Significance of left atrial volume in patients < 20 years of age with hypertrophic cardiomyopathy

Efficiency and feasibility of semi-automated software for measuring left atrial volume in routine echocardiography in a pediatric population

PURPOSE

The traditional method for measuring left atrial volume (LAV) involves manual tracing. Recently, semi-automated techniques for measuring LAV, based on 2D speckle tracking echocardiography (STE) and 3D echocardiography (3DE), have become commercially available. This study aimed to investigate the efficiency and feasibility of these semi-automated software methods for LAV measurement in pediatric patients.

METHODS

We analyzed 207 pediatric patients with 2D and 3D echocardiographic images of the left atrium. The maximum LAV was measured using three techniques: (1) manual tracing, (2) STE-based semi-automated measurement, and (3) 3DE-based semi-automated measurement. We compared both LAV and the time required for LAV measurement among these three techniques. Intra- and inter-observer reproducibility of the LAV measurements was assessed using the intraclass correlation (ICC).

RESULTS

There was no difference in the LAV between the manual tracing and the STE-based method, but the LAV measured by 3DE-based method was slightly smaller than manual tracing. The measurement time was 32.6 ± 3.5, 53.8 ± 10.8, and 33.8 ± 13.0 s for manual tracing, STE-based, and 3DE-based techniques, respectively. There was no difference the time for LAV measurement between the manual tracing and the 3D-based technique. The agreement and ICC for intra-observer reproducibility was similar across all three techniques, but inter-observer reproducibility was superior with the 3DE-based technique.

CONCLUSIONS

Although the maximum LAV obtained through the 3DE-based techniques was slightly smaller compared with the traditional manual tracing method, the 3DE-based technique is anticipated to be integrated into routine examinations owing to its short measurement time and superior reproducibility.

Cardiopulmonary Exercise Test in Patients with Hypertrophic Cardiomyopathy: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with chronic diseases frequently adapt their lifestyles to their functional limitations. Functional capacity in Hypertrophic Cardiomyopathy (HCM) can be assessed by stress testing. We aim to review and analyze the available data from the literature on the value of Cardiopulmonary Exercise Test (CPET) in HCM. Objective measurements from CPET are used for evaluation of patient response to traditional and new developing therapeutic measurements.

METHODS

A systematic review of the literature was conducted in PubMed, Web of Science and Cochrane in Mar-20. The original search yielded 2628 results. One hundred and two full texts were read after the first screening, of which, 69 were included for qualitative synthesis. Relevant variables to be included in the review were set and 17 were selected, including comorbidities, body mass index (BMI), cardiac-related symptoms, echocardiographic variables, medications and outcomes.

RESULTS

Study sample consisted of 69 research articles, including 11,672 patients (48 ± 14 years old, 65.9%/34.1% men/women). Treadmill was the most common instrument employed (n = 37 studies), followed by upright cycle-ergometer (n = 16 studies). Mean maximal oxygen consumption (VO2max) was 22.3 ± 3.8 mL·kg^-1·min^-1. The highest average values were observed in supine and upright cycle-ergometer (25.3 ± 6.5 and 24.8 ± 9.1 mL·kg^-1·min^-1; respectively). Oxygen consumption in the anaerobic threshold (ATVO2) was reported in 18 publications. Left ventricular outflow tract gradient (LVOT) > 30 mmHg was present at baseline in 31.4% of cases. It increased to 49% during exercise. Proportion of abnormal blood pressure response (ABPRE) was higher in severe (>20 mm) vs. mild hypertrophy groups (17.9% vs. 13.6%, p < 0.001). Mean VO2max was not significantly different between severe vs. milder hypertrophy, or for obstructive vs. non-obstructive groups. Occurrence of arrhythmias during functional assessment was higher among younger adults (5.42% vs. 1.69% in older adults, p < 0.001). Twenty-three publications (9145 patients) evaluated the prognostic value of exercise capacity. There were 8.5% total deaths, 6.7% cardiovascular deaths, 3.0% sudden cardiac deaths (SCD), 1.2% heart failure death, 0.6% resuscitated cardiac arrests, 1.1% transplants, 2.6% implantable cardioverter defibrillator (ICD) therapies and 1.2 strokes (mean follow-up: 3.81 ± 2.77 years). VO2max, ATVO2, METs, % of age-gender predicted VO2max, % of age-gender predicted METs, ABPRE and ventricular arrhythmias were significantly associated with major outcomes individually. Mean VO2max was reduced in patients who reached the combined cardiovascular death outcome compared to those who survived (-6.20 mL·kg^-1·min^-1; CI 95%: -7.95, -4.46; p < 0.01).

