Hypertonic saline is a negative inotropic agent in normovolumic dogs

The inotropic effects of hypertonic saline (HS) and hyperosmotic dextrose (HD; 2,400 mosmol/l, 4 ml/kg) were determined in normovolumic, chloralose-anesthetized, intact (n = 14) and autonomically blocked (n = 8) dogs. Solutions were infused intravenously over 3 min. HS and HD rapidly increased preload in both intact and autonomically blocked dogs, as assessed by significant (P < 0.05) increases in plasma volume, end-diastolic volume, and end-diastolic pressure. In intact dogs, HS produced a nonsignificant decrease in end-systolic elastance (Ees) and a nonsignificant increase in the maximal rate of change of left ventricular pressure (dP/dtmax) and cardiac output, whereas HD produced a significant increase in Ees, dP/dtmax, and cardiac output. In autonomically blocked dogs, HS significantly decreased Ees and significantly increased dP/dtmax but did not alter cardiac output, whereas HD significantly increased Ees, dP/dtmax, and cardiac output. We conclude that in normovolumic animals, HS is a negative inotropic agent, HD is a positive inotropic agent, and the in vivo effect of an ionic hyperosmotic agent (HS) differs from that of a nonionic hyperosmotic agent (HD).

Transesophageal echocardiographic assessment of the effects of age, gender, and hypertension on thoracic aortic wall size, thickness, and stiffness

Aging is associated with progressive arterial stiffening and widening of the pulse pressure, resulting in a high prevalence of systolic hypertension. The contribution of increased aortic thickness to this process and to essential hypertension has been poorly characterized. With transesophageal echocardiography, aortic thickness and diameter can be measured. Thus, the influence of aging, gender, and hypertension on the geometry and stiffness of the descending thoracic aorta in humans can be determined in vivo. In 83 patients undergoing transesophageal echocardiography for clinical indications, recordings of the descending thoracic aorta were made. There were 53 normotensive subjects (33 men and 20 women, mean age 46 years, range 14 to 79 years) and 25 hypertensive subjects (8 men and 17 women, mean age 67 years, range 50 to 80 years). Measurements of diastolic and systolic aortic thickness and aortic diameter were made, and three measures of the elastic properties of the aorta were calculated: (1) Peterson's elastic modulus, (2) Young's modulus, and (3) the stiffness index (beta). Aortic thickness averaged 1.1 +/- 0.1 mm in both normotensive men and women. Normotensive women had a significantly greater thickness/diameter ratio than men (0.06 +/- 0.01 vs 0.05 +/- 0.01, p < 0.01), but there were no differences in stiffness between men and women. Age was highly positively correlated with thickness (r = 0.74, p < 0.001), diameter (r = 0.67, p < 0.001), beta (r = 0.79, p < 0.001), Peterson's modulus (r = 0.78, p < 0.001), and Young's modulus (r = 0.81, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

The significance and prevention of air emboli with the total artificial heart

Embolism remains a significant complication of the total artificial heart (TAH). The ineffectual deairing of the TAH can allow embolization of the retained air. The standard needle aspiration of TAH air (Group A) was compared with a new protocol (Group B) that included standard needle TAH aspiration plus simultaneous pumping of the TAH against an occluded ascending aorta and main pulmonary artery with vacuum applied to a needle in the proximal aorta and pulmonary artery. There were 4 calves in each group. There was no premortem evidence of systemic or pulmonary emboli. Both groups of animals were electively terminated less than 2 weeks postoperatively Postoperative mean aortic and pulmonary artery pressures were recorded for each animal. Animals in Group B had a significant decline in pulmonary artery pressures (43 +/- 12 vs. 33 +/- 8 mm Hg) 1 h after TAH implantation when compared with Group A. All other aortic and pulmonary artery pressure differences between Groups A and B were not statistically significant within 24 h of the operation. Group A animals had a 75% incidence, and Group B animals had 100% incidence of TAH thrombus. This very small thrombus was found exclusively at the inflow valve-TAH housing interface. Evaluation of the kidneys postmortem was used to identify embolic injury. All animals in Group A had evidence of acute, hemorrhagic injury, but none of the Group B animals had similar injury. Half of the animals in each group had small, fibrotic chronic renal cortical injury, which did not develop during TAH implantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic evaluation of pulmonary artery distensibility

