Magnitude of left ventricular hypertrophy and risk of sudden death in hypertrophic cardiomyopathy

Effect of left ventricular outflow tract obstruction on clinical outcome in hypertrophic cardiomyopathy

BACKGROUND

The influence of left ventricular outflow tract obstruction on the clinical outcome of hypertrophic cardiomyopathy remains unresolved.

METHODS

We assessed the effect of outflow tract obstruction on morbidity and mortality in a large cohort of patients with hypertrophic cardiomyopathy who were followed for a mean (+/-SD) of 6.3+/-6.2 years.

RESULTS

Of the 1101 consecutive patients, 273 (25 percent) had obstruction of left ventricular outflow under basal (resting) conditions with a peak instantaneous gradient of at least 30 mm Hg. A total of 127 patients (12 percent) died of hypertrophic cardiomyopathy, and 216 surviving patients (20 percent) had severe, disabling symptoms of progressive heart failure (New York Heart Association [NYHA] functional class III or IV). The overall probability of death related to hypertrophic cardiomyopathy was significantly greater among patients with outflow tract obstruction than among those without obstruction (relative risk, 2.0; P=0.001). The risk of progression to NYHA class III or IV or death specifically from heart failure or stroke was also greater among patients with obstruction (relative risk, 4.4; P<0.001), particularly among patients 40 years of age or older (P<0.001). Age-adjusted multivariate analysis confirmed that outflow tract obstruction was independently associated with an increased risk of both death related to hypertrophic cardiomyopathy (relative risk, 1.6; P=0.02) and progression to NYHA class III or IV or death from heart failure or stroke (relative risk, 2.7; P<0.001). The likelihood of severe symptoms and death related to outflow tract obstruction did not increase as the gradient increased above the threshold of 30 mm Hg.

CONCLUSIONS

In patients with hypertrophic cardiomyopathy, left ventricular outflow tract obstruction at rest is a strong, independent predictor of progression to severe symptoms of heart failure and of death.

Maximum left ventricular thickness and risk of sudden death in patients with hypertrophic cardiomyopathy

OBJECTIVES

We sought to assess the relationship between maximum left ventricular (LV) wall thickness and outcome in patients with hypertrophic cardiomyopathy (HCM).

BACKGROUND

An association between maximum LV wall thickness and risk of sudden death was suggested in HCM. This finding requires further investigation, given the important implications for risk stratification and treatment.

METHODS

We analyzed the mortality and risk profile of 237 patients (age 41 +/- 17 years; 63% male) classified into five groups based on echocardiographic maximum LV thickness.

RESULTS

During follow-up (12 +/- 7 years), 36 patients died of cardiovascular causes, including 16 sudden deaths. Maximum LV thickness was not associated with a risk of sudden death (p = 0.37) nor with overall cardiovascular mortality (p = 0.7). With the exception of the small subset with thickness values < or =15 mm, with a consistently benign clinical course, the distribution of sudden death and overall cardiovascular mortality was not significantly different among the other four classes, ranging from 16 to 19 mm to > or =30 mm. Among 30 patients with extreme LV thickness (> or =30 mm), only one sudden event occurred among six patients diagnosed at <18 years of age (17%) and none among 24 diagnosed at > or =18 years of age. The prevalence of nonsustained ventricular tachycardia, syncope, an abnormal blood pressure response to exercise, and atrial fibrillation was similar among the five thickness classes.

CONCLUSIONS

During 12-year follow-up, we observed no association between maximum LV thickness and cardiovascular mortality in a community-based population with HCM. The degree of maximum LV wall thickness should be considered in the context of a multifactorial approach to risk stratification, rather than as an isolated risk factor. Only in those patients diagnosed at a very young age might the presence of extreme LV wall thickness represent, per se, a potential marker of risk of sudden death.

Imaging of cardiopulmonary diseases

Clear physiologic adaptations to endurance and resistance training occur in the myocardium. These morphologic changes have been identified primarily by echocardiography. In the evaluation of the symptomatic athlete, imaging is a valuable tool. To differentiate athletic hypertrophy from hypertrophic cardiomyopathy, echocardiography, or MRI may be used, although the latter may be superior in the accurate assessment of wall thickness. Either imaging modality may be used to differentiate athletic dilatation from dilated cardiomyopathy in which systolic dysfunction always accompanies the dilatation. To exclude anomalous coronary arteries, either MRI or CT is a reasonable examination, although the latter requires x-ray exposure and iodinated contrast dye. Chest radiograph continues to be the standard imaging modality for athletic lung disease, whereas fluoroscopy and laryngoscopy are useful for identifying vocal cord dysfunction. Knowledge of the utility of these different imaging modalities is crucial to the practitioner of sports medicine.

Sudden death prevented in hypertrophic cardiomyopathy

The most common cause of sudden cardiac death in individuals aged less than 35 years, including competitive athletes, is the inherited disorder hypertrophic cardiomyopathy (HCM). Until recently, no therapeutic intervention had been identified to prevent sudden death in HCM. This case report highlights the role of the implantable cardioverter defibrillator (ICD) in preventing sudden death in patients with HCM. The report highlights the importance of risk stratification in patients with HCM in order to identify those individuals who would most likely benefit from ICD therapy. The ICD implantation is now the treatment of choice in preventing sudden death in selected (highest risk) populations with HCM. In the future, understanding the molecular basis of sudden death in HCM may identify potential new gene-based therapeutic strategies.

