Search PubMed⌕ Search

Biomedical subjects

N Hasebe

Publications and source records attributed to N Hasebe.

At least 37 records · Page 2Linked to original sources
PubMed1998

A case of cardiac sarcoidosis: significance of ventricular tachycardia originating from the septum.

A 65-year-old woman was admitted for assessment of recurrent tachycardia. Cross-sectional echocardiography showed that the anterobasal portion of the ventricular septum was thin and dyskinetic. An electrophysiologic study revealed ventricular tachycardia, during which marked fragmented potentials could be obtained from the anterior septal aspect of the right ventricle. The site of earliest activation was in the vicinity of the His bundle. A diagnosis of cardiac sarcoidosis was made by based on endomyocardial biopsy combined with the clinical manifestations. Ventricular tachycardia originating from the anterior septum may be an indicator of underlying cardiac sarcoidosis.

Aged↗
PubMed1998

[Significance of coronary risk factors and coronary arteriosclerosis for coronary vasospasm].

The clinical significance of coronary arteriosclerosis and coronary risk factors was investigated in patients with coronary spasm. Coronary spasm induction test with acetylcholine was performed in 140 consecutive patients (85 males and 55 females) with chest pain in our hospital. The patients were divided into positive, borderline, and negative groups according to the results of the test. The positive and borderline groups were categorized as the coronary contractive group. The coronary sclerosis index was used to evaluate the degree of coronary arteriosclerosis. Coronary risk factors were evaluated in terms of hypertension, diabetes mellitus, hyperlipidemia, obesity, history of smoking and drinking, and family history of cardiovascular events. Patients could be divided into 34.3% in the positive group and 23.6% in the borderline group, i.e. 57.9% in the coronary contractive group, and 42.1% in the negative group. There were more males than females in both positive and coronary contractive groups. The proportion of males in the coronary contractive group was higher in patients over 60 years of age than in patients under 60. In contrast, the proportion of females was higher in patients under 60 than in patients over 60. In male patients, the coronary sclerosis indices in the positive, borderline, and coronary contractive groups were higher than those in the negative group. The indices in female patients in the positive and coronary contractive groups were higher than the index in the negative group. There were no differences in terms of the presence or absence, or the degree of organic stenosis between spastic sites and nonspastic branches in the positive group. The history of smoking in male patients was significantly more common in the positive group than in the negative group. The family history was more relevant in female patients in the positive or coronary contractive group compared to the negative group. Moreover, the history of smoking in the coronary contractive group was significantly more common than that in the negative group. The development of coronary spasm may be determined, at least in part, by the degree of coronary sclerosis as well as by gender and age. Smoking habits in both sexes and family history in females are proposed as the most important risk factors for coronary spasm.

Acetylcholine↗
PubMed1998

[Left atrial function and left atrial appendage flow velocity in hypertrophic cardiomyopathy: comparison of patients with and without paroxysmal atrial fibrillation].

The involvement of left atrial (LA) appendage flow velocity in reduced left atrial function was investigated in 24 patients with hypertrophic cardiomyopathy, who retained sinus rhythm at the examination. Patients were divided into 11 with a history of paroxysmal atrial fibrillation [PAf(+)] and 13 without such history [PAf(-)]. Transthoracic echocardiography was performed to evaluate LA fractional shortening (LA%FS) and mean velocity of circumferential LA fiber shortening (LAmVcf), as contractile functions of the left atrium at the phase of active atrial contraction. Transesophageal echocardiographic Doppler examination was performed in all patients to measure the LA appendage velocity. In all patients, significant positive correlations were observed between the LA appendage velocity and LA%FS (r = 0.50, p < 0.05) or LAmVcf (r = 0.82, p < 0.001). LAmVcf and LA appendage velocity in patients with paroxysmal fibrillation were significantly lower than in those without (0.84 +/- 0.15 vs 1.28 +/- 0.37 circ/sec, 44 +/- 12 vs 65 +/- 20 cm/sec, both p < 0.01), whereas LA diameter was greater in the former compared to the latter (45 +/- 5 vs 38 +/- 5 mm, p < 0.01). LAmVcf and LA appendage velocity were low in four patients with cerebral infarction or transient cerebral ischemic attack (LAmVcf < 1.0 circ/sec, LA appendage velocity < or = 40 cm/sec). Importantly, all these patients had a history of paroxysmal fibrillation. These results indicate that there is a close relationship between LA appendage velocity and LA contractile function in patients with hypertrophic cardiomyopathy with paroxysmal atrial fibrilation, and these patients have potential risk of cerebral infarction.