The aim of this study was to verify the hypothesis that pulmonary artery (PA) distensibility may modify the pattern of right ventricular ejection. Pulmonary artery distensibility was evaluated with M-mode measurements of right pulmonary artery diameter from suprasternal notch simultaneous with pulmonary pressure measurements. Pulmonary artery pressure was measured in 19 subjects, 29 to 75 years old (mean age, 49 years). Pulmonary artery systolic pressure was 22 to 108 mm Hg (mean, 52 mm Hg). Pulmonary artery pressure strain modulus (Ep) was calculated as follows: PADD x (PASP-PADP)/PADD-PADS (PADS-PA diameter in systole, PADD-PA diameter in diastole, PASP-PA systolic pressure, PADP-PA diastolic pressure) was 6 +/- 8 10(5) dynes/cm2. Right ventricular outflow tract velocity was recorded with pulsed Doppler echocardiography and acceleration times (AT) and ejection times (ET) were measured. Log Ep was correlated with pulmonary artery systolic and mean pressure (r = 0.90 and r = 0.87, p < 0.0001) but not with age (r = 0.30, p = NS). Acceleration time and AT/ET ratio were correlated with log Ep (r = 0.73 and r = 0.76, p < 0.001) and with pulmonary artery mean pressure (r = 0.91 and r = 0.89, p < 0.0001). When pulmonary artery pressure was included in multiple analyses, the relationships between Doppler indices and elastic modulus did not prove to be significant. These findings emphasize the independence of Doppler right ventricular outflow tract velocity indexes used for noninvasive evaluation of pulmonary hypertension from pulmonary artery distensibility in a clinical setting.

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.

Thermodilution measures of right ventricular ejection fraction and volumes in heart transplant recipients: a comparison with radionuclide angiography

A reliable, convenient measure of right ventricular ejection fraction may be a useful adjunct to evaluate cardiac allograft rejection. The purpose of this investigation was to compare two measures of right ventricular ejection fraction: (1) radionuclide angiography with the first-pass technique and (2) thermodilution with a balloon flotation catheter. The study was performed in 26 heart transplant recipients; hemodynamics, thermodilution cardiac output, and right ventricular ejection fraction were measured. First pass radionuclide angiography was performed either simultaneously (n = 11) or within 4 hours (n = 15) of the thermodilution study. Mean thermodilution right ventricular ejection fraction was 39% +/- 8%, and radionuclide angiography ejection fraction was 47% +/- 9%, which represents a highly significant difference (p < 0.001) in techniques. Linear regression showed no correlation between the two techniques (r = 0.3; p = NS). No differences in results were observed in those studied simultaneously versus less than 4 hours. We conclude that the thermodilution technique underestimates right ventricular ejection fraction in heart transplant recipients and that its usefulness as a tool to screen for systolic dysfunction related to rejection is limited.

Remnant atrial function in human and animal recipients of a total artificial heart

The native atria remains intact after total artificial heart (TAH) implantation. The electrical activity of the recipient's atria can be recorded from wires placed during TAH implantation. Regulating TAH heart rate by coupling it with native atrial activity has the potential for a more physiologically responsive TAH. The reactivity of the atrial impulse rate is a critical component of this link, but little is known about atrial responsiveness after TAH placement. Two human and three animal TAH recipients had recordable atrial electrical activity. Human atrial impulse rate after TAH was relatively constant at rest but unresponsive to physiologic stimuli. Analysis of human atrial contraction provided no discernable effect on ventricular filling. Animal atrial impulse rate at rest was more rapid than calves without a TAH. The bovine TAH recipients had an atrial impulse rate that responded to catecholamine stimulation and blockade. Isoproterenol caused a significant rise in atrial impulse rate (152 +/- 16 impulses per minute to 216 +/- 24 impulses per minute; p < 0.05) and propranolol caused a decrease in atrial impulse rate (142 +/- 20 impulses per minute to 122 +/- 19 impulses per minute; p > 0.05). Despite beta blockade, the atrial impulse rate remained abnormally elevated secondary to unknown factors. Animal atrial contraction did appear to intermittently augment TAH ventricular filling. These data indicate that the atria remains electrically intact after TAH implantation. The human atrial impulse rate was unresponsive to physiologic stimuli although the animal atrial impulse rate was affected by exogenous catecholamine administration, but the rate remained abnormally rapid.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical pharmacology of nicorandil in patients with congestive heart failure

