Table 6.
Purpose: To prevent long QTc interval, Torsade de Pointes causing polymorphic ventricular tachycardia and sudden cardiac deaths. | ||
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Step | Particulars | Action |
1 | Check: known drug allergy congenital long QT syndrome (occurs in 1:7000) |
Drug contraindicated |
2 | Check: drug interaction refer to Table 4, Table 5 for a list of drugs that have a drug interaction with CQ or HCQ |
Stop non-essential drugs that have a drug interaction |
3 | Check: the risk score for QTc prolongation total score: 21. Score ≤ 6 (risk low, chance 15%); 7–10 (risk moderate, chance 37%); ≥ 11 (risk high, chance 73%) Risks include: age ≥ 68 years - 1, female gender - 1, concomitant loop diuretic - 1, serum K+ ≤ 3.5 mEq/L - 2, admission QTc ≥ 450 ms - 2, acute MI - 2, sepsis - 3, heart failure - 3, one QTc-prolonging drug - 3, ≥ 2 QTc-prolonging drugs – 3, additional points i.e. 6 |
Drug contraindicated when risk is high (score ≥ 11) |
4 | Calculate baseline QTc: {QT interval - start of the Q wave to the end of the T wave; QTc = QT / √ RR, use an app to calculate QTc. Normal ≤ 430 ms (male)/≤ 450 ms (female)}(75) |
Drug contraindicated if baseline QTc ≥ 500 ms |
5 | Monitor: serum K+ and Mg+ use of loop diuretics |
Correct electrolyte imbalance |
6 | Plan: interval ECG (12 hourly) or cardiac telemetry in sick patients interval ECG in ambulatory subjects |
Reduce dose if QTc prolongs, stop the drug if QTc ≥ 500 ms |
In case of Torsade de Pointes: stable tachycardia - give magnesium sulfate 1–2 g IV x 15 min not responsive - give isoproterenol 2–10 mcg/min infusion or pacing to a rate of 100–120 depolarizations/minute as required to suppress PVC, usually terminates Torsade de Pointes |
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Tisdale JE, et al. Circ Cardiovasc Qual Outcomes 2013;6:479–87.