Involvement of α- and β-Adrenergic Receptors in Skeletal Muscle Blood Flow Changes During Hyper-/Hypocapnia in Anesthetized Rabbits

OBJECTIVE

This study investigated the involvement of α1- and β2-adrenergic receptors in skeletal muscle blood flow changes during variations in ETCO2.

METHODS

Forty Japanese White rabbits anesthetized with isoflurane were randomly allocated to 1 of 5 groups: phentolamine, metaproterenol, phenylephrine, butoxamine, and atropine. Heart rate (HR), systolic blood pressure (SBP), common carotid artery blood flow (CCBF), masseter muscle tissue blood flow (MBF), and quadriceps muscle tissue blood flow (QBF) were recorded and analyzed at 3 periods: (1) baseline, (2) during hypercapnia (phentolamine and metaproterenol groups) or hypocapnia (phenylephrine, butoxamine, and atropine groups), and (3) during or after receiving vasoactive agents.

RESULTS

MBF and QBF decreased during hypercapnia. The decrease in MBF was smaller than that in QBF. SBP and CCBF increased, while HR decreased. Both MBF and QBF recovered to their baseline levels after phentolamine administration. MBF became greater than its baseline level, while QBF did not fully recover after metaproterenol administration. MBF and QBF increased during hypocapnia. The increase rate in MBF was larger than that in QBF. HR, SBP, and CCBF did not change. Both MBF and QBF decreased to ∼90% to 95% of their baseline levels after phenylephrine or butoxamine administration. Atropine showed no effects on MBF and QBF.

CONCLUSION

These results suggest the skeletal muscle blood flow changes observed during hypercapnia and hypocapnia may mainly involve α1-adrenergic but not β2-adrenergic receptor activity.

Continuous stress disrupts immunostimulatory effects of IL-12

Immune stimulation by biological response modifiers is a common approach in tumor immunotherapy. IL-12 was found effective in various animal studies, but clinical trials showed limited success. However, among other differences, animal models do not simulate psychological or physiological stress while employing IL-12, whereas cancer patients often experience distress while treated with immunostimulants. Thus, in the current study we assessed the impact of continuous stress on the efficacy of IL-12 immunostimulation. F344 rats were subjected to a pharmacological stress paradigm (continuous administration of a β-adrenergic agonist) or to a 20 h behavioral stress paradigm (wet cage exposure) commencing 2h before IL-12 administration. Twenty-six hours after stress initiation, we studied indices known to reflect IL-12 immunostimulatory impacts, including NK cell numbers and activity in different immune compartments, and in vivo resistance to MADB106 lung tumor colonization. The results indicated that both the pharmacological and behavioral stress paradigms significantly reduced the increase in the number and activity of marginating-pulmonary NK cells evident in non-stressed IL-12 treated animals. Additionally, stressed animals exhibited a lower IL-12-induced improvement of MADB106 lung clearance, an in vivo index that markedly depends on total marginating-pulmonary NK activity. These deleterious effects of stress were more prominent in males than in females. Overall, the findings demonstrate that prolonged stress exposure can disrupt the efficacy of simultaneous immunostimulatory treatments, irrespective of stress effects on baseline immune measures. Neuroendocrine and cellular mediating mechanisms are yet unknown, but the potential clinical ramifications of these findings warrant consideration in clinical trials employing immunostimulatory agents.

Initial experience with remote catheter ablation using a novel magnetic navigation system: magnetic remote catheter ablation

BACKGROUND

Catheters are typically stiff and incorporate a pull-wire mechanism to allow tip deflection. While standing at the patient's side, the operator manually navigates the catheter in the heart using fluoroscopic guidance.

