Effects of orthotopic heart transplantation on sympathetic control mechanisms in congestive heart failure

The importance of the endothelial nitric oxide synthase on the release of 6-nitrodopamine from mouse isolated atria and ventricles and their role on chronotropism

6-nitrodopamine (6-ND) is released from rat isolated atria, where it acts as a potent positive chronotropic agent. The release of 6-ND from rat isolated atria and ventricles is significantly reduced when pre-incubated with l-NAME, and the release was not affected by tetrodotoxin pre-treatment, indicating that in the heart, the origin of 6-ND is not neurogenic. Since l-NAME inhibits all three isoforms of NO synthase, it was investigated the basal release of 6-ND from isolated atria and ventricles from nNOS-/-, iNOS-/- and eNOS-/- mice of either sex. The release of 6-ND was measured by LC-MS/MS. There were no significant differences in the 6-ND basal release from isolated atria and ventricles from male control mice, as compared to female control mice. The 6-ND release from atria obtained from eNOS-/- mice was significantly reduced when compared to atria obtained from control mice. The 6-ND release in nNOS-/- mice was not significantly different compared to control animals whereas the 6-ND release from atria obtained from iNOS-/- mice was significantly higher when compared to control group. Incubation of the isolated atria with l-NAME caused a significant decrease in the basal atrial rate of control, nNOS-/-, and iNOS-/- mice, but not in eNOS-/- mice. The results clearly indicate that eNOS is the isoform responsible for the synthesis of 6-ND in the mice isolated atria and ventricles and supports the concept that 6-ND is the major mechanism by which endogenous NO modulates heart rate.

Sympathetic vasoconstrictor activity before and after left ventricular assist device implantation in patients with end-stage heart failure

AIMS

Sympathetic overactivity, which predicts poor outcome in patients with heart failure, normalizes following cardiac transplantation. We tested the hypothesis that haemodynamic improvement following left ventricular assist device (LVAD) implantation is also associated with reductions in centrally generated sympathetic activity.

METHODS AND RESULTS

In eight patients with heart failure (two women, six men, age 44-66 years), we continuously recorded electrocardiogram, beat-to-beat finger blood pressure, respiration, and muscle sympathetic nerve activity (MSNA) before and after implantation of the continuous-flow LVAD devices HeartWare HVAD (n = 4) and HeartMate II (n = 2), and the non-continuous-flow device HeartMate 3 (n = 2). LVAD implantation increased cardiac output by 1.29 ± 0.88 L/min (P = 0.060) and mean arterial pressure by 16.2 ± 7.9 mmHg (P < 0.001), while reducing pulse pressure by 25.3 ± 9.8 mmHg (P < 0.001). LVAD implantation did not change MSNA burst frequency (-1.3 ± 7.5 bursts/min, P = 0.636), total activity (+0.62 ± 1.83 au, P = 0.369), or normalized activity (+0.63 ± 4.23, P = 0.685). MSNA burst incidence was decreased (-7.8 ± 9.3 bursts/100 heart beats, P = 0.049). However, cardiac ectopy altered MSNA bursting patterns that could be mistaken for sympatholysis.

CONCLUSION

Implantation of current design LVAD does not consistently normalize sympathetic activity in patients with end-stage heart failure despite haemodynamic improvement.

Vascular function and the role of oxidative stress in heart failure, heart transplant, and beyond

Using flow-mediated vasodilation (FMD), reactive hyperemia, and an acute oral antioxidant cocktail (AOC; vitamins C and E and α-lipoic acid), this study aimed to provide greater insight into altered vascular function and the role of oxidative stress in chronic heart failure patients with reduced ejection fraction (HFrEF) and at several time points beyond heart transplantation (HTx). A total of 61 age-matched subjects (12 healthy controls, 14 New York Heart Association class II and III HFrEF, and 35 HTx recipients [<3 years post-HTx, 5-10 years post-HTx, and >14 years post-HTx]) ingested either placebo (PL) or an AOC before FMD and reactive hyperemia testing of the brachial artery. Vascular function, as measured by FMD, was not different among the controls (6.8±1.9%), recent <3-year post-HTx group (8.1±1.2%), and the 5- to 10-year post-HTx group (5.5±1.0%). However, PL FMD was lower in the HFrEF (4.5±0.7%) and in the >14-year post-HTx group (2.9±0.8%). The AOC increased plasma ascorbate levels in all of the groups but only increased FMD in the controls (PL, 6.8±1.9%; AOC, 9.2±1.0%) and >14-year post-HTx recipients (PL, 2.9±0.8%; AOC, 4.5±1.3%). There were no differences in reactive hyperemia in any of the groups with PL or AOC. This cross-sectional study reveals that, compared with controls, vascular function is blunted in HFrEF, is similar soon after HTx, but is decreased with greater time post-HTx with free radicals implicated in this progression.

Preserved response of mitochondrial function to short-term endurance training in skeletal muscle of heart transplant recipients

OBJECTIVES

We sought to determine whether intrinsic mitochondrial function and regulation were altered in heart transplant recipients (HTRs) and to investigate the response of mitochondrial function to six-week endurance training in these patients.

BACKGROUND

Despite the normalization of central oxygen transport during exercise, HTRs are still characterized by limited exercise capacity, which is thought to result from skeletal muscle metabolic abnormalities.

METHODS

Twenty HTRS agreed to have vastus lateralis biopsies and exercise testing: before and after training for 12 of them and before and after the same control period for eight subjects unwilling to train. Mitochondrial respiration was evaluated on saponin-permeabilized muscle fibers in the absence or presence (maximum respiration rate [V(max)]) of saturating adenosine diphosphate.

RESULTS

Mitochondrial function was preserved at the level of sedentary subjects in untrained HTRs, although they showed 28 +/- 5% functional aerobic impairment (FAI). After training, V(max), citrate synthase, cytochrome c oxidase, and mitochondrial creatine kinase (CK) activities were significantly increased by 48%, 40%, 67%, and 53%, respectively (p < 0.05), whereas FAI decreased to 12 +/- 5% (p < 0.01). The control of mitochondrial respiration by creatine and mitochondrial CK was also improved (p < 0.01), suggesting that phosphocreatine synthesis and transfer by the mitochondrial CK become coupled to oxidative phosphorylation, as shown in trained, healthy subjects.

CONCLUSIONS

In HTRs, the mitochondrial properties of skeletal muscle were preserved and responded well to training, reaching values of physically active, healthy subjects. This suggests that, in HTRs, immunosuppressive drugs do not alter the intrinsic muscle oxidative capacities and that the patients' physical handicap results from nonmitochondrial mechanisms.

Autonomic function in elderly patients with chronic heart failure

AIMS

Autonomic function (AF) is attenuated by heart failure (HF). Reports have been based on studies of young patients with systolic heart failure (SHF). However, HF is a disease of older patients who are more likely to have diastolic heart failure (DHF). We investigated whether age alters AF in elderly HF patients and whether the haemodynamic type of HF influences AF.

METHOD AND RESULTS

Thirty-six elderly HF (Framingham criteria) patients (11 with SHF, 25 with DHF) and 21 matched healthy subjects underwent simple bedside AF tests. Compared with the reference values for healthy adults, the mean E:I ratios and the median 30:15 ratios standing were all essentially normal. The median 30:15 ratios tilt and the mean Valsalva ratios were all significantly below the reference value (P for all cases <<0.050). Comparing three groups, there were no significant differences for mean E:I ratio (P=0.111), 30:15 tilt (P=0.619) and 30:15 standing (P=0.167), whereas there were significant differences for the mean Valsalva ratios (P=0.001). The mean Valsalva ratio of the SHF patients was significantly lower than that for the DHF patients (P<0.001) which in turn was significantly lower than the result of the healthy subjects (P<0.001).

