Tool calculates risk for life-threatening events in long QT syndrome
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Researchers have developed an online calculator to assess 5-year risk for life-threatening arrhythmic events in patients with long QT syndrome.
Methodology and validation of the University of Rochester long QT syndrome risk calculator was presented at the virtual Heart Rhythm Society Annual Scientific Sessions.
“Patients who are affected by long QT have quite a high risk of cardiac events,” Wojciech Zareba, MD, PhD, FACC, FESC, professor of medicine and director of heart research at the University of Rochester, New York, said during a press conference. “The definition of cardiac events traditionally consists of three parameters: syncopal events, aborted cardiac arrest and sudden death. However, between 20% and 40% of patients with long QT syndrome will have events between age 18 and age 40, which is quite high. When we limit the analysis to life-threatening events — aborted cardiac arrest and sudden death — this number is lower. Between ages 18 and 40, it ranges from 6% to 9% depending on genotype, but is still very high. This is why we want to develop restratification strategies to identify people at high risk.”
The researchers developed a model to predict 5-year risk for aborted cardiac arrest, sudden death or appropriate implantable cardioverter defibrillator shock in patients with long QT syndrome, patterned after the European Society of Cardiology risk model for hypertrophic cardiomyopathy.
To develop the model, Zareba and colleagues analyzed 1,288 patients from Rochester (mean age, 20 years; 56% women; mean QTc, 477 ms) with a single mutation of LQT1, LQT2 or LQT3 and followed them for a mean of 9.8 years. The model included prespecified time-dependent covariates of baseline-corrected QT, age, sex, syncope (never, syncope while off beta-blockers or syncope while on beta-blockers), beta-blocker use and genotype.
The researchers validated the model in a cohort of 1,481 patients with genotyped long QT syndrome from Pavia, Italy (mean age, 21 years; 52% women; mean QTc, 471 ms), who were followed for a mean of 7 years.
Life-threatening event rates were 0.33 per 100 person-years in the Rochester cohort and 0.45 per 100 person-years in the Italy cohort, Zareba said during the press conference.
Using the model, researchers identified combinations of factors that produced low 5-year risk for life-threatening events, defined as less than 4%; moderate risk, defined as 4% to 6%; and risk level that could indicate need for an ICD, defined as higher than 6%.
“The calculator which we created will enable this assessment for every physician,” Zareba said during the press conference. “They will be able to click and enter age, sex, QTc, beta-blocker information and syncope information, and they will get exact 5-year probability of sudden death or aborted cardiac arrest, which are the events we are fearful of. We will release this particular tool very soon.”
The score was not developed for patients with COVID-19 who may get long QT syndrome after treatment with hydroxychloroquine and/or azithromycin, but “we know well the risk factors for drug-induced QT prolongation, which are female sex, older age, lower level of potassium in the blood and concomitant treatment with other drugs for other cardiac conditions,” Zareba said during the press conference. “These typical risk factors we have used should suffice when applied to COVID patients.” – by Erik Swain
Reference:
Zareba W, et al. LBCT04-03. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 6-9, 2020 (virtual meeting).
Disclosure: Zareba reports he received research grants from Biotronik, Boston Scientific, EBR, Gilead and LivaNova and consults for Abbott and ERT.
Perspective
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Daniel J. Cantillon, MD, FACC, FHRS
In an elegant study, investigators from the University of Rochester and Italy developed and validated a 5-year risk score calculator tool for lethal arrhythmias among patients with long QT syndrome. The investigators appear to have been inspired by a similar 5-year risk score calculator for patients with hypertrophic cardiomyopathy.
The score is easy to use and can help physicians counsel patients with long QT syndrome on their risk for sudden cardiac arrest given the reasonably good C-statistics from the internal and external validation cohorts.
It’s unclear if the score can guide medical decision-making, including patient selection for ICDs, as the inspired model for hypertrophic cardiomyopathy does — providing the user both an estimated 5-year risk percentage and professional society recommendation on ICD. Further research would be required for this score to get to that point.
One inherent challenge for these predictive models is keeping up with the science in dynamic fields, while preserving the convenience of an easy-to-use tool. For example, the current ESC hypertrophic cardiomyopathy 5-year calculator does not use the patient’s scar burden by cardiac MRI as an input variable, which has been shown to be a very important determinant of risk in this patient population and remains part of the American Heart Association algorithm to guide ICD medical decision-making. While there is no immediate obvious example to parallel this among patients with long QT syndrome, most experts would agree they are similarly nuanced by science surrounding triggering events, exposure to QT-prolonging-drug therapies, circadian rhythm, etc.
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Zareba W, et al. LBCT04-03. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 6-9, 2020 (virtual meeting).
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