Hypertrophic cardiomyopathy (HCM) is a relatively common genetic cardiac disease (0.47 cases per 100.000 children per year) that is heterogeneous with respect to disease-causing mutations, clinical presentation, prognosis, and treatment strategies. HCM is a myocardial disease characterized by hypertrophy of the left ventricle which is not secondary to congenital heart disease or arterial hypertension. The severity of cardiac hypertrophy, etiology, as well as the clinical course of HCM in children is varied, resulting in a large spectrum of clinical and phenotypic expression (1, 2). Left ventricular hypertrophy is usually asymmetrical. Most are occupied septum and anterolateral free wall of the left ventricle, concentric hypertrophy occurs frequently and occasionally apex hypertrophy (3). Hypertrophic obstructive cardiomyopathy was diagnosed in 25% of patients with HCM, they have an obstruction and systolic pressure gradient in the left ventricular outflow tract (LVOT). In a subgroup of children with HCM, the thickened heart muscle can cause signs and symptoms, such as shortness of breath, fatigue, syncope, chest pain, progressive heart failure and problems in the heart’s electrical system resulting in life-threatening arrhythmias (3, 4). Hypertrophic cardiomyopathy is the most common cause of sudden cardiac death (SCD) in the young (including competitive athletes) (5-7). A subgroup of patients with hypertrophic obstructive cardiomyopathy (HOCM) remain severely symptomatic despite optimal medical therapy. Septal myectomy reduces or eliminates left ventricular outflow obstruction and produces marked symptomatic improvement (8, 9).

Treatment strategies include drug treatment for exertional dyspnea (β-blockers, verapamil), pharmacological treatment and radiofrequency catheter (RF) ablation for arrhythmias and the septal myectomy operation, which is the standard of care for severe refractory symptoms associated with marked outflow obstruction. The alcohol septal ablation and pacing are alternatives to surgery for selected adult patients. High-risk patients may be effectively protected against sudden cardiac death with the implantable cardioverter-defibrillator (ICD). In children with progressive heart failure pharmacological treatment of heart failure is used, and in the absence of improvement they are qualified for a heart transplant.

Retrospective analysis of clinical profile, current therapeutic options and SCD risk assessment in children with HCM hospitalized in the Department of Pediatric Cardiology in the years 1991-2013. Mean follow-up was 6.4 ± 4.83 yrs (ranged from 5 months to 20 yrs).

We analyzed 108 patients, 44 girls, 64 boys, mean age 9.7 ± 5.46 years (ranged from 4 month to 17.7 yrs) with hypertrophic cardiomyopathy. Patients demographics, clinical symptoms (shortness of breath, fatigability, syncope, pre-syncope, chest pain, heart failure, arrhythmias), family history of HCM and SCD, treatment strategy as well as the results of echocardiography, chest X-ray, 12-leads ECG, 24h Holter ECG, exercise test with assessment of blood pressure response to exercise were analyzed. HCM was diagnosed in the presence of left ventricular hypertrophy (more than two SDs from the normal range corrected for body size (BSA); z-score ≥ 2) in the absence of haemodynamic conditions that could account for the observed degree of hypertrophy. Left ventricular hypertrophy as % of mean normal range relative to BSA and z-score were calculated. Family history of SCD was defined as one or more SCD in relatives < 40 years of age or SCD in a relative with confirmed HCM at any age. Unexplained syncope was defined as unexplained transient loss of consciousness at or prior to first evaluation. Vasovagal syncope was not considered a risk factor for SCD. Abnormal systolic blood pressure response to exercise (ABPRE): < 25 mmHg rise in systolic blood pressure from rest to peak exercise and/or > 10 mmHg drop from maximal systolic blood pressure when exercised to exhaustion. Nonsustained ventricular tachycardia (NSVT) was defined as ≥ 3 consecutive ventricular extra systoles at a rate of ≥ 120 beats/min lasting < 30 s during Holter monitoring. In all patients, cardiological test results and data from the family history have been analyzed regarding the presence of major risk factors for SCD according to the Expert Group of the American and the European Society of Cardiology (10-12) recommendations such as sudden cardiac arrest (SCA) in an interview, sudden cardiac death in the family history, syncope of unknown etiology, left ventricular thickness ≥ 30 mm, spontaneous sustained ventricular tachycardia, abnormal blood pressure response during exercise and episodes of NSVT in 24-hour Holter ECG recording.

Of the 108 patients studied 77 (71%) were treated only pharmacologically, with 4 children underwent RF catheter ablation (3.7%), in 8 (7.4%) patients septal myectomy was performed. In 17 (15.7%) children with risk factors for sudden cardiac death ICD for primary prevention (12/17) and secondary prevention (5/17) was implanted. The heart transplant was qualified in six patients (5.5%) who had symptoms of progressive heart failure, not responsive to drug treatment efficacy. Table 1 lists the baseline characteristics of the 108 patients studied.

In 7 patients with electrocardiographic features of pre-excitation (Wolff-Parkinson-White syndrome)electrophysiological study was done, in 4 (3.7%) children accessory atrioventricular pathway was diagnosed and RF ablation was performed. The mean age at the ablation was 12.1 ± 5 yrs (ranged from 6.7 to 17 yrs). Maximum left ventricular wall thickness ranged from 6.6 to 18.9 mm, an average of 14 mm (from 157 to 378% of mean normal range relative to BSA, medium 240%, z-score ranged from 2.3 to 9.7, average 5.8). Of the 4 patients with accessory pathways, in 2 children episodes of supraventricular tachycardia and reentry atrioventricular tachycardia were present. RF ablation was effective in 2 patients with an accessory atriventricular pathways located in left upper wall, after procedure no evidence of pre-excitation was found. One patient underwent RF ablation of two accessory atrioventricular pathways located in the septal posterior wall and right lateral wall. It was a good early effect of ablation-no conduction by bundle of Kent, but perhaps there is a His-Purkinje conduction (a real Mahaim fiber)because after ablation in electrocardiography features of pre-excitation persisted. It was concluded that the early result of RF ablation is good, remote requires further observation. In one patient RF ablation of two accessory atrioventricular pathways located in the left bottom and lateral wall was performed. After intervention, no signs of preexitation in electrocardiography was observed. During ventricular pacing narrow complexes – the earliest retrograde activation of the His bundle around the left side occured. Due to the location (indicated transseptal access), duration of application abandoned to continue the procedure. This patient received amiodarone and is expected to repeat RF ablation. All of these four patients after RF ablation receive beta-blockers.