The renin system and atrial natriuretic hormone in congestive heart failure

The renin angiotensin system is activated in the majority of patients with chronic congestive heart failure of moderate to severe symptomatology. Renin release may result from one of several different stimuli: renal tubular sodium delivery and sensing by the macula densa, sympathetic nervous system activity, and baroreceptor to changes in renal blood flow. Difficulties arise with an analysis of renin angiotensin system activity due to the necessity for diuretic therapy in the majority of these patients. Despite the presence of diuretic therapy, however, there is a wide range of renin angiotensin system activity. In evaluating this activity the administration of a converting enzyme inhibitor will block the contribution of angiotensin mediated vasoconstriction, thereby confirming the importance of the renin angiotensin system activity as a mediator of the long-term consequences of heart failure. In situations of low plasma renin activity, vasoconstriction is mediated by an alternate mechanism. The mechanisms of this non-renin mediated vasoconstriction are less apparent, but may include calcium mediated vasoconstriction, and the effects of increased cytosolic content. This low renin group of patients appear to be very sensitive to reversal of vasoconstriction by calcium channel antagonists, especially when converting enzyme inhibitors are ineffective. In an analysis of the factors that may result in renin release, tubular delivery of sodium to the macula densa may emerge as the most important regulator of renin release.(ABSTRACT TRUNCATED AT 250 WORDS)

The treatment of diastolic heart failure

Recommendations for the treatment of diastolic heart failure must be based on theoretical issues. Evidence-based outcomes from clinical trials are not available at this time, but there is an increasing mandate for more focused studies for this clinical disorder. Meaningful outcomes require delineation of patient populations, including identification of underlying disease and comorbid cardiovascular disorders. Until such information is available, we must rely on an understanding of the natural history of associated disorders, extrapolation of treatment strategies that are successful for systolic heart failure management, and use of pharmacologic agents that empirically target the observed hemodynamic abnormalities of diastolic heart failure.

Dissociation between ACE activity and autonomic response to ACE inhibition in patients with heart failure

BACKGROUND

Administration of angiotensin-converting enzyme (ACE) inhibitors to patients with congestive heart failure has been shown to increase parasympathetic tone as indicated by increases in high-frequency heart rate variability. The mechanism for this effect, including its relation to changes in baroreflex activity, blood pressure variability, and suppression of ACE activity, remains undefined. This study was designed to test the relation of these variables, which may govern changes in autonomic activity, to the previously described increase in parasympathetic tone.

METHODS

Seven patients with heart failure received a 3-hour infusion of the ACE inhibitor enalaprilat. Hemodynamic variables and parameters of heart rate and blood pressure variability, baroreflex gain derived from the interaction of heart rate and blood pressure variability, and serum ACE activity were measured during and after the infusion. Measures of heart rate and blood pressure variability were also compared against a historic control group.

RESULTS

Serum ACE activity was significantly suppressed throughout and after enalaprilat infusion. Hemodynamic measures did not change other than a small decline in right atrial and pulmonary capillary wedge pressures. Parasympathetic tone showed an initial significant increase with a peak at 2 hours but then declined below baseline 8 hours after initiation of enalaprilat infusion. Sympathetically influenced low-frequency heart rate variability was significantly increased above baseline in the enalaprilat treatment group 8 hours after initiation of the infusion. Baroreflex gain showed a significant trend to an increase with the maximum value coinciding with the peak in parasympathetic tone. There was no change in blood pressure variability in the enalaprilat group and no change in baroreflex gain, heart rate variability, or blood pressure variability in the control group.

CONCLUSIONS

Parasympathetic tone and baroreflex gain increased with parenteral administration of an ACE inhibitor but subsequently decreased below baseline values despite continued suppression of serum ACE activity. The dissociation between ACE suppression and autonomic response to ACE inhibition indicates that enzyme systems not reflected by plasma ACE activity or independent from the classic pathways of angiotensin formation contribute to the regulation of the autonomic response to ACE inhibition in patients with heart failure. The absence of significant change in hemodynamic variables or in blood pressure variability indicates that these autonomic changes are not an indirect reflex response to ACE inhibitor-induced vasodilation or hemodynamic baroreceptor stimulation.

Angiotensin II enhances integrin and alpha-actinin expression in adult rat cardiac fibroblasts

Angiotensin II (Ang II) plays an important role in cardiac remodeling through stimulation of proliferation and extracellular matrix (ECM) production in cardiac fibroblasts. Integrins are a family of transmembrane receptors that mediate the attachment of cells to ECM. We hypothesized that Ang II regulation of integrins further contributes to its role in cardiac remodeling. We cultured adult rat cardiac fibroblasts with and without Ang II (100 nmol/L) to determine the effects on mRNA and protein levels of integrins, as well as alpha-actinin and other cytoskeletal proteins that link to integrins at the site of focal adhesions. Ang II was also added in the presence of irbesartan (10 micromol/L), a specific Ang II type 1 (AT(1)) receptor antagonist, or PD 123319 (10 micromol/L), a specific Ang II type 2 receptor antagonist. To investigate the function of these integrins, we determined the effects of blocking antibodies on Ang II-induced adhesion to ECM. We also treated spontaneously hypertensive rats (SHR) with an AT(1) receptor blocker, losartan, or with hydralazine to investigate integrin and alpha-actinin expression in treated and untreated SHR. Ang II enhanced alpha(v), beta(1), beta(3), and beta(5) integrins; osteopontin; and alpha-actinin mRNA and protein levels in cardiac fibroblasts. All of these effects were inhibited by irbesartan but not by PD 123319. Pretreatment of cardiac fibroblasts with Ang II enhanced cell attachment to ECM proteins and induced focal adhesion kinase phosphorylation. Blocking antibodies to beta(3) and alpha(v)beta(5) attenuated Ang II-induced adhesion. In SHR, ventricular alpha(v) and beta(5) integrin expression and alpha-actinin were increased compared with those in Wistar-Kyoto rats. Although both losartan and hydralazine lowered mean arterial pressure and decreased peripheral vascular resistance, only losartan attenuated the increased integrin, alpha-actinin, fibronectin laminin, and osteopontin expression and the increased left ventricular mass (as determined with echocardiography). Hydralzine had none of these effects. Although both agents attenuated beta-myosin heavy chain expression, a marker of hypertrophy, losartan had a greater effect. These results suggest that integrins and alpha-actinin are upregulated by Ang II and in left ventricular hypertrophy and that the block of expression of these proteins through inhibition of the AT(1) receptor is associated with attenuation of the hypertrophic response. Ang II induces integrin and alpha-actinin expression in cardiac fibroblasts that is associated with adhesion and left ventricular hypertrophy and blocked through inhibition of the AT(1) receptor.

