Brian D. Lowes

Systemic hemodynamic, neurohormonal, and renal effects of a steady-state infusion of human brain natriuretic peptide in patients with hemodynamically decompensated heart failure

BACKGROUNDnHuman brain natriuretic peptide (hBNP) is a promising agent for the treatment of decompensated cardiac failure. However, the systemic hemodynamic, neurohormonal, and renal effects of hBNP have been incompletely studied in human heart failure.nnnMETHODS AND RESULTSnThe effects of a continuous 4-hour infusion of hBNP were determined in 16 decompensated heart failure patients in an invasive, randomized, double-blind, placebo-controlled study. Patients were evaluated during three 4-hour study periods: baseline, treatment (placebo [n = 4] versus hBNP 0.025 or 0.05 microgram/kg/min [n = 12]), and post-treatment. Urinary volume losses were replaced hourly to separate the vasodilatory and diuretic effects of hBNP. Two patients in the hBNP group were excluded from the analysis because of adverse events. hBNP significantly (P < .001) reduced right atrial pressure and pulmonary capillary wedge pressure by approximately 30% and 40%, respectively. hBNP also significantly lowered systemic vascular resistance from 1722 +/- 139 to 1101 +/- 83 dynes.s.cm-5 (P < .05). These unloading effects of hBNP produced a 28% increase in cardiac index (P < .05) with no change in heart rate. Compared to placebo, hBNP decreased plasma norepinephrine and aldosterone. Renal hemodynamics were unaffected by hBNP; however, most patients were resistant to its natriuretic effect.nnnCONCLUSIONSn1) The predominant hemodynamic effects of hBNP were a decrease in cardiac preload and systemic vascular resistance. 2) hBNP also improved cardiac output without increasing heart rate. 3) Plasma norepinephrine and aldosterone levels decreased during hBNP infusion. 4) hBNP is pharmacologically active and has potential in the therapy for decompensated heart failure.

The effect of diabetes on outcomes of patients with advanced heart failure in the BEST trial

OBJECTIVESnThis was a retrospective analysis to determine the effect of diabetes on outcome in patients with advanced heart failure (HF), and to determine the effect of beta-blockade in patients with HF with and without diabetes mellitus.nnnBACKGROUNDnIn chronic HF the impact on clinical outcomes and therapeutic response of the prevalent comorbid condition diabetes mellitus has not been extensively investigated.nnnMETHODSnWe assessed the impact of diabetes on prognosis and effectiveness of beta-blocker therapy with bucindolol in patients with HF enrolled in the Beta-Blocker Evaluation of Survival Trial (BEST). We conducted a retrospective analysis to examine the prognosis of patients with advanced HF with and without diabetes, and the effect of beta-blocker therapy on mortality and HF progression or myocardial infarction (MI). The database was the 2,708 patients with advanced HF (36% with diabetes and 64% without diabetes) who were randomized to the beta-blocker bucindolol or placebo in BEST and followed for mortality, hospitalization, and MI for an average of two years.nnnRESULTSnPatients with diabetes had more severe chronic HF and more coronary risk factors than patients without diabetes. Diabetes was independently associated with increased mortality in patients with ischemic cardiomyopathy (adjusted hazard ratio 1.33, 95% confidence interval 1.12 to 1.58, p = 0.001), but not in those with a nonischemic etiology (adjusted hazard ratio 0.98, 95% confidence interval 0.74 to 1.30, p = 0.89). Compared with patients without diabetes, in diabetic patients beta-blocker therapy was at least as effective in reducing death or HF hospitalizations, total hospitalizations, HF hospitalizations, and MI. Ventricular function and physiologic responses to beta-blockade were similar in patients with and without diabetes.nnnCONCLUSIONSnDiabetes worsens prognosis in patients with advanced HF, but this worsening appears to be limited to patients with ischemic cardiomyopathy. In advanced HF beta-blockade is effective in reducing major clinical end points in patients with and without diabetes.

Adora2b-elicited Per2 stabilization promotes a HIF-dependent metabolic switch crucial for myocardial adaptation to ischemia

Adenosine signaling has been implicated in cardiac adaptation to limited oxygen availability. In a wide search for adenosine receptor A2b (Adora2b)-elicited cardioadaptive responses, we identified the circadian rhythm protein period 2 (Per2) as an Adora2b target. Adora2b signaling led to Per2 stabilization during myocardial ischemia, and in this setting, Per2−/− mice had larger infarct sizes compared to wild-type mice and loss of the cardioprotection conferred by ischemic preconditioning. Metabolic studies uncovered a limited ability of ischemic hearts in Per2−/− mice to use carbohydrates for oxygen-efficient glycolysis. This impairment was caused by a failure to stabilize hypoxia-inducible factor-1α (Hif-1α). Moreover, stabilization of Per2 in the heart by exposing mice to intense light resulted in the transcriptional induction of glycolytic enzymes and Per2-dependent cardioprotection from ischemia. Together, these studies identify adenosine-elicited stabilization of Per2 in the control of HIF-dependent cardiac metabolism and ischemia tolerance and implicate Per2 stabilization as a potential new strategy for treating myocardial ischemia.

