Sodium and water excretion abnormalities in congestive heart failure. Determinant factors and clinical implications

A pharmacogenetic investigation of intravenous furosemide in decompensated heart failure: a meta-analysis of three clinical trials

We conducted a meta-analysis of pharmacogenomic substudies of three randomized trials conducted in patients with decompensated heart failure (HF) that were led by National Heart Lung and Blood Institute (NHLBI)-funded HF Network to test the hypothesis that candidate genes modulate net fluid loss and weight change in patients with decompensated HF treated with a furosemide-based diuretic regimen. Although none of the genetic variants previously shown to modulate the effects of loop diuretics in healthy individuals were associated with net fluid loss after 72 h of treatment, a set of rare variants in the APOL1 gene, which codes for apolipoprotein L1 (P=0.0005 in the random effects model), was associated with this end point. Moreover, a common variant in the multidrug resistance protein-4 coding gene (ABCC4, rs17268282) was associated with weight loss with furosemide use (P=0.0001). Our results suggest that both common and rare genetic variants modulate the response to a furosemide-based diuretic regimen in patients with decompensated HF.

Baseline hyponatremia does not predict two-year mortality in patients with chronic peritoneal dialysis

PURPOSE

Hyponatremia is a common electrolyte abnormality in a variety of medical conditions. Lower predialysis serum sodium concentration is associated with an increased risk of death in oligoanuric patients on hemodialysis. However, whether hyponatremia affects the short-term mortality in chronic peritoneal dialysis (CPD) patients remains unclear.

METHODS

We conducted a cross-sectional and two-year follow-up review retrospectively, and 318 patients with CPD were enrolled in a medical center. Serum sodium levels were measured at baseline and categorized as quartile of Na: quartile 1 (124-135 mEq/L), quartile 2 (136-139), quartile 3 (140-141) and quartile 4 (142-148). Mortality and cause of death were recorded for longitudinal analyses.

RESULTS

The patients with higher quartile (higher serum sodium) had a trend of lower age, peritoneal dialysis (PD) duration, co-morbidity index, D/P Cr and white blood cell counts and higher renal Kt/Vurea (Kt/V) and serum albumin level. Stepwise multiple linear regression analysis showed that serum sodium level was positively associated with albumin, residual renal Kt/V and negatively associated with age and PD duration in CPD patients. After two-year follow-up, stepwise multivariate Cox proportional hazards model demonstrated that age, co-morbidity index and serum albumin were the significant risk factors for all-cause two-year mortality, but not serum sodium levels.

CONCLUSIONS

Serum sodium level in CPD patients is associated with nutritional status, residual renal function and duration of PD. However, baseline serum sodium level is not an independent predictor of two-year mortality in CPD patients.

Hyponatraemia predicts the acute (type 1) cardio-renal syndrome

AIMS

The acute (type 1) cardio-renal syndrome (CRS) refers to an acute worsening of heart function leading to worsening renal function (WRF), and frequently complicates acute decompensated heart failure (ADHF) and acute myocardial infarction (AMI). The aim of this study was to investigate whether hyponatraemia, a surrogate marker of congestion and haemodilution and of neurohormonal activation, could identify patients at risk for WRF.

METHODS AND RESULTS

We studied the association between hyponatraemia (sodium <136 mmol/L) and WRF (defined as an increase of >0.3 mg/dL in creatinine above baseline) in two separate cohorts: patients with ADHF (n = 525) and patients with AMI (n = 2576). Hyponatraemia on admission was present in 156 patients (19.7%) with ADHF and 461 patients (17.7%) with AMI. Hyponatraemia was more frequent in patients who subsequently developed WRF as compared with patients who did not, in both the ADHF (34.6% vs. 22.2%, P = 0.0003) and AMI (29.7% vs. 21.8%, P<0.01) cohorts. In a multivariable logistic regression model, the multivariable adjusted odds ratio for WRF was 1.90 [95% confidence interval (CI) 1.25-2.88; P = 0.003] and 1.56 (95% CI 1.13-2.16; P = 0.002) in the ADHF and AMI cohorts, respectively. The mortality risk associated with hyponatraemia was attenuated in the absence of WRF.

