Prevention of ventricular arrhythmias in the congenital long QT syndrome

The pre-clinical discovery and development of osimertinib used to treat non-small cell lung cancer

Introduction: Osimertinib is currently the only FDA- and EMA-approved third-generation small-molecule epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI). It was initially indicated for second-line treatment of patients with metastatic EGFR T790M mutation-positive non-small cell lung cancer (NSCLC) and got approved for first-line treatment of EGFR activation mutation-positive metastatic NSCLC in 2018. Most recently, the FDA granted approval for the adjuvant treatment of patients with early-stage mutated EGFR NSCLC after tumor resection.Areas covered: This drug discovery case history focuses on the key studies that led to the preclinical discovery and development of osimertinib. The authors focus on published preclinical studies by scientists from AstraZeneca and highlight key events in the clinical development.Expert opinion: Although eventually compromised by the cellular plasticity of the tumor and the inevitable acquisition of drug resistance through the use of osimertinib, its key role in the treatment of NSCLC with specific EGFR mutations will be maintained in the near future. As the genome of EGFR is highly labile and since the rapid development of new mutants remains an issue, there is still room for improvement for the next generation of inhibitors.

Efficacy of ventricular pacing in the treatment of an arrhythmic storm associated with a congenital long QT mutation

Long QT syndrome in the infant with 2:1 atrioventricular block is a malignant form of disease associated with frequent torsade de pointes in some cases. Those patients that do not respond to antiarrhythmic therapy are particularly challenging to manage. Ventricular pacing in this patient population has been shown to reduce arrhythmic events. We report a case of a newborn with frequent torsade de pointes requiring defibrillation and cardiopulmonary resuscitation with immediate shortening of the QTc interval with ventricular pacing and subsequent resolution of torsade de pointes.

The risk of cardiac events and genotype-based management of LQTS patients

This review discusses the risk of cardiac events and genotype-based management of LQTS. We describe here the genetic background of long QT syndrome and the eleven different genes for ion-channels and a structural anchoring protein associated with that disorder. Clinical Background section discusses the risk of cardiac events associated with different LQTS types. Management and Prevention section describes in turn gene-specific therapy, which was based on the identification of the gene defect and the dysfunction of the associated transmembrane ion channel. In patients affected by LQTS, genetic analysis is useful for risk stratification and for making therapeutic decisions. A recent study reported a quite novel pathogenic mechanism for LQTS and suggested that treatments aimed at scaffolding proteins rather than specific ion channels may be an alternative to antiarrhythmic strategy in the future.

Effects of a rate smoothing algorithm for prevention of ventricular arrhythmias: Results of the Ventricular Arrhythmia Suppression Trial (VAST)

BACKGROUND

Rate smoothing, which is available in some pacemakers and implantable cardioverter defibrillators (ICDs), has been used to prevent Torsades de Pointes in patients with long QT syndrome. Its efficacy in general ventricular arrhythmia prevention has not been determined.

OBJECTIVES

The purpose of the Ventricular Arrhythmia Suppression Trial (VAST) was to prospectively investigate whether rate smoothing could significantly reduce the incidence of ventricular tachyarrhythmias in a large, broad population of patients with ICDs.

METHODS

Five hundred sixty-nine patients were enrolled at 57 participating centers and implanted with a commercially available Guidant ICD. A single-blinded crossover design was used in which each patient was randomized at implant to one of two treatment sequences: either rate smoothing on (RS On) followed by rate smoothing off (RS Off), or RS Off followed by RS On. This mode sequence was randomly determined and assigned in a 1:1 fashion using randomized permuted blocks by site. Each mode was followed for 6 months. Programming of rate smoothing was prescribed as 12% Down and 12% Up for the duration of the RS On period.

RESULTS

Of enrolled patients, 281 were randomized to RS Off followed by RS On, and 288 to RS On followed by RS Off. With RS On, 75 (23%) patients experienced a reduction in arrhythmias, 76 (23%) saw an increase in arrhythmias, and the remaining 176 (54%) had no difference. No significant difference (P = .58) in frequency of arrhythmias with RS On vs RS Off was found.

CONCLUSION

Rate smoothing does not result in a reduction in ventricular arrhythmias in a heterogeneous population of patients receiving ICDs.

Clinical and therapeutic aspects of congenital and acquired long QT syndrome

The long QT syndrome is characterized by prolongation of the corrected QT (QTc) interval on the surface electrocardiogram. It is associated with precipitation of a polymorphic ventricular tachycardia, torsade de pointes, which may cause sudden death. The syndrome is a disorder of cardiac repolarization caused by the alterations in the transmembrane potassium and sodium currents. Six genetic loci for the congenital forms of the syndrome have been identified; sporadic cases occur because of spontaneous mutations. Acquired causes of the long QT syndrome include drugs, electrolyte imbalance, toxins, marked bradycardia, subarachnoid hemorrhage, stroke, myocardial ischemia, protein-sparing fasting, autonomic neuropathy, and human immunodeficiency virus disease. Clinical symptoms are the result of the precipitation of torsade de pointes and range from such minor symptoms as dizziness to syncope and sudden death. Short-term treatment is aimed at preventing the recurrences of torsade de pointes and includes intravenous magnesium and potassium administration, temporary cardiac pacing, and correction of electrolyte imbalance; rarely, intravenous isoproterenol is indicated. Long-term management includes use of beta-blockers, permanent pacemaker placement, and cardioverter-defibrillator implantation. Asymptomatic patients are treated if under the age of 40 years at the time of diagnosis.

Long QT syndrome: diagnosis and management

BACKGROUND

Long QT syndrome (LQT) is characterized by prolongation of the QT interval, causing torsade de pointes and sudden cardiac death. The LQT is a disorder of cardiac repolarization caused by alterations in the transmembrane potassium and sodium currents. Congenital LQT is a disease of transmembrane ion-channel proteins. Six genetic loci of the disease have been identified. Sporadic cases of the disease occur as a result of spontaneous mutations. The acquired causes of LQT include drugs, electrolyte imbalance, marked bradycardia, cocaine, organophosphorus compounds, subarachnoid hemorrhage, myocardial ischemia, protein sparing fasting, autonomic neuropathy, and human immunodeficiency virus disease.

METHODS

Data on the diagnosis and management of LQT were thoroughly reviewed.

RESULTS AND CONCLUSIONS

The diagnosis of LQT primarily rests on clinical and electrocardiographic features and family history. The clinical presentations range from dizziness to syncope and sudden death. Genetic screening is available primarily as a research tool. Short-term treatment of LQT is aimed at preventing the recurrences of torsades and includes intravenous magnesium and potassium administration, temporary cardiac pacing, withdrawal of the offending agent, correction of electrolyte imbalance, and, rarely, intravenous isoproterenol administration. The long-term treatment is aimed at reducing the QT-interval duration and preventing the torsades and sudden death and includes use of oral beta-adrenergic blockers, implantation of permanent pacemaker/cardioverter-defibrillator, and left thoracic sympathectomy. Sodium channel blockers are promising agents under investigation. Electrocardiograms are recorded for screening of family members. The data favor treating asymptomatic patients, if <40 years old at the time of diagnosis, with beta-adrenergic blockers.