Syncope in hypertrophic cardiomyopathy: multivariate analysis of prognostic determinants

Syncope in hypertrophic cardiomyopathy (part I): An updated systematic review and meta-analysis

AIMS

To describe the proportion of patients with syncope among those affected by hypertrophic cardiomyopathy (HCM) and the relevance of syncope as risk factor for sudden cardiac death and life-threatening arrhythmic events.

METHOD AND RESULTS

Systematic review of original articles that assessed syncope in HCM patients. Literature search of PubMed including all English publications from 1973 to 2021.We found 57 articles for a total of 21.791 patients; of these, 14 studies reported on arrhythmic events in the follow-up. Syncope was reported in 15.8% (3.452 of 21.791) patients. It was considered unexplained in 91% of cases. Life-threatening arrhythmic events occurred in 3.6% of non-syncopal patients and in 7.7% of syncopal patients during a mean follow-up of 5.6 years. A relative risk of 1.99 (95%CI 1.39 to 2.86) was estimated for syncope patients by the random effect model using Haldane continuity correction for 0 events.

CONCLUSIONS

In the current practice, the cause of syncope remained unexplained in most patients affected by HCM. The management of patients seems mainly driven by risk stratification rather than identification of the aetiology of syncope. There is a need of precise instructions how to apply the recommendations of current guidelines to this disease, which tests are indicated and how to interpret their findings. The protocol was registered in Prospero (ID: 275963).

Cardiomyopathies: An Overview

Background: Cardiomyopathies are a heterogeneous group of pathologies characterized by structural and functional alterations of the heart. Aims: The purpose of this narrative review is to focus on the most important cardiomyopathies and their epidemiology, diagnosis, and management. Methods: Clinical trials were identified by Pubmed until 30 March 2021. The search keywords were “cardiomyopathies, sudden cardiac arrest, dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy, arrhythmogenic cardiomyopathy (ARCV), takotsubo syndrome”. Results: Hypertrophic cardiomyopathy (HCM) is the most common primary cardiomyopathy, with a prevalence of 1:500 persons. Dilated cardiomyopathy (DCM) has a prevalence of 1:2500 and is the leading indication for heart transplantation. Restrictive cardiomyopathy (RCM) is the least common of the major cardiomyopathies, representing 2% to 5% of cases. Arrhythmogenic cardiomyopathy (ARCV) is a pathology characterized by the substitution of the myocardium by fibrofatty tissue. Takotsubo cardiomyopathy is defined as an abrupt onset of left ventricular dysfunction in response to severe emotional or physiologic stress. Conclusion: In particular, it has been reported that HCM is the most important cause of sudden death on the athletic field in the United States. It is needless to say how important it is to know which changes in the heart due to physical activity are normal, and when they are pathological.

Reversed Septal Curvature Is Associated with Elevated Troponin Level in Hypertrophic Cardiomyopathy

The aim of study was to compare patients with hypertrophic cardiomyopathy divided according to septal configuration assessed in a 4-chamber apical window. The study group consisted of 56 consecutive patients. Reversed septal curvature (RSC) and non-RSC were diagnosed in 17 (30.4%) and 39 (69.6%) patients, respectively. Both RSC and non-RSC groups were compared in terms of the level of high-sensitivity troponin I (hs-TnI), NT-proBNP (absolute value), NT-proBNP/ULN (value normalized for sex and age), and echocardiographic parameters, including left ventricular outflow tract gradient (LVOTG). A higher level of hs-TnI was observed in RSC patients as compared to the non-RSC group (102 (29.2-214.7) vs. 8.7 (5.3-18) (ng/l), p = 0.001). A trend toward increased NT-proBNP value was reported in RSC patients (1279 (367.3-1186) vs. 551.7 (273-969) (pg/ml), p = 0.056). However, no difference in the NT-proBNP/ULN level between both groups was observed. Provocable LVOTG was higher in RSC as compared to non-RSC patients (51 (9.5-105) vs. 13.6 (7.5-31) (mmHg), p = 0.04). Furthermore, more patients with RSC had prognostically unfavourable increased septal thickness to left LV diameter at the end diastole ratio. Patients with RSC were associated with an increased level of hs-TnI, and the only trend observed in this group was for the higher NT-proBNP levels. RSC seems to be an alerting factor for the risk of ischemic events. Not resting but only provocable LVOTG was higher in RSC as compared to non-RSC patients.

Takotsubo Cardiomyopathy in a Patient with Preexisting Hypertrophic Cardiomyopathy

Takotsubo cardiomyopathy (TCM) is a condition characterized by transient left ventricular dysfunction and apical ballooning, best seen on an echocardiogram or left ventriculogram. It mimics acute myocardial infarction but without evidence of coronary artery disease on an angiogram. Hypertrophic cardiomyopathy (HCM) is an autosomal dominant heart muscle disease that is significant with hypertrophy of the left ventricle with various morphologies. We hereby report a case of TCM in a male patient with a known history of HCM. The patient's hemodynamic findings were challenging because the TCM produced an increased left ventricular outflow tract (LVOT) gradient that was previously not seen on his prior echocardiogram or cardiac catheterizations. Assessment and continuous monitoring are warranted in such a rare case. Supportive care afterward with beta blockers, along with echocardiogram surveillance, are the mainstay of management of such a patient.