First-pass MR imaging in the assessment of perfusion impairment in patients with hypertrophic cardiomyopathy and the Asp175Asn mutation of the alpha-tropomyosin gene

PURPOSE

To assess first-pass magnetic resonance (MR) imaging in the evaluation of perfusion impairment in a genetically homogeneous population of patients with hypertrophic cardiomyopathy (HCM) and the Asp175Asn mutation of the alpha-tropomyosin gene and to evaluate the association between hypertrophy and perfusion.

MATERIALS AND METHODS

Rest-stress first-pass MR imaging with gadopentetate dimeglumine was performed in 17 patients with HCM and the Asp175Asn substitution in the alpha-tropomyosin gene and in five control subjects. Global and segmental first-pass reserve index (FPR) measurements were derived from signal intensity versus time curves. Left ventricular (LV) wall thickness and LV mass index were measured on cine MR images. The Mann-Whitney test was used to evaluate the difference in FPR between the patient group and the control group. The Spearman correlation was used to evaluate the association between LV hypertrophy and FPR.

RESULTS

Global FPR was significantly lower in the patients with HCM than in the control subjects (1.12 +/- 0.35 vs 1.80 +/- 0.58, P =.015). In patients with HCM, maximal LV wall thickness and LV mass index correlated negatively with global FPR (r = -0.723, P =.001 and r = -0.598, P =.011, respectively). At the regional level, segmental FPR correlated inversely with LV wall thickness (r = -0.389; P <.001) in patients with HCM.

CONCLUSION

First-pass MR imaging facilitates global and regional evaluation of perfusion impairment in patients with HCM. The severity of perfusion impairment is associated with the degree of LV hypertrophy.

Myocardial scarring in asymptomatic or mildly symptomatic patients with hypertrophic cardiomyopathy

OBJECTIVES

We sought to ascertain whether myocardial scarring occurs in living unselected patients with hypertrophic cardiomyopathy (HCM).

BACKGROUND

Myocardial scarring is known to occur in select HCM patients, who were highly symptomatic prior to death or who died suddenly. The majority of HCM patients, however, are minimally symptomatic and have not suffered sudden death.

METHODS

Cine and gadolinium-enhanced magnetic resonance imaging was performed in 21 HCM patients who were predominantly asymptomatic. Gadolinium hyperenhancement was assumed to represent myocardial scar, and the extent of scar was compared to left ventricular (LV) morphology and function.

RESULTS

Scarring was present in 17 patients (81%). Scarring occurred only in hypertrophied regions (> or =10 mm), was patchy with multiple foci, and predominantly involved the middle third of the ventricular wall. All 17 patients had scarring at the junction of the interventricular septum and the right ventricular (RV) free wall. On a regional basis, the extent of scarring correlated positively with wall thickness (r = 0.36, p < 0.0001), and inversely with wall thickening (r = -0.21, p < 0.0001). On a per patient basis, the extent of scarring (mean, 8 +/- 9% of LV mass) was minimally related to maximum wall thickness (r = 0.40, p = 0.07) and LV mass (r = 0.33, p = 0.15), and correlated inversely with ejection fraction (r = -0.46, p = 0.04).

CONCLUSIONS

Myocardial scarring is common in asymptomatic or mildly symptomatic HCM patients who have not suffered sudden death. When present, scarring occurs in hypertrophied regions, is consistently localized to the junctions of the septum and RV free wall, and correlates positively with regional hypertrophy and inversely with regional contraction.

Genetic causes of inherited cardiac hypertrophy: Robert L. Frye Lecture

Cardiac hypertrophy is well recognized as a cardiac manifestation of systemic disorders such as hypertension or intrinsic myocardial disease, but it can also reflect an underlying genetic defect. Molecular studies of inherited forms of cardiac hypertrophy have defined 2 novel pathways that lead to cardiac remodeling in adults, discoveries that increasingly provide insights relevant for both diagnosis and management. This article reviews the genetic studies that led to the current molecular understanding of hypertrophic cardiomyopathy and discusses more recently discovered causes of inherited cardiac hypertrophy.

Risk associated with pregnancy in hypertrophic cardiomyopathy

OBJECTIVES

We sought to assess mortality and morbidity in pregnant women with hypertrophic cardiomyopathy (HCM).

BACKGROUND

The risk associated with pregnancy in women with HCM is an important and increasingly frequent clinical issue for which systematic data are not available and a large measure of uncertainty persists.

METHODS

Maternal mortality in 91 consecutively evaluated families with HCM was compared with that reported in the general population. The study cohort included 100 women with HCM with one or more live births, for a total of 199 live births. Morbidity related to HCM during pregnancy was investigated in 40 women evaluated within five years of their pregnancy.

