Effects of dopaminergic agents on cardiac and renal function in normal man and in patients with congestive heart failure

Inotropes in Patients with Advanced Heart Failure: Not Only Palliative Care

Patients with advanced heart failure suffer from severe and persistent symptoms, often not responding disease-modifying drugs, a marked limitation of functional capacity and poor quality of life that can ameliorate with inotropic drugs therapy. In small studies, pulsed infusions of classical inotropes (ie, dobutamine and milrinone) are associated with improvement in hemodynamic parameters and quality of life in patients with advanced heart failure. However, because of the adverse effects of these drugs, serious safety issues have been raised. Levosimendan is a calcium-sensitizing inodilators with a triple mechanism of action, whose infusion results in hemodynamic, neurohormonal, and inflammatory cytokine improvements in patients with chronic advanced HF. In addition, levosimendan has important pleiotropic effects, including protection of myocardial, renal, and liver cells from ischemia-reperfusion injury, and anti-inflammatory and antioxidant effects; these properties possibly make levosimendan an "organ protective" inodilator. In clinical trials and real-world evidence, infusion of levosimendan at fixed intervals is safe and effective in patients with advanced HF, alleviating clinical symptoms, reducing hospitalizations, and improving the quality of life. Therefore, the use of repeated doses of levosimendan could represent the therapy of choice as a bridge to transplant/left ventricular assist device implantation or as palliative therapy in patients with advanced heart failure.

Prognostic value of heart rate variability and ventricular arrhythmias during 13-year follow-up in patients with mild to moderate heart failure

BACKGROUND

In contrast to patients with moderate to severe chronic heart failure (CHF), data regarding long-term outcome in patients with mild CHF are scarce. We examined the place of Holter monitoring to study the prognostic value of ventricular arrhythmias and heart rate variability (HRV) in patients with mild to moderate CHF during long-term follow-up.

METHODS

We studied 90 patients with mild to moderate CHF and NYHA class II who had been enrolled in the Dutch Ibopamine Multicenter Trial. At baseline their mean age was 60.5 +/- 8.0 years, left ventricular ejection fraction (LVEF) was 0.29 +/- 0.09, and 85% were males. At the start of the study, patients were only using diuretics, while digoxin, and particularly ACE inhibitors and beta-blockers were initiated later. Univariate and multivariate proportional hazard analyses were performed.

RESULTS

At baseline 80% of patients were in NYHA class II, and 20% were in class III; their mean age was 60 years, mean LVEF was 0.29, and 85% were men. During a follow-up of 13 years, 47 patients (53%) died. Cardiovascular (CV) death occurred in 39 patients, of which 28 were sudden cardiac death (SCD). For both CV death and SCD, LVEF <30% and ventricular premature beats/h (>20) were independent risk markers. Of the HRV parameters, total power (>2,500 ms(2)) was an important risk marker for CV death, but not for SCD.

CONCLUSION

The present 13-year follow-up study in 90 patients with mild to moderate CHF showed that ventricular premature beats and HRV may have important value in predicting outcome.

Renal dopamine receptors and hypertension

Dopamine has been recognized as an important modulator of central as well as peripheral physiologic functions in both humans and animals. Dopamine receptors have been identified in a number of organs and tissues, which include several regions within the central nervous system, sympathetic ganglia and postganglionic nerve terminals, various vascular beds, the heart, the gastrointestinal tract, and the kidney. The peripheral dopamine receptors influence cardiovascular and renal function by decreasing afterload and vascular resistance and promoting sodium excretion. Within the kidney, dopamine receptors are present along the nephron, with highest density on proximal tubule epithelial cells. It has been reported that there is a defective dopamine receptor, especially D(1) receptor function, in the proximal tubule of various animal models of hypertension as well as in humans with essential hypertension. Recent reports have revealed the site of and the molecular mechanisms responsible for the defect in D(1) receptors in hypertension. Moreover, recent studies have also demonstrated that the disruption of various dopamine receptor subtypes and their function produces hypertension in rodents. In this review, we present evidence that dopamine and dopamine receptors play an important role in regulating renal sodium excretion and that defective renal dopamine production and/or dopamine receptor function may contribute to the development of various forms of hypertension.

Post-treatment Dopexamine Infusions Partially Reverse Reductions in Cranial Mesenteric Blood Flow and Mucosal Oxygenation Induced by Hypoxia in Newborn Piglets

A severe hypoxic insult is known to induce dramatic reductions in newborn intestinal blood flow and is, thus, considered a vector for the development of neonatal intestinal ischemic diseases. Dopexamine (DPX) is a novel synthetic agent that has potent B2-adrenoceptor and dopaminergic activity, the clinical effects of which include an increase in cardiac output and in mesenteric blood flow. Having previously shown that infusion of DPX before hypoxia (HYP) mitigated the reduction in newborn mesenteric blood flow, we sought to define its efficacy when given after an established hypoxic insult. Ultrasonic transit time blood flow probes were placed around the ascending aorta and cranial mesenteric artery of anesthetized, mechanically ventilated 0 to 2-day-old piglets. Small bowel mucosal oxygenation was observed with a tissue oxygen monitoring system. After stabilization, animals were subjected to one of the following: HYP (FIO2 = 0.12) for 60 minutes (n = 12); DPX (5 μg/kg/min) infusion begun 10 minutes after induction of HYP/DPX (n = 11). Almost no alterations in any of the monitored variables were shown in a group (n = 5) of similarly instrumented, untreated animals. In contrast, although both hypoxic piglet groups experienced significant (P < 0.05, analysis of variance) declines from baseline cardiac output, mesenteric blood flow, and mucosal oxygenation, each of these deleterious effects was significantly (P < 0.05) blunted in the DPX-treated animals. During periods of systemic hypoxemia, the reductions in neonatal mesenteric blood flow and oxygenation can be somewhat blunted by DPX. As such, this agent may prove of clinical benefit when an infant is threatened by a hypoxic episode.

