Objective: To investigate the clinical outcome, ECG characteristics, and optimal treatment of catecholaminergic polymorphic ventricular tachycardia (CPVT), a malignant and rare ventricular tachycardia. Patients and methods: Questionnaire responses and ECGs of 29 patients with CPVT were evaluated. Mean (SD) age of onset was 10.3 (6.1) years. Results: The initial CPVT manifestations were syncope (79%), cardiac arrest (7%), and a family history (14%). ECGs showed sinus bradycardia and a normal QTc. Mean heart rate during CPVT was 192 (30) beats/min. Most cases were non-sustained (72%), but 21% were sustained and 7% were associated with ventricular fibrillation. The morphology of CPVT was polymorphic (62%), polymorphic and bidirectional (21%), bidirectional (10%), or polymorphic with ventricular fibrillation (7%). There was 100% inducement of CPVT by exercise, 75% by catecholamine infusion, and none by programmed stimulation. No late potential was recorded. Onset was in the right ventricular outflow tract in more than half the cases. During a follow up of 6.8 (4.9) years, sudden death occurred in 24% of the patients, 7% of whom had anoxic brain damage. Autosomal dominant inheritance was seen in 8% of the patients' families. β Blockers completely controlled CPVT in only 31% of cases. Calcium antagonists partially suppressed CPVT in autosomal dominant cases. Conclusions: CPVT may arise in certain distinct areas but the prognosis is poor. The onset of CPVT may be an indication for an implanted cardioverter-defibrillator.

he incidence of ventricular tachycardia (VT) in childhood is low (0.2-0.8 per 10,000 children in school-based heart screening) compared with that in adults [1][2][3][4][5][6] in whom most VT is associated with coronary artery disease. In contrast, most pediatric cases are idiopathic without underlying heart disease and are found incidentally during school-based heart screening, with the exception of those found as complications of congenital heart diseases. The aim of the present study was to review the clinical picture and long-term course of patients in whom VT was detected by school-based screening. Methods SubjectsThe subjects were 48 children (23 males, 25 females) diagnosed with VT after routine school-based heart examinations conducted before they entered school or while they attended primary, junior or senior high school. All children undergo a 12-lead ECG, which pediatric cardiologists or Circulation Journal Vol.69, March 2005 pediatricians then check for abnormalities (the rate of abnormal ECGs is approximately 2-3% per annum). Children who have an abnormal ECG and have not been previously followed for heart disease, have a more detailed examination at a regional hospital. The present subjects were detected in this way and referred to the Department of Paediatrics, Yokohama City University Hospital where they were diagnosed as having VT. Of the 48 patients, underlying heart disease was detected in 2 cases (nonischemic left ventricular aneurysm, 1; arrhythmogenic right ventricular cardiomyopathy, 1), either at the time of the first medical examination after school-based screening or during follow-up. All of the 48 patients were followed for more than 2 years (2-30 years; average: 6 years) after the medical examinations. At the first medical examination, these subjects ranged in age from 5 to 15 years (average: 11 years). Cardiac ExaminationsAll subjects underwent an examination consisting of a 12-lead ECG, treadmill exercise test, chest X-ray and echocardiography to determine the presence or absence of underlying heart disease. The site of origin and type of VT (monomorphic or polymorphic) were determined on the basis of the QRS morphology of the VT detected by 12-lead ECG. Holter monitoring was used to record the (1) total number of premature ventricular contractions (PVC) in 1 day, (2) number of episodes of VT/day, the maximum number of salvos of VT and the heart rate during VT. Treadmill exercise stress testing and 24-h ECG monitoring Long-Term Course and Clinical Characteristics of Ventricular Tachycardia Detected in Children by School-Based Heart Disease ScreeningMari Iwamoto, MD; Ichiroh Niimura, MD † ; Toshimitsu Shibata, MD † † ; Kiyoshi Yasui, MD*; Kiyohiro Takigiku, MD**; Takashi Nishizawa, MD*; Tohru Akaike, MD; Shunpei Yokota, MD** Background The prognosis of ventricular tachycardia (VT) in children with overt heart disease is generally good, so the aim of this study was to review the prognosis and necessity of treatment of VT that detected by school-based heart disease screening. Method...

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The dynamic mechanical behavior of excised rabbit papillary muscles that had been tonically activated by replacing bathing Ca2+ with Ba2+ was studied. Steady activation was used to visualize the dynamic behavior of cardiac myofilaments more clearly than is possible during twitches, which are complicated by the kinetics of excitation-contraction coupling. To avoid artifacts due to damaged ends of the muscle, the length of a central segment, which was defined by 2 tungsten pins inserted through the muscle, was measured. To test the mechanical behavior of the contractured muscles (at 24 degrees C), the central segment length was sinusoidally oscillated (amplitude 1%) at 15 different frequencies (0.05-30 Hz). The dynamic stiffness of the central segment was calculated from the ratio of force response amplitude to length perturbation amplitude. At low frequencies (below 0.4 Hz), stiffness was approximately constant and reflected the force-length relation. However, in a localized range near 1 Hz, there was a distinct drop in the magnitude of dynamic stiffness to approximately half its low-frequency baseline. This range may reflect the dynamics of attachment and detachment of force generators. The frequency of minimum stiffness was consistent among all muscles (1.3 +/- 0.3 Hz). Moreover, no significant change in this frequency was found over the examined range of lengths (90-100% of the segment length that produced maximal developed force) and activation levels (Ba2+ concentration 0.3-1.0 mM). From 2 to 8 Hz, dynamic stiffness appeared to reflect force-velocity properties, but at higher frequencies, another elastic property emerged. At 30 Hz, stiffness was proportional to force, with an apparent series elasticity less than 1.8%. Even though the muscles had only moderate longitudinal inhomogeneity, quantitatively significant (35%) errors would have been introduced had the study relied on total muscle length instead of central segment length.