A molecular basis for cardiac arrhythmia: HERG mutations cause long QT syndrome

http://www.area-c54.it/public/standardization%20and%20interpretation%20ecg.pdf

AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society. Endorsed by the International Society for Computerized Electrocardiology.

https://www.cell.com/cell/pdf/0092-8674(95)90359-3.pdf

SCN5A mutations associated with an inherited cardiac arrhythmia, long QT syndrome

Background Mutations in potassium-channel genes KCNQ1 (LQT1 locus) and KCNH2 (LQT2 locus) and the sodium-channel gene SCN5A (LQT3 locus) are the most common causes of the long-QT syndrome. We stratified risk according to the genotype, in conjunction with other clinical variables such as sex and the length of the QT interval. Methods We evaluated 647 patients (386 with a mutation at the LQT1 locus, 206 with a mutation at the LQT2 locus, and 55 with a mutation at the LQT3 locus) from 193 consecutively genotyped families with the long-QT syndrome. The cumulative probability of a first cardiac event, defined as the occurrence of syncope, cardiac arrest, or sudden death before the age of 40 years and before the initiation of therapy, was determined according to genotype, sex, and the QT interval corrected for heart rate (QTc). Within each genotype we also assessed risk in the four categories derived from the combination of sex and QTc (<500 msec or ≥500 msec). Results The incidence of a first cardiac event bef...

https://www.nejm.org/doi/pdf/10.1056/NEJMoa022147

Risk Stratification in the Long-QT Syndrome

Homogeneity of recovery time protects against arrhythmias whereas dispersion of recovery time is arrhythmogenic. A single surface electrocardiographic QT interval gives no information on recovery time dispersion but the difference between the maximum and minimum body surface QT interval may be relevant. This hypothesis was tested by measuring the dispersion of the corrected QT interval (QTc) in 10 patients with an arrhythmogenic long QT interval (Romano Ward and Jervell and Lange-Nielsen syndromes or drug arrhythmogenicity) and in 14 patients without arrhythmias in whom the QT interval was prolonged by sotalol. QTc dispersion was significantly greater in the arrhythmogenic QT group than in the sotalol QT group. In patients with prolonged QT intervals, QT dispersion distinguished between those with ventricular arrhythmias and those without. This supports the hypothesis that QT dispersion reflects spatial differences in myocardial recovery time. QT dispersion may be useful in the assessment of both arrhythmia risk and the efficacy of antiarrhythmic drugs.

https://heart.bmj.com/content/heartjnl/63/6/342.full.pdf

QT dispersion: an indication of arrhythmia risk in patients with long QT intervals.

IN a preliminary attempt (which requires considerable modification) to determine from blood-pressure records the relative influence of the heart action and of vaso-canstriction, I suggestedS that it might be necessary to estimate the duration of ventricular systole for different heart rates. In order to obtain this information a number of measurements have been made of electrocardiographic curves, including some obtained by myself and a selection of curves from Dr. T. Lewis’s collection, which he very kindly put at my disposal. Electrical records have been preferred to mechanical, because it is easier to secure accuracy, and it has been shown by many workers that as a rub the electrical and mechanical changes correspond fairly closely. Lewis ,*7 in a comparison of the heart sounds with the electrical changes, found the first sound to commence 0.011 of a second to 0.039 of a second after the commencement of Q, while the second sound started either before or after the end of T but usually within 0.01 of a second of it. WiggersYS1 working with dogs, found the mechanical systole to commence 0.03 to 0.045 after the rise of R, and to terminate 0.034 to 0.048 after the end of T, so that as a rule the two changes corresponded in duration, but he found that adrenalin shortens the duration of the mechanical change more than the electrical, and under these conditions the ventrical contrsction ended before the end of the T wave. In considering, therefore, the relative duration of systole and diastole, both electrical and mechanical records are useful, if these differences be allowed for. Walleflsgivee the following values for the durebtion of mechanical systole with different heart rates, and it will be seen that almost exactly similar figures are obtained by calculation from the formula systole = K Vcycle, where K hae 8 value of 0.343.

H. C. Bazett

Papers

An analysis of the time-relations of electrocardiograms

An analysis of the time-relations of electrocardiograms.