Syncope and the risk of sudden cardiac death: Evaluation, management, and prevention

Syncope is a clinical syndrome defined as a relatively brief self-limited transient loss of consciousness (TLOC) caused by a period of inadequate cerebral nutrient flow. Most often the trigger is an abrupt drop of systemic blood pressure. True syncope must be distinguished from other common non-syncope conditions in which real or apparent TLOC may occur such as seizures, concussions, or accidental falls. The causes of syncope are diverse, but in most instances, are relatively benign (e.g., reflex and orthostatic faints) with the main risks being accidents and/or injury. However, in some instances, syncope may be due to more worrisome conditions (particularly those associated with cardiac structural disease or channelopathies); in such circumstances, syncope may be an indicator of increased morbidity and mortality risk, including sudden cardiac death (SCD). Establishing an accurate basis for the etiology of syncope is crucial in order to initiate effective therapy. In this review, we focus primarily on the causes of syncope that are associated with increased SCD risk (i.e., sudden arrhythmic cardiac death), and the management of these patients. In addition, we discuss the limitations of our understanding of SCD in relation to syncope, and propose future studies that may ultimately address how to improve outcomes of syncope patients and reduce SCD risk.

Hypertrophic Cardiomyopathy: Genetics, Pathogenesis, Clinical Manifestations, Diagnosis, and Therapy

Hypertrophic cardiomyopathy (HCM) is a genetic disorder that is characterized by left ventricular hypertrophy unexplained by secondary causes and a nondilated left ventricle with preserved or increased ejection fraction. It is commonly asymmetrical with the most severe hypertrophy involving the basal interventricular septum. Left ventricular outflow tract obstruction is present at rest in about one third of the patients and can be provoked in another third. The histological features of HCM include myocyte hypertrophy and disarray, as well as interstitial fibrosis. The hypertrophy is also frequently associated with left ventricular diastolic dysfunction. In the majority of patients, HCM has a relatively benign course. However, HCM is also an important cause of sudden cardiac death, particularly in adolescents and young adults. Nonsustained ventricular tachycardia, syncope, a family history of sudden cardiac death, and severe cardiac hypertrophy are major risk factors for sudden cardiac death. This complication can usually be averted by implantation of a cardioverter-defibrillator in appropriate high-risk patients. Atrial fibrillation is also a common complication and is not well tolerated. Mutations in over a dozen genes encoding sarcomere-associated proteins cause HCM. MYH7 and MYBPC3, encoding β-myosin heavy chain and myosin-binding protein C, respectively, are the 2 most common genes involved, together accounting for ≈50% of the HCM families. In ≈40% of HCM patients, the causal genes remain to be identified. Mutations in genes responsible for storage diseases also cause a phenotype resembling HCM (genocopy or phenocopy). The routine applications of genetic testing and preclinical identification of family members represents an important advance. The genetic discoveries have enhanced understanding of the molecular pathogenesis of HCM and have stimulated efforts designed to identify new therapeutic agents.

Genetics and Genomics of Single-Gene Cardiovascular Diseases: Common Hereditary Cardiomyopathies as Prototypes of Single-Gene Disorders

This is the first of 2 review papers on genetics and genomics appearing as part of the series on "omics." Genomics pertains to all components of an organism's genes, whereas genetics involves analysis of a specific gene or genes in the context of heredity. The paper provides introductory comments, describes the basis of human genetic diversity, and addresses the phenotypic consequences of genetic variants. Rare variants with large effect sizes are responsible for single-gene disorders, whereas complex polygenic diseases are typically due to multiple genetic variants, each exerting a modest effect size. To illustrate the clinical implications of genetic variants with large effect sizes, 3 common forms of hereditary cardiomyopathies are discussed as prototypic examples of single-gene disorders, including their genetics, clinical manifestations, pathogenesis, and treatment. The genetic basis of complex traits is discussed in a separate paper.

Echocardiography Differences Between Athlete's Heart Hearth and Hypertrophic Cardiomyopathy

Introduction:

Among long term athletes there is always present hypertrophy of the left ventricle walls as well as increased cardiac mass. These changes are the result of the heart muscle adaptation to load during the years of training, which should not be considered as pathology. In people suffering from hypertrophic cardiomyopathy (HCM), there is also present hypertrophy of the left ventricle walls and increased mass of the heart, but these changes are the result of pathological changes in the heart caused by a genetic predisposition for the development HCM of. Differences between myocardial hypertrophy in athletes and HCM are not clearly differentiated and there are always dilemmas between pathological and physiological hypertrophy. The goal of the study is to determine and compare the echocardiographic cardiac parameters of longtime athletes to patients with hypertrophic cardiomyopathy.

Material and methods:

The study included 60 subjects divided into two groups: active athletes and people with hypertrophic cardiomyopathy.

Results:

Mean values of IVSd recorded in GB is IVSd=17.5 mm (n=20, 95% CI, 16.00–19.00 mm), while a significantly smaller mean value is recorded in GA, IVSd=10.0 mm (n=40, 95% CI, 9.00-11.00 mm). The mean value of the left ventricle in diastole (LVDd) recorded in the GA is LVDd=51 mm (n=40; 95% CI, 48.00 to 52.00 mm), while in the group with hypertrophic cardiomyopathy (GB) mean LVDd value is 42 mm (n=20; 95% CI, 40.00 to 48.00 mm). The mean value of the rear wall of the left ventricle (LVPWd) recorded in the GA is LVDd=10 mm (n=40; 95% CI, 9.00-10.00 mm) while in the group with hypertrophic cardiomyopathy (GB) mean LVDd is 14 mm (n=20; 95% CI, 12.00 to 16.00 mm). The mean of the left ventricle during systole (LVSD) observed in GA is LVSD=34 mm (n=40; 95% CI, 32.00 to 36.00 mm), while in the group with hypertrophic cardiomyopathy (GB) mean LVSD is 28 mm (n=20; 95% CI, 24.00 to 28.83 mm). The mean ejection fraction (EF%) observed in GA is EF=60% (n=40; 95% CI, 56.41 to 63.00%), while in the group with hypertrophic cardiomyopathy (GB) mean EF value is 69% (n=20; 95% CI, 62.00 to 70.83 mm). Somewhat higher mean diastolic left ventricular function (E/A) was observed in GA, E/A=1.76±0.15, and lower average values in the group with hypertrophic cardiomyopathy: (GB) E/A=0.78±0.02.

