Hyponatraemia in heart failure

1. HYPONATREMIA
IN
CONGESTIVE CARDIAC
FAILURE
Dr. Thant Zaw Lwin
M.B.B.S, M.Med.Sc (Internal Medicine)
MRCP UK, Dr. Med.Sc (Cardiology)
Consultant Cardiologist
University of Medicine 2, Myanmar

2. Introduction
Hyponatremia is defined as serum sodium <135 meq/l.
Plasma osm : should be <285 mOsm/L (else pseudo-
hyponatraemia)
It may be present in up to 30% of patients admitted to hospital
with HF.
Rodriguez M. et el, Hyponatremia in heart failure: pathogenesis and
management. Curr Cardiol Rev 2019;15:252-261.

3. Congestion in heart failure
Definition and mechanisms of congestion
• Congestion in heart failure is defined as signs and symptoms of extracellular fluid
accumulation that result in increased cardiac filling pressures.
• Filling pressures are the integrated result of the cardiac systolic and diastolic
function, plasma volume, and venous capacitance/compliance.

4. increased neurohumoral activation
increased sympathetic output
• Heart failure with increased neurohumoral activation induces a state of increased
renal sodium and water avidity resulting in an increased plasma volume.
• Also, increased sympathetic output leads to splanchnic arterial and venous
constriction resulting in blood redistribution from the splanchnic capacitance
vasculature to the circulatory volume.
• This increases the effective circulating volume by redistribution, in a state where
volume expansion is already present. As a result, venous return and cardiac filling
pressures increase.

5. Classification of hyponatremia
Hypervolemic hyponatremia
Euvolemic hyponatremia
Hypovolemic hyponatremia

6. Hypervolemic hyponatremia
ØDilutional form of hyponatremia, occurs when there is an increase in total
body water but a relatively smaller increase in the total serum sodium.
ØDilution: impaired free water excretion. Clinical picture of volume overload with
inappropriate high Uosm (≥ 100 mOsm/L). Typical in the setting of ADHF
Ø3 primary causes of hypervolemic hyponatremia:
ØHF,
ØCirrhosis of the liver, and
ØRenal disease.
ØClinical signs
Øevidence of volume expansion, such as the presence of clinically evident edema,
ascites, and pulmonary edema

7. Euvolemic hyponatremia
ØIt occurs when there is an increase in total body water without a
corresponding increase in total serum sodium, though the increase in
body water is not sufficient to promote clinically evident edema.
ØCauses:
ØSyndrome of inappropriate antidiuretic hormone (SIADH)
ØPatients with euvolemic hyponatremia have no signs of volume
depletion or volume expansion.

8. Hypovolemic hyponatremia
ØDepletional form of hyponatremia, occurs when there is a decrease in both total
body water and total serum sodium, with a disproportionately greater decrease in
serum sodium.
ØDepletion: true body deficit of Na+. Typical in the setting of chronic excessive
diuretic use (and strict Na+ intake). Clinical picture of volume depletion with low
Uosm (<100mOsm/L) and UNa (<50mEq/L)
ØHypovolemic hyponatremia is usually due to an excess of fluid loss. It is
commonly caused by fluid loss through vomiting or diarrhea or is due to the use of
diuretic therapy.
ØClinical signs of volume depletion include orthostatic decreases in blood pressure,
increases in pulse rate, dry mucus membranes, and decreased skin turgor

9. Pathophysiology of
Hyponatremia in Heart Failure

10. In heart failure with congestion, as extracellular volume
expansion is mainly driven by sodium retention.
However, in more advanced stages of heart failure,
inappropriately high levels of arginine vasopressin contribute
to plasma expansion and dilutional hyponatremia.

11. • HF patients may have increased vasopressin secretion
• in response to decreases in arterial blood pressure and circulating blood
volume.
• A decrease in blood volume or blood pressure of approximately 8% to 10% -
stimulates vasopressin secretion.
• The underloading of arterial baroreceptors is responsible for the stimulation of
vasopressin secretion.
• Vasopressin increases the passive reabsorption of electrolyte-free water in the
kidney in an attempt to restore perfusion pressure, may result in hypervolemic
hyponatremia.
Inappropriately high levels of arginine vasopressin in
advanced decompensated heart failure

