Total body electrolyte composition in patients with heart failure: a comparison with normal subjects and patients with untreated hypertension

The relationship between serum potassium levels and cardiac arrhythmias in left ventricular assist device (LVAD) recipients: a comprehensive analysis and prognostic evaluation

BACKGROUND

This study aimed to comprehensively analyze the relationship between serum potassium (K+) levels and the risk of de novo cardiac arrhythmias in left ventricular assist device (LVAD) recipients.

METHODS

We performed a retrospective study using the INTERMACS registry. Data was collected on adult patients with available K+ measurements taken 1-month post-LVAD implantation. K+ levels were the main exposure of interest and were analyzed as a continuous and categorical variable (quartiles of baseline K+ distribution). The main outcome of interest was the occurrence of de novo arrhythmia events, either sustained (ventricular [VA] or supraventricular arrhythmia [SVA]) or not sustained (atrial fibrillation/flutter [AF]). All-cause mortality was evaluated as the secondary outcome. Multivariable adjusted time-dependent Cox regression models and natural splines were used to describe the relationship between the exposure and outcomes of interest.

RESULTS

10,570 patients met our inclusion criteria. A significant and consistent relationship was observed between the lowest quartile of longitudinal K+ and the risk of arrhythmic events (HR 1.28, 95% CI 1.08, 1.53, p = 0.005) as well as in the highest K+ quartile (HR 1.24, 95% CI 1.02, 1.49, p = 0.027). A similar relationship was confirmed in the stratified analysis of arrhythmia types for SVAs and AF. The data were reflected in a U shaped relationship. Similarly, the highest and lowest quartiles of longitudinal K+ were independently associated with a significant increase in the HR of death, which was reflected by a U shaped relationship.

CONCLUSIONS

Our study reveals a significant U shaped relationship between low and high K + levels and cardiac arrhythmias in LVAD patients, particularly SVAs and AF. Both high and low K + levels negatively impacted patient survival.

The Congestion "Pandemic" in Acute Heart Failure Patients

Congestion not only represents a cardinal sign of heart failure (HF) but is also now recognized as the primary cause of hospital admissions, rehospitalization, and mortality among patients with acute heart failure (AHF). Congestion can manifest through various HF phenotypes in acute settings: volume overload, volume redistribution, or both. Recognizing the congestion phenotype is paramount, as it implies different therapeutic strategies for decongestion. Among patients with AHF, achieving complete decongestion is challenging, as more than half still experience residual congestion at discharge. Residual congestion is one of the strongest predictors of future cardiovascular events and poor outcomes. Through this review, we try to provide a better understanding of the congestion phenomenon among patients with AHF by highlighting insights into the pathophysiological mechanisms behind congestion and new diagnostic and management tools to achieve and maintain efficient decongestion.

Congestion in Heart Failure: From the Secret of a Mummy to Today's Novel Diagnostic and Therapeutic Approaches: A Comprehensive Review

This review paper presents a review of the evolution of this disease throughout the centuries, describes and summarizes the pathophysiologic mechanisms, briefly discusses the mechanism of action of diuretics, presents their role in decongesting heart failure in patients, and reveals the data behind ultrafiltration in the management of acutely or chronically decompensated heart failure (ADHF), focusing on all the available data and advancements in this field. Acutely decompensated heart failure (ADHF) presents a critical clinical condition characterized by worsening symptoms and signs of heart failure, necessitating prompt intervention to alleviate congestion and improve cardiac function. Diuretics have traditionally been the mainstay for managing fluid overload in ADHF. Mounting evidence suggests that due to numerous causes, such as coexisting renal failure or chronic use of loop diuretics, an increasing rate of diuretic resistance is noticed and needs to be addressed. There has been a series of trials that combined diuretics of different categories without the expected results. Emerging evidence suggests that ultrafiltration may offer an alternative or adjunctive approach.