Conclusion:

Mean values of parameters intraventricular septum thickness in diastole (IVSd), the thickness of the rear wall of the left ventricle (LVPWd), the diameter of the left ventricle during systole (LVSD) were statistically different between groups of athletes (GA) compared to the group of patients with hypertrophic cardiomyopathy (GB).

Syncope in Patients with Organic Heart Disease

Patients with syncope and organic heart disease remain a small but important subset of those patients who experience transient loss of consciousness. These patients require thoughtful and complete evaluation in an attempt to better understand the mechanism of syncope and its relationship to the underlying disease, and to diagnose and treat both properly. The goal is to reduce the risk of further syncope, to improve long-term outcomes with respect to arrhythmic and total mortality, and to improve patients' quality of life.

Recurrent syncope episodes and exercise intolerance in hypertrophic cardiomyopathy combined with atrioventricular conduction disturbance

A 30-year-old female patient with known hypertrophic cardiomyopathy (HCMP) was admitted for recurrent syncope episodes. Electrocardiogram (ECG) showed 2 : 1 atrioventricular (AV) block. Stress echocardiography with bicycle showed high grade AV block at high stage of the exercise associated with exercise intolerance and dyspnea. Twenty-four hour ECG monitoring also revealed high grade AV block and 1 episode of non-sustained ventricular tachycardia. Implantable cardioverter/defibrillator-pacemaker (ICD-P) was inserted. After implantation of ICD-P, conduction disturbance and exercise intolerance were improved. AV block is a rare complication HCMP. There are just a few case reports that present symptoms caused by conduction disturbance in HCMP. This case describes repeated syncope episodes and exercise intolerance caused by conduction disturbance during exercise in HCMP patient. For evaluating the cause of syncope in HCMP, stress echocardiography can be helpful to understand the probable mechanism of syncope.

Mechanisms of arrhythmias and conduction disorders in older adults

Aging is associated with an increased prevalence of cardiac arrhythmias, which contribute to higher morbidity and mortality in the elderly. The frequency of cardiac arrhythmias, particularly atrial fibrillation and ventricular tachyarrhythmia, is projected to increase as the population ages, greatly impacting health care resource utilization. Several clinical factors associated with the risk of arrhythmias have been identified in the population, yet the molecular bases for the increased predisposition to arrhythmogenesis in the elderly are not fully understood. This review highlights the epidemiology of cardiac dysrhythmias, changes in cardiac structure and function associated with aging, and the basis for arrhythmogenesis in the elderly.

Comparison of surgical septal myectomy to medical therapy alone in patients with hypertrophic cardiomyopathy and syncope

The presence of syncope despite medical therapy in patients with hypertrophic cardiomyopathy (HC) is considered an indication for surgical myectomy; however, no study has examined the long-term effects on recurrent syncope and survival after surgery in these patients. We examined 239 patients with HC and a history of syncope who had undergone surgical myectomy (mean age 48 ± 17 years; 56% men). The patients were age- and gender-matched to patients with HC and syncope who were treated medically without myectomy (mean age 51 ± 16 years; 59% men). The median follow-up period was 4.7 years (0.8, 11.3). The recurrence rate of syncope was 11% in the myectomy patients and 40% in the medical group (p <0.0001). Multiple episodes of syncope, left ventricular outflow tract obstruction, and recent syncope were identified as baseline predictors of recurrent syncope. Survival free of all-cause mortality was greater for patients who had undergone surgical myectomy than for the medically treated patients (10-year estimate 82 ± 4% vs 69 ± 4%; p = 0.01). In conclusion, surgical myectomy in patients with HC and a history of syncope was associated with a reduction in recurrent syncope and increased survival.

Recent advances in genetics and treatment of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an intriguing disease with various clinical manifestations, ranging from sudden cardiac death to heart failure. The molecular genetics of HCM are all but elucidated and over 200 mutations in more than a dozen genes have been identified. Conventional therapeutic agents, namely beta-blockers and calcium channel blockers, could provide symptomatic relief but are not known to reduce mortality or induce regression of phenotype. Studies in genetic animal models suggest cardiac hypertrophy and fibrosis, a major histological feature of HCM, may be reversed or prevented through blockade of molecules involved in the pathogenesis of HCM. Surgical myomectomy and ethanol-induced septal ablation are effective procedures for reducing the left ventricular outflow tract obstruction and hence, symptomatic improvement. Randomized studies are needed to compare the effectiveness of medical therapy, ethanol septal ablation and surgical myomectomy in treatment of patients with HCM.

Hypertrophic cardiomyopathy: from genetics to treatment

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the prototypic form of pathological cardiac hypertrophy. HCM is an important cause of sudden cardiac death in the young and a major cause of morbidity in the elderly.

DESIGN

We discuss the clinical implications of recent advances in the molecular genetics of HCM.

RESULTS

The current diagnosis of HCM is neither adequately sensitive nor specific. Partial elucidation of the molecular genetic basis of HCM has raised interest in genetic-based diagnosis and management. Over a dozen causal genes have been identified. MYH7 and MYBPC3 mutations account for about 50% of cases. The remaining known causal genes are uncommon and some are rare. Advances in DNA sequencing techniques have made genetic screening practical. The difficulty, particularly in the sporadic cases and in small families, is to discern the causal from the non-causal variants. Overall, the causal mutations alone have limited implications in risk stratification and prognostication, as the clinical phenotype arises from complex and often non-linear interactions between various determinants.

