Thiamine deficiency cardiomyopathy

Article written and reviewed by Dr Luca Moretti

Thiamine, or vitamin B1, deficiency can cause a potentially reversible cardiovascular syndrome called cardiac beriberi or wet beriberi. It is not always a dilated cardiomyopathy in the strict morphological sense: the early phase may be dominated by peripheral vasodilation, high output and salt and water retention, whereas advanced disease may present with biventricular depression. The metabolic phenotype must be recognized because etiologic therapy can change hemodynamics within hours.

The fulminant variant, called Shoshin beriberi, combines severe lactic acidosis, hypotension and cardiocirculatory collapse. Although the classic pattern is high output, low output may appear in the terminal phase because of myocardial exhaustion, making the diagnosis less intuitive. Thiamine-deficiency shock is rapidly fatal if untreated but may respond dramatically to parenteral administration.

In high-income countries, thiamine deficiency has not disappeared: alcohol use disorder, malnutrition, prolonged vomiting, bariatric surgery, malabsorption, dialysis and critical illness create new settings. An apparently calorie-sufficient diet does not guarantee adequate micronutrient intake. Nutritional risk depends on diet quality and absorption, not only on body weight.

Cardiac beriberi may coexist with Wernicke encephalopathy or neuropathy, but absence of the neurologic triad does not exclude it. Confusion, ocular signs and ataxia are often incomplete, while edema and shock may dominate the presentation. The multisystem presentation requires the heart, neurologic status and nutrition to be assessed together.

Laboratory diagnosis is imperfect, whereas treatment is safe, inexpensive and time-dependent. In a compatible patient, a sample is obtained before therapy if doing so causes no delay, and thiamine is given without waiting for the result. Urgent empiric treatment does not replace clinical reasoning but recognizes the asymmetry between the harm of delay and the low risk of the vitamin.

Thiamine metabolism and cardiocirculatory pathophysiology

Thiamine is absorbed in the small intestine through saturable transporters and, at high concentrations, by passive diffusion. In the body it is phosphorylated mainly to thiamine diphosphate, also called thiamine pyrophosphate, the predominant coenzyme form. Limited stores and continuous turnover explain why inadequate intake combined with high metabolic consumption can produce disease within weeks.

Thiamine diphosphate is a cofactor for pyruvate dehydrogenase, which connects glycolysis to the Krebs cycle, and for alpha-ketoglutarate dehydrogenase within the cycle itself. It also participates in branched-chain alpha-ketoacid dehydrogenase and transketolase in the pentose phosphate pathway. This coenzyme hub makes deficiency particularly harmful to tissues with high energy requirements such as the heart and brain.

When pyruvate dehydrogenase is limited, pyruvate is diverted toward lactate and aerobic ATP production decreases. The heart loses efficiency while lactate rises despite potentially adequate oxygenation. Metabolic-block acidosis may therefore resemble sepsis or refractory shock and persist until the missing cofactor is corrected.

Reduced transketolase activity impairs the pentose phosphate pathway and the ability to support redox defenses. Oxidative stress, mitochondrial dysfunction and energy deficiency affect cardiomyocytes and the nervous system. Cellular injury is not explained by a simple caloric deficit, but by an inability to use available carbohydrates correctly.

Peripheral vasodilation lowers systemic vascular resistance; the heart responds by increasing heart rate and output, while renin-angiotensin and sympathetic activation promote sodium and water retention. The result is a wide pulse pressure, warm extremities, edema and congestion. The hyperdynamic circulation may conceal severity because initial blood pressure is maintained despite profoundly impaired metabolism.

With progression, volume overload, acidosis and energy deficiency depress contractility, involving both ventricles. Filling pressures and pulmonary vascular resistance may rise, while output falls in Shoshin beriberi. The hemodynamic transition explains why an exclusively high-output description does not encompass all fulminant cases.

Magnesium is required for formation and function of active thiamine forms and for numerous ATP-dependent reactions. Concomitant deficiency, common in malnutrition and alcohol use, may blunt the response and promote arrhythmias. Magnesium dependence makes it necessary to measure and correct magnesium rather than wait for thiamine alone to appear ineffective.

A glucose load or refeeding increases carbohydrate flux through thiamine-dependent enzymes and may precipitate lactate accumulation or encephalopathy in a depleted patient. Thiamine is therefore given before or together with carbohydrates. This nutritional sequence must not, however, delay life-saving correction of hypoglycemia, which proceeds concurrently.

