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.

Hypertrophic cardiomyopathy in childhood and adolescence - strategies to prevent sudden death

Clinically overt hypertrophic cardiomyopathy is the most common cause of sudden unexpected death in childhood and has significantly higher sudden death mortality in the 8- to 16-year age range than in the 17- to 30-year age range. A combination of electrocardiographic risk factors (a limb-lead ECG voltage sum >10 mV) and/or a septal wall thickness >190% of upper limit of normal for age (z-score > 3.72) defines a paediatric high-risk patient with great sensitivity. Syncope, blunted blood pressure response to exercise, non-sustained ventricular tachycardia and a malignant family history are additional risk factors. Of the medical treatments used, only beta-blocker therapy with lipophilic beta-blockers (i.e. propranolol, metoprolol or bisoprolol) have been shown to significantly reduce risk of sudden death, with doses ≥ 6 mg/kg BW in propranolol equivalents giving around a tenfold reduction in risk. Disopyramide therapy is a very useful adjunct to beta-blockers to improve prognosis in those patients that have dynamic outflow obstruction in spite of large doses of beta-blocker, and its use in patients with hypertrophic cardiomyopathy is not associated with significant pro-arrhythmia mortality. Calcium-channel blockers increase the risk of heart failure-associated death in hypertrophic cardiomyopathy (HCM) patients with severe generalized hypertrophy and should be avoided in such patients. Amiodarone does not protect against sudden death, and long-term use in children usually has to be terminated because of side effects. Therapy with internal cardioverter defibrillator implantation has high paediatric morbidity, 27% incidence of inappropriate shocks, and does not absolutely protect against mortality but is indicated as secondary prevention or in very high-risk patients.

Electrocardiographic amplitudes: a new risk factor for sudden death in hypertrophic cardiomyopathy

Aims

Assessment of ECG-features as predictors of sudden death in adults with hypertrophic cardiomyopathy (HCM).

Methods and results

ECG-amplitude sums were measured in 44 normals, 34 athletes, a hospital-cohort of 87 HCM-patients, and 29 HCM-patients with sudden death or cardiac arrest (HCM-CA). HCM-patients with sudden death or cardiac arrest had substantially higher ECG-amplitudes than the HCM-cohort for limb-lead and 12-lead QRS-amplitude sums, and amplitude–duration products (P = 0.00003–P = 0.000002). Separation of HCM-CA from the HCM-cohort is obtained by limb-lead QRS-amplitude sum ≥7.7 mV (odds ratio 18.8, sensitivity 87%, negative predictive value (NPV) 94%, P < 0.0001), 12-lead amplitude–duration product ≥2.2 mV s (odds ratio 31.0, sensitivity 92%, NPV 97%, P < 0.0001), and limb-lead amplitude–duration product ≥0.70 mV s (odds ratio 31.5, sensitivity 93%, NPV 96%, P < 0.0001). Sensitivity in HCM-patients <40 years is 90, 100, and 100% for those ECG-variables, respectively. Qualitative analysis showed correlation with cardiac arrest for pathological T-wave-inversion (P = 0.0003), ST-depression (P = 0.0010), and dominant S-wave in V₄ (P = 0.0048). A risk score is proposed; a score ≥6 gives a sensitivity of 85% but a higher positive predictive value than above measures. Optimal separation between HCM-CA <40 years and athletes is obtained by a risk score ≥6 (odds ratio 345, sensitivity 85%, specificity 100%, P < 0.0001).

Conclusion

Twelve-lead ECG is a powerful instrument for risk-stratification in HCM.

Impact of pulse oximetry screening on the detection of duct dependent congenital heart disease: a Swedish prospective screening study in 39,821 newborns

OBJECTIVE

To evaluate the use of pulse oximetry to screen for early detection of life threatening congenital heart disease.

DESIGN

Prospective screening study with a new generation pulse oximeter before discharge from well baby nurseries in West Götaland. Cohort study comparing the detection rate of duct dependent circulation in West Götaland with that in other regions not using pulse oximetry screening. Deaths at home with undetected duct dependent circulation were included.

SETTING

All 5 maternity units in West Götaland and the supraregional referral centre for neonatal cardiac surgery.

PARTICIPANTS

39,821 screened babies born between 1 July 2004 and 31 March 2007. Total duct dependent circulation cohorts: West Götaland n=60, other referring regions n=100.

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive and negative predictive values, and likelihood ratio for pulse oximetry screening and for neonatal physical examination alone.

