Clinical Features and Natural History of Preadolescent Nonsyndromic Hypertrophic Cardiomyopathy

BACKGROUND

Up to one-half of childhood sarcomeric hypertrophic cardiomyopathy (HCM) presents before the age of 12 years, but this patient group has not been systematically characterized.

OBJECTIVES

The aim of this study was to describe the clinical presentation and natural history of patients presenting with nonsyndromic HCM before the age of 12 years.

METHODS

Data from the International Paediatric Hypertrophic Cardiomyopathy Consortium on 639 children diagnosed with HCM younger than 12 years were collected and compared with those from 568 children diagnosed between 12 and 16 years.

RESULTS

At baseline, 339 patients (53.6%) had family histories of HCM, 132 (20.9%) had heart failure symptoms, and 250 (39.2%) were prescribed cardiac medications. The median maximal left ventricular wall thickness z-score was 8.7 (IQR: 5.3-14.4), and 145 patients (27.2%) had left ventricular outflow tract obstruction. Over a median follow-up period of 5.6 years (IQR: 2.3-10.0 years), 42 patients (6.6%) died, 21 (3.3%) underwent cardiac transplantation, and 69 (10.8%) had life-threatening arrhythmic events. Compared with those presenting after 12 years, a higher proportion of younger patients underwent myectomy (10.5% vs 7.2%; P = 0.045), but fewer received primary prevention implantable cardioverter-defibrillators (18.9% vs 30.1%; P = 0.041). The incidence of mortality or life-threatening arrhythmic events did not differ, but events occurred at a younger age.

CONCLUSIONS

Early-onset childhood HCM is associated with a comparable symptom burden and cardiac phenotype as in patients presenting later in childhood. Long-term outcomes including mortality did not differ by age of presentation, but patients presenting at younger than 12 years experienced adverse events at younger ages.

Relationship Between Maximal Left Ventricular Wall Thickness and Sudden Cardiac Death in Childhood Onset Hypertrophic Cardiomyopathy

BACKGROUND

Maximal left ventricular wall thickness (MLVWT) is a risk factor for sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). In adults, the severity of left ventricular hypertrophy has a nonlinear relationship with SCD, but it is not known whether the same complex relationship is seen in childhood. The aim of this study was to describe the relationship between left ventricular hypertrophy and SCD risk in a large international pediatric HCM cohort.

METHODS

The study cohort comprised 1075 children (mean age, 10.2 years [±4.4]) diagnosed with HCM (1-16 years) from the International Paediatric Hypertrophic Cardiomyopathy Consortium. Anonymized, noninvasive clinical data were collected from baseline evaluation and follow-up, and 5-year estimated SCD risk was calculated (HCM Risk-Kids).

RESULTS

MLVWT Z score was <10 in 598 (58.1%), ≥10 to <20 in 334 (31.1%), and ≥20 in 143 (13.3%). Higher MLVWT Z scores were associated with heart failure symptoms, unexplained syncope, left ventricular outflow tract obstruction, left atrial dilatation, and nonsustained ventricular tachycardia. One hundred twenty-two patients (71.3%) with MLVWT Z score ≥20 had coexisting risk factors for SCD. Over a median follow-up of 4.9 years (interquartile range, 2.3-9.3), 115 (10.7%) had an SCD event. Freedom from SCD event at 5 years for those with MLVWT Z scores <10, ≥10 to <20, and ≥20 was 95.6%, 87.4%, and 86.0, respectively. The estimated SCD risk at 5 years had a nonlinear, inverted U-shaped relationship with MLVWT Z score, peaking at Z score +23. The presence of coexisting risk factors had a summative effect on risk.

CONCLUSIONS

In children with HCM, an inverted U-shaped relationship exists between left ventricular hypertrophy and estimated SCD risk. The presence of additional risk factors has a summative effect on risk. While MLVWT is important for risk stratification, it should not be used either as a binary variable or in isolation to guide implantable cardioverter defibrillator implantation decisions in children with HCM.

External validation of the HCM Risk-Kids model for predicting sudden cardiac death in childhood hypertrophic cardiomyopathy

AIMS

Sudden cardiac death (SCD) is the most common mode of death in childhood hypertrophic cardiomyopathy (HCM). The newly developed HCM Risk-Kids model provides clinicians with individualized estimates of risk. The aim of this study was to externally validate the model in a large independent, multi-centre patient cohort.

