Exon-array profiling unlocks clinically and biologically relevant gene signatures from formalin-fixed paraffin-embedded tumour samples

Background:

Degradation and chemical modification of RNA in formalin-fixed paraffin-embedded (FFPE) samples hamper their use in expression profiling studies. This study aimed to show that useful information can be obtained by Exon-array profiling archival FFPE tumour samples.

Methods:

Nineteen cervical squamous cell carcinoma (SCC) and 9 adenocarcinoma (AC) FFPE samples (10–16-year-old) were profiled using Affymetrix Exon arrays. The gene signature derived was tested on a fresh-frozen non-small cell lung cancer (NSCLC) series. Exploration of biological networks involved gene set enrichment analysis (GSEA). Differential gene expression was confirmed using Quantigene, a multiplex bead-based alternative to qRT–PCR.

Results:

In all, 1062 genes were higher in SCC vs AC, and 155 genes higher in AC. The 1217-gene signature correctly separated 58 NSCLC into SCC and AC. A gene network centered on hepatic nuclear factor and GATA6 was identified in AC, suggesting a role in glandular cell differentiation of the cervix. Quantigene analysis of the top 26 differentially expressed genes correctly partitioned cervix samples as SCC or AC.

Conclusion:

FFPE samples can be profiled using Exon arrays to derive gene expression signatures that are sufficiently robust to be applied to independent data sets, identify novel biology and design assays for independent platform validation.

Relationship between sleep apnoea and mortality in patients with ischaemic heart failure

OBJECTIVE

To determine whether the influence of sleep apnoea (SA) on the risk of death differs in patients with ischaemic and in those with non-ischaemic heart failure (HF).

DESIGN

Prospective observational study.

PATIENTS

Consecutive patients with HF with left ventricular ejection fraction < or =45% newly referred to the HF clinic between 1 September 1997 and 1 December 2004.

MAIN OUTCOME MEASURES

Patients underwent sleep studies and were divided into those with moderate to severe SA (apnoea-hypopnoea index > or =15/h of sleep) and those with mild to no SA (apnoea-hypopnoea index <15/h of sleep). They were followed up for a mean of 32 months to determine all-cause mortality rate.

RESULTS

Of 193 patients, 34 (18%) died. In the ischaemic group, mortality risk adjusted for confounding factors was significantly higher in those with SA than in those without it (18.9 vs 4.6 deaths/100 patient-years, hazards ratio (HR) = 3.03, 95% CI 1.04 to 8.84, p = 0.043). In contrast, in the non-ischaemic HF group, there was no difference in adjusted mortality risk between those with, and those without, SA (3.9 vs 4.0 deaths/100 patient-years, p = 0.929).

CONCLUSIONS

In patients with HF, the presence of SA is independently associated with an increased risk of death in those with ischaemic, but not in those with non-ischaemic, aetiology. These findings suggest that patients with ischaemic cardiomyopathy are more susceptible to the adverse haemodynamic, autonomic and inflammatory consequences of SA than are those with non-ischaemic cardiomyopathy.

The oxidative stress hypothesis of congestive heart failure: radical thoughts

There is extensive experimental evidence from in vitro and animal experiments that congestive heart failure (CHF) is a state of oxidative stress. Moreover, in animal models, the development of CHF is accompanied by changes in the antioxidant defense mechanisms of the myocardium as well as evidence of oxidative myocardial injury. This has led to the hypothesis that oxidative stress may be a mechanism of disease progression in CHF. Indeed, many patients consume antioxidant supplements making the assumption that no harm will result and, possibly, that this therapy will yield some clinical benefits. The focus of this review is to examine the oxidative stress hypothesis of CHF as it pertains to humans. To date, human studies that have sought evidence for a role of oxidative stress in patients with CHF have fallen short of providing strong support for this hypothesis. Studies that have demonstrated an association between oxidant stress and CHF are small and are hindered by methodologic limitations that diminish the impact of their conclusions. Randomized trials of antioxidant supplementation for CHF are scarce, and to our knowledge no study yet convincingly demonstrates any benefit from consuming antioxidant supplements. Therefore, the available evidence is insufficient to support or negate the oxidative stress hypothesis of CHF and the use of antioxidants cannot be recommended as a specific therapy for this condition.

Lack of evidence for peripheral alpha(1)- adrenoceptor blockade during long-term treatment of heart failure with carvedilol

OBJECTIVES

The purpose of this study was to determine whether carvedilol's alpha(1)-adrenoceptor antagonism persists during long-term therapy of patients with congestive heart failure (CHF).