Drug Therapy in the Heart Transplant Recipient Part II: Immunosuppressive Drugs

Received March 16, 2004; revision received July 23, 2004; accepted September 30, 2004. nnPart I of this series describes the mechanisms and types of rejection and the intravenous immunosuppressive drugs commonly used for induction or antirejection therapy. In this article, we review the commonly used oral immunosuppressive drugs. Intravenous corticosteroid methylprednisolone is included in the discussion of corticosteroids. Table 1 gives trade names, pharmacology, necessary adjustments for renal or hepatic dysfunction, and dosing and general monitoring guidelines for drugs described in this section. Table 2 lists the major adverse effects of immunosuppressive drugs described in Parts I and II of this review and provides an estimate of their relative frequency. nnView this table:nnTABLE 1. Commonly Used Oral (and Intravenous) Immunosuppressive Drugs nnnnView this table:nnTABLE 2. Major Adverse Effects of Immunosuppressive Drugs nnnnSteroids, among the first immunosuppressive agents used in clinical transplantation, have remained an important component of induction, maintenance, and rejection regimens.nn### Mechanism of ActionnnGlucocorticoids are potent immunosuppressive and antiinflammatory agents (the Figure). They diffuse freely across cell membranes and bind to high-affinity cytoplasmic glucocorticoid receptors. The glucocorticoid receptor–steroid complex translocates to the nucleus, where it binds to a glucocorticoid response element within the DNA.1 The glucocorticoid receptor–steroid complex may also bind to other regulatory elements, inhibiting their binding to DNA. Both actions cause transcriptional regulation, thereby altering the expression of genes involved in immune and inflammatory response. Glucocorticoids affect the number, distribution, and function of all types of leukocytes (T and B lymphocytes, granulocytes, macrophages, and monocytes), as well as endothelial cells.2 The major effect on lymphocytes appears to be mediated by inhibition of 2 transcription factors, activator protein-1 and nuclear factor (NF) κ-B.3,4 This affects the expression of a number of genes, including those for growth factors, cytokines, CD40 ligand, GM-CSF, and adhesion and myosin heavy chain molecules.2 In nonlymphoid …

Combined oral positive inotropic and beta-blocker therapy for treatment of refractory class IV heart failure

OBJECTIVESnWe sought to assess the effects of combined oral positive inotropic and beta-blocker therapy in patients with severe heart failure.nnnBACKGROUNDnPatients with severe, class IV heart failure who receive standard medical therapy exhibit a 1-year mortality rate >50%. Moreover, such patients generally do not tolerate beta-blockade, a promising new therapy for chronic heart failure. Positive inotropes, including phosphodiesterase inhibitors, are associated with increased mortality when administered over the long term in these patients. The addition of a beta-blocker to positive inotropic therapy might attenuate this adverse effect, although long-term oral inotropic therapy might serve as a bridge to beta-blockade.nnnMETHODSnThirty patients with severe heart failure (left ventricular ejection fraction [LVEF] 17.2+/-1.2%, cardiac index 1.6+/-0.1 liter/min per m2) were treated with the combination of oral enoximone (a phosphodiesterase inhibitor) and oral metoprolol at two institutions. Enoximone was given at a dose of < or = 1 mg/kg body weight three times a day. After clinical stabilization, metoprolol was initiated at 6.25 mg twice a day and slowly titrated up to a target dose of 100 to 200 mg/day.nnnRESULTSnNinety-six percent of the patients tolerated enoximone, whereas 80% tolerated the addition of metoprolol. The mean duration of combination therapy was 9.4+/-1.8 months. The mean length of follow-up was 20.9+/-3.9 months. Of the 23 patients receiving the combination therapy, 48% were weaned off enoximone over the long term. The LVEF increased significantly, from 17.7+/-1.6% to 27.6+/-3.4% (p=0.01), whereas the New York Heart Association functional class improved from 4+/-0 to 2.8+/-0.1 (p=0.0001). The number of hospital admissions tended to decrease during therapy (p=0.06). The estimated probability of survival at 1 year was 81+/-9%. Heart transplantation was performed successfully in nine patients (30%).nnnCONCLUSIONSnCombination therapy with a positive inotrope and a beta-blocker appears to be useful in the treatment of severe, class IV heart failure. It may be used as a palliative measure when transplantation is not an option or as a bridge to heart transplantation. Further study of this form of combined therapy is warranted.