METHODS AND RESULTS

A total of 42 patients (32 female; mean age, 55+/-15 years) underwent ablation of common-type (slow/fast) or uncommon-type (slow/slow) atrioventricular nodal reentrant tachycardia (AVNRT) with the use of the magnetic navigation system Niobe (Stereotaxis, Inc). It consists of 2 computer-controlled permanent magnets located on opposite sides of the patient, which create a steerable external magnetic field (0.08 T). A small magnet embedded in the catheter tip causes the catheter to align and to be steered by the external magnetic field. A motor drive advances or retracts the catheter, enabling complete remote navigation. Radiofrequency current was applied with the use of a remote-controlled 4-mm, solid-tip, magnetic navigation-enabled catheter (55 degrees C, maximum 40 W, 60 seconds) in all patients. The investigators, who were situated in the control room, performed the ablation using a mean of 7.2+/-4.7 radiofrequency current applications (mean fluoroscopy time, 8.9+/-6.2 minutes; procedure duration, 145+/-43 minutes). Slow pathway ablation was achieved in 15 patients, whereas slow pathway modulation was the end point in the remaining patients. There were no complications.

CONCLUSIONS

The Niobe magnetic navigation system is a new platform technology allowing remote-controlled navigation of an ablation catheter. In conjunction with a motor drive unit, this system was used successfully to perform completely remote-controlled mapping and ablation in patients with AVNRT.

[Catheter ablation of ectopic atrial tachycardia by electrical pulmonary vein disconnection]

We report a 25-year-old female patient with a long history of symptomatic paroxysmal supraventricular tachycardia. Electroanatomic activation mapping demonstrated a focal tachycardia originating in the right upper pulmonary vein, 3 cm distal to the ostium. Due to the recent experiences in the management of focal atrial fibrillation with catheter ablation, direct ablation applied inside the pulmonary vein was avoided. Instead, an electrical disconnection of the pulmonary musculature from the left atrium guided by a circumferential 10-electrode mapping catheter was performed. The patient has since been asymptomatic during follow-up.

Atrial premature beats in patients with focal atrial fibrillation: incidence at baseline and impact of provocative maneuvers

This study evaluated the incidence of atrial premature beats (APBs) and the impact of various provocative maneuvers in patients with focally initiated AF. Fifty patients (39 men, 57 +/- 0.4 years) with focally initiated, paroxysmal AF underwent Holter recording and a standardized protocol of provocative maneuvers: vagomechanical stimulation, adenosine 12 mg i.v., esmolol 500 ng/kg i.v., orciprenaline i.v. 5 mg/50 mL saline 0.9%, and atropine 0.01 mg/kg i.v. A surface ECG was recorded for 20 minutes at baseline and following each part of the protocol. High focal activity was defined as > or = 1 APB/minute. During Holter ECG, 29 (58%) patients had an amount of < 200 APBs, 12 (24%) patients < 700 > or = 200, and 9 (18%) patients > or = 700 APBs. Less than 1 hour of high focal activity was observed in 34 (68%) of the 50 patients. Before starting provocative maneuvers 15 (30%) patients had high focal activity whereas 35 (70%) presented < 1 APB/minute. In 29 (58%) patients APBs increased by > or = 1/min during provocative maneuvers: by vagomechanical stimulation in 11 patients, after adenosine in 15, esmolol in 12, orciprenaline in 15, and after atropine in 9 patients. In all patients with > or = 1 APB/min at baseline, focal activity decreased or disappeared during some single provocative maneuvers. AF occurred in eight patients under provocative maneuvers. No predictive factors of a successful provocative maneuver were detected with regard to the baseline patients characteristics and Holter results. In conclusion, patients with focally initiated AF have a low incidence of spontaneous APBs. Various provocative maneuvers successfully increase APBs in more than half of the patients; orciprenaline had the highest efficacy. Some provocative maneuvers may suppress APBs in the setting of high focal activity at baseline.