CONCLUSION

Hyponatraemia predicts the development of WRF in two clinical scenarios that frequently lead to the type I CRS. These data are consistent with the concept that congestion and neurohormonal activation play a pivotal role in the pathophysiology of acute cardio-renal failure.

Cardiorenal syndrome in acute decompensated heart failure

Cardiorenal syndrome (CRS) commonly occurs during treatment of acute decompensated heart failure (ADHF) and is associated with poor clinical outcome. The pathophysiology of CRS entails a complex interaction between hemodynamic alterations, including reduced renal perfusion, increased venous pressure and activation of multiple neurohormonal systems. Attempts to effectively treat congestion while preserving renal function in ADHF are often met with limited clinical success and often require therapeutic decisions that reflect a compromise between potential benefits and harm. At present, there is no evidence-based intervention specifically targeted at renal function. Recent Phase III randomized trials, using novel agents in patients with ADHF, have largely failed to demonstrate any benefits of therapy on renal and clinical outcomes. Early diagnosis of CRS using novel markers of tubular injury may allow for timely interventions and attenuate progression. Future studies are needed to further elucidate the pathophysiology of this complex syndrome and identify new potential targets for effective evidence-based treatments.

Emergence of blood urea nitrogen as a biomarker of neurohormonal activation in heart failure

The nonosmotic release of arginine vasopressin, concurrent with the activation of the sympathetic nervous system and renin-angiotensin-aldosterone system, is thought to represent the maladaptive response that is central to the pathophysiology of heart failure (HF). The degree of neurohormonal activation correlates with the severity of the disease and can predict the outcomes. However, quantification of components of neurohormonal axis (e.g., serum arginine vasopressin level) is mainly reserved for research purposes rather than routine practice. The results of several recent HF trials have shed light on the differential role of blood urea nitrogen (BUN) and creatinine in predicting the outcomes in this setting. These studies suggest that BUN could indeed represent a surrogate marker for "renal response" to neurohormonal activation in this setting, above and beyond its role in the estimation of renal function. In this report, the relevant physiologic mechanisms underlying urea and water transport in the kidney are first reviewed. Then, the activation of the neurohormonal axis and the impact of its components on renal urea transport, independent of changes in renal function, are explained. Finally, the unique role of BUN as a biomarker of neurohormonal activation in the setting of HF is discussed, and the potential clinical implication of this novel concept is emphasized. In conclusion, this review explains the pathophysiologic basis for the emerging role of BUN as a biomarker in HF.

Hyponatremia and Heart Failure?Treatment Considerations

Hyponatremia as it occurs in the heart failure patient is a multifactorial process. The presence of hyponatremia in the heart failure patient correlates with both the severity of the disease and its ultimate outcome. The therapeutic approach to the treatment of hyponatremia in heart failure has traditionally relied on attempts to improve cardiac function while at the same time limiting fluid intake. In more select circumstances, hypertonic saline, loop diuretics, and/or lithium or demeclocycline have been used. The latter two compounds act by retarding the antidiuretic effect of vasopressin but carry with their use the risk of serious renal and/or cardiovascular side effects. Alternatively, agents that selectively block the type 2 vasopressin receptor increase free water excretion without any of the adverse consequences of other therapies. Conivaptan, lixivaptan, and tolvaptan are three such aquaretic drugs. Vasopressin receptor antagonists will redefine the treatment of heart failure-related hyponatremia and may possibly evolve as adjunct therapies to loop diuretics in diuretic-resistant patients.

Cardiac and renal dysfunction in chronic heart failure: relation to neurohumoral activation and prognosis

BACKGROUND

In chronic heart failure (CHF), cardiac dysfunction is considered the major determinant of neurohumoral activation but the role of renal impairment has not been defined. We investigated the relationship between both cardiac and renal dysfunction and neurohumoral activation, and their possible influence on prognosis.

METHODS

Hemodynamics, renal function, plasma neurohormones, and long-term follow-up were evaluated in 148 CHF patients, grouped according to systolic volume index (SVI) and serum creatinine (CRE) values: SVI > 28 mL/m2 and CRE < 1.5 mg/dL (group I, n = 55), SVI < 28 mL/m2 and CRE < 1.5 mg/dL (group II, n = 37), SVI > 28 mL/m2 and CRE > 1.5 mg/dL (group III, n = 25), SVI < 28 mL/m2 and CRE > 1.5 mg/dL (group IV, n = 31).

