Interatrial block may raise risk for stroke in patients with no history of AF
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Key takeaways:
- Interatrial block was linked to higher likelihood of stroke in patients without prior atrial fibrillation.
- Whether patients with interatrial block but no AF should be treated with blood thinners is unclear.
Interatrial block was associated with elevated risk for stroke and other poor outcomes in patients with no history of atrial fibrillation, according to a retrospective study.
“Interatrial block (IAB) is an electrocardiographic pattern defined by a P-wave duration 120 ms, typically signifying delayed conduction between the right and left atria through Bachmann’s bundle. Although initially considered a benign finding, IAB is associated with thromboembolic risk,” Joshua Lampert, MD, cardiac electrophysiology fellow at Mount Sinai Hospital, and colleagues wrote. “Ultimately, IAB has emerged as a potentially interesting risk marker of adverse cardiovascular outcomes, but its impact on thromboembolic risk profile remains unclear.”
Image: Adobe Stock
Lampert and colleagues retrospectively analyzed 4,837,989 ECGs from 1,228,291 patients at five centers; there were 458,994 patients without prior AF.
Among those without prior AF, the prevalence of IAB was 19.6% and was highest in Black (26.1%) and white (20.9%) patients but lowest in Native American patients (9.2%), according to the researchers.
In a restricted mean survival time analysis adjusted for baseline clinical variables, medications and CHA2DS2-VASc score, IAB was independently associated with increased likelihood of stroke (restricted mean time lost ratio coefficient [RMTLRC] = 1.43; 95% CI, 1.35-1.51; tau = 1,895), mortality (RMTLRC = 1.14; 95% CI, 1.07-1.21; tau = 1,924), systemic thromboembolism (RMTLRC = 1.62; 95% CI, 1.53-1.71; tau = 1,897), HF (RMTLRC = 1.94; 95% CI, 1.83-2.04; tau = 1,921) and incident AF (RMTLRC = 1.16; 95% CI, 1.1-1.22; tau = 1,888), Lampert and colleagues found.
IAB remained associated with stroke risk even in patients with had no subsequent AF, the researchers wrote, noting that this finding “is particularly important because the role of anticoagulation in patients with IAB who do not exhibit AF has not been established.”
When adjusting for other risk factors, IAB was not associated with elevated stroke risk in patients with prior AF.
“IAB is associated with an approximately 44% increase in time lost free from stroke among patients without a history of AF whether or not AF was later detected,” Lampert and colleagues wrote. “Patients with IAB are more likely to experience stroke even when the CHA2DS2-VASc score is low. Further investigation is warranted to assess whether treating patients who exhibit IAB on the ECG without AF would have improved outcomes with anticoagulation, antithrombotic therapy or other strategies that are currently reserved for patients with documented AF.”
Editor’s Note: This article was updated on June 26, 2023 to correct the spelling of interatrial block. The Editors regret the error.
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