Hypochloraemia in Patients with Heart Failure: Causes and Consequences

Hypochloraemia is a common electrolyte abnormality in patients with heart failure (HF). It has a strong association with adverse outcome regardless of HF phenotype and independent of other prognostic markers. How hypochloraemia develops in a patient with HF and how it might influence outcome are not clear, and in this review we explore the possible mechanisms. Patients with HF and hypochloraemia almost invariably take higher doses of loop diuretic than patients with normal chloride levels. However, renal chloride and bicarbonate homeostasis are closely linked, and the latter may be influenced by neurohormonal activation: it is likely that the etiology of hypochloraemia in patients with HF is multifactorial and due to more than just diuretic-induced urinary losses. There are multiple proposed mechanisms by which low chloride concentrations may lead to an adverse outcome in patients with HF: by increasing renin release; by a stimulatory effect on the with-no-lysine kinases which might increase renal sodium-chloride co-transporter activity; and by an adverse effect on myocardial conduction and contractility. None of these proposed mechanisms are proven in humans with HF. However, if true, it might suggest that hypochloraemia is a therapeutic target that might be amenable to treatment with acetazolamide or chloride supplementation.

Acid-base and electrolyte abnormalities in heart failure: pathophysiology and implications

Electrolyte and acid–base abnormalities are a frequent and potentially dangerous complication in subjects with congestive heart failure. This may be due either to the pathophysiological alterations present in the heart failure state leading to neurohumoral activation (stimulation of the renin–angiotensin–aldosterone system, sympathoadrenergic stimulation), or to the adverse events of therapy with diuretics, cardiac glycosides, and ACE inhibitors. Subjects with heart failure may show hyponatremia, magnesium, and potassium deficiencies; the latter two play a pivotal role in the development of cardiac arrhythmias. The early identification of these alterations and the knowledge of the pathophysiological mechanisms are very useful for the management of these patients.

The meaning of hypokalemia in heart failure

Maintenance of normal potassium (K(+)) homeostasis has become an increasingly important limiting factor in the therapy of heart failure (HF). With the application of loop diuretics and digoxin, hypokalemia has become a frequent and feared side effect of treatment. Low serum K(+) in HF may be also a marker of increased neurohormonal activity and disease progression. To gain the maximum benefit from treatment, we need to individualize drug use and carefully monitor electrolytes. Symptomatic HF patients (New York Heart Association class III-IV) should be prescribed the lowest dose of diuretic necessary to maintain euvolemia. Mild hypokalemia may be corrected by the use of aldosterone receptor antagonists such as spironolactone or eplerenone. However, a more severe hypokalemia should preferably be corrected using K(+) supplement. Serum K levels should be frequently checked and maintained between 4.0 and 5.5 mEq/l (mmol/l).

Plasma potassium level is associated with common genetic variation in the beta-subunit of the epithelial sodium channel

Plasma potassium is a moderately heritable phenotype, but no robust associations between common single nucleotide polymorphisms (SNPs) and plasma potassium have previously been described. Genetic influences on renal potassium handling could be important in the etiology of hypertension. We have tested whether common genetic variation in the gene encoding the beta-subunit of the epithelial sodium channel (SCNN1B) affects plasma potassium and blood pressure level in a study of 1,425 members of 248 families ascertained on a proband with hypertension. We characterized family members for blood pressure using ambulatory monitoring, measured plasma potassium in venous blood samples, and genotyped four SNPs that spanned the SCNN1B gene. We found highly significant association between genotype at the SCNN1B rs889299 SNP situated in intron 4 of the gene and plasma potassium. Homozygotes for the rarer T allele had on average a 0.15 mM lower plasma potassium than homozygotes for the common C allele, with an intermediate value for heterozygotes (trend, P = 0.0003). Genotype at rs889299 accounted for approximately 1% of the total variability in plasma potassium, or around 3% of the total heritable fraction. There was no association between genotype at any SCNN1B SNP and blood pressure considered as a quantitative trait, or with hypertension affection status. We have shown a modest sized but highly significant effect of common genetic variation in the SCNN1B gene on plasma potassium. Interaction between the rs889299 SNP and functional SNPs in other genes influencing aldosterone-responsive distal tubular electrolyte transport may be important in the etiology of essential hypertension.

