Threshold photodetachment in a repulsive potential.

We report on the first experimental observation of a new threshold behavior observed in the 5(2)G partial channel in photodetachment of K(-). It arises from the repulsive polarization interaction between the detached electron and the residual K(5(2)G) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5(2)G) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme.

Electron rescattering in above-threshold photodetachment of negative ions.

We present experimental and theoretical results on photodetachment of Br(-) and F(-) in a strong infrared laser field. The observed photoelectron spectra of Br(-) exhibit a high-energy plateau along the laser polarization direction, which is identified as being due to the rescattering effect. The shape and the extension of the plateau is found to be influenced by the depletion of negative ions during the interaction with the laser pulse. Our findings represent the first observation of electron rescattering in above-threshold photodetachment of an atomic system with a short-range potential.

Osteitis deformans (Paget's disease) and calcific disease of the heart valves.

The prevalence of calcific aortic valve stenosis in Paget's disease (osteitis deformans) was investigated by reviewing autopsy data of severe cases (> or = 75% involvement of > or = 3 major bones, the femur, tibia, skull, and pelvis) and moderate cases (> or = 75% involvement of only 1 or 2 major bones) of Paget's disease. Comparisons were made with normal age-matched controls. Aortic stenosis (AS) was present in 24% of 27 autopsies of severe Paget's disease compared with 3.5% in 201 controls (p <0.01). Clinical signs of AS were present in 39% of 102 patients with severe Paget's disease compared with 4% in 417 controls (p <0.101). The prevalence of AS in 18 cases of moderate Paget's disease was similar to that of controls. Electrocardiograms were reviewed in 45 cases of Paget's disease and compared with 80 controls of similar age. Complete atrioventricular (AV) block, incomplete AV block, bundle branch block, and left ventricular hypertrophy were present in 11%, 11%, 20%, and 13% of the Paget's cases and in only 2.5%, 1.3%, 2.5%, and 3.8% in the control cases (p <0.05, <0.05, <0.01, and <0.05, respectively). It is concluded that in severe Paget's disease there is a high prevalence of AS, heart block, and bundle branch block, but these are not present in moderate degrees of bone involvement.

High altitude pulmonary edema: hemodynamic aspects.

Over 30 years ago hemodynamic studies on patients with high altitude pulmonary edema (HAPE) excluded the prior contention that the basic cause was left ventricular failure and correctly implicated the pulmonary circulation as the culprit. Physiological studies during the acute stage have revealed a normal pulmonary artery wedge pressure, marked elevation of pulmonary artery pressure, severe arterial unsaturation, and usually a low cardiac output. Pulmonary arteriolar (pre-capillary) resistance was elevated. A working hypothesis of the etiology of HAPE suggests that hypoxic pulmonary vasoconstriction is extensive but not uniform. The result is overperfusion of the remaining patent vessels with transmission of the high pulmonary artery pressure to capillaries. Dilatation of the capillaries and high flow results in capillary injury with leakage of protein and red cells into the alveoli. While hypoxic vasoconstriction appears to be the major cause of patchy vascular obstruction the occurrence of thrombi in the pulmonary vessels may also play a role in more severe and advanced cases. The above concept of the mechanism of HAPE has been further supported by animal studies showing pulmonary edema occurring when increased pressure and flow is produced in a portion of the pulmonary vascular bed. Clinical studies which have supported this concept include the susceptibility to HAPE of patients with an absent pulmonary artery, pulmonary edema occurring in pulmonary embolism, following removal of pulmonary arterial thrombi and following balloon dilatation of stenoses of branches of the pulmonary artery. In addition to those hemodynamic factors an increase in capillary permeability due to cell derived products resulting from capillary wall injury is an important aspect of edema formation.

Lung pathology in high-altitude pulmonary edema.

Autopsy findings in 10 cases of high-altitude pulmonary edema have been collected from published articles and personal observations. All cases were males with a mean age of 37 years (22-62). The altitude of occurrence was from 8400 to 17 500 feet. The mean combined lung weight in nine cases was 1682 g (1200-3000 g). Cerebral edema was present in five of eight cases. The most frequency pulmonary findings in addition to diffuse edema consisted of leukocyte infiltrates, alveolar hemorrhages, thrombi in small pulmonary arteries, and alveolar hyaline membranes. Pulmonary infarction was present in only one case. Right ventricular dilatation was commonly present. The left ventricle was normal. No significant coronary disease was present.

High-altitude pulmonary edema at a ski resort.

