Predicts risk of QT prolongation in hospitalized patients
Primary source: Tisdale JE et al. Circ Cardiovasc Qual Outcomes 2013; 6: 479-487
The Tisdale score (Tisdale JE et al., Circ Cardiovasc Qual Outcomes, 2013) is a clinical tool for assessing the risk of QTc prolongation in hospitalized patients in cardiac/intensive care settings. It is particularly relevant before starting QT-prolonging drugs during hospitalization.
It uses 7 factors with weighted points: age ≥ 68 years (1), female sex (1), loop diuretics (1), potassium ≤ 3.5 mmol/L (2), QTc on admission ≥ 450 ms (2), acute MI (2), sepsis (3), heart failure (3), 1 QT-prolonging drug (3), ≥ 2 QT-prolonging drugs (6) — maximum 21.
Interpretation: ≤ 6 points is low risk (~15%), 7-10 is moderate risk (~37%), ≥ 11 is high risk (~73%). At high risk, an alternative drug is recommended, along with ECG monitoring every 8-12 hours and active electrolyte correction (K > 4.0, Mg > 0.8 mmol/L).
A 74-year-old woman with heart failure with reduced ejection fraction is admitted with pneumonia. She is started on azithromycin and furosemide. Potassium 3.3 mmol/L, QTc on admission 460 ms.
Age ≥ 68 (1) + female sex (1) + loop diuretic (1) + potassium ≤ 3.5 (2) + QTc ≥ 450 (2) + heart failure (3) + 1 QT-prolonging drug — azithromycin (3) = 13 points.
High risk of QTc prolongation (~73%). Management: switch azithromycin to a safer antibiotic (amoxicillin-clavulanate), correct hypokalemia (KCl to target ≥ 4.0 mmol/L), give magnesium if < 0.8 mmol/L. Daily ECG monitoring.
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