Drug therapy in the heart transplant recipient: part I: cardiac rejection and immunosuppressive drugs.

Survival after heart transplantation has improved considerably over the past 20 years. Half of all patients now live >9 years, and ≈25% live ≥17 years.1 Currently, ≈20 000 heart transplant recipients live in the United States.2 Improved longevity means prolonged immunosuppression and the concomitant use of drugs to prevent or treat the long-term complications of immunosuppressive agents, such as infection, obesity, hypertension, hyperlipidemia, renal insufficiency, diabetes, osteoporosis, gout, and malignancies. In 1989, heart transplant recipients surviving 1 year were reported to be taking 16±6 drug doses per day (prescription and nonprescription).3 In 2001, heart transplant recipients surviving an average of 76 months were taking 7 prescription drugs (range, 2 to 14), along with a number of nonprescription drugs.4 Thus, despite prolonged survival, heart transplant recipients continue to take multiple medications. With the large number of heart transplant recipients in the community and the increasing number of immunosuppressive and nonimmunosuppressive drugs used by these patients, it is important that the general cardiologist understand these drugs, their side effects, and the very real potential for drug–drug interactions. These interactions may result in adverse events caused by supratherapeutic and subtherapeutic drug concentrations. In this series, we review mechanisms and types of rejection, immunosuppressive drugs commonly used in the heart transplant recipient, common medical problems after transplantation, and clinically significant drug–drug interactions.nnA brief review of known immunologic mechanisms leading to graft rejection highlights the action of individual immunosuppressive drugs, as well as the rationale for combination therapy5–8 (Figure). The rejection of a transplanted organ is primarily a T-lymphocyte (T-cell)–mediated event, although humoral (B-cell) responses also contribute. The exception is hyperacute rejection, which occurs when preformed antibodies to human leukocyte antigens (HLA) result in an immediate and catastrophic rejection. Immune recognition of donor antigens that differ from those of …

Angiotensin II formation in the intact human heart. Predominance of the angiotensin-converting enzyme pathway.

It has been proposed that the contribution of myocardial tissue angiotensin converting enzyme (ACE) to angiotensin II (Ang II) formation in the human heart is low compared with non-ACE pathways. However, little is known about the actual in vivo contribution of these pathways to Ang II formation in the human heart. To examine angiotensin II formation in the intact human heart, we administered intracoronary 123I-labeled angiotensin I (Ang I) with and without intracoronary enalaprilat to orthotopic heart transplant recipients. The fractional conversion of Ang I to Ang II, calculated after separation of angiotensin peptides by HPLC, was 0.415 +/- 0.104 (n = 5, mean +/- SD). Enalaprilat reduced fractional conversion by 89%, to a value of 0.044 +/- 0.053 (n = 4, P = 0.002). In a separate study of explanted hearts, a newly developed in vitro Ang II-forming assay was used to examine cardiac tissue ACE activity independent of circulating components. ACE activity in solubilized left ventricular membrane preparations from failing hearts was 49.6 +/- 5.3 fmol 125I-Ang II formed per minute per milligram of protein (n = 8, +/- SE), and 35.9 +/- 4.8 fmol/min/mg from nonfailing human hearts (n = 7, P = 0.08). In the presence of 1 microM enalaprilat, ACE activity was reduced by 85%, to 7.3 +/- 1.4 fmol/min/mg in the failing group and to 4.6 +/- 1.3 fmol/min/mg in the nonfailing group (P < 0.001). We conclude that the predominant pathway for angiotensin II formation in the human heart is through ACE.

Effect of Baseline or Changes in Adrenergic Activity on Clinical Outcomes in the β-Blocker Evaluation of Survival Trial

Background—Adrenergic activation is thought to be an important determinant of outcome in subjects with chronic heart failure (CHF), but baseline or serial changes in adrenergic activity have not been previously investigated in a large patient sample treated with a powerful antiadrenergic agent. Methods and Results—Systemic venous norepinephrine was measured at baseline, 3 months, and 12 months in the &bgr;-Blocker Evaluation of Survival Trial (BEST), which compared placebo treatment with the &bgr;-blocker/sympatholytic agent bucindolol. Baseline norepinephrine level was associated with a progressive increase in rates of death or death plus CHF hospitalization that was independent of treatment group. On multivariate analysis, baseline norepinephrine was also a highly significant (P<0.001) independent predictor of death. In contrast, the relation of the change in norepinephrine at 3 months to subsequent clinical outcomes was complex and treatment group–dependent. In the placebo-treated group but not in the bucindolol-treated group, marked norepinephrine increase at 3 months was associated with increased subsequent risks of death or death plus CHF hospitalization. In the bucindolol-treated group but not in the placebo-treated group, the 1st quartile of marked norepinephrine reduction was associated with an increased mortality risk. A likelihood-based method indicated that 18% of the bucindolol group but only 1% of the placebo group were at an increased risk for death related to marked reduction in norepinephrine at 3 months. Conclusions—In BEST, a subset of patients treated with bucindolol had an increased risk of death as the result of sympatholysis, which compromised the efficacy of this third-generation &bgr;-blocker.