12. Derived from Mann, Braunwald's Heart Disease: A
Textbook of Cardiovascular Medicine, 2012.

13. Vasopressin
• Is a nine-amino-acid peptide synthesized in the
neurosecretory cells of the supraoptic and
paraventricular nuclei of the hypothalamus and
is stored in the posterior pituitary gland.
• Upon its release, vasopressin binds to and
activates V2-receptors in the renal collecting
duct, leading to the insertion of water channels
into the wall of the collecting duct by a cAMP-
dependent mechanism.
• This series of events stimulates water
reabsorption.
• Thus, increased vasopressin promotes an
increase in electrolyte-free water reabsorption
and more concentrated urine as water passively
diffuses out of the renal tubule.
MOA Of V2 Receptor Activation

14. • Circulating vasopressin can also cause vasoconstriction by activating V1a-
receptors on smooth muscle cells in blood vessels. V1b-receptors are found on
corticotropes, and they contribute to increased ACTH secretion.
• The primary role of vasopressin is
• to control total body water, electrolyte balance, and blood pressure by
regulating vascular tone and water excretion by the kidney.

15. Why recognizing and treating
hyponatremia is important ?

16. Prevalence Of Hyponatremia In Patients
Hospitalised With HF

20. OPTIMIZE-HF
• The Organized Program to Initiate Life Saving Treatment in Patients
Hospitalized for Heart Failure (OPTIMIZE-HF) registry recorded that
25.3% of 47,647 heart failure patients had hyponatremia on
admission.
• In this registry, patients with hyponatremia had increased in-hospital
and post-discharge mortality and longer median hospital stay
compared with those with higher sodium levels.

21. Hyponatremia Is Associated with
Higher Mortality
Lancet. 1982;2(8289):101-2.
Clin Sci. 1939;4:73-7.
Br Med J. 1983;286(6366):671-3.
Br Med J. 1979;1(6173):1242-6.

22. Mx of Hyponatremia - HF
Dilution: temporarily stop distal acting diuretics, limit water intake,
promote distal nephron flow (loop diuretics, hypertonic saline,
acetazolamide/SGLT2 inhibitor) or vaptans, correction of K+ and
Mg2+ deficiencies
Depletion: stop distal acting diuretics, calculate Na deficit and
administer IV Na+ correction of K+ and Mg2+ deficiencies

23. Rationale of Present Therapies
Increase the amount of sodium in the body
Decrease intake of water
Prevent water reabsorption into the body and prevent dilution

24. Fluid restriction is the most common treatment
in hyponatremia

25. Fluid restrictions to less than 800–1000 mL/day may be indicated
to achieve a negative water balance and treat hyponatraemia
fluid restriction usually cannot be sustained because it produces
intolerable dehydration and thirst
Secondly, fluid restriction works very slowly—generally 1 to 2 mEq/L
per day even under a severe fluid restriction of <500 mL/d.
Consequently, this method can take many days to correct a low
serum [Na+].
Fluid restriction

26. Treatments for Hyponatremia
Therapy Limitations
Isotonic saline Ineffective in dilutional hyponatremias; can’t be used
in edema-forming disorders; no controlled safety database
Hypertonic saline No consensus re appropriate infusion rates; overcorrection
can cause osmotic demyelination; can’t be used in edema-
forming disorders; no controlled safety database
Fluid restriction Slow to correct over many days; poorly tolerated due to
thirst; unsuccessful with high AVP levels and urine
osmolalities
Demeclocycline Not FDA approved for hyponatremia; slow to correct;
nephrotoxic in cirrhosis and CHF
All treatments other than demeclocycline
and the vaptans fail to attack the mechanistic
cause of dilutional hyponatremia, which is
inappropriately elevated plasma AVP levels.

27. Aquaretic Therapies
• The appropriate method of treating hyponatremia in HF is by
removing excess total body water
• That is the objective of fluid restriction that decreases body water via
insensible losses of water, but very inefficiently and very slowly.
• A better therapy would be blocking the process of urinary
concentration, which originates from AVP binding to the V2 receptor
in the kidney, and would prevent all the downstream intracellular
consequences of V2 receptor activation including the insertion of the
aquaporin water channels into the apical membrane of the collecting
duct cells.

