Long QT syndrome refers to the prolongation of a patient's QT interval, at greater than 450 milliseconds for men and greater than 470 milliseconds for women. At intervals above 500 milliseconds, the risk of cardiac events is significantly multiplied as QTc prolongation predisposes individuals to ventricular tachyarrhythmias like TdP, ventricular fibrillation, and resulting death. LQTS may be inherited, or acquired due to drug effects or electrolyte changes.

Long QT Syndrome (LQTS)

A patient's QTc interval reflects the time it takes for ventricular depolarization and repolarization to occur, measured from the beginning of the QRS complex to the end of the T wave, corrected for their heart rate. In other words, it represents the time needed for the heart to reset between beats.

Kalamazoo College

Hypokalemia, or low serum potassium, from malnutrition or purging may predispose anorexia nervosa patients to sudden cardiac death. Low potassium has the potential to contribute to QTc prolongation, which may trigger TdP.  Especially in conjunction with elevated serum aldosterone levels which further exacerbate it, hypokalemia has the potential to lead to deadly outcomes. Furthermore, low potassium may also indicate refeeding syndrome, which can lead to death by acute heart failure.

Hypokalemia and Sudden Cardiac Death in Anorexia Nervosa Patients

Purging via self-induced vomiting or abuse of laxatives or diuretics leave bulimia nervosa patients particularly vulnerable to electrolyte imbalances such as hypokalemia and resulting acid-base disorders. These imbalances may result in QT prolongation and potentially fatal arrhythmias. Patients who abuse ipecac to induce vomiting may suffer from  permanent conduction problems and cardiomyopathy since it contains emetine, a cardiotoxic alkaloid. Stimulant abuse can lead to palpitations, sinus tachycardia, and arrhythmias such as supraventricular tachycardia. Diet pill abuse is similarly associated with heart arrhythmias.

Bulimia Nervosa Cardiovascular Complications

Hypokalemia occurs when the blood contains too little potassium. Common causes of hypokalemia are a potassium-deficient diet or purging of ingested food. Urine potassium-to-creatinine ratios of <13 are often indicative that hypokalemia is resultant from eating disorder behaviors. If serum potassium levels are 2.5 mmol/L or more and no symptoms of hypokalemia are present, it can be treated with oral potassium supplements and purging cessation in bulimia nervosa patients. However, if serum potassium levels are <2.5mmol/L, potassium supplementation must be provided both orally and intravenously in a saline solution drip at no greater than 50-75mL/hr to restore intravascular volume while preventing hyperkalemia. Severe hypokalemia can lead to QT prolongation, TdP, other arrhythmias, and rarely, acute renal failure via hypokalemic nephropathy. 

Hypokalemia in Eating Disorder Patients

Ambhore, A., Teo, S. G., Omar, A. R. B., & Poh, K. K. (2014). ECG series: Importance of QT interval in clinical practice. Singapore Medical Journal, 55(12), 607. https://doi.org/10.11622/smedj.2014172

ECG Series: Importance of QT Interval in Clinical Practice

QT Corrected for Heart Rate (QTc) Interval

Aldosterone (ALD) is a hormone that regulates sodium and potassium levels, contributing to blood pressure regulation. It increases sodium levels, thereby also increasing blood volume via water retention, and increases the amount of potassium excreted in urine. Among adults, generally 3.1 – 35.4 ng/dL is considered normal.

Aldosterone (ALD)

Refeeding syndrome refers to the metabolic complications that occur when starting the refeeding process. Risk factors include very low body weight, severe malnutrition and rapid weight loss.

Refeeding Syndrome

An arrhythmia refers to an irregularity in the heartbeat, either due to excessive slowness, excessive quickness, or disorganized beating. Though sometimes harmless and natural, they may also cause issues or even be fatal. Symptoms may include chest palpitations, heart rate changes, chest pain, difficult or discomfort while breathing, anxiety, sweating, fatigue, and unconsciousness.

Learn Before

Related

Learn After