CONCLUSION

There is an age-related impairment in AF with further impairment occurring in patients with HF. However, the severity of autonomic dysfunction is less in patients with DHF compared with patients with SHF.

Chronotropic effects of nitric oxide in the denervated human heart

Nitric oxide synthase is expressed in the sino-atrial node and animal data suggests a direct role for nitric oxide on pacemaker activity. Study of this mechanism in intact humans is complicated by both reflex and direct effects of nitric oxide on cardiac autonomic control. Thus, we have studied the direct effects of nitric oxide on heart rate in human cardiac transplant recipients who possess a denervated donor heart. In nine patients, the chronotropic effects of systemic injection of the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) (3 mg kg(-1)) or increasing bolus doses of the nitric oxide donor, sodium nitroprusside (SNP), were studied. Injection of L-NMMA increased mean arterial pressure by 17 +/- 2 mmHg (mean +/- S.E.M.; P < 0.001) and also had a significant negative chronotropic effect, lengthening the R-R interval by 54 +/- 8 ms (P < 0.001). This bradycardia was not reflex in origin since injection of the non-NO-dependent vasoconstrictor, phenylephrine (100 microg) achieved a similar rise in mean arterial pressure (18 +/- 3 mmHg; P < 0.001) but failed to change R-R interval duration (Delta R-R = -3 +/- 4 ms). Furthermore, no change in levels of circulating adrenaline was observed with L-NMMA. Conversely, injection of sodium nitroprusside resulted in a positive chronotropic effect with a dose-dependent shortening of R-R interval duration, peak Delta R-R = -25 +/- 8 ms with 130 microg (P < 0.01). These findings indicate that nitric oxide exerts a tonic, direct, positive chronotropic influence on the denervated human heart. This is consistent with the results of animal experiments showing that nitric oxide exerts a facilitatory influence on pacemaking currents in the sino-atrial node.

Skeletal muscle characteristics, muscle strength and thigh muscle area in patients before and after cardiac transplantation

BACKGROUND

Patients with chronic heart failure demonstrate several skeletal muscle abnormalities. The underlying mechanisms are unclear. After cardiac transplantation, cardiac function is restored, but exercise capacity is still impaired.

AIM

To evaluate the influence of cardiac transplantation on skeletal muscle fibre composition, fibre area and capillarization as well as muscle enzymes, lactate, thigh muscle area and strength.

METHODS

Ten patients were longitudinally investigated before, 1-3 and 6-9 months after transplantation. Ten healthy individuals served as controls. A biopsy from the lateral vastus muscle was obtained and the thigh muscle area was measured with computed tomography. Muscle strength in the knee extensors and exercise capacity were also evaluated.

RESULTS

Muscle lactate was elevated in patients vs. controls (3.6+/-3.0 vs. 1.5+/-0.7 mmol/kg wet wt., P=0.037), and decreased to normal (1.4+/-0.3 mmol/kg wet wt., P=0.038) after transplantation. Citrate synthase activity was decreased in patients (5.6+/-1.5 micromol/g wet wt./min) vs. controls (8.1+/-1.6 micromol/g wet wt./min, P=0.0018), and did not change post transplantation. Patients had decreased number of capillaries in contact with each fibre vs. controls (2.6+/-0.5 vs. 3.5+/-1.0, P=0.039) which persisted post transplantation. Exercise capacity increased after transplantation (74+/-22 vs. 118+/-26 W, P=0.0002), whereas muscle strength did not improve significantly.

CONCLUSION

The persisting intrinsic abnormalities in skeletal muscle after cardiac transplantation may contribute to the impaired exercise capacity observed in cardiac transplant recipients.

Safety profile and hemodynamic responses to beta-adrenergic stimulation by dobutamine in heart transplant patients

STUDY OBJECTIVE

Dobutamine stress echocardiography (DSE) has been used as a screening tool for coronary artery disease after heart transplantation and in the identification of patients at risk for development of cardiac events. However, the safety profile of high-dose dobutamine in heart transplant patients has not been systematically examined. Accordingly, we studied the safety profile and hemodynamic responses to escalating doses of dobutamine to determine the influence of denervation.

DESIGN

We assessed the hemodynamic responses, heart rate (HR), and arterial BP indexes (mean arterial pressure, systolic BP [SBP], diastolic BP [DBP], and pulse pressure) to dobutamine in 87 heart transplant patients ([mean +/- SD] age, 51 +/- 1 years) and compared the results with 97 nontransplant patients (age, 63.0 +/- 1 years) who served as innervated control subjects.

MEASUREMENTS AND RESULTS

The baseline HR (84 +/- 2 vs 69 +/- 1 beats/minute, respectively; p < 0.001) and peak HR response (144 +/- 2 vs 117 +/- 2 beats/minute, respectively; p < 0.001) were significantly higher in heart transplant patients than in the nontransplant patients. SBP was lower in heart transplant patients than in nontransplant patients at baseline (131 +/- 2 vs 138 +/- 2 mm Hg, respectively; p < 0.02) and at peak (150 +/- 3 vs 158 +/- 3 mm Hg, respectively; p < 0.03). However, baseline DBP was higher in transplant patients than in nontransplant patients (86 +/- 1 vs 77 +/- 1 mm Hg, respectively; p < 0.001). The decrease in DBP was similar in both groups (15 mm Hg). The dose-response curve for HR was shifted leftward in heart transplant patients. Heart transplant patients attained a higher absolute HR at each infusion stage and higher rates of increase, but the decrease in DBP was not significantly different in the two groups.

CONCLUSIONS

These results show that there is augmented chronotropic response and expected decline in DBP in response to dobutamine infusion in heart transplant patients. This increase in myocardial oxygen demand and a decrease in coronary perfusion pressure may be important mechanisms in the development of ischemic abnormalities that are detectable as regional dysynergy on echocardiography.

Exercise blod flow and microvascualr distensibility in skeletal muscle normalize after heart transplantation

This study investigated the effect of heart transplantation (HTX) on reduced exercise blood flow and microvascular stiffness in patients with congestive heart failure (CHF). Skeletal muscle blood flow (SMBF) during graded maximal supine bicycle exercise and microvascular distensibility (i.e., stiffness) were measured in musculus tibialis anterior by the isotope washout method. Measurements were performed in a cross-sectional study with 31 CHF patients and 28 patients, mean 9 months after HTX, and in a longitudinal study in 12 CHF patients before, 3 months, and 14 months after HTX, and in 31 healthy controls. Maximal SMBF: In the cross-sectional study, maximal SMBF was reduced in severe CHF patients (3.6 +/- 2.5 mL (100 g min)(-1)) and increased after HTX (7.7 +/- 4.8; p < 0.01 versus controls (11 +/- 4.1). Maximal SMBF was reduced in CHF patients (5.8 +/- 4.0) and reversed to normalization 3 months after HTX (10.3 +/- 4.4) in the longitudinal study. Microvascular distensibility: The distensibility was reduced (severe CHF, 12 +/- 8%; moderate CHF, 23 +/- 14%) in the cross-sectional study and increased after HTX towards normalization (38 +/-20%; controls: 44 +/- 17). In the longitudinal study, distensibility in CHF patients (14 +/- 6%) increased gradually to 32 +/- 12% (p < 0.005) at 3 months and normalized 14 months after HTX (46 +/- 17%). HTX gradually reversed the reduced SMBF and microvascular distensibility in CHF patients towards normalization.