BACKGROUND

Carvedilol and metoprolol differ in that carvedilol also antagonizes beta(2)- and alpha(1)-adrenoceptors. We hypothesized that in contrast to metoprolol, carvedilol would increase calf vascular conductance (CVC), blunt neurally mediated vasoconstriction and attenuate neuroeffector transfer function gain.

METHODS

We randomized 36 patients with CHF (age 55 +/- 1 years, ejection fraction 19 +/- 1%, means +/- SE) to either drug. Blood pressure (BP), heart rate, muscle sympathetic nerve activity (MSNA) and CVC were assessed before and after four months of treatment. The variability of BP and MSNA was determined using fast Fourier transformation.

RESULTS

Paired data were obtained in 23 (carvedilol, 13; metoprolol, 10) subjects. Both beta-blockers decreased heart rate, but neither affected mean BP or CVC (carvedilol: 0.016 +/- 0.002 to 0.018 +/- 0.003 U; metoprolol: 0.020 +/- 0.002 to 0.020 +/- 0.004 U). Isometric handgrip exercise (30% of maximum) increased heart rate, mean BP and MSNA. The calf vasoconstrictor response to handgrip exercise was not affected by carvedilol (from 16 +/- 6 resistance U to 25 +/- 10 resistance U, NS). The gain of the transfer of oscillations in MSNA into BP under resting conditions was not attenuated by carvedilol.

CONCLUSIONS

Carvedilol did not increase CVC, blunt the calf vasoconstrictor response to handgrip or attenuate the gain of the neuroeffector transfer function, indicating the absence of functionally important peripheral alpha(1)-adrenoceptor antagonism during long-term treatment of CHF.

Nonselective versus selective beta-adrenergic receptor blockade in congestive heart failure: differential effects on sympathetic activity

BACKGROUND

Activation of the sympathetic nervous system has important prognostic implications in chronic heart failure. Nonselective versus selective beta-adrenergic receptor antagonists may have differential effects on norepinephrine release from nerve terminals mediated by prejunctional beta(2)-adrenergic receptors.

METHODS AND RESULTS

Thirty-six patients with chronic heart failure were randomized to the nonselective beta-blocker carvedilol or the selective beta-blocker metoprolol (double-blind). Measurements of hemodynamics and cardiac and systemic norepinephrine spillover as well as microneurographic recordings of muscle sympathetic nerve traffic were made before and after 4 months of therapy. In the carvedilol group (n=17), there were significant reductions in both total body (-1.7+/-0.5 nmol/min, P<0.01) and cardiac norepinephrine spillover (-87+/-29 pmol/min, P<0.01). By contrast, in the metoprolol group (n=14), there were no significant changes in total body or cardiac norepinephrine spillover. Responses in the carvedilol group were significantly different from those observed in the metoprolol group (P<0.05). Both agents caused a reduction in heart rate and increases in pulse pressure, although mean arterial pressure did not change. Importantly, microneurographic measures of sympathetic nerve traffic to skeletal muscle did not change in either group.

CONCLUSIONS

Therapy with carvedilol caused significant decreases in systemic and cardiac norepinephrine spillover, an indirect measure of norepinephrine release. Such changes were not observed in patients treated with metoprolol. There was no effect of either agent on sympathetic efferent neuronal discharge to skeletal muscle. These findings suggest that carvedilol, a nonselective beta-blocker, caused its sympathoinhibitory effect by blocking peripheral, prejunctional beta-adrenergic receptors.

Effect of hyperoxia on left ventricular function and filling pressures in patients with and without congestive heart failure

STUDY OBJECTIVES

To determine the effects of hyperoxia on left ventricular (LV) function in humans with and without congestive heart failure (CHF).

DESIGN

An acute physiologic study of the effect of hyperoxia on right-heart hemodynamics, LV contractility (peak positive rate of rise of LV pressure [+dP/dt]), time constant of isovolumic left ventricular relaxation (tau), and LV filling pressures.

SETTING

Bayer Cardiovascular Clinical Research Laboratory at the Mount Sinai Hospital, Toronto, Ontario.

PATIENTS

Sixteen patients with stable CHF and 12 subjects with normal LV function received the hyperoxia intervention.

INTERVENTIONS

Patients received 21% O(2) by a nonrebreather mask, followed by 100% O(2) for 20 min, and 21% O(2) for a 10-min recovery period.

RESULTS

In response to hyperoxia, there was a 22 +/- 6% increase in LV end-diastolic pressure (LVEDP) in the CHF group and a similar 29 +/- 14% increase in LVEDP in the normal LV function group (p < 0.05 for both; mean +/- SEM). Hyperoxia was also associated with a prolongation in tau of 10 +/- 2% in the CHF group (p < 0.05) and 8 +/- 2% in the normal LV function group (p < 0.05). No changes in +dP/dt were observed in either group.