Medical records of 150 patients with high-altitude pulmonary edema seen over a 39-month period in a Colorado Rocky Mountain ski area at 2,928 m (9,600 ft) (mean age 34.4 years; 84% male) were reviewed. The mean time to the onset of symptoms was 3 +/- 1.3 days after arrival. Common symptoms were dyspnea, cough, headache, chest congestion, nausea, fever, and weakness. Orthopnea, hemoptysis, and vomiting were rare, occurring in 7%, 6%, and 16%, respectively. Symptoms of cerebral edema occurred in 14%. A temperature exceeding 100 degrees F occurred in 20%, and 17% had a systolic blood pressure of 150 mm of mercury or higher. Blood pressures were higher in patients older than 50 years (142 mm of mercury). Rales were present in 85%, and a pulmonary infiltrate was present in 88%; both were most commonly bilateral or on the right side. The amount of infiltrate was mild. Men appeared to be more susceptible than women to high-altitude pulmonary edema. Pulse oximetry in 45 patients showed a mean oxygen saturation of 74% (38% to 93%). Treatment methods depended on severity and included a return to quarters for portable nasal oxygen, an overnight stay in the clinic for continuing oxygen, or a descent to Denver for recovery or admission to a hospital. All patients received oxygen for 2 to 4 hours in the clinic. There were no deaths or complications.

High-altitude pulmonary edema: current concepts.

High-altitude pulmonary edema (HAPE) occurs in unacclimatized individuals who are rapidly exposed to altitudes in excess of 2450 m. It is commonly seen in climbers and skiers who ascend to high altitude without previous acclimatization. Initial symptoms of dyspnea, cough, weakness, and chest tightness appear, usually within 1-3 days after arrival. Common physical signs are tachypnea, tachycardia, rales, and cyanosis. Descent to a lower altitude, nifedipine, and oxygen administration result in rapid clinical improvement. Physiologic studies during the acute stage have revealed a normal pulmonary artery wedge pressure, marked elevation of pulmonary artery pressure, severe arterial unsaturation, and usually a low cardiac output. Pulmonary arteriolar (precapillary) resistance is elevated. A working hypothesis of the etiology of HAPE suggests that hypoxic pulmonary vasoconstriction is extensive but not uniform. The result is overperfusion of the remaining patent vessels with transmission of the high pulmonary artery pressure to capillaries. Dilatation of the capillaries and high flow results in capillary injury, with leakage of protein and red cells into the alveoli and airways. HAPE represents one of the few varieties of pulmonary edema where left ventricular filling pressure is normal.

How well do older persons tolerate moderate altitude?

We studied the physiologic and clinical responses to moderate altitude in 97 older men and women (aged 59 to 83 years) over 5 days in Vail, Colorado, at an elevation of 2,500 m (8,200 ft). The incidence of acute mountain sickness was 16%, which is slightly lower than that reported for younger persons. The occurrence of symptoms of acute mountain sickness did not parallel arterial oxygen saturation or spirometric or blood pressure measurements. Chronic diseases were present in percentages typical for ambulatory elderly persons: 19 (20%) had coronary artery disease, 33 (34%) had hypertension, and 9 (9%) had lung disease. Despite this, no adverse signs or symptoms occurred in our subjects during their stay at this altitude. Our findings suggest that persons with preexisting, generally asymptomatic, cardiovascular or pulmonary disease can safely visit moderate altitudes.

Oxygen transport and cardiovascular function at extreme altitude: lessons from Operation Everest II.

Operation Everest II was designed to examine the physiological responses to gradual decompression simulating an ascent of Mt Everest (8,848 m) to an inspired PO2 of 43 mmHg. The principal studies conducted were cardiovascular, respiratory, muscular-skeletal and metabolic responses to exercise. Eight healthy males aged 21-31 years began the "ascent" and six successfully reached the "summit", where their resting arterial blood gases were PO2 = 30 mmHg and PCO2 = 11 mmHg, pH = 7.56. Their maximal oxygen uptake decreased from 3.98 +/- 0.2 L/min at sea level to 1.17 +/- 0.08 L/min at PIO2 43 mmHg. The principal factors responsible for oxygen transport from the atmosphere to tissues were (1) Alveolar ventilation--a four fold increase. (2) Diffusion from the alveolus to end capillary blood--unchanged. (3) Cardiac function (assessed by hemodynamics, echocardiography and electrocardiography)--normal--although maximum cardiac output and heart rate were reduced. (4) Oxygen extraction--maximal with PvO2 14.8 +/- 1 mmHg. With increasing altitude maximal blood and muscle lactate progressively declined although at any submaximal intensity blood and muscle lactate was higher at higher altitudes.