What is the optimal serum potassium level in cardiovascular patients?

Humans are prone to sodium overload and potassium depletion. This electrolyte imbalance is important in the pathogenesis of cardiovascular disease and sudden cardiac death. Avoiding hypokalemia is beneficial in several cardiovascular disease states including acute myocardial infarction, heart failure, and hypertension. The evidence highlighting the importance of potassium homeostasis in cardiovascular disease and possible mechanisms explaining potassium's benefits are reviewed. Targets for serum potassium concentration are suggested.

Dietary salt and hypertension: a scientific issue or a matter of faith?

Many workers have an overly simplistic view of the relationship between salt intake and hypertension. This article attempts a critical evaluation of some of the evidence.

Cardiac complications in the intensive care unit

Advances in the care of critically ill patients has been startling, especially in patients with acute coronary syndromes. With new therapies and procedures, however, have come new complications. On balance, our patients are better off, but the stakes are now higher and the complications more serious. The need for constant vigilance has never been greater.

Body composition and energy expenditure of patients with chronic cardiac failure

BACKGROUND

Patients with acute cardiac failure have excess body water, and it is commonly assumed that this is also so in patients with stable chronic cardiac failure (CCF).

METHODS

To investigate this, we measured total body water (TBW) using stable isotope dilution and single-frequency bioelectrical impedance (BIA), and also extracellular volume (ECV) using bromide dilution in 12 patients with CCF and eight matched control subjects.

RESULTS

TBW [kg(-1) bodyweight] was similar in the two groups [median 18O dilution 53.2% (range 46.5-57.1%) in patients vs. 54.8% (47.9-62.7) in control subjects; BIA 56.6% (42.7-73.1) vs. 58.0% (52.0-68.6)]. ECV was also similar in the two groups [0.25 Lkg(-1) (0.20-0.29) vs. 0.25 (0.19-0.35)]. There was a strong correlation between stable isotope and BIA measurements of TBW for all subjects (r = 0.76), but BIA overestimated TBW by a mean difference of 2.4 kg (limits of agreement of -4.1 kg to +8.9 kg). Body fat content was similar in the two groups, whether measured by skinfold anthropometry, whole-body densitometry or by 18O dilution. Resting energy expenditure (REE), calculated from indirect calorimetry, and total energy expenditure (TEE), calculated from the ratio of 2H to 18O elimination rate after drinking doubly labelled water, were also similar in the two groups.

CONCLUSION

It is concluded that the patients with stable CCF in this study had normal ECV and TBW, and so excess body water did not account for their persistent symptoms.

Effectiveness of spironolactone added to an angiotensin-converting enzyme inhibitor and a loop diuretic for severe chronic congestive heart failure (the Randomized Aldactone Evaluation Study [RALES])

The present study enrolled 214 patients, aged 26 to 83 years, with symptomatic New York Heart Association class II through IV congestive heart failure. Patients were continued on their previous therapeutic regimens, which included an angiotensin-converting enzyme (ACE) inhibitor and a loop diuretic with or without digitalis. Patients were randomized to 1 of 5 parallel treatment groups: placebo or spironolactone at a single daily dose of 12.5, 25, 50, or 75 mg for 12 weeks. Serum levels of creatinine, urea nitrogen, potassium, plasma renin activity, and N-terminal proatrial natriuretic factor (pro-ANF), as well as urinary aldosterone levels, were measured periodically. Measurements at 12 weeks versus baseline values indicated significant increases in plasma renin activity and aldosterone excretion and significant decreases in systolic and diastolic blood pressure and pro-ANF. Hypokalemia (serum potassium < 3.4 mmol/L) occurred in 10% of placebo-treated patients and in 0.5% of the spironolactone group. The incidence of hyperkalemia (serum potassium > or = 5.5 mmol/L) was 5% for the placebo group, whereas it was 5%, 13%, 20%, and 24% for the 12.5-, 25-, 50- and 75-mg spironolactone treatment groups, respectively. Predictors of hyperkalemia included the use of ACE inhibitors other than captopril, ACE inhibitor dose, and baseline elevation of serum creatinine or potassium levels. Thus, daily doses of 12.5 to 25 mg of spironolactone coadministered with conventional therapy of ACE inhibitors, loop diuretics, and digitalis are relatively safe (provided that serum potassium levels are monitored) and effective in blocking the effects of aldosterone, while reducing the potential for hypokalemia in patients with heart failure.

