Prevention of ventricular arrhythmias in the congenital long QT syndrome

Abstract

Life-long therapy is necessary for patients with symptomatic long QT syndrome to prevent arrhythmic death. The merits and limitations of the different therapeutic modalities are discussed. beta-blockers remain the mainstay of therapy, but this medication may not be sufficient for cardiac arrest survivors and for those with the LQT3 genotype. "Genotype-specific" therapy, like potassium-channel openers for patients with inadequate potassium outflow (LQT1 and LQT2 genotypes) or sodium-channel blockers for patients with excessive sodium inflow (LQT3), significantly shortens the QT interval, but the effects of these drugs on arrhythmia prevention is less well established. Cardiac pacemakers may be especially beneficial for patients with LQT2 or LQT3 and for those with pause-dependent torsade de pointes. More important is to recognize that device programming for preventing tachyarrhythmias in patients with long QT differs from the standard pacemaker programming. Finally, implantable defibrillators with dual-chamber pacing capability are indicated for patients at high risk for arrhythmic death, including all cardiac arrest survivors.

Recommendations for the Programming of Implantable Cardioverter-Defibrillators in New Zealand

“…Those with LQTS may also benefit from rate-smoothing algorithms [101] and a base pacing rate ≥70 bpm [102]. Available in Boston and Medtronic devices the rate-smoothing algorithm aims to reduce ventricular arrhythmia burden by minimising short-long-short intervals.…”

The Risk of Cardiac Events and Genotype‐Based Management of LQTS Patients

“…There were three classical modalities of treating LQTS: beta-adrenergic blocking agents (beta-blockers), 2,14,[45][46][47][48][49][50] elective pacing (pacemakers), [49][50][51][52] and left cervicothoracic sympathetic ganglionectomy. [53][54][55] Beta-blockers have been used as standard therapeutic and preventive measures in patients with clinical diagnosis of LQTS.…”

“…[53][54][55] Beta-blockers have been used as standard therapeutic and preventive measures in patients with clinical diagnosis of LQTS. 2,14,[45][46][47][48] The mechanism of beta-blocker action is to prevent the increase in repolarization dispersion induced by sympathetic stimulation. 26,27 Beta-blocker treatment is effective in about 60-70% of LQTS patients in all age groups.…”

The Long QT Syndrome

“…In patients who do not tolerate β-blockers because of symptomatic bradycardia, and in patients in whom this therapy may have limited usefulness as they tend to have torsades de pointes at low heart rate, the combination of β-blockers and cardiac pacing may be employed. Long-term treatment with β-blockers has shown to result in a significant reduction in the incidence of cardiac events in patients with LQTS [37,38]. During a 5-year period, the rate of cardiac events was significantly reduced either in probands (0.97 ± 1.42 events/year before vs 0.31 ± 0.86 events/year after initiation of β-blockers) or in affected family members (0.26 ± 0.84 events/year before vs 0.15 ± 0.69 events/year after initiation of β-blockers).…”