Ten-year incidence of myocardial infarction and prognosis after infarction. Department of Veterans Affairs Cooperative Study of Coronary Artery Bypass Surgery.

BACKGROUND: The 10-year incidence of myocardial infarction (fatal and nonfatal) and the prognosis after infarction were evaluated in 686 patients with stable angina who were randomly assigned to medical or surgical treatment in the Veterans Administration Cooperative Study of Coronary Artery Bypass Surgery. METHODS AND RESULTS: Myocardial infarction was defined by either new Q wave findings or clinical symptoms compatible with myocardial infarction accompanied by serum enzyme elevations with or without electrocardiographic findings. Treatment comparisons were made according to original treatment assignment; 35% of the medical cohort had bypass surgery during the 10-year follow-up period. The overall cumulative infarction rate was somewhat higher in patients assigned to surgery (36%) than in medical patients (31%) (p = 0.13) due to perioperative infarctions (13%) and an accelerated infarction rate after the fifth year of follow-up (average, 2.4%/yr in the surgical group versus 1.4%/yr in the medical group). The 10-year cumulative incidence of death or myocardial infarction was also higher in surgical (54%) than in medical (49%) patients (p = 0.20). According to the Cox model, the estimated risk of death after infarction was 59% lower in surgical than in medical patients (p less than 0.0001). The reduction in postinfarction mortality with surgery was most striking in the first month after the event: 99% in the first month (p less than 0.0001) and 49% subsequently (p less than 0.0001). The estimated risk of death in the absence of infarction was nearly identical regardless of treatment (p = 0.75). Exclusion of perioperative infarctions did not alter the findings. CONCLUSIONS: Although surgery does not reduce the incidence of myocardial infarction overall, it does reduce the risk of mortality after infarction, particularly in the first 30 days after the event (fatal infarctions).

Quality of life after bypass surgery for unstable angina. 5-year follow-up results of a Veterans Affairs Cooperative Study.

To assess the effect of bypass surgery on outcome from unstable angina, 468 patients were randomized to medical treatment (237 patients) or surgery plus medical treatment (231 patients) and have been followed for comparison of survival, cardiac end points, and quality of life; the latter end point is discussed in the present report. Data were available at 3 and 5 years for 80% and 82% of patients in the medical group, respectively, and 77% and 80% of patients in the surgery group, respectively. At 3 months after randomization to therapy, 79.8% of patients in the surgery group reported subjective improvement, compared with 58% of the medical group, 12.6% of the surgery group reported no change compared with 24.5% of the medical group, and 5.5% of the surgery group reported worsening compared with 24.5% of the medical group (p less than 0.01 by chi 2). Similar data were found for chest pain status, and the benefit to the surgery group remained statistically significant through 5 years of follow-up. Crossover rate to surgery was 43% by 5 years. Treadmill duration was increased in the surgery group compared with the medical group (6.5 +/- 0.25 versus 5.3 +/- 0.25 minutes at 6 months, p less than 0.01), and a significant difference was again demonstrated at 3 and 5 years. A trend toward decreased recurrence of unstable angina was present in the surgery group at 1 year (six of 168 [3.6%] versus 13 of 187 [6.9%] in the medical group, p = 0.158), but the two groups were similar at 3 and 5 years.(ABSTRACT TRUNCATED AT 250 WORDS)

The electrocardiogram at rest and exercise during a simulated ascent of Mt. Everest (Operation Everest II).

To evaluate the effect of extreme altitude on cardiac function in normal young men, electrocardiograms were recorded at rest and during maximal exercise at several simulated altitudes up to the equivalent of the summit of Mt. Everest (240 torr or 8,848 m). The subjects spent 40 days in a hypobaric chamber as the pressure was gradually reduced to simulate an ascent. Changes in the resting electrocardiogram were evident at 483 torr (3,660 m) and were more marked at 282 torr (7,620 m) and 240 torr (8,848 m). They consisted of an increase in resting heart rate from 63 +/- 5 to a maximum of 89 +/- 8 beats/min; increase in P-wave amplitude in inferior leads; right-axis shift in the frontal plane; increased S/R ratio in the left precordial leads; and increased T negativity in V1 and V2. No significant arrhythmias or conduction defects were observed. Most changes reverted to normal within 12 hours of return to sea level, with the exception of the frontal-plane axis and T-wave alterations. Maximal cycle ergometer exercise at 282 torr (7,620 m) and 240 torr (8,848 m) resulted in a heart rate of 138 +/- 7 and 119 +/- 6 beats/min at the 2 altitudes, respectively. No ST depression or T-wave changes suggestive of ischemia occurred despite a mean arterial oxygen saturation of 49% and a mean pH of 8 during peak exercise. Occasional ventricular premature beats were observed during exercise in 2 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