RESULTS

Neurohormones progressively increased from Group I through IV and correlated with both cardiac and renal function. The hemodynamic pattern was similar in patients with normal or abnormal renal function, whereas neurohormones were only moderately increased in the former group and markedly increased in the latter group. Long-term survival progressively decreased from Group I through IV and was significantly poorer in patients with renal dysfunction.

CONCLUSIONS

Our study confirms that, in CHF, neurohumoral activation is strictly related to long-term survival and that many factors contribute to its development and progression; among these, cardiac and renal dysfunction seem to play a major role.

Congestive heart failure in rats is associated with increased expression and targeting of aquaporin-2 water channel in collecting duct

We tested whether severe congestive heart failure (CHF), a condition associated with excess free-water retention, is accompanied by altered regulation of the vasopressin-regulated water channel, aquaporin-2 (AQP2), in the renal collecting duct. CHF was induced by left coronary artery ligation. Compared with sham-operated animals, rats with CHF had severe heart failure with elevated left ventricular end-diastolic pressures (LVEDP): 26.9 +/- 3.4 vs. 4.1 +/- 0.3 mmHg, and reduced plasma sodium concentrations (142.2 +/- 1. 6 vs. 149.1 +/- 1.1 mEq/liter). Quantitative immunoblotting of total kidney membrane fractions revealed a significant increase in AQP2 expression in animals with CHF (267 +/- 53%, n = 12) relative to sham-operated controls (100 +/- 13%, n = 14). In contrast, immunoblotting demonstrated a lack of an increase in expression of AQP1 and AQP3 water channel expression, indicating that the effect on AQP2 was selective. Furthermore, postinfarction animals without LVEDP elevation or plasma Na reduction showed no increase in AQP2 expression (121 +/- 28% of sham levels, n = 6). Immunocytochemistry and immunoelectron microscopy demonstrated very abundant labeling of the apical plasma membrane and relatively little labeling of intracellular vesicles in collecting duct cells from rats with severe CHF, consistent with enhanced trafficking of AQP2 to the apical plasma membrane. The selective increase in AQP2 expression and enhanced plasma membrane targeting provide an explanation for the development of water retention and hyponatremia in severe CHF.

Clinical relevance and management of the major electrolyte abnormalities in congestive heart failure: hyponatremia, hypokalemia, and hypomagnesemia

Electrolyte disturbances are a common complication of CHF. CHF provides a perfect milieu for the development of these disturbances; renal dysfunction, elevation of neurohormonal substances, activation of the renin-angiotensin-aldosterone axis, and diuretic therapy represent the major contributory factors. Hyponatremia is closely aligned with an unfavorable clinical course. Hypokalemia is associated with increased ventricular dysrhythmias. Hypomagnesemia noted in advanced CHF can be accompanied by arrhythmias and refractory hypokalemia. CHF also offers the ideal milieu (diseased, ischemic, and arrhythmogenic myocardium; elevated catecholamines; and arrhythmogenic drugs) for the threatening clinical consequences (clinical deterioration, dysrhythmias, or death) of these disturbances. These consequences underscore the importance of the recognition, appreciation, and management of these electrolyte abnormalities.

Baroreflex loading maneuvers do not suppress increased plasma arginine vasopressin in patients with congestive heart failure

Nonspecific baroreflex loading maneuvers such as head-down tilt readily suppress stimulated arginine vasopressin levels in normal humans. To test the hypothesis that the increased arginine vasopressin levels in patients with congestive heart failure would not respond normally to baroreflex loading, 12 patients with congestive heart failure had arginine vasopressin levels and osmolality determined in the supine position and after 15 min of 30 degrees head-down tilt. Arginine vasopressin was increased to 6.5 +/- 2.0 pg/ml at control measurement and did not decrease. Eight patients underwent further study after osmotic stimulation with mannitol. Mannitol increased osmolality from 287 +/- 9.2 to 294 +/- 7.8 mOsm/kg (p less than 0.001) and from 288 +/- 9 to 299 +/- 8.2 mOsm/kg (p less than 0.01) on two occasions. No significant suppression of arginine vasopressin was seen during head-down tilt after mannitol infusion compared with values in a time control period. These results are consistent with an abnormality in baroreflex suppression of arginine vasopressin secretion in chronic congestive heart failure and suggest that such a defect may contribute to long-term high levels of arginine vasopressin in this condition.