A randomized trial of ecadotril versus placebo in patients with mild to moderate heart failure: the U.S. ecadotril pilot safety study

OBJECTIVE

To determine the short-term safety and tolerability of the addition of ecadotril to conventional therapy in patients with mild to moderate heart failure.

METHODS

Fifty ambulatory patients, 18 to 75 years of age, with mild to moderate heart failure, left ventricular ejection fraction </=35%, taking stable doses of angiotensin-converting enzyme inhibitor, diuretics, and optionally digoxin were enrolled in a randomized, double-blind, placebo-controlled dose-escalation study of ecadotril 50 to 400 mg twice daily versus conventional therapy alone.

RESULTS

No increases in deaths, serious adverse events, or dropouts from adverse events were observed for the ecadotril group compared with placebo. The serum measures of neurohormonal activation were highly variable. Changes in signs and symptoms of heart failure, New York Heart Association class, and patient self-assessment of symptoms were not observed with ecadotril therapy; however, the study was not designed to detect differences in these parameters.

CONCLUSION

In this small pilot study, ecadotril in doses of 50 to 400 mg twice daily was generally well-tolerated and without severe short-term adverse effects in patients with mild to moderate heart failure. Evaluation of the clinical efficacy and long-term safety of ecadotril and other neutral endopeptidase inhibitors in patients with heart failure requires further study.

The renin-angiotensin system antagonism in the treatment of hypertension

The effective treatment of hypertension is associated with improved mortality and morbidity from diseases such as stroke, congestive heart failure, and renal failure. Use of medications that target the renin-angiotensin system for the treatment of hypertension can often achieve the desired decrease in blood pressure while causing a minimum of unwanted side effects. In this paper, the principles of the renin-angiotensin system antagonism are described. The approach to using these medications is discussed with special attention to specific indications as well as common side effects.

The sympathetic nervous system and the renin-angiotensin-aldosterone system in cardiovascular disease

Both the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) have central roles in vascular adaptive processes. Stimulation of the 2 systems has been demonstrated in a range of cardiovascular disorders, including congestive heart failure and hypertension. However, elucidation regarding the interactions of the many factors involved in these 2 systems is lacking. Angiotensin-converting enzyme inhibitors have been used to reveal the contribution of some elements in the RAAS. Until relatively recently, little was known about the specific disturbances of the sympathetic nervous system in cardiovascular disease. Plasma norepinephrine levels, an indicator of sympathetic activity, have limited value because they are affected by various physiologic processes in addition to sympathetic activation. Newer approaches to the assessment of neurohormonal activity include the determination of the power content of heart-rate variability. More specific probes may lead to a better comprehension of neurohormonal physiology in health and disease and underlie future therapeutic advances targeted to prevention and treatment of specific syndromes.

Stevens-Johnson syndrome associated with carvedilol therapy

Stevens-Johnson syndrome, related to carvedilol use, has not been previously reported as a serious adverse experience requiring hospitalization. We report this reaction in a 71-year-old man with stable ischemic cardiomyopathy.

The integrated effects of angiotensin II

In recent years, a prodigious amount of information has been gathered regarding the relationship between vascular biology and the mechanisms underlying cardiovascular disease. Activation of elements of the reninangiotensin system (RAS) appear to play an important role in the development and progression of conditions such as hypertension, coronary artery disease, and heart failure. Indeed, converging lines of evidence indicate that angiotensin-converting enzyme (ACE) regulates a delicate balance among a multitude of factors responsible for vascular tone, cellular growth promotion and inhibition, and pro- and anti-inflammatory effects. Because angiotensin II inhibits fibronectin, stimulates expression of plasminogen activator inhibitors, and degrades bradykinin, thereby impairing production of nitric oxide, ACE and the RAS are also involved in thrombosis and fibrinolysis. The favorable effects of ACE inhibition on endothelial function and, potentially, on cardiovascular morbidity and mortality are believed to result not only from angiotensin II suppression but also its consequent bradykinin preservation and nitric oxide production.

Double-blind, placebo-controlled study of the effects of carvedilol in patients with moderate to severe heart failure. The PRECISE Trial. Prospective Randomized Evaluation of Carvedilol on Symptoms and Exercise

BACKGROUND

Carvedilol has improved the symptomatic status of patients with moderate to severe heart failure in single-center studies, but its clinical effects have not been evaluated in large, multicenter trials.

METHODS AND RESULTS

We enrolled 278 patients with moderate to severe heart failure (6-minute walk distance, 150 to 450 m) and a left ventricular ejection fraction < or = 0.35 at 31 centers. After an open-label, run-in period, each patient was randomly assigned (double-blind) to either placebo (n = 145) or carvedilol (n = 133; target dose, 25 to 50 mg BID) for 6 months, while background therapy with digoxin, diuretics, and an ACE inhibitor remained constant. Compared with placebo, patients in the carvedilol group had a greater frequency of symptomatic improvement and lower risk of clinical deterioration, as evaluated by changes in the NYHA functional class (P = .014) or by a global assessment of progress judged either by the patient (P = .002) or by the physician (P < .001). In addition, treatment with carvedilol was associated with a significant increase in ejection fraction (P < .001) and a significant decrease in the combined risk of morbidity and mortality (P = .029). In contrast, carvedilol therapy had little effect on indirect measures of patient benefit, including changes in exercise tolerance or quality-of-life scores. The effects of the drug were similar in patients with ischemic heart disease or idiopathic dilated cardiomyopathy as the cause of heart failure.

CONCLUSIONS

These findings indicate that, in addition to its favorable effects on survival, carvedilol produces important clinical benefits in patients with moderate to severe heart failure treated with digoxin, diuretics, and an ACE inhibitor.