The sleep electrocardiogram at extreme altitudes (Operation Everest II)

To evaluate the effect of sleep at extreme altitudes upon heart rate and rhythm, continuous sleep monitoring was performed in 8 normal young men during a 40-day simulated ascent of Mt. Everest in a hypobaric chamber. Recordings were made for 1 hour before sleep, during sleep and for 1 hour after awakening in all subjects at 760 torr (sea level), in 7 subjects at 390 torr (5,490 m), in 6 at 347 torr (6,100 m) and in 4 at 282 torr (7,620 m). The following results were obtained: periods of sinus bradycardia occurred during sleep in all subjects at 3 altitudes with a mean heart rate of 41 +/- 0.5 beats/min compared to a rate of 44 +/- 2 beats/min at sea level; cycling of the heart rate, presumably due to periodic breathing, occurred in 14 of 17 studies at altitude but not at sea level (cycles consisted of bradycardia [40 beats/min] for 13 seconds and tachycardia [120 beats/min for 5 seconds]; and arrhythmias were observed in all subjects during sleep and consisted of transient bradycardia (heart rates as low as 20 beats/min), sinus pauses frequently associated with escape rhythms and occasional blocked P waves. No arrhythmias were observed at sea level. Simultaneous records of respiration and the electrocardiogram at 12,500 feet (3,810 m) in 5 other normal subjects revealed tachycardia occurring during hyperpnea and bradycardia occurring during apnea. Data indicate that during sleep in normal young subjects at high altitude, cycling of the heart rate with periodic breathing is common, as are bradyarrhythmias. The mechanism of these arrhythmias has yet to be defined.

Diagnostic accuracy of continuous wave Doppler echocardiography in severe aortic stenosis in the elderly.

Forty-four male patients (mean age 63.6 years) with aortic stenosis (AS) were evaluated by conventional hemodynamic methods and continuous wave (CW) Doppler echocardiography. The relationship between Doppler mean gradients and direct mean pressure gradients in all patients was significant, with an r value of 0.88. Sixteen of 17 patients with a mean Doppler gradient greater than or equal to 40 mmHg had severe AS (AVA less than or equal to 1.0 cm2). Twenty-seven patients had a Doppler gradient less than 40 mmHg, and 8 of these patients had severe AS (AVA less than or equal to 1.0 cm2). The sensitivity and specificity of a Doppler gradient greater than or equal to 40 mmHg in detecting severe AS were, therefore, 67% and 95%, respectively. Thirty-three percent (8/24) of patients with severe AS and low Doppler gradients (less than 40 mmHg) had evidence of poor left ventricular function, evidenced by a lower cardiac output, a higher heart rate and an abnormal PEP/LVET ratio compared to the other patients. Thus, the presence of a low stroke volume less than or equal to 60 ml/beat and PEP/LVET x HR greater than 26 is of value in identifying patients where the Doppler is likely to significantly underestimate the degree of aortic stenosis.

Prevalence and characteristics of the aortic ejection sound in adults.

A survey of 1,950 phonocardiograms recorded over a 6-year period revealed 170 (9%) with a distinct aortic ejection sound. All patients were men with a mean age of 61 years (range 29 to 88). Associated clinical features were: aortic stenosis in 28%, history of systemic hypertension in 10%, history of rheumatic fever in 4% and none of these features in 58% of patients. In 141 (83%) of 170 patients the aortic ejection sound occurred simultaneously with or 0.01 second before or after the onset of the rise of the externally recorded carotid pulse. In 37 (66%) of 56 patients who had simultaneous echocardiograms and phonocardiograms recorded, the aortic ejection sound occurred at 0.01 second before or after the maximal opening point of the aortic valve leaflets. Two-dimensional echocardiography was performed in all patients and a bicuspid aortic valve was identified in 38 patients (22%). In 83 patients (49%) 3 cusps were clearly seen. In 49 patients (29%) an accurate determination was not possible. Anatomic examination of 120 consecutive aortic valves at autopsy was performed to identify possible causes of the aortic ejection sound. In 18 (15%) of autopsies fusion of 2 aortic cusps extending greater than or equal to 5 mm from the attachment to the aorta was observed. This abnormality, aortic commissural fusion, may be congenital or acquired. It is concluded that aortic ejection sounds may occur in patients without bicuspid aortic valves and in a variety of clinical conditions. A moderate degree of cuspal fusion may be the cause of the sound.