Objectives
To design a new echocardiographic method of screening for hypertrophic cardiomyopathy applicable to children and adults, with a low false positive rate in athletes.
Setting
Regional centre of cardiology, Oxford, UK.
Methods
Forty one patients with hypertrophic cardiomyopathy, 66 first degree relatives from families with familial hypertrophic cardiomyopathy, 262 normal subjects, and 32 athletes were studied by long axis M mode and cross sectional echocardiography to determine the frequency distribution of diastolic and systolic ratios of cardiac wall thickness to cavity diameter.
Results
The best screening measure for hypertrophic cardiomyopathy is diastolic septum to cavity ratio, where a value of > 0.26 yielded a 100% disease detection rate at all ages with 0% false positives in the ordinary population. In comparison, the conventional screening tool of diastolic septum to posterior left ventricular wall ratio of > 1.5 yielded a detection rate of only 75%, for a false positive rate of 2%. In first degree relatives, a septum to cavity ratio > 0.26 yielded a 100% detection rate for an abnormal phenotype suggestive of carriage of a mutation for hypertrophic cardiomyopathy with no obvious false positives. Conventional screening showed a detection rate of only 44%. Athletes with physiological cardiac hypertrophy showed only a 6% false positive rate with diastolic septum to cavity ratio, and could be differentiated from subjects with hypertrophic cardiomyopathy by the absence of hypercontractility shown by a normal systolic left ventricular wall to cavity ratio (cut off < 0.63; 0% false positives).
Conclusions
M mode echocardiographic measurement of the septum to cavity ratio provides a good screening test for hypertrophic cardiomyopathy at all ages. Combining this measurement with systolic left ventricular wall to cavity ratio improves the accuracy further.
