Brief Review of the Recently Described Short QT Syndrome and Other Cardiac Channelopathies

Abstract

There are many diseases related to ion-channel disorders, so-called "channelopathies." Hereditary short QT syndrome is a clinical-electrocardiographic entity with autosomal-dominant mode of transmission and it is the most recently described channelopathy. The syndrome may affect infants, children, or young adults with strong positive family background of sudden cardiac death. Short QT syndrome is characterized by short QT and heart-rate-corrected QTc intervals. It is frequently associated with tall-, peaked-, and narrow-based T waves that are reminiscent of the typical "desert tent" T waves of hyperkalemia. There is a high tendency for paroxysmal atrial fibrillation due to the heterogeneous abbreviation of action potential duration and refractoriness of atrial myocytes. The arrhythmia can also be induced by programmed electrical stimulation. The safest treatment suggested is an implantable cardioverter defibrillator, though the possibilities of inappropriate shocks have caused some concern, especially in teenagers. The ability of quinidine to prolong the QT interval has the potential to be an effective therapy for patients with short QT syndrome. This is particularly important in developing countries, where the implantable cardioverter-defibrillator therapy is not always available. Since these patients are at risk of sudden cardiac death from birth, and implantable cardioverter-defibrillator implantation has a lot of limitations in very young children, the utility of quinidine has to be evaluated further. Clinicians need to be aware of this deadly electrocardiographic (ECG) pattern as it portends a high risk of sudden cardiac death in otherwise healthy subjects with structurally normal hearts.

Short QT Syndrome

“…ECG documentation of asymptomatic atrial fibrillation: A high incidence of paroxysmal atrial fibrillation was noted on review of patients with short QT syndrome, 18 presumably related to the short effective refractory period of the atria. 15,17 Thus, in young patients with "lone" atrial fibrillation, a short QT interval should be excluded.…”

Acquired Long QT Syndrome: Frequency, Onset, and Risk Factors in Intensive Care Patients

“…3 Channel opathies are conditions caused by malfunction of these ion channels or the proteins that regulate the channels, leading to cardiac electrical disorders. 4,5 T he heart contains 2 types of cells: cells that generate the electrical activity (conduction system) and muscle cells that contract in response to the electrical activity. The contractions, or beats, are coordinated by a network of specialized, autorhythmic cells integrated within the contractile myocytes.…”

Targeting Potassium Channels: New Advances in Cardiovascular Therapy

“…It can be clinically characterized by major (cardiac arrest, syncope and sudden cardiac death) or minor (palpitations and/or dizziness secondary to bursts of paroxysmal atrial fibrillation) cardiac events [38].…”

“…However, this concept is not completely restricted to genetic disorders. Functional ionic disturbances induced by punctual or chronic use of drugs with undesirable proarrhythmic effects have been widely reported [36][37][38][39]. …”