RESULTS

In West Götaland 29 babies in well baby nurseries had duct dependent circulation undetected before neonatal discharge examination. In 13 cases, pulse oximetry showed oxygen saturations <or=90%, and (in accordance with protocol) clinical staff were immediately told of the results. Of the remaining 16 cases, physical examination alone detected 10 (63%). Combining physical examination with pulse oximetry screening had a sensitivity of 24/29 (82.8% (95% CI 64.2% to 95.2%)) and detected 100% of the babies with duct dependent lung circulation. Five cases were missed (all with aortic arch obstruction). False positive rate with pulse oximetry was substantially lower than that with physical examination alone (69/39 821 (0.17%) v 729/38 413 (1.90%), P<0.0001), and 31/69 of the "false positive" cases with pulse oximetry had other pathology. Thus, referral of all cases with positive oximetry results for echocardiography resulted in only 2.3 echocardiograms with normal cardiac findings for every true positive case of duct dependent circulation. In the cohort study, the risk of leaving hospital with undiagnosed duct dependent circulation was 28/100 (28%) in other referring regions versus 5/60 (8%) in West Götaland (P=0.0025, relative risk 3.36 (95% CI 1.37 to 8.24)). In the other referring regions 11/25 (44%) of babies with transposition of the great arteries left hospital undiagnosed versus 0/18 in West Götaland (P=0.0010), and severe acidosis at diagnosis was more common (33/100 (33%) v 7/60 (12%), P=0.0025, relative risk 2.8 (1.3 to 6.0)). Excluding premature babies and Norwood surgery, babies discharged without diagnosis had higher mortality than those diagnosed in hospital (4/27 (18%) v 1/110 (0.9%), P=0.0054). No baby died from undiagnosed duct dependent circulation in West Götaland versus five babies from the other referring regions.

CONCLUSION

Introducing pulse oximetry screening before discharge improved total detection rate of duct dependent circulation to 92%. Such screening seems cost neutral in the short term, but the probable prevention of neurological morbidity and reduced need for preoperative neonatal intensive care suggest that such screening will be cost effective long term.

Cardiomyopathy and exercise intolerance in muscle glycogen storage disease 0

Storage of glycogen is essential for glucose homeostasis and for energy supply during bursts of activity and sustained muscle work. We describe three siblings with profound muscle and heart glycogen deficiency caused by a homozygous stop mutation (R462-->ter) in the muscle glycogen synthase gene. The oldest brother died from sudden cardiac arrest at the age of 10.5 years. Two years later, an 11-year-old brother showed muscle fatigability, hypertrophic cardiomyopathy, and an abnormal heart rate and blood pressure while exercising; a 2-year-old sister had no symptoms. In muscle-biopsy specimens obtained from the two younger siblings, there was lack of glycogen, predominance of oxidative fibers, and mitochondrial proliferation. Glucose tolerance was normal.

Noninvasive peripheral perfusion index as a possible tool for screening for critical left heart obstruction

AIM

Peripheral perfusion index (PPI) has been suggested as a possible method to detect illness causing circulatory embarrassment. We aimed to establish the normal range of this index in healthy newborns, and compare it with newborns with duct-dependent systemic circulation.

DESIGN

We conducted a case-control study.

SETTING

Our study population comprised 10,000 prospectively recruited newborns from Västra Götaland, Sweden.

PATIENTS

A total of 10,000 normal newborns and 9 infants with duct-dependent systemic circulation (left heart obstructive disease [LHOD] group) participated in the study.

METHODS

We conducted single pre- and postductal measurements of PPI with a new generation pulse oximeter (Masimo Radical SET) before discharge from hospital.

RESULTS

PPI values between 1 and 120 h of age show an asymmetrical, non-normal distribution with median PPI value of 1.70 and interquartile range of 1.18-2.50. The 5th percentile = 0.70 and 95th percentile = 4.50. All infants in the LHOD group had either pre- or postductal PPI below the interquartile range, and 5 of 9 (56%) were below the 5th percentile cut-off of 0.70 (p < 0.0001, Fisher's exact test). A PPI value <0.70 gave an odds ratio for LHOD of 23.75 (95% CI 6.36-88.74).

CONCLUSION

PPI values lower than 0.70 may indicate illness and a value <0.50 (1st percentile) indicates definite underperfusion. PPI values might be a useful additional tool for early detection of LHOD.

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%.

Screening for duct-dependant congenital heart disease with pulse oximetry: a critical evaluation of strategies to maximize sensitivity

AIM

To evaluate the feasibility of detecting duct-dependent congenital heart disease before hospital discharge by using pulse oximetry.

DESIGN

Case-control study.

SETTING

A supra-regional referral centre for paediatric cardiac surgery in Sweden.

PATIENTS

200 normal term newborns with echocardiographically normal hearts (median age 1.0 d) and 66 infants with critical congenital heart disease (CCHD; median age 3 d).

METHODS

Pulse oximetry was performed in the right hand and one foot using a new-generation pulse oximeter (NGoxi) and a conventional-technology oximeter (CToxi).