Adult↗
PubMed1997

Longitudinal study of the mental health of caregivers caring for elderly patients with dementia: effect of institutional placement on mental health.

One hundred and three family caregivers of relatives with dementia were longitudinally surveyed to examine the course of caregivers' mental health after the relatives had been placed in full-time care facilities. Mental health was assessed twice, with a 6-month interval, using the Japanese version of the 60-item General Health Questionnaire. The degree of social dysfunction was significantly reduced within 6 months after placement, while the other indicators of mental health (e.g. anxiety-insomnia, depression, somatic symptom and psychiatric morbidity) were not reduced within this term. However, anxiety-insomnia and psychiatric morbidity were significantly reduced more than 6 months after placement. Analyses by caregivers' lineal relations to the relatives indicated that only daughters-in-law showed a significant decrease in anxiety-insomnia and a marginal reduction in psychiatric morbidity. This study suggests that caregivers' social dysfunction was more greatly reduced than anxiety-insomnia and psychiatric morbidity within a relatively short term after placement, and that its effects on mental health might vary with the lineal relations.

Adult↗
PubMed1997

Radiation dosimetry measurements with real time radiation monitoring device (RRMD)-II in Space Shuttle STS-79.

The real-time measurement of radiation environment was made with an improved real-time radiation monitoring device (RRMD)-II onboard Space Shuttle STS-79 (S/MM#4: 4th Shuttle MIR Mission, at an inclination angle of 51.6 degrees and an altitude of 250-400km) for 199 h during 17-25 September, 1996. The observation of the detector covered the linear energy transfer (LET) range of 3.5-6000 keV/micrometer. The Shuttle orbital profile in this mission was equivalent to that of the currently planned Space Station, and provided an opportunity to investigate variations in count rate and dose equivalent rate depending on altitude, longitude, and latitude in detail. Particle count rate and dose equivalent rate were mapped geographically during the mission. Based on the map of count rate, an analysis was made by dividing whole region into three regions: South Atlantic Anomaly (SAA) region, high latitude region and other regions. The averaged absorbed dose rate during the mission was 39.3 microGy/day for a LET range of 3.5-6000 keV/micrometer. The corresponding average dose equivalent rates during the mission are estimated to be 293 microSv/day with quality factors from International Commission on Radiological Protection (ICRP)-Pub. 60 and 270 microSv/day with quality factors from ICRP-Pub. 26. The effective quality factors for ICRP-Pub. 60 and 26 are 7.45 and 6.88, respectively. From the present data for particles of LET > 3.5keV/micrometer, we conclude that the average dose equivalent rate is dominated by the contribution of galactic cosmic ray (GCR) particles. The dose-detector depth dependence was also investigated.

Aerospace Medicine↗
PubMed1997

Measurements of LET distribution and dose equivalent onboard the Space Shuttle IML-2 (STS-65) and S/MM#4 (STS-79).

