In vivo identification and distribution of alpha- and beta-adrenoceptors in rat heart and lung

Uptake of 3H-prazosin (3H-PZ), a potent alpha-adrenoceptor antagonist, and 3h-dihydroalprenolol (3H-DHA), a potent beta-antagonist, was measured in rat heart and lung after intravenous injection. 3H-PZ binding was inhibited in a dose-dependent manner by phentolamine with maximum displacement at 5 mg/kg which represented 50-70% of the total binding. 3H-DHA was inhibited by increasing doses of l-propranolol with maximum displacement at 1 mg/kg (30-70% of total binding), whereas d-propranolol was approximately 100 times less potent, confirming stereospecificity of binding. These radioligands appeared to label adrenoceptors in vivo. The distribution of both radioligands in heart, lung and blood vessels was investigated.

Safety of electrical cardioversion in patients without digitalis toxicity

To ascertain whether electrical cardioversion increases ventricular ectopy in patients receiving nontoxic doses of digitalis, we recorded continuous electrocardiograms in 21 patients for at least 1 hour before and immediately after direct-current countershock. Seventeen patients also received specific antiarrhythmic therapy. There were no consistent differences in the frequency of severity of ventricular ectopy before and after cardioversion despite a wide range of serum digoxin levels (0.1 to 3.0 ng/mL; mean, 1.6 ng/mL). No patient had ventricular tachycardia after cardioversion, and all eight patients with serum digoxin levels greater than 2.0 ng/mL had the same or fewer ventricular ectopic beats per hour and the same or lower ectopy grades after cardioversion when pre- and postshock recordings were compared. These findings suggest that patients receiving digoxin without clinical evidence of digitalis toxicity are at low risk for serious postcardioversion ventricular arrhythmias, even when serum digoxin levels are modestly elevated. The extent to which this low risk is due to concomitant antiarrhythmic therapy is unknown

Assessment of isovolumic and ejection phase indices of left ventricular performance

Variables derived from isovolumic phase pressure tracings and from the characteristics of wall shortening during ejection may be used for defining the basal levels of contractility in normal subjects and in patients with cardiac disease. The problem of identifying an acute change in contractility appears to be relatively straightforward, and both isovolumic and ejection phase indices of left ventricular performance seem to be useful for detecting such acute alterations. Under chronic conditions, however, the heart may compensate for long-term stress by hypertrophy, dilatation and maximum use of the Frank-Starling reserve mechanism. Geometrical and wall thickness changes may serve to maintain preload and afterload relatively constant, and if basal contractility is maintained, myocardial performance per unit of circumference during ejection will remain normal. Isovolumic indices, which are derived from the preejection phase of contraction, are relatively insensitive measures of left ventricular performance. Therefore, when myocardial contractility becomes depressed in the basal state, the isovolumic indices may not detect the inability of the heart to sustain performance and in these circumstances it seems preferable to measure shortening characteristics in order to detect the depressed level of contractility. This concept may provide at least a partial explanation of why ejection phase indices have proved more reliable than isovolumic measures for detecting reduced contractility in the basal state.

Enhanced noradrenaline response in cardiomyopathic hamsters: possible relation to changes in adrenoceptors studied by radioligand binding

To assess the possible relation between catecholamine responses and adrenoceptor affinity and density, we compared the effect of noradrenaline, isoprenaline and ouabain on the right ventricular muscle strips from normal and cardiomyopathic hamsters with alpha 1- and beta-adrenoceptor characteristics assessed by radioligand binding methods. At concentrations of 1.28, 2.56, 5.0 and 10 x 10 (-6) mol . litre (-1) noradrenaline raised isometric tension by 27 +/- 4, 39 +/- 5, 52 +/- 5 and 61 +/-6% in normal animals (n = 6). Corresponding increase of 65 +/- 8, 92 +/- 8, 109 +/- 9 and 115 +/- 10% occurred in cardiomyopathic hamsters (n=11, all P less than 0.02). The responses to isoprenaline (Emax =82%) and ouabain did not differ between the two groups of hamsters. [3H]-prazosin, a new radioligand, and [-3H]-dihydroalprenolol were used to assess alpha 1- and beta-adrenoceptors in cardiac membranes. By Scatchard analysis, the KD values for both ligands did not differ between normal and cardiomyopathic hamsters, but the maximum number of binding sites was higher in the myopathic group: 5.5 vs 3.9 fmol . mg [-1] protein for [3H]-prazosin and 27 vs 20 fmol . mg [-1] protein for [-3H]-dihydroalprenolol (both P less than 0.05). Histochemically, oxidative and glycolytic activity were normal but lysosomal acid phosphatase was high. Possible explanations for the raise response to noradrenaline in cardiomyopathic hamster include and increased concentration of noradrenaline in the synaptic cleft due to defective neuronal uptake and / or stimulation of an augmented population of alpha 1-(postsynaptic) adrenoceptors.

