Hemodynamic effects of digoxin in latent cardiac failure

Evolution of the chronic congestive heart failure paradigm

Paradigms are a part of our human nature. In the world of medicine and science, they allow investigators to work within a particular, previously accepted framework that provides certain constraints. This is the crux of Newton's quote, "If I've seen so far it's because I stood upon the shoulders of giants." However, in the same way that it allows us to build, it can constrain our thought processes if we fail to accept new data that are ill suited to an accepted paradigm. The physiological mechanisms to explain the phenomenon of chronic congestive heart failure are similar to other paradigms of science, in that they have undergone several shifts throughout their history, and continue to change with new evidence. Here, we seek to explore how our understanding of congestive heart failure has changed.

Effects of intravenous digoxin on pulmonary venous and transmitral flows in patients with chronic heart failure of different degrees

Acute effects of digoxin on diastole were evaluated noninvasively by combining data simultaneously obtained by Doppler echocardiograms (echo-Doppler) of transmitral and pulmonary venous flow curves in 38 patients with dilated and failing hearts, who had been stable for at least 7 days before the study. According to the resting ejection fraction (EF), patients were subdivided into Group 1 (EF < 30%: n = 20, mean EF values 23 +/- 8%) and Group 2 (EF > or = 30%: n = 18, mean EF values 40 +/- 3%). Significant differences were observed at rest between the two groups in both transmitral (shorter deceleration time and isovolumic relaxation time and increased peak E and E/A ratio in Group 1 vs. Group 2) and transpulmonary (reduced systolic forward component and systolic fraction of the flow curves in Group 1 compared with Group 2 and control subjects) parameters. Digoxin (1 mg subdivided into two doses, each infused over a 15-min period with 2 h between the doses) significantly modified the diastolic profile in Group 1 patients in the absence of statistically relevant changes in EF: a significant decrease of transmitral peak E (from 76 +/- 17 to 60 +/- 15 cm/s, p < 0.05) and E/A ratio (from 2.5 +/- 1 to 1.6 +/- 0.6; p < 0.05) and a significant lengthening of deceleration time (from 115 +/- 20 to 160 +/- 18 ms; p < 0.05) were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

The development of positive inotropic agents for chronic heart failure: how have we gone astray?

Because cardiac contractility is impaired in chronic heart failure, many pharmacologic agents have been developed to increase the contractile state of the failing heart. These drugs produce impressive hemodynamic effects, but long-term therapy has failed to produce clinical benefits and has increased mortality in treated patients. This experience has led many physicians to suggest that positive inotropic therapy be abandoned as a therapeutic approach for heart failure. However, recent studies suggest that the efficacy and safety of many (if not all) positive inotropic drugs can be greatly enhanced by reducing the dose of these drugs. The importance of dose is dramatically illustrated by the results of trials with vesnarinone, which decreases mortality when used in low doses but increases mortality when administered in doses only twice as large. Although low doses of positive inotropic drugs may be clinically superior to high doses, it is not clear that these low doses exert significant inotropic effects. All positive inotropic drugs exert actions on the circulation in addition to stimulating the heart, and these ancillary properties may be particularly important at low doses of these drugs. Low doses of milrinone and pimobendan may act primarily to dilate peripheral blood vessels; low doses of digitalis may exert only neurohormonal effects, and low doses of vesnarinone may act as an antiarrhythmic agent. If the noninotropic actions of low doses account for the therapeutic benefits of these drugs, then the positive inotropic effects seen at high doses may be primarily responsible for their adverse effects.(ABSTRACT TRUNCATED AT 250 WORDS)

How should physicians view heart failure? The philosophical and physiological evolution of three conceptual models of the disease

During the last 50 years, physicians have developed three distinct conceptual models of heart failure that have provided a rational basis for the treatment of the disease. In the 1940s through the 1960s, physicians regarded heart failure principally as an edematous disorder and formulated a cardiorenal model of the disease in an attempt to explain the sodium retention of these patients. This model led to the widespread use of digitalis and diuretics. In the 1970s and 1980s, physicians viewed heart failure principally as a hemodynamic disorder and formulated a cardiocirculatory model of the disease in an attempt to explain patients' symptoms and disability. This model led to the widespread use of peripheral vasodilators and the development of novel positive inotropic agents. Now, in the 1990s, physicians are beginning to think about heart failure as a neurohormonal disorder in an attempt to explain the progression of the disease and its poor long-term survival. This new conceptual framework has led to the widespread use of converting-enzyme inhibitors and the development of beta blockers for the treatment of heart failure. Which conceptual model most accurately describes the syndrome of heart failure and leads physicians to utilize the most effective treatment? This paper critically reviews the available evidence supporting and refuting the validity of all three models of heart failure. We conclude that, to varying degrees, all three approaches provide useful, but incomplete, insights into this physiologically complex and therapeutically challenging disease.

