Continuous neonatal evaluation in the delivery room by pulse oximetry

The pulse oximeter, a noninvasive and continuous monitor of arterial oxygenation that is reliable in adults, children, and infants, was evaluated for use in neonates in the delivery suite. One hundred newborn infants, weighing 850 to 5,230 g each, delivered vaginally or by cesarean section with general or epidural anesthesia were studied. After delivery, each infant was placed in a radiant warmer, and a pulse oximetry probe was placed on the right hand. Hemoglobin saturation was then recorded for 15 minutes. Initial pulse oximetry values were obtained in less than one minute after cord clamping in 43% of infants, less than two minutes in 81 %, and less than three minutes in 98%. Average arterial oxygen saturation was 59% at 1 minute (43 infants), 68% at 2 minutes (81), 82% at 5 minutes (98), and 90% at 15 minutes (91). Oxygen saturation was less than 30% in 12 neonates and less than 50% in 26 neonates at some time during the 15-minute monitoring period. Oxygen saturation did not differ significantly between neonates delivered vaginally or by cesarean section, regardless of the presence or type of anesthetic used. Arterial oxygen saturation measured by pulse oximetry showed a statistically significant relationship when compared with the traditional Apgar scoring system. Pulse oximetry was found to be very useful in objectively judging the adequacy of resuscitative efforts, as well as in identifying children who had marked arterial desaturation during the early neonatal period.     

Monitored anesthesia care with a combination of ketamine and dexmedetomidine during cardiac catheterization

No specific regimen has been universally accepted as ideal for sedation during cardiac catheterization in infants and children. We evaluated a combination of ketamine and dexmedetomidine for sedation during cardiac catheterization in children with congenital heart disease. The study design included a retrospective analysis of data sheets and hospital records. The protocol for sedation was standardized and data collected prospectively for an ongoing quality assurance project. Heart rate, blood pressure, and oxygen saturation were recorded every 1 minute for the first 5 minutes and then at 5-minute intervals. The efficacy of sedation was judged by the need for supplemental ketamine doses. The study cohort included 16 infants and children undergoing either diagnostic or therapeutic cardiac catheterization. Sedation was initiated with a bolus dose of ketamine (2 mg/kg) and dexmedetomidine (1 microg/kg) administered over 3 minutes followed by a continuous infusion of dexmedetomidine (2 microg/kg per hour for the initial 30 minutes followed by 1 microg/kg per hour for the duration of the case). Supplemental analgesia/sedation was provided by ketamine (1 mg/kg) as needed. The baseline heart rate was 103 +/- 21 beats/minute. After the bolus dose of ketamine and dexmedetomidine, the heart rate increased by 7 +/- 5 beats/minute. The greatest increase was 15 beats/minute. The low heart rate after the bolus dose of ketamine/dexmedetomidine or during the subsequent dexmedetomidine infusion was 91 +/- 20 beats/minute (P < 0.001 compared with baseline) and the high heart rate was 110 +/- 25 beats/minute (P < 0.01 compared with baseline). In two patients, the dexmedetomidine infusion was decreased from 2 to 1 microg/kg per hour at 12 to 15 minutes instead of 30 minutes as a result of a decreased heart rate. No clinically significant changes in blood pressure or respiratory rate were noted. Two patients developed upper airway obstruction, which responded to repositioning of the airway. No apnea was noted. During the procedure, the PaCO2 varied from 37.5 to 48 mm Hg and was > or =45 mm Hg in seven patients. No patient responded to local infiltration of the groin and placement of the arterial and venous cannulae. Three patients required a supplemental dose of ketamine (1 mg/kg) during the procedure. In two of these patients, this was required before changing the cannulae. Our preliminary data suggest that a combination of ketamine and dexmedetomidine provides effective sedation for cardiac catheterization in infants and children without significant effects on cardiovascular or ventilatory function.     

Determination of aortic valve opening time and left ventricular peak filling rate from the peripheral pulse amplitude in patients with ectopic beats

Ectopic beats are common in patients who have heart disease and are associated with reduced peripheral pulse amplitude. This study determined the start of the peripheral pulse increase and from it the opening of the aortic valve. The left ventricular peak filling rate was also estimated from the peripheral pulse. Results were compared with published invasive and cardiac imaging data. Twenty-five subjects with ectopic beat electrocardiograms (ECGs) were studied. The ECGs and the peripheral pulses, detected optically at the right index finger by a simple photoplethysmography (PPG) technique, were recorded for subsequent analysis. Peripheral pulse amplitudes for ectopic beats, post-ectopic sinus beats and normal sinus beats were determined. Ectopic beats induced a mean 68% decrease in pulse amplitude in comparison with sinus beats (p < 0.001). In contrast, the mean pulse amplitude for post-ectopic sinus beats increased by 20% (p < 0.01). Pulse amplitude changes were comparable with the published stroke volume differences for ectopic beats and post-ectopic sinus beats. The range of shortest coupling interval (CI) for ectopic beats with observable pulses was from 373 to 531 ms, with the mean value equivalent to 55% of the mean sinus RR interval, comparable with the opening of the aortic valve. Finally, as the CI increased, the pulse amplitude increased quickly from zero. The average rate of increase was equivalent to 4.8 times the normal sinus amplitude in 1 s, equal to 50% filling in 208 ms, showing diastolic rapid filling, comparable with published left ventricular peak filling rate data. In conclusion, the effect of ectopic beat CI on peripheral pulse amplitude has been determined, providing useful information for developing a technique to determine the opening of the aortic valve and the peak filling rate non-invasively and peripherally in patients with frequent ectopic beats.     