Electrolyte disturbances in chronic heart failure: metabolic and clinical aspects

The pathophysiology of congestive heart failure (CHF) includes conditions (e.g., activation of the renin-angiotensin-aldosterone system) which, when combined with CHF therapies, make patients afflicted with this syndrome quite susceptible to electrolyte disturbances. The most commonly encountered are hyponatremia, hypokalemia, and hypomagnesemia. These derangements are of vast clinical importance; their development not only represents an immediate threat to the CHF patient (e.g., dysrhythmias secondary to hypokalemia), but are also indicative of underlying pathophysiologic events, an unfavorable clinical course, and occasionally an adverse therapeutic response. The optimal care of CHF patient includes the recognition and management of these electrolyte disturbances.

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.

Angiotensin-converting enzyme inhibitors, left ventricular dysfunction, and early heart failure

A study was undertaken to examine the effects of the angiotensin-converting enzyme inhibitor lisinopril on exercise performance in 18 patients with major impairment of left ventricular systolic function. The study was a randomized, double-blind, crossover design, and patients received treatment with either once-daily lisinopril (2.5-10 mg) or placebo for a period of 6 weeks. A total of 15 patients completed the study. Compared with placebo, lisinopril had no significant effect on supine or standing blood pressure or heart rate. Although lisinopril had no effect on exercise duration during a low-intensity exercise protocol, in patients undergoing a high-intensity exercise protocol, there was a trend toward improved exercise time and peak oxygen consumption improved significantly. In addition, treatment with lisinopril resulted in an increase in renal blood flow and a reduction in glomerular filtration rate. Moreover, administration of once-daily lisinopril 10 mg resulted in a decrease in plasma concentrations of angiotensin II, aldosterone, and atrial natriuretic peptide, and an increase in plasma concentrations of active renin.

Cardiac myocyte necrosis induced by angiotensin II

Although the role of angiotensin II (Ang II) in the pathogenesis and progression of the failing heart is uncertain, previous reports have suggested that myocyte injury may be a component in this process. In this study, we investigated this possibility in more detail. Cardiotoxic effects of nonacutely hypertensive doses of Ang II were examined in 90 rats, including those receiving an angiotensin infusion (200 ng/min i.p.) and those with renovascular hypertension, where endogenous stimulation of Ang II occurred. Myocyte injury and wound healing resulting from these treatments were evaluated by 1) immunofluorescence after in vivo monoclonal antibody labeling of myosin to detect abnormal sarcolemmal permeability, 2) [3H]thymidine incorporation into DNA, to detect fibroblast proliferation, and 3) light microscopic evidence of myocytolysis and subsequent scar formation. We found that exogenous Ang II produced multifocal antimyosin labeling of cardiac myocytes and myocytolysis, which were maximal on days 1-2 of the infusion. Subsequently, DNA synthesis rates were increased, with fibroblast proliferation reaching peak levels on day 2 (Ang II-treated rats, 90.0 +/- 18.6 cpm/micrograms DNA; control rats, 11.4 +/- 2.3 cpm/micrograms DNA; p less than 0.05); microscopic scarring was found on day 14 and represented 0.12 +/- 0.02% of the myocardium. Concurrent treatment with both propranolol (30 mg/kg/day s.c.) and phenoxybenzamine (5 mg/kg/day i.m.) did not attenuate Ang II-induced antimyosin labeling. Increased endogenous Ang II, resulting from renal ischemia after abdominal aortic constriction, produced both antimyosin labeling and increased rates of DNA synthesis like that observed with Ang II infusion. Both myocyte injury and fibroplasia were prevented with captopril (65 mg/day p.o.), but this protective effect was not seen with reserpine pretreatment. Infrarenal aortic banding without renal ischemia, on the other hand, produced hypertension without necrosis. We conclude that pathophysiological levels of endogenous as well as low-dose exogenous Ang II were associated with altered sarcolemmal permeability and myocytolysis with subsequent fibroblast proliferation and scar formation. Myocyte injury was unrelated to the hypertensive or enhanced adrenergic effects of Ang II or to hypertension per se. Captopril was effective in preventing myocyte injury in renovascular hypertension. The mechanism(s) responsible for Ang II-induced necrosis will require further study.