RESULTS

With the NGoxi, normal newborns showed a median postductal saturation of 99% (range 94-100%); intra-observer variability showed a mean difference of 0% (SD 1.3%), and inter-observer variability was 0% (SD 1.5%). The CToxi recorded a significantly greater proportion of postductal values below 95% (41% vs 1%) in the normal newborns compared with NGoxi (p<0.0001). The CCHD group showed a median postductal saturation of 90% (45-99%) with the NGoxi. Analysis of distributions suggested a screening cut-off of <95%; however, this still gave 7/66 false-negative patients, all with aortic arch obstruction. Best sensitivity was obtained by adding one further criterion: saturation of <95% in both hand and foot or a difference of >+/-3% between hand and foot. These combined criteria gave a sensitivity of 98.5%, specificity of 96.0%, positive predictive value of 89.0% and negative predictive value of 99.5%.

CONCLUSION

Systematic screening for CCHD with high accuracy requires a new-generation oximeter, and comparison of saturation values from the right hand and one foot substantially improves the detection of CCHD.

Differentiation of Athlete's Heart from Pathological Forms of Cardiac Hypertrophy by Means of Geometric Indices Derived from Cardiovascular Magnetic Resonance

PURPOSE

Determination of the underlying etiology of left ventricular hypertrophy (LVH) is a common, challenging, and critical clinical problem. The authors aimed to test whether pathological LVH, such as occurs in hypertrophic cardiomyopathy (HCM), hypertensive heart disease, or aortic stenosis, and physiological LVH in athletes, can be distinguished by means of left ventricular volume and geometric indices, derived from cardiovascular magnetic resonance imaging.

METHODS

A total of 120 subjects were studied on a 1.5 Tesla MR (Sonata, Siemens Medical Solutions, Erlangen, Germany) scanner, comprising healthy volunteers (18), competitive athletes (25), patients with HCM (35), aortic stenosis (24), and hypertensive heart disease (18). Left ventricular mass index, ejection fraction, end-diastolic, end-systolic and stroke volume index, diastolic wall thickness, wall thickness ratio and diastolic and systolic wall-to-volume ratios were determined.

RESULTS

Left ventricular (LV) mass indices were similar for all forms of LVH (p > 0.05), which were at least 35% higher than those obtained in healthy volunteers (p < 0.05). Multiple logistic regression showed that the percentage of correctly predicted diagnoses was 100% for athlete's heart, 80% for hypertrophic cardiomyopathy, 54% for aortic stenosis, and 22% for hypertensive heart disease. Using a receiver operating curve-determined cut-off value for diastolic wall-to-volume ratio of less than 0.15 mm x m2 x ml(-1), athletes' hearts could be differentiated from all forms of pathological cardiac hypertrophy with 99% specificity.

CONCLUSIONS

Athlete's heart can be reliably distinguished from all forms of pathological cardiac hypertrophy using CMR-derived LV volume and geometric indices, but pathological forms of LVH present with overlapping cardiac hypertrophy phenotypes. This capability of CMR should be of high clinical value.

Mutation analysis of AMP-activated protein kinase subunits in inherited cardiomyopathies: implications for kinase function and disease pathogenesis

Familial hypertrophic cardiomyopathy (HCM) has been defined as a disease of the cardiac sarcomere, although sarcomeric protein mutations are not found in one third of cases. We have recently shown that HCM associated with Wolff-Parkinson-White syndrome (WPW) and conduction disease can be caused by mutations in PRKAG2, which encodes the gamma2 subunit of AMPK, an enzyme central to cellular energy homeostasis. AMPK is a heterotrimer composed of one catalytic subunit (alpha) and two regulatory subunits (beta and gamma). Seven known genes encode the subunit isoforms (alpha1, alpha2, beta1, beta2, gamma1, gamma2, gamma3) and all are expressed in the heart. To better understand the role of AMPK mutations in HCM/WPW and other inherited cardiomyophathies, all 7 subunit genes were screened for mutations in a panel of probands: 3 with HCM/WPW, 4 with DCM/WPW, 38 with HCM alone (in whom contractile protein mutations had not been found) and 13 with DCM alone. In total, 73 amplimers were screened in the 58 probands and a number of polymorphisms, including non-conservative substitutions, were identified. However, no further disease-causing mutations were found in any AMPK subunit gene. These results indicate that HCM with WPW is a distinct, but genetically heterogeneous, condition caused by mutations in PRKAG2 and in an unknown gene or genes, not involved in the AMPK complex. Mutations in PRKAG2 appear to specifically cause HCM with WPW and conduction disease, and not other inherited cardiomyopathies. As deleterious alleles were not found in other AMPK subunit isoforms, the mutations affecting PRKAG2 are likely to confer a specific alteration of AMPK function of particular importance in the myocardium.

Hypertrophic cardiomyopathy due to sarcomeric gene mutations is characterized by impaired energy metabolism irrespective of the degree of hypertrophy

OBJECTIVES

We investigated cardiac energetics in subjects with mutations in three different familial hypertrophic cardiomyopathy (HCM) disease genes, some of whom were nonpenetrant carriers without hypertrophy, using phosphorus-31 magnetic resonance spectroscopy.