CONCLUSIONS

CPET is a valuable tool and can safely perform for assessment of physical functional capacity in patients with HCM. VO2max is the most common performance measurement evaluated in functional studies, showing higher values in those based on cycle-ergometer compared to treadmill. Subgroup analysis shows that exercise intolerance seems to be more related to age, medication and comorbidities than HCM phenotype itself. Lower VO2max is consistently seen in HCM patients at major cardiovascular risk.

Predictors of Long-Term Outcome in Children with Hypertrophic Cardiomyopathy

To date limited data are available to predict the progression to end-stage heart failure (HF) with subsequent death (non-SCD), need for heart transplantation, or sudden cardiac death (SCD) in children with hypertrophic cardiomyopathy (HCM). We aimed to determine predictors of long-term outcome in children with HCM. A total of 112 children (median 14.1, IQR 7.8-16.6 years) were followed up for the median of 6.5 years for the development of morbidity and mortality, including arrhythmic and HF-related secondary end points. HF end point included HF-related death or heart transplant, and arrhythmic end point included resuscitated cardiac arrest, appropriate ICD discharge, or SCD. Overall, 23 (21 %) patients reached the pre-defined composite primary end point. At 10-year follow-up, the event-free survival rate was 76 %. Thirteen patients (12 %) reached the secondary arrhythmic end point, and 10 patients (9 %) reached the secondary HF end point. In multivariate model, prior cardiac arrest (r = 0.658), QTc dispersion (r = 0.262), and NSVT (r = 0.217) were independent predictors of the arrhythmic secondary end point, while HF (r = 0.440), LV posterior wall thickness (r = 0.258), LA size (r = 0.389), and decreased early transmitral flow velocity (r = 0.202) were all independent predictors of the secondary HF end point. There are differences in the risk factors for SCD and for HF-related death in childhood HCM. Only prior cardiac arrest, QTc dispersion, and NSVT predicted arrhythmic outcome in patients aged <18 years. LA size, LV posterior wall thickness, and decreased early transmitral flow velocity were strong independent predictors of HF-related events.

Efficacy of exercise training in symptomatic patients with hypertrophic cardiomyopathy: results of a structured exercise training program in a cardiac rehabilitation center

BACKGROUND

Recent data suggest that exercise training (ET) confers significant symptomatic and functional improvements in patients with diastolic dysfunction, and thus may be beneficial in patients with hypertrophic cardiomyopathy (HCM). However, there are no data regarding the safety or efficacy of ET in HCM patients.

DESIGN

A prospective non-randomized intervention design was used.

METHODS

We enrolled 20 patients with symptomatic HCM, significantly limited in everyday activity, into a supervised cardiac rehabilitation exercise program.

RESULTS

Patients were 62 ± 13 years old, in New York Heart Association (NYHA) functional class II (35%) or III (65%), had a mean interventricular septum dimension of 17 ± 5 mm and left ventricular ejection fraction (LVEF) of 53 ± 15%. Left ventricular outflow gradient was present at rest in nine patients (mean 51 ± 24 mm Hg) and six patients had an implantable defibrillator. Exercise prescription was based on heart rate reserve (HRR) determined from a symptom-limited graded exercise stress test. Exercise intensity was gradually increased from 50% to 85% of the HRR over the training period. Patients completed an average of 41 ± 8 hours of aerobic ET. No adverse events or sustained ventricular arrhythmias occurred during the training program. Functional capacity, assessed by a graded exercise test, improved from 4.7 ± 2.2 to 7.2 ± 2.8 metabolic equivalents (METs) (p = 0.01). NYHA functional class improved from baseline by ≥ 1 grade in 10 patients (50%) and none experiencing deterioration during follow-up.