Orthostatic vital signs: variation with age, specificity, and sensitivity in detecting a 450-mL blood loss.

The authors conducted this study to: (1) determine the effect of age on orthostatic vital signs; and (2) to define the sensitivity and specificity of alternative definitions of "abnormal" orthostatic vital signs in blood donors sustaining an acute 450-mL blood loss. The population studied were 100 healthy adult volunteer blood donors and 100 self-sufficient ambulatory citizens attending a senior citizens daytime activity center. Subjects with a history of orthostatic hypotension were excluded. Subjects were first placed in the recumbent position and their rate pulse and blood pressure were determined after 1 minute; these same parameters were measured in the same arm beginning 30 seconds after standing. In blood donors measurement of orthostatic vital signs was repeated immediately after blood donation. Blood donors served as their own controls in the determination of sensitivities and specificities. Mean orthostatic vital sign changes were as follows: pulse rate, 2 +/- 7 beats per minute; systolic blood pressure, -3 +/- 9 mm Hg; and diastolic blood pressure, 1 +/- 7 mm Hg. There was no clinically meaningful variance in orthostatic blood pressure changes with age. For a given specificity, pulse rate increase was the most sensitive of the orthostatic vital signs used alone; a pulse rise of greater than 20 beats per minute had a sensitivity of 9% with a specificity of 98%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Refractory hypoxia in an HIV-infected patient--a diagnostic challenge

A 39-year-old man with HIV presented to the emergency department for evaluation of dyspnea accompanied by fever, diffuse chest discomfort, dry cough, and fatigue for past 1 week. The patient described his dyspnea as exertional progressing over 1 week to rest dyspnea. He was prescribed antiretroviral therapy but was noncompliant. He had no paroxysmal nocturnal dyspnea, orthopnea, rash, oral thrush, or diarrhea. His last record CD4+ lymphocyte count and HIV viral load were 43 cells/mm3 and 178,0000 copies/mL, respectively. Vital signs included a temperature of 101°F, heart rate of 115 beats per minute, respiratory rate of 16 per minute, and pulse oxygenation of 91% on room air. Lung examination revealed decreased breath sounds bilaterally, and the remainder of the examination was unrevealing. Laboratory findings revealed leukocytosis and increased serum lactate dehydrogenase of 577 U/L (90-190 U/L), and chest radiograph showed a right lower lobe infiltrate and perihilar, bilateral interstitial infiltrates (Fig. 1A).     

Accuracy of EMS-Recorded Patient Demographic Data

Objective. Emergency medical services (EMS) research is frequently dependent on data recorded by prehospital personnel. Linking EMS information with hospital outcome depends on essential identifying data. We sought to determine the accuracy of these data in patients who activated EMS for chest pain andto describe the types of errors committed. Methods. We performed a retrospective, consecutive case series study of all prehospital records for patients transported by the City of Pittsburgh Bureau of EMS (annual call volume, 60,000) for chest pain to three area hospitals during a three-month interval. Demographic data, including name, date of birth (DOB), andSocial Security number (SSN), for each patient were extracted from the EMS record. These were compared to the definitive information in the hospital records. Results. 360 prehospital records were examined, with 341 matches to hospital records. The correct patient name was recorded in 301 records (83.6%), the correct DOB was recorded 284 times (78.9%), andthe correct SSN was recorded 120 times (33.3%). The overall error rate of demographic data recorded on EMS records was 73.9% (266/360). If SSN is not included as a demographic variable, then the overall error rate was 25.3% (91/360). Conclusion. The use of EMS-generated demographic data demonstrates moderate agreement andlinkage with hospital records. Name andDOB are more reliable data elements for matching than SSN. Future research should examine the impact of electronic medical records andEMS identification numbers on data reliability.     