CONCLUSIONS

The clinical phenotype of 'HCM' results from mutations in sarcomeric proteins and subsequent activation of multiple cellular constituents including signal transducers. We advocate that HCM, despite its current recognition and management as a single disease entity, involves multiple partially independent mechanisms, despite similarity in the ensuing phenotype. To treat HCM effectively, it is necessary to delineate the underlying fundamental mechanisms that govern the pathogenesis of the phenotype and apply these principles to the treatment of each subset of clinically recognized HCM.

Severe symptoms in mid and apical hypertrophic cardiomyopathy

BACKGROUND

We analyzed the clinical and quantitative echocardiographic characteristics of patients with sub-basal hypertrophic cardiomyopathy (HCM) to define the characteristics of patients (pts) with severe symptoms.

METHODS

Of 444 pts in a referral-based HCM program, 22 (5%) had midventricular or apical HCM. Quality of life (QoL) questionnaire was administered as an independent confirmer of symptomatic state.

RESULTS

Ten pts were NYHA III and IV, and 12 pts were NYHA I and II; QoL scores (41 +/- 26 vs. 10 +/- 13, P = 0.001) confirmed a priori division of two groups based on NYHA classification. Pts with more severe symptoms were more likely female (70% vs. 25%, P = 0.001) with atrial fibrillation (40% vs. 0%, P = 0.02). They more frequently had midventricular HCM 60% versus 8% (P = 0.01) (mid-LV thickness 17 +/- 6 vs. 12 +/- 2 mm, P = 0.03) and had much smaller LV diastolic volumes 68 +/- 12 versus 102 +/- 22 ml (39 +/- 4 vs. 53 +/- 12 ml/m(2), P = 0.001). Septal E/E' was higher in the severely symptomatic pts (15 +/- 5 vs. 7 +/- 3, P = 0.001) indicating higher estimated LV filling pressure. Midobstruction with apical akinetic chamber was noted in 4/10 pts who developed refractory symptoms. Cardiac mortality was higher in the severely symptomatic patients, 4/10 who had midventricular HCM as compared to 0/12 in the mildly symptomatic apical HCM group (P = 0.03).

CONCLUSIONS

In subbasal HCM, pts with severe symptoms have midventricular hypertrophy, with encroachment of the LV cavity and consequent very small LV volumes that may be complicated by mid-LV obstruction. Pts with mid-LV hypertrophy are more symptomatic than those with apical HCM, are often refractory to therapy, and have higher mortality.

Supraventricular arrhythmia induction by an implantable cardioverter defibrillator in a patient with hypertrophic cardiomyopathy

A 23-year-old woman with obstructive hypertrophic cardiomyopathy and history of frequent unexplained syncope had undergone implantable cardioverter defibrillator implantation. She had experienced frequent inappropriate shocks since implantation due to T-wave oversensing. After one of the syncopal attacks, she was found to have an atrioventricular (AV)-reentrant tachycardia, induced by a high-voltage shock, with rapid degeneration to atrial fibrillation and then ventricular fibrillation. The AV-reentrant tachycardia was believed to be the cause of both syncopal attacks and inappropriate shocks. The patient has been asymptomatic after ablation of the accessory pathway. To the best of our knowledge, this is the first report of induction of an AV-reentrant tachycardia by a high-voltage implantable cardioverter defibrillator shock.

Pathophysiology and Treatment of Hypertrophic Cardiomyopathy

All patients with hypertrophic cardiomyopathy (HCM) should have five aspects of care addressed. An attempt should be made to detect the presence or absence of risk factors for sudden arrhythmic death. If the patient appears to be at high risk, discussion of the benefits and risks of ICD are indicated, and many such patients will be implanted. Symptoms are appraised and treated. Bacterial endocarditis prophylaxis is recommended. Patients are advised to avoid athletic competition and extremes of physical exertion. First degree family members should be screened with echocardiography and ECG.

The athleteʼs heart and hypertrophic cardiomyopathy: two conditions which may be misdiagnosed and coexistent. Which parameters should be analysed to distinguish one disease from the other?

According to the statements from the International Cardiological Committees on Eligibility for Sports, athletes with a clinical diagnosis of hypertrophic cardiomyopathy (HCM) should be excluded from most competitive sports, with the possible exception of those of low intensity. Clinical distinctions between physiological athlete's heart and pathological conditions such as HCM have critical implications especially for trained athletes. Even if the standard two-dimensional echocardiography represents an irreplaceable method in the evaluation of cardiac adaptations to physical exercise, the data currently available suggest the usefulness of Doppler myocardial imaging (DMI) in the assessment of the myocardial systolic and diastolic function of the athlete's heart. On this ground, the combined use of standard two-dimensional echocardiography and DMI may be taken into account for a valid, non-invasive and easily repeatable evaluation of both physiological and pathological ventricular hypertrophy, and in selecting a subgroup of HCM patients at higher risk of cardiac events. In particular, DMI analysis in the trained individual has demonstrated an interesting opportunity for: (1) the differential diagnosis from pathological left ventricular hypertrophy due to HCM; (2) the prediction of cardiac performance during physical effort; (3) the evaluation of bi-ventricular interaction; (4) the analysis of myocardial adaptations to various training protocols; and (5) the early identification of specific genotypes associated with cardiomyopathies.