CONCLUSIONS

The present study suggests that patients with HCM who remain symptomatic despite medical therapy may achieve considerable functional improvement through a supervised ET program.

Cardiomyopathies in children

Cardiomyopathy (CMP) is a heterogeneous disease caused by a functional abnormality of the cardiac muscle. CMP is of 2 major types, dilated and hypertrophic, and is further classified as either primary or secondary. Secondary CMP is caused by extrinsic factors, including infection, ischemia, hypertension, and metabolic disorders. Primary CMP is diagnosed when the extrinsic factors of secondary CMP are absent. Furthermore, the World Health Organization, American Heart Association, and European Cardiology Association have different systems for clinically classifying primary CMP. Primary CMP is rare and associated with a family history of the disease, implying that genetic factors might affect its incidence. In addition, the incidence of CMP varies widely according to patient ethnicity. Genetic testing plays an important role in the care of patients with CMP and their families because it confirms diagnosis, determines the appropriate care for the patient, and possibly affects patient prognosis. The diagnosis and genetic identification of CMP in patients' families allow the possibility to identify novel genes that may lead to new treatments. This review focuses on the epidemiology, pathophysiology, diagnosis, and treatment of CMP, with the aim of providing pediatricians with insights that may be helpful in the early identification and management of idiopathic CMP in children.

Interpretation of left ventricular diastolic dysfunction in children with cardiomyopathy by echocardiography: problems and limitations

BACKGROUND

Left ventricular diastolic dysfunction (DD) is a key determinant of outcomes in pediatric cardiomyopathy (CM), but remains very challenging to diagnose and classify. Adult paradigms and guidelines relating to DD are currently applied in children. However, it is unknown whether these are applicable to children with CM. We investigated the assessment of DD in children with CM using adult and pediatric echocardiographic criteria and tested whether recent adult guidelines are applicable to this population.

METHODS AND RESULTS

Three investigators independently classified diastolic function in 4 study groups: controls, dilated, hypertrophic, and restrictive CM. Agreement among investigators, failure to classify DD, and the reasons for diagnostic failure were determined. The usefulness of individual echo parameters to diagnose and classify DD was assessed. One hundred seventy-five children (aged 0-18 years) were studied. DD diagnostic criteria were discrepant in the majority of patients. Delayed relaxation was diagnosed in only 14% of hypertrophic CM patients and never in dilated CM and restrictive CM, with 50% of those patients having coexisting findings of elevated filling pressures. Many key parameters, such as mitral and pulmonary venous Doppler, were not informative. Agreement among investigators for grading of DD was poor (36% of CM patients).

CONCLUSIONS

Assessment of DD in childhood CM seems inadequate using current guidelines. The large range of normal pediatric reference values allows diagnosis of DD in only a small proportion of patients. Key echo parameters to assess DF are not sufficiently discriminatory in this population, and discrepancies between criteria within individuals prevent further classification and result in poor interobserver agreement.

Left atrial volume change throughout the cardiac cycle in children with congenital heart disease associated with increased pulmonary blood flow: evaluation using a novel left atrium-tracking method