Vascular hypertrophy is an early finding in essential hypertension and is related to arterial pressure waveform contour

The effects of hypertension on the arterial vasculature were examined in a study group of 20 patients with newly diagnosed essential hypertension, 18 patients with chronic essential hypertension, and 32 control subjects with normal blood pressure. Left ventricular mass was determined echocardiographically. Carotid artery intimal-medial thickness was measured by means of B-mode ultrasound imaging, and carotid arterial waveforms were obtained by applanation tonometry. Compared with that in control subjects, carotid intimal-medial thickness was increased in patients with chronic hypertension (0.74 +/- 0.17 mm vs 0.61 +/- 0.15 mm in control subjects; p < 0.01) and in patients with newly diagnosed hypertension (0.66 +/- 0.12 mm vs 0.61 +/- 0.15 mm in control subjects; p < 0.05). Left ventricular mass was also higher in patients with chronic hypertension than in control subjects but was very similar between control subjects and those with newly diagnosed hypertension. Both the group with early hypertension and the group with chronic hypertension had an increased incidence of early waveform reflection evident on carotid arterial waveform examination. By multiple regression analysis, independent predictors of increased carotid intimal-medial thickness were age, systolic arterial pressure, and Murgo class of arterial waveform. Conduit arterial wall thickening precedes left ventricular remodeling in essential hypertension and is significantly related to the degree of pressure elevation and the arterial waveform contour.

Assessment of left ventricular function by meridional and circumferential end-systolic stress/minor-axis shortening relations in dilated cardiomyopathy

Echocardiographic meridional wall stress-endocardial shortening relations provide estimates of left ventricular (LV) contractility that do not uniformly detect myocardial dysfunction despite severe symptoms in dilated cardiomyopathy. To improve detection of myocardial dysfunction in patients with congestive heart failure (CHF) due to dilated cardiomyopathy, echocardiographic meridional and circumferential end-systolic stress were related to endocardial and midwall shortening in 42 patients (95% dead within a mean of 22 months) with dilated cardiomyopathy and 140 normal subjects. A method to estimate LV long-axis dimension from M-mode minor-axis epicardial measurements was developed in a separate series of 115 subjects. Endocardial shortening to meridional wall stress relation identified 31 of 42 CHF patients falling below the 95% normal confidence interval of the reference population; use of midwall shortening decreased this number to 26 (p = NS). The use of circumferential wall stress identified 39 of 42 patients with subnormal endocardial LV shortening and 41 of 42 patients with depressed midwall performance (p < 0.01 vs use of meridional stress). The circumferential/meridional wall stress ratio was 2.6 +/- 0.5 in normal subjects and 1.3 +/- 0.2 in CHF patients (p < 0.0001). Thus, use of circumferential end-systolic stress as the measure of afterload improves the detection of myocardial dysfunction by stress/shortening relations in patients with CHF. The ratio between the 2 stresses decreases with more spherical LV shape. Midwall and endocardial shortening measurements are equivalent in the setting of thin LV walls as occurs in dilated cardiomyopathy.

Influence of pressure overload and ACE inhibitor therapy on constitutive protein mRNA expression in the spontaneously hypertensive rat

Despite use as constitutive protein standards to quantify mRNA, data are limited regarding alteration of cyclophilin or glyceraldehyde-3-phosphate dehydrogenase (G3PDH) in hypertension or angiotensin converting enzyme (ACE) inhibitor treatment. We assessed these standards in 6 month old Wistar-Kyoto rats (WKY, n = 16), compared to age-matched spontaneously hypertensive rats (SHR, n = 14). Additional SHR (n = 8) had received enalapril for 3 to 4 months at evaluation. Left ventricular (LV) and kidney RNA was extracted for dot blot cyclophilin and G3PDH cDNA hybridization. Cyclophilin and G3PDH mRNA densitometries were expressed as a ratio. Cyclophilin/G3PDH for the WKY, untreated SHR, and enalapril SHR were 1.56 +/- 0.33, 1.45 +/- 0.42, and 1.49 +/- 0.51, respectively, for the LV, and 1.52 +/- 0.09, 1.43 +/- 0.22, and 1.38 +/- 0.22, respectively, for the kidney. Differences were not significant. Relative expression of cyclophilin/G3PDH was unaffected by genetic SHR hypertension, or long term enalapril. Thus, either constitutive mRNA may be confidently used to index structural or functional protein responses, at the transcriptional level, in the SHR.

Role of spectral measures of heart rate variability as markers of disease progression in patients with chronic congestive heart failure not treated with angiotensin-converting enzyme inhibitors

Measures of heart rate variability in the frequency domain quantify autonomic activity. However, the relation of these measures to the severity of ventricular dysfunction in patients with congestive heart failure remains uncertain. We applied spectral analysis of heart rate variability to 24-hour Holter monitor recordings obtained from 20 patients with congestive heart failure who were not treated with angiotensin-converting enzyme inhibitors to determine whether significant changes in parameters of heart rate variability reflect the progression of symptoms in patients with ventricular failure. Both total and low-frequency heart rate spectral power were seen to decrease with worsening New Heart Associate (NYHA) functional class. A significant (p = 0.04) higher total power was noted in NYHA class II than in class III patients (3.0 x 10(-3) +/- 3.6 10(-4) and 2.5 x 10(-3) +/- 5.9 x 19(-4) [beats/min]2, respectively). Similarly, low-frequency heart rate spectral power was significantly (p = 0.008) higher in class II than in class III patients (1.7 x 10(-3) +/- 4.6 x 10(-4) and 1.1 x 10(-3) +/- 3.5 x 10(-4) [beats/min]2, respectively). Only the low-frequency component of the spectrum was directly correlated with left ventricular ejection fraction (LVEF) (r = 0.40) with a trend toward statistical significance (p = 0.07). Measures of heart rate variability and the changes in autonomic tone that they reflect may therefore serve as markers of the extent of disease progression in patients with congestive heart failure.

