Calmodulin mutations and life-threatening cardiac arrhythmias: insights from the International Calmodulinopathy Registry
2019
AIMS: Calmodulinopathies are rare life-threatening arrhythmia syndromes which affect mostly young individuals and are, caused by mutations in any of the three genes (
CALM1-3) that encode identical calmodulin proteins. We established the International Calmodulinopathy Registry (ICalmR) to understand the natural history, clinical features, and response to therapy of patients with a
CALM-mediated arrhythmia syndrome. METHODS AND RESULTS: A dedicated Case Report File was created to collect demographic, clinical, and genetic information. ICalmR has enrolled 74 subjects, with a variant in the CALM1 (n = 36), CALM2 (n = 23), or CALM3 (n = 15) genes. Sixty-four (86.5%) were symptomatic and the 10-year cumulative mortality was 27%. The two prevalent phenotypes are
long QT syndrome(LQTS;
CALM-LQTS, n = 36, 49%) and
catecholaminergic polymorphic ventricular tachycardia(CPVT;
CALM-CPVT, n = 21, 28%).
CALM-LQTS patients have extremely prolonged QTc intervals (594 ± 73 ms), high prevalence (78%) of life-threatening arrhythmias with median
ageat
onsetof 1.5 years [interquartile range (IQR) 0.1-5.5 years] and poor response to therapies. Most electrocardiograms (ECGs) show late onset peaked T waves. All
CALM-CPVT patients were symptomatic with median
ageof
onsetof 6.0 years (IQR 3.0-8.5 years). Basal ECG frequently shows prominent
U waves. Other
CALM-related phenotypes are
idiopathic ventricular fibrillation(IVF, n = 7), sudden unexplained death (SUD, n = 4), overlapping features of CPVT/LQTS (n = 3), and predominant neurological phenotype (n = 1). Cardiac structural abnormalities and neurological features were present in 18 and 13 patients, respectively. CONCLUSION: Calmodulinopathies are largely characterized by adrenergically-induced life-threatening arrhythmias. Available therapies are disquietingly insufficient, especially in
CALM-LQTS. Combination therapy with drugs,
sympathectomy, and devices should be considered.
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