BACKGROUND

Familial hypertrophic cardiomyopathy is caused by mutations in sarcomeric protein genes. The mechanism by which these mutant proteins cause disease is uncertain. A defect of myocyte contractility had been proposed, but in vitro studies of force generation have subsequently shown opposing results in different classes of mutation. An alternative hypothesis of "energy compromise" resulting from inefficient utilization of adenosine triphosphate (ATP) has been suggested, but in vivo data in humans with genotyped HCM are lacking.

METHODS

The cardiac phosphocreatine (PCr) to ATP ratio was determined at rest in 31 patients harboring mutations in the genes for either beta-myosin heavy chain, cardiac troponin T, or myosin-binding protein C, and in 24 controls. Transthoracic echocardiography was used to measure left ventricular (LV) dimensions and maximal wall thickness.

RESULTS

The PCr/ATP was reduced in the HCM subjects by 30% relative to controls (1.70 +/- 0.43 vs. 2.44 +/- 0.30; p < 0.001), and the reduction was of a similar magnitude in all three disease-gene groups. The PCr/ATP was equally reduced in subjects with (n = 24) and without (n = 7) LV hypertrophy.

CONCLUSIONS

Our data provide evidence of a bioenergetic deficit in genotype-confirmed HCM, which is present to a similar degree in three disease-gene groups. The presence of energetic abnormalities, even in those without hypertrophy, supports a proposed link between altered cardiac energetics and development of the disease phenotype.

A cohort study of neurodevelopmental outcome in children with DiGeorge syndrome following cardiac surgery

AIMS

To examine whether the learning difficulties seen in a proportion of children with DGS are secondary to cardiac pathology and treatment, or a feature of the DGS phenotype.

METHODS

Cohort study of all patients with DGS and coexisting cardiac lesions within a region. Ten children with 22q11 deletion were assigned two controls each, matched for age, sex, cardiac lesion, and preoperative hemodynamic status but without DGS. The neurodevelopmental status was evaluated with the Ruth Griffiths test for babies and young children.

RESULTS

Children with the 22q11 deletion showed a wide range of developmental quotient (DQ; mean 71, 95% CI 47 to 95) and subscale scores, but these as a group were significantly lower than those of the control group (DQ 113, 95% CI 108 to 118). Four of the DGS children had DQs below 60. Hypocalcaemia, prolonged postoperative ventilation, and abnormal neurology perioperatively were associated with a low DQ.

CONCLUSIONS

A proportion of children with DGS have a very poor developmental outcome following cardiac surgery. This outcome is not attributable to the cardiac condition and its treatment alone, but represents either a pre-existing component of the syndrome or an interaction between the syndrome and its treatment.

Mutations of the light meromyosin domain of the beta-myosin heavy chain rod in hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (HCM) is caused by mutations in 9 sarcomeric protein genes. The most commonly affected is beta-myosin heavy chain (MYH7), where missense mutations cluster in the head and neck regions and directly affect motor function. Comparable mutations have not been described in the light meromyosin (LMM) region of the myosin rod, nor would these be expected to directly affect motor function. We studied 82 probands with HCM in whom no mutations had been found in MYH7 exons encoding the head and neck regions of myosin nor in the other frequently implicated disease genes. Primers were designed to amplify exons 24 to 40 of MYH7. These amplimers were subjected to temperature modulated heteroduplex analysis by denaturing high-performance liquid chromatography. An Ala1379Thr missense mutation in exon 30 segregated with disease in three families and was not present in 200 normal chromosomes. The mutation occurred on two haplotypes, indicating that it was not a polymorphism linked with another disease-causing mutation. The position of this residue within the LMM region of myosin suggests that it may be important for thick filament assembly or for accessory protein binding. A further missense mutation in exon 37, Ser1776Gly, segregated with disease in a single family and was absent from 400 population-matched control chromosomes. Because the Ser1776 residue occupies a core position in the myosin rod at which the substitution of glycine is extremely energetically unfavorable, it is likely to disrupt the coiled-coil structure. We conclude that mutation of the LMM can cause HCM and that such mutations may act through novel mechanisms of disease pathogenesis involving myosin filament assembly or interaction with thick filament binding proteins.

Prevention of exercise-induced cardiac hypertrophy in rats by chemical sympathectomy (guanethidine treatment)