Space radiation dosimetry measurements have been made onboard the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2: 28.5 degrees x 300 km: 14.68 days) and the STS-79 in the 4th Shuttle MIR mission (S/MM#4: 51.6 degrees x 300-400km: 10.2 days). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD-I for IML-2 and RRMD-II with improved triggering system for S/MM#4)" utilizing silicon semi-conductor detectors and the other detectors are conventional passive detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. The main contribution to dose equivalent for particles with LET > 5.0 keV/micrometer (IML-2) and LET > 3.5 keV/micrometer (S/MM#4) is seen to be due to galactic cosmic rays (GCRs) and the contribution of the South Atlantic Anomaly (SAA) is less than 5% (IML-2: 28.5 degrees x 300 km) and 15% (S/MM#4: 51.6 degrees x 400 km) in the above RRMD LET detection conditions. For the whole LET range (> 0.2 kev/micrometer) obtained by TLDs and CR-39 in these two typical orbits (a small inclination x low altitude and a large inclination x high altitude), absorbed dose rates range from 94 to 114 microGy/day, dose equivalent rates from 186 to 207 microSv/day and average quality factors from 1.82 to 2.00 depending on the locations and directions of detectors inside the Spacelab at the highly protected IML-2 orbit (28.5 degrees x 300 km), and also, absorbed dose rates range from 290 to 367 microGy/day, dose equivalent rates from 582 to 651 microSv/day and average quality factors from 1.78 to 2.01 depending on the dosimeter packages around the RRMD-II "Detector Unit" at the S/MM#4 orbit (5l.6 degrees x 400km). In general, it is seen that absorbed doses depend on the orbit altitude (SAA trapped particles contribution dominant) and dose equivalents on the orbit inclination (GCR contribution dominant). The LET distributions obtained by two different types of active and passive detectors, RRMDs and CR-39, are in good agreement for LET of 15 - 200 kev/micrometer and difference of these distributions in the regions of LET < 15 kev/micrometer and LET > 200 kev/micrometer can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks and chemical etching conditions.

Atlantic Ocean↗
PubMed1997

[A psychological burden on patients with clinical trials during anesthesia].

We investigated with questionnaires, psychological outline of 30 patients, who were requested to participate in clinical trials of anti-tachycardia drugs during anesthesia. Although 14 patients consented to the trial, the consent was not based on adequate understanding or volunteerism in 3 patients. Nine patients of the consented group were anxious about the possible use of the trial drug. Eight patients of the rejected group felt anxiety on surgery and anesthesia, which was the most common reason for rejection. Forty % of refused patients felt a guilty conscience or embarrassed. Although we tried to obtain patients' consent following governmental and institutional regulations and guidelines, not only the consented but also the refused patients suffer from psychological burden with the clinical trial. It is of concern that recruitment to the trial enhances anxiety of the patients as they already feel uneasiness, unrest, and insecurity facing anesthesia and surgery. To avoid entry of less informed or unwilling patients to the clinical trial, we must secure patients' veto, and recruitment should be performed by clinicians who are not involved in anesthesia practice.

Anesthesia↗
PubMed1997

[Clinical significance of 123I-MIBG myocardial scintigraphy in patients with hypertrophic cardiomyopathy].

We studied the abnormality of myocardial sympathetic nervous system in patients with hypertrophic cardiomyopathy using 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy in comparison with the parameters of other clinical examinations. In 50 patients with HCM, the heart to mediastinum 123I-MIBG uptake ratio (H/M) was significantly low and washout rate (WR) of 123I-MIBG was significantly high respectively compared with normal subjects (n = 8). H/M was negatively correlated with serum norepinephrine level, wall thickness of left ventricle, left ventricular mass index, left ventricular end diastolic pressure respectively, and WR was positively correlated with those parameters respectively. On the other hand, LF/HF calculated by spectral analysis in holter electrocardiogram was positively correlated with H/M, and negatively correlated with WR. In HCM, H/M in patients with subjective symptoms was significantly lower than that without subjective symptoms, and WR in patients with paroxysmal atrial fibrillation was significantly higher than that without paroxysmal atrial fibrillation. This study revealed that H/M and WR reflected the severity and the difference of disease type in HCM. In conclusion, 123I-MIBG contributes to evaluating more details in diagnosis and pathophysiology of HCM.

3-Iodobenzylguanidine↗
PubMed1996

Coronary vascular morphology in pressure-overload left ventricular hypertrophy.

