Electrocardiographic marker linked to stroke risk
MedWire News: People with a prolonged QT interval have an increased risk for stroke, suggest findings from a prospective, community-based study.
A prolonged QT interval has been reported in 38% to 71% of patients with acute stroke, but the current findings from the REasons for Geographic and Racial Differences in Stroke (REGARDS) Study suggest it could be a pre-existing, and even predisposing, factor.
"These findings add further concern regarding the consequences of QTc prolongation," say Elsayed Soliman (Wake Forest School of Medicine, Winston-Salem, North Carolina, USA) and co-workers.
"In addition to increased cardiovascular morbidity and mortality, stroke seems to be another serious outcome."
During a median of 5.1 years of follow up, 608 of the 27,411 REGARDS participants (aged at least 45 years) had a stroke, 491 of whom had ischemic strokes.
At baseline, 740 participants had a prolonged QT interval corrected for heart rate (QTc), which was calculated using the Framingham formula and defined as at least 460 ms in women and 450 ms in men. In all, 5.4% of these participants had a stroke, compared with just 2.8% of those with a normal QT interval.
This equated to a 2.88-fold increased stroke risk associated with a prolonged QT interval. The association remained significant after accounting for demographics, stroke risk factors, medication, QRS duration, and use of QTc-prolonging drugs, at a 1.67-fold increase.
Each standard deviation increase in QTc interval was associated with a 12% increase in stroke risk after accounting for confounders, the team reports in the Journal of the American College of Cardiology.
The uncorrected QT internal did not predict stroke, and neither did heart rate, indicating that the association between stroke and QTc was not driven by heart rate.
Soliman et al note that, as with left ventricular hypertrophy, it is not clear whether prolonged QTc interval is itself a pathologic factor leading to stroke, represents a marker for a different underlying process, or is an adaptive response.
But they say: "With the increasing number of QTc-prolonging drugs and in light of our results, examining the risk of stroke associated with QTc-prolonging drugs may be warranted."
By Eleanor McDermid