CONCLUSIONS

Hyperoxia was associated with impairment of cardiac relaxation and increased LV filling pressures in patients with and without CHF. These observations indicate that caution should be used in the administration of high inspired O(2) fractions to normoxic patients, especially in the setting of CHF.

Vitamin C augments the inotropic response to dobutamine in humans with normal left ventricular function

BACKGROUND

We studied the effect of an antioxidant, the intracoronary infusion of vitamin C, on basal and dobutamine-stimulated left ventricular (LV) contractility.

METHODS AND RESULTS

Nineteen patients with normal ventricular function participated in this study. A micromanometer-tipped catheter was inserted into the LV. In the experimental group (n=10), an infusion catheter was positioned in the left main coronary artery. LV peak +dP/dt (LV +dP/dt) was measured in response to the intravenous infusion of dobutamine before (Dob) and during (Dob+vit C) the intracoronary infusion of vitamin C. The intracoronary infusion of vitamin C had no effect on basal LV +dP/dt or any other hemodynamic parameter. The infusion of vitamin C augmented the LV +dP/dt response to dobutamine by 22+/-4% (Dob, 1680+/-76 mm Hg/s; Dob+vit C, 1814+/-97 mm Hg/s, P<0.01). In the control group (n=9), LV +dP/dt was measured in response to sequential infusions of dobutamine (Dob, Dob-2) given at the same time intervals as in the experimental group but without the intracoronary infusion of vitamin C. In contrast to the experimental group, no difference in LV +dP/dt was observed between the 2 infusions of dobutamine (Dob, 1706+/-131 mm Hg/s; Dob-2, 1709+/-138 mm Hg/s, P=NS).

CONCLUSIONS

The administration of the antioxidant vitamin C augments the inotropic response to dobutamine in humans. This suggests that redox environment contributes to the adrenergic regulation of ventricular contractility.

Unsaturated aldehydes including 4-OH-nonenal are elevated in patients with congestive heart failure

BACKGROUND

Lipid peroxidation generates several unsaturated aldehydes, such as 4-OH-nonenal (HNE), which may interact with and modify the function of other molecules that are of biological importance. Although congestive heart failure (CHF) is a state of generalized oxidative stress, the resultant spectrum of saturated and unsaturated aldehydes has not been systematically characterized in this condition.

METHODS

We studied 8 CHF patients and 8 age-matched patients with normal left ventricular (LV) function. The concentrations of 22 aldehydes produced by lipid peroxidation, including saturated (n-alkanals) and unsaturated (t-2-alkenals, t-2,t-4-alkadienals, 4-OH-alkenals) aldehydes, were measured in arterial plasma by gas chromatography mass spectrometry (GC/MS). LV contractility (+dP/dt) and relaxation (Tau) were directly measured with a micromanometer-tipped catheter.

RESULTS

Compared with patients who have normal LV function, CHF patients had higher levels of total aldehydes (9,311 +/- 835 v 6,594 +/- 344 nmol/L, P < .01), as well as multiple unsaturated aldehydes (t-2-alkenals and 4-OH-alkenals, including HNE). In the CHF group, a strong relationship was observed between total aldehyde concentration and both +dP/dt (correlation coefficient = -0.76, P < .05) and Tau (correlation coefficient = 0.78, P < .05).

CONCLUSION

Unsaturated aldehyde levels were consistently elevated in the plasma of CHF patients compared with patients who have normal LV function. In CHF patients, elevated aldehyde levels were associated with impairment of LV contractility.

Reducing cardiac filling pressure lowers norepinephrine spillover in patients with chronic heart failure

BACKGROUND

We studied the cardiac sympathetic response to selective unloading of cardiopulmonary baroreceptors in subjects with normal left ventricular (LV) function and congestive heart failure (CHF).

METHODS AND RESULTS

Eight patients with normal LV function (age 57+/-5 years, ejection fraction 58+/-2%) and 8 patients with CHF (age 60+/-2 years; ejection fraction 19+/-2%) were studied. Instrumentation consisted of an arterial line, a pulmonary artery catheter, and a coronary sinus thermodilution catheter. The radiotracer technique was used for measurement of cardiac norepinephrine spillover (CANESP) and total-body norepinephrine spillover. Lower-body negative pressure (LBNP) was applied at 2 levels: nonhypotensive and hypotensive LBNP. Nonhypotensive LBNP reduced filling pressures significantly in both groups. Arterial pressure did not change. This reduction in filling pressures caused a significant reduction in CANESP in the CHF group (from 167+/-53 to 125+/-37 pmol/min, P<0.05) but no change in the normal LV function group. Hypotensive LBNP caused a significant increase in CANESP in the normal group (73+/-13 vs 122+/-27 pmol/min, P<0.05) but no significant change in those with CHF.