The effect of 'chemical sympathectomy', produced by daily intraperitoneal injections of guanethidine sulphate for six weeks, was studied in sedentary rats and in rats chronically exercised by swimming. The guanethidine-treatment itself caused the following changes. There was a reduction in the rate of weight gain resulting in a 7% lower final body weight. Organ content of noradrenaline was decreased by 90% in spleen and submandibular glands and by 83% in the heart. Urinary excretion of noradrenaline was also decreased, but to a lesser degree, both during rest (45% lower) and after acute exercise (46% lower), while the urinary excretion of adrenaline was no different from that of controls. There was a compensatory adrenal hypertrophy in the guanethidine-treated rats, with a significant increase in adrenal catecholamine levels that was more pronounced for noradrenaline (+45%) than for adrenaline (+11%). Chronic physical exercise produced the expected degree of cardiac hypertrophy in untreated rats, but this adaptive cardiac hypertrophy was completely absent in the exercised guanethidine-treated rats. The results indicate, firstly that a good degree of chemical sympathectomy was obtained and that the persistence of a considerable urinary excretion of catecholamines in the guanethidine-treated rats was due to a compensatory increase in the secretory activity of the adrenal medulla. Secondly, it is suggested that the adaptive cardiac hypertrophy produced by chronic exercise is not caused by a direct effect of the increased work load on the cardiac muscle cell, but is instead mediated by release of a trophic factor from cardiac sympathetic nerves, probably noradrenaline itself but possibly a secretory protein.

Mutations in the gamma(2) subunit of AMP-activated protein kinase cause familial hypertrophic cardiomyopathy: evidence for the central role of energy compromise in disease pathogenesis

Familial hypertrophic cardiomyopathy (HCM) has been widely studied as a genetic model of cardiac hypertrophy and sudden cardiac death. HCM has been defined as a disease of the cardiac sarcomere, but mutations in the known contractile protein disease genes are not found in up to one-third of cases. Further, no consistent changes in contractile properties are shared by these mutant proteins, implying that an abnormality of force generation may not be the underlying mechanism of disease. Instead, all of the sarcomeric mutations appear to result in inefficient use of ATP, suggesting that an inability to maintain normal ATP levels may be the central abnormality. To test this hypothesis we have examined candidate genes involved in energy homeostasis in the heart. We now describe mutations in PRKAG2, encoding the gamma(2) subunit of AMP-activated protein kinase (AMPK), in two families with severe HCM and aberrant conduction from atria to ventricles in some affected individuals (pre-excitation or Wolff-Parkinson-White syndrome). The mutations, one missense and one in-frame single codon insertion, occur in highly conserved regions. Because AMPK provides a central sensing mechanism that protects cells from exhaustion of ATP supplies, we propose that these data substantiate energy compromise as a unifying pathogenic mechanism in all forms of HCM. This conclusion should radically redirect thinking about this disorder and also, by establishing energy depletion as a cause of myocardial dysfunction, should be relevant to the acquired forms of heart muscle disease that HCM models.

A simple method for assessing the regression or progression of ventricular hypertrophy in the growing child and adult: the value of left ventricular wall-to-cavity ratios

AIMS

To establish the normal range of diastolic and systolic left ventricular wall-to-cavity ratios.

METHODS AND RESULTS

Two hundred and sixty-two normal subjects (age 0-40 years), 15 children with valvar aortic stenosis and 11 childhood athletes were studied with M-mode echocardiography. Values of diastolic septum-to-cavity ratio and diastolic left ventricular wall-to-cavity ratio were not influenced by sex nor, in adults, by height, weight or body surface area. There were slight age variations from 0-15 years of age, but not in adults from 15-40 years of age. Values of diastolic left ventricular wall-to-cavity ratio in neonates were 0.18 (95% confidence limits 0.17-0.19); in 3-5 year olds 0.16 (0.15-0.16); and in adults 0.18 (0.17-0.19). In valvar aortic stenosis there is a positive correlation between the Doppler-estimated pressure gradient and the degree of left ventricular hypertrophy, as expressed by both diastolic and systolic left ventricular wall-to-cavity ratio (r = 0.90;P < 0.00001 and r = 0.85;P = 0.00006 respectively).

CONCLUSIONS

Diastolic septum and left ventricular wall-to-cavity ratios accurately differentiate physiological from pathological left ventricular hypertrophy in the growing child. Because these ratios are independent of sex and body size, they may also be more sensitive than absolute wall thickness in the detection of abnormal left ventricular hypertrophy in adults.

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

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.

Recommendations of the British Paediatric Cardiac Association for therapeutic cardiac catheterisation in congenital cardiac disease

The aims of these recommendations are to improve the outcome for patients after, and to provide acceptable standards of practice of therapeutic cardiac catheterisation performed to treat congenital cardiac disease. The scope of the recommendations includes all interventional procedures, recognising that for some congenital malformations, surgical treatment is equally as effective as, or occasionally preferable to, interventional treatment. The limitations of the recommendations are that, at present, no data are available which compare the results of interventional treatment with surgery, and certainly none which evaluate the numbers and types of procedures that need to be performed for the maintenance of skills. Thus, there is a recognised need to collect comprehensive data with which these recommendations could be reviewed in the future, and re-written as evidence-based guidelines. Such a review will have to take into account the methods of collection of data, their effectiveness, and the latest developments in technology. The present recommendations should, therefore, be considered as consensus statements, and as describing accepted practice, which could be used as a basis for ensuring and improving the quality of future care.