Acute heart failure: determinants of outcome

We prospectively studied 69 consecutive patients hospitalized with a primary diagnosis of acute left ventricular failure so as to assess the impact of vasodilators on incidence and morbidity of acute symptomatic left ventricular failure. The determinants of duration of hospitalization, in-hospital mortality and symptomatic status 2 months after discharge were examined. There were 9 in-hospital deaths (13%), and survival at 60 days was 77%. Median duration of hospitalization was 9 days, and 33% of the surviving patients remained in New York Heart Association functional class III-IV 60 days subsequent to discharge. Of the patients, 49 (76%) had previously received treatment for left ventricular failure: 30 (61%) of these had received vasodilators, most commonly angiotensin converting enzyme inhibitors and nitrates. Ischaemic chest pain was present in 34 (49%) of the patients. Acute utilization of vasodilators (45% of patients) was largely limited to nitrate therapy associated with ischaemic chest pain (P less than 0.01). Multiple logistic regression revealed previous left ventricular failure, advanced age and hypokalaemia as significant correlates of prolonged hospitalization (greater than 9 days). Previous left ventricular failure was also predictive of persistent severe disability two months subsequent to discharge. No factor was a significant predictor of in-hospital death. Although preceding treatment with digoxin and incremental angiotensin converting enzyme inhibitor therapy tended to predict brief hospitalization, the parameter of acute ischaemia, other biochemical anomalies and modes of acute or chronic therapy were not significant correlates of any end point. We conclude that preceding disability, rather than mode of treatment, predicts an adverse outcome in acute left ventricular failure.

Tissue and plasma angiotensin converting enzyme and the response to ACE inhibitor drugs

1. There is a body of circumstantial and direct evidence supporting the existence and functional importance of a tissue based RAS at a variety of sites. 2. The relation between circulatory and tissue based systems is complex. The relative importance of the two in determining haemodynamic effects is unknown. 3. Despite the wide range of ACE inhibitors already available, it remains unclear whether there are genuine differences related to tissue specificity. 4. Pathological states such as chronic cardiac failure need to be explored with regard to the contribution of tissue based ACE activities in generating acute and chronic haemodynamic responses to ACE inhibitors. 5. The role of tissue vs plasma ACE activity may be clarified by study of the relation between drug concentration and haemodynamic effect, provided that the temporal dissociation is examined and linked to circulating and tissue based changes in ACE activity, angiotensin peptides and sympathetic hormones.

Potential role of potassium as a determinant of morbidity and mortality in patients with systemic hypertension and congestive heart failure

Prehistoric animals and humans consumed a diet low in sodium but high in potassium, and thus, evolutionary forces fostered the development of physiologic systems that conserved sodium and excreted potassium. With the advent of civilized societies, food cooking and processing have greatly increased the sodium but decreased the potassium content of the diet. However, there has been little time for physiologic systems to adapt. The resulting excess of sodium has been implicated as an important factor in the development of hypertension and congestive heart failure. This traditional focus on sodium has ignored the potential role that an inadequate dietary intake of potassium might play in the degenerative diseases of the heart, brain and kidney. Yet dietary potassium may be as powerful a determinant of cardiovascular morbidity and mortality as dietary sodium. In experimental and clinical hypertension, an increased intake of potassium (without a change in dietary sodium) can reduce blood pressure, may suppress the activity of the sympathetic nervous and renin-angiotensin systems, and can prevent the development of vascular injury; conversely, potassium depletion has been associated with an increase in stroke and sudden death. In patients with chronic heart failure, potassium can modify both the mechanical and electrical properties of the heart, it can exert diuretic effects, and it can reduce the frequency and complexity of potentially lethal ventricular tachyarrhythmias. Given this central role, the effects of many pharmacologic interventions on the morbidity and mortality of patients with hypertension or chronic heart failure can be enhanced or diminished by the effect that these treatments might have on potassium homeostasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of the sympathetic nervous system and electrolytes in congestive heart failure