RESULTS

Two pregnancy-related deaths occurred, both in patients at a particularly high risk. The maternal mortality rate was 10 per 1,000 live births (95% confidence interval [CI] 1.1 to 36.2/1,000) and was in excess of the expected mortality in the general Italian population (relative risk 17.1, 95% CI 2.0 to 61.8). In the 40 patients evaluated within close proximity of their pregnancy, 1 (4%) of the 28 who were previously asymptomatic and 5 (42%) of the 12 with symptoms progressed to functional class III or IV during pregnancy (p < 0.01). One patient had atrial fibrillation and one had syncope, both of whom had already experienced similar and recurrent events before their pregnancy.

CONCLUSIONS

Maternal mortality is increased in patients with HCM compared with the general population. However, absolute maternal mortality is low and appears to be principally confined to women at a particularly high risk. In the presence of a favorable clinical profile, the progression of symptoms, atrial fibrillation, and syncope are also uncommon during pregnancy.

Echocardiographic assessment of patients with hypertrophic and restrictive cardiomyopathy: imaging and echocardiography

Echocardiography has evolved to be an important tool in the assessment of patients with hypertrophic and restrictive cardiomyopathy. In this article, the authors review the use of echocardiography in diagnosis, differentiation from disease mimics, assessment of prognosis, and the assistance of specific therapies. A pathophysiologic understanding of restrictive cardiomyopathy and constrictive pericarditis will be reviewed along with echocardiographic and Doppler features that help to distinguish these two entities.

Sudden adult death: a medico-legal series of 77 cases between 1995 and 2000

Among all the autopsies performed between 1995 and 2000 in our Department, 77 adult cases of sudden death were selected. Sex, age, place of death, circumstances of death, causes of death and heart weight were reported from these 77 post-mortem records. A complete forensic autopsy was performed in every case. Sudden death occurred more frequently in males at rest. Strenuous activity was rarely involved in sudden death and 72.7% of the cases died from cardiovascular disease, mainly coronary atherosclerosis. Non-cardiac causes were dominated by pulmonary and neurological diseases. Cardiomegaly was a frequent finding in cases who died from cardiac pathology. This study underlines the importance of complete medico-legal investigations in case of sudden death. Multiple heart samples are required in order to detect focal microscopic lesions, such as myocarditis and some forms of cardiomyopathy with minimal gross abnormalities. The post-mortem diagnosis of such cardiomyopathies is very important because the family of the deceased may undergo a possible screening. Toxicology is useful in the diagnosis of epileptic seizure and in identifying drugs like metamphetamine as a risk factor for some lethal cardiovascular pathologies such as aortic dissection. Molecular biology can also be helpful when limits of morphological diagnosis have been reached.

Use of implantable cardioverter-defibrillators in pediatric patients

Automatic implantable cardioverter-defibrillator use has become widespread in the prevention of sudden death in at-risk populations. The compelling safety and efficacy data in numerous large, blinded trials on adult patients have led to increasing use of these devices in pediatric patients. Although there are no prospective data to support device therapy in pediatric patients, several large, retrospective studies suggest that pediatric patients are likely to enjoy the same reduction in mortality as adult patients, with a slightly higher rate of complications from the device implant. Data on the use of these devices in pediatric patients for several different indications exist but are limited to retrospective reviews with small numbers and short follow-up. Large prospective trials are needed to assess the safety and efficacy of these devices in children and the influence of implant technique, patient growth, and programmed parameters on overall outcome.

The prevention of sudden death in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a familial myocardial disease caused by mutations in cardiac sarcomeric proteins. HCM is characterised by myocyte disarray and myocardial fibrosis. Most patients are largely asymptomatic but some are prone to a number of disease-related complications, the most problematic of which is sudden cardiac death. Diagnosing patients who are at risk has not been easy because of the clinical heterogeneity of the disease, the frequent absence of symptoms prior to sudden cardiac death and the relatively low disease prevalence and annual mortality rates. To date, both low-dose amiodarone and internal cardioverter/defibrillator implantation have been advocated in high-risk individuals. Further improvements in clinical understanding and risk stratification are necessary to identify HCM patients who are at high risk of sudden death.

Hypertrophic cardiomyopathy: management issues in the new millennium

Hypertrophic cardiomyopathy is an inherited cardiac disorder. Sudden cardiac death frequently occurs in otherwise healthy individuals, and accounts for nearly 35% of all sudden deaths within this age group. Although symptoms occur commonly, they often go unreported. Despite this, a degree of functional limitation is often seen on objective assessment. Management of hypertrophic cardiomyopathy is aimed at relieving symptoms, identifying and treating those individuals at increased risk of sudden death, and screening family members.

Optimal range for parvalbumin as relaxing agent in adult cardiac myocytes: gene transfer and mathematical modeling