A cohort study of childhood hypertrophic cardiomyopathy: improved survival following high-dose beta-adrenoceptor antagonist treatment

OBJECTIVES

The study analyzed factors, including treatment, affecting disease-related death in patients with hypertrophic cardiomyopathy (HCM) presenting in childhood.

BACKGROUND

Previous smaller studies suggest that mortality is higher in patients with HCM presenting in childhood compared with presentation in adulthood, but these studies have all originated from selected patient populations in tertiary referral centers, and reported no significant protection by treatment.

METHODS

Retrospective comparisons of mortality were done in total cohort of patients presenting to three regional centers of pediatric cardiology. There were 66 patients (25 with Noonan's syndrome) with HCM presenting at age <19 years; mean follow-up was 12.0 years.

RESULTS

Among risk factors for death were congestive heart failure (p = 0.008), large electrocardiogram voltages (Sokolow-Lyon index p = 0.0003), and degree of septal (p = 0.004) and left ventricular (p = 0.028) hypertrophy expressed as percent of 95th centile value. The only treatment that significantly reduced the risk of death on multifactorial analysis of variance was high-dose beta-adrenoceptor antagonist therapy (propranolol 5 to 23 mg/kg/day or equivalent; p = 0.0001). Nineteen out of 40 patients managed conventionally (no treatment, 0.8 to 4 mg/kg of propranolol, or verapamil) died, median survival 15.8 years, with no deaths among 26 patients on high-dose beta-blockers (p = 0.0004); survival proportions at 10 years were 0.65 (95% confidence interval 0.49-0.80) and 1.0, respectively (p = 0.0015). Survival time analysis shows better survival in the high-dose beta-blocker group compared with the "no specific therapy" group (p = 0.0009) and with the conventional-dose beta-blocker group (p = 0.002). Hazard ratio analysis suggests that high-dose beta-blocker therapy produces a 5-10-fold reduction in the risk of disease-related death.

CONCLUSIONS

High-dose beta-blocker therapy improves survival in childhood HCM.

A comparison of MRI and echocardiography in hypertrophic cardiomyopathy

This study compares MRI and echocardiography as imaging modalities in hypertrophic cardiomyopathy, with particular reference to measurement of left ventricular wall thickness and mass. 10 subjects underwent echocardiography and MRI. Contiguous 10 mm short axis 35 degrees flip angle cine gradient recalled echo MR images were acquired from the apex to the base of the left ventricle at 1.5 tesla. Standard M-mode and cross-sectional echocardiographic views of the left ventricle were obtained. Excellent agreement between measurements occurred with MRI and M-mode echocardiographic assessment of the thickness of the anterior interventricular septum (95% limits of agreement -1.5 to +1.5 mm). Other comparisons of MRI vs M-mode echocardiographic measurements had the following limits of agreement: posterior free wall -3.3 to +2.9 mm; end-diastolic dimension -5 to +8 mm, left ventricular mass -291 to +55.5 g. Comparing MRI with cross-sectional echocardiographic measurements, the limits of agreement were: anterior interventricular septum -2.4 to +1.7 mm, posterior interventricular septum -2.4 to +2.9 mm, posterior free wall -3.4 to +2.5 mm, anterior free wall -2.4 to +1.7 mm, end-diastolic dimension -4.1 to +8 mm. MRI estimates of LVM in systole vs diastole showed good agreement with 95% limits of agreement of -20 to +17 g, with excellent interobserver variability in diastole (-9 to +5 g) and in systole (-7 to +12 g). In conclusion, MRI is superior to echocardiography for the quantification of ventricular mass in the abnormal left ventricle because it does not make invalid geometrical assumptions. Comparisons of wall thickness show greater discrepancy with increasing distance from the echocardiographic transducer. This study suggests that sequential echocardiography could rationalize the need for MRI in left ventricular hypertrophy. A change in anterior septal thickness of > or = 3 mm on echocardiography merits a further MRI study.

Middle aortic syndrome in a boy with arteriohepatic dysplasia (Alagille syndrome)

Middle aortic syndrome is increasingly recognized as a cause of hypertension in adolescents and young adults. Alagille syndrome is a genetic disorder characterized by hepatic, eye, and bony abnormalities. Cardiovascular lesions occur in most of the patients, but narrowing of the abdominal aorta has not been previously recorded. We present an unusual association between middle aortic syndrome and Alagille syndrome, with a similar vascular lesion seen in two generations.

Infant Ross procedure for recurrent aortic stenosis

A male infant underwent an open aortic valvotomy during the second day of life. Aortic stenosis recurred and at the age of eight weeks he underwent a pulmonary autograft aortic root replacement (Ross procedure). The pulmonary autograft procedure is a valuable option in this circumstance.