Congestive heart failure is characterized by both disturbances in electrolyte homeostasis and neuro-hormonal regulation. Total body potassium is reduced, and this reduction bears a modest relation to activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system. Patients with decompensated heart failure show increases in both plasma epinephrine and plasma norepinephrine, whereas patients with chronic stable heart failure usually have an increase only in plasma norepinephrine. High levels of circulating epinephrine may contribute to the development of hypokalemia by activating skeletal muscle and liver membrane beta 2-adrenergic receptors, which in turn stimulate intracellular cyclic adenosine monophosphate to activate the membrane-bound Na+K(+)-adenosine triphosphatase pump. The net result is that potassium flux across the cell membrane from the extracellular to the intracellular space increases, setting the stage for hypokalemia and possibly serious ventricular arrhythmias. Other mechanisms that may contribute to the development of hypokalemia in heart failure include the kaliuresis brought on by excessive levels of aldosterone. Moreover, it is likely that the activity of facilitated by concomitant activation of the renin-angiotensin system. Increased sympathetic nerve activity may then release additional renin from the kidney (by way of a beta 2-adrenergic mechanism). Therefore, both the sympathetic nervous system and the adrenal medulla may interact to cause hypokalemia in patients with heart failure. Because hypokalemia is known to predispose patients to ventricular arrhythmias, it may be prudent to aggressively maintain serum potassium levels in patients with heart failure in the range of 4 to 5 mEq/liter.

Interrelation of electrolytes and renin-angiotensin system in congestive heart failure

Many of the electrolyte derangements seen in chronic heart failure are related to activation of the renin-angiotensin system. Activation of the system may cause the retention of both sodium and water; the former is primarily related to the release of aldosterone and the latter is related to an angiotensin-mediated increase in thirst and decrease in the excretion of free water. The interaction of these mechanisms may explain why patients with chronic heart failure have higher values for total body sodium but lower values for serum sodium concentration than hypertensive patients or normal subjects. Activation of the renin-angiotensin system may also cause potassium depletion, which is manifest clinically by a decrease in both total body potassium and serum potassium concentration. These electrolyte disturbances may play a role in the development of ventricular arrhythmias. The renin-angiotensin system may also contribute to the development of magnesium deficits. These hormone-electrolyte interactions have important implications in the treatment of patients with heart failure, especially those in whom the renin-angiotensin system is pharmacologically inhibited.

Enalapril for severe heart failure in infancy

Eight infants aged between 4 days and 12 weeks with severe heart failure that was refractory to optimal conventional treatment with diuretics were treated with enalapril. The starting dose was 0.1 mg/kg/day, increasing according to response to 0.12-0.43 mg/kg/day. One infant with severe myocarditis did not tolerate enalapril because of hypotension and later died of intractable heart failure. Six of the remaining patients had congenital systemic to pulmonary shunts and one had a simple aortic coarctation. Two weeks after starting enalapril the clinical features of heart failure had improved in all the infants, the mean (SEM) plasma sodium concentration had increased from 129 (2.4) to 136 (1.1) mmol/l and plasma urea concentration had fallen from 7.0 (0.85) to 2.9 (0.85) mmol/l. These data suggest that enalapril is a potentially useful treatment for severe heart failure in infancy.