To attempt to explain the loss of subendocardial coronary reserve in chronic pressure-overload cardiac hypertrophy on a morphologic basis, we measured capillary capacity and coronary artery and arteriole medial wall area in dogs with moderately severe chronic (1 year) left ventricular hypertrophy (LVH). Aortic bands were placed on the ascending aorta of 8-10-week-old puppies of either sex, and hearts were perfusion fixed with 2% glutaraldehyde 8-16 months later after hemodynamic study while fully conscious. Left ventricular (LV) mass/body weight ratio in 11 banded dogs with LV end-diastolic pressure < 12 mmHg was 72% greater than in 15 controls (C). There was a decrease in subendocardial coronary reserve during adenosine-induced vasodilation with a shift away from the subendocardium (endo/epi flow ratio: C = 0.68 +/- 0.05; LVH = 0.34 +/- 0.06; P < 0.05). In spite of the extensive hypertrophy, image analysis revealed capillary density to be equally reduced by only 10-15% in endo, mid and epicardial LV regions compared to control dogs, while increased capillary cross-sectional area resulted in no change in capillary surface area/myocyte volume or volume percentage capillary space. In addition to these data suggesting capillary angiogenesis, there was no reduction in arteriolar density, indicating transmural increase in arteriolar number, and, as a consequence, increased total length of the resistance vessels. Medial area of arterioles and arteries showed a graduated increase according to size. We concluded that due to the lack of transmural difference in vascular morphology in chronic (1 year) moderately severe LVH, these anatomic bases do not play a major role as a cause for the loss of coronary reserve. Regional functional differences as a consequence of the morphologic alterations, however, cannot be excluded.

Adenosine↗
PubMed1996

Measurement of LET distribution and dose equivalent on board the space shuttle STS-65.

Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD)" utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 microSv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit for space radiation with a small inclination (28.5 degrees) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15-200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks.

Atlantic Ocean↗
PubMed1996

A new silicon detector telescope for measuring the linear energy transfer distribution over the range from 0.2 to 400 keV/micrometer in space.

A new telescope consisting of three two-dimensional position-sensitive silicon detectors which can measure the linear energy transfer (LET) distribution over the range from 0.2 to 400keV/micrometers has been developed as a real-time radiation monitor in manned spacecraft. First, the principle of LET measurement and its design method are described. Second, suitable electronic parameters for the LET measurement are experimentally determined. Finally the telescope performance is investigated by using, relativistic heavy ions. The first in-flight test of this type of telescope on the US Space Shuttle (STS-84) is scheduled for May, 1997.

Astronomy↗
PubMed1995

Effects of hypertrophy on left atrial and ventricular compliance and plasma ANF levels in conscious dogs.

Alterations in left atrial (LA) and left ventricular (LV) compliance and arterial and coronary sinus atrial natriuretic factor (ANF) concentrations at baseline and in response to both volume depletion and expansion were investigated in 15 conscious dogs with aortic banding-induced LV hypertrophy (LVH) (LV/body wt increased by 64%), which also induced LAH (LA/body wt increased by 61%). With volume expansion coronary sinus ANF increased more (P < 0.05) in dogs with LVH (+427 +/- 88 pg/ml) compared with control dogs (+146 +/- 45 pg/ml). Arterial ANF levels also rose more with volume expansion in LVH. In dogs with LVH, the LV end-diastolic pressure-diameter relationship was shifted to the left with a steeper slope with volume expansion, such that at any given diastolic dimension, diastolic pressure was higher. In contrast, the pressure-dimension relationship for the LA appendage was shifted in the opposite direction during both atrial systolic and diastolic phases, with a more shallow slope in hypertrophy compared with control dogs, resulting in an augmented pressure-dimension product during volume loading in LAH. In conclusion, in dogs with LVH and LAH, enhanced ANF was revealed in the coronary sinus and systemic circulation during volume expansion, which could be due, in part, to a more compliant, but hypertrophied, LA, which responded to equivalent volume loading with an augmented pressure-dimension product.

Animals↗
PubMed1995

[Systemic and regional myocardial distribution of 123I-BMIPP in normal subjects].