Effects of the angiotensin II antagonist losartan on endothelin-1 and norepinephrine plasma levels during cold pressor test in patients with chronic heart failure

We evaluate the acute hemodynamic and neurohormonal effects of losartan in 15 patients with symptomatic chronic heart failure (CHF), mean age 72+/-8 years, which were classified in two subgroups: (A) Patients with left ventricular ejection fraction (LVEF)< or =0.35 (n = 7); (B) subjects with LVEF>0.35 (n = 8). Sympathetic reactivity (blood pressure, heart rate and plasma norepinephrine) and plasma endothelin-1 (ET-1) were evaluated by a cold pressor test (CPT). Single doses of losartan (50 mg p.o.) lowered delta DBP in both subgroups (A, 8+/-9 to 0+/-5 mm Hg, P<0.05; B, 10+/-6 to 3+/-4 mm Hg, P<0.05) and attenuated the rise of HR in patients with mild (4+/-6 to -1+/-2 bpm, P<0.05) but not with severe (4+/-5 to 2+/-5 bpm, n.s.) impairment of left ventricular function. Losartan blunted the response (delta) of PNE during CPT (A, 142+/-131 to 10+/-74 pg/ml, P<0.05; B, 129+/-72 to 1+/-144 pg/ml, P<0.01). A significant rise in plasma ET-1 was observed during CPT in patients from subgroup B (0.64+/-0.40 to 0.81+/-0.40 fmol/ml, P<0.05) but not in patients with LVEF< or =0.35 (1.79+/-0.44 to 1.51+/-0.66 fmol/ml, n.s.). Losartan attenuated the rise in ET-1 during CPT in patients with LVEF>0.35 (delta ET-1 0.17+/-0.86 to 0.03+/-0.11 fmol/ml, P<0.05), with no significant changes in subgroup A. Acute effects of losartan were characterized by a more favorable hemodynamic and neurohumoral response in patients with chronic heart failure and preserved systolic ventricular function related to subjects with lower ejection fractions.

Nitric oxide donors can increase heart rate independent of autonomic activation

Administration of nitric oxide (NO) donors in vivo is accompanied by a baroreflex-mediated increase in heart rate (HR). In vitro, however, NO donors can increase HR directly by stimulating a pathway that involves NO, cGMP, and the hyperpolarization-activated current (I(f)). The aim of this study was to assess the functional significance of this pathway in vivo by testing whether NO donors can increase HR in the anesthetized rabbit independent of the autonomic nervous system. New Zealand White rabbits were vagotomized, cardiac sympathectomized, and treated with propranolol (0.3 mg/kg iv). The NO donor molsidomine (0.2 mg/kg iv) caused a progressive increase (Delta) in HR (DeltaHR, 14 +/- 3 beats/min; P < 0.01). This effect was significantly reduced by the I(f) blocker ZD-7288 (0.2 mg/kg iv; DeltaHR, 2 +/- 3 beats/min; P = not significant). Similar results were seen with sodium nitroprusside. The positive chronotropic effect of sodium nitroprusside (50 microM) was confirmed in the isolated working rabbit heart preparation (DeltaHR, 17 +/- 3 beats/min; P < 0.01). In conclusion, NO donors exert a small, but significant, positive chronotropic effect in vivo that is independent of the autonomic nervous system. These results are also consistent with data in sinoatrial node cells that show that NO donors increase HR by stimulating I(f).

Effect of heart transplantation on impaired peripheral microvascular perfusion and reactivity in congestive heart failure

Whether reduced peripheral blood flow in congestive heart failure is reversed after heart transplantation, has not been closely examined. We therefore studied skin microvascular resting perfusion and reactivity in patients pre- and postoperatively. Resting digital skin perfusion, together with the responses to cold pressor test, postocclusive reactive hyperemia and direct skin heating were examined with laser Doppler perfusion measurements. We examined 28 patients with congestive heart failure and 14 of these patients after heart transplantation and compared them to 13 healthy controls. Measurements were performed within 3 months preoperatively and 12 days, 1, 2, 3 and 6 months postoperatively. Patients with congestive heart failure had significantly lower resting perfusion levels than controls and demonstrated attenuated responses to both stimuli of vasodilation (all P<0.01). While peak hyperemic responses improved significantly after transplantation, postocclusive area under the hyperemic curve decreased further, and none of these variables were normalized after 6 months. In contrast, minimal perfusion during cold pressor test increased from a significantly lower level in the patients with congestive heart failure (P<0.05), to a level similar to that of the controls within 12 days postoperatively. Thus, skin microvascular perfusion and reactivity improve, but are not normalized within 6 months of transplantation. Both pre- and postoperative factors may be involved in maintaining a dysfunction of the peripheral microcirculation, which may contribute to exercise intolerance and hypertension in heart transplant recipients.

Percutaneous transluminal mitral valvuloplasty normalizes baroreflex sensitivity and sympathetic activity in patients with mitral stenosis

BACKGROUND

In patients with mitral stenosis, reduced cardiac output or altered pulmonary hemodynamics may increase sympathetic nerve activity. However, the magnitude of the increase in sympathetic activity in such patients and the effect of valvuloplasty on this activity are unknown.

METHODS AND RESULTS

We microneurographically measured muscle sympathetic nerve activity before and after mitral valvuloplasty in 10 patients (mean+/-SEM age, 48+/-2 years) with mitral stenosis and in 10 healthy volunteers (47+/-4 years); hemodynamic variables were also measured. Baroreflex sensitivity was assessed on the basis of the ratio of the change in heart rate or muscle sympathetic activity to the change in mean arterial pressure during intravenous infusion of sodium nitroprusside or phenylephrine. At baseline, muscle sympathetic activity was significantly higher in the patients with mitral stenosis than in the control subjects (42.1+/-3.2 versus 26.1+/-3.7 bursts/min, P<.05). However, there was no significant difference between the groups in sympathetic activity at 1 week after valvuloplasty. The reduction in sympathetic activity after valvuloplasty was maintained for > or = 6 months and correlated with the increase in cardiac index (r=.74, P<.05). Baroreflex sensitivity was significantly lower in the patients than in the control subjects, but after valvuloplasty there was no significant difference in baroreflex sensitivity between the groups.

CONCLUSIONS

Sympathetic activity is increased in patients with mitral stenosis. Mitral valvuloplasty in such patients results in early and long-lasting normalization of sympathetic nerve activity, possibly because of an improvement in arterial baroreflex sensitivity.

Function of the transplanted heart: unique physiology and therapeutic implications

Orthotopic heart transplantation has become an established treatment for selected patients with refractory heart failure. Long-term survival rates are superior to those resulting from other forms of therapy for that patient population. In addition, an improved quality of life has been reported by many patients. However, despite these encouraging results, the transplanted heart does not provide the recipient with normal cardiac function. Cardiac physiology after heart transplantation is unique. Resting hemodynamics differ significantly, acutely and chronically, from those seen in healthy subjects. In addition, neural mechanisms undergo changes as a result of surgical denervation. Afferent control mechanisms and efferent responses both are altered, leading to important clinical abnormalities. Examples include altered cardiovascular responses to exercise, altered cardiac electrophysiology, and altered responses to cardiac pharmacologic agents. An improved understanding of the changes in cardiac physiology, which occur after heart transplant, may allow the care of these patients to be optimized.