On predictors of sudden cardiac death in hypertrophic cardiomyopathy

The clinical diagnostic hallmark of hypertrophic cardiomyopathy (HCM) is unexplained cardiac hypertrophy, commonly found on an echocardiogram and in unfortunate occasions, in an autopsy. The latter is most tragic as HCM, a relatively common disease (1 ) often presenting with sudden cardiac death (SCD) in apparently healthy young individuals (2 ,3 ). Indeed, HCM is considered the most common cause of SCD in young competitive athletes (2 ). The unexpected SCD of young athletic individuals in conjunction with the results of earlier studies from major referral centers, reporting an annual mortality rate of approximately 2% to 6% (3 –5 ), led to the impression that HCM is a relatively malignant disease. Population-based studies, however, suggested a more benign course with an annual mortality rate of approximately 1% (6 –9 ). In the largest series comprised of 744 patients, the annual mortality rate was 1.2% of which approximately half were sudden unexpected deaths (9 ).

Comparison of hemodynamic adaptation to orthostatic stress in patients with hypertrophic cardiomyopathy with or without syncope and in vasovagal syncope

This study was designed to investigate whether, in patients with hypertrophic cardiomyopathy (HC), tilt-induced volume unloading triggers a peripheral reflex similar to that seen in patients with a history of vasovagal syncope or rather acts through an intrinsic cardiac mechanism secondary to diastolic dysfunction. Thirty-seven patients with HC (10 with and 27 without a history of syncope), 10 patients with vasovagal syncope, and 9 controls underwent 70 degrees head-up tilt for 45 minutes during continuous radionuclide monitoring of left ventricular function. We focused on the initial 5 minutes into the tilt test, well before symptoms occurred, to exclude that the observed hemodynamic changes were the consequence rather than the cause of syncope. HC patients with previous syncope and vasovagal patients experienced significant hypotension after the initial 5 minutes of tilt. Only HC patients with a history of syncope had a significant decrease in cardiac output, which began at the initial stage of the test. Systemic vascular resistance decreased in vasovagal patients, but increased in the HC syncopal group. Baseline peak filling rate was lower (2.4 +/- 0.5 vs 3.3 +/- 1.1 stroke counts/s, p = 0.03) and a "pseudonormal" or a restrictive pattern of left ventricular filling was more frequent (70% vs 26%, p = 0.02) in HC patients with than without a history of syncope. Thus, significant hypotension or frank syncope during orthostatic stress in HC patients with a history of syncope is due to an early decrease in cardiac output, which occurs well before the onset of symptoms; such impaired hemodynamic adaptation seems to be related to diastolic dysfunction.

Common emergent pediatric neurologic problems

Although there are a variety of neurologic disease processes that the emergency physician should be aware of the most common of these include seizures, closed head injury, headache, and syncope. When one is evaluating a patient who has had a seizure, differentiating between febrile seizures, afebrile seizures, and SE helps to determine the extent of the work-up. Febrile seizures are typically benign, although a diagnosis of meningitis must not be missed. Educating parents regarding the likelihood of future seizures, and precautions to be taken should a subsequent seizure be witnessed, is important. The etiology of a first-time afebrile seizure varies with the patient's age at presentation, and this age-specific differential drives the diagnostic work-up. A follow-up EEG is often indicated, and imaging studies can appropriate on a nonurgent basis. Appropriate management of SE requires a paradigm of escalating pharmacologic therapy, and early consideration of transport for pediatric intensive care services if the seizure cannot be controlled with conventional three-tiered therapy. Closed head injury frequently is seen in the pediatric emergency care setting. The absence of specific clinical criteria to guide the need for imaging makes management of these children more difficult. A thorough history and physical examination is important to uncover risk factors that prompt emergent imaging. Headaches are best approached by assessing the temporal course, associated symptoms, and the presence of persistent neurologic signs. Most patients ultimately are diagnosed with either a tension or migraine headache; however, in those patients with a chronic progressive headache course, an intracranial process must be addressed and pursued with appropriate imaging. Syncope has multiple causes but can generally be categorized as autonomic, cardiac, or noncardiac. Although vasovagal syncope is the most common cause of syncope, vigilance is required to identify those patients with a potentially fatal arrhythmia or with heart disease that predisposes to hypoperfusion. As such, all patients who present with syncope should have an ECG. Additional work-up studies are guided by the results of individual history and physical examination.

Risk factors for syncope in a community-based sample (the Framingham Heart Study)

The epidemiology of syncope has not been well described. Prior studies have examined risk factors for syncope in hospital-based or other acute or long-term care settings. To determine risk factors for syncope in a community-based sample, we performed a nested case-control study. We examined reports of syncope in Framingham Heart Study participants who underwent routine clinic visits from 1971 to 1990. For each syncope case (n = 543) 2 controls were matched for age, sex, and examination period. Mean age of subjects was 67 years (range 25 to 95); 59% were women. History of stroke or transient ischemic attack, history of myocardial infarction, high blood pressure, use of antihypertensive medication, use of other cardiac medication, smoking, alcohol intake, body mass index, systolic blood pressure, diastolic blood pressure, heart rate, atrial fibrillation, PR interval prolongation, interventricular block, and diabetes or elevated glucose level were examined as potential predictors. Using conditional logistic regression analysis, the predictors of syncope included a history of stroke or transient ischemic attack (odds ratio [OR] 2.56, 95% confidence interval [CI] 1.62 to 4.04), use of cardiac medication (OR 1.67, 95% CI 1.21 to 2. 30), and high blood pressure (OR 1.46, 95% CI 1.14 to 1.88). Lower body mass index was marginally associated with syncope (OR per 4 kg/m(2) decrement 1.10, 95% CI 0.99 to 1.22), as were increased alcohol intake (OR per 5 oz/week 1.11, 95% CI 0.99 to 1.26), and diabetes or an elevated glucose level (OR 1.29, 95% CI 0.96 to 1.75). To our knowledge, this study represents the first community-based study of risk factors for syncope.