Effects of oxygen and nitric oxide in oxygen on pulmonary arterial pressures of children with congenital cardiac defects

Inhaled nitric oxide is a specific pulmonary vasodilator. This study was undertaken to assess the effect on pulmonary arterial pressure of administering 100% oxygen compared with nitric oxide in oxygen. Thirteen mechanically ventilated children undergoing routine cardiac catheterization for the investigation of congenital heart disease were studied. Pulmonary arterial pressures were measured during inhalation of 30% oxygen (baseline), 100% oxygen, and nitric oxide (40 parts per million) in oxygen. In addition, in six children the pulmonary/systemic blood flow ratio and pulmonary vascular resistance were calculated using oxygen content, an assumed value for oxygen uptake, and the Fick principle. Results were compared using analysis of variance and the Wilcoxon signed-rank test. Pulmonary arterial pressure decreased from a mean value of 29.5 mmHg (SD 15.1) to 25.6 mmHg (SD 9.3), p = 0.048, after increasing the inspired oxygen fraction from 0.3 to 1.0. The addition of nitric oxide caused a further reduction to 22.9 mmHg (SD 7.9), p = 0.0001. There was no change in systemic arterial pressure or heart rate during the study period, but a small increase occurred in the mean methemoglobin level (1.1% to 1.3%) p = 0.039. Changes in the pulmonary/systemic blood flow ratio and pulmonary vascular resistance (n = 6) were not significant. Nitric oxide in oxygen appears to be a more potent pulmonary vasodilator than oxygen alone in pediatric patients with congenital cardiac defects.

Reduction by oral propranolol treatment of left ventricular hypertrophy secondary to pressure-overload in the rat

1. Studies on cardiac myocyte cell cultures have postulated a role for alpha 1-adrenoceptors and mechanical stretch in the induction of cellular changes thought to be important in compensatory cardiac hypertrophy. However, in vivo work suggests that beta-adrenoceptors are important and the present study was designed to analyse the effect of propranolol on the cardiac hypertrophy caused by a pressure-overload in a way that takes account of the effects of propranolol on the work load itself. 2. The compensatory cardiac hypertrophy that develops in response to experimental coarctation of the aorta was studied in the rat. Pressure gradients and total cardiac work load (expressed as rate x pressure product) were assessed, and the relationship between increasing cardiac work load and the resulting left ventricular hypertrophy was established in a control group and compared with left ventricular hypertrophy in a group treated with a high dose of oral propranolol (80 mg kg-1 body weight). 3. In the rats with mean pressure gradients over the coarctation in the range of 15-31 mmHg, the animals on control diet showed a 38% increase in left ventricular weight/body weight ratio (LV ratio) and a 30% increase in heart weight/body weight ratio (heart ratio), whereas rats given high dose oral propranolol-treatment showed increases of only 13% and 9%, respectively. 4. In a second series of rats with a wider range of pressure gradients, the regression lines of LV ratio versus mean pressure gradient, and of LV ratio versus cardiac work, were different in the two groups with a slope that was only half as steep in the propranolol-treated rats as in the controls. Thus, for the same increment in cardiac work load, the degree of compensatory cardiac hypertrophy in propranolol-treated rats was half that observed in controls. 5. The reduction in compensatory cardiac hypertrophy was not associated with an increase in incidence of congestive heart failure and the propranolol-treated rats were able to sustain equally high (or higher) degrees of pressure over-load as controls did. 6. It is concluded that propranolol treatment approximately halves the compensatory cardiac hypertrophy occurring in response to a left ventricular pressure over-load by a mechanism independent of its effect on cardiac work load. This finding provides further support for the view that noradrenaline released from sympathetic nerve terminals in the heart exerts a trophic effect on cardiac myocytes, and that the sympathetic nervous system may be the final common pathway in many forms of compensatory cardiac hypertrophy. In contrast to in vitro models, this effect appears to be largely mediated via beta-adrenoceptors in the intact animal.

Reduction by beta-adrenoceptor blockade of hypoxia-induced right heart hypertrophy in the rat

1. The study was undertaken to assess the role of beta-adrenoceptors in the induction of compensatory cardiac hypertrophy in an in vivo model. 2. In the rat, exposure to severe hypoxia (6% inspired oxygen for 8 h day) caused a 51% increase in right heart weight and a 75% increase in haematocrit. 3. The hypoxia-induced right ventricular hypertrophic response was reduced by 65% by oral treatment with a high dose of the non-selective beta-adrenoceptor antagonist, propranolol (80 mg kg-1 body weight); the drug treatment caused only a minor reduction (6%) in secondary polycythaemia. 4. With a less severe degree of hypoxia (7% inspired oxygen) there was only minimal secondary polycythaemia (+15%), and a lesser degree of compensatory right ventricular hypertrophy in untreated rats (+33%). 5. Treatment with the beta 1-adrenoceptor antagonist, atenolol, in a dose of 80 mg kg-1 body weight abolished right ventricular hypertrophy in response to 7% inspired oxygen, without affecting haematocrit and caused a small reduction in the ratio of heart weight to body weight in normoxic rats. 6. The results show that the effect of propranolol on hypoxic right ventricular hypertrophy is not secondary to any effect on secondary polycythaemia as has previously been suggested and that a marked reduction of compensatory cardiac hypertrophy can be obtained by a beta 1-selective adrenoceptor antagonist. Thus these findings support the view that noradrenaline released from cardiac sympathetic nerve terminals exerts a trophic effect on myocardial cells and demonstrates that in vivo, this trophic effect can be reduced by beta 1-adrenoceptor blockade.