Parvalbumin (PV) has recently been shown to increase the relaxation rate when expressed in intact isolated cardiac myocytes via adenovirus gene transfer. We report here a combined experimental and mathematical modeling approach to determine the dose-response and the sarcomere length (SL) shortening-frequency relationship of PV in adult rat cardiac myocytes in primary culture. The dose-response was obtained experimentally by observing the PV-transduced myocytes at different time points after gene transfer. Calcium transients and unloaded mechanical contractions were measured. The results were as follows. At low estimated [PV] (approximately 0.01 mM), contractile parameters were unchanged; at intermediate [PV], relaxation rate of the mechanical contraction and the decay rate of the calcium transient increased with little effects on amplitude; and at high [PV] (approximately 0.1 mM), relaxation rate was further increased, but the amplitudes of the mechanical contraction and the calcium transient were diminished when compared with control myocytes. The SL shortening-frequency relationship exhibited a biphasic response to increasing stimulus frequency in controls (decrease in amplitude and re-lengthening time from 0.2 to 1.0 Hz followed by an increase in these parameters from 2.0 to 4.0 Hz). The effect of PV was to flatten this frequency response. This flattening effect was partly explained by a reduction in the variation in fractional binding of PV to calcium during beats at high frequency. In conclusion, experimental results and mathematical modeling indicate that there is an optimal PV range for which relaxation rate is increased with little effect on contractile amplitude and that PV effectiveness decreases as the stimulus frequency increases.

Risk stratification and prevention of sudden death in hypertrophic cardiomyopathy

Sudden unexpected death, often occurring in young, asymptomatic patients, is the most devastating facet of the natural history of hypertrophic cardiomyopathy, and appears to be the consequence of primary ventricular tachyarrhythmias arising in an electrically unstable myocardial substrate characterized by disorganized cellular architecture, ischemia, cell death, and replacement scarring. Although precise identification of all hypertrophic cardiomyopathy patients at high risk for a catastrophic event is a clinical challenge, effective treatment strategies for the prevention of sudden death with the implantable cardioverter-defibrillator are now available.

Cardiomiopatia hipertrófica, atividade física e morte súbita

A morte súbita em atletas é um evento dramático e tem sido demonstrado que, na maioria das vezes, se deve a doenças cardiovasculares congênitas ou adquiridas. O objetivo deste artigo é abordar alguns aspectos da cardiomiopatia hipertrófica, que é a principal causa de morte súbita em atletas jovens, e sugerir medidas para prevenir essa condição.

Angiotensin II type 2 receptors and cardiac hypertrophy in women with hypertrophic cardiomyopathy

The development of left ventricular hypertrophy in subjects with hypertrophic cardiomyopathy (HCM) is variable, suggesting a role for modifying factors such as angiotensin II. Angiotensin II mediates both trophic and antitrophic effects, via angiotensin II type 1 (AT(1)-R) and angiotensin II type 2 (AT(2)-R) receptors, respectively. Here we investigated the effect of the AT(2)-R gene A/C(3123) polymorphism, located in the 3' untranslated region of exon 3, on left ventricular mass index (LVMI) in 103 genetically independent subjects with HCM (age, 12 to 81 years). LVMI and interventricular septum thickness were determined by 2D echocardiography. Extent of hypertrophy was quantified by a point score (Wigle score). Plasma prorenin, renin, and ACE were determined by immunoradiometric or fluorometric assays, and genotyping was performed by polymerase chain reaction. In men, no associations between AT(2)-R genotype and any of the measured parameters were observed, whereas in women, LVMI decreased with the number of C alleles (211+/-19, 201+/-18, and 152+/-10 g/m(2) in women with the AA, AC, and CC genotype, respectively; P=0.015). Similar C allele-related decreases in women were observed for interventricular septum thickness (P=0.13), Wigle score (P=0.05), plasma renin (P=0.03), and plasma prorenin (P=0.26). Multiple regression analysis revealed that the AT(2)-R C allele-related effect on LVMI (beta=-30.7+/-11.1, P=0.010) occurred independently of plasma renin, the AT(1)-R gene A/C(1166) polymorphism, or the ACE gene I/D polymorphism. In conclusion, AT(2)-Rs modulate cardiac hypertrophy in women with HCM, independently of the circulating renin-angiotensin system. These data support the contention that AT(2)-Rs mediate antitrophic effects in humans.

The implantable cardioverter-defibrillator: does everybody need one?

The implantable cardioverter-defibrillator (ICD) has emerged as an effective, but expensive, therapy for arrhythmic sudden cardiac death. ICD use has been increasing by 20% to 30% per year. Clinical trials have shown that the ICD can be effective for both the primary prevention and the secondary prevention of sudden cardiac death in selected populations. Despite the available trial evidence, several issues pertaining to ICD use remain unresolved, including the treatment of patients not represented in clinical trials, the optimal selection of patients who will benefit from an ICD, the duration of benefit from an ICD, the quality of life for patients with an ICD, and both the cost-effectiveness and the cost impact of the ICD. These considerations are discussed in this article.

Acute effect of human cardiotrophin-1 on hemodynamic parameters in spontaneously hypertensive rats and Wistar Kyoto rats

There is considerable evidence to indicate that humoral factors play an important role in the development of left ventricular hypertrophy. Cardiotrophin-1 (CT-1) is a cytokine that has been shown to induce cardiac hypertrophy in a dose-dependent manner. The aim of the present study was to investigate the acute effect of CT-1 on hemodynamic parameters in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) and to study the relationship between the plasma concentration of CT-1 and its hemodynamic effect. Ten-week-old SHR and age-matched WKY were used. Blood pressure (BP), heart rate (HR) and plasma concentration of CT-1 were measured both before and for 60 min after intravenous bolus injection of human CT-1 (10 microg/kg). CT-1 injection significantly decreased BP and significantly increased HR in SHR and WKY. There were significant differences in BP and HR between the two groups at all time points after injection. The lowest BP, highest HR and maximal plasma concentrations of CT-1 were observed in both groups within 10 min after injection. However, after converting the values into the percentage change from their respective baselines, there were no significant differences between the two groups in BP or HR at any time point. There was also no significant difference between the two groups at any time point in the plasma concentration of CT-1. This study indicates that CT-1 decreases BP and increases HR in both SHR and WKY. The most obvious change occurred within 10 min after injection. However, there was no significant difference in the hypotensive effect of CT-1 on 10-week-old SHR and WKY.