An alpha2C-adrenergic receptor polymorphism alters the norepinephrine-lowering effects and therapeutic response of the beta-blocker bucindolol in chronic heart failure.

Background—Adrenergic activation is an important determinant of outcomes in chronic heart failure. Adrenergic activity is regulated in part by prejunctional &agr;2C-adrenergic receptors (ARs), which exhibit genetic variation in humans. Bucindolol is a novel &bgr;-AR blocking agent that also lowers systemic norepinephrine and thus is also a sympatholytic agent. This study investigated whether &agr;2C-AR polymorphisms affect sympatholytic effects of bucindolol in patients with heart failure. Methods and Results—In the &bgr;-Blocker Evaluation of Survival Trial, adrenergic activation was estimated by systemic venous norepinephrine measured at baseline, 3 months, and 12 months posttreatment in patients treated with placebo or bucindolol. In the &bgr;-Blocker Evaluation of Survival Trial AR polymorphism substudy, DNA was collected from 1040 of the 2708 randomized patients, and &agr;2C-AR gene polymorphisms (&agr;2C Del322-325 or the wild-type counterpart) were measured by polymerase chain reaction and gel electrophoresis. Patients who were &agr;2C Del carriers (heterozygotes or homozygotes) exhibited a much greater sympatholytic response to bucindolol (decrease in norepinephrine at 3 months of 153±57 pg/mL, P=0.012 compared with placebo versus decrease of 50±13 pg/mL in &agr;2C wild type, P=0.0005 versus placebo; P=0.010 by interaction test). &agr;2C Del carriers had no evidence of a favorable survival benefit from bucindolol (mortality compared with placebo hazard ratio, 1.09; 95% CI, 0.57 to 2.08; P=0.80), whereas bucindolol-treated subjects who were wild type for the &agr;2C-AR had a 30% reduction in mortality (hazard ratio, 0.70; 95% CI, 0.51 to 0.96; P=0.025). Conclusions—In the &bgr;-Blocker Evaluation of Survival Trial AR polymorphism substudy, the norepinephrine lowering and clinical therapeutic responses to bucindolol were strongly influenced by &agr;2C receptor genotype.

Angiotensin-converting enzyme DD genotype in patients with primary pulmonary hypertension: increased frequency and association with preserved haemodynamics.

Hypothesis/introduction A polymorphic marker within the angiotensin-converting enzyme (ACE) gene has been associated with circulating and tissue ACE activity and with a variety of forms of cardiovascular disease. Since angiotensin II (Ang II) causes pulmonary vasoconstriction and vascular and myocardial remodelling, we postulated a role for the renin-angiotensin system and the ACE DD genotype in the pathophysiology of primary pulmonary hypertension (PPH) and in the right ventricular response to pressure overload in these patients. Methods and results The incidence of the ACE DD genotype was evaluated in 60 patients with severe PPH compared with two normal control populations, a group of healthy population-based controls (n=158) and subjects found suitable for cardiac organ donation (n=79). Genomic DNA extracted from peripheral leukocytes was amplified using the polymerase chain reaction to detect polymorphic markers. Haemodynamics were determined by right heart catheterisation in a subset of the PPH patients. The frequency of the ACE DD genotype was 45% in the patients with PPH, compared with 24% in the organ donors, and 28% in populationbased healthy controls (p=0.01 for chi-square test). Of the 32 PPH patients with baseline haemodynamics, 12 exhibited the ACE DD genotype and 20 were non-DD. While the mean pulmonary artery pressure and the duration of symptoms attributable to pulmonary hypertension was not different between the DD and non-DD groups, cardiac output was significantly lower (3.29±0.27 vs. 5.07±0.37 L/minute, p=0.002) and the trouvemean right atrial pressure tended to be higher (8.85±1.29 vs. 4.92±1.27 mmHg, p=0.08) in the non-DD group. The reduction in cardiac output seen in the non-DD group was not due to a difference in heart rate, but to a significant reduction in stroke volume, consistent with a decreased contractile state. In addition, non-DD patients exhibited a significantly worse functional capacity (NYHA Class 3.14±0.12 vs. 2.40±0.28, p=0.02). Conclusions 1) The ACE DD genotype is significantly increased in patients with severe PPH compared with normal controls, suggesting that certain individuals may be genetically predisposed to developing pulmonary hypertension. 2) The ACE DD genotype is associated with preserved right ventricular function in PPH patients, supporting a compensatory myocardial or inotropic role for Ang II in the pressure overloaded right ventricle.