ACE inhibitors: myocardial infarction and congestive heart failure

Myocardial infarction and congestive heart failure are associated with high morbidity and mortality rates. The results of recent clinical trials support a beneficial role for angiotensin-converting enzyme (ACE) inhibitors in attenuating mortality from myocardial infarction and left ventricular dysfunction. Large-scale survival studies provide practical evidence that the addition of an ACE inhibitor to conventional therapy with diuretics and digoxin can significantly reduce the number of hospital admissions and the risk of death related to progressive heart failure.

Echocardiographic characterization of left ventricular adaptation in a genetically determined heart failure rat model

This study uses echocardiography to characterize the pattern of left ventricular hypertrophy in a new hypertensive heart failure-prone rat strain designated SHHF/Mcc-cp (SHHF). M-mode echocardiograms of the left ventricle in nine 10- to 12-month old SHHF rats and nine age-matched spontaneously hypertensive rats (SHR) were compared. Wistar-Kyoto and Sprague-Dawley strains served as the normotensive control group. SHHF rats had significantly greater left ventricular mass than did rats in the normotensive control group. Although left ventricular mass was not different between SHHF and SHR, significant differences were seen in the pattern of left ventricular remodeling as determined by relative wall thickness. These differences in left ventricular remodeling may explain the earlier development of heart failure in SHHF. The different patterns of left ventricular hypertrophy in SHHF and SHR suggests that heart failure in SHHF is not mediated by hypertension alone.

Hypertensive heart disease and heart failure

Hypertension is associated with the remodeling of left ventricular geometry and abnormalities of function that may precede geometric changes. Rather than a specific disease, "hypertensive heart failure" is a spectrum of disorders that result from left ventricular geometric changes and comorbid conditions. Heart failure may present as abnormalities of diastolic or systolic function, although symptoms (dyspnea, fatigue) and physical findings (edema, rales) may be similar.

Early left ventricular dysfunction elicits activation of sympathetic drive and attenuation of parasympathetic tone in the paced canine model of congestive heart failure

BACKGROUND

Although autonomic imbalance is known to be characteristics of patients with clinically overt symptomatic congestive heart failure, it is currently unknown whether this autonomic response arises early in the course of left ventricular dysfunction or is restricted to the later stages of circulatory failure.

METHODS AND RESULTS

This investigation utilized the technique of spectral analysis of heart rate variability in a paced canine model of congestive heart failure that permits an examination of autonomic activity at the earliest stages of ventricular dysfunction to determine whether early systolic dysfunction in congestive heart failure is characterized by autonomic imbalance, which may contribute to subsequent myocardial and vascular dysfunction. The results indicate that autonomic imbalance as reflected in an abnormal pattern of heart rate variability evolves early in the course of ventricular systolic dysfunction consisting of both a significant increase in sympathetically influenced low-frequency heart rate variability and a significant reduction of parasympathetically mediated high-frequency variability. This was quantified by a marked and significant increase in the area under the low-frequency region from 0.053 +/- 0.037 (beats per minute)2 at baseline to 0.182 +/- 0.143 (beats per minute)2 at 48 hours to 0.253 +/- 0.202 (beats per minute)2 after 7 days of pacing (ANOVA, P < .04). The area under the high-frequency region of the curve showed a decrease from a baseline value of 0.945 +/- 0.037 (beats per minute)2 to 0.811 +/- 0.152 (beats per minute)2 at 48 hours to 0.733 +/- 0.197 (beats per minute)2 after 7 days of pacing (ANOVA, P < .03). This resulted in a shift in autonomic balance away from parasympathetic tone and toward augmented sympathetic drive as reflected by the ratio of high- to low-frequency areas from a baseline value of 15.2 +/- 9.6 to 10.1 +/- 6.89 at 48 hours and 0.004 +/- 0.001 at 7 days (ANOVA, P < .01).

CONCLUSIONS

The results indicate that autonomic imbalance as reflected in an abnormal pattern of heart rate variability evolves early in the course of ventricular systolic dysfunction consisting of both a significant increase in sympathetically influenced low-frequency heart rate variability and a significant reduction of parasympathetically mediated high-frequency variability. The early appearance of these autonomic abnormalities suggests that autonomic imbalance plays a significant role in promoting the progression of circulatory failure.

Acute myocardial and vascular responses to specific angiotensin II antagonism in the spontaneously hypertensive rat

As the AT1 receptor is the primary angiotensin II receptor in the myocardium and vasculature, we assessed the acute myocardial and vascular response to the AT1 angiotensin II antagonist losartan in the spontaneously hypertensive rat (SHR) to determine the contribution of angiotensin II in this genetic form of hypertension. In a preliminary dose response study, which evaluated losartan at 1.0, 3.0, and 10 mg/kg, 10 mg/kg uniformly lowered blood pressure. In a second group of experiments, 10 mg/kg also completely attenuated the pressor effects of angiotensin II administration. In nine adult SHR, intravenous losartan, 10 mg/kg, was given, with hemodynamics measured immediately and at steady-state intervals to delineate the hemodynamic response to angiotensin II antagonism. Losartan significantly lowered systolic, diastolic, and mean blood pressures, yet heart rate was unchanged. Cardiac function, as assessed by cardiac output and blood flow acceleration, demonstrated only transient increases which were not sustained during steady-state blood pressure reduction. Significant increases of peak blood flow and pulse pressure were sustained throughout the blood pressure response. At immediate and steady-state determinations, system vascular resistance and characteristic aortic impedance were significantly reduced with losartan (both P < .01). In addition, concomitant reduction of the wave reflectance index also occurred, achieving significance at steady state (P < .05). These changes demonstrate that the AT1 angiotensin II receptor contributes to both central and peripheral vasoconstriction in the spontaneously hypertensive rat. Absence of sustained increase of cardiac output and blood flow acceleration are consistent with inhibition of the previously reported positive inotropic effect of angiotensin II.