Morbidity of severe obesity

Although obesity is an easy diagnosis to make, its etiologies, pathophysiology, and symptomatology are extraordinarily complex. Progress in surgical technique and anesthesiological management has substantially improved the safety of performing operations on the severely obese in the last 20 years. These improvements have occurred more or less empirically, without a full understanding of etiology or pathophysiology, although this has advanced concomitantly with improvements in practice. This review has attempted to provide a framework to facilitate progress in the neglected areas of patient selection and choice of operation, in an effort to improve long-term outcome. Despite the disparate etiologies of obesity and its diverse comorbidities and complications, there are unifying interdependent pathogenetic mechanisms of great relevance to the practice of antiobesity surgery. The rate of eating, whether driven by HPA dysfunction, ambient stress, or related hereditary susceptibility factors including the increased energy demands of an expanded body fat mass, participates in a cycle that results in disordered satiety (see Fig. 3). This leads to substrate overload, causing extensive metabolic abnormalities such as atherogenesis, insulin resistance, thrombogenesis, and carcinogenesis. This interpretation of the pathophysiology of obesity ironically accords with the original meaning of the word obesity: "to overeat." The ultimate solution to the problem of obesity--preventing it--will not be forthcoming until the food industry is forced to lower production and change its marketing strategies, as the liquor and tobacco industries in the United States were compelled to do. This cannot occur until the large and fast-growing populations of industrialized nations become educated in the personal implications of the energy principle. Regardless of whether school curricula are modified to prioritize health education, the larger problems of cultural and economic change remain for the groups most susceptible to obesity. In this context, antiobesity surgery will continue to thrive, especially in the absence of effective alternatives.

Hypertrophic cardiomyopathy: histopathological features of sudden death in cardiac troponin T disease

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) are at increased risk of premature death; this is particularly apparent for patients with mutations of the troponin T gene. Myocyte disarray and interstitial fibrosis, pathological features of HCM, may be determinants in these deaths. The relation between genotype, pathological phenotype, and mode of death has not been explored.

METHODS AND RESULTS

Seventy-five hearts with HCM were examined. DNA was available in 50 for screening of the troponin T gene. The macroscopic findings, percentage of disarray, percentage of fibrosis, and percentage of small-vessel disease were correlated with the genotype. A troponin T mutation was identified in 9 of the 50 patients, 8 of whom died suddenly. Patients with a troponin T mutation were younger (mean age, 21.0 years [range, 6 to 37] versus 39.1 years [range, 14 to 72]; P<0.0001), had more sudden death (P=0.02), and had lower heart weights, less fibrosis, and greater disarray than other HCM patients (mean heart weight, 380.3+/-105.4 versus 585.0+/-245.7 g, P=0.002; mean fibrosis, 0.7+/-0.4% versus 2.6+/-2.8%, P=0.001; mean disarray, 46.2+/-7.2% versus 24.1+/-15.9%, P<0.0001; and mean small-vessel disease, 11.7+/-14.6 versus 14.1+/-8.7, P=0.6, respectively). Similarly, patients with troponin T mutations who died suddenly had lower heart weights and greater disarray than patients who died suddenly with unknown genotype (ie, troponin T mutation excluded) (mean heart weight, 429.8+/-75.4 versus 559.6+/-204.43 g, P=0.04, and mean disarray, 40.1+/-9.4% versus 20.2+/-12.6%, P=0.002, respectively).

CONCLUSIONS

Patients with troponin T mutations had severe disarray, with only mild hypertrophy and fibrosis. These patients died suddenly and at an especially early age. We propose that extensive myocyte disarray in the absence of marked hypertrophy is the pathological substrate for sudden death in these patients.

Evaluation and treatment of syncope in infants

Syncope in the infant and newborn occurs as a loss of consciousness due to a variety of etiologies. Because syncope at this age may be a harbinger of sudden infant death, the symptom provokes anxiety and challenges clinicians to identify those babies with an increased risk for life threatening events. Recently introduced diagnostic tests and advances in molecular biology offer promising potential, but the population at risk remains unknown. Controversy surrounds: many potential risk factors; the value of home monitoring; and appropriate preventive and therapeutic strategies. This article reviews the differential diagnosis of syncope in children less than 18 months of age, with particular attention to those diagnoses and problems specific to the evaluation and treatment in this age group. Recommendations are presented for an efficient evaluation, which must include a careful history, complete physical examination and thorough investigation of the family history and home environment. In addition, specific diagnostic tests and a practical approach to treatment are suggested.