Activation of neurohumoral systems following acute myocardial infarction

Previous studies have indicated that patients with an acute myocardial infarction have marked activation of all neurohumoral systems on admission to the hospital. This activation begins to subside within the first 72 hours so that by 7-10 days, all plasma neurohormones have returned to normal. The only documented exceptions were found to occur in patients with left ventricular dysfunction and overt heart failure, where both plasma renin activity and atrial natriuretic peptide were increased, and in patients with left ventricular dysfunction but no overt heart failure, where only atrial natriuretic peptide was increased. Although these studies suggest that neurohumoral activation rarely occurs at the time of hospital discharge, they were small and may have missed an important subgroup of patients with persistent neurohumoral activation. In the Survival and Ventricular Enlargement (SAVE) study, 522 patients had plasma neurohumoral levels measured at a mean of 12 days postinfarction. All SAVE patients had left ventricular dysfunction (left ventricular ejection fraction less than or equal to 40%), but no overt heart failure. In this group of patients, all neurohumoral levels (plasma renin activity, norepinephrine, arginine vasopressin, and atrial natriuretic peptide) were found to be increased compared with age-matched control subjects. These results indicate that, in fact, a subgroup of patients without overt heart failure has persistent neurohumoral activation at the time of hospital discharge postinfarction, and that this activation involves several neurohumoral systems. Since patients with persistent neurohumoral activation postinfarction are likely those most at risk of developing complications and the ones most likely to benefit from pharmacologic interventions blunting the effects of neurohumoral activation, measurement of predischarge neurohumoral levels may be useful.

A large-scale trial of captopril for mild to moderate heart failure in the primary care setting

A large-scale, prospective, 8-week, office-based study was conducted to evaluate the effects of adding captopril to a therapeutic regimen of diuretic and digoxin or diuretic alone in the management of patients with mild to moderate congestive heart failure (CHF). A total of 2218 primary care physicians evaluated 6669 patients over the study period for efficacy parameters, which included changes in a modified New York Heart Association (NYHA) functional classification, symptomatology, and daily activity levels. Overall, 63.8% of evaluated patients improved with regard to functional ability, with 19% improving two or more modified NYHA classes. Symptoms of CHF, including dyspnea on exertion, fatigue, and orthopnea and signs, including rales and peripheral edema, were reduced in 86% of these patients: 41.5% demonstrated mild improvement; 30.0%, moderate improvement; and 14.5%, marked improvement. Three parameters, with which patients reported having difficulty at study entry, were assessed serially to evaluate changes in functional capacity; 78.5% of patients reported an increased walking distance, 72.3% had increased capacity for climbing stairs, and 60.2% had improved capacity for individual recreational activities. Adverse experiences were reported in 18.1% of all patients; 4.9% of patients withdrew from the study because of an adverse effect. Combination therapy with captopril and diuretic for CHF was shown to be safe and effective regardless of patient age (less than 70 years vs. greater than or equal to 70 years), duration of heart failure (less than 1 year vs. greater than 1 year), presence of digoxin treatment, or the dosing schedule employed.(ABSTRACT TRUNCATED AT 250 WORDS)

Does the stress of admission to an intensive care unit influence arginine vasopressin secretion and renal diluting ability?

