Diagnosis of hypertrophic cardiomyopathy and screening for the phenotype suggestive of gene carriage in familial disease: a simple echocardiographic procedure

Abnormal cardiac formation in hypertrophic cardiomyopathy: fractal analysis of trabeculae and preclinical gene expression

BACKGROUND

Mutations in genes coding for sarcomeric proteins cause hypertrophic cardiomyopathy. Subtle abnormalities of the myocardium may be present in mutation carriers without left ventricular hypertrophy (G+LVH-) but are difficult to quantify. Fractal analysis has been used to define trabeculae in left ventricular noncompaction and to identify normal racial variations. We hypothesized that trabeculae measured by fractal analysis of cardiovascular magnetic resonance images are abnormal in G+LVH- patients, providing a preclinical marker of disease in hypertrophic cardiomyopathy.

METHODS AND RESULTS

Cardiovascular magnetic resonance was performed on 40 G+LVH- patients (33±15 years, 38% men), 67 patients with a clinical diagnosis of hypertrophic cardiomyopathy (53±15 years, 76% men; 31 with a pathogenic mutation [G+LVH+]), and 69 matched healthy volunteers (44±15 years, 57% men). Trabeculae were quantified by fractal analysis of cine slices to calculate the fractal dimension, a unitless index of endocardial complexity calculated from endocardial contours after segmentation. In G+LVH- patients, apical left ventricular trabeculation was increased compared with controls (maximal apical fractal dimension, 1.249±0.07 versus 1.199±0.05; P=0.001). In G+LVH+ and G-LVH+ cohorts, maximal apical fractal dimension was greater than in controls (P<0.0001) irrespective of gene status (G+LVH+: 1.370±0.08; G-LVH+: 1.380±0.09). Compared with controls, G+LVH- patients also had a higher frequency of clefts (28% versus 8%; P=0.02), longer anterior mitral valve leaflets (23.5±3.0 versus 19.7±3.1 mm; P<0.0001), greater septal systolic wall thickness (12.6±3.2 versus 11.2±2.1 mm; P=0.03), higher ejection fraction (71±4% versus 69±4%; P=0.03), and smaller end-systolic volumes (38±9 versus 43±12 mL; P=0.03).

CONCLUSIONS

Increased myocardial trabecular complexity is one of several preclinical abnormalities in hypertrophic cardiomyopathy sarcomere gene mutation carriers without LVH.

Sudden cardiac death in young athletes

Athletic activity is associated with an increased risk of sudden death for individuals with some congenital or acquired heart disorders. This review considers in particular the causes of death affecting athletes below 35 years of age. In this age group the largest proportion of deaths are caused by diseases with autosomal dominant inheritance such as hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, long QT-syndrome, and Marfan's syndrome. A policy of early cascade-screening of all first-degree relatives of patients with these disorders will therefore detect a substantial number of individuals at risk. A strictly regulated system with preparticipation screening of all athletes following a protocol pioneered in Italy, including school-age children, can also detect cases caused by sporadic new mutations and has been shown to reduce excess mortality among athletes substantially. Recommendations for screening procedure are reviewed. It is concluded that ECG screening ought to be part of preparticipation screening, but using criteria that do not cause too many false positives among athletes. One such suggested protocol will show positive in approximately 5% of screened individuals, among whom many will be screened for these diseases. On this point further research is needed to define what kind of false-positive and false-negative rate these new criteria result in. A less formal system based on cascade-screening of relatives, education of coaches about suspicious symptoms, and preparticipation questionnaires used by athletic clubs, has been associated over time with a sizeable reduction in sudden cardiac deaths among Swedish athletes, and thus appears to be worth implementing even for junior athletes not recommended for formal preparticipation screening. It is strongly argued that in families with autosomal dominant disorders the first screening of children should be carried out no later than 6 to 7 years of age.

Echocardiographic and electrocardiographic identification of those children with hypertrophic cardiomyopathy who should be considered at high-risk of dying suddenly

BACKGROUND

Hypertrophic cardiomyopathy is a common cause of sudden death in children. In this study, we aimed to identify clinical measures for stratification of this risk in childhood.

PATIENTS AND METHODS

By means of a retrospective cohort study from six regional centres of paediatric cardiology, we identified 128 patients with hypertrophic cardiomyopathy presenting below 19 years of age, with a mean follow-up of 10.8 years. Of the patients, 31 had died, 16 suddenly, with a median age at sudden death of 13.3 years.