Development of left ventricular hypertrophy in adults in hypertrophic cardiomyopathy caused by cardiac myosin-binding protein C gene mutations

OBJECTIVES

We sought to determine whether the development of left ventricular hypertrophy (LVH) can be demonstrated during adulthood in genetically affected relatives with hypertrophic cardiomyopathy (HCM).

BACKGROUND

Hypertrophic cardiomyopathy is a heterogeneous cardiac disease caused by mutations in nine genes that encode proteins of the sarcomere. Mutations in cardiac myosin-binding protein C (MyBPC) gene have been associated with age-related penetrance.

METHODS

To further analyze dormancy of LVH in patients with HCM, we studied, using echocardiography and 12-lead electrocardiography, the phenotypic expression caused by MyBPC mutations in seven genotyped pedigrees.

RESULTS

Of 119 family members studied, 61 were identified with a MyBPC mutation, including 21 genetically affected relatives (34%) who did not express the HCM morphologic phenotype (by virtue of showing normal left ventricular wall thickness). Of these 21 phenotype-negative individuals, 9 were children, presumably in the prehypertrophic phase, and 12 were adults. Of the 12 adults with normal wall thickness < or = 12 mm (7 also with normal electrocardiograms), 5 subsequently underwent serial echocardiography prospectively over four to six years. Of note, three of these five adults showed development of LVH in mid-life, appearing for the first time at 33, 34 and 42 years of age, respectively, not associated with outflow obstruction or significant symptoms.

CONCLUSIONS

In adults with HCM, disease-causing MyBPC mutations are not uncommonly associated with absence of LVH on echocardiogram. Delayed remodeling with the development of LVH appearing de novo in adulthood, demonstrated here for the first time in individual patients with prospectively obtained serial echocardiograms, substantiates the principle of age-related penetrance for MyBPC mutations in HCM. These observations alter prevailing perceptions regarding the HCM clinical spectrum and family screening strategies and further characterize the evolution of LVH in this disease.

Sudden cardiac death with clozapine and sertraline combination

OBJECTIVE

To report a case of sudden cardiac death in a patient receiving combination therapy with clozapine and sertraline.

CASE SUMMARY

A 26-year-old white man was discovered dead at his residence. His medical history included chronic paranoid schizophrenia, obsessive-compulsive disorder, major depressive disorder, obstructive sleep apnea, and akathisia. He had no prior history of cardiovascular disease. His medication regimen included clozapine 100 mg twice daily (started 4 y prior to his death), risperidone 3 mg twice daily, sertraline 200 mg once daily, atenolol 50 mg twice daily, and lorazepam 0.5 mg four times daily. Autopsy and toxicology studies revealed cardiomegaly suggestive of idiopathic cardiomyopathy, single-vessel coronary artery disease, sertraline and clozapine blood concentrations in the expected range, undetectable lorazepam and risperidone blood concentrations, obesity, and moderate fatty changes to the liver. The most likely cause of death was sudden cardiac death due to acute cardiac arrhythmia.

DISCUSSION

Clozapine is structurally similar to the tricyclic antidepressants, which have type 1 A antiarrhythmic properties. Case reports have described electrocardiographic abnomalities, cardiomyopathy, and fatal myocarditis associated with its use. Unexplained death in patients on clozapine therapy has also been reported. Sertraline appears to have less cardiac effect; however, one report has observed clinically significant QT prolongation during sertraline therapy.

CONCLUSIONS

Clozapine-induced cardiomyopathy and cardiac arrhythmia from clozapine and/or sertraline use may have contributed to this man's death.

The molecular genetic basis for hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM), a relatively common disease, is diagnosed clinically by unexplained cardiac hypertrophy and pathologically by myocyte hypertrophy, disarray, and interstitial fibrosis. HCM is the most common cause of sudden cardiac death (SCD) in the young and a major cause of morbidity and mortality in elderly. Hypertrophy and fibrosis are the major determinants of morbidity and SCD. More than 100 mutations in nine genes, all encoding sarcomeric proteins have been identified in patients with HCM, which had led to the notion that HCM is a disease of contractile sarcomeric proteins. The beta -myosin heavy chain (MyHC), cardiac troponin T (cTnT) and myosin binding protein-C (MyBP-C) are the most common genes accounting for approximately 2/3 of all HCM cases. Genotype-phenotype correlation studies suggest that mutations in the beta -MyHC gene are associated with more extensive hypertrophy and a higher risk of SCD as compared to mutations in genes coding for other sarcomeric proteins, such as MyBP-C and cTnT. The prognostic significance of mutations is related to their hypertrophic expressivity and penetrance, with the exception of those in the cTnT, which are associated with mild hypertrophic response and a high incidence of SCD. However, there is a significant variability and factors, such as modifier genes and probably the environmental factors affect the phenotypic expression of HCM. The molecular pathogenesis of HCM is not completely understood. In vitro and in vivo studies suggest that mutations impart a diverse array of functional defects including reduced ATPase activity of myosin, acto-myosin interaction, cross-bridging kinetics, myocyte contractility, and altered Ca2+ sensitivity. Hypertrophy and other clinical and pathological phenotypes are considered compensatory phenotypes secondary to functional defects. In summary, the molecular genetic basis of HCM has been identified, which affords the opportunity to delineate its pathogenesis. Understanding the pathogenesis of HCM could provide for genetic based diagnosis, risk stratification, treatment and prevention of cardiac phenotypes.