Influence of left ventricular cavity size on clinical presentation in hypertrophic cardiomyopathy

The aim of this study was to assess whether left ventricular (LV) cavity size relates to functional impairment and syncope in patients with hypertrophic cardiomyopathy (HC). LV diastolic dysfunction influences functional limitation in HC. A reduced LV end-diastolic dimension may underlie impaired diastolic properties and be implicated in hemodynamic syncope. Eighty-two consecutive patients with HC (off drugs, in sinus rhythm) underwent echocardiography to measure LV end-diastolic dimension in the short-axis view (indexed to the body surface area) and radionuclide angiography (n = 50) to calculate peak filling rate (normalized to stroke counts/s). Patients in New York Heart Association functional classes II to IV had smaller LV end-diastolic dimension (23.2 +/- 2.6 vs 25.5 +/- 2.5 mm/M2, p = 0.0001) and lower peak filling rate (4.3 +/- 1.4 vs 5.1 +/- 1.3 stroke counts/s, p = 0.036) than those in New York Heart Association class I. LV end-diastolic diameter was correlated to peak filling rate (r = 0.37; p = 0.008). The most potent predictors of functional limitation were LV end-diastolic dimension (relative risk [RR] 0.63, confidence interval [CI] 0.45 to 0.88; p = 0.008), age (RR 1.09, CI 1.03 to 1.17; p = 0.003), and LV thickness score (RR 1.08, CI 1.02 to 1.13; p = 0.003). LV cavity size was smaller in patients with functional limitation irrespective of obstruction and hypertrophy. Patients with differed from those without a history of syncope for a smaller LV end-diastolic dimension (23.2 +/- 2.5 vs 25.0 +/- 2.7 mm/M2, p = 0.008), which was the only independent predictor of syncope (RR 0.77, CI 0.63 to 0.95; p = 0.013). Thus, a small LV cavity size is associated with functional limitation and history of syncope in HC.

Long-term outcome and prognostic determinants in children with hypertrophic cardiomyopathy

OBJECTIVES

We sought to determine clinical, angiographic, and echocardiographic predictors of survival in children with isolated hypertrophic cardiomyopathy (HCM) in a large pediatric centre.

BACKGROUND

Sudden death is a catastrophic outcome of HCM in childhood but has been difficult to predict. Current therapies might provide for improved outcome if factors identifying high risk can be identified.

METHODS

Records of 99 patients diagnosed with HCM from 1958 to 1997 at <18 yr were reviewed for clinical, angiographic (n = 62) and echocardiographic (n = 83) predictors of survival outcome. The effects of clinical characteristics on sudden death (including resuscitated sudden death) were individually tested in Cox's proportionate hazard modeling.

RESULTS

Seventy-one subjects were male. Median age at diagnosis was 5.0 yr with a medical follow-up interval of 4.8 yr. Thirty-seven of 97 patients had a family history of HCM. Ambulatory electrocardiograms (ECG) in 78 patients demonstrated supraventricular tachycardia in 16 and ventricular tachycardia in 21. Death or resuscitated sudden death occurred in 18 patients. Sudden death rate was 2.7%/yr after age 8 yr. Cox's proportionate survival modeling revealed increased corrected QT interval (QTc) dispersion on ECG (relative risk [RR] 1.61 per 20 ms increment, p < 0.0003), ventricular tachycardia (VT) on ambulatory ECG (RR 3.75, p < 0.006) and myocardial bridging of the LAD coronary (RR 12.0, p < 0.003) to be associated with reduced time to death or resuscitated sudden death.

CONCLUSIONS

Detailed assessment of ECGs, ambulatory ECGs, and coronary angiography can assist in identifying which children with HCM are at risk for sudden death.

Syncope in children

The sudden loss of consciousness in a child is concerning to both patients and their parents. Although most cases of syncope in children are benign, an adequate evaluation is required to exclude life-threatening disorders. Patient history and physical examination may be sufficient to define the cause of syncope in a large percentage of pediatric cases. The events and setting preceding the syncopal episode provide clues in defining the nature of the event.

Heart rate variability in patients with hypertrophic cardiomyopathy: association with clinical and echocardiographic features

Autonomic dysfunction has been reported in patients with hypertrophic cardiomyopathy. To evaluate the influence of different clinical and echocardiographic features of the disease on sympathovagal balance, as assessed by heart rate variability, 33 patients with hypertrophic cardiomyopathy and 33 healthy volunteers underwent echocardiographic examination and 24-hour electrocardiogram Holter recording. Measures of vagal modulation of heart rate were lower in patients with hypertrophic cardiomyopathy than in controls, particularly in those exhibiting syncope, exertional chest pain, dyspnea, or moderate or severe mitral regurgitation. Furthermore, the age-corrected multiple regression analysis showed that the parasympathetic cardiac control was inversely related to left atrial dimension and directly related to left ventricular end-systolic dimension. Therefore in hypertrophic cardiomyopathy the parasympathetic withdrawal is more evident in patients with symptoms than in those without; the reduction in left ventricular end-systolic dimension and the increase in left atrial size are the echocardiographic features that most influence the sympathovagal balance.

Syncope: current diagnosis and treatment

The patient with syncope often poses a formidable diagnostic challenge. A large number of underlying causes must be considered, ranging in severity from benign to life-threatening. A careful, systematic clinical evaluation beginning with a history, physical examination, and ECG will establish the diagnosis in most patients, and the judicious use of specialized testing will confirm or uncover the cause in many of the remaining cases. Further basic and clinical research into the pathogenesis and treatment of neurocardiogenic syncope, the role of HUT testing in neurally mediated syncope, and the optimal use of EPS in patients with cardiac disease will markedly improve our management of these patients in the future.

