Friday, June 8, 2007

Electrophysiology roundup

Electrophysiology roundup

A recent review from the Journal of the American College of Cardiology on developments in the field of electrophysiology during the year 2006 was posted in Medscape May 21. I thought it was worth linking here, as it contains several items of general clinical interest. Some highlights follow.
Cardiac channel disorders continue to garner interest. Despite the discovery of new mutations leading to the long QT syndrome (LQTS) some 25% of patients with LQTS have no identifiable genetic abnormality. Brugada syndrome is increasingly well understood. The channelopathies of Brugada syndrome appear to cause a gradient between endocardium and epicardium caused by disparities in phase 1 of their respective action potentials. In contrast to the LQTS, relatively few patients with Brugada syndrome (20%-30%) have an identified genetic abnormality.
One study referenced in the review is interesting, to me anyway, not because of any immediate clinical relevance but because it’s an example herbal research done right. Investigators created a Brugada syndrome phenotype in isolated perfused canine right ventricular tissue. Drawing on prior research showing that dimethyl lithospermate B (dmLSB), a minor component of the root extract of the Danshen plant, is capable of decreasing inactivation of the sodium current INa, the researchers demonstrated reversal of the Brugada phenotype by adding dmLSB to the perfusate. Basic research such as this may pave the way for novel drug therapies for cardiac channelopathies
Recent research in Brugada syndrome has also made it increasingly evident that the electrocardiographic findings may fluctuate over time, often necessitating multiple tracings to diagnose, classify and risk stratify patients.
Genetic abnormalities, both germ line and somatic, also underlie non lethal conditions. Recent findings relating to genetic causes of sick sinus syndrome and somatic mutations in atrial fibrillation were presented.
Finally, nonantiarrhythmic drugs are increasingly being found to prevent arrhythmias. A meta-analysis cited in the review found that treatment with angiotensin converting enzyme inhibitors and angiotensin receptor blockers decreases the new onset of atrial fibrillation in patients with and without heart failure. The review cited prior studies indicating that statin drugs prevent atrial fibrillation and a recent study of patients with coronary artery disease and implanted defibrillators showing that administration of 80mg daily of atorvastatin decreases episodes of device intervention by 50%.


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