Electrolyte, hepatic and thromboembolic complications of heart failure
THE CONTEXT
Heart failure can cause electrolyte disturbances, impaired liver function, thromboembolism and arrhythmias. Several complications are compounded by treatment or low cardiac output.
Potassium disturbances
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Hypokalaemia may result from potassium-losing diuretics or hyperaldosteronism. Hyperaldosteronism can reflect renin–angiotensin system activation and impaired aldosterone metabolism from hepatic congestion.
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Most body potassium is intracellular, so substantial potassium depletion can exist despite a plasma concentration within the reference range.
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Hyperkalaemia may result from drugs promoting renal potassium resorption, particularly combinations of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and mineralocorticoid receptor antagonists.
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Renal dysfunction from low cardiac output or atherosclerotic renal vascular disease amplifies these hyperkalaemic effects.
Hyponatraemia and liver dysfunction
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Hyponatraemia is a feature of severe heart failure and carries a poor prognosis.
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Causes include diuretic therapy, inappropriate water retention from high vasopressin secretion, and failure of the cell membrane ion pump because of intracellular energy depletion.
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Hepatic venous congestion and poor arterial perfusion impair liver function, frequently producing mild jaundice and abnormal liver function tests.
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Reduced clotting-factor synthesis can make anticoagulant control difficult.
Thromboembolism
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Low cardiac output and enforced immobility predispose to deep vein thrombosis and pulmonary embolism.
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Systemic embolism, including stroke, occurs with atrial fibrillation or flutter, or intracardiac thrombus complicating mitral stenosis, myocardial infarction or left ventricular aneurysm.
Arrhythmias and sudden death
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Atrial and ventricular arrhythmias are common and may relate to hypokalaemia, hypomagnesaemia, myocardial fibrosis and sympathetic activation.
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Atrial fibrillation occurs in approximately 20% of patients with heart failure and further impairs cardiac function.
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Ventricular ectopic beats and non-sustained ventricular tachycardia are common and associated with an adverse prognosis.
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Sudden death occurs in up to 50% of patients with heart failure and is most often due to ventricular fibrillation.