Laser catheter coagulation of atrial myocardium for ablation of atrioventricular nodal reentrant tachycardia. First clinical experience

A new technique for ablation of atrioventricular nodal reentrant tachycardia, using catheter-directed continuous wave Nd-YAG laser light, 1064 nm, via a novel pin-electrode laser catheter, was applied in 10 patients aged 15-63 years (mean 43 years). A total of 22 laser pulses, 1-5 per patient, at 20 or 30 W, of 10-45 s (mean 27 s) were aimed at the postero-inferior aspect of the tricuspid annulus. In all patients the tachycardia was rendered non-inducible at baseline as well as during orciprenaline administration. The amplitudes of the local atrial potentials diminished from 2.0 +/- 0.5 before to 0.4 +/- 0.4 mV after ablation, atrio-His intervals increased from 73 +/- 7 to 157 +/- 36 ms. Anterograde atrioventricular nodal refractory periods (212 +/- 31 vs 238 +/- 31 ms) and Wenckebach rate (174 +/- 8 vs 167 +/- 8 beats.min-1) did not change significantly (P > 0.05). There were no complications or recurrent arrhythmias in a follow-up of 12-35 (mean 27) months. Anatomically guided laser catheter coagulation of the postero-inferior aspect of the tricuspid valve ring is a safe and effective method for the cure of patients with common atrioventricular reentrant tachycardia.

[Unmasking an exclusively retrograde accessory pathway by catecholamines]

A 52-year-old man with frequent episodes of narrow QRS complex tachycardias with rates of 150/min was admitted for electrophysiological evaluation and treatment. P waves could be seen in the ST-segment of the surface ECG during tachycardia. Atrial stimulation during electrophysiological testing was not able to induce tachycardia. During atrial stimulation, there was no evidence of conduction via an accessory pathway or of dual AV node conduction properties. Ventricular stimulation showed complete ventriculoatrial block. After intravenous administration of the catecholamine orciprenaline, single atrial extrastimuli induced an AV macro-reentrant tachycardia with a rate of 165/min. VA conduction showed the earliest retrograde atrial activation in the left anterolateral area. Thus, there was an accessory pathway which only conducted in ventriculoatrial direction and only during adrenergic stimulation. After successful radiofrequency catheter ablation, complete ventriculoatrial block was recorded even after repeat administration of orciprenaline during ventricular stimulation. This case confirms the need to administer catecholamines in every undiagnosed tachycardia during electrophysiological testing to reveal the mechanism of the tachycardia.

[Incidence of myocardial bridges after adrenergic stimulation and decreasing afterload in patients with angina pectoris, but normal coronary arteries]

The prevalence of myocardial bridging in patients with angina pectoris but normal coronary arteries was evaluated in 1780 patients who consecutively underwent coronary angiography. 62 patients (3.5%) were free of coronary atherosclerosis or other organic heart disease. In four of these patients systolic narrowing of the LAD was present. The other 58 patients received 0.2 mg nitroglycerin (NTG) intracoronarily and 30 micrograms/ml orciprenalin (ORC) intravenously up to a heart rate of 130/min. Repeated angiography revealed systolic compression of the LAD due to myocardial bridging (MB) in 40% (25 of 62). The length of MB raised from 1.4 +/- 0.9 cm to 2.1 +/- 1.1 cm (p < 0.001) after NTG and to 2.8 +/- 1.1 cm (p < 0.001) after ORC. Coronary luminal stenosis increased from 48 +/- 29% to 67 +/- 25% after NTG (p < 0.001) and to 83 +/- 18% (p < 0.001) after ORC. The prevalence of myocardial bridging in 40% of patients with stress-induced angina pectoris but normal coronary arteries is high. Nearly always coronary compression by myocardial bridging is only evident after adrenergic stimulation or after afterload reduction. Therefore, NTG and ORC are useful drugs to facilitate diagnosis of myocardial bridging by increasing coronary compression.