The pathogenesis of excessive arginine vasopressin (AVP) release and hyponatraemia in euvolaemic intensive care unit (ICU) patients is poorly understood. Stress has frequently been proposed as a possible determinant, but its actual responsibility has not been adequately assessed. Therefore, water-load tests were prospectively performed in 11 patients admitted to the ICU for severe or potentially severe diseases, but who had no other condition which could result in excessive AVP release or impairment of renal diluting ability. Renal diluting ability was normal in 9 patients. Two patients exhibited very slight defects, which might be the consequence of subclinical haemodynamic alterations, since one had a pulmonary embolism and the other manifested a gastrointestinal haemorrhage just after the completion of the water load. Nevertheless, plasma AVP levels decreased in response to the water load in all the patients, resulting in a significant decrease in mean values. Plasma norepinephrine values were found to be elevated both before and after water loading. A highly significant correlation existed between the levels of norepinephrine and those of AVP measured before the load, but was lost after it. In addition, norepinephrine values were markedly elevated in two patients who exhibited strictly normal renal diluting abilities, and no correlation was found between plasma norepinephrine values and any parameter of renal water excretion. Our study shows that the stress of a serious illness and of admission to an ICU does not seem to interfere, by itself, with osmotic regulation of AVP secretion and renal diluting ability, and that sympathetic activation is not, under such circumstances, a predominant stimulus for AVP release.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional and morphological characteristics of compensated and decompensated cardiac hypertrophy in dogs with chronic infrarenal aorto-caval fistulas

The relation between cardiac hypertrophy, shunt size, myocardial contractility, capillary density, adrenergic responsiveness, and neurohumoral stimulation was evaluated in dogs with compensated and decompensated cardiac hypertrophy caused by an infrarenal aorto-caval shunt. Shunt size varied from 5 to 35 mm2 due to an inability to create a uniform size. Dogs that developed heart failure within 4 months had 25 +/- 2 mm2 shunts, whereas those that developed it after 4 months had 19 +/- 3 mm2 shunts; those that did not develop heart failure had 10 +/- 1 mm2 shunts. Hypertrophy developed at the same rate in all the dogs that developed heart failure, which occurred at a critical heart weight (hypertrophy) for a given load (shunt size). In the dogs with heart failure there was a decrease in myocardial contractility (tension = 5.7 +/- 0.6 vs. 7.3 +/- 0.3 g/mm2, p less than 0.05), a decrease in adrenergic responsiveness (maximal heart rate with isoproterenol = 203 +/- 7 vs. 249 +/- 5 beats/min, p less than 0.01), an increase in circulating neurohormones, and a decrease in urinary sodium excretion (0.4 +/- 0.1 vs. 5.0 +/- 1.3 meq/3 hr, p less than 0.01). None of these abnormalities occurred in dogs with compensated hypertrophy. There were no differences in cardiac capillary density between the control dogs and the dogs with compensated cardiac hypertrophy or heart failure. Thus, it would appear that if heart failure is to develop after an initial toleration of a sudden volume overload, it will develop at a given combination of cardiac hypertrophy and volume overload, with cardiac hypertrophy developing at the same rate in all cases. In this model, once heart failure develops, myocardial contractility and cardiac adrenergic responsiveness are decreased and there is pronounced neurohumoral activation. All these changes are absent in hearts with compensated hypertrophy.

The use of angiotensin-converting enzyme inhibitors in congestive heart failure

The development of angiotensin-converting enzyme (ACE) inhibitors has been important in furthering our understanding of the pathophysiology of congestive heart failure and improving the care of these patients. ACE inhibitors have been shown to improve the longevity and quality of life of patients with congestive heart failure. They decrease neurohumoral over-activation, they restore baroreceptor reactivity, and in many cases they increase sodium and water excretion. If hypovolemia and an excessive decrease in renal perfusion pressure can be avoided, ACE inhibitors generally do not cause a deterioration of renal function and may even improve it. By decreasing myocardial metabolic demand, ACE inhibitors appear to have generally beneficial effects on myocardial metabolic balance. At low perfusion pressures, they also appear to maintain cerebral blood flow.