CONCLUSIONS

We conclude that selective reduction in filling pressures lowers cardiac norepinephrine spillover in patients with CHF. These findings suggest that a goal of CHF management should be to reduce cardiac filling pressures while avoiding systemic hypotension.

Sympathetic responses to atrial natriuretic peptide in patients with congestive heart failure

Previous studies have shown that atrial natriuretic peptide (ANP) has relative sympathoinhibitory effects that are of potential benefit in patients with congestive heart failure (CHF). In this study, cardiac and systemic sympathetic responses to ANP were evaluated and compared with responses to sodium nitroprusside (SNP) in patients with CHF. Right- and left-heart hemodynamics were obtained simultaneously with cardiac (CANESP) and total body (TBNESP) norepinephrine spillover; these were measured by using the radiotracer technique. Reductions in arterial blood pressure and cardiac filling pressures were similar with both drugs. ANP and SNP caused a significant and similar increase in TBNESP. Mean values for CANESP did not change in either group, but the response of individual patients was dependent on the effect on diastolic blood pressure (r = -0.71, p<0.01). These results do not provide evidence for a sympathoinhibitory effect of ANP, but suggest that in patients with CHF, cardiac sympathoexcitatory response to arterial baroreceptor unloading may be countered by a potential sympathoinhibitory effect caused by a reduction in cardiac filling pressures. In the setting of CHF, vasodilator therapy may decrease cardiac sympathetic activity if systemic hypotension is avoided.

Long-term endothelial dysfunction after coronary artery stenting

OBJECTIVES

We assessed the endothelial-dependent vasomotor function in nonrestenotic coronary arteries more than six months following stent implantation, balloon angioplasty (BA), and directional atherectomy (DCA).

BACKGROUND

Catheter-based coronary interventions are associated with extensive arterial injury. Endothelial function has been shown to remain chronically abnormal after vascular injury. The long-term effects of different percutaneous coronary interventions on endothelial function are not known.

METHODS

Thirty-nine patients treated at least six months earlier with a coronary intervention for isolated proximal left anterior descending (LAD) stenosis, with no evidence of restenosis, were studied. Twelve patients had been stented, 15 had been treated with BA, and 12 had undergone DCA. Changes in diameter of the intervened LAD, and the unintervened circumflex coronary artery (Cx), in response to intracoronary acetylcholine infusions were assessed by quantitative angiography.

RESULTS

The groups had similar angiographic characteristics and risk factors for endothelial dysfunction. The LAD constricted significantly more (p = 0.02) in previously stented patients (-21.8+/-4.3%), as compared to patients previously treated with BA (-9.5+/-2.8%) or with DCA (-9.1+/-3.6%). In contrast, acetylcholine infusion resulted in mild constriction in the Cx, which was similar in the three groups (p = 0.47). By multiple regression analysis, previous implant of a stent was the only significant predictor of LAD constriction (p = 0.008).

CONCLUSIONS

More severe endothelial dysfunction was observed long term after stenting as compared to BA or DCA. These findings may have implications with respect to the progression of atherosclerosis in coronary arteries subjected to percutaneous interventions.

Inotropic and sympathetic responses to the intracoronary infusion of a beta2-receptor agonist: a human in vivo study

BACKGROUND

On the basis of the presence of beta2-receptors within the sympathetic nervous system, beta2-stimulation may increase cardiac sympathetic outflow. We addressed the hypothesis that sympathoexcitatory beta2-receptors are present in the human left ventricle.

METHODS AND RESULTS

The beta2-agonist salbutamol was infused into the left coronary artery in 3 groups of patients: group 1 (n=9, no beta-blocker therapy), group 2 (n=7, beta1-selective blockade with atenolol), and group 3 (n=6, nonselective beta-blockade with nadolol). Left ventricular +dP/dt in response to increasing concentrations of salbutamol was measured in all groups, and cardiac norepinephrine spillover was measured in group 1. There were no systemic hemodynamic changes in any group. Salbutamol resulted in a 44+/-6% increase in +dP/dt in group 1, a 25+/-6% increase in group 2 (P<0.05 versus group 1), and no increase in group 3. Salbutamol also resulted in a 124+/-37% increase in cardiac norepinephrine spillover in group 1 (P<0.05).

CONCLUSIONS

Evidence that salbutamol increased norepinephrine release from cardiac sympathetic nerves was provided by the observations that atenolol suppressed the salbutamol inotropic response, demonstrating that this response was mediated in part by beta1-receptors and that salbutamol also resulted in an increase in cardiac norepinephrine spillover. This result provides in vivo evidence, in humans, for the role of sympathoexcitatory cardiac beta2-receptors.