Hypertrophic cardiomyopathy: value of atrial programmed electrical stimulation in patients with or without syncope with special reference to the role of atrial arrhythmias

Hypertrophic cardiomyopathy may be associated with both supraventricular and ventricular arrhythmias, which may play a role in the genesis of syncope. The aim of this study was to assess the findings of electrophysiological study and programmed atrial and ventricular stimulation and their possible role in syncope. Programmed atrial and ventricular stimulation using up to two extrastimuli in right atrium and three in right ventricle at three cycle lengths (600, 400 ms and spontaneous) was systematically performed in 56 patients with hypertrophic cardiomyopathy. Thirty seven had unexplained dizzinesses or syncopes (group I) and 19 did not present loss of consciousness (group II). Patients with syncopes had a higher prevalence of induced sustained supraventricular tachyarrhythmia (73%) than those of group II (16%) (P<0.05). Inducible supraventricular tachycardia was the only finding in 16 patients with syncopes. During the follow-up (3 years+/-6 months), empirical antiarrhythmic therapy suppressed the symptoms, except in two patients who developed atrial fibrillation despite therapy. The high incidence of inducible atrial tachycardia of these patients was not correlated with particular Holter findings or echocardiographic data. However, their mean age was rather high (58+/-12 years). In conclusion, atrial tachyarrhythmias may play a role in syncopes of middle-aged patients with hypertrophic cardiomyopathy. Moreover programmed atrial stimulation is an useful means to identify this syncope mechanism.

Acute hemodynamic deterioration during rapid atrial pacing in patients with hypertrophic cardiomyopathy

BACKGROUND AND HYPOTHESIS

Supraventricular tachycardia and ventricular tachycardia are often observed in patients with hypertrophic cardiomyopathy (HCM) and they often alter the clinical features of HCM. We examine the influence of supraventricular tachycardia on cardiac function and assess the clinical characteristics of patients with HCM.

METHODS

We studied 32 patients with HCM and 8 normal volunteers using echocardiography under transesophageal rapid atrial pacing.

RESULTS

Presyncope-associated hypotension was observed during rapid atrial pacing in 8 HCM patients, but in none of the normal controls. During rapid atrial pacing (144 +/- 8 beats/min in HCM, 146 +/- 5 beats/min in controls), systolic blood pressure (SBP), the product of left ventricular filling volume (FV) and heart rate, and fractional shortening (%FS) in the HCM patients decreased significantly compared with the basal values (138 +/- 19 mmHg vs. 99 +/- 24 mmHg, 5.0 +/- 1.2 l/min vs. 2.9 +/- 0.9 l/min, 41.7 +/- 6.2% vs. 35.2 +/- 6.0%, respectively), but these decreases were not observed in normal controls. The decrement of SBP during rapid atrial pacing in HCM patients with a history of syncope was more marked than that in those without such history. The decrement correlated positively with the indices of left ventricular hypertrophy (maximal wall thickness and wall thickness index) and with %FS, and correlated negatively with the endsystolic left ventricular diameter at rest.

CONCLUSIONS

In some patients with HCM, supraventricular tachycardia causes marked hemodynamic deterioration that may be related to a history of syncope, marked hypertrophy, hyperkinesis, small cavity size, and small filling volume of the left ventricle.

The athlete's heart: is big beautiful?

Development of the concept of "athlete's heart" is traced through early clinical and radiographic studies to modern echocardiography and magnetic resonance imaging. It is noted that the lower limits of criteria for the diagnosis of a "pathological" enlargement of the heart have frequently been revised in an upward direction, as the prevalence of large hearts has been recognised in both endurance and power sports competitors who are in good health. Belief that hypertrophic cardiomyopathy is the commonest cause of sports related death in young adults is traced to weak diagnostic criteria and frequent republication of a very small group of cases. Although the existence of a congenital myocardial dystrophy is now well established, this condition is extremely rare, and has no particular predilection for athletes. Genetically based screening tests may become available in the future, but the exclusion of young adults from sports participation on echocardiographic criteria appears costly and ineffective. For most people, the development of a large heart is not a pathological sign--rather, it is a desirable outcome that will enhance performance on the sports field, and will allow longer independence in old age.

Time-domain signal-averaged electrocardiogram in nonischemic ventricular tachycardia

The prevalence of late ventricular potentials (LVPs) detected by signal averaged ECG (SAECG) is variable in nonischemic heart diseases. In idiopathic dilated cardiomyopathy, the prevalence increases from about 25% to 70%-90% in cases of spontaneous sustained ventricular tachycardia (VT), is not significantly correlated with hemodynamic and Holter data, and has a good positive predictive value for induced and spontaneous sustained VT. However, its predictive value for cardiac death has not been established. In primary hypertrophic cardiomyopathy, LVPs are rare (about 10%), not correlated to hemodynamic data, enhanced in cases of spontaneous sustained VT (up to 77%), and have a good predictive value of induced VT. LVP-SAECG are frequent in arrhythmogenic right ventricular dysplasia (ARVD) (70%-80%). They can identify patients with VT and an unapparent or limited form of this disease, or ARVD with few ventricular arrhythmias. The prevalence (26%-37%) of LVPs in mitral valve prolapse is clearly higher than in normal individuals or in other valvular diseases and is enhanced in cases of spontaneous and induced VT. Its significance remains speculative. After surgical repair of tetralogy of Fallot, LVPs can identify a group of patients with higher probability of induced and spontaneous risk of VT. The usefulness and significance of LVPs in other nonischemic cardiac diseases have not to date been established. In "true" idiopathic VT, without proved structural cardiac disease, the prevalence of LVPs does not exceed that observed in normal individuals (0%-5%), but in "apparent" idiopathic VT the prevalence of LVPs rises to 20%-40%. In these latter cases more invasive techniques must be used to discover a limited form of myocardiopathy.