Acute hemodynamic effects of digoxin alone or in combination with other vasoactive agents in patients with congestive heart failure

Although digitalis preparations have been in use for greater than 200 years, it is only within the last 2 decades that the central hemodynamic and neurohumoral effects occurring over several hours following intravenous administration of digoxin have been investigated in patients with congestive heart failure (CHF). Although digoxin has been shown to stimulate myocardial contractility in tissue preparations, its positive inotropic activity does not consistently translate into improvements in hemodynamic measurements in humans. Digoxin given intravenously results in increased cardiac index and decreased heart rate, left ventricular filling pressure, and right atrial pressure, as well as in acute attenuation of neurohumoral abnormalities, in patients with chronic CHF who have abnormal baseline hemodynamic measurements. Unlike other drugs with positive inotropic activity, however, digoxin does not influence hemodynamics in normal volunteers or in CHF patients in whom hemodynamics have been normalized with other therapies. These differing effects may be related to the drug's diverse peripheral vascular effects in CHF patients in whom vasodilation may occur in comparison with those that occur in normal subjects in whom the peripheral vasoconstrictor effects may prevent the inotropic effects of the drug from being translated into an increase in cardiac output. The hemodynamic effects of digoxin in patients with chronic CHF due primarily to diastolic dysfunction have not been fully investigated. Intravenous digoxin produces hemodynamic effects in patients with CHF associated with acute myocardial infarction, but these changes are small compared with those resulting from the administration of dobutamine. Digoxin does not appear to influence hemodynamic measurements in patients with right ventricular dysfunction unless concomitant left ventricular failure is present. In patients with chronic left ventricular dysfunction, the hemodynamic effects of intravenous digoxin and vasodilators are enhanced when these agents are given in combination.

Comparative hemodynamic and neurohormonal effects of intravenous captopril and digoxin and their combinations in patients with severe heart failure

The effects of intravenous captopril and intravenous digoxin given separately and in combination on rest and exercise hemodynamics were studied in 16 patients with severe heart failure and sinus rhythm. When given separately, both captopril and digoxin decreased the pulmonary capillary wedge pressure by, respectively, 24% (p = 0.003) and 34% (p = 0.004) and systemic vascular resistance by 23% (p = 0.09) and 20% (p = 0.03). Only digoxin increased cardiac index by 23% (p = 0.03) and stroke work index by 52% (p = 0.01). During maximal exercise, captopril alone decreased systemic vascular resistance by 28% (p = 0.0002) and increased cardiac index by 33% (p = 0.02). Digoxin alone decreased pulmonary capillary wedge pressure by 11% (p = 0.04) and increased stroke work index by 44% (p = 0.01). The combination of captopril and digoxin resulted in a decrease in pulmonary capillary wedge pressure and systemic vascular resistance and an increase in cardiac index and stroke work index both at rest and during exercise that was greater than values observed with either drug given alone. Cardiac index response to the combination of captopril and digoxin correlated with baseline serum aldosterone concentration (r = 0.81, p less than 0.001) and plasma renin activity (r = 0.74, p less than 0.0002). A significant decrease in norepinephrine concentration was noted after digoxin was administered alone or added to captopril. These findings demonstrate that in patients with severe heart failure, the acute administration of captopril and digoxin has an independent salutary hemodynamic effect. The combination of these agents, however, has an adjunctive effect on cardiac function at rest and during exercise.