Nicorandil is a nicotinamide derivative with a potential role in human therapeutics because of its potent vasodilating properties. The pharmacokinetics of oral nicorandil administration and the relationships between plasma nicorandil concentration and hemodynamic responses were examined in 25 patients with moderate to severe congestive heart failure. The dose range from 10 to 60 mg was studied. Elimination half-life for this dose range was substantially longer than that previously reported in normal volunteers. Total area under the curve increased in a curvilinear fashion with progressive dose increments, indicating a disproportionate increase in systemically available drug at higher doses. Hemodynamic responses generally correlated well with plasma nicorandil concentration, with rapid loss of cardiovascular activity corresponding to the efficient clearance of nicorandil.

Evaluation of aortic distensibility with transesophageal echocardiography

Distensibility of the descending aorta was evaluated during routine transesophageal echocardiography (TEE) in 50 subjects (16 to 80 years, average age 53). M-mode measurements of aortic systolic (SD) and diastolic diameter (DD) were taken distal to the left subclavian artery. Simultaneously, cuff brachial artery systolic (SBP) and diastolic (DBP) pressures were measured. Aortic pressure strain modulus (Ep), calculated as brachial artery pulse pressure/aortic strain, averaged 1.19 +/- 0.95 10(6) dynes/cm2. Elasticity index beta, defined as 1n (SBP/DBP)/aortic strain, averaged 3.77 +/- 2.12. Both Ep and beta were correlated with age (r = 0.65, p less than 0.001; and r = 0.70, p less than 0.0001). In 20 subjects aortic pulse wave velocity was assessed at the same time using simultaneous high fidelity recordings of carotid and femoral artery pressure waveforms. Aortic pulse wave velocity averaged 818 +/- 231 cm/sec and was correlated with Ep (r = 0.60, p less than 0.01) and with age (r = 0.55, p less than 0.05). Intraobserver and interobserver variability for aortic diameter measurement ranged from 0.2 to 0.5 mm.

Plasma endothelin correlates with the extent of pulmonary hypertension in patients with chronic congestive heart failure

BACKGROUND

Endothelin is a family of potent vasoconstrictor peptides of vascular endothelial origin. Although it has been proposed that the vasoconstrictor effects of endothelin are produced at the local vascular level, increased plasma concentration of endothelin has been identified in cardiovascular disorders.

METHODS AND RESULTS

We tested whether immunoreactive endothelin-1 could be detected by radioimmunoassay in plasma of congestive heart failure patients and whether levels correlated with hemodynamic characteristics. Twenty congestive heart failure patients (New York Heart Association class II-IV) were sampled in the morning after an overnight fast, before medication. Cardiac index was decreased to 2.14 +/- 0.45 l/m/m2, and pulmonary wedge pressure was increased to 22 +/- 7 mm Hg. The ranges of pulmonary pressures were: systolic, 22-100 mm Hg, mean, 13-61 mm Hg, and diastolic, 8-42 mm Hg. The endothelin-1 level was 9.07 +/- 4.13 pg/ml (range, 4-19 pg/ml), which was increased compared with 12 normals (3.7 +/- 0.6 pg/ml; range, 2.8-4.7 pg/ml); the difference was statistically significant (p less than 0.0001). Endothelin-1 significantly correlated with pulmonary pressures (systolic, r = 0.78; mean, r = 0.80; diastolic, r = 0.77; all p less than 0.003) and pulmonary vascular resistance (r = 0.65, p less than 0.01). Endothelin-1 strongly correlated with the resistance ratio (pulmonary vascular resistance/systemic vascular resistance) (r = 0.88, p less than 0.0001). Stepwise multiple regression analysis confirmed the significance of these observations.

CONCLUSIONS

Elevated immunoreactive endothelin-1 specifically correlated with the extent of pulmonary hypertension in congestive heart failure patients. Whether endothelin-1 is a regional mediator of pulmonary hypertension or a marker for its occurrence requires additional evaluation.

Dobutamine increases cardiac output of the total artificial heart. Implications for vascular contribution of inotropic agents to augmented ventricular function

BACKGROUND

The synthetic catecholamine dobutamine increases stroke volume in normal subjects and in patients with congestive heart failure. In addition to its direct influence on myocardial contractility, dobutamine may significantly modulate vascular tone because of its alpha- and beta-adrenergic agonist activity.