We estimated the systemic and left ventricular (LV) regional myocardial distribution of 123I-BMIPP (beta-methyl-p-iodophenyl-pentadecanoic-acid) in normal subjects (n = 13, mean age 43.9). In planar studies, the count ratios of heart, lung and liver to mediastinum were 2.63, 1.28 and 3.80 in the early images, and 2.23, 1.20 and 2.26 in the delayed images, respectively. The uptake in liver was almost identical with that in heart in the delayed images. In SPECT studies, the regional relative counts in anterior, septal, posterior and lateral LV walls were 100, 98, 96 and 108 (%) in the initial images, and 100, 98, 99 and 107 (%) in the delayed images, respectively. The regional relative uptake was significantly higher in the lateral wall than those in the other parts of LV walls in both images. The relative counts in the basal, mid- and apical portions were 100, 111 and 87 (%) in the initial images, and 100, 113, 92 (%) in the delayed images, respectively. These results suggest that the myocardial regional distribution of BMIPP is not always uniform even in normal subjects. Thus, it is necessary to interpret with caution in the light of these findings, especially for detect in a myocardial lesion in an early phase of cardiomyopathy or a mild myocardial ischemia.

Adult↗
PubMed1994

Enhanced postischemic dysfunction selective to subendocardium in conscious dogs with LV hypertrophy.

The effects of a 15-min coronary arterial occlusion (CAO) and reperfusion (CAR) for 24 h were compared in 11 normal dogs and in 13 conscious dogs with left ventricular (LV) hypertrophy (H) induced by ascending aortic banding, which increased the LV weight-to-body weight ratio by 69%. The dogs were studied 2-4 wk after recovery from instrumentation for measurement of global LV dynamics and regional wall motion. During CAO, heart rate and LV end-diastolic pressure increased similarly in both groups; however, LV systolic pressure decreased (-38 +/- 6 mmHg; P < 0.01) only in LVH. At 1 h of CAR, all measurements of systemic hemodynamics and global LV function returned to baseline levels in normal dogs; however, sustained depression (P < 0.01) in LV systolic pressure (-18 +/- 4 mmHg) and mean velocity of circumferential fiber shortening corrected for heart rate (-0.17 +/- 0.06) were observed in LVH. The recovery in regional myocardial dysfunction was significantly prolonged in the subendocardium (Endo) of LVH, e.g., at 1 h of CAR, Endo wall thickening was depressed more in dogs with LVH compared with normal dogs (-69 +/- 3% vs. -53 +/- 5%; P < 0.01), but not in the subepicardium (Epi). Coronary flow reserve, assessed by intravenous adenosine, was depressed in Endo of LVH compared with normal dogs, but not altered further by CAR. In conclusion, myocardial stunning after a brief period of CAO in dogs with LVH was not enhanced in Epi but was modestly increased in Endo. This regional dysfunction was, however, sufficiently powerful to induce modest impairment of global LV function.

Animals↗
PubMed1994

Exercise induces cardiac dysfunction in both moderate, compensated and severe hypertrophy.

BACKGROUND: Ventricular hypertrophy begins as a physiological adaptation to cardiac overload but progresses to a pathological state. We examined whether the extent of hypertrophy influenced the response to exercise in terms of its effects on regional and global ventricular function and transmural myocardial blood flow distribution. METHODS AND RESULTS: Left ventricular (LV) hypertrophy was induced by aortic banding in puppies. The effects of treadmill exercise were compared in sham-operated control dogs (n = 7) and in dogs with moderate LV hypertrophy (47% increase in LV wt/body wt, n = 7) with normal baseline levels of LV systolic and diastolic wall stress and dogs with severe LV hypertrophy (85% increase in LV wt/body wt, n = 18), which exhibited elevated levels of LV systolic wall stress at baseline. The dogs with severe LV hypertrophy were further subdivided into those with either elevated or normal baseline levels of LV end-diastolic pressure and wall stress. The response to exercise in dogs with moderate LV hypertrophy was directionally similar to that of sham-operated control dogs for systemic hemodynamics and global and regional LV function, ie, full and subendocardial wall thickening rose, as did mean and diastolic arterial pressures, shortening fraction, and Vcf. The endocardial/epicardial blood flow ratio did not fall during exercise in these two groups. However, relations comparing either LV shortening, Vcf, or wall thickening with LV systolic wall stress during exercise demonstrated depressed myocardial function in the dogs with moderate LV hypertrophy. In contrast, in dogs with severe LV hypertrophy, exercise reduced LV shortening fraction, Vcf, mean and diastolic arterial pressures, and full and subendocardial wall thickening, and the endocardial/epicardial blood flow ratio fell to 0.73 +/- 0.07. There were no differences observed between the two subgroups with severe LV hypertrophy, but the global and regional wall function responses to exercise were more severely impaired than those in dogs with moderate LV hypertrophy. CONCLUSIONS: Responses of global and regional LV function and transmural myocardial blood flow distribution to exercise were clearly abnormal in dogs with severe LV hypertrophy with elevated baseline levels of LV systolic wall stress whether or not baseline levels of LV end-diastolic wall stress were elevated. Thus, it required more severe LV hypertrophy as well as elevated levels of LV wall stress to elicit qualitatively abnormal regional and global hemodynamic responses to exercise. However, even with moderate LV hypertrophy, which was well compensated under baseline conditions, qualitatively impaired contraction-afterload relations were observed during the stress of exercise.

