European Heart Journal Advance Access originally published online on February 28, 2008
European Heart Journal 2008 29(7):949; doi:10.1093/eurheartj/ehn034
Normal systolic function in hypertrophic cardiomyopathy: reality or myth?: reply
Pediatric Cardiology
University Hospitals Leuven
Leuven
Belgium
Lillie Frank Abercrombie Section of Pediatric
Cardiology
Texas Children's Hospital
Baylor College of Medicine 6621
Fannin TX 77030
Houston
USA
Email: cardop{at}bcm.tmc.edu
We would like to thank Efthimiadis et al. for their interest in our work. Indeed, it was long believed that patients with hypertrophic cardiomyopathy (HCM) had normal or supranormal systolic function despite mutations in genes encoding for sarcomeric proteins. This concept was, at least partly, based on the use of endocardial indices of systolic function such as ejection fraction. Ejection fraction is generally normal or supranormal in HCM patients. However, it is well known that ejection fraction is a poor surrogate for systolic function in the presence of left ventricular hypertrophy because a normal ejection fraction is maintained by the subnormal function of additional sarcomeres laid in parallel. Reduced shortening of extra parallel sarcomeres leads to the same thickening and ejection of blood as would normal shortening of fewer sarcomeres.1 Experimental data started to separate reality from myth by showing that there is myocardial dysfunction even before the development of left ventricular hypertrophy.2 Whether this is detectable in the in vivo heart remains a difficult task. Follow up studies looking at young subjects with mutations before the development of hypertrophy may give the answer to this elusive question.
We concur that isolated systolic or diastolic dysfunction do not exist. One is coupled to the other. Studies have confirmed that parameters of systolic function are important determinants of early diastolic function.3 The sensitivity of the techniques used to assess function seems to play a crucial role in detecting subtle abnormalities.4 Interestingly, in our study, patients with HCM had myocardial shortening and thickening persisting well after aortic valve closure in the more hypertrophied basal septal myocardial segments. This was associated with reduced early diastolic myocardial velocity in those myocardial segments suggesting abnormal myocardial relaxation.
The reduction in systolic myocardial deformation was associated not only with maximal end-diastolic wall thickness and decreased exercise capacity but also with a blunted blood pressure response with exercise (r = 0.62, P < 0.01). Given a blunted blood pressure response is a predictor of poor outcome in patients with HCM; this finding suggests that the abnormalities in myocardial deformation may be used to predict exercise capacity and may help risk stratify patients with HCM.
Certainly, non-invasive techniques have helped us uncover some secrets of the hypertrophic heart. We hope that future studies will tell us more about when, how, and why hypertrophy as well as myocardial dysfunction ensue in HCM.
References
- Carabello BA. Evolution of the study of left ventricular function: everything old is new again. Circulation (2002) 105:2701–2703.
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- Courtois M, Mechem CJ, Barzilai B, Ludbrook PA. Factors related to end-systolic volume are important determinants of peak early diastolic transmitral flow velocity. Circulation (1992) 85:1132–1138.
[Abstract/Free Full Text] - Yu CM, Lin H, Yang H, Kong SL, Zhang Q, Lee SW. Progression of systolic abnormalities in patients with "isolated" diastolic heart failure and diastolic dysfunction. Circulation (2002) 105:1195–1201.
[Abstract/Free Full Text]
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