Causes, at-risk populations and clinical presentations

Insufficient intake results from dietary restriction, poverty, eating disorders, addiction, monotonous diets or inability to eat. Refined foods and prolonged cooking may reduce thiamine content, while some traditional diets expose people to thiaminases or antagonists. The dietary history should describe what is actually consumed rather than merely whether meals are eaten.

Alcohol reduces intake, absorption, storage and utilization and is associated with multiple deficiencies. Direct ethanol-related myocardial injury may coexist with beriberi, producing a combination of chronic cardiomyopathy and an acute metabolic component. Alcohol-related overlap is recognized through nutritional status, hemodynamics and the rapid response to thiamine, without assuming a single cause.

Prolonged vomiting due to hyperemesis gravidarum, malignancy, obstruction or other causes depletes intake and increases losses. After bariatric surgery, vomiting, poor adherence to supplements and malabsorption may cause deficiency even years later. Gastrointestinal risk requires prophylaxis and treatment before neurologic or cardiac signs appear.

Parenteral or enteral nutrition without adequate supplementation, refeeding and critical illness rapidly increase requirements. Sepsis and hypermetabolism complicate lactate interpretation but do not exclude concomitant deficiency. Iatrogenic deficiency is preventable through nutrition protocols and review of the administered formulation.

Dialysis may increase loss of water-soluble vitamins, while malignancy, chronic infections and advanced heart failure reduce intake and stores. Loop diuretic use has been associated with greater urinary loss and variable prevalence of deficiency, but causality and the benefit of universal supplementation remain uncertain. Diuretic-associated risk should be interpreted together with nutrition, dose, comorbidity and laboratory method.

Classic wet beriberi presents with tachycardia, warm extremities, wide pulse pressure, edema and signs of right-sided or biventricular heart failure. High cardiac output and low vascular resistance distinguish it from many low-output cardiomyopathies. The hyperdynamic profile can be confirmed invasively when the presentation is critical and hemodynamics remain unclear.

In Shoshin beriberi, nausea, dyspnea, hypotension, renal failure and very high lactate may evolve over hours. Echocardiography ranges from relatively preserved function to severe biventricular hypokinesia, and vascular resistance is not always low in the terminal phase. Shock heterogeneity prevents beriberi from being excluded merely because one classic finding is absent.

Symmetric neuropathy, weakness, loss of reflexes and pain characterize dry beriberi, whereas Wernicke encephalopathy includes altered mental status, ocular signs and ataxia. The syndromes overlap and the complete triad has low sensitivity. Neurologic signs strengthen suspicion, but their absence does not protect against cardiac involvement.

Infants of thiamine-deficient mothers may develop heart failure, aphonia, cyanosis and acidosis with rapid progression; maternal health may appear relatively preserved. This setting is relevant in populations with low intake or monotonous diets. Infantile beriberi highlights that epidemiology depends on maternal nutrition and public health, not only on individual disease.

Diagnosis: laboratory testing, hemodynamics and therapeutic response

Diagnosis begins by integrating risk factors, heart failure or shock, otherwise unexplained lactate elevation and possible neurologic signs. No single feature is specific, but their constellation increases probability before laboratory confirmation. Probabilistic reasoning is essential because waiting for definitive proof may exceed the therapeutic window.

Thiamine diphosphate measured in whole blood by chromatography better reflects cellular compartments than plasma thiamine, which is influenced by recent intake. Reference intervals, sample stability and methods vary between laboratories. Blood measurement can support the diagnosis but has no universal threshold capable of excluding every functional deficiency.

Erythrocyte transketolase activity and its increase after addition of thiamine pyrophosphate are a historical functional measure available only in selected centers. Hematologic disease and preanalytical factors may affect the result. The functional test provides information on biological effect but is not rapid enough to guide an emergency.

The sample is ideally obtained before the first dose because supplementation may rapidly normalize values, but sampling must not delay treatment. A normal concentration obtained after treatment does not exclude initial deficiency. Preanalytical timing should be documented so that a test already altered by therapy is not misinterpreted as negative.

Blood gas analysis shows lactic acidosis of variable severity; renal and liver function, complete blood count, albumin, phosphorus, potassium and magnesium define deficiencies and complications. Sepsis, ischemia, drugs and liver failure remain alternative causes of lactate elevation. The lactate differential diagnosis proceeds in parallel, without using response to thiamine as a reason to neglect other emergencies.