Assessment of autonomic tone over a 24-hour period in patients with congestive heart failure: relation between mean heart rate and measures of heart rate variability

Patients with congestive heart failure (CHF) are characterized by an imbalance of the autonomic nervous system, which may contribute to the progression of circulatory failure and influence survival. However, it is still unclear whether CHF is characterized by a suppression of the diurnal variation in autonomic tone that is observed in normal subjects. To characterize the circadian variation in autonomic tone in patients with ventricular failure, ambulatory 24-hour Holter monitor recordings were obtained in 20 patients with CHF; 4-minute epochs of data from every hour of each 24-hour recording were selected. For each epoch we calculated the mean heart rate (HR) and, by applying spectral analysis of heart rate variability (HRV), we quantified the magnitude of the total (0.02 to 0.9 Hz), sympathetically governed low frequency variability (0.02 to 0.1 Hz), and parasympathetically mediated high-frequency variability (0.1 to 0.9 Hz). These areas were also expressed as a ratio to total variability and a ratio of high to low variability. A highly significant change in the mean HR over 24 hours was observed (p = 0.0001); no changes in the measures of HRV were obtained (p < 0.3). No significant correlation was found between mean HR and any frequency domain measures. We conclude that the sustained imbalance of autonomic tone over a 24-hour period, as shown by the spectral analysis of HRV, may promote the progression of circulatory failure and predispose patients with CHF to malignant ventricular arrhythmias and sudden cardiac death.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of flosequinan on autonomic tone in congestive heart failure: implications for the mechanism of the positive chronotropic effect and survival influence of long-term vasodilator administration

The vasodilator flosequinan has been shown to be effective in the management of symptoms of congestive heart failure but has been found to influence survival adversely when administered in selected doses. A moderate positive chronotropic response accompanies long-term administration of this agent, which may be associated with an activation of the neurohormonal axis that itself may contribute to the reported increase in mortality. This investigation used the technique of spectral analysis of heart rate variability to examine the autonomic response to long-term flosequinan administration in 39 patients enrolled in a double-blind placebo-controlled trial of this vasodilator to determine whether autonomic mechanisms account for the observed changes in heart rate. Although heart rate significantly increased in the flosequinan-treated patients, parasympathetic tone increased and sympathetic drive decreased compared with placebo, as reflected by high- and low-frequency heart rate variabilities, respectively. It is concluded that (1) autonomic inputs to the myocardium that would be expected to produce increases in heart rate do not result from long-term flosequinan administration; (2) accordingly, a direct positive chronotropic effect must account for the heart rate changes observed with this vasodilator; and (3) the increased mortality associated with the administration of this agent in the doses examined does not appear to result from reflex changes in autonomic tone and must result from other properties of this vasodilator.

Pulmonary hypertension and systemic hypotension as limitations to exercise in chronic heart failure

The authors have previously shown that the resistance ratio (RR) is increased in patients with congestive heart failure (CHF), and that the patients with the highest RRs have an increased mortality. The authors hypothesized that CHF patients with the lowest maximum oxygen consumption and the most impaired Weber functional classification would have the highest RR. Eighty-four patients with chronic CHF underwent seated ergometric exercise to exhaustion. Hemodynamic and respiratory gas exchange parameters were measured at rest and peak exercise. Weber functional classifications (A through E) were determined from maximum oxygen consumptions, and patients were stratified to evaluate the RR. The RR increased progressively across Weber classifications at rest (A vs E; P < .001) and with maximum exercise (A vs E; P < .002). At rest, elevation in the RR was related to an increase in the pulmonary pressure gradient (A vs E; P < .002) secondary to increased mean pulmonary arterial pressures. With peak exercise, this elevation was secondary to a decrease in the systemic pressure gradient (A vs E; P < .001). Further analysis revealed that the progressive decrease in the systemic pressure gradient was due to progressively lower mean arterial pressures (A vs E; P < .001). Elevation of the RR, both at rest and peak exercise, predicts a more impaired exercise functional status in patients with chronic CHF. Increases in the RR at peak exercise were related to decreases in mean arterial pressure, most likely limiting perfusion to exercising skeletal muscle. The mechanism of poor exercise blood pressure response in these patients is unclear. Possible explanations include abnormal systemic baroreceptor function with inappropriate vascular adaptation, and a poor cardiac output response to a relative increase in right ventricular afterload in systemic vasodilation seen with exercise.

Comparing angiotensin-converting enzyme inhibitor trial results in patients with acute myocardial infarction

Angiotensin-converting enzyme inhibitors are proved, effective agents for the treatment of hypertension and congestive heart failure. New data suggest that angiotensin-converting enzyme inhibitors may be effective therapy for patients following acute myocardial infarction. Results from clinical trials, such as the Survival and Ventricular Enlargement trial, have demonstrated that captopril attenuates left ventricular enlargement, minimizes and/or prevents the subsequent development of overt congestive heart failure, and improves survival in patients with asymptomatic left ventricular dysfunction after myocardial infarction. Clinical reinfarctions and need for subsequent revascularization procedures were also reduced with captopril. In the Acute Infarction Ramipril Efficacy study, patients with clinically evident heart failure following acute myocardial infarction who received ramipril demonstrated a significant reduction in mortality and cardiovascular events. The mortality benefit in this study was evident within 30 days, possibly reflecting differences in patients studied (ie, population with high-risk heart failure in the Acute Infarction Ramipril Efficacy study as opposed to population with asymptomatic left ventricular dysfunction in the Survival and Ventricular Enlargement trial). Contrary results have been reported in another major postmyocardial infarction trial, the Cooperative New Scandinavian Enalapril Survival Study, which evaluated enalaprilat/enalapril maleate in unselected patients with acute myocardial infarction. This article reviews the recent trials using angiotensin-converting enzyme inhibition after myocardial infarction and will explore the reasons why angiotensin-converting enzyme inhibition seems to be beneficial in this clinical setting.