Renal dopamine receptor function in hypertension

Dopamine plays an important role in the regulation of renal sodium excretion. The synthesis of dopamine and the presence of dopamine receptor subtypes (D1A, D1B, as D1-like and D2, and D3 as D2-like) have been shown within the kidney. The activation of D1-like receptors located on the proximal tubules causes inhibition of tubular sodium reabsorption by inhibiting Na,H-exchanger and Na,K-ATPase activity. The D1-like receptors are linked to the multiple cellular signaling systems (namely, adenylyl cyclase, phospholipase C, and phospholipase A2) in the different regions of the nephron. Defective renal dopamine production and/or dopamine receptor function have been reported in human primary hypertension as well as in genetic models of animal hypertension. There may be a primary defect in D1-like receptors and an altered signaling system in the proximal tubules that lead to reduced dopamine-mediated effects on renal sodium excretion in hypertension. Recently, it has been shown in animal models that the disruption of either D1A or D3 receptors at the gene level causes hypertension in mice. Dopamine and dopamine receptor agonists also provide therapeutic potential in treatment of various cardiovascular pathological conditions, including hypertension. However, because of the poor bioavailability of the currently available compounds, the use of D1-like agonists is limited to the management of patients with severe hypertension when a rapid reduction of blood pressure is clinically indicated and in acute management of patients with heart failure. In conclusion, there is convincing evidence that dopamine and dopamine receptors play an important role in regulation of renal function, suggesting that a defective dopamine receptor/signaling system may contribute to the development and maintenance of hypertension. Further studies need to be directed toward establishing a direct correlation between defective dopamine receptor gene in the kidney and development of hypertension. Subsequently, it may be possible to use a therapeutic approach to correct the defect in dopamine receptor gene causing the hypertension.

Effect of YM435, a novel dopamine DA1 receptor agonist, in a canine model of acute congestive heart failure

1. The effects of YM435, a dopamine DA1 receptor agonist, were evaluated in a canine model of acute congestive heart failure. 2. The model was induced in open-chest anesthetized dogs by left anterior descending coronary artery ligation, volume loading, and intravenous infusion of angiotensin II. This resulted in a moderate and stable congestive heart failure characterized by reduction in cardiac output and increases in left ventricular end-diastolic pressure and total peripheral vascular resistance. 3. Intravenous infusion of YM435 (1 microgram/kg/min) significantly decreased left ventricular end-diastolic pressure, total peripheral vascular resistance and mean blood pressure and significantly increased cardiac output and renal blood flow in this model. 4. These results indicate that intravenous infusion of YM435 can improve hemodynamics and cardiac function in a canine model of acute congestive heart failure. YM435 may be a useful therapeutic agent for the treatment of congestive heart failure.

Indomethacin-induced reduction in neonatal piglet mesenteric blood flow is blunted by dopexamine

BACKGROUND

Dopexamine is a specific dopaminergic and beta2-adrenergic agonist. Using newborn piglets, we have previously shown that (1) dopexamine increases cardiac output and mesenteric blood flow; (2) indomethacin reduces mesenteric blood flow.

METHODS

Ultrasonic blood flow probes were placed around the ascending aorta, cranial mesenteric artery, and a renal artery of 0 to 2-day-old and 2-week-old piglets. Animals of each age were grouped (5 to 8 animals per group) and subjected to one of three experimental protocols: (1) 0.4 mg/kg indomethacin infusion, (2) 10 microg/kg/min dopexamine infusion begun 10 minutes before indomethacin, or (3) no treatment.

RESULTS

Control animals demonstrated no significant alterations in mesenteric blood flow. Compared with baseline, indomethacin produced significant (P< .05, analysis of variance) declines in cranial mesenteric artery blood flow in 0 to 2-day old (37.2+/-5.7 mL/min v 17.9+/-3.7 mL/min at 90 min), and 2-week-old (80.2+/-12.5 mL/min v 29.7+/-5.7 mL/min at 90 minutes) piglets. In both animal groups treated with dopexamine before indomethacin, the decreases in cranial mesenteric artery blood flow were eliminated (38.4+/-7.6 mL/min at baseline v 36.5+/-6.8 mL/min at 90 minutes in 0 to 2 day olds; 79.9+/-10.0 mL/min at baseline v 77.5+/-14.7 mL/min in 2 week olds). Indomethacin-induced declines in renal blood flow were similarly abrogated by dopexamine.

CONCLUSION

Dopexamine may prove of clinical benefit when a neonate is considered a candidate for indomethacin therapy.

Selective and nonselective dopamine receptor agonists: an innovative approach to cardiovascular disease treatment

Dopamine and a new group of selective and nonselective peripheral dopaminergic receptor effectors are being evaluated for the treatment of various cardiovascular disorders, including shock, CHF, and systemic hypertension. Dopamine, in relatively low intravenous doses, will stimulate both peripheral DA1 receptors, which mediate arterial vasodilation of different vascular beds, and the DA2 receptors, which mediate the inhibition of norepinephrine release. Ibopamine is a new oral, nonspecific peripheral dopaminergic agonist with an active metabolite (epinine) that is being evaluated in patients with CHF. Fenoldopam is a selective peripheral DA1 agonist now being developed as a parenteral treatment for hypertensive emergencies. Dopexamine is a parenteral agent that selectively activates both DA1 and beta 2 adrenergic receptors and is being evaluated in patients with CHF and in individuals with postoperative left ventricular dysfunction. A group of selective DA2 receptor agonists is being evaluated as long-term treatment for systemic hypertension.