ECG and chest radiography are nonspecific. Echocardiography assesses output, biventricular function, pressures, valves and effusion; a nondilated heart does not exclude an acute form. Hemodynamic imaging distinguishes congestion, tamponade, embolism and other causes while providing a baseline for assessing response.

Right heart catheterization is unnecessary in most cases, but in refractory shock it may demonstrate high output and low resistance or document transition to low output. These data guide vasopressors, fluids and support while avoiding physiologically opposing interventions. Invasive hemodynamics is a selective tool when clinical examination cannot resolve a rapidly changing situation.

A rapid fall in lactate, rise in blood pressure, diuresis and improvement in function after thiamine strongly support the diagnosis. The response is not perfectly specific and may reflect simultaneous interventions, but in Shoshin beriberi it is often striking. The therapeutic response integrates exposure and testing as retrospective clinical evidence.

The differential diagnosis includes sepsis, ischemic cardiogenic shock, myocarditis, pulmonary embolism, thyrotoxicosis, arteriovenous fistulas, severe anemia and mitochondrial toxicities. Several conditions may coexist in malnutrition and intensive care. A nonexclusive diagnosis allows thiamine to be administered while concurrent causes continue to be sought and treated.

Urgent treatment and management of complications

When severe cardiac beriberi is suspected, intravenous thiamine is administered immediately, preferably after obtaining a sample that does not delay care. Published regimens vary according to severity, clinical setting and possible Wernicke encephalopathy and use parenteral doses far above nutritional requirements. The therapeutic dose follows local protocols and specialist expertise, with repeated initial dosing in neurologic or critical presentations.

The parenteral route is preferred in shock, vomiting, malabsorption or suspected encephalopathy because oral absorption may be unreliable and saturable. After stabilization, treatment is changed to oral administration to complete repletion and prevent recurrence. The parenteral-to-oral sequence separates immediate rescue from restoration of body stores.

Thiamine is given before or at the same time as glucose, feeding or caloric solutions. In hypoglycemia, glucose correction is not delayed while waiting for the vitamin: both treatments are started as soon as possible. Metabolic priority avoids both worsening of deficiency and the immediate neurologic harm of hypoglycemia.

Magnesium is measured and replaced when low or plausibly deficient, with renal function monitored. Phosphorus and potassium require surveillance especially during refeeding, when rapid intracellular shifts may cause arrhythmias and weakness. Correction of cofactors makes thiamine effective and prevents a second metabolic deterioration.

Congestion may require diuretics, but vasodilation and hypotension make it dangerous to mechanically apply the chronic heart failure regimen. Vasopressors, inotropes and fluids are titrated to hemodynamics while thiamine takes effect. Temporary support maintains perfusion without replacing etiologic therapy.

In the hyperdynamic phase, excess fluid worsens edema and right-sided failure, whereas in the vasoplegic phase some fluid may be necessary; serial examination is decisive. Lactate and blood pressure may change rapidly after the vitamin. Dynamic management requires frequent reassessment rather than a fixed volume plan established at admission.

Clinical improvement may precede complete normalization of echocardiographic and neurologic findings. Lack of an initial response requires checking magnesium, dose, route and alternative diagnoses without prematurely stopping treatment when suspicion remains high. Response assessment uses hemodynamics, lactate, urine output, consciousness and cardiac function.

Anaphylaxis to parenteral thiamine is rare but possible, so it is administered in a setting equipped to treat acute reactions. This risk does not justify delay in compatible shock. Administration safety derives from appropriate monitoring, not from underdosing a metabolic emergency.

Prevention, follow-up and limits of supplementation

After stabilization, the reason for deficiency is identified: food access, alcohol use disorder, vomiting, malabsorption, surgery, dialysis or a nutrition error require different interventions. Without correction of the cause, stores may again become depleted. Recurrence prevention is nutritional, medical and social at the same time.

Patients after bariatric surgery or with persistent vomiting should be instructed that new symptoms warrant urgent evaluation, not merely an increase in oral supplements. Nutritional follow-up verifies adherence and other deficiencies. Bariatric surveillance recognizes that an unabsorbed tablet is not effective prophylaxis.

In alcohol use disorder, thiamine is integrated into a pathway addressing withdrawal, nutrition and addiction. The vitamin prevents or treats deficiency but does not protect against direct ethanol toxicity or its complications. Integrated alcohol-related care avoids reducing a complex disease to a vitamin prescription.