Regression of left ventricular hypertrophy after nonsurgical septal reduction therapy for hypertrophic obstructive cardiomyopathy

BACKGROUND

Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by left ventricular hypertrophy (LVH) in the absence of increased external load. Recently, nonsurgical septal reduction therapy (NSRT) with intracoronary ethanol has been introduced to treat severely symptomatic patients with outflow tract obstruction. Its long-term effects on LV mass, however, are unknown.

METHODS AND RESULTS

The LV size, function, and outflow tract gradient of 26 HOCM patients (53+/-15 years old) who underwent NSRT were assessed by echocardiography at baseline and 1 and 2 years after the procedure. LVH was evaluated by wall thickness of individual myocardial segments, planimetered myocardial area, and mass. The outflow gradient decreased from 36+/-6 mm Hg before NSRT to 0+/-3 mm Hg at 2 years (P<0.001), with patients experiencing symptomatic improvement (P<0.05). LV end-diastolic and end-systolic dimensions increased significantly at both 1 and 2 years (P<0.001). All parameters of LVH showed evidence of regression. LV mass decreased (301+/-78 g at baseline, 223+/-5 g at 1 year, and 190+/-58 g at 2 years; P<0.01), with the 2-year reduction in mass related to infarct size and the acute reduction in outflow tract gradient (r=0.48, P<0.05 and r=0.63, P<0.01, respectively).

CONCLUSIONS

NSRT results in LV remodeling that is characterized by an increase in LV size and a decrease in the extent of LVH.

Value of exercise testing in assessing clinical state and prognosis in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the sarcomeric contractile proteins. A majority of patients with HCM are limited in terms of functional capacity, and a minority of these patients die suddenly. The main aims of management are symptom alleviation and prevention of sudden cardiac death. In patients with HCM, cardiopulmonary exercise testing provides a much more accurate index of functional capacity than New York Heart Association classification status, and it is useful in assessing symptoms after various therapeutic strategies have been implemented. Exercise testing is also valuable in identifying patients with HCM who are at high risk of sudden cardiac death and is an integral part of the algorithm in risk stratification and delivery of prophylactic therapy. Also, cardiopulmonary exercise testing plays an important role in differentiating HCM from other conditions associated with left ventricular hypertrophy, such as physiologic athlete's heart. Therefore, during the last few years, cardiopulmonary exercise testing has provided insights into the diagnosis, determinants, and mechanisms of exercise limitation in HCM. This understanding aids physicians in targeting therapy and developing new treatment modalities.

The role of exercise testing in the evaluation of the patient with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the sarcomeric contractile proteins that is characterized by left ventricular hypertrophy and myocyte disarray. The majority of patients are limited in terms of functional capacity and a minority die suddenly. The main aims of management are symptom alleviation and prevention of sudden cardiac death. In patients with HCM, cardiopulmonary exercise testing provides a more accurate index of functional capacity than New York Heart Association classification status and is useful in assessing symptoms following various therapeutic interventions. Cardiopulmonary exercise testing plays an important role in differentiating HCM from other conditions associated with left ventricular hypertrophy. Cardiopulmonary exercise testing is also valuable in identifying individuals at high risk of sudden cardiac death and is an integral part of the algorithm in risk stratification and delivery of prophylactic therapy. Over the past few years, cardiopulmonary exercise testing has provided insight into the determinants and mechanisms of exercise limitation. This understanding helps in targeting therapy and the development of new treatment modalities.

Angiotensin II blockade reverses myocardial fibrosis in a transgenic mouse model of human hypertrophic cardiomyopathy

BACKGROUND

-Hypertrophic cardiomyopathy (HCM), the most common cause of sudden cardiac death in the young, is characterized by cardiac hypertrophy, myocyte disarray, and interstitial fibrosis. We propose that hypertrophy and fibrosis are secondary to the activation of trophic and mitotic factors and, thus, potentially reversible. We determined whether the blockade of angiotensin II, a known cardiotrophic factor, could reverse or attenuate interstitial fibrosis in a transgenic mouse model of human HCM.

METHODS AND RESULTS

We randomized 24 adult cardiac troponin T (cTnT-Q(92)) mice, which exhibit myocyte disarray and interstitial fibrosis, to treatment with losartan or placebo and included 12 nontransgenic mice as controls. The mean dose of losartan and the mean duration of therapy were 14.2+/-5.3 mg. kg(-1). d(-1) and 42+/-9.6 days, respectively. Mean age, number of males and females, and heart/body weight ratio were similar in the groups. Collagen volume fraction and extent of myocyte disarray were increased in the cTnT-Q(92) mice (placebo group) compared with nontransgenic mice (9.9+/-6.8% versus 4.5+/-2.2%, P=0.01, and 27.6+/-10.6% versus 3.9+/-2.3%, P<0.001, respectively). Treatment with losartan reduced collagen volume fraction by 49% to 4.9+/-2.9%. The expression of collagen 1alpha (I) and transforming growth factor-beta1, a mediator of angiotensin II profibrotic effect, were also reduced by 50%. Losartan had no effect on myocyte disarray.