Dispersion of ventricular repolarization in hypertrophic cardiomyopathy

On an averaged QRS-T cycle from a 15-lead record (12-lead electrocardiogram + XYZ leads) and through interactive editing, four electrocardiographic indices of the dispersion of ventricular repolarization (DVR) are automatically computed and represent the maximal interlead difference of QT and JTend and QT and JTapex. The values of these indices were then examined in three clinical groups matched for age and sex: normal subjects (control), patients with left ventricular hypertrophy (LVH group), and patients with hypertrophic cardiomyopathy (HCM group) without ventricular arrhythmias and without interacting drugs. The mean values of all four DVR indices were significantly increased in the HCM group compared with the control group and the LVH group of another origin (ie, for the QTe dispersion index, the mean values and the 97.5th percentiles were, respectively, 65 +/- 18 ms and 97 ms in the HCM group, 41 +/- 25 ms and 79 ms in the LVH group, and 31 +/- 15 ms and 58 ms in the control group). The maximal QT interval was also significantly longer in the HCM group (464 +/- 30 ms) than in the LVH group (436 +/- 32 ms) and the control group (428 +/- 25 ms).

Significance and prevalence of inducible atrial tachyarrhythmias in patients undergoing electrophysiologic study for presyncope or syncope

The purpose of the study was to report the prevalence of inducible supraventricular tachyarrhythmias (SVTA) in 827 consecutive patients aged 17 to 90 years who did not have spontaneous documented SVTA and who had unexplained presyncope and/or syncope. The electrophysiologic study (EPS) included programmed atrial and ventricular stimulation up to two extrastimuli at three cycle lengths, and the study of sino-atrial and AV conduction. The results were as follows. EPS was normal in 386 patients. Inducible junctional tachycardia or atrial flutter and fibrillation was the only finding in 187 patients (23%). In the remaining patients we found ventricular tachycardia in 103 (12%), heart block in 67 (8%), sick sinus syndrome in 56 (7%) and increased vagal tone in 28 (3%). The presence of an underlying heart disease (47%) and salvos of atrial premature beats on Holter monitoring (39%) were significantly correlated with the induction of SVTA. However, the comparison with similar groups without syncope indicates that only the induction of SVTA in patients with hypertrophic cardiomyopathy and mitral valve prolapse was significantly correlated with the history of syncope. In patients without heart disease or with prior myocardial infarction or decreased left ventricular function, the induction of SVTA, which is not associated with hypotension in the supine position, could require an induction after head-up tilting, because of the lack of specificity of programmed stimulation in these patients. Programmed atrial stimulation should be systematically performed in patients with unexplained syncope, in particular in those with hypertropic cardiomyopathy and mitral valve prolapse, who require a specific treatment, if a SVTA is induced. In other patients the results of programmed atrial stimulation should be interpreted cautiously.

Hypertrophic cardiomyopathy in Tuscany: clinical course and outcome in an unselected regional population

OBJECTIVES

Our aim was to study a population of patients with hypertrophic cardiomyopathy from the well defined geographic region of Tuscany in central Italy, a group virtually free of selective referral bias and therefore probably closely representative of the true patient population with this disease.

BACKGROUND

Most available information on clinical course, natural history and prognosis of hypertrophic cardiomyopathy is based on data generated from tertiary referral centers and therefore constitutes a potentially biased perspective of the disease process in this complex and diverse condition.

METHODS

The study group comprised 202 patients aged 1 to 74 years (mean +/- SD 41 +/- 17) at initial diagnosis and followed up for 1 to 30 years (mean 10 +/- 5).

RESULTS

Largely with the use of single or multiple drug therapy, the vast majority of patients (n = 154 [76%]) were asymptomatic or mildly symptomatic and in stable or improved condition over the period of follow-up, whereas the remaining patients (n = 48 [24%]) experienced deterioration, had substantial functional impairment or died. Of the 13 patients (6%) who died of cardiovascular causes related to hypertrophic cardiomyopathy, 11 had progressive congestive heart failure (including 6 in the end-stage phase) and only 2 died suddenly. The annual mortality rate for cardiovascular disease was 0.6% and that due to sudden cardiac death was only 0.1%; the cumulative survival rate was 97%, 95% and 92%, respectively, at 5, 10 and 15 years of follow-up. Atrial fibrillation proved to be a relatively common (n = 57 [28%]) and particularly unfavorable clinical feature, with premature death occurring in 9 of the 57 patients. The cumulative survival rate after 15 years was 76% for patients with atrial fibrillation versus 97% for patients with sinus rhythm. Syncope occurred in 33 patients (16%) but did not appear to be of prognostic significance.

CONCLUSIONS

In an unselected regional population, hypertrophic cardiomyopathy had a relatively benign prognosis inconsistent with its prior characterization as a generally progressive disorder, based primarily on the experience of selected referral institutions. Sudden unexpected cardiac death was distinctly uncommon, although a sizable proportion of patients (particularly the subset prone to atrial fibrillation), did experience clinical deterioration.

Echocardiographic Management of Patients With Hypertrophic Obstructive Ca rdiomyopathy Treated With Dual Chamber Pacemakers

A 53-year-old man diagnosed and treated for hypertrophic obstructive cardiomyopathy received serial echocardiograms before and after dual-chamber pacemaker implantation. Varying the programmed atrioventricular delay in a dual-chamber pacemaker can affect the left ventricular outflow tract pressure gradient in hypertrophic obstructive cardiomyopathy. Serial Doppler echo examinations were used to evaluate the effect of varying atrioventricular intervals. Echocardiography can be effectively used with pacemaker programming to optimize the left ventricular outflow tract velocities in patients with hypertrophic obstructive cardiomyopathy.