RESULTS

Cox regression shows that electrocardiographic voltages, analysed as the sum of the R and S waves in all six limb leads (p equal to 0.001), and septal thickness expressed as proportion of the 95th centile for age (p equal to 0.036), were independent predictors of sudden death. When the sum of the R and S waves is over 10 millivolts, the odds ratio for sudden death was 8.4, with 95% confidence intervals from 2.2 to 33.7 (p equal to 0.0012), and finding a septal thickness over 190% of 95th centile for age gives an odds ratio of 6.2, with confidence intervals from 1.5 to 25.1 (p equal to 0.011). Noonan's syndrome, with a p value equal to 0.043, and the ratio of the left ventricular wall to its cavity in diastole, with a p value equal to 0.005, were independent predictors of death in cardiac failure, with a ratio of the mural thickness to the dimension of the cavity over 0.30 giving an odds ratio of 36.0, with confidence limits from 4.2 to 311, and a p value equal to 0.00009. At follow-up, patients deemed to be at a high risk of dying suddenly were identified by the combination of the sum of the R and S waves greater than 10 millivolts and septal thickness over 190%, with a sensitivity of 91%, specificity of 78%, positive predictive value of 50%, and a negative predictive value of 97%.

CONCLUSIONS

Children at high risk of dying suddenly with hypertrophic cardiomyopathy, with a subsequent annual mortality of 6.6%, can be distinguished at the time of diagnosis from those patients having a low risk of sudden death, the latter with an annual mortality of 0.27%.

Preparticipation evaluation: an evidence-based review

OBJECTIVE

To review available evidence establishing the validity of the preparticipation evaluation (PPE) as a method for screening health risk prior to participation in exercise and sport. Specific emphasis was placed on reviewing original research evaluating methods to screen participants for risk of sudden cardiovascular death. Literature on the current state of the PPE as a screening tool for athletic participation was examined.

DATA SOURCES

Electronic databases were searched for articles relating to mass screening for sports participation and sudden cardiac death in athletes published up to January 2004. Databases searched included Medline (OVID Web, 1966-2004), PubMed (1966-2004), Sport Discuss (1975-2004), Current Contents, CISTI Source (1993-2004), Cochrane Database of Systematic Reviews, and EBM Reviews. Additional references from the bibliographies of retrieved articles were also reviewed.

SELECTION CRITERIA

All study designs were retrieved, but only those studying athletes and/or student-athletes under age 36 years were reviewed. Of the original research retrieved, the majority of the articles sought to establish incidence or prevalence of cardiovascular causes of sudden death in athletes or the validity of various screening tools. Original research articles seeking to establish the current use of the PPE in all its various forms were also reviewed. All of the articles selected for review consisted of type II, population-based data.

DATA EXTRACTION AND SYNTHESIS

The initial literature search identified 639 papers. Of these, 310 articles that met the selection criteria were reviewed, and 25 articles were identified as original research directly relating to the PPE. All of these contained type II evidence-population-based clinical studies. The majority of the literature on the PPE consists of type III evidence-case-based opinion papers and position papers from respected authors and sports medicine societies and reports of expert committees. This literature was also reviewed, but only original research relevant to the PPE is reported in this article. The majority of these studies examined cardiovascular diseases and screening procedures.

RESULTS

The 5 studies that assessed the format or effectiveness of the PPE concluded that it was inadequate. The format of the PPE is not standardized and does not consistently address the American Heart Association recommendations for cardiovascular screening history and physical exams. A variety of health care professionals, some without proper training, administer the PPE. The 12 original studies that looked at specific cardiovascular screening techniques were divided on the effectiveness of history, physical examination, electrocardiogram, and echocardiography for detecting cardiovascular risks for sudden death in athletes.

CONCLUSIONS

A PPE is required by most sport organizations in America, but research as to its effectiveness is very limited. PPEs have been mandatory in Italy for many years, and we can draw on some the data recorded over this time. Otherwise, very few studies in America or elsewhere have been performed on the PPE process. The research available indicates that the PPE is not implemented adequately or uniformly. An opportunity exists to create a standardized, validated PPE that meets medical standards for quality and provides sensitive, specific screening of potential participants in sport and exercise.