Vasodilators as first-line therapy for congestive heart failure: a comparative hemodynamic study of hydralazine, digoxin, and their combination

Although digitalis and vasodilators both enhance cardiac performance in patients with congestive heart failure, their relative efficacy is unknown. Accordingly, the acute hemodynamic effects of intravenous hydralazine (0.15 mg/kg), digoxin (1.0 mg), and the hydralazine-digoxin combination were evaluated in 14 normotensive heart failure patients at sitting rest, nine of whom were also studied during submaximal upright bicycle exercise. Hemodynamic responses at rest and exercise were similar. Cardiac output and stroke volume rose with both agents, the increase in cardiac output with hydralazine exceeding that with digoxin at rest. Left and right ventricular filling pressures declined equally. Systemic arterial mean pressure and total systemic vascular resistance fell with hydralazine, while, with digoxin, systemic arterial mean pressure increased and total systemic vascular resistance was unchanged. The hydralazine-digoxin combination produced increases in cardiac output and stroke volume that were greater than with either drug alone, and that equalled the sum of the drugs' individual effects; reductions in ventricular filling pressures were similar to the single-drug interventions. Thus, hydralazine is at least as effective as digoxin in improving cardiac function over the short term. Vasodilators may constitute an acceptable alternative to digitalis as initial therapy for congestive heart failure, except where a reduction in systemic arterial pressure is potentially deleterious. Use of combined treatment produces greater increases in cardiac output than with either drug alone, but requires risking the toxicities of two agents.

Hemodynamic effects of intravenous digoxin in patients with severe heart failure initially treated with diuretics and vasodilators

The purpose of this study was to assess the hemodynamic effects of intravenous digoxin in patients with New York Heart Association class IV heart failure, who had never previously been treated with digitalis drugs, and who were initially treated only with diuretics and systemic vasodilators to clinical end points of compensation. Eleven male patients, 5 with idiopathic and 6 with ischemic cardiomyopathy, had sinus rhythm and were hospitalized with congestive heart failure not precipitated by an acute ischemic event. All 11 patients were treated with intravenous furosemide and various vasodilators without invasive hemodynamic monitoring for a mean period of 4.3 +/- 2.1 days. This therapy resulted in subjective and objective improvement in all patients as reflected by a significant decrease in heart failure score from 9.5 +/- 2.2 to 2.7 +/- 2.3 (p less than 0.001). When compensation was achieved by clinical criteria, the patients were instrumented and hemodynamics obtained before and serially thereafter for 6 hours after the intravenous administration of digoxin given in two 0.5 mg doses 2 hours apart. In response to digoxin, cardiac index increased from 2.6 +/- 0.7 liters/min per m2 to a peak of 3.3 +/- 0.6 liters/min per m2 (p less than 0.005); left ventricular stroke work index (g X m/m2) increased from 27 +/- 16 to 43 +/- 23 (p less than 0.005) and the ejection fraction (eight patients) increased from 21 +/- 13% to 29 +/- 11% (p less than 0.04). Mean pulmonary capillary wedge pressure decreased from 24 +/- 7 to a minimum of 17 +/- 4 mm Hg (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effects of digoxin on total systemic vascular resistance in congestive heart failure due to dilated cardiomyopathy: a hemodynamic-hormonal study

The effects of the digitalis glycosides on systemic vascular resistance (SVR) in patients with congestive heart failure (CHF) are controversial. Most investigators report a reduction in total SVR, an action that has been attributed primarily to withdrawal of elevated sympathetic tone. Direct proof of this hypothesis is lacking, however, and the roles played by the renin-angiotensin-aldosterone and vasopressin systems have not been fully explored. Moreover, in several studies of patients with CHF, SVR did not decrease after the administration of digitalis. To clarify these issues, the hemodynamic and hormonal effects of digoxin were correlated in 11 normotensive men in sinus rhythm with CHF due to dilated cardiomyopathy. Patients were evaluated at rest and during submaximal exercise before and 6 hours after the intravenous infusion of 1.0 mg of digoxin (mean serum concentration 1.7 ng/ml). With digoxin therapy, heart rate, pulmonary wedge pressure and right atrial pressure declined and cardiac output increased. Although vasopressin was unchanged, both plasma norepinephrine concentrations and plasma renin activity decreased, the reduction in norepinephrine correlating with the increase in cardiac output. Despite these hemodynamic and hormonal effects, there was no change in total SVR at rest or during exercise. It is concluded that the improvement in cardiac function with digoxin in this patient group was a result of the inotropic properties of the drug, without an associated reduction in impedance. The failure of total SVR to decrease despite decreases in plasma norepinephrine levels and plasma renin activity might be explained by concomitant digitalis-induced vasoconstriction, impaired ability of arterioles to dilate in CHF, or offsetting alterations in other vasoactive hormone systems.