CONCLUSIONS

Treatment with losartan reversed interstitial fibrosis and the expression of collagen 1alpha (I) and transforming growth factor-beta1 in the hearts of cTnT-Q(92) mice. These findings suggest that losartan has the potential to reverse or attenuate interstitial fibrosis, a major predictor of sudden cardiac death, in human patients with HCM.

Relation between severity of left-ventricular hypertrophy and prognosis in patients with hypertrophic cardiomyopathy

BACKGROUND

A previous study suggested that severe left-ventricular hypertrophy (maximum wall thickness > or = 30 mm) in patients with hypertrophic cardiomyopathy is associated with a risk of sudden cardiac death sufficient to warrant consideration for implantation of a cardioverter defibrillator (ICD). However, the prognostic significance of left-ventricular hypertrophy in relation to other clinical risk factors is poorly characterised.

METHODS

We studied 630 patients consecutively referred to one hospital in London, UK (mean age 37 years [SD 16]; 382 male; mean follow-up 59 months). Patients underwent two-dimensional and doppler echocardiography, upright exercise testing, and Holter monitoring.

FINDINGS

39 patients died suddenly or had an appropriate ICD discharge; nine died from progressive heart failure; 11 from other cardiovascular causes and 23 from non-cardiac causes. There was a trend towards higher probability of sudden death or ICD discharge with increasing wall thickness (p=0.029, relative risk per 5 mm increment 1.31 [95% CI 1.03-1.66]). Of the 39 patients who died suddenly or had an ICD discharge, ten had a wall thickness of 30 mm or more. Patients with wall thickness of 30 mm or more had higher probability of sudden death or ICD discharge than patients with wall thickness less than 30 mm (p=0.049, 2.07 [1.00-4.25]. When considered together, the number of additional risk factors (one to three) was a better predictor of risk of sudden death or ICD discharge than wall thickness (p=0.0001, relative risk per additional factor 2.00 [1.43-2.79] vs p=0.058, 1.26 per 5 mm increment [0.99-1.60]). There was no relation between the pattern of hypertrophy and survival.

INTERPRETATION

The risk of sudden death associated with a wall thickness of 30 mm or more in patients without other risk factors is insufficient to justify aggressive prophylactic therapy. Most sudden deaths occurred in patients with wall thickness less than 30 mm, so the presence of mild hypertrophy cannot be used to reassure patients that they are at low risk.

Clinical and echocardiographic features of hypertrophic cardiomyopathy in the elderly

Hypertrophic cardiomyopathy is a familial cardiac disease with exceptionally diverse clinical and morphologic presentations. The influence of age on the disease manifestation has become increasingly clear over the last decade. Most initial reports concentrated on characterization and treatment of the disease in younger individuals, but a better appreciation of hypertrophic cardiomyopathy in elderly patients has yielded important information regarding clinical presentation, morphologic appearance on echocardiography, prognosis, and management. This paper reviews the literature focusing on the age-related differences in hypertrophic cardiomyopathy.

Ventricular arrhythmias in the athlete

Life-threatening ventricular arrhythmias in the athlete nearly always occur in the presence of structural heart disease. In the last few years, 2 new causes of life-threatening arrhythmias have been described in patients with normal hearts-that of the Brugada syndrome and that of commotio cordis. Non-life-threatening premature ventricular beats and even nonsustained ventricular tachycardia are not rare, and although usually benign, can be secondary to cardiomyopathies. Athletes with symptoms of syncope, especially if exertional, warrant a complete evaluation. The treatment of athletes and other individuals with life-threatening ventricular arrhythmias has been revolutionized by the implantable cardioverter defibrillator, a device that affords excellent protection from sudden death. Defining those athletes who would benefit from the implantable defibrillator is not always clear. Furthermore, participation in competitive athletics for athletes with life-threatening arrhythmias or structural heart disease known to put the athlete at risk for life-threatening arrhythmias is usually prohibited.

Attaining long-term survival when treating diabetic patients with ESRD by hemodialysis

Diabetic nephropathy is the most common cause of end-stage renal disease (ESRD). The United States Renal Data System's report indicates that survival of diabetic patients has improved but continues to be reduced compared with that of nondiabetic patients. Several ways to decrease morbidity and mortality in diabetic patients are discussed: (1) Instructions and treatment in the predialysis period markedly influence compliance of patients, and this plays a determinant role in development and progression of diabetic complications before and during maintenance hemodialysis. (2) After the start of hemodialysis therapy, insulin therapy must be adjusted and respect impaired glucose use and prolongation of insulin half-life. (3) By avoiding of puncture of veins prospectively used for arteriovenous fistulae and timely installation of the fistulae, native arteriovenous fistulae can be achieved in more than 70% of diabetic patients. (4) Hypertension, left ventricular hypertrophy, and cardiovascular problems commonly found in diabetic patients require optimal removal of fluid overload. This is difficult to achieve in the presence of accelerated arteriosclerosis and autonomic polyneuropathy in diabetic patients and requires long and smooth dialysis procedures. (5) Infected necroses caused by diabetic polyneuropathy and peripheral vascular disease require appropriate therapy by experienced nephrologists and surgeons.