. Conclusions - Septum-to-cavity ratio and systolic LV wall-to-cavity ratio can diagnose LV hypertrophy at all ages, are useful in the diagnosis of and screening for HCM and can help differentiate physiological from pathological hypertrophy. MRI and echocardiography are complimentary techniques in the assessment of LV hypertrophy and any positive treatment effects.

Type: Thesis (Doctoral)
Qualification: M.D
Title: Echocardiographic wall-to-cavity ratios in hypertrophic cardiomyopathy and other types of cardiac hypertrophy
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Health and environmental sciences; Hypertrophic cardiomyopathy
URI: https://discovery.ucl.ac.uk/id/eprint/10105263
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