Evaluation of digitalis in cardiac failure

Ten patients in sinus rhythm with symptomatic cardiac failure participated in a study investigating the value of digitalis at rest and during dynamic exercise. A haemodynamic profile and left ventricular ejection fraction were measured before treatment, after intravenous ouabain, and after six weeks of maintenance treatment with digoxin. There was no significant change in the haemodynamic profile or in the left ventricular ejection fraction at rest after either glycoside. During exercise there was a significant reduction in left ventricular filling pressure from 39 +/- 3 mm Hg to 34 +/- 3 mm Hg (p less than 0.05) after ouabain and to 33 +/- 3 mm Hg (p less than 0.02) after digoxin. Cardiac index improved from 33 +/- 0.3 1/min/m2 to 4.0 +/- 0.4 l/min/m2 (p less than 0.01) after ouabain and to 3.8 +/- 0.4 l/min/m2 (p less than 0.01) after digoxin. During exercise stroke volume index and stroke work index also improved significantly with both glycosides. This was accompanied by an increase in left ventricular ejection fraction from 29 +/- 2% to 36 +/- 3% (p less than 0.05) after ouabain and digoxin. In this study both intravenous ouabain and maintenance treatment with oral digoxin exerted a modest positive inotropic effect in patients with cardiac failure in sinus rhythm. The haemodynamic benefit, however, was manifest only during exertion.

Long-term digitalis therapy improves left ventricular function in heart failure

To clarify the controversy regarding the benefits of long-term oral digoxin in the treatment of heart failure, we evaluated hemodynamics at rest and during exercise in nine patients in sinus rhythm with symptomatic heart failure. Patients were studied during long-term digoxin therapy, after withdrawal of the drug, and six hours after readministration. Upon withdrawal of digoxin, pulmonary capillary-wedge pressure increased from 21 +/- 8 to 29 +/- 10 mm Hg, and cardiac index decreased from 2.4 +/- 0.7 to 2.1 +/- 0.6 liters per minute per square meter of body-surface area, suggesting a deterioration in left ventricular function. In addition, heart rate tended to increase and stroke-work index, stroke-volume index, and radioangiographic ejection fraction decreased. Acute readministration restored the hemodynamic values to those observed during long-term digoxin therapy. The improvement in hemodynamics during long-term digoxin administration was also observed during exercise. This improvement demonstrated the value of long-term oral digoxin therapy in congestive heart failure.

Variability of hemodynamic responses to acute digitalization in chronic cardiac failure due to cardiomyopathy and coronary artery disease

Eight patients with chronic congestive heart failure (four with cardiomyopathy and four with ischemic heart disease) underwent hemodynamic studies during acute administration of digoxin, given intravenously in two 0-5 mg doses 2 hours apart. Observations were made before administration of digitalis (control period) and serially therafter for 4 hours after the first dose. Resting mean cardiac index and pulmonary arterial wedge pressure were as follows: 2.0 liters/min per m2 and 23 mm Hg (control period); 2.1 and 24 (at 1 hour); 2.0 and 23 (at 2 hours); 2.7 and 19 (at 3 hours); and 2.3 and 20 (at 4 hours). Exercise responses of mean cardiac index and pulmonary arterial wedge pressure in five patients were: 3.1 liters/min per m2 and 36 mm Hg (control period); 3.2 and 33 (at 1 hour); 3.2 and 28 (at 2 hours); 3.1 and 27 (at.3 hours); and 3.4 and 31 (at 4 hours). The pulmonary arterial wedge pressure remained elevated during exercise in all cases. Arrhythmias were seen in five patients after administration of 0.5 mg of digoxin. Hemodynamic improvement at 4 hours involving both reduced filling pressure and increased blood flow was observed in only two patients at rest and in one additional patient during exercise. Acute deterioration of cardiac function (elevated pulmonary arterial wedge pressure of decreased cardiac index) occurred 30 minutes after administration of digoxin in four patients, concomitantly with increased systemic resistance. In six patients, a peak hemodynamic effect appeared 1 to 1 1/2 hours after administration of digoxin, with partial or total loss of initial benefit by 2 and 4 hours. In previously performed studies observations have seldom exceeded 1 hour; the results of this 4 hour study suggest that, in patients with cardiomyopathy or coronary artery disease and chronic congestive heart failure, acute digitalization does not necessarily lead to consistent, marked or lasting hemodynamic improvement. Thus, current concepts of the use of digitalis is such patients may require revision.