QTc calculator

n1 (number of small boxes between QT interval)

x 0.04 s/small box =

QT interval, seconds

n2 (number of small boxes between RR interval)

x 0.04 s/small box =

RR interval, seconds

n1 = 9

n2 = 24

OR

Heart rate (if regluar rhythm), beats/minute

QTc (Bazett fomula) = QT/sqr(RR)

QTc (Fridericia fomula) : Cardio-oncology = QT/CBRT(RR)

QTc (Framingham fomula) = QT+ 0.154 * (1-RR)

QTc (Hodges formula) = QT + (0.00175 * (60/RR) - 60 ))

Congenital long QT syndrome

Acquired causes of long QT

Anorexia nervosa, Alcohol

Bradycardia, Brain

Coronary artery disease, Cardiomyopathy

Drugs (see below), Diet (liquid protein)

Electrolyte imbalance (hypokalemia, hypocalcemia, hypomagnesemia), Endocrine (hypothyroid)

Anti-Arrhythmics e.g. procainamide, disopyramide, Amiodarone, Sotalol

Anti-Anginals e.g. Ranolazine

Anti-Biotics e.g. Macrolides, Fluoroquinolones, Bactrim, azoles

Anti-psyChotics: 1st gen>2nd gen (chlorpromazine, haloperidol, risperidone)

Anti-Depressions: SSRIs, TCAs

Anti-Emetics: (5-HT3 antagonists) ondansetron, also droperidol