Pulmonary Embolism Risk Stratification: Pulse Oximetry and Pulmonary Embolism Severity Index

Background: Risk stratification of pulmonary embolism (PE) patients is important to determine appropriate management. Objectives: We evaluated two published risk-stratification tools in emergency department (ED) PE patients: a pulse oximetry cutoff below 92.5% oxygen (at 5280 feet elevation) and the Pulmonary Embolism Severity Index (PESI). Methods: Electronic medical records of all patients diagnosed with PE were abstracted to identify their triage vital signs, co-morbidities, and adverse short-term outcomes (AO) either requiring interventions (defined as respiratory failure, hypotension requiring pressors, and hemodynamic impairment requiring thrombolytics) or resulting in death. We applied these models to our ED PE patients and assessed their performance. Results: There were 168 PE patients identified, with an overall AO rate of 7.1% (12/168), including a 3.0% mortality rate. A room-air pulse oximetry cutoff of 92.5%, for values measured at 5280 feet, classified 89/136 patients as low risk, 1.1% of which had an AO, and 47/136 patients as high risk, of which 10.6% had AO. This pulse oximetry cutoff had a sensitivity of 83% (95% confidence interval [CI] 36–99%), specificity of 68% (95% CI 58–76%), and a negative predictive value (NPV) of 99% (95% CI 93–100%). PESI classified 91/168 patients as low risk (class I or II): 2.2% had AO but none died, and 77/168 were classified as high risk (class III, IV, or V), with an AO rate of 13.0%. A PESI cutoff score of II had a sensitivity of 83% (95% CI 52–98%), specificity of 57% (95% CI 49–65%), and NPV of 98% (95% CI 92–100%). Conclusion: Both PESI and pulse oximetry measurements are moderately accurate identifiers of low-risk patients with PE.     

Comparison of qSOFA,SIRS, and NEWS scoring systems for diagnosis,mortality, and morbidity of sepsis in emergency department

PurposeThis study was aimed to compare the quick Sequential Organ Failure Assessment (qSOFA), Systemic Inflammatory Response Syndrome (SIRS), and National Early Warning Score (NEWS) scoring systems for diagnosing sepsis and predicting mortality and morbidity.Patients and methodsA prospective study was designed. qSOFA, SIRS, and NEWS scores were calculated at the admission. The diagnosis of sepsis was made with SOFA scoring initially. The morbidity and mortality of the patients were identified during follow-up. Also, the sensitivity, specificity, negative predictive value, and positive predictive value of three scoring systems were calculated. The scoring systems were compared with ROC analysis.ResultsA total of 463 patients were evaluated. There were 287 (62.0%) patients diagnosed with sepsis, and septic shock occurred in 64 (13.8%) of patients. Seven-day mortality rate was 8.4% (n = 39), 30-day mortality rate was 18.1% (n = 84). The sensitivity for qSOFA, SIRS, and NEWS for diagnosis of sepsis was 23%, 77%, 58%, and specificity was 99%, 35%, 81% respectively. The sensitivity of the qSOFA, SIRS and NEWS scoring systems for mortality was 39%, 82%, 77% and specificity 91%, 29%, and 64%, respectively. AUROC values for mortality detected as NEWS = 0.772, qSOFA = 0.758, SIRS = 0.542. According to the ROC analysis, the SIRS system was significantly less useful than the qSOFA and NEWS system in the diagnosis of sepsis and mortality (p < 0.0001).ConclusionNEWS and qSOFA scoring systems have similar prognosis in both diagnosing sepsis and predicting mortality and both are superior to SIRS.     

Slight Rate Acceleration in Permanent Rechargeable Nickel-Cadmium Pacemakers: A Possible Marker of Battery Failure

Thirty-seven rechargeable pacemakers were implanted in 33 patients between 1972 and 1976. Average follow-up has been 4.9 years. Six patients have had these pacers for an average of 7.8 years. Slight rate acceleration of 3 to 5 beats per minute was demonstrated in 46% of the units; rate acceleration to greater than 80 beats per minute was present in three pacemakers, two of which failed within three months. Although rechargeable pacemakers have performed well, frequent surveillance or replacement is warranted if the pacing rate increases to greater than 80 beats per minute     

Embryonic heart rate in the early first trimester: what rate is normal?

Embryonic heart rates below 90 beats per minute at 6 to 8 weeks of gestation have been shown to be associated with a high likelihood of subsequent first trimester demise. The boundary between slow and normal heart rates has not been established, however, in that previous studies do not identify the heart rate for each gestational age at which prognosis plateaus. We evaluated sonograms of singleton pregnancies at 6 to 8 weeks to determine the relationship between heart rate and first trimester outcome in four gestational age subgroups: < or = 6.2, 6.3-7.0, 7.1-7.5, and 7.6-8.0 weeks. Below 6.2 weeks, prognosis improved as heart rate increased to 100 beats per minute, then plateaued for rates > or = 100 beats per minute. At 6.3-7.0 weeks, prognosis improved up to 120 beats per minute, then plateaued. Heart rate norms