Disconnect Between Heart, Kidneys Negatively Affects Heart Failure Outcomes

Hyponatremia resulting in cardiac dysfunction and intrarenal venous congestion may lead to worsened survival outcomes among patients with heart failure, according to new study findings published in Disease Markers.

“The interrelationship between the heart and kidneys has a great importance in the homeostasis of the cardiovascular system,” the authors wrote. “But in patients with heart failure, [the sympathetic nervous system and the renin-angiotensin-aldosterone system] act in a maladaptive way, generating excessive retention of sodium and water, perpetuating systemic congestion.”

This cross-sectional study of 88 patients—44 patients with heart failure (mean [SD] age, 63.52 [7.03] years) matched 1:1, based on age and gender, to healthy controls (mean [SD] age, 60.38 [7.46] years)—evaluated serum sodium, NT-proBNP, and creatinine levels, as well as estimated glomerular filtration rate (eGFR), among the entire study population; also assessed were their intrarenal arterial resistive index, intrarenal venous flow pattern, renal venous stasis index, and left ventricular ejection fraction (LVEF). Patients in the study received care from the Department of Internal Medicine at Victor Babes University of Medicine and Pharmacy in Timișoara, Romania, from January 2018 to May 2021.

Overall, close to half (47.72%) of patients in the heart failure cohort were indicated to have hyponatremia, or suboptimal blood sodium levels. For this study, hyponatremia was defined as serum sodium below 136 mmol/L. New York Heart Association heart failure classes I to IV were evenly distributed among this cohort, with 10 having class I heart failure; 12, class II; 11, class III; and 11, class IV.

The most common cause of heart failure was ischemic heart disease in 18, followed by arterial hypertension in 17, primary dilated cardiomyopathy in 5, and rheumatic heart disease and degenerative valvular disease in 2 patients each. All of the patients in the heart failure groups also were taking diuretics. Beta-blockers, mineralocorticoid receptor antagonists, angiotensin receptor blockers, and angiotensin-converting enzyme inhibitors were used by 37, 26, 25, and 19 patients, respectively.

When the authors analyzed mean serum sodium, NT-proBNP, creatinine levels, and estimated glomerular filtration rate (eGFR), they found all measures in the heart failure cohort to be worse compared with the healthy controls:

• Serum sodium: 135.63 (3.94) vs 140.52 (2.12) mmol/L (P < .0001)
• NT-proBNP: 3929.11 (5044.27) vs 183.38 (54.34) pg/mL (P < .0001)
• Creatinine: 1.36 (0.46) vs 0.97 (0.12) mg/dL (P <.0001)
• eGFR: 52.09 (17.68) vs 68.38 (29.39) mL/min/1.73 m² (P < .001)

LVEF was also measured, and the mean results for the healthy controls were approximately 20 percentage points higher than for the study group: 59.80% (4.31%) vs 38.35% (10.22%) (P < .0001).

Among older adults, low sodium levels have potential to cause seizures or death, high creatinine levels can impair kidney function, high NT-proBNP levels may indicate unstable heart function, and low eGFR can signify loss of kidney function.

In addition, hyponatremia in heart failure, they added, has also been linked to hospital readmission, longer hospital length of stay, and higher total costs and complications. In this study, it was an independent predictor of a 72% greater chance of 12-month mortality (HR, 1.72; 95% CI, 1.12-2.65), as well as linked to higher 12-month mortality in the heart failure cohort: 17.9% vs 14.6% (P < .001).

“The kidneys have an important role in maintaining the hydroelectrolytic and acid-base balance, in the hemoglobin synthesis, and in the metabolic waste product clearance,” the authors concluded. “Cardiac dysfunction has repercussions on kidney function, which in turn contributes to the worsening of heart function.”

Reference

Caraba A, Iurciuc S, Munteanu A, Iurciuc M. Hyponatremia and renal venous congestion in heart failure patients. Dis Markers. Published online August 12, 2021. doi:10.1155/2021/6499346