During refeeding of a high-risk person, thiamine precedes caloric intake and electrolytes are monitored according to protocols. Caloric intake is increased gradually according to the severity of malnutrition. Refeeding prophylaxis prevents both thiamine deficiency and shifts in phosphorus, potassium and magnesium.

Chronic heart failure and loop diuretics are associated with low thiamine in some studies, but prevalence depends on method and population. Small trials have produced conflicting results and a more recent meta-analysis did not demonstrate clinical benefit from routine supplementation. The therapeutic distinction separates life-saving treatment of beriberi from indiscriminate vitamin prescribing to every patient with heart failure.

When deficiency is confirmed, treatment duration depends on persistence of the cause and restoration of adequate nutrition. Imaging and lactate document cardiac recovery; neurologic and nutritional examinations assess slower outcomes. Multisystem follow-up prevents normalization of ejection fraction from obscuring residual neuropathy or Wernicke encephalopathy.

Population prevention includes food fortification and ensuring adequate intake in humanitarian emergencies, in which populations dependent on refined grains may develop outbreaks. Surveillance of infants and mothers is essential in at-risk areas. Public health shows that beriberi is not only a rare intensive-care diagnosis but a preventable disease of food security.

Cardiac beriberi teaches clinicians to recognize a treatable cause within apparently nonspecific shock. The combination of nutritional risk, elevated lactate, a hyperdynamic circulation or biventricular dysfunction should trigger therapy without waiting for diagnostic perfection. Time-dependent reversibility makes thiamine an immediate intervention followed by rigorous reconstruction of the cause and durable prevention.

Diagnostic settings at high risk of delay

After bariatric surgery, vomiting and neurologic symptoms require parenteral thiamine even if the patient reports taking a multivitamin. Type of procedure, adherence and ability to retain the supplement determine actual exposure. An unabsorbed supplement does not reduce urgency, and a laboratory level must not delay treatment.

In hyperemesis gravidarum, intravenous glucose and nutrition may precipitate manifestations in a woman who has been vomiting for weeks. The heart and brain may be involved together, and pregnancy changes the differential diagnosis of dyspnea and tachycardia. Prophylaxis in hyperemesis should precede refeeding and accompany control of vomiting.

In a dialysis patient, fatigue, hypotension and congestion have many explanations and deficiency may be obscured by the underlying disease. A restrictive diet and dialysis losses increase plausibility, but supplementation follows nutritional assessment and protocol. The dialysis context requires avoiding both omission and automatic attribution of nonspecific symptoms.

In intensive care, refractory lactate elevation is often attributed to sepsis, catecholamines or hypoperfusion, all genuine causes that can coexist. Prolonged nutrition, diuresis and hypermetabolism may add deficiency. Concomitant deficiency is treated without interrupting antibiotics, source control or shock support.

Refeeding after fasting shifts phosphorus, potassium and magnesium into cells and increases thiamine requirements. Heart failure, arrhythmias and weakness may result from the combination rather than a single abnormality. Refeeding syndrome requires coordinated prevention and controlled caloric advancement.

In alcohol use disorder, a standard multivitamin infusion may contain an insufficient dose for suspected Wernicke encephalopathy or a critical presentation. Dose and frequency are prescribed explicitly according to protocol rather than relying on the nominal composition of the intravenous bag. Prescribed thiamine should be distinguishable from generic supplementation.

An obese patient may be severely deficient after restriction, malabsorption or vomiting, while albumin and weight do not measure thiamine stores. Nutritional appearance may therefore be falsely reassuring. Micronutrient malnutrition is assessed from the history and metabolic risk, not from body mass index alone.

A very rapid response to the vitamin is suggestive, but a slower response does not exclude the diagnosis when pneumonia, alcoholic cardiomyopathy or multiple deficiencies coexist. Conversely, a fall in lactate after simultaneous interventions does not by itself prove beriberi. Interpretation of the response preserves the chronology and considers competing causes.

At discharge, formulation, dose and duration of oral therapy are linked to a dietary plan and correction of the underlying mechanism. An appointment without food access, treatment of vomiting or addiction support does not prevent recurrence. Nutritional continuity turns metabolic rescue into sustainable protection.

The possibility of rapid recovery makes deficiency easy to treat only after it has been recognized. Before treatment, the presentation mimics far more common emergencies and the test result may arrive late. Early diagnosis therefore depends on clinical awareness of risk and the decision to treat a plausible probability while evaluation continues.