28. • Was approved by US FDA in February 19, 2009
• Tolvaptan (INN) is a selective, Competitive vasopressin
receptor 2 antagonist used to treat hyponatremia associated
with congestive heart failure, cirrhosis, and the syndrome of
inappropriate antidiuretic hormone (SIADH)
Tolvaptan

29. Mechanism of action of the Tolvaptan
• Stimulate increased water excretion from the kidney.
• Importantly, blocking the V2 receptor has no effect on sodium or
potassium excretion; it simply causes increased excretion of water
without increased solute.
• Therefore, vaptans are electrolyte-sparing, and it is more appropriate
to call their effect “aquaresis” or increased urinary water excretion
rather than diuresis, which classically has been defined as increased
urinary water and solute (particularly sodium and potassium)
excretion.

30. • Tolvaptan is a selective vasopressin V2-receptor antagonist with an
affinity for the human V2-receptor 1.8 times that of native
vasopressin.
• Tolvaptan affinity for the V2-receptors is approximately 29 times that
for the V1a-receptor.
• When taken orally, 15- to 60-mg doses of tolvaptan antagonize the
effect of vasopressin and cause an increase in urine water excretion
that results in an increase in free water clearance (aquaresis), a
decrease in urine osmolality, and a resulting increase in serum sodium.
• Urinary excretion of sodium and potassium, and plasma potassium
concentrations are not significantly changed.

31. Mechanisms of action of diuretics in heart failure

32. Binding of a V2-receptor antagonist, such as tolvaptan, blocks the activation of the
receptor by endogenous vasopressin.
The resulting increase in urine output produced by a V2-receptor antagonist is
quantitatively similar to diuretics such as loop diuretics, but qualitatively different
in that electrolyte-free water is excreted without a significant increase in urine
solute excretion, including sodium and potassium.
For this reason, the renal effects produced by V2-receptor antagonists are termed
aquaresis, to distinguish them from the renal effects produced by some diuretic
agents, which include not only increased water excretion but also natriuresis and
kaliuresis
Targeted MOA: Vasopressin V2-receptor antagonism

33. 1. SAMSCA blocks vasopressin selectively blocks
the binding of vasopressin to the V2-receptors in the
renal collecting ducts
Targeted MOA: Vasopressin V2-receptor antagonism

34. 2. Decreased expression of aquaporin Inhibition
of vasopressin binding to the V2-receptor leads to
decreased expression and removal of aquaporin-2
from the luminal membrane.
3. Decreased water reabsorptionV2-
receptor blockade results in decreased
water reabsorption by the kidney.
Increases free water clearance

35. Onset of aquaretic effect
4. Diuresis vs aquaresis
Diuresis and aquaresis are different.
Diuresis is an increase in overall urine
production. SAMSCA provides aquaresis,
or excretion water without clinically
significant electrolyte loss
5. Serum sodium concentration
and urine osmolalityAquaresis
results in increased serum sodium
concentration and decreased urine
osmolality.

36. 6. Sodium and potassium excretionThis process does not, however, result
in significant change in urinary excretion of sodium or potassium, nor does it
result in increased plasma potassium.

37. Dosing
• The usual starting dose for (tolvaptan) is 15 mg administered once
daily without regard to meals.
• The dose of Tolvaptan may be increased to 30 mg once daily, after at
least 24 hours, to a maximum of 60 mg once daily, as needed to
achieve the desired level of serum sodium.
• During initiation and titration, frequently monitor for changes in
serum electrolytes and volume to prevent overcorrection of serum
sodium

38. Tolvaptan is contraindicated in the
following conditions:
Urgent need to raise serum sodium acutely
Inability of the patient to sense or appropriately respond to thirst
Hypovolemic hyponatremia
Concomitant use of strong CYP 3A inhibitors
Anuric patients

39. Adverse effects
• Problems with speech or muscle control, trouble swallowing, trouble
moving your arms and legs, mood changes, and seizure (convulsions)
– may be osmotic demyelination syndrome due to rapid correction
of sodium
• weakness or fainting;
Less serious side effects may include:
• dry mouth;
• increased thirst
• abnormal frequent urination

41. 13.7 Electrolyte disorders: Hyponatremia
Tolvaptan, an orally active selective arginine vasopressin V2 receptor
antagonist, can be considered to increase serum sodium and diuresis in
patients with persistent hyponatraemia and congestion.
However, no effects on outcomes have been shown in RCTs.
European Heart Journal (2021) 42, 3670

42. Conclusion
Hyponatremia occurring in advanced HF has been considered for
many years as a poor prognostic factor in HF.
Tolvaptan may be useful as a decongestive aquaretic, but improving
hyponatremia may also improve the short-term prognosis for
morbidity and mortality in these patients

43. Thank You