Water disturbances in cardiac failure

The non-osmotic stimulation of release of arginine vasopressin (AVP) seems to be the main determinant of the impaired water excretion and hyponatraemia in patients with cardiac failure. This non-osmotic stimulation of AVP release could be secondary to a decrease in stroke volume to which the ventricular receptors respond by decreasing the vagal afferent input to the hypothalamus via the mid-brain. Improvement of cardiac stroke volume would then decrease AVP release and improve water excretion. In cardiac failure, the non-osmotic stimulation of AVP release is not clearly modulated by the renin-angiotensin system or by the atrial natriuretic peptide plasma concentration. Nevertheless, physiological concentrations of atrial natriuretic peptide could inhibit the renal epithelial water transport at the collecting duct level. Water-loading and osmotic-loading experiments in patients with cardiac failure indicated that the release of AVP is still under osmotic control and favoured the concept that volume depletion in general and cardiac failure in particular may lower the osmotic threshold and increase the osmotic sensitivity to vasopressin release. Experiments using a specific vasopressin antagonist rarely indicated a vasoconstrictor role for endogenous AVP in either experimental or clinical cardiac failure. Intrarenal factors also contributed to the impaired water excretion observed in patients with cardiac failure: increased central sympathetic efferent discharge and stimulation of the renin-angiotensin-aldosterone system would be expected as a consequence of the decreased effective arterial blood volume. These effects could then decrease maximal reabsorption of solute further impairing the ability of the kidney to excrete free water. The impaired water excretion is correlated with the severity of the cardiac deterioration and thus has prognostic implications.

Neurohumoral and hemodynamic changes in congestive heart failure: lack of correlation and evidence of compensatory mechanisms

The objective of this study was to assess the hemodynamic and neurohumoral (plasma renin activity, aldosterone, epinephrine, norepinephrine, vasopressin, and atrial natriuretic peptide) determinants of systemic vascular resistance in 35 patients with stable congestive heart failure. In the supine position, although activation of the various neurohumoral systems tended to occur in the same patients, there was little correlation between activation of any of the neurohumoral systems, as reflected by circulating levels, and systemic vascular resistance. There was also little correlation between changes in circulating neurohormones and changes in either mean arterial pressure or systemic vascular resistance in the standing position. Acutely reducing the activity of the renin-angiotensin system with the use of captopril did not improve the correlation between other neurohumoral and hemodynamic variables. In fact there was no correlation between the effects of acute captopril therapy and baseline renin values. These results support the concept that activation of one or another vasoconstrictor neurohumoral system varies from patient to patient and that the effects of their activation are tempered by activation of parallel vasodilator systems and by attenuation of neurohormone release and effector organ response.

Congestive heart failure

Congestive heart failure (CHF) is not a single entity but a symptom complex that may represent the consequence of mechanical abnormalities, myocardial abnormalities, and/or disturbances of cardiac rhythm. In turn, it affects virtually every organ system in the body. This review focuses on CHF due to systolic dysfunction of the left ventricle, which comprises the majority of cases of this condition. Recent data suggest that CHF may be the most frequent primary diagnosis in patients on medical services in nonmilitary hospitals in this country: it affects approximately 2% of the United States population, or some 4 million people. The mortality rate for CHF is also worse than for many forms of cancer; thus, new therapeutic alternatives are imperative. In order to devise new therapeutic strategies, a detailed understanding of the pathophysiology of this condition is required. The relative advantages and disadvantages of various pharmacologic and nonpharmacologic approaches are considered in detail. Certain medications, such as the angiotensin converting enzyme (ACE) inhibitors, have been shown to improve survival, and heart transplantation is clearly life-saving for those who are eligible for this therapy. However, the real challenge is to devise strategies to prevent the occurrence of heart failure, or interrupt its progress at a very early stage.

New trends in the use of angiotensin converting enzyme inhibitors in chronic heart failure

Although the underlying pathophysiology in most patients with congestive heart failure is impaired myocardial contractility, hemodynamic and clinical benefit can be achieved by treatment with agents that alter the loading conditions of the left ventricle. This was initially accomplished with direct-acting vasodilators such as sodium nitroprusside, nitrates, and hydralazine. Subsequently, the angiotensin converting enzyme (ACE) inhibitors have been demonstrated to produce similar short-term hemodynamic improvement and have generally proved superior in their long-term hemodynamic and clinical efficacy. Although the ACE inhibitors were initially employed as adjunctive treatment in patients with refractory heart failure, recent studies indicate that they are also effective in patients with mild and moderate symptoms and that they are at least as effective as digitalis in this patient group. Furthermore, a growing body of data indicates that the ACE inhibitors improve the survival rate in patients with severe and, possibly, milder heart failure. As a result, the ACE inhibitors have emerged as useful agents in patients with mild symptoms and are being investigated for their potential to improve the survival rate and prevent clinical deterioration in patients with asymptomatic or minimally symptomatic left ventricular dysfunction.