Emphysematous changes assessed by selective alveolobronchography and bronchodilator response in chronic airflow obstruction

To investigate the relationship between the emphysematous changes and bronchodilator responses in patients with chronic airflow obstruction (CAO), we studied the correlation between bronchodilator response to 10 mg inhaled metaproterenol and the extent of emphysema, using selective alveolobronchogram (SAB). Fifty-one patients with CAO were classified into 3 groups by the extent of emphysematous changes detected by SAB. In group 1, no or mild emphysematous change was observed on SAB (n = 9); in group 2, there were significant emphysematous changes but the involved area was less than 75% (n = 17); in group 3, emphysematous change was extensive and covered more than 75% (n = 25). The post-bronchodilator forced expiratory volume in 1 sec (FEV1) of patients in group 3 was significantly lower than in groups 1 and 2. The mean value of changes of FEV1 as a percentage of predicted FEV1 of patients in group 3 was significantly lower than in groups 1 and 2. These results indicated that the extent of emphysematous change correlated positively with the severity of fixed airflow obstruction, and negatively with the bronchodilator response.

Pulmonary obstruction in individuals with cervical spinal cord lesions unmasked by bronchodilator administration

In subjects with spinal cord injury (SCI) a restrictive ventilatory impairment has been well described. Despite numerous studies of pulmonary function in patients with SCI, evidence of an obstructive component of respiratory dysfunction as a result of paralysis has not been observed in this population. We performed spirometry in 34 patients with cervical SCI before and after administration of an inhaled bronchodilator. Significant improvement in flow rate was demonstrated in 14 (41%) subjects. Our results suggest that transection of the cervical spine may result in obstruction to air flow, possibly due to interruption of the sympathetic innervation of the lung with resultant unopposed parasympathetic tone producing bronchoconstriction.

Phenolic cyclization of epinephrine, metaproterenol, metaraminol, phenylephrine, and terbutaline with formaldehyde

An exploratory study of the rates of cyclization of the title compounds, all 3-hydroxyphenalkanolamines, with formaldehyde to 1,2,3,4-tetrahydroisoquinolines (THIQs) was performed using high-performance liquid chromatographic (HPLC) methods. Reactions occur quantitatively and practically instantaneously at room temperature and neutral pH; thus, rates were measured at acid pH. Cyclization occurs ortho or para to the 3-phenolic function, so that all but the 3,5-dihydroxyphenyl derivatives, metaproterenol and terbutaline, gave two THIQs. Terbutaline reacted significantly slower than the other compounds. Formaldehyde occurs in pharmaceutical systems and it serves as a model for other aldehydes that occur in sugars and flavors. The pharmaceutical implications of the reaction are discussed.

[Potential use of indenolol in hypertensive patients with chronic bronchial asthma]

The data are reported on a double blind clinical experiment using indenolol on a group of asthmatic hypertensives. The drug revealed a satisfactory anti-hypertensive action in the absence of any significantly bronchoconstrictive effect. The orciprenaline test performed at the end of the experiment showed that the drug does not reduce the availability of beta 2 bronchial receptors vis-à-vis the beta 2 stimulants.

Effect of a deep inspiration on expiratory flow in normals and patients with chronic obstructive pulmonary disease

Normal control subjects and individuals with chronic obstructive pulmonary disease (COPD) were studied by measuring routine lung function tests as well as maximal (MEFV) and partial expiratory flow-volume (PEFV) curves and lung elastic recoil (Pst,L) before and after a total lung capacity (TLC) volume history. In the normal subjects: before bronchodilators airflow increased significantly, whereas Pst,L and upstream segment resistance (Rus) decreased significantly following inspiration to TLC; after administration of inhaled bronchodilators, flow rates were higher on the PEFV than on MEFV curves; nevertheless, because Pst,L decreased substantially following a deep breath, post-bronchodilator Rus was still somewhat reduced by deep inspiration. In the subjects with COPD flow rates on PEFV curves were as high or exceeded flow rates on MEFV curves in 76/100 studies; the ratio of flow rates (PEFV)/flow rates (MEFV) increased as pulmonary function worsened; as in normal subjects, Pst,L diminished in COPD subjects following deep inspiration; although flow rates increased on both PEFV and MEFV curves after bronchodilators, the increments in flow were considerably larger on PEFV maneuvers.