Nitric oxide can increase heart rate by stimulating the hyperpolarization-activated inward current, I(f)

We investigated the chronotropic effect of increasing concentrations of sodium nitroprusside (SNP, n = 8) or 3-morpholinosydnonimine (SIN-1, n = 6) in isolated guinea pig spontaneously beating sinoatrial node/atrial preparations. Low concentrations of NO donors (nanomolar to micromolar) gradually increased the beating rate, whereas high (millimolar) concentrations decreased it. The increase in rate was (1) enhanced by superoxide dismutase (50 to 100 U/mL, n = 6), (2) prevented by the guanylyl cyclase inhibitors 6-anilino-5,8-quinolinedione (5 mumol/L, n = 6) or 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (10 mumol/L, n = 6), and (3) mimicked by 8-bromo-cGMP (n = 6) with no additional positive chronotropic effect of SIN-1 (n = 5). The response to 10 mumol/L SNP (n = 28) or 50 mumol/L SIN-1 (n = 16) was unaffected by IcaL antagonism with nifedipine (0.2 mumol/L) but was abolished after blockade of the hyperpolarization-activated inward current (I(f)) by Cs+ (2 mmol/L) or 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino)pyrimidinium chloride (1 mumol/L). The effect on I(f) was further evaluated in rabbit isolated patch-clamped sinoatrial node cells (n = 21), where we found that 5 mumol/L SNP or SIN-1 caused a reversible Cs(+)-sensitive increase in this current (+130% at -70 mV and +250% at -100 mV). In conclusion, NO donors can affect pacemaker activity in a concentration-dependent biphasic fashion. Our results indicate that the increase in beating rate is due to stimulation of I(f) via the NO-cGMP pathway. This may contribute to the sinus tachycardia in pathological conditions associated with an increase in myocardial production of NO.

Rapid fall in sympathetic nerve hyperactivity in patients with heart failure after cardiac transplantation

BACKGROUND

Severe heart failure is associated with an intense sympathetic nerve hyperactivity. After cardiac transplantation, neurochemical studies have indicated a normalization of sympathetic outflow. Intraneural recordings have, however, yielded varying results; both a normalization and a remaining hyperactivity have been obtained in cardiac transplant recipients, the latter being attributed to cyclosporine treatment.

METHODS AND RESULTS

To circumvent the methodologic variation associated with different patient groups in cross-sectional studies, a longitudinal study design was employed in this study. Intraneural recordings of muscle sympathetic nerve activity in 21 heart failure patients were performed before, and repeatedly during the first year after, heart transplantation. Before surgery, muscle sympathetic nerve activity was augmented in all patients (78 +/- 4 bursts/min, 90 +/- 2 bursts/100 heartbeats). Both muscle sympathetic nerve activity burst frequency (burst/minute) and burst incidence (bursts/100 heartbeats) decreased rapidly following surgery. One month after surgery, burst frequency was reduced by 35% (51 +/- 5 bursts/min P < .05), whereas burst incidence decreased by 32% (61 +/- 5 bursts/100 heartbeats, P < .05). This decrease remained unchanged up to 1 year after surgery. The fall in posttransplant muscle sympathetic nerve activity was similar in transplant recipients who developed hypertension during the course of the study (n = 12) and those who remained normotensive (n = 9).

CONCLUSIONS

The sympathoexcitation recorded in patients with heart failure was rapidly and substantially reduced after cardiac transplantation despite cyclosporine treatment, most likely reflecting improved central and peripheral hemodynamics.

Endothelial nitric oxide pathway function in the peripheral vasculature of patients with heart failure

Many studies have investigated the pathophysiologic contributions of abnormalities in the endothelial nitric oxide pathway to the heightened vasoconstrictor tone that is characteristic of the clinical syndrome of heart failure. The most consistent abnormality is a reduced vasodilator response to muscarinic stimulation with either acetylcholine or methacholine, a finding which has been identified in several animal models of heart failure as well as in forearm and leg resistance vessels in patients with heart failure. More recent studies with desmopressin, a vasopressin 2 receptor agonist that stimulates nitric oxide production independent of the muscarinic receptor, have demonstrated that the abnormality in endothelium-dependent vasodilation was not limited to the muscarinic pathway. At present, the mechanisms of the defect in the endothelial nitric oxide pathway are unknown. But, they appear not to be directly related to sympathetic stimulation. Finally, studies using transplant recipients have demonstrated that this defect is reversible. In addition, a pilot study has demonstrated that supplemental oral L-arginine, the precursor for nitric oxide, has beneficial effects on forearm blood flow responses to exercise, arterial compliance nad functional status as assessed by increased distances during a 6-minute walk test and lower scores on the Living with Heart Failure Questionnaire. These studies suggest that the endothelial nitric oxide pathway may be a target for therapeutic interventions in heart failure.

Circulating noradrenaline and beta-adrenergic receptors in children with congestive heart failure

This study was designed to investigate changes in plasma catecholamine concentrations and the number of beta-adrenoceptors (beta-AR) of circulating lymphocyte in 94 noncyanotic congenital heart patients. In 43 patients with congestive heart failure, beta-AR density was significantly lower (p < 0.001) and plasma noradrenergic levels were significantly higher (p < 0.001) compared with corresponding values in 51 patients without heart failure. A significant negative correlation between lymphocyte beta-AR density and plasma noradrenergic levels was observed (r = -0.61, p < 0.001). The degree of left-to-right shunt and pulmonary pressure was correlated directly with noradrenaline level and inversely with lymphocyte beta-AR density. Both plasma noradrenaline level and lymphocyte beta-AR density return to normal in children with heart failure after surgical repair. Our results support the idea that changes in noradrenaline level and lymphocyte beta-adrenoceptor density occur concurrently with the presence and severity of heart failure in children.

Outcome predictors of ultrafiltration in patients with refractory congestive heart failure and renal failure

This study is an attempt to identify predictors of outcome from the use of ultrafiltration (UF) in patients with refractory congestive heart failure (CHF) and renal failure. The authors studied 30 patients in NYHA functional class IV in whom UF was utilized in the management of refractory CHF. Patients were retrospectively divided into two groups according to their outcome. Group A included 12 patients who improved and survived hospital admission, and group B included 18 patients who did not respond and died shortly after UF. Clinical, hemodynamic, and laboratory data before UF were fairly comparable between both groups. Renal function and hemodynamic parameters were compared and analyzed within the same group and between both groups before and after UF. The mean age in group A was sixty-three +/- thirteen years while in group B it was seventy +/- eleven years (P < 0.005). A mean of 9.6 liters of fluid were removed from group A and 3.2 liters from group B (P < 0.001). Group A showed greater reduction in the mean values of right atrial pressure (P < 0.005) and pulmonary capillary wedge pressure (P < 0.05) after UF. Additionally, group A showed a significant decrease in their blood urea nitrogen (P < 0.05) and serum creatinine values (P < 0.05), in contradistinction to group B patients who showed a major increase in those values after UF. There was no significant change in the mean values of cardiac index, systemic vascular resistance, and pulmonary vascular resistance after UF. These findings suggest that younger age groups, greater fluid removal, as well as significant decreases in blood urea nitrogen, serum creatinine, and right atrial and pulmonary wedge pressures after UF, are associated with favorable outcome. Conversely, older age groups, less fluid removal, and rising blood urea nitrogen and serum creatinine levels after UF were associated with poor outcome.

