Introduction

The QT interval on the electrocardiogram (ECG) represents the summation of action potentials in ventricular myocytes, comprising ventricular depolarization and repolarization [1, 2].  Long QT syndrome (LQTS) is a cardiac conduction disorder characterized by prolongation and increased dispersion of ventricular repolarization, manifested by lengthening of the QT interval on the surface electrocardiography (ECG). This abnormal repolarization, when amplified by sympathetic activity, can lead to the formation of reentry circuits and may present with syncope, seizures, or torsades de pointes (TdP), ventricular fibrillation and, therefore sudden cardiac death [3].

Prolongation of the QT interval can be congenital or acquired, is frequently drug-related, and is thus of concern  in the clinical drug use [4, 5]. Drug induced heart-rate corrected QT (QTc) interval duration of more than 500 ms predicts short term mortality independent of comorbidities [6]. Also for non-antiarrhythmic drugs a thorough assessment of drug effects on the QTc interval is required and of importance for safe clinical drug use [9].

 In regular follow up in both indoor and OPD patients for Qt prolongation should be done which is easily missed. Drugs can be distinguished into the following groups depending on their simultaneous effects on the QT corrected using the Bazzet’s formula (QTc) interval. Moreover, an ECG at rest is always needed to reveal a QT prolongation. Electrolytes should be normalized. Among these drugs, some commonly used drugs used on  daily basis  are atropine , Anti-anginal Ranolazine, Anti-arrhythmic Sotalol, Quinidine, Amiodarone, Ibutilide, Disopyramide, Procainamide, Flecainide,  Amiadarone, Antibiotic Moxifloxacin, Ciprofloxacin, Gemifloxacin, Ofloxacin, Levofloxacin other fluoroquinolones, Trimethoprim-Sulfa, Azithromycin, Erythromycin, Clarithromycin, Anti-convulsant Fosphenytoin, Anti-depressant  Citalopram, Fluoxetine, Sertraline, Escitalopram, Amitriptyline, Anti-fungal Voriconazole, Fluconazole, Ketoconazole, Itraconazole. Antihistamine Astemizole, Terfenadine, Diphenhydramine, Anti-hypertensive Nicardipine, HCTZ Anti-malarial Chloroquine, Halofantrine, Anti-mania Lithium, Anti-nausea/antiemetic Ondansetron Anti-psychotic Clozapine, Haloperidol, Chlorpromazine, Anti-viral Foscarnet, Ritonavir, Appetite suppressant Phentermine, Fenfluramine, Bronchodilator/decongestant Albuterol, Salmeterol, Terbutaline, Levalbuterol, Diuretic Indapamide  Cisapride H2-receptor antagonist Famotidine Inotropic agent/vasconstrictor Dopamine, Isoproterenol, Dobutamine, Epinephrine, Norepinephrine, Phenylephrine Local anesthetic Sedative; Anti-nausea/anesthesia  Vasconstrictor Midodrine. Both intubation and extubation may trigger a TdP in patients with LQTS the use of lidocaine before intubation proved to be safe to prevent arrhythmias.

The QT interval duration is physiologically variable, the QTc is calculated using the Bazett’s formula [(QTc = QT/√RR) [7]. Genetic testing can help to recognize specific subtypes of c-LQTS. The most common phenotypes are LQT1, LQT2 and LQT3. The QT interval on the electrocardiogram is the time from ventricular depolarization to ventricular repolarization. When this interval becomes prolonged, it indicates delayed cardiac repolarization [19].

QTc Interval has demographic  and diurnal Variations, normal QTc values are generally <450 ms in men and <460 ms in women, while a QTc >500 ms is associated with increased mortality. QTc duration varies with age and sex, being longest during the neonatal period and shortening during adolescence, particularly in males due to testosterone-related effects. In adulthood, QTc is typically 12 to 15 ms shorter in men than in women; however, this sex difference diminishes after 40 years of age and disappears in the elderly. QTc also exhibits circadian variation, with a mean daily fluctuation of approximately 24 ms (range 10 to 47 ms) [10], likely due to neurohumoral and diurnal influences. Similar circadian patterns are observed in cardiovascular events, including sudden cardiac death [11], which peaks in the early morning hours around 3 am [8, 9]. In general, QTc-prolonging drugs are contraindicated in patients with congenital LQTS or baseline QTc >500 ms and have to be used with caution when preexisting acquired QT prolongation is known [20]. Also the drug-specific risk potential has to be considered [21].

Objevtive

• To evaluate QT interval prolongation caused by drugs used in emergency cardiac care
• To study the clinical profile of patients with QT prolongation.
• To compare QT prolongation between male and female patients.
• To identify associated risk factors in coronary artery disease patients.

Methods

This was an observational study including 96 patients admitted in the emergency setting.

All patients who showed QTc prolongation on follow-up ECG during hospital stay were included.

QT interval was measured from the beginning of the Q wave to the end of the T wave, and the corrected QT interval (QTc) was calculated using Bazett’s formula, which is QT divided by the square root of the RR interval.QT and QTc are documented at the time of presentation and QT2 and QTc2 are prolonged QTc interval documented Electrolytes were normalized.

Clinical data collected included age, gender, presenting symptoms, diagnosis, risk factors such as diabetes and hypertension, and left ventricular ejection fraction.

Results

Results there was no statistically difference between  male and female and p value was not significant, even on basis of age   the p value was not significant. Also for non-antiarrhythmic drugs a thorough assessment of drug effects on the QTc interval is required and of importance for safe clinical drug use [9]. When studying clinical concentration-QTc relationships, a quantitative understanding of variability, including variations in measurement techniques, heart-rate correction, and other clinical influencing factors is of importance. Furthermore, the relationship between quantified effects on the QTc interval and expected risk of life-threatening events need to be understood.

A total of 96 patients were included in the study.

• 54 were males
• 42 were females

The most common age group was 31–40 years, accounting for about 31% of cases. Regarding symptoms:

• Around 65% presented with chest pain
• 32% had shortness of breath
• A small proportion had palpitations

In terms of diagnosis:

• 35 patients had acute coronary syndrome
• 12% had coronary artery disease on medical therapy
• 4% were admitted for routine angioplasty

Regarding cardiac function:

• 48% had LVEF less than 40%
• 33% had LVEF between 41–50%
• 19% had LVEF between 51–60%

Risk factor analysis showed:

10% were hypertensive

16% were diabetic

4% had both diabetes and hypertension

Clinical Importance

Several commonly used medications can contribute to QT prolongation, including:

• Antiarrhythmic drugs such as amiodarone and sotalol
• Antibiotics such as azithromycin and fluoroquinolones
• Antiemetics like ondansetron
• Certain antidepressants and antipsychotics

When multiple drugs are administered simultaneously in cardiac patients, gradual QT prolongation may go unnoticed until a serious arrhythmia develops.