Nifedipine in exercise-induced asthma

The calcium entry blockers may inhibit EIA in patients with bronchial asthma, but it is not demonstrated that they produced bronchodilation once the crisis is established. Nine patients with exercise induced asthma were studied. We carried out an exercise test for ten minutes with constant load and the following were measured; FVC, PEF, MEF25 and sGaw before and after test. All the values fell 20% or more than the initial values. A 20 mg was administered without modifying the studied parameters and only the administration of 400 micrograms of metaproterenol by inhalation made the sensation of dyspnea recur in all patients.

A new method of evaluating the degree of stenosis using a multisensor catheter. Application of the pressure loss coefficient

A new method of evaluating the degree of stenosis using the pressure loss coefficient is presented here. The pressure loss coefficient was obtained in patients with pulmonary or aortic stenosis by measuring the pressure and velocity of the blood simultaneously with a multisensor catheter. Although the pressure gradient across the stenosis was augmented by increasing the blood velocity with pharmacological loading, the pressure loss coefficient remained nearly constant. This confirmed that the pressure loss coefficient is more appropriate for evaluating the degree of stenosis than the pressure gradient, which depends on the blood velocity. The pressure loss coefficients obtained from the preoperative and postoperative catheterization data were compared to evaluate the effects of the surgical operation. A pressure loss coefficient of 15 was proposed as the critical value for the indication of operation.

Effects of cold air hyperpnea in patients with chronic obstructive lung disease

In 26 well-characterized, stable patients with chronic obstructive pulmonary disease (COPD), we measured changes in forced expiratory volume in one second (FEV1) induced by isocapnic hyperpnea of subfreezing dry air. The patients had a mean FEV1 of 1.21 L(38% predicted); 13 of 26 increased their FEV1 by at least 20% in response to inhaled beta agonists, and 11 of 18 subjects tested demonstrated at least a 30% increase in FEV1 with oral administration of corticosteroids. Only 6 of 26 patients responded to cold air hyperpnea with a 20% decrease in FEV1. Cold air response was not related to baseline FEV1 or to the level of hyperpnea attained. Though responses to inhaled beta agonists and systemic steroids were correlated, neither correlated with cold air responses. We conclude that in COPD airway reactivity is not nonspecific but depends on the agent used to elicit airway responses.

[Problems of so-called functional ECG changes]

It is reported on a 25-year-old African student with healthy heart in whom on account of an enlarged hepatologic diagnostics considerable changes of the ECG with repeated alteration between the ST-elevations and the T-negativations became manifest in the anterolateral BW-leads. In the otherwise inconspicuous findings functional changes of the ECG (early repolarization syndrome) with pronounced vegetative lability are concerned. The influence on the changes of the ECG by sympathicomimetics (isoproterenol test) may help to alleviate the diagnostics. In connection with diagnostic interventions the recognition and correct explanation of such ECG-findings is of decisive importance.

The bronchodilating effect of acupuncture in patients with acute asthma

The effectiveness of acupuncture therapy for asthmatic patients was studied by continuous monitoring of the respiratory function. Using the forced 5 Hz oscillating technique, the investigators could estimate the change of total respiratory resistance (Rrs) of asthmatic patients throughout their reception of acupuncture therapy. They performed a single-blind study consisting of a placebo acupuncture, a placebo stimulation and real acupuncture therapy For further control of this study, they selected an easily locatable point for needle placement among the many traditional meridian points. In 10 out of 26 acupuncture therapies. Rrs significantly decreased while in only one of 17 placebo treatments did Rrs decrease.