Diuretic treatment for the sodium retention of congestive heart failure

The use of diuretics for the treatment of sodium retention in congestive heart failure was evaluated. Particular focus was given to the altered renal response to diuretics in patients with heart failure and adverse responses to diuretic therapy. Highlighted information included historical aspects of the development of diuretics, mechanisms of sodium retention, the physiologic and clinical response to diuretics, and the altered pharmacokinetics and pharmacodynamics of diuretics in congestive heart failure. Despite more than 60 years of empiric diuretic use in heart failure, the actual database regarding the long-term efficacy, adverse effects, and altered mortality outcome in heart failure is relatively small. Existent pharmacokinetic and pharmacodynamic data are typically not collected within the context of heart failure efficacy trials. In addition to altered electrolyte transport and total-body electrolyte depletion, diuretics may be associated with adverse neurohormonal activation. Thus, guidelines for acute and long-term therapy with diuretics in heart failure remain somewhat empiric. Diuretics will remain a mainstay for the treatment of edema in congestive heart failure but must be accompanied by moderate sodium restriction. However, large clinical trials of diuretics would be necessary to demonstrate that improved clinical efficacy with edema reduction is not offset by adverse effects, which include electrolyte depletion, ventricular arrhythmias, and subsequent increased mortality.

A gene defect that causes conduction system disease and dilated cardiomyopathy maps to chromosome 1p1-1q1

Longitudinal evaluation of a seven generation kindred with an inherited conduction system defect and dilated cardiomyopathy demonstrated autosomal dominant transmission of a progressive disorder that both perturbs atrioventricular conduction and depresses cardiac contractility. To elucidate the molecular genetic basis for this disorder, a genome-wide linkage analysis was performed. Polymorphic loci near the centromere of chromosome 1 demonstrated linkage to the disease locus (maximum multipoint lod score = 13.2 in the interval between D1S305 and D1S176). Based on the disease phenotype and map location we speculate that gap junction protein connexin 40 is a candidate for mutations that result in conduction system disease and dilated cardiomyopathy.

The clinical potential of renin inhibitors and angiotensin antagonists

The renin angiotensin system is a major contributor to the pathophysiology of cardiovascular diseases such as congestive heart failure and hypertension. For this reason, attempts to specifically block this system have been a pharmacological goal for over 25 years. Blockade of the renin system has been attempted at 3 pivotal sites: the rate limiting angiotensinogen-renin step, conversion of angiotensin I to angiotensin II, and the active receptor sites for the terminal products of angiotensin II and aldosterone. Converting enzyme inhibitors have been successfully studied and utilised in clinical cardiovascular disorders, but questions persist regarding the specificity of their action. Thus, other more specific approaches remain under evaluation. Inhibition of the action of renin on angiotensinogen was demonstrated with early inhibitory peptides and in experimental studies with specific antibodies. Most currently available renin inhibitors are nonpeptides, which nonetheless require intravenous administration. An oral renin inhibitor with clinical effects has been evaluated in early human trials. Like renin inhibitors and converting enzyme inhibitors, specific angiotensin antagonists were studied early in the course of renin system pharmacological blockade. Early angiotensin antagonists were limited, due to the requirement for intravenous administration and because of their short half-lives. They also had the potential for mixed agonist/antagonist physiological and pharmacological effects, which could result in a pressor, rather than a depressor, response. The angiotensin receptor antagonists have the appeal of blocking the specific receptor at its target tissue site, analogous to other well described systems. Newer angiotensin antagonists do not have the limitations of the precursor peptides. Losartan (DUP753) is a specific angiotensin II AT1 receptor antagonist. It is orally effective without agonist activity, and has high receptor binding characteristics. Early studies indicate that it is a specific probe of the renin system, and is providing newer insights into the role of the renin system in cardiovascular disorders. Emerging clinical studies indicate that it is effective for blood pressure reduction and as a vasodilator. Aldosterone antagonists such as spironolactone have been available for decades. Spironolactone is being used in an ongoing trial to assess the impact of combined converting enzyme and aldosterone inhibition. Newer aldosterone antagonists could add to targeted blockade of aldosterone without the adverse effects of the precursor compound, and the potential for combined specific renin system blockade.

Approaches to diuretic therapy and electrolyte imbalance in congestive heart failure

This review has summarized the current role of diuretic therapy in heart failure, emphasizing those aspects most relevant to this patient population. Recommended diuretic usage is as follows: Asymptomatic left ventricular dysfunction--establish moderate sodium intake, Mild sodium retention--thiazide-type diuretic or low-dose loop diuretic; continue moderate sodium intake; combine with an ACE inhibitor, Moderate sodium retention--loop diuretic, adjusting for renal function, if necessary; continue moderate sodium intake; combine with an ACE inhibitor, Severe sodium retention--large-dose loop diuretic combined with a thiazide-type diuretic; continue moderate sodium intake; ACE inhibitor, unless contraindicated; consider addition of a potassium-sparing diuretic Treatment measures for refractory sodium retention--intermittent intravenous loop diuretic; short-term infusion of a loop diuretic; intensified combination oral diuretic therapy; intravenous positive inotropic therapy; ultrafiltration or dialysis. In addition, the well-known adverse effect of electrolyte depletion and guidelines for electrolyte replacement have been discussed. It is evident that the diuretic class of pharmacologic therapy has not been as well assessed as both the positive inotrope and vasodilator classes. Limitations in this regard have been summarized recently. Even relatively simple parameters or instruments, such as the sodium retention score, when applied to clinical trials will yield a greater understanding of the utility and limitations of diuretic therapy for heart failure.

Increased aortic impedance precedes peripheral vasoconstriction at the early stage of ventricular failure in the paced canine model

BACKGROUND

Aortic input impedance is altered in patients with congestive heart failure. However, little is known about whether this vascular response is an early change or a late manifestation of left ventricular dysfunction.

METHODS AND RESULTS

This investigation used a paced canine model of congestive heart failure to demonstrate that abnormal aortic input impedance does evolve in the setting of ventricular systolic dysfunction and to prospectively define the time course of change in aortic input impedance and conduit vessel compliance. Studies were performed in closed-chest conditioned beagles aged 1 to 2 years that underwent hemodynamic evaluation at baseline and after induction of left ventricular dysfunction by rapid ventricular pacing. Within 48 hours of the onset of rapid ventricular pacing, we observed mild left ventricular systolic dysfunction with an echocardiographically derived left ventricular ejection fraction of 37% (p < .001 compared with baseline) measured during interruption of rapid ventricular pacing. Concomitant with this reduction in left ventricular systolic function, the aortic input impedance spectrum was shifted above baseline in all dogs studied. Characteristic impedance of the aorta significantly increased from 121 +/- 65 dynes.s/cm5 to 186 +/- 114 dynes.s/cm5 (P < .02), and a significant increase in the first modulus of impedance from 137 +/- 43 dynes.s/cm5 to 228 +/- 139 dynes.s/cm5 was observed (P < .05). Although characteristic aortic impedance increased by 50%, there was at this point no change in peripheral vascular resistance. Therefore, these abnormalities in aortic input impedance are representative of an early vascular change that evolves in response to ventricular systolic dysfunction.