METHODS AND RESULTS

To test the hypothesis that such vasoactive properties significantly contribute to the improved ventricular performance noted with this agent, hemodynamic parameters were measured during stepped ascension infusion of dobutamine in a model that is insensitive to positive inotropic stimulation. Administration of dobutamine in nine calves that underwent replacement of the native right and left ventricles with pneumatically driven total artificial hearts resulted in a significant (p = 0.0001) increase in cardiac output from 7.0 +/- 1.8 to 8.2 +/- 1.8 l/min and a significant (p = 0.0001) decrease in total peripheral vascular resistance from 1,224 +/- 559 to 745 +/- 317 dyne.sec/cm5. A less marked influence was noted on the pulmonary vasculature, with pulmonary vascular resistance exhibiting a significant (p less than 0.05) decrease from its baseline value only at the peak infusion. Consistent with an increase in venous return, both left and right atrial pressures increased significantly (p less than 0.005) with dobutamine administration.

CONCLUSIONS

These data demonstrate that the vasoactive properties of dobutamine significantly contribute to improved ventricular performance independent of direct myocardial stimulation. This effect appears to result in part from a direct modulation of myocardial stimulation. This effect appears to result in part from a direct modulation of arterial and venous tones rather than from a reflex response to primary changes in contractility.

Parasympathetic withdrawal is an integral component of autonomic imbalance in congestive heart failure: demonstration in human subjects and verification in a paced canine model of ventricular failure

Although enhanced sympathetic tone is a well recognized component of the autonomic profile characteristic of congestive heart failure, the contribution of parasympathetic withdrawal to this autonomic imbalance is less well described. The technique of spectral analysis of heart rate variability provides a dynamic map of sympathetic and parasympathetic tone and was thus used to define the nature of sympathetic-parasympathetic interactions in humans with idiopathic dilated cardiomyopathy and in a paced canine model of congestive heart failure. Humans with cardiomyopathy were found to have an augmentation of the sympathetically mediated low frequency area of the power density spectrum. Parasympathetic withdrawal was demonstrated by significant reductions in the parasympathetically mediated high frequency area (p less than 0.05) and the ratio of high to low frequency areas (p less than 0.01). Administration of atropine to normal subjects resulted in a significant reduction in the high frequency area (p less than 0.05) and the high/low frequency area ratio, both of which decreased within the range noted in patients with congestive heart failure. Administration of isoproterenol in normal subjects led to an augmentation of the low frequency area but to only a small decrease in the high/low frequency area ratio. Induction of congestive heart failure in a paced canine model resulted in alterations in the autonomic profile that resembled those seen in humans with ventricular failure. The prominent high frequency region of the spectrum at baseline, indicating a predominance of parasympathetic tone, was absent after the evolution of congestive heart failure, and there was a marked augmentation of the low frequency region of the spectrum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine nucleotide content in cold preserved human donor hearts and subsequent cardiac performance after orthotopic heart transplantation

Myocardial high-energy phosphate content has been used as a parameter to evaluate the adequacy of donor organ preservation. The purpose of this study was to assess current techniques of preservation by measuring high-energy phosphates in cold preserved (4 degrees C) human donor hearts. Endomyocardial biopsy samples of the donor heart right ventricular septum (n = 24) were compared with samples from patients with normal cardiac function evaluated before chemotherapy (n = 12). Left ventricular and right ventricular ejection fractions were measured by means of radionuclide angiography early (24 to 72 hours) and late (mean 42 days) postoperatively. Mean total cold ischemic time was 146 +/- 54 minutes (range, 89 to 340 minutes). ATP nmol/mg noncollagenous protein in donor hearts was 38.2 +/- 10.7 and 31.9 +/- 13.6 (p = NS) in normal hearts. Early postoperative left ventricular and right ventricular ejection fraction was 55% +/- 14% and 40% +/- 9%, respectively. Late postoperative left ventricular and right ventricular ejection fraction was 64% +/- 14% and 50% +/- 10%, respectively; both represent significant increases in right and left ventricular ejection fraction (p less than 0.05). No correlation was found between ischemic time and donor ATP, ischemic time and ejection fraction, or ejection fraction and ATP. Three patients with normal donor heart ATP content had severe, but reversible, early graft dysfunction. In summary, currently used human donor heart preservation techniques are associated with normal values of high-energy phosphates and usually excellent early and late postoperative graft function.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute positive inotropic intervention: the catecholamines

The catecholamines remain a major therapeutic group in intensive cardiac care; this group of compounds evokes a positive inotropic response and vascular effects ranging from vasoconstriction to little net effect to vasodilatation. Hemodynamics and clinical guidelines now allow a proper selection of the optimal catecholamine. Additional mechanisms of action and a better understanding of the clinical application of this important drug group are continuing to unfold.