Effects of orthotopic cardiac transplantation on structural microangiopathy and abnormal hemodynamics in idiopathic dilated cardiomyopathy

To examine whether cardiac transplantation would reverse morphologic and hemodynamic changes in peripheral circulation in idiopathic dilated cardiomyopathy, the structure of terminal arterioles and minimal vascular resistance were measured in skin at the dorsum of the foot in the same 14 patients before and 80 +/- 21 (mean +/- SD) days and 387 +/- 46 days after transplantation. The results were compared with data from a group of 16 healthy subjects. Blood flow was measured by the local technetium-99m pertechnetate washout method in a vascular bed relaxed with histamine. Structural microangiopathy (enhanced thickening of the basement membranes) in the arterioles was disclosed in skin biopsies in 11 of 14 patients before transplant, but in none of the 16 control subjects (p < 0.002). These abnormalities were unchanged 80 days after cardiac transplantation. However, arteriolar wall thickening was significantly reduced over the 1-year period after transplantation (p < 0.05), but this was not complete. Transplantation also led to a significant delayed decrease in minimal vascular resistance: before transplantation, 10.1 +/- 3.2 mm Hg.ml-1.100 g.min (mean +/- SD); 80 days after transplantation, 9.3 +/- 3.1 mm Hg.ml-1.100 g.min (p = NS), and 1 year after transplantation 7.6 +/- 2.4 mm Hg.ml-1 100 g.min (p < 0.01). Minimal vascular resistance before and 80 days after transplantation was significantly increased compared with that in healthy control subjects (6.3 +/- 1.7 mm Hg.ml-1 100g.min [p < 0.0003 and p < 0.003, respectively]). However, 1 year after transplantation, minimal vascular resistance was reduced to comparable levels when compared with that in control subjects (p = NS). These results indicate that structural microangiopathy and minimal vascular resistance in skin are improved slowly and gradually within the first year after orthotopic cardiac transplantation in patients with idiopathic dilated cardiomyopathy, however, the remodeling of histopathology is not accompanied by complete normalization.

Neurohormonal activation and exercise function in patients with severe heart failure and patients with left ventricular assist system. A comparative study

OBJECTIVES

The aim of this study was to evaluate the effects of implantation of a left ventricular assist system (LVAS) on the neurohormonal status, exercise capacity and symptomatic state in patients with severe congestive heart failure (CHF).

BACKGROUND

Severe CHF is characterized by decreased exercise tolerance and activation of several neurohormonal systems.

METHODS

Parameters of neurohormonal activation and exercise capacity in patients with LVAS (n = 7) were compared with those in groups of New York Heart Association (NYHA) class 3 (n = 121) and class 4 (n = 81) patients. Plasma levels of norepinephrine (NE), plasma renin activity (PRA), and atrial natriuretic peptide (ANP) and maximal and submaximal exercise capacities were measured monthly in LVAS patients and compared with results in CHF patients.

RESULTS

Plasma NE and PRA levels were significantly lower in LVAS patients than in NYHA class 4 patients, and plasma ANP levels in LVAS patients were significantly lower than those in NYHA class 3 and 4 patients. The distance walked during submaximal exercise testing and peak oxygen consumption during maximal exercise testing were similar for the LVAS and NYHA class 3 patients. The class 4 patients were unable to exercise.

CONCLUSIONS

We conclude that the LVAS lessens the neurohormonal activation and exercise intolerance characteristic of the CHF state and that the exercise capacity early after LVAS (< 4 months) is similar to that observed in NYHA class 3 patients.

Effect of beta blockade on the neurohumoral and cardiopulmonary response to dynamic exercise in cardiac transplant recipients

OBJECTIVE

To determine the effects of a small dose of beta blocker on neurohumoral and cardiopulmonary responses after cardiac transplantation.

BACKGROUND

Cardiac transplant recipients have a reduced exercise capacity and abnormal cardiovascular responses to exercise. The sympathoadrenal response to exercise has been shown to be abnormal with high venous noradrenaline. The effect of beta blockade on these neurohumoral mechanisms has not been defined.

METHODS

10 non-rejecting cardiac transplant recipients were studied. Patients carried out graded exercise to a symptom limited maximum. Blood samples were taken during exercise. Concentrations of noradrenaline, adrenaline, and atrial natriuretic peptide and plasma renin activity were measured. The next day, the exercise and sampling procedure were repeated after an oral dose of propranolol (40 mg).

RESULTS

Patients tolerated exercise poorly after beta blockade, which was reflected in the maximum workload reached. Heart rate and blood pressure were significantly higher at rest and during exercise before beta blockade. Although there was no significant difference when resting, mean (SEM) noradrenaline concentrations during peak exercise were higher after beta blockade (16.2 (2) v 23.6 (2.9) nmol/l, p = 0.001). Adrenaline concentrations at peak exercise were also greater after beta blockade (0.89 (0.31) v 1.18 (0.38) nmol/l, p = 0.055). Atrial natriuretic peptide concentrations tended to be higher after beta blockade (118.75 (50.2) v 169.79 (39.3) pmol/l, p = 0.36). There was no significant change in plasma renin activity.

CONCLUSIONS

A small oral dose of a competitive beta blocker such as propranolol has an adverse effect on exercise tolerance and cardiovascular response to exercise in cardiac transplant recipients. There are also increased concentrations of circulating noradrenaline and therefore, sympathetic activity during exercise. beta blockers should be used with caution in cardiac transplant recipients.

Progression of venoconstriction in patients after heart transplantation during exercise

Changes of both central hemodynamics and peripheral circulation in non-exercising muscle were investigated in 17 patients after successful orthotopic heart transplantation during moderate supine isotonic leg-exercise. Changes of peripheral circulation were measured in 14 healthy controls. The cardiac output rose from 5.71 to 9.45 l/min, the right atrial pressure from 3.5 to 12 mmHg, mean pulmonary arterial pressure from 17.4 to 36.9 mmHg, and pulmonary capillary wedger pressure from 9.5 to 23.5 mmHg. Venoconstriction, already present in the rest in patients after heart transplantation, further increased during the exercise (venous compliance lowered from 0.0454 to 0.0309 ml/mmHg). In controls no changes were observed (venous compliance being 0.0833 at rest and 0.0839 ml/mmHg during exercise). Negative correlation was found between an increase in pulmonary arterial pressure and a decrease in venous compliance. The authors hypothesise that venoconstriction could serve to increase of cardiac output via Frank-Starling mechanisms in patients after heart transplantation. Forearm blood flow during the exercise decreased (from 3.4 to 2.0 ml/100 ml/min), while local peripheral resistance rose (from 35.9 to 78.8 units) in patients after heart transplantation. These changes were not observed in controls.

Effect of angiotensin converting enzyme inhibition on plasma endothelin in congestive heart failure

The influence of angiotensin converting enzyme inhibitor therapy on elevated plasma endothelin concentrations in chronic heart failure was investigated by measuring plasma endothelin immunoreactivity in 22 patients with severe but stable chronic heart failure before and after 16 weeks of therapy with quinapril (n = 12) or captopril (n = 10). Plasma endothelin immunoreactivity in the patients (10.2 +/- 34 pg/ml) was significantly higher than a control group (5.9 +/- 1.8 pg/ml). Quinapril improved symptoms and haemodynamics but did not affect plasma endothelin immunoreactivity (11.9 +/- 2.9 pg/ml at baseline and 12.3 +/- 3.4 pg/ml after 16 weeks of quinapril). Captopril also had no effect on endothelin levels (8.1 +/- 2.9 at baseline and 8.1 +/- 3.8 pg/ml after 16 weeks of captopril). The vasodilatory effects of angiotensin converting enzyme inhibitors in heart failure are not mediated by, or associated with, changes in plasma endothelin immunoreactivity.

Sympathetic dysfunction in heart failure

CHF is a common, complex and life-threatening clinical syndrome. It is widely accepted that enhanced peripheral vascular tone plays a major role in the pathophysiology of CHF. Increased activity of the sympathetic nervous system is one of the most important factors responsible for the increased afterload in CHF. This increase in sympathetic activity occurs early in the course of development of CHF. Efferent sympathetic activity is distributed in a non-uniform way in CHF, with significant increases to the heart and kidney but normal activity to some other organs such as the lung. Increased renal sympathetic activity contributes significantly to altered neural haemodynamics, sodium and water retention, and modulation of the actions of other vasoactive hormones. The regional alteration in sympathetic activity may be largely responsible for the changes in resting regional blood flow to different organs in CHF and the maldistribution of blood flow that occurs during the stress of exercise. Disordered function of cardiovascular reflexes is observed in CHF and may contribute to disordered sympathetic function. In CHF there are significant interactions between the sympathetic nervous system and other humoral systems such as the renin-angiotensin system, AVP, ANP, endothelin and renal DA. The various drugs used in the treatment of CHF have different effects on sympathetic activity: digitalis and ACE inhibitors tend to suppress activity while diuretics may have the opposite effect. Following cardiac transplantation, there is a prompt return of sympathetic function towards normal, although the heart may remain significantly denervated for a long time, with gradual reinnervation. Cyclosporin therapy tends to increase sympathetic activity and this may contribute to post-transplant hypertension.

Isolated ultrafiltration in moderate congestive heart failure

OBJECTIVES

The aim of this study was to evaluate whether ultrafiltration is beneficial in patients with moderate congestive heart failure.

BACKGROUND

Ultrafiltration is beneficial in patients with severe congestive heart failure.

METHODS

We studied 36 patients in New York Heart Association functional classes II and III in stable clinical condition. Eighteen patients (group A) were randomly selected and underwent a single session of ultrafiltration (venovenous bypass, mean [+/- SEM] ultrafiltrate 1,880 +/- 174 ml, approximately 600 ml/h) and 18 (group B) served as control subjects.

RESULTS

Two patients in group A and three in group B did not complete the 6-month follow-up study. In group A, soon after ultrafiltration there were significant reductions in right atrial pressure (from 8 +/- 1 to 3.4 +/- 0.7 mm Hg, pulmonary wedge pressure (from 18 +/- 2.5 to 10 +/- 1.9 mm Hg) and cardiac index (from 2.8 +/- 0.2 to 2.3 +/- 0.2 liters/min). During the follow-up period, lung function improved, extravascular lung water (X-ray score) decreased and peak oxygen consumption (ml/min per kg) increased significantly from 15.5 +/- 1 (day -1) to 17.6 +/- 0.9 (day 4), to 17.8 +/- 0.9 (day 30), to 18.9 +/- 1 (day 90) and to 19.1 +/- 1 (day 180). Oxygen consumption at anaerobic threshold (ml/min per kg) also increased significantly from 11.6 +/- 0.8 (day -1) to 13 +/- 0.7 (day 4), to 13.7 +/- 0.5 (day 30), to 15.5 +/- 0.8 (day 90) and to 15.2 +/- 0.8 (day 180). These changes were associated with increased ventilation, tidal volume and dead space/tidal volume ratio at peak exercise. The improvement in exercise performance was associated with a decrease in norepinephrine at rest, a downward shift of norepinephrine kinetics at submaximal exercise and an increase in norepinephrine during orthostatic tilt. None of these changes were recorded in group B.

CONCLUSIONS

In patients with moderate congestive heart failure, ultrafiltration reduces the severity of the syndrome.

Effects of successful cardiac transplantation on plasma endothelin

After cardiac transplantation, cyclosporine-treated patients exhibit a high incidence of systemic hypertension, the mechanism of which is not known. Endothelin, a potent vasoconstrictor peptide of endothelial origin, may be activated by cyclosporine-induced endothelial injury and therefore may mediate post-transplant hypertension. In the present study, we tested whether immunoreactive endothelin-1 could be detected by radioimmunoassay in the plasma of cardiac transplant recipients and if levels correlated with hemodynamic characteristics, cyclosporine level, or renal function as assessed by serum creatinine. Plasma endothelin was measured in 22 stable cyclosporine-treated patients 9 days to 3 years after successful orthotopic cardiac transplantation before routine hemodynamic assessment and surveillance endomyocardial biopsy. Fifteen patients were receiving chronic therapy for hypertension. Plasma endothelin-1 was 5.2 +/- 1.8 pg/ml (range 3.1 to 10.5), which was increased compared with that in 12 normal subjects (1.9 +/- 0.3 pg/ml; range 1.4 to 2.4); the difference was statistically significant (p < 0.0001). Repeated sampling in 8 patients at weekly intervals identified a persistent increase in endothelin with only modest variability. Endothelin-1 did not correlate with any hemodynamic variable, serum creatinine or cyclosporine level. Thus, endothelin-1 is increased after successful orthotopic cardiac transplantation. In the absence of discrete correlations with hemodynamic variables, serum creatinine or cyclosporine levels, both the characteristics and mechanisms for increased endothelin in recipients of cardiac transplants require further evaluation.

Effects of cardiac transplantation on endothelium-dependent dilation of the peripheral vasculature in congestive heart failure

Patients with congestive heart failure demonstrate attenuated endothelium-dependent vasodilation of the peripheral vasculature, but there are no data regarding the effect of therapies on this abnormality or whether this abnormality is reversible. This study was performed to address the hypothesis that abnormalities in endothelium-dependent vasodilation in heart failure are improved by heart transplantation. Forearm blood flow responses to the intraarterial administration of a dose range of methacholine, an endothelium-dependent vasodilator, and nitroprusside, an endothelium-independent vasodilator, were examined in 2 separate protocols. In protocol 1, forearm blood flow responses to methacholine in 14 heart transplant recipients were 5.02 +/- 3.11, 11.55 +/- 7.20 and 11.61 +/- 10.24 ml/min/100 ml forearm volume. These responses were significantly greater than those in 10 patients with heart failure (2.23 +/- 1.22, 4.60 +/- 3.43 and 6.70 +/- 4.91 ml/min/100 ml forearm volume; p < 0.05). In contrast, the responses to nitroprusside were nearly identical in the 2 groups. In protocol 2, six patients were studied before and 4 months (range 1 to 11) after transplantation. Methacholine responses before transplantation were 2.5 +/- 1.3, 5.2 +/- 1.5 and 7.3 +/- 1.5 ml/min/100 ml forearm volume and were significantly improved after transplantation to 5.7 +/- 1.2, 12.1 +/- 3.0 and 14.2 +/- 2.2 ml/min/100 ml forearm volume (p < 0.05). Peak reactive hyperemia responses increased significantly from 19.0 +/- 3.7 to 44.8 +/- 6.4 ml/min/100 ml forearm volume (p < 0.01) after transplantation. These data demonstrate that heart transplantation was associated with a significant improvement in the forearm blood flow responses to methacholine.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma endothelin concentrations in humans with end-stage heart failure and after heart transplantation

OBJECTIVES AND BACKGROUND

Endothelin is an endothelium-derived vasoconstrictor peptide that increases systemic and renal vascular resistance at pathophysiologic concentrations. Recent studies have demonstrated its presence in the circulation and its elevation in animals with congestive heart failure, suggesting that endothelin may contribute to the vasoconstrictive state of heart failure. The current study was designed with two objectives: 1) to demonstrate the elevation of circulating endothelin in patients with heart failure, and 2) to determine the short- and long-term response of endothelin levels after heart transplantation.

METHODS

Plasma endothelin concentrations were measured in two patient groups. Group 1 included 24 patients with end-stage heart failure who were studied during evaluation for potential heart transplantation. Group 2 included 12 patients from Group 1 who had had heart transplantation. Plasma endothelin concentrations were measured before and on days 1, 3 and 7 after heart transplantation. Eight of these patients also had levels measured 3 to 12 months later.

RESULTS

Plasma endothelin concentrations were significantly elevated in patients with heart failure compared with those in an age-matched control group (11.7 +/- 1.1 vs. 6.8 +/- 0.3 pg/ml). In response to heart transplantation, plasma endothelin concentrations increased further and were sustained during a long-term follow-up. These later changes were associated with a significant increase in arterial pressure and serum creatinine.

CONCLUSIONS

This study demonstrates that endothelin concentrations are increased in patients with heart failure and increase further after heart transplantation. It suggests a possible role for endothelin in the cardiovascular and renal adaptive responses to human heart transplantation.

Role of Neurohumoral Control of the Circulation in Determining Exercise Capacity in Patients with Heart Failure

The weak relationship between left ventricular function and exercise capacity in heart failure has stimulated interest in neurohumoral mechanisms as possibly contributing to exercise intolerance. Although chronic activation of neuroendocrine systems is characteristic of heart failure and is accompanied by impaired reflex responsiveness to physiologic stimuli, data from clinical trials do not support the hypothesis that the abnormal neurohumoral state is directly related to exercise intolerance. Thus, these systems may play an important role in the natural history of the disease and its high mortality, but they may not be critical to the impaired exercise capacity.

Exercise hemodynamics and myocardial metabolism during long-term beta-adrenergic blockade in severe heart failure

Hemodynamics and myocardial metabolism at rest and during exercise were investigated in 21 patients with heart failure. The patients were evaluated before and after long-term treatment (14 +/- 7 months) with the beta-adrenergic blocking agent metoprolol. Clinical improvement with increased functional capacity occurred during treatment. Maximal work load increased by 25% (104 to 130 W; p less than 0.001). Hemodynamic data showed an increased cardiac index (3.8 to 4.6 liters/min per m2; p less than 0.02) during exercise. Pulmonary capillary wedge pressure decreased at rest (20 to 13 mm Hg; p less than 0.01) and during exercise (32 to 28 mm Hg; p = NS). Stroke volume index (30 to 39 g.m/m2; p less than 0.006) and stroke work index (28 to 46 g.m/m2; p less than 0.006) increased during exercise and long-term metoprolol treatment. The arterial norepinephrine concentration decreased at rest (3.72 to 2.19 nmol/liter; p less than 0.02) but not during exercise (13.2 to 11.1 nmol/liter; p = NS). The arterial-coronary sinus norepinephrine difference suggested a decrease in myocardial spillover during metoprolol treatment (-0.28 to -0.13 nmol/liter; p = NS at rest and -1.13 to -0.27 nmol/liter; p less than 0.05 during exercise). Coronary sinus blood flow was unchanged during treatment. Four patients produced myocardial lactate before the study, but none produced lactate after beta-blockade (p less than 0.05). There was no obvious improvement in a subgroup of patients with ischemic cardiomyopathy. In summary, there were signs of increased myocardial work load without higher metabolic costs after treatment with metoprolol.

Contractility of the transplanted, denervated human heart

The purpose of the study was to characterize the contractility of the transplanted human heart and to evaluate possible adverse effects of denervation or structural changes of the myocardium or coronary vessels. As an index of contractility, the linear slope k of the end-systolic pressure/dimension relationship during afterload increase with angiotensin II was determined by M-mode echocardiography in 34 heart transplant recipients and 20 healthy control subjects. Baseline findings for end-systolic diameter and systolic blood pressure were normal and similar in both groups, but the transplanted hearts performed at a significantly lower end-systolic wall stress (40.4 +/- 12 gm/cm2 vs 49.9 +/- 11 gm/cm2, p less than 0.001). Comparable increase of afterload was achieved in heart transplant recipients with significantly (p less than 0.001) less angiotensin II, which indicates increased vasoconstrictor sensitivity. Contractility index k did not differ between heart transplant recipients (12.95 +/- 4.9 mm/100 mm Hg) and control subjects (12.78 +/- 2.8 mm/100 mm Hg). This finding is consistent with a normal contractility of the transplanted, denervated human heart. Normal baseline contractility therefore is an intrinsic property of the intact heart, which is independent of autonomic neural control. Contractility was not compromised by increasing interval from transplantation or the presence of mild acute rejection or mild interstitial fibrosis. Mildly impaired contractility (k greater than 2 SD of k in control subjects) in four heart transplant recipients (12%) was neither associated with structural myocardial or coronary changes nor with rejection episodes or graft ischemic time. One may speculate that impaired contractility, which is present in a minority of heart transplant recipients, results from pretransplantation damage.

Future directions in vasodilator therapy for heart failure

Vasodilator therapy has become a major pharmacologic approach for improving left ventricular function, and consequently, vasodilator drugs are being used increasingly in the treatment of heart failure. Ideally, vasodilator drugs used in the long-term management of heart failure should show clearly defined pharmacodynamic effects. These include reduced impedance to left ventricular ejection, increased venous capacitance, increased left ventricular ejection fraction and reduced heart size, absence of neurohormonal stimulation, and slowed progression of left ventricular dysfunction. The mechanisms of action and sites of activity of the various vasodilator drugs currently available vary considerably, and none as yet has proved ideal for the treatment of heart failure or hypertension. The complexity surrounding the multiple vasoconstrictor mechanisms involved in heart failure has led to a rationale for combined vasodilator therapy and certain combinations are discussed. From a therapeutic standpoint, the development of drugs with multiple mechanisms of action is particularly attractive. Flosequinan is a new vasodilator agent whose cellular mechanism of action remains uncertain. Flosequinan has the advantage of being able to relax both arterial and venous beds and as such may be particularly beneficial in the treatment of heart failure.

Vasoconstriction in patients after heart transplantation

We have the values of rest and maximal blood flow and of venous compliance in the forearm in three groups of patients: those undergoing orthotopic heart transplantation, those with severe cardiac insufficiency, and a control group. The findings suggest the presence of arteriolo- as well as venoconstriction in transplanted patients. This, however, was less pronounced than in the patients with heart failure. Neither the values of maximal blood flow nor those of minimal peripheral resistance in the forearm obtained after a 5-minute ischaemic insult differed significantly between the patients after heart transplantation and the controls. Thus, arteriolar constriction can be removed by this insult in patients after transplantation.

Baroreflex control of renal sympathetic nerve activity is preserved in heart failure despite reduced arterial baroreceptor sensitivity

The purpose of this study was to determine if arterial baroreflex control of sympathetic nerve traffic is impaired in heart failure. We recorded renal nerve activity during changes in arterial pressure while simultaneously recording from aortic baroreceptor afferent fibers in 10 dogs with heart failure induced by rapid ventricular pacing and in 10 sham animals. Sensitivity of the aortic baroreceptors (percent change in nerve activity per millimeters mercury change in mean arterial pressure) was reduced in the heart failure group (heart failure, 2.3 +/- 0.3; sham, 3.6 +/- 0.4, p = 0.02). Despite the reduced sensitivity of aortic baroreceptors in heart failure, there was no difference in the baroreflex gain of renal nerve activity (heart failure, -5.5 +/- 1.4; sham, -5.8 +/- 1.3, p = NS). These values tended to decrease in both groups after vagotomy. The relation between baroreceptor input and renal sympathetic output, or central baroreflex gain (percent change in renal nerve activity divided by percent change in aortic nerve activity) was similar in both groups before vagotomy (heart failure, -2.4 +/- 0.6; sham, -2.3 +/- 0.5, p = NS). Vagotomy reduced central gain in the sham group (-0.9 +/- 0.1, p = 0.03) but not in the heart failure group (-1.7 +/- 0.5, p = NS), suggesting that the contribution of vagal afferents in the baroreflex arc is reduced in heart failure. Baroreflex control of R-R interval was attenuated in heart failure when assessed by blood pressure elevation but not reduction, indicating abnormal parasympathetic but preserved cardiac sympathetic mechanisms in heart failure. Thus, dogs with heart failure exhibit reduced sensitivity of aortic baroreceptors but preserved baroreflex control of renal nerve activity. Reduced baroreceptor sensitivity with preservation of baroreflex control of sympathetic nerve activity may contribute to the sympathoexcitatory state known to exist in heart failure.

Cardiac and peripheral vascular responses to adrenoceptor stimulation and blockade after cardiac transplantation

A denervated heart coupled to a periphery previously exposed to high catecholamine levels provides a unique model to study adrenoceptor physiology. Six orthotopic transplant patients (1.3 +/- 0.8 years postoperative) were age matched with six atropine-treated normal subjects. Simultaneous two-dimensionally targeted left ventricular echo-cardiograms and calibrated carotid pulse tracings were recorded. Left ventricular contractility was assessed with use of heart rate- and load-independent end-systolic indexes. Studies were performed at baseline and during dobutamine infusion with and without beta-adrenergic blockade with use of propranolol; effects were assessed during afterload changes generated by the alpha 1 agonist methoxamine. There were no differences in baseline contractility or reserve between transplant patients and normal subjects. The heart rate response to dobutamine was greater for transplant patients (p less than 0.001). In both groups, the positive inotropic and chronotropic effects of dobutamine were ablated by propranolol. Dobutamine plus propranolol (unopposed alpha 1 effect) did not change mean systemic pressure in transplant patients while markedly raising mean systemic pressures in normal subjects (36 +/- 18 mm Hg; p less than 0.001). In addition, during initial challenge with methoxamine, the transplant patients required 60% more alpha 1 agonist than did the normal subjects (p less than 0.001) to obtain a pressor effect. In summary, transplant patients who were previously in severe heart failure have normal left ventricular inotropic response to beta 1 activation and blockade, exaggerated chronotropic response to dobutamine and reduced sensitivity to stimulation with alpha 1-adrenoceptor agonists. These findings are consistent with a differential response of adrenoceptors to long-term stimulation after cardiac transplantation.

The relationship of the sympathetic nervous system and the renin-angiotensin system in congestive heart failure

Congestive heart failure is a complex clinical syndrome characterized by circulatory and metabolic abnormalities. It has been apparent for more than 25 years that the sympathetic nervous system and the renin-angiotensin-aldosterone system are markedly activated in the late stages of heart failure. These two systems interact to facilitate sympathetic drive and promote salt and water retention. Circumstantial evidence is now accumulating to indicate that excessive sympathetic drive and angiotensin II activity may contribute to the pathophysiology of heart failure. These observations suggest that a dual strategy of modulating sympathetic nervous system activity to the heart while blocking angiotensin II activity may provide a rational therapeutic approach to the treatment of heart failure. Xamoterol, a beta 1 partial agonist, may enhance myocardial contractile force in the steady state, while acting to inhibit excessive sympathetic drive during exercise or severe heart failure. The concomitant use of a converting-enzyme inhibitor would be expected to blunt the detrimental effects of excessive angiotensin II activity. Modulation of adrenergic drive coupled with inhibition of marked angiotensin II activity may be potentially more effective in the treatment of congestive heart failure than either strategy used alone.

Arterial baroreflex abnormalities in heart failure. Reversal after orthotopic cardiac transplantation

Arterial baroreflex control of the heart and peripheral circulation is markedly impaired in humans and animals with congestive heart failure. After reversal of heart failure in animal models, arterial baroreflex control of heart rate remains impaired for up to 8 months. Cardiac transplantation restores normal ventricular function and completely reverses heart failure, but does it normalize arterial baroreflex control of heart rate in humans? We studied baroreflex sensitivity in 11 patients with severe heart failure, six normal control patients, and 23 patients at 2 weeks to 4 years after orthotopic cardiac transplantation. Baroreflex sensitivity was assessed with intravenous bolus injections of phenylephrine and is expressed as change in RR or PP interval (msec) per millimeters of mercury rise in systolic arterial pressure. Atrial rate of both donor (denervated) and recipient (innervated) atria were measured in the transplant group. Baroreflex sensitivity in patients with severe heart failure was 2.0 +/- 0.3 msec/mm Hg, but in patients after cardiac transplantation, it was 13.0 +/- 0.9 msec/mm Hg (p less than 0.001). The responses in the transplant group were similar to those observed in normal controls (10 +/- 1.2 msec/mm Hg, p = NS). Our data indicate that patients with severe congestive heart failure have marked abnormalities of baroreflex control, which are reversed as early as 2 weeks after cardiac transplantation. In view of this rapid reversal, we consider it unlikely that abnormal baroreflex sensitivity seen in heart failure is due to structural alterations in the baroreceptors. We speculate that neurohumoral rather than structural abnormalities account for depressed baroreflex sensitivity in heart failure.

Sequential neurohumoral measurements in patients with congestive heart failure

Patients with chronic congestive heart failure are known to have increased plasma norepinephrine and plasma renin activity. In order to evaluate neurohumoral changes over time, we measured plasma norepinephrine and plasma renin activity at baseline and sequentially during follow-up in 49 patients with chronic, stable congestive heart failure. All patients were treated with digitalis and diuretics. Converting enzyme inhibitor therapy was prescribed as adjunctive therapy in 22 patients, while 10 patients were taking hydralazine and/or isosorbide dinitrate, seven were taking prazosin, and 10 had no adjunctive therapy. Patients were divided into those taking converting enzyme inhibitors (group I, n = 22) and those not taking converting enzyme inhibitors (group II, n = 27). Group I was followed for a median (25th to 75th percentiles) of 24.3 (18 to 27.9) months, while group II was followed for 18.7 (11.9 to 36.5) months. Results indicate that patients in group I demonstrate a significant positive trend for rise in plasma norepinephrine of 11.7 pg/ml per month (7.8 to 15 pg/ml per month, 95% confidence interval). Patients in group II also demonstrated a significant positive trend in plasma norepinephrine over time of 6.6 pg/ml per month (2.2 to 11.1 pg/ml per month). Moreover, there was a progressive trend upward in plasma renin activity over time in group II (median 0.34 ng/ml/hr per month; range 0.13 to 0.54). The data indicate that there is a significant trend of neurohumoral activation over time in patients with chronic, clinically stable congestive heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroendocrine manifestations of congestive heart failure

Congestive heart failure is a complex clinical syndrome characterized by a number of neuroendocrine responses. These responses are probably an evolutionary vestige of mechanisms designed to defend volume and maintain circulatory homeostasis. Activation of the sympathetic nervous system and renin-angiotensin-aldosterone system and the release of vasopressin have been clearly documented in patients with heart failure. Unlike the normal ventricle, the failing ventricle responds to peripheral vasoconstriction and sodium retention with further hemodynamic embarrassment and circulatory congestion. Certain vasorelaxant natriuretic substances are also released during heart failure, perhaps in an attempt to offset excessive peripheral constriction and sodium retention. Prostaglandin E2, atrial natriuretic peptide (or atrial natriuretic factor) and plasma dopamine are found to be increased in some patients with heart failure. However, peripheral constriction and sodium retention appear to be dominant, particularly in the advanced stages of heart failure. An understanding of these neuroendocrine responses has led to new developments in therapy. Angiotensin-converting enzyme inhibitors have emerged as distinctly useful drugs in the treatment of heart failure. Agents designed to block excessive sympathetic drive and inhibit vasopressin are under investigation. Infusion of atrial natriuretic factors and the use of selective dopamine agonists are also undergoing clinical trials in patients with heart failure. Increased knowledge of the neuroendocrine responses will likely result in even newer and more imaginative therapy.