A shortened QT interval may be caused by what condition?

A shortened QT interval may be caused by what condition?

• A. Electrolyte imbalance
• B. Excess digitalis (digitalis toxicity)
• C. Ventricular hypertrophy
• D. Heart failure

Answer: (B)

A shortened QT interval is most commonly associated with the effects of excess digitalis, which can lead to various alterations in cardiac conduction. Digitalis, a medication often used to treat heart failure and certain arrhythmias, has a known effect on the cardiac action potential. It primarily increases vagal tone (parasympathetic effect) on the heart, which can result in a decrease in the duration of the QT interval. When digitalis levels rise excessively, the impact on the myocardial cells can cause changes in repolarization dynamics, typically leading to a distinct shortening of the QT interval on the electrocardiogram. This distinct alteration is what makes digitalis toxicity a noteworthy cause of a shortened QT interval. Other conditions like electrolyte imbalances and ventricular hypertrophy can indeed influence the QT interval, but they often result in prolongation or variable changes rather than a shortening. In the case of heart failure, while it might modify the overall electrical activity of the heart, it typically does not specifically correlate with a shortened QT interval as directly as does digitalis toxicity.

A shortened QT interval is most commonly associated with the effects of excess digitalis, which can lead to various alterations in cardiac conduction. Digitalis, a medication often used to treat heart failure and certain arrhythmias, has a known effect on the cardiac action potential. It primarily increases vagal tone (parasympathetic effect) on the heart, which can result in a decrease in the duration of the QT interval.

When digitalis levels rise excessively, the impact on the myocardial cells can cause changes in repolarization dynamics, typically leading to a distinct shortening of the QT interval on the electrocardiogram. This distinct alteration is what makes digitalis toxicity a noteworthy cause of a shortened QT interval.

Other conditions like electrolyte imbalances and ventricular hypertrophy can indeed influence the QT interval, but they often result in prolongation or variable changes rather than a shortening. In the case of heart failure, while it might modify the overall electrical activity of the heart, it typically does not specifically correlate with a shortened QT interval as directly as does digitalis toxicity.