Platypnea-orthodeoxia: an unusual indication for surgical closure of a patent foramen ovale

Platypnea-orthodeoxia is an infrequently reported clinical form of position dependent dyspnea and oxygen desaturation. There are several diverse etiologies for this syndrome. This case report of a patient with platypnea-orthodeoxia is the first known presentation of a case secondary to a patent foramen ovale and idiopathic hemidiaphragm paralysis. A major problem with this disease is the clinical recognition of its existence. Full recovery is possible with proper assessment of clinical signs and symptoms, appropriate noninvasive diagnostic tests, and corrective surgery in selective cases.

Clinical significance of terminal QRS abnormalities in the setting of inferior myocardial infarction

To ascertain the clinical relevance of terminal electrocardiographic (ECG) QRS prolongation in the setting of inferior myocardial infarction, 32 patients were studied by radionuclide ventriculography to evaluate regional left ventricular contractility. Of the 32 patients, 16 had evidence of terminal QRS prolongation and notching associated with inferior myocardial infarction, and 16 had isolated ECG evidence of inferior myocardial infarction without terminal QRS prolongation. The regional ejection fraction in the posterolateral and inferoapical regions of patients with terminal conduction delay was lower than those without this conduction delay. This group also demonstrated a lower global ejection fraction than those patients with ECG evidence of inferior myocardial infarction without terminal QRS changes. Terminal QRS abnormalities are important qualitative predictors of left ventricular dysfunction in the setting of inferior myocardial infarction.

Comparison of hypersensitivity to adrenergic stimulation after abrupt withdrawal of propranolol and nadolol: influence of half-life differences

To test whether a beta-blocker's pharmacokinetics has an effect on the development of the beta-blocker withdrawal syndrome, we compared response to exercise and isoproterenol after abrupt withdrawal of two beta-blockers, one with a short half-life (propranolol) and one with a long half-life (nadolol). Eight normal males participated in the randomized cross-over trial. They took propranolol, 40 mg every 6 hours for 6 days, and nadolol, 80 mg daily for 7 days. Exercise- and isoproterenol-induced changes in heart rate and pulse pressure were significantly less than control values during treatment with both drugs (p less than 0.05). Significant hypersensitivity of heart rate response was seen on days 2, 3, and 7 after propranolol withdrawal (p less than 0.05) and on day 6 after nadolol withdrawal (p less than 0.005). Hypersensitive responses to isoproterenol were seen after propranolol withdrawal; no evidence of hypersensitivity to isoproterenol was seen after nadolol withdrawal. The area under the heart rate response, time curve after nadolol withdrawal was significantly less than that after propranolol withdrawal (20.3 beats/min.day vs 44.9 beats/min.day, respectively, (p less than 0.05). There was a significant inverse correlation between the degree of hypersensitivity and nadolol pharmacokinetic half-life (r = -0.80, p less than 0.02). We conclude that abrupt withdrawal of a beta-blocker with a long half-life may protect against the development of the beta-blocker withdrawal syndrome.

Comparison of single-dose and steady-state nadolol plasma concentrations

The pharmacokinetics of nadolol have been previously reported to be linear between single and steady-state dosing. Data from a study in our laboratory suggested greater than expected beta-blockade with nadolol at steady state. Because the early potency studies were single-dose studies, we hypothesized there was a nonlinearity in nadolol pharmacokinetics which produced higher than expected plasma concentrations at steady state. Six normal volunteers from the previous study (steady state) volunteered to participate in the single-dose study. Plasma concentrations were determined for 24 hr following a single dose of nadolol, 80 mg. A simple, inexpensive, and accurate method for determination of nadolol in plasma or serum by HPLC with fluorometric detection is described. The AUC0-tau at steady state was greater than the AUC0-infinity following a single dose in five of the six subjects. The mean ratio of AUCss/AUCsd was 2.54. This value would be unity in the presence of linear pharmacokinetics. We conclude that the principle of superposition is not applicable for nadolol.

