Abstract Body: Introduction:
Cardiac complications following ischemic stroke are common. The term "stroke-heart syndrome" describes new adverse cardiac events post-stroke, with QTc prolongation being the most frequent electrocardiographic abnormality. Elevated brain natriuretic peptide (BNP) levels, indicating myocardial damage and increased cardiac load, may lead to prolonged myocardial repolarization. This study examines the interaction between BNP levels and QTc interval and their impact on the short-term prognosis of stroke-heart syndrome patients.

Methods:
The study included patients who presented to the emergency department from January 2021 to July 2022 with acute ischemic stroke complicated by stroke-heart syndrome, defined as new-onset cardiac dysfunction within three days post-stroke, including acute coronary syndrome, heart failure, and arrhythmias. All patients underwent routine laboratory tests and ECG evaluations. QTc prolongation was defined as >430 ms for males and >450 ms for females. Patients were followed for three months, with outcomes including all-cause and cardiovascular-related mortality. The optimal BNP cutoff for predicting mortality was determined using ROC curve analysis. The relationship between BNP, QTc interval, and mortality was evaluated using Cox proportional hazards regression, with further assessment of the interaction between BNP and QTc interval.

Results:
The study included 448 patients, with 14 deaths during follow-up, 9 of which were cardiovascular-related. QTc prolongation was observed in 217 patients (48.44%), who also had significantly higher BNP levels (p=0.008). High BNP was significantly associated with QTc prolongation (OR, 1.90; 95% CI, 1.20-3.01, p=0.006)(Table 1). The optimal BNP cutoff was 122.5 pg/mL. High BNP increased the risk of all-cause mortality (HR, 5.94; 95% CI, 1.22-29.03, p=0.028), while QTc prolongation increased mortality risk only in patients with high BNP (HR, 2.22; 95% CI, 0.53-9.25, p=0.273; p for interaction <0.001)(Table 2). The group with QTc prolongation and high BNP had a significantly increased mortality risk compared to the control group (HR 4.92, 95% CI 1.03-23.39, p=0.045)(Figure 1).

Conclusions:
QTc prolongation and elevated BNP levels interact to influence short-term mortality in stroke-heart syndrome patients. In patients with high BNP levels, QTc prolongation is a potential mortality risk predictor. Monitoring and treatment adjustments are recommended for such patients to reduce mortality risk.