The creatine kinase curve area and peak creatine kinase after acute myocardial infarction: usefulness and limitations

We determined creatine kinase (CK) curve areas in 112 patients with acute myocardial infarction. Two-hour sampling was performed for the first 24 hours or until peak CK was reached, and a gamma density function was used to calculate curve areas from all available samples. Attempts to predict CK curve area by means of the portion of the curve prior to peak CK proved to be inaccurate; not until values 2 hours or more beyond peak CK were utilized did predicted and actual CK areas agree well. A good correlation (r = 0.93) was found between CK area and peak CK. To establish an approach for detecting peak CK in the clinical setting, a range of sampling intervals (4 to 24 hours) was assessed; 4- and 6-hour sampling intervals for 48 hours produced maximum CK values at or above 85% of true peak CK in 90% and 89% of patients, respectively, and average maximum CK at both sampling intervals exceeded 94% of that obtained with 2-hour samplings. We conclude that this simplified approach can provide a basis for estimating infarct severity in the individual patient.

Chronic heart failure in the guinea pig increases cardiac alpha 1- and beta-adrenoceptors

Compared with sham-operated guinea pigs, chronic heart failure produced by aortic constriction resulted in a 79% increase in alpha 1-adrenoceptor density as measured by [3H]prazosin binding (73 +/- 15 vs. 131 +/- 20 fmol/mg protein, P < 0.05); beta-adrenoceptor number, measured by (-)-[3H]dihydroalprenolol binding, increased by 93% (28 +/- 3.4 vs. 54 +/- 5.2 fmol/mg protein, P < 0.01). For each radioligand KD values were unchanged. Thus, congestive heart failure due to chronic pressure overload results in compensatory augmentation of alpha 1- and beta-adrenoceptor numbers.

First-third ejection fraction at rest compared with exercise radionuclide angiography in assessing patients with coronary artery disease

To compare two methods of evaluating patients with coronary artery disease, the authors assessed the ejection fraction (EF) during the first-third (1/3) of systole by first-pass radionuclide angiography and the EF response to exercise in 22 normal individuals and 40 patients. The 1/3 EF was calculated by averaging 3--5 beats on the time--activity curve. Exercise EFs were obtained by gated cardiac imaging. The results are shown below, including the per cent change in EF with exercise (% EF). (Formula: see text) p less than 0.05 vs. normals; p less than 0.001 vs. normals; all results are +/- SD. Thirty per cent of patients had a depressed EF, 98% had a depressed 1/3 EF, and 88% had an abnormal EF response to exercise. It is concluded that the 1/3 EF by first-pass radionuclide angiography at rest may be at least as sensitive in identifying patients with coronary artery disease as the EF response to exercise.

Human lung adrenoreceptors studied by radioligand binding

1. Direct radioligand-binding techniques have been used to characterize and quantify adrenoreceptors in human peripheral lung tissue removed at thoracotomy from ten patients, nine of whom had evidence of obstructive airways disease. 2. [3H]Dihydroalprenolol was used to characterize beta-adrenoreceptor sites and [3H]prazosin to identify alpha-adrenoreceptor sites. Binding of both ligands showed saturability, high affinity, rapid kinetics, reversibility and stereospecificity. The rank order of agonists and antagonists inhibiting specific binding correlated well with known physiological potencies. Specificity of [3H]dihydroalprenolol binding suggested that the population of lung beta-adrenoreceptors is predominantly of the beta 2 subtype.

Enhanced left ventricular shortening during chronic volume overload in conscious dogs

Prior work with the arteriovenous fistula model indicates that left ventricular performance is at least normal and may be enhanced during chronic volume overload. The present study was undertaken in conscious dogs to determine whether ejection-phase indices of ventricular function are enhanced after 1 mo of volume overload, using an experimental design in which loading conditions could be accounted for and animals were used as their own controls before and after volume overload. We also examined the response of the volume-overloaded left ventricle to an afterload stress and the role of adrenergic stimulation in maintenance of function. Both at rest and during hemodynamically matched conditions, percent shortening (ultrasonic dimension gauges) and mean shortening rates were increased during volume overload. This difference was maintained during phenylephrine-induced blood pressure elevation, although diastolic dimensions increased more in control studies during phenylephrine. Propranolol produced significantly larger reductions in these indices during volume overload than in the control state. Thus, ejection-phase function is enhanced during volume overload, at least in part due to increased adrenergic stimulation.

Right and left ventricular dysfunction in patients with chronic obstructive lung disease. Assessment by first-pass radionuclide angiography

To evaluate the relationship between right and left ventricular function in patients with obstructive lund disease, we studied 10 normal subjects (group 1) and 37 patients with chronic obstructive pulmonary disease by first pass radionuclide angiography. These 37 patients were divided into three groups: nine with mild chronic obstructive pulmonary disease (group 2), 20 with severe chronic obstructive pulmonary disease (group 3) and eight with severe chronic obstructive pulmonary disease and primary left ventricular disease (group 4). In each subject right ventricular ejection fraction (RVEF), left ventricular ejection fraction (LVEF) and ejection fraction during first third of systole (first third LVEF) were calculated. (For table: see text.) p less than 0.05 versus 1. All subjects in group 2 had normal left ventricular and right ventricular function. In group 3, 11 of 10 (55 per cent) had a low RVEF and three of 20 (15 per cent) a low LVEF. However eight of 20 in this group (40 per cent) had a depressed first-third LVEF. The correlation between decline in RVEF and first-third LVEF was good r = 0.73. We conclude that (1) certain indices of early systolic left ventricular ejection are abnormal in many patients with chronic obstructive pulmonary disease and correlate with the decline in right ventricular function; (2) this is not seen in patients with mild chronic obstructive pulmonary disease and is worse in patients with underlying left-sided heart disease.