CONCLUSIONS

Considering the early appearance of these findings, the resultant impaired power transfer and reduced conduit vessel compliance likely contribute to the progression of abnormal myocardial energetics and systolic dysfunction characteristic of ventricular failure.

Clinical trials of diuretic therapy in heart failure: research directions and clinical considerations

Diuretic drugs have historically been developed for the treatment of sodium and water retention in edematous disorders. The latter have traditionally been an amalgam of congestive heart failure, nephrotic syndrome, cirrhosis and chronic renal failure. With a > 50-year tradition of this approach to development, diuretic drugs have not been evaluated specifically for their safety and efficacy profile in patients with congestive heart failure. Yet, they are the most frequently prescribed drug class for this disorder. Furthermore, they remain the only drug class in congestive heart failure not subjected to large scale clinical trials. Sodium and water retention within this group of patients is related primarily to functional rather than to structural renal abnormalities. The reduction of glomerular filtration rate, increase in aldosterone secretion and abnormal profile of atrial natriuretic factor, all produce sodium retention and can be related to the severity of heart failure. Diuretic drugs have not been scrutinized in a manner similar to that of other drugs for the management of heart failure. Controversy persists regarding direct vascular effects, objective end points of assessment and the magnitude of adverse effects such as activation of neurohormonal pathways. These issues may be addressed by the establishment of reasonable objective end points, better stratification of patients in clinical trials and prospective trials in large clinical series. Even mortality studies should be considered.

Effect of standard-dose versus high-dose epinephrine on myocardial high-energy phosphates during ventricular fibrillation and closed-chest CPR

STUDY OBJECTIVE

To evaluate the effects of standard-dose versus high-dose epinephrine on myocardial high-energy phosphate metabolism during resuscitation from cardiac arrest.

DESIGN

Prospective, nonrandomized, controlled study using a swine model of cardiac arrest and resuscitation.

INTERVENTIONS

After anesthesia, intravascular pressure instrumentation, and ten minutes of ventricular fibrillation arrest, closed-chest CPR was begun. After three minutes of CPR, animals were allocated to receive either 0.02 mg/kg i.v. standard-dose epinephrine (eight) or 0.2 mg/kg i.v. high-dose epinephrine (nine). The animals underwent thoracotomy and rapid-freezing transmural myocardial core biopsy for high-energy phosphate analysis 3.5 minutes after epinephrine administration. High-energy phosphate values were blindly determined using high-pressure liquid chromatography.

RESULTS

Intravascular pressure (mm Hg) and high-energy phosphate (nmol/mg protein) results for standard-dose epinephrine versus high-dose epinephrine are, respectively, coronary perfusion pressure, 15.3 +/- 7.8 versus 23.7 +/- 5.5 (P = .0009); phosphocreatine, 0.4 +/- 0.8 versus 6.2 +/- 4.4 (P = .0003); adenosine triphosphate, 9.8 +/- 4.8 versus 12.7 +/- 5.7 (P = .30); adenosine diphosphate, 5.4 +/- 2.1 versus 6.1 +/- 1.3 (P = .41); and adenylate charge, 0.68 +/- 0.12 versus 0.72 +/- 0.12 (P = .87).

CONCLUSION

High-dose epinephrine does not deplete myocardial high-energy phosphate when given in this model of prolonged ventricular fibrillation. High-dose epinephrine increases coronary perfusion pressure compared with standard-dose epinephrine. High-dose epinephrine administration repletes phosphocreatine during closed-chest CPR, thereby increasing myocardial energy stores.

Physiological changes due to age. Implications for drug therapy of congestive heart failure

The segment of the population considered to be 'elderly' is consistently growing. At the same time, the number of patients with congestive heart failure continues to grow. Therefore, it is important to consider whether older patients with congestive heart failure have characteristics that identify an aging effect in addition to the obvious abnormalities produced by heart failure. Furthermore, it is important to determine the relevance of these abnormalities to the use of pharmacological therapy. Within a population of 128 consecutive heart failure patients, age-related increases of systemic vascular resistance, changes in baroreceptor responses, and increases of plasma noradrenaline (norepinephrine) levels were identified. In addition, an age-related reduction of renal function was clearly evident in patients > 65 years of age. These changes affect the use of digoxin, diuretics and angiotensin converting enzyme (ACE) inhibitors. Most notably, marked reduction of renal function in such patients must be considered in the drug treatment of heart failure.

Withdrawal of digoxin from patients with chronic heart failure treated with angiotensin-converting-enzyme inhibitors. RADIANCE Study

BACKGROUND

Although digoxin is effective in the treatment of patients with chronic heart failure who are receiving diuretic agents, it is not clear whether the drug has a role when patients are receiving angiotensin-converting-enzyme inhibitors, as is often the case in current practice.

METHODS

We studied 178 patients with New York Heart Association class II or III heart failure and left ventricular ejection fractions of 35 percent or less in normal sinus rhythm who were clinically stable while receiving digoxin, diuretics, and an angiotensin-converting-enzyme inhibitor (captopril or enalapril). The patients were randomly assigned in a double-blind fashion either to continue receiving digoxin (85 patients) or to be switched to placebo (93 patients) for 12 weeks. Otherwise, their medical therapy for heart failure was not changed.

RESULTS

Worsening heart failure necessitating withdrawal from the study developed in 23 patients switched to placebo, but in only 4 patients who continued to receive digoxin (P < 0.001). The relative risk of worsening heart failure in the placebo group as compared with the digoxin group was 5.9 (95 percent confidence interval, 2.1 to 17.2). All measures of functional capacity deteriorated in the patients receiving placebo as compared with those continuing to receive digoxin (P = 0.033 for maximal exercise tolerance, P = 0.01 for submaximal exercise endurance, and P = 0.019 for New York Heart Association class). In addition, the patients switched from digoxin to placebo had lower quality-of-life scores (P = 0.04), decreased ejection fractions (P = 0.001), and increases in heart rate (P = 0.001) and body weight (P < 0.001).