Alpha-adrenergic component of the sympathetic nervous system in congestive heart failure

The alpha-adrenergic component of the sympathetic nervous system plays a major role in the pathophysiology, clinical manifestations, and natural history of human congestive heart failure. While the augmentation of alpha-adrenergic tone (through the neuronal release of norepinephrine) is a valuable mechanism to maintain adequate systemic blood pressure and perfusion of vital organs in states of circulatory collapse, stimulation of alpha-adrenergic receptors produces detrimental hemodynamic effects in congestive heart failure. These undesirable effects result from alpha-mediated vasoconstriction and consist of excessive elevation of right and left ventricular filling pressures and pulmonary and systemic vascular resistances. The enhancement of alpha-adrenergic tone preferentially reduces blood flow to the hepatosplanchnic circulation. Many of the hemodynamic responses that are seen after activation of the renin-angiotensin system are related to the ability of angiotensin II to amplify the actions of the alpha-adrenergic system. Stimulation of myocardial alpha-adrenergic receptors in most species elicits a modest positive inotropic effect, but the presence and importance of this property in the human heart remains controversial. Chronic stimulation of myocardial alpha-adrenergic receptors may result in the hypertrophy of cardiomyocytes and may also contribute to the development of catecholamine-induced cardiomyopathy. Acute blockade of the heightened alpha-adrenergic tone in congestive heart failure (e.g., with first doses of prazosin) results in favorable hemodynamic effects, but repeated dosing leads to pharmacological tolerance. Consequently, the long-term administration of alpha-adrenergic blocking agents in human heart failure has not been accompanied by an improvement in clinical status, exercise capacity, or survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of oral nicorandil in congestive heart failure

Twenty-five patients with congestive heart failure (CHF) underwent a double-blind randomized study of the acute hemodynamic effects of orally administered nicorandil, a newly developed vasodilator drug. A dose range of 10 to 60 mg was studied. Nicorandil, at a dose of 60 mg, caused statistically significant decreases in systemic systolic and diastolic blood pressure, right atrial pressure, pulmonary capillary wedge pressure, systemic and pulmonary vascular resistance and systolic and diastolic pulmonary arterial pressure. A brief increase in cardiac index attributable to an increase in stroke volume without a change in heart rate was also observed. A dose of 40 mg produced similar results in cardiac index and systemic and pulmonary vascular resistance, but changes in other hemodynamic parameters were much smaller in magnitude and usually not of statistical significance. No significant hemodynamic response was seen to doses of 10 and 20 mg of nicorandil. Duration of action was short with nearly all hemodynamic parameters returning close to baseline within 3 hours. This rapid decrease in activity occurred in concert with a rapid plasma clearance of nicorandil as determined by serial measurements of plasma drug concentration. This study suggests that first-dose orally administered nicorandil elicits favorable, but brief, hemodynamic effects in CHF at doses greater than or equal to 40 mg.

Influence of positive inotropic therapy on pulsatile hydraulic load and ventricular-vascular coupling in congestive heart failure

The aortic input impedance spectrum provides a description of the total hydraulic load imposed on the left ventricle and may be used to assess the coupling of the ventricle to the vasculature. The adaptation of the vasculature to positive inotropic intervention was examined in 10 patients with idiopathic dilated cardiomyopathy to test the hypothesis that increased myocardial contractility is matched by complementary changes in aortic impedance that optimize ventricular-vascular coupling and maximize power transfer to the circulation. High fidelity intravascular recordings of aortic pressure and flow were obtained at baseline study and during infusion of dobutamine to derive the aortic input impedance spectrum. In eight patients in whom increased staged infusion of dobutamine resulted in a significant increase in stroke volume (22.3 +/- 14.5 ml/beat increase over baseline), the significant (p less than 0.05) increase in the maximum of the first derivative left ventricular pressure pulse (dP/dt) was accompanied by significant decreases in characteristic impedance of the aorta (138 +/- 88 to 92 +/- 44 dyne.s.cm-5) wave reflection index (238 +/- 144 to 109 +/- 59 dyne.s.cm-5), and low frequency moduli of impedance. Effective positive inotropic therapy with dobutamine in the setting of congestive heart failure is accompanied by complementary changes in the aortic impedance spectrum, which represent a matching of impedance to the increased contractile state of the ventricle and facilitation of ventricular-vascular coupling.