Atrial natriuretic factor secretion in dogs with experimental high-output heart failure

Area of Science:

• Cardiology
• Endocrinology
• Renal Physiology

Background:

• Chronic high-output heart failure models are crucial for understanding cardiac decompensation.
• Arteriovenous (AV) fistula in dogs creates a model of sustained volume overload and cardiac stress.
• Atrial natriuretic factor (ANF) is implicated in regulating fluid and electrolyte balance.

Purpose of the Study:

• To investigate the temporal changes in plasma immunoreactive atrial natriuretic factor (iANF) in a canine model of chronic heart failure.
• To determine the relationship between iANF levels, sodium balance, and the renin-aldosterone system during the progression of heart failure.
• To elucidate the role of ANF as a compensatory mechanism in chronic cardiac volume overload.

Main Methods:

• Utilized six conscious dogs with surgically created arteriovenous (AV) fistulas to induce chronic high-output heart failure.
• Monitored plasma iANF concentrations, plasma renin activity, plasma aldosterone concentration, and right atrial pressure over a 14-day period.
• Assessed daily sodium excretion and balance to evaluate renal handling of sodium.

Main Results:

• Following AV fistula creation, dogs initially exhibited sodium retention, elevated plasma renin activity, aldosterone, and right atrial pressure, with only modest iANF increase.
• Between days 6 and 14, dogs achieved sodium balance, accompanied by a significant rise in iANF.
• This natriuretic phase correlated with normalized renin and aldosterone levels and persistently elevated right atrial pressure.

Conclusions:

• Chronic increases in atrial pressure serve as a sustained stimulus for ANF release in dogs with AV fistula-induced heart failure.
• Elevated ANF levels contribute to chronic endocrine adjustments, reestablishing sodium balance by inhibiting the renin-aldosterone axis.
• The ANF endocrine system acts as a compensatory mechanism promoting sodium and water excretion in heart failure via renin-aldosterone suppression and potential direct renal effects.