There is a paucity of data regarding the significance of left atrial (LA) volume and its changes throughout the cardiac cycle in pediatric patients with heart disease. The recently developed LA volume-tracking (LAVT) method can automatically construct the LA volume curve. The study group consisted of 48 pediatric patients with ventricular septal defect (n = 34) or patent ductus arteriosus (n = 14) and age-matched healthy controls. Maximum and minimum LA volumes (LAVmax and LAVmin, respectively) were measured. The total LA emptying volume (LAVtotal) was defined as LAVmax--LAVmin. Volume parameters were standardized by dividing by body surface area (BSA). The total LA emptying fraction (%LAVtotal) was defined as the ratio of LAVtotal to LAVmax. In the patient group, there was a positive correlation between the ratio of pulmonary to systemic blood flow (Qp/Qs) and LAVmax/BSA, LAVmin/BSA, and LAVtotal/BSA (r = 0.42, 0.44, and 0.34, respectively). LAVmin/BSA was positively correlated with the ratio of early mitral inflow velocity to early mitral annular diastolic tissue Doppler velocity (E/E') (r = 0.32). The %LAVtotal had a negative correlation with left-ventricular (LV) end-diastolic pressure (r = -0.32). There were significant correlations between serum B-type natriuretic peptide level and LAVmax/BSA, LAVmin/BSA, and %LAVtotal (r = 0.38, 0.49, and -0.35, respectively). The LAVT method is useful in the evaluation of LV diastolic function in pediatric patients with chronic LV volume overload.

Noninvasive imaging modalities and sudden cardiac arrest in the young: can they help distinguish subjects with a potentially life-threatening abnormality from normals?

Sudden cardiac arrest (SCA) in the young is always tragic, but fortunately it is an unusual event. When it does occur, it usually happens in active individuals, often while they are participating in physical activity. Depending on the population's characteristics, the most common causes of sudden cardiac arrest in these subjects are hypertrophic cardiomyopathy, congenital coronary abnormalities, arrhythmia in the presence of a structurally normal heart (ion channelopathies or abnormal conduction pathways), aortic rupture, and arrhythmogenic right-ventricular cardiomyopathy. Two-dimensional echocardiography (2-DE) has been proposed as a screening tool that can potentially detect four of these five causes of SCA, and many groups now sponsor community-based 2-DE SCA-screening programs. "Basic" 2-DE screening may include assessment of ventricular volumes, mass, and function; left atrial size; and cardiac and thoracic vascular (including coronary) anatomy. "Advanced" echocardiographic techniques, such as tissue Doppler and strain imaging, can help in diagnosis when the history, electrocardiogram (ECG), and/or standard 2-DE screening suggest there may be an abnormality, e.g., to help differentiate those with "athlete's heart" from hypertrophic or dilated cardiomyopathy. Cardiac magnetic resonance imaging or cardiac computed tomography can be added to increase diagnostic sensitivity and specificity in select cases when an abnormality is suggested during SCA screening. Test availability, cost, and ethical issues related to who to screen, as well as the detection of those with potential disease but low risk, must be balanced when deciding what tests to perform to assess for increased SCA risk.

Restrictive physiology is associated with poor outcomes in children with hypertrophic cardiomyopathy

Pediatric patients with hypertrophic cardiomyopathy (HCM) and restrictive physiology (RP) with poor outcomes have been identified, but data on their course are limited. Our goal was to delineate the clinical features and course of children with HCM and RP. An institutional review of 119 patients identified between 1985 and 2010 with the diagnosis of HCM was performed. The diagnosis of RP was based on >1 echocardiogram along with at least one of the following: left atrial enlargement without evidence of left ventricle dilation, E/E' ratio ≥ 10, and E/A ratio ≥ 3. Outcomes analysis was performed using Cox or Poisson regression when appropriate. RP was present in 50 (42%) patients. In patients without RP, 10-year freedom-from-death or aborted sudden cardiac death (aSCD), and death or heart transplant (HT), were 93.6 and 98.5%, respectively. In patients with RP, 10-year freedom-from-death or aSCD, and death or HT, were 59.0 and 71.2%, respectively. RP conferred a 3.5-fold increase in incidence rate of hospitalization (P = 0.01), a 3.8-fold increase in hazard of death or aSCD (P = 0.02), and a 5.7-fold increase in hazard of death or HT (P = 0.04). Assessment for RP is of paramount importance in children with HCM because those without RP have a good prognosis, and those with RP account for the majority of poor outcomes.