Disorders in peripheral arterial system in asymptomatic elderly: plethysmographic semiology at rest, during postural, effort and pharmacological tests

The vascular system of 30 old asymptomatic patients (average age 62.5 years) was studied by reflection plethysmography. The plethysmogram (PTG) was recorded from the forefinger of the left hand at rest, during two postural tests (+45 degrees arm-up and -45 degrees arm-down), after physical work, and during the infusion of nitroglycerin and the beta-agonist metaproterenol. 50% of the subjects presented a normal PTG under basal conditions. However, pathological PTGs were recorded after the various tests: 23.3% with the arm-up test, 6.6% with the arm-down test, 52% with the effort test, 31% with the nitroglycerin test and 73.9% with the metaproterenol test. Clearly, the effort and metaproterenol tests are pathological in the majority of cases, both tests inducing physiologically vasodilation and increase in the peripheral pulse. The arm-down test, which usually induces vasoconstriction, is almost always normal. Since the percentage of pathological responses to the nitroglycerin test is significantly smaller than that to the effort and metaproterenol tests, it is concluded that the vascular changes induced by aging are primarily functional, at least in asymptomatic subjects. Aging more negatively influences the vasodilating than the vasoconstricting ability.

[Significance of a negative inhalation test in chronic obstructive lung disease]

To assess the bronchospastic component in patients with chronic obstructive lung disease, measurement of vital capacity and forced expiratory volume (FEV) before and after inhalation of a beta-agonist is a widely used procedure. In a minority of patients this simple inhalation test yields a negative result, suggesting the possibility of unresponsive airways. The purpose of this study was to explore th significance of a negative test result by examining pulmonary mechanics in 17 patients before and after inhalation. The results permit the following conclusions: (1) A significant broncholytic action of a beta-agonist can be determined by measuring vital capacity and FEV. As a rule, a negative test cannot be attributed to the alleged insensitivity of spirometric measurements. For clinicla purposes, the more demanding determination of specific airway conductance is not necessary. (2) A negative inhalation test does not imply a pure emphysema with out peripheral airway disease, any more than it does irreversible bronchiolitis. All it proves is the unimportance of bronchiolospasm at the time of examination. The true role of a spatic component in the course of the disease, and the benefit of regular inhalations, can be assessed on the basis of repeated controls only.

A study of western red cedar-induced asthma

Seventeen asthmatic patients who were workers dealing with Western Red Cedar in a Japanese wooden frame factory were studied. One fraction from the aqueous extract of the lumber induced a positive skin test, Prausnitz-Kustner test and the inhalation test. This confirms the existence of antigen in Western Red Cedar and its ability to produce allergic asthma in sensitive workers.

[Labile repolarization changes in the ECG of patients without heart disease (author's transl)]

Nine patients with suspicious repolarization (ST-T segment) changes in the ECG were further investigated. Each had ten different additional ECG tests (after various degrees of exercise, and orciprenaline, amylnitrite, glucose, potassium chloride, and propranolol injections). The ECG changes became normal in all patients, orciprenaline and propranolol injection providing optimal results. Clinical investigation, left-heart angiocardiography and coronary angiography were normal in all. The questionably abnormal repolarization distrubances were, therefore, judged to be benign. As both beta-stimulation and beta-blockade normalized the ECG it can be safely assumed that the ECG changes were induced by autonomic nervous system factors. Cardiac catheterization appears, therefore, not indicated in each case and a potential iatrogenic heart disease can be avoided by relatively simple means.

Time factor in the measurement of response to bronchodilators

The measurement of response to bronchodilators by recording the change in forced expiratory volume in 1 second (F.E.V._1·0) can underestimate response unless the correct time for postbronchodilator tests is chosen. In 18 patients given isoprenaline, the time of peak response varied, but a 30-minute testing time gave the closest approximation to peak response. In order to test whether repeated doses would increase the response, inhalations of isoprenaline were given at 30-minute intervals, the F.E.V._1·0 being measured after each dose. There was a further response after successive doses until a plateau was reached, usually after the third dose. The maximum response obtained was often considerably greater than the response after the first administration of isoprenaline, the average increase in F.E.V._1·0 being 600 ml. after the first dose and 840 ml. after repeated doses. A similar response was obtained in four patients using orciprenaline spray administered with a metered aerosol, the dose being repeated at hourly intervals. Four patients were given repeated inhalations of isoprenaline until the response reached a plateau, and then 250 mg. of aminophylline was injected intravenously. None of these patients showed any further improvement with aminophylline. The significance of these findings is discussed.