Biochemical, hemodynamic, and vascular evidence concerning the free radical hypothesis of nitrate tolerance

Tolerance to nitroglycerin (NTG) may be due to increased superoxide anion production. Hemodynamic parameters and biochemical markers of free radical production were measured in 20 healthy male subjects at baseline, 3 h after acute transdermal NTG (0.6 mg/h), and after 5 days of continuous therapy. Transdermal NTG therapy was continued, and 2 days later all subjects received 2 g of oral vitamin C, or placebo, in a double-blind, randomized, crossover fashion. In another study of eight male subjects, forearm plethysmography was used to assess the venous responses to sublingual NTG at baseline, after 5 days of sustained transdermal NTG therapy (0.6 mg/h), and after 2 g of oral vitamin C or placebo. Systolic blood pressure decreased in response to acute transdermal NTG therapy but returned to normal after sustained NTG therapy, indicating the development of tolerance. The venous volume responses to sublingual NTG were significantly diminished after sustained therapy with transdermal NTG. Plasma lipid peroxidation products, 8-iso-PGF2 alpha, and vitamin C were unchanged by acute and sustained therapy with transdermal NTG. Vitamin C failed to restore either the hemodynamic or venous effects of NTG. These results do not support the hypothesis that nitrate therapy and tolerance is associated with increased free radical production.

Electrical and hemodynamic correlates of the maximal rate of pressure increase in the human left ventricle

BACKGROUND

The rate of left ventricular (LV) pressure increase (LV + dP/dt) may be related to QRS duration, as well as to a number of hemodynamic parameters.

METHODS AND RESULTS

We studied the relation between basal LV + dP/dt and QRS duration in 43 patients with normal LV function and 81 patients with heart failure undergoing diagnostic catheterization. We also examined the relationship between LV + dP/dt and heart rate, as well as measures of both LV preload and afterload. In patients with normal LV function, there was a strong relationship between basal LV + dP/dt and resting heart rate, whereas the relationship with QRS duration was of borderline significance. In patients with heart failure, the relationship with heart rate was lost; however, LV systolic pressure, QRS duration, and LV end-diastolic pressure all made significant contributions to a model predicting LV + dP/dt.

CONCLUSIONS

These data show a strong relationship between resting heart rate and LV + dP/dt in the healthy human LV. In patients with heart failure, the relationship with heart rate is not maintained; however, there is a systematic relationship between LV + dP/dt and both the time-course of the electrical activation and measures of LV loading conditions.

Hemodynamic and biochemical effects of 100% oxygen breathing in humans

High concentrations of inspired oxygen have been reported to have significant hemodynamic effects that may be related to increased free radical production. If oxygen therapy increases free radical production, it may also modify hemodynamic responses to a nitric oxide donor. Twenty-nine healthy male volunteers were studied using randomized, double-blind, placebo-controlled, crossover designs to determine whether oxygen therapy is associated with hemodynamic and forearm vascular effects. We measured hemodynamic parameters and forearm vascular responses before and 1 h after exposure to 100% oxygen versus medical air. Plasma 8-iso-PGF2alpha and plasma vitamin C were measured to assess the biochemical effects of oxygen administration. Hemodynamic measurements were also made following the acute administration of sublingual nitroglycerin. Oxygen therapy caused no significant change in blood pressure, plasma 8-iso-PGF2alpha, or vitamin C. Oxygen did cause a significant reduction in heart rate and forearm blood flow, and an increase in peripheral vascular resistance. Oxygen caused no change in the hemodynamic response to nitroglycerin. Therefore, in healthy young adults, therapy with 100% oxygen does not affect blood pressure, despite causing an increase in vascular resistance, is not associated with evidence of increased free radical injury, and does not affect the hemodynamic responses to nitroglycerin.

Cardiac and systemic sympathetic activity in response to clonidine in human heart failure

OBJECTIVES

We studied the effects of clonidine on cardiac sympathetic activity and left ventricular function in patients with congestive heart failure (CHF).

BACKGROUND

Sympathetic activation has major prognostic implications in patients with heart failure. Clonidine, an imidazoline and alpha2-receptor agonist, has been shown to cause a reduction in generalized sympathetic activity.

METHODS

Nine patients with CHF (left ventricular ejection fraction 22+/-4% [mean+/-SEM]) received a 50 microg and 100 microg bolus of clonidine intravenously. Study measurements included right and left heart hemodynamics, cardiac output, rate of rise in left ventricular peak positive pressure (LV + dP/dt) and tau, along with cardiac and total body norepinephrine spillover. The radiotracer method was used for calculation of norepinephrine spillover.