METHODS AND RESULTS

A retrospective, longitudinal cohort of 421 patients diagnosed with HCM aged 1-16 years independent of the HCM Risk-Kids development and internal validation cohort was studied. Data on HCM Risk-Kids predictor variables (unexplained syncope, non-sustained ventricular tachycardia, maximal left ventricular wall thickness, left atrial diameter, and left ventricular outflow tract gradient) were collected from the time of baseline clinical evaluation. The performance of the HCM Risk-Kids model in predicting risk at 5 years was assessed. Twenty-three patients (5.4%) met the SCD end-point within 5 years, with an overall incidence rate of 2.03 per 100 patient-years [95% confidence interval (CI) 1.48-2.78]. Model validation showed a Harrell's C-index of 0.745 (95% CI 0.52-0.97) and Uno's C-index 0.714 (95% 0.58-0.85) with a calibration slope of 1.15 (95% 0.51-1.80). A 5-year predicted risk threshold of ≥6% identified 17 (73.9%) SCD events with a corresponding C-statistic of 0.702 (95% CI 0.60-0.81).

CONCLUSIONS

This study reports the first external validation of the HCM Risk-Kids model in a large and geographically diverse patient population. A 5-year predicted risk of ≥6% identified over 70% of events, confirming that HCM Risk-Kids provides a method for individualized risk predictions and shared decision-making in children with HCM.

Coronary artery spasm and dobutamine stress echocardiography

AIMS

The aim of this article was to assess whether abnormal dobutamine stress echocardiography (DSE) can be due to a dobutamine-induced coronary spasm in patients with angiographically documented vasospastic coronary arteries.

METHODS AND RESULTS

Between January 2004 and April 2008, we prospectively evaluated all patients with known or suspected coronary artery disease (CAD) referred to the echocardiography laboratory for dobutamine stress tests (6061 examinations). Those with abnormal DSE underwent coronary angiogram with a systematic methylergometrine intracoronary injection in the case of absence of significant coronary stenosis or spontaneous occlusive coronary spasm. Patients who had spontaneous occlusive coronary spasm or positive methylergometrine test, but no significant stenoses, were ultimately included in this study. About 581 patients had abnormal DSE, among them only 20 (3.4%) fulfilled the inclusion criteria. There were 15 males and 5 females, and mean age was 64.35 years (range 52-85); 8 patients had a known history of CAD and all of them had at least two established cardiovascular risk factors. The culprit vessel was the left anterior descending artery in 10 cases (50%), right coronary artery in 8 cases (40%), and left circumflex in 2 cases (10%). There was a systematic correspondence between the culprit arteries and dobutamine-induced wall motion abnormality territories. No complications occurred during examination or during the provocation test. All the patients were discharged with a calcium channel blocker and were doing well after 13 months of mean follow-up.

CONCLUSION

Coronary artery spasm can be induced at DSE, but is a rare finding; it could, though, be clinically relevant as it may partly explain some erroneously labelled 'false-positive' examinations. Methylergometrine provocation test is a safe and advisable approach in such situations.

[Rehabilitation of hypoplastic pulmonary arteries in pulmonary atresia with ventricular septal defect. Medium term results]

The treatment of pulmonary atresia with ventricular septal defect, hypoplasia of the native pulmonary arteries and major aorto-pulmonary collaterals is controversial with a wide range of options from symptomatic treatment to surgical correction, but usually unifocal surgery. However, the collateral vessels used in the reconstruction are often tortuous and stenosed, resulting in a problematic haemodynamic result. The authors report the results of medico-surgical rehabilitation of the native pulmonary arteries in three stages. Since 1990, patients with an average Nakata index of 27.5 +/- 16.7 mm2/m2 underwent elective surgical connection of the native pulmonary arteries to the right ventricle (1st stage) followed by their rehabilitation with catheter occlusion of the collaterals (2nd stage) with the aim of preparing surgical correction (3rd stage). The first surgical stage at an median age of 5 months (0.1 to 25.2) was complicated by one death. After an average of 2.1 +/- 1 catheterisations, 17 patients underwent surgical correction at an median age of 2.18 (0.6 to 10.3) years with an average Nakata index of 207 +/- 91 mm2/m2. All survived surgery with three late deaths in patients with poor haemodynamic results (right ventricular/left ventricular pressure ratio>80%). After an median follow-up of 9.2 (3.5 to 17) years, the 14 survivors are in NYHA Class I or II with a good haemodynamic result in 10 patients. The authors conclude that despite some late deaths and raised right ventricular and pulmonary artery pressures in a minority of patients, the rehabilitation of the pulmonary arteries is an effective management of this cardiopathy.