Effects of morphine on left ventricular dimensions and function in patients with previous myocardial infarction

To assess the effects of morphine sulfate on left ventricular function and dimensions we administered 15 mg of this agent to 11 stable patients with previous transmural myocardial infarction. All studies were carried out in the supine position. Before morphine administration an echocardiogram was obtained, and this procedure was repeated at 15, 30, 60, 120, and 240 min after morphine. Heart rate decreased from a control value of 69 +/- 4 to 62 +/- 5 beats/min 2 h after morphine (p less than 0.01, analysis of variance); this slower heart rate persisted for 4 h after morphine. Serial measurements of blood pressure, echocardiographic ejection fraction, percent of fractional shortening, and mean normalized velocity of circumferential fiber shortening also showed no significant alterations after morphine. We conclude that in stable patients with chronic ischemic heart disease studied in the supine position, 1) morphine exerts no effect on left ventricular dimensions, an observation which does not support the concept that this agent acts in humans by producing a 'pharmacologic phlebotomy'; and 2) morphine does not alter left ventricular function at rest. Whether different results will be found in patients with increased sympathetic activity, such as occurs in the setting of an acute myocardial infarction or during an episode of acute pulmonary edema, remains to be investigated.

Assessment of pulmonary valve echogram in normal subjects and in patients with pulmonary arterial hypertension

To assess the validity of ultrasound criteria for pulmonary arterial hypertension, we studied pulmonary valve motion in 28 patients and 20 normal subjects. In the latter group, we categorised normal movement of the posterior leaflet of the pulmonary valve in a fashion not previously described. Of the 28 patients, 19 had pulmonary arterial hypertension (pulmonary artery mean pressure more than 20 mmHg, range 22 to 72). Negative, flat, and positive e to f slopes occurred equally in normal subjects and patients. Maximal a wave excursion was less than 2 mm in 9 of 13 patients with pulmonary hypertension who had sinus rhythm, but was more than 2 mm in all normals and in the 9 patients with normal pulmonary artery pressure (69% sensitivity and 100% specificity). The b to c slope was more than 450 mm/s in 6 of 18 patients with pulmonary arterial hypertension and was less than 450 mm/s in all others (33% sensitivity and 100% specificity). The normalised right ventricular pre-ejection period was more than 0.095 (range 0.10 to 0.16) in 13 of the 19 patients with pulmonary arterial hypertension and less than 0.095 in all others (68% sensitivity and 100% specificity). A midsystolic notch occurred in patients with pulmonary arterial hypertension and in no normal subjects or patients with normal pulmonary arterial pressure. Of the 19 patients with pulmonary arterial hypertension, 18 were identified by one or more ultrasound criteria. Of the 5 patients who met only 1 criterion (increased normalised right ventricular pre-ejection period), 4 had atrial fibrillation. We conclude that measurement of the pulmonary valve e to f slope is useless for identifying pulmonary arterial hypertension. However, changes in normalised right ventricular pre-ejection, maximal a wave excursion, b to c slope, and the presence of a midsystolic notch, while insensitive, are highly specific for pulmonary atrial hypertension.

Effects of tocainide on left ventricular performance at rest and during acute alterations in heart rate and systemic arterial pressure. An echocardiographic study

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Efficacy of a new oral agent (tocainide) in the acute treatment of refractory ventricular arrhythmias

To assess the efficacy of tocainide, a new oral analog of lidocaine, 30 patients with ventricular arrhythmias refractory to quinidine, procainamide and propranolol were treated with this agent. The dose of tocainide ranged from 400 to 800 mg every 8 hours. Peak tocainide blood levels 1 to 4 hours after administration ranged from 5.0 to 15.0 microgram/ml (mean 10.3). The suppression of ventricular premature beats by 75 percent or more was arbitrarily used as a measure of drug efficacy. In 13 patients who met this criterion, ventricular premature complexes, assessed with 24 hour ambulatory tape monitoring, decreased by an average of 88 percent. In 8 of 11 patients, repeated symptomatic bouts of ventricular tachycardia were completely suppressed. Considering both the response of ventricular premature complexes and the abolition of ventricular tachycardia, 18 patients (60 percent) responded to tocainide. Twenty-one patients (70 percent) had initial gastrointestinal and central nervous system side effects; most of these were transient or responded to a reduction in dose. In two patients disorientation and a skin rash required withdrawal of tocainide. These adverse effects did not appear to be due to the interaction of tocainide with other antiarrhythmic agents. It is concluded that tocainide is an effective oral agent for the therapy of potentially lethal ventricular arrhythmias refractory to other medication.