RESULTS

Right and left heart filling pressures did not change in response to either dose of clonidine. Mean arterial pressure fell after the second dose of clonidine, from 94+/-8 to 82+/-6 mm Hg (p < 0.05). The LV + dP/dt was reduced from 737+/-53 to 629+/-43 mm Hg/s (p < 0.05). Clonidine also caused a significant increase in tau, as measured by the method of Weiss (65+/-3 vs. 74+/-4 ms, p < 0.01) and the direct pressure half-time technique (48+/-2 vs. 54+/-3 ms, p < 0.01). Cardiac norepinephrine spillover fell from 121+/-29 to 52+/-20 pmol/min in response to 100 microg of clonidine (p < 0.01 vs. control).

CONCLUSIONS

Despite a significant fall in arterial pressure, clonidine caused a marked reduction in sympathetic activity directed at the heart. The negative inotropic and lusitropic effects appear to be secondary to this reduction in sympathetic drive. Because increased cardiac and generalized sympathetic activity are strong predictors of an adverse outcome in patients with CHF, the role of centrally active sympathoinhibitory agents in the therapy of CHF deserves further exploration.

Therapy with nitroglycerin increases coronary vasoconstriction in response to acetylcholine

OBJECTIVES

The purpose of this study was to investigate whether therapy with nitroglycerin (GTN) would lead to abnormal coronary artery responses to the endothelium-dependent vasodilator acetylcholine.

BACKGROUND

Nitroglycerin therapy is associated with specific biochemical changes in the vasculature that may lead to increased vascular sensitivity to vasoconstrictors.

METHODS

Patients were randomized to continuous transdermal GTN, 0.6 mg/h (n = 8), or no therapy (n = 7), for 5 days prior to a diagnostic catheterization. Patients had similar risk factors for endothelial dysfunction. Quantitative angiography was performed in the morning to measure the mean luminal diameter of the left anterior descending coronary artery (LAD) in response to intracoronary acetylcholine (peak concentration, 10(-4) mol/liter). The transdermal preparation was removed from the GTN group, and 3 h later experimental procedures were repeated.

RESULTS

In the morning, the GTN group experienced greater coronary constriction in response to acetylcholine infusion than those not receiving GTN (-19.6+/-4.2 vs. -3.8+/-3.0%; p = 0.01). Three hours later, the GTN group continued to display greater constriction to acetylcholine (-24.1+/-5.9%) as compared to the non-GTN group (-1.8+/-4.8%). When the morning and afternoon responses to acetylcholine were compared, the increase in coronary constriction in the GTN group was greater than the change observed in the non-GTN group (p < 0.05).

CONCLUSIONS

This study demonstrates that therapy with GTN causes abnormal coronary vasomotor responses to the endothelium-dependent vasodilator acetylcholine, changes that were persistent for up to 3 hours after GTN discontinuation. This nitrate-associated vasomotor dysfunction has implications with respect to the development of nitrate tolerance and the potential for adverse events during nitrate withdrawal.

Cardiac sympathetic activity in response to acute myocardial ischemia

Although experimental evidence has demonstrated that brief periods of myocardial ischemia are not associated with norepinephrine overflow from the heart, cardiac sympathetic responses to myocardial ischemia in humans remain unclear. Eleven patients undergoing angioplasty of the left anterior descending coronary artery had cardiac norepinephrine spillover measured immediately before inflation, during the final minute of a 5-min balloon inflation, and 1 min after deflation. Angioplasty caused significant S-T segment elevation and a reduction in the transcardiac lactate extraction ratio. Cardiac norepinephrine spillover was reduced from a mean value of 58 +/- 14 pmol/min at control to 41 +/- 15 pmol/min during balloon inflation and 38 +/- 14 pmol/min after deflation (P < 0.05 vs. control for both inflation and deflation values). In contrast, during balloon inflation, there were significant increases in arterial norepinephrine and epinephrine concentrations. Therefore, a brief period of myocardial ischemia caused by angioplasty of the left anterior descending coronary artery does not result in cardiac sympathetic activation, despite evidence of generalized sympathoadrenal activation.

Sympathetic alternans. Evidence for arterial baroreflex control of muscle sympathetic nerve activity in congestive heart failure

Alternation in the amplitude of muscle sympathetic nerve activity (MSNA) was documented in three patients with severe heart failure. In the index patient with pulsus alternans, the amplitude of MSNA was inversely related to changes in the preceding diastolic pressure with a lag time of 1.2 to 1.3 seconds, indicating that oscillations in burst amplitude are determined primarily by changes in this component of blood pressure. Spectral analysis of the blood pressure and MSNA signals identified two spectral peaks, one at the cardiac frequency and a second peak, with greater spectral power, at the alternans frequency (ie, at half the heart rate). The latter peak for both blood pressure and MSNA disappeared when alternans was abolished by nitroglycerin. The presence of sympathetic alternans in synchrony with pulsus alternans and the rapid transduction of changes in the diastolic blood pressure afferent signal to the amplitude of sympathetic outflow indicate that the arterial baroreflex control of MSNA must be active and rapidly responsive in human heart failure.