Clinical spectrum in a family with tropomyosin-mediated hypertrophic cardiomyopathy and sudden death in childhood

This report demonstrates variable clinical courses in several members of a family with tropomyosin-mediated hypertrophic cardiomyopathy (HCM) (L185R mutation). The index case was an 8-year-old girl who died from sudden cardiac death and was diagnosed with HCM on autopsy. Her father had minimal hypertrophy but had an implantable cardioverter defibrillator placed prophylactically with no appropriate shocks. Two brothers progressed from normal phenotype to HCM on follow-up, the younger with significant hypertrophy and the older with mild hypertrophy. They both had malignant arrhythmia courses with VF, which was terminated by ICD shock. In conclusion, family members with same genotype can have significantly variable phenotypes.

Left atrial volume in children without heart disease and in those with ventricular septal defect or patent ductus arteriosus or hypertrophic cardiomyopathy

In adults, the left atrial (LA) volume has been shown to reflect diastolic function and is a powerful predictor of cardiac morbidity and mortality. Normative LA volume values in children and the effect of loading conditions on the LA volume in those with congenital heart disease are lacking. The purposes of the present study were to (1) establish normal LA volume values for children, (2) assess the effect of left ventricular volume loading conditions on LA volume, and (3) describe the effect of abnormal myocardial relaxation on the LA volume. We retrospectively reviewed the echocardiograms from 3 pediatric cohorts: group N (n = 522), children with normal echocardiographic findings; group VSD/PDA (n = 71), children with ventricular septal defect (VSD; n = 50) or patent ductus arteriosus (PDA; n = 21); and group HC (n = 63), children with hypertrophic cardiomyopathy (HC). In group N, we identified the LA volume indexed to the body surface area (LA volume index) as a consistent measure of the LA volume in children 3 to 23 months old (mean 16 ± 3 ml/m(2)) and 2 to 17 years old (mean 22 ± 4 ml/m(2)). LA dilation was more common in group VSD/PDA than in group N (27% vs 2%, p <0.0001) and in children with moderate or large shunts than in those with smaller shunts (61% vs 5%, p <0.0001). In group HC, the LA volume index correlated with the mitral valve E/e' ratio (p <0.0001). In conclusion, this is the first study to establish normal pediatric LA volume values. The LA volume index is a reproducible measure of LA size in children ≥ 3 months old. The LA volume index reflects a chronically increased left ventricular volume load in children with VSD or PDA and chronically elevated left ventricular filling pressures in children with HC.

Assessment of left atrial volume: a focus on echocardiographic methods and clinical implications

Left atrial enlargement is an important predictor of cardiovascular events such as atrial fibrillation, stroke, heart failure and mortality. A number of methods of left atrial size assessment by echocardiography have been reported, from the simple antero-posterior diameter in the parasternal long axis view to the more complex ellipsoid, area-length and Simpson's method of estimating left atrial volume. These different methods of left atrial size assessment, their clinical implications and some common pitfalls are discussed in this review.

Diastolic dysfunction and its histopathological correlation in obstructive hypertrophic cardiomyopathy in children and adolescents

BACKGROUND

Histopathologic hallmarks of hypertrophic cardiomyopathy (HCM) include myocyte hypertrophy and disarray as well as interstitial and endocardial fibrosis. Published correlations between echocardiographic parameters and histopathologic findings are scarce.

METHODS

All patients aged <20 years (n = 45; 15 female patients; median age, 14 years) with obstructive HCM undergoing septal myectomy at the Mayo Clinic from 2003 to 2007 were identified. A retrospective review of echocardiographic data was performed, and these data were compared with the histologic findings from the myectomy specimens.

RESULTS

Histopathologic analysis of myectomy specimens revealed significant myocyte hypertrophy (100%), myocyte disarray (98%), interstitial fibrosis (95%), and subendocardial fibrosis (97%). On multivariate regression analysis, there was a significant relationship between the degree of myocyte disarray and echocardiographic markers of left ventricular diastolic dysfunction.

CONCLUSION

The results of this study suggest that myocyte disarray is a key factor responsible for diastolic dysfunction in pediatric patients with obstructive HCM. These findings provide novel insights into the mechanism of diastolic dysfunction in HCM that warrant further study.