Acute and long-term renal and metabolic effects of piretanide in congestive cardiac failure

1. The renal and metabolic effects of the sulphamoylbenzoic acid diuretic, piretanide, have been studied, under controlled dietary conditions, in 39 patients with congestive cardiac failure. 2. In acute studies, peak saluresis occurred within 4 h of oral piretanide administration; saluresis was complete within 6 h, after which a significant antidiuretic effect was observed. Addition of triamterene, 50 mg, blunted the 0-6 h kaliuretic effect of piretanide. Over 24 h, piretanide, alone, caused insignificant urinary losses of potassium when compared with control. 3. In comparative studies, the piretanide dose-response curve was found to be parallel to that of frusemide over the dose range studied. The 0-6 h saluretic responses of piretanide, 6, 12 and 18 mg, were found to be equivalent to frusemide, 40, 80 and 120 mg respectively. The collective mean ratios of all the saluretic responses to each dose of piretanide with the corresponding dose of frusemide was observed to be 0.99 +/- 0.12, over 0-6 h period, and 0.86 +/- 0.09 over the 24 h period. The relative potency of piretanide, when compared with frusemide was found to be 6.18 (95% confidence limits 4.87-8.33), over the 0-6 h period, and 4.73 (95% confidence limits 3.65-6.14), over 24 h period. 4. In 15 patients in severe cardiac failure, urinary recovery of piretanide, over first 6 h, at the start of treatment was 21.2 +/- 2.1% while efficiency of the diuretic (mmol Na/mg drug) was 47.3 +/- 4.1. Long-term piretanide therapy was continued in the same group for up to and in some cases over 3 years. No other diuretics or potassium supplements were given. Piretanide dosage ranged from 6 to 24 mg day-1 according to clinical need. Plasma potassium fell significantly at 12 and 24 months, though remaining within the normal range. At these same times, significant elevations in both plasma urate and total fasting cholesterol were observed. Two patients developed overt gout on high dose piretanide therapy (24 mg day-1). Piretanide was well tolerated, and effective in the management of congestive cardiac failure without any other recognized metabolic or electrolyte changes.

Arrhythmias, catecholamines and electrolytes

The prognosis in patients with heart failure secondary to left ventricular dysfunction is poor. Although survival can be related to the extent of cardiac functional impairment, many patients die suddenly rather than in refractory heart failure. Ambulatory electrocardiography has revealed a high prevalence of simple and complex ventricular arrhythmias in these patients, which was the most important predictor of subsequent mortality in our patients. Factors predisposing to arrhythmias are many, but increased catecholamines and electrolyte abnormalities are among the more obvious. In patients who have undergone treatment for congestive heart failure, serum and total body potassium are reduced, and this is closely and inversely related to the state of activation of the renin-angiotensin system. Renin and noradrenaline are also closely and directly correlated, while both are inversely related to the arterial pressure. Treatment with angiotensin-converting enzyme inhibitors tends to reverse these neuroendocrine and electrolyte abnormalities and reduces the frequency of ventricular arrhythmias. Whether this will have a favorable impact on mortality, and, in particular, on sudden death, remains to be seen.

Mortality in heart failure: clinical variables of prognostic value

One hundred and fifty two patients with chronic heart failure caused primarily by left ventricular dysfunction were followed prospectively in an open study for a mean period of 21 months. The effects of several clinical variables on subsequent outcome were examined, including the effects of treatment, which was determined by the clinician caring for the patient and was not randomly allocated. In order of importance, frequent ventricular extrasystoles, non-treatment with amiodarone, low mean arterial pressure, and a diagnosis of coronary artery disease were associated with a poor prognosis, with each of these variables providing extra predictive information independently of the others. Initial serum potassium concentration and treadmill exercise time also carried further weak but independent prognostic information. Neither treatment with angiotensin converting enzyme inhibitors nor digoxin appeared to affect outcome. Left ventricular function (as reflected by M mode echocardiography) and the dose of diuretic also failed to predict outcome. There did, however, appear to be a reduction in the frequency of sudden death when angiotension converting enzyme inhibitors were given. Further studies are required to confirm the adverse prognostic significance of ventricular arrhythmias in patients with heart failure and the possible benefit associated with amiodarone treatment.