Animals↗
PubMed1993

Inhibition of endothelium-derived relaxing factor enhances myocardial stunning in conscious dogs.

BACKGROUND: Impaired endothelial-dependent vascular responses after coronary artery occlusion (CAO) and reperfusion (CAR) have been investigated extensively. However, it is not known whether impaired endogenous endothelium-derived relaxing factor production affects postischemic myocardial dysfunction, ie, myocardial stunning. METHODS AND RESULTS: Eight dogs were instrumented with an intracoronary catheter and an hydraulic occluder on the left circumflex coronary artery. The effects of a 10-minute CAO randomized with and without intracoronary administration of NG-nitro-L-arginine (L-NA), a nitric oxide (NO) synthesis inhibitor, were compared in the same conscious dogs. Postischemic regional contractile dysfunction in subendocardial and subepicardial as well as transmural wall thickening was measured with ultrasonic dimension crystals, and myocardial blood flow was measured with radioactive microspheres. Intracoronary infusion of L-NA did not affect systemic hemodynamics, and transmural myocardial blood flow was reduced slightly (-8%), but significantly, only in the left circumflex territory. The recovery of wall thickening was significantly delayed in the presence of L-NA compared with the absence of L-NA, eg, at 30-minute CAR, not only in the subendocardium (-76 +/- 9% versus -49 +/- 9%) but also in the subepicardium (-52 +/- 8% versus -29 +/- 7%). During CAO, blood flow was decreased identically in both conditions, and during CAR, the differences in blood flow were minor (7%). CONCLUSIONS: Inhibition of NO synthesis enhanced myocardial stunning transmurally in conscious dogs, potentially independent of its effects on blood flow.

Animals↗
PubMed1992

Effect of xamoterol in Shy-Drager syndrome.

BACKGROUND: Xamoterol, a cardioselective beta 1-adrenoceptor partial agonist, has been reported to be effective on postural hypotension. We investigated the effect of xamoterol in five patients with Shy-Drager syndrome (SDS) in relation to their prevailing sympathetic nerve activity and sensitivity of beta-adrenoceptors and the change in circadian variation of blood pressure. METHODS AND RESULTS: Ambulatory blood pressure over 24 hours was monitored by noninvasive sphygmomanometer (model 5200, Spacelab). Plasma norepinephrine levels of SDS patients were significantly lower than that of normal subjects (n = 5) both at rest (54 +/- 15 versus 178 +/- 83 pg/ml) and after 10-minute standing (74 +/- 24 versus 318 +/- 143 pg/ml). Infusion of isoproterenol (0.02 micrograms/kg/min) produced a mild rise of systolic blood pressure and tachycardia in normal subjects but resulted in marked hypotension and tachycardia in SDS subjects. After xamoterol administration (200 mg b.i.d.), systolic blood pressure and heart rate were significantly increased in the averages during the day; however, increases were more pronounced at night. In two of the five patients, the improvement in dizziness was large enough to enable them to increase their daily activities. CONCLUSIONS: Our observations suggest that 1) beta 1-selective, high intrinsic sympathomimetic activity of xamoterol increases blood pressure and heart rate in patients with SDS as a consequence of their prevailing beta 1-adrenoceptor hypersensitive state, and 2) blood pressure monitoring over 24 hours appears to have important advantages in evaluating the therapeutic effects on postural hypotension.

Adrenergic beta-Agonists↗