CONCLUSIONS

These findings indicate that the withdrawal of digoxin carries considerable risks for patients with chronic heart failure and impaired systolic function who have remained clinically stable while receiving digoxin and angiotensin-converting-enzyme inhibitors.

Sustained augmentation of parasympathetic tone with angiotensin-converting enzyme inhibition in patients with congestive heart failure

OBJECTIVES

The objective of this investigation was to evaluate the changes in parasympathetic tone associated with long-term angiotensin-converting enzyme inhibitor therapy in patients with congestive heart failure.

BACKGROUND

Angiotensin-converting enzyme inhibitors provide hemodynamic and symptomatic benefit and are associated with improved survival in patients with congestive heart failure. Angiotensin II, whose production is ultimately inhibited by these agents, exerts significant regulatory influence on a variety of target organs including the central and peripheral nervous systems. Accordingly, it would be anticipated that angiotensin-converting enzyme inhibitors would significantly alter the autonomic imbalance characteristic of patients with congestive heart failure and that this influence over neural mechanisms of cardiovascular control may significantly contribute to the hemodynamic benefit and improved survival associated with angiotensin-converting enzyme inhibitor therapy.

METHODS

In the current investigation, changes in autonomic tone associated with long-term administration of an angiotensin-converting enzyme inhibitor were measured using spectral analysis of heart rate variability in 13 patients with congestive heart failure who were enrolled in a double-blind randomized placebo-controlled trial of the angiotensin-converting enzyme inhibitor zofenopril. Both placebo and treatment groups were balanced at baseline study in terms of functional class, ventricular performance and autonomic tone.

RESULTS

After 12 weeks of therapy with placebo, there was no change in total heart rate variability, parasympathetically governed high frequency heart rate variability or sympathetically influenced low frequency heart rate variability. In contrast, therapy with zofenopril was associated with a 50% increase in total heart rate variability (p = 0.09) and a significant (p = 0.03) twofold increase in high frequency heart rate variability, indicating a significant augmentation of parasympathetic tone.

CONCLUSIONS

These results demonstrate that long-term treatment of patients having congestive heart failure with an angiotensin-converting enzyme inhibitor is associated with a restoration of autonomic balance, which derives in part from a sustained augmentation of parasympathetic tone. Such augmentation of vagal tone is known to be protective against malignant ventricular arrhythmias in patients with ischemic heart disease and therefore may have similar benefit in the setting of ventricular failure, thus contributing to the improved survival associated with angiotensin-converting enzyme inhibitor therapy in patients with congestive heart failure.

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.

Optimising ACE inhibitor therapy of congestive heart failure. Insights from pharmacodynamic studies

Pharmacokinetic studies are often used to provide additional information regarding the use of pharmacological agents for the treatment of cardiovascular disorders. Pharmacokinetic data are available for the major angiotensin converting enzyme (ACE) inhibitors. However, practical guidelines regarding dosage and dosage intervals are not feasible, and measurements of serum drug concentrations are generally not useful in practice. Such use is obscured by the nature of enzymatic inhibition, renin and angiotensin I accumulation, the complex interaction of several organ systems, the compromise of organ system function due to the heart failure process, the effect of ACE inhibitors on other vasoactive substances and the cellular actions of carboxypeptidase (the enzyme otherwise known as ACE). Pharmacodynamic data demonstrate 2 important factors that influence ACE inhibitor pharmacokinetics and serum concentrations: the aging process and abnormal renal function. As most patients with moderate to severe heart failure have reduced renal function, this has practical implications. Furthermore, heart failure is common in the elderly, and even within the population with heart failure, a superimposed further reduction in renal function can be identified in elderly patients with heart failure. Therefore, a more careful analysis of ACE inhibitor dosage must be made in the presence of decreased renal function and in the elderly patient with heart failure.

The potential role of endothelin as a vasoconstrictor substance in congestive heart failure

A rapidly growing body of data supports the concept of in situ regulation of vascular tone: the ability of vasoactive substances to regulate vascular tone at their site of production within the wall of the vasculature. Sufficient data exist to suggest that ineffective production or response to endothelium-dependent vasodilator substances, or excessive production or responsiveness to endothelium-dependent vasoconstrictor substances may play an important role in cardiovascular disorders such as hypertension, coronary artery spasm, restenosis following coronary angioplasty, and congestive heart failure. The present review summarizes data which support the concept that endothelin, a potent vasoconstrictor produced by the endothelium, may play a role in the excessive vasoconstriction of heart failure. Increased circulating plasma endothelin may be particularly relevant to the range of pulmonary vasoconstriction encountered in congestive heart failure, with a correlation revealing that the greatest increase of plasma endothelin occurs in patients with marked pulmonary hypertension within the congestive heart failure patients studied.

Cardiac secretion of atrial natriuretic factor with exercise in chronic congestive heart failure patients

We have previously reported a fivefold increase of plasma atrial natriuretic factor (ANF) in patients with congestive heart failure (CHF) compared with normal subjects. However, given the marked increase of ANF under basal conditions, the extent to which ANF secretion can further increase under physiological stress is not been clarified in CHF. We therefore evaluated ANF secretion during ergometric exercise in 11 patients with CHF, with peripheral venous ANF samples obtained at rest and peak exercise. In seven patients, simultaneous peripheral venous and right ventricular ANF samples were obtained to estimate myocardial ANF secretion. Hemodynamic characteristics of exercise included a significant increase of heart rate, mean arterial pressure, and cardiac output (all P < 0.01); reduction of systemic vascular resistance (P < 0.001); and increase of right atrial and pulmonary wedge pressures (P < 0.001). ANF was abnormally elevated at baseline (108 +/- 58 fmol/ml) yet increased further to 183 +/- 86 fmol/ml with exercise (P < 0.003). A step-up of right ventricular ANF, particularly during exercise, was consistent with active myocardial secretion, despite elevated baseline ANF levels.