What is qt prolongation

A quick way to distinguish a prolonged QT interval is to examine if the T wave ends beyond the halfway point between the RR interval. If the T wave ends past the halfway point of the RR interval, it is prolonged. The QTc is considered prolonged if greater than ms in males and ms in females. Enlarge Prolongation of the QT interval can result from multiple medications, electrolyte abnormalities — hypocalcemia , hypomagnesemia and hypokalemia — and certain disease states including intracranial hemorrhage.

Long QT syndrome can run in families. A typical heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of the heart. The heart valves, which keep blood flowing in the right direction, are gates at the chamber openings. Long QT syndrome is a heart rhythm disorder caused by abnormalities in the heart's electrical recharging system.

The heart's structure is normal. Normally, the heart sends blood out to the body during each heartbeat. The heart's chambers contract and relax to pump the blood. This coordinated action is controlled by your heart's electrical system. Electrical signals impulses travel from the top to the bottom of your heart and trigger it to contract and beat.

After each heartbeat, the system recharges itself to prepare for the next heartbeat. In long QT syndrome, your heart's electrical system takes longer than normal to recharge between beats. More than 17 genes have been linked to long QT syndrome so far, and researchers have identified hundreds of mutations within these genes.

More than medications — many of them common — can lengthen the QT interval in otherwise healthy people and cause acquired long QT syndrome. If your condition is caused by a medication, it may be called drug-induced long QT syndrome. Always tell your doctor about all the medications you take, including those you buy without a prescription. The following things may increase your risk of developing congenital or acquired long QT syndrome or its symptoms:. Sexual intercourse doesn't appear to be high risk for patients with long QT syndrome.

Pregnancy and delivery aren't associated with an increased risk of symptoms in women diagnosed with long QT syndrome. However, if you have the condition and are pregnant, your doctor will want to carefully monitor you during and after pregnancy.

Proper medical treatment and lifestyle changes can help prevent complications related to long QT syndrome. Torsades de pointes 'twisting of the points'.

This is a life-threatening form of ventricular arrhythmia. Your heart's two lower chambers ventricles beat fast and chaotically, making the waves on an ECG monitor look twisted. The heart pumps out less blood. The lack of blood to the brain causes you to faint suddenly and, often, without warning. If the episode lasts for a long time, fainting can be followed by a full-body seizure.

If the dangerous rhythm does not correct itself, then a life-threatening arrhythmia called ventricular fibrillation follows. Congenital long QT syndrome is caused by a genetic mutation. Terfenadine and astemizole were found to have proarrhythmic effects, which led to their withdrawal from the market in and , respectively.

Newer nonsedating antihistamines e. When used in combination with drugs that inhibit metabolism, or if overdose occurs, the risk is increased. Drug Interactions Both pharmacokinetic and pharmacodynamic drug interactions can significantly increase the risk of QT prolongation. Pharmacists may help reduce the risk of serious ventricular arrhythmias by screening for potential interactions.

Furthermore, it is intuitive that inhibiting the metabolism of these commonly associated medications can significantly increase the risk for QTc prolongation or TdP. The drug interactions listed in Table 3 are likely to increase a patient's risk for QTc prolongation, further leading to TdP. For example, prior to terfenadine's withdrawal from the market, the QTc prolongation associated with this drug was estimated to be about 8 to 18 milliseconds.

When studied along with the administration of ketoconazole, a 3A4 inhibitor, the QTc interval increased by 82 milliseconds. Pharmacodynamic: Pharmacodynamic interactions may also lead to QT prolongation. These interactions occur as a result of synergistic or antagonistic pharmacologic properties. Several drugs are known to cause QT prolongation see Table 2 ; the potential risk increases when such drugs are used in combination.

Risks Versus Benefits Risks and benefits should be assessed when selecting medications known to prolong QT interval. Of course, the benefits of certain medications may far outweigh the risks associated with their use.

For example, arsenic trioxide, although known to induce arrhythmia, may be necessary for the treatment of acute promyelocytic leukemia. However, it is important to note that generally, in other cases, a safer alternative may be available.

The incidence of QT prolongation and TdP is well documented with the antiarrhythmic agents. Although they are beneficial for the acute termination of an arrhythmia, there has been little documentation supporting their use for chronic management of arrhythmias.

As previously mentioned, it is important to assess the nonpharmacologic risk factors Table 1 when selecting a medication that has been associated with QT prolongation. Close monitoring is particularly necessary when choosing to use QT-prolonging drugs within this population of patients at risk.

Patients should be counseled about the potential risks associated with these medications and informed of the symptoms of arrhythmia. Patients should seek medical attention if symptoms such as lightheadedness, dizziness, palpitations, shortness of breath, or syncope occur. Conclusion Although QT prolongation has been linked to the use of certain drugs, it remains difficult to predict the relative risk associated with their administration.

Pharmacists can make recommendations to clinicians to help promote safer prescribing practices when selecting QT-prolonging drugs. Drugs that have QT-prolonging effects should not exceed recommended dosing range, as drug-induced arrhythmia is often a result of high drug concentrations.

In addition, these medications should be prescribed with caution in patients who have underlying risk factors, such as cardiac disorders. Screening for potential drug interactions and electrolyte abnormalities may also help lead to safer therapies, potentially preventing the development of ventricular arrhythmias.

References 1. This type of surgery involves implanting a battery powered device called an implantable cardioverter defibrillator ICD under the skin. ICDs can detect abnormal heart rhythms and respond by delivering electric shocks to correct the arrhythmia.

This surgery is an alternative option for people with long QT syndrome who faint while taking beta-blockers. QT prolongation is the medical term for an extended interval between the heart contracting and relaxing. QT prolongation can be present from birth, or it may develop later in life. People with QT prolongation do not usually experience any symptoms of the condition. In most cases, a doctor discovers the condition during a routine medical exam.

An ECG can usually confirm the diagnosis. Treatment for QT prolongation may include medications, lifestyle changes, and surgery. A person can discuss all the potential treatment options with a doctor. Learn more about the definition, procedure, and results here. Atrial fibrillation, or A-fib, can lead to fatal heart complications if it reaches a severe enough stage. A doctor can identify some types of atrial…. Several situations and medical conditions can cause abnormal EKG results, including electrolyte imbalances and irregular heart rhythms.

Learn more in…. Torsades de pointes is an uncommon type of ventricular tachycardia that can be potentially life-threatening. Learn more about the causes and diagnosis. Arrhythmia means an irregular heartbeat. Diagnosing it is critical, as arrhythmia can indicate severe heart damage. Learn about types of arrhythmias….