The post-angiocardiography urogram in children: should it be abandoned?

This study examines the value of the urogram radiograph taken after angiocardiography, in children with suspected congenital heart disease, to screen for co-existent urinary tract abnormalities. A retrospective audit of post-angiocardiography urograms over a three year period 1990 to 1993 is presented. 184 urograms obtained in 166 children were reviewed (86 males; mean age 18.1 months). Twenty-five urograms (13.6%) were obtained in cases where the urinary tract had previously been investigated. These urograms contributed no additional information. Image quality was suboptimal in 62 examinations (33.7%), due to gas, faeces or poor opacification, and two lesions were undetected on suboptimal radiographs. Urinary tract abnormalities were detected in 17 patients (10.2%). These lesions were also detectable at sonography. We suggest that routine post-angiocardiography urograms can be abandoned in favour of sonographic screening of the urinary tract in children with congenital heart disease.

Dilated cardiomyopathy due to type II X-linked 3-methylglutaconic aciduria: successful treatment with pantothenic acid

A case of dilated cardiomyopathy in a young boy secondary to type II 3-methylglutaconic aciduria is described. A metabolic cause for his dilated cardiomyopathy was suspected because of the development on the electrocardiogram of an unusual "camel's hump" shape of the T waves, and of progressive thickening with increasing echogenicity of the left ventricular wall. He initially improved on digoxin treatment, but did not maintain the response with conventional dietary treatment for this condition. Supplementation with L-carnitine was associated with rapid deterioration in cardiac state, and may be contraindicated in this condition. At a point when the patient was moribund, large doses of pantothenic acid, a precursor of coenzyme A, produced a dramatic and sustained improvement in myocardial function and in growth, neutrophil cell count, hypocholesterolaemia, and hyperuricaemia, which suggests that limitation of availability of coenzyme A is a fundamental pathological process in this condition. The clinical improvement has been maintained for 13 months, and myocardial function is now nearly normal. Oral pantothenol, unlike pantothenic acid, is not efficacious.

Congenital septation of the aortic arch with carotid stenosis

A 14-year-old white boy presented with syncope and a left carotid bruit. Arch aortogram showed narrowing of the distal aortic arch, left carotid stenosis, and small left subclavian and vertebral arteries. When aortic arch replacement was carried out a vertical septum was found in the distal arch. Histologic examination suggested this was ductal in origin.

Congenital heart block with hydrops fetalis treated with high-dose dexamethasone; a case report

A 32-year-old woman with systemic lupus erythematosus was found to have a fetus with heart block and fetal ascites at 23 weeks gestation. Treatment with high-dose corticosteroids ameliorated the early signs of heart failure, although the fetal heart rate gradually fell from 48 beats/min to 42 beats/min by 34 weeks. Sudden deterioration of the fetal state occurred at 35 weeks, and this only partially responded to digitalisation. Neonatal death occurred on Day 18 from the consequences of severe birth asphyxia. The relationship and pathogenesis of anti-Ro antibodies, congenital heart block and hydrops fetals are discussed, together with the in utero management of this condition.

Hydrops fetalis due to abnormal lymphatics

A case of generalised lymphatic abnormality that presented with hydrops fetalis is described. This seems to be the first such case reported.

Cor triatriatum sinistrum. Diagnostic features on cross sectional echocardiography

M mode and cross sectional echocardiography was carried out in three cases of cor triatriatum sinistrum (two infants and one adult). In two cases a peculiar double arch appearance, not previously reported, was found. All three cases were referred for surgery without cardiac catheterisation, and the diagnosis proved to be correct. The characteristic echocardiographic feature of cor triatriatum is an intra-atrial membrane detected in multiple planes of examination, curving anteroinferiorly and inserting some distance away from the mitral valve ring, proximal to the left atrial appendage. Superiorly the membrane runs parallel to, and a short distance behind, the aortic root creating a superior recess of the distal left atrial chamber. These features differentiate cor triatriatum from a supravalvar mitral ring. During diastole the membrane moves forward towards the mitral valve funnel. This, together with the arching appearance of the membrane on four chamber views and the more superior position of the membrane, makes it possible to distinguish cor triatriatum from total anomalous pulmonary venous drainage to the coronary sinus. From a review of past experience at the Brompton Hospital of the diagnostic accuracy of cardiac catheterisation in this condition, it is concluded that cross sectional echocardiography is superior to angiography as a technique for diagnosing cor triatriatum.