What is severity of QTc prolongation?
What is severity of QTc prolongation?
There is no threshold of QTc prolongation at which TdP is certain to occur. A QTc greater than 500 milliseconds (ms) has been associated with a twofold to threefold higher risk for TdP, and each 10-ms increase contributes to approximately a 5% to 7% exponential increase in risk.
How is QTc prolongation treated?
Several medications may help treat QT prolongation. A doctor may prescribe beta-blockers to help slow the heart rate or antiarrhythmic drugs to help shorten the QT interval. People may also consider dietary supplementation with potassium. Diuretics are one class of drugs that may cause QT prolongation.
What causes prolonged QTc intervals?
Risk factors Using medications known to cause prolonged QT intervals. Being female and on heart medication. Excessive vomiting or diarrhea, which causes electrolyte imbalances. Eating disorders, such as anorexia nervosa, which cause electrolyte imbalances.
Which drugs cause torsades Depointes?
Other drugs that prolong the QT interval and have been implicated in cases of torsade include phenothiazines, tricyclic antidepressants, lithium carbonate, ziprasidone, cisapride, highly active antiretroviral drugs, high-dose methadone, anthracycline chemotherapeutic agents (eg, doxorubicin, daunomycin), some …
What is the normal range for QTc?
Many formulas are used to correct QT interval for heart rate. The Bazett formula (QTc=QT/RR½) is one of them. Normal QTc interval is 350–450 ms in males and 360–460 ms in females. QTd is the difference between the longest and shortest QT interval on standard ECG.
What does a high QTc mean?
An abnormally prolonged QTc interval (>450 ms in men, >470 ms in women) was associated with a three-fold increased risk of sudden cardiac death (hazard ratio, 2.5; 95% confidence interval, 1.3 to 4.7), after adjustment for age, gender, body mass index, hypertension, cholesterol/high-density lipoprotein ratio, diabetes …
Who is at risk for QT prolongation?
Factors that predispose to QT prolongation and higher risk of torsades de pointes include older age, female sex, low left ventricular ejection fraction, left ventricular hypertrophy, ischemia, slow heart rate, and electrolyte abnormalities including hypokalemia and hypomagnesemia.
Why is magnesium used for torsades?
Pulseless torsades should be defibrillated. Intravenous magnesium is the first-line pharmacologic therapy in Torsades de Pointes. Magnesium has been shown to stabilize the cardiac membrane, though the exact mechanism is unknown. The recommended initial dose of magnesium is a slow 2 g IV push.
What is the most common cause of torsades de pointes?
Common causes for torsades de pointes include drug-induced QT prolongation and less often diarrhea, low serum magnesium, and low serum potassium or congenital long QT syndrome. It can be seen in malnourished individuals and chronic alcoholics, due to a deficiency in potassium and/or magnesium.
What does QTc mean on ECG?
Abstract. QT corrected for heart rate (QTc) interval reflects ventricular repolarization, and its prolongation can lead to fatal ventricular arrhythmias. Studies on obese patients report a prolonged QTc interval as well as an increased rate of sudden cardiac death when compared with lean individuals.
