Can cardiac disorders cause hyponatremia (low sodium levels)?

From the Guidelines

Yes, cardiac disorders can cause hyponatremia, which is a low sodium level in the blood (typically below 135 mEq/L).

Causes of Hyponatremia in Cardiac Disorders

Heart failure is the most common cardiac condition associated with hyponatremia, as it activates compensatory mechanisms that lead to sodium and water imbalance.

• In heart failure, decreased cardiac output triggers the activation of the renin-angiotensin-aldosterone system and stimulates the release of antidiuretic hormone (ADH) 1.
• These hormonal changes promote water retention disproportionate to sodium retention, resulting in dilutional hyponatremia.
• Additionally, many medications used to treat heart conditions, particularly diuretics like thiazides and loop diuretics, can contribute to hyponatremia by increasing sodium excretion.

Treatment of Hyponatremia in Cardiac Disorders

Treatment typically involves addressing the underlying cardiac condition, fluid restriction (usually 1-1.5 liters daily), adjusting diuretic therapy, and in severe cases, administration of hypertonic saline or vasopressin receptor antagonists (vaptans) under careful medical supervision 1.

• The severity of hyponatremia often correlates with the severity of heart failure and serves as a negative prognostic indicator.
• Patients with HF should be monitored carefully for changes in serum potassium, and every effort should be made to prevent the occurrence of either hypokalemia or hyperkalemia, both of which may adversely affect cardiac excitability and conduction and may lead to sudden death 1.
• Close observation and follow-up are crucial in managing patients with heart failure and hyponatremia, as nonadherence with diet and medications can rapidly and profoundly affect the clinical status of patients 1.

From the FDA Drug Label

Hyponatremia was attributed to cirrhosis in 17% of patients, heart failure in 68% and SIADH/other in 16%

Cardiac disorders can cause hyponatremia, as evidenced by the fact that 68% of patients with hyponatremia in the clinical trials had heart failure as the attributed cause. 2

From the Research

Cardiac Disorders and Hyponatremia

• Cardiac disorders, such as congestive heart failure (CHF), can cause hyponatremia, a condition characterized by low sodium levels in the blood 3, 4, 5.
• Hyponatremia in CHF is associated with increased morbidity and mortality, and its management is crucial to improve patient outcomes 3, 6.
• The pathogenesis of hyponatremia in heart failure is multifactorial, involving the persistent release of arginine vasopressin (AVP) and ineffective renal perfusion secondary to low cardiac output 4, 5.

Mechanisms and Types of Hyponatremia

• Hyponatremia can be caused by excess water retention (dilutional hyponatremia) or absolute deficiency of water (depletional hyponatremia) 5.
• Dilutional hyponatremia is the most common form of hyponatremia and is caused by increased activity of AVP, which increases free-water reabsorption in the renal collecting ducts 5.
• Depletional hyponatremia is usually hypovolemic, with an absolute deficiency of water but a relative excess of body water compared with sodium concentration 5.

Treatment Options

• Current treatment options for hyponatremia in CHF include hypertonic saline solution, loop diuretics, fluid restriction, and other pharmacologic agents, such as demeclocycline, lithium carbonate, and urea 3.
• Vasopressin receptor antagonists, such as tolvaptan, conivaptan, and lixivaptan, are emerging therapeutic strategies for the management of hyponatremia in heart failure 3, 4, 6, 7.
• Loop diuretics can be considered a readily available first-line pharmacologic therapy for hyponatremia in heart failure, provided that patients can be closely monitored 7.