Muscarinic receptor modulation of basal and beta-adrenergic stimulated function of the failing human left ventricle

The objective of this study was to evaluate the effect of muscarinic receptor modulation on basal and beta-adrenergic stimulated left ventricular function in patients with heart failure. 21 heart failure patients and 14 subjects with normal ventricular function were studied. In Protocol 1 intracoronary acetylcholine resulted in a 60+/-8% inhibition of the left ventricular +dP/dt response to intracoronary dobutamine in the normal group, and a similar 70+/-13% inhibition in the heart failure group. Acetylcholine also attenuated the dobutamine-mediated acceleration of isovolumic relaxation (Tau) in both groups. Acetylcholine alone had no effect on Tau in the normal group, while it prolonged Tau in the heart failure group. In Protocol 2 intracoronary atropine resulted in a 35+/-10% augmentation of the inotropic response to dobutamine in the normal group, versus a non-significant 12+/-15% augmentation of the dobutamine response in the heart failure group. In Protocol 3, in 6 heart failure patients, both effects of acetylcholine, the slowing of ventricular relaxation and the inhibition of beta-adrenergic responses, were reversed by the addition of atropine. Therefore, in the failing human left ventricle muscarinic stimulation has an independent negative lusitropic effect and antagonizes the effects of beta-adrenergic stimulation.

Cardiac sympathetic responses to acute vasodilation. Normal ventricular function versus congestive heart failure

BACKGROUND

Although there is indirect evidence of impaired baroreflex control of sympathetic outflow directed at heart muscle, the regulation of cardiac sympathetic activity in the setting of heart failure is largely unexplored. We used the norepinephrine spillover method to address the hypothesis that baroreflex control of cardiac sympathetic activity is reduced in heart failure.

METHODS AND RESULTS

Twenty-three patients were studied, 17 in a group with heart failure and 6 in a group with normal ventricular function. In both groups, cardiac norepinephrine spillover was assessed in response to nitroprusside infused to steady-state conditions. Nitroprusside resulted in significant reductions in mean systemic arterial pressure (normal group, -15 +/- 3% [mean +/- SEM]; heart failure group, -13 +/- 1%) and mean pulmonary artery pressure (normal group, -25 +/- 10%; heart failure group, -29 +/- 4%). In response to nitroprusside, there was a 98 +/- 16% increase in cardiac norepinephrine spillover in the normal group (from 81 +/- 10 to 159 +/- 25 pmol/min, P < .05). Despite similar hemodynamic responses to nitroprusside in the heart failure group, there was only a 28 +/- 14% increase in cardiac spillover (from 211 +/- 71 to 245 +/- 59 pmol/ min, P = NS), a response that was significantly smaller than that seen in the normal group.

CONCLUSIONS

In patients with heart failure compared with subjects with normal ventricular function, there was a significantly smaller increase in cardiac sympathetic activity in response to a steady-state infusion of nitroprusside. This result provides evidence for reduced baroreflex control of cardiac sympathetic activity in heart failure.

Acute effects of beta 1-selective and nonselective beta-adrenergic receptor blockade on cardiac sympathetic activity in congestive heart failure

BACKGROUND

beta-Blockers may reduce cardiac sympathetic activity in patients with heart failure by antagonizing beta-adrenergic receptors that facilitate sympathetic outflow to the heart. To explore this possible effect of beta-blockade, we measured cardiac norepinephrine spillover responses in patients with heart failure after the acute administration of either propranolol, a nonselective beta-blocker, or metoprolol, a beta 1-selective agent.

METHODS AND RESULTS

Eighteen patients were studied. Repeated intravenous doses of propranolol (0.5 mg; nine patients; left ventricular ejection fraction, 14 +/- 2%) or metoprolol (1.0 mg; nine patients; left ventricular ejection fraction, 18 +/- 2%) were administered until one of the following end points was reached: a 15% decrease in heart rate, left ventricular +dP/dt, or mean arterial blood pressure or a 5 mm Hg increase in left ventricular end-diastolic pressure. Propranolol (mean dose, 2.0 mg) and metoprolol (mean dose, 3.6 mg) caused similar reductions in heart rate, +dP/dt, and coronary sinus plasma flow. Cardiac norepinephrine spillover was reduced after propranolol (277 +/- 55 to 262 +/- 53 pmol/min, P < .05) but was increased after metoprolol (233 +/- 57 to 296 +/- 82 pmol/min, P < .05). In a comparison of the two groups, the decrease in spillover after propranolol was significantly different than the increase seen after metoprolol (P < .01).

CONCLUSIONS

The administration of a beta 1-selective antagonist was associated with increased cardiac norepinephrine spillover. In contrast, the administration of a nonselective beta-blocker until similar hemodynamic end points were reached caused a reduction in norepinephrine spillover. This suggests that in patients with heart failure, nonselective beta-blockade may have favorable inhibitory effects on cardiac sympathetic activity.

Digoxin reduces cardiac sympathetic activity in severe congestive heart failure

OBJECTIVES

This study evaluated the effect of digoxin on cardiac sympathetic activity in patients with congestive heart failure.

BACKGROUND

Digoxin favorably alters autonomic tone in heart failure. Whether it reduces cardiac sympathetic drive in the setting of heart failure is unknown.

METHODS

Digoxin (0.25 mg intravenously) was administered to 12 patients with severe heart failure and elevated left ventricular end-diastolic pressure (> 14 mm Hg, Group A), 5 patients with less severe heart failure who had normal left ventricular end-diastolic pressure (> 14 mm Hg, Group B) and 6 patients with normal ventricular function. Seven additional patients with heart failure were studied as a time control group. Cardiac and total body norepinephrine spillover, systemic arterial pressure, left ventricular filling pressure and peak positive first derivative of left ventricular pressure were all assessed before and 30 min after administration of digoxin.

RESULTS

In Group A there were no changes in hemodynamic variables or total body norepinephrine spillover after digoxin administration; however, there was a significant reduction in cardiac norepinephrine spillover (263 +/- 70 to 218 +/- 62 pmol/min, mean +/- SEM, p < 0.001). In contrast, in Group B, digoxin caused a significant increase in cardiac norepinephrine spillover that was not associated with any hemodynamic changes or a change in total body spillover. There were no hemodynamic changes or a change in total body spillover. There were no hemodynamic or spillover changes in the time control or normal ventricular function group.

CONCLUSIONS

Digoxin, in the absence of detectable inotropic or hemodynamic effects, caused a reduction in cardiac norepinephrine spillover in patients with heart failure who had elevated filling pressures. This finding suggests a potentially beneficial primary autonomic action of digoxin in patients with severe heart failure.

Functional significance of presynaptic alpha-adrenergic receptors in failing and nonfailing human left ventricle

BACKGROUND

There are alpha-adrenergic receptors on human myocardium that exert positive inotropic effects. The effect of alpha-adrenergic receptor blockade on human left ventricular (LV) performance has not been fully explored. Although alpha-adrenergic receptor blockade might have effects on LV function that are mediated via blockade of postsynaptic myocardial alpha-adrenergic receptors, it is also possible that blockade of presynaptic alpha 2-adrenergic receptors and subsequent increased release of norepinephrine would have effects on LV performance. In the present study, we explored the effects of nonselective alpha-adrenergic receptor blockade on LV performance and transcardiac norepinephrine concentrations in a group of patients with normal LV function and in a group of patients with congestive heart failure secondary to dilated cardiomyopathy.

METHODS AND RESULTS

Using an intracoronary drug infusion technique, we administered the nonselective alpha-adrenergic antagonist phentolamine to 13 patients with normal LV function and 19 patients with congestive heart failure secondary to dilated cardiomyopathy. With a high-fidelity LV catheter, the systolic (+dP/dt) and diastolic (-dP/dt and Tau) LV function responses to intracoronary infusion of phentolamine (0.2 mg/min x 5 minutes) were assessed. In 8 patients with normal ventricular function and 10 patients with congestive heart failure, arterial and coronary sinus blood samples were drawn to determine the effects of phentolamine on catecholamine concentrations. Phentolamine had no measurable effect on LV performance or catecholamine concentrations in the normal ventricular function group. In patients with congestive heart failure, intracoronary phentolamine caused a significant increase in +dP/dt and the rate of isovolumic LV relaxation (-dP/dt and Tau). These hemodynamic effects were accompanied by a significant increase in coronary sinus norepinephrine concentration but no change in arterial norepinephrine concentration.

CONCLUSIONS

Myocardial alpha-adrenergic receptor blockade causes significant inotropic and lusitropic effects in the failing but not the nonfailing human LV. These effects appear to be mediated by increased release of norepinephrine from cardiac nerves secondary to blockade of presynaptic alpha 2-adrenergic receptors. Differences in the responses of the failing and nonfailing human LV appear to reflect the higher level of sympathetic activation that is seen in the group with congestive heart failure. This suggests that the presynaptic alpha 2-adrenergic receptor exerts a tonic inhibitory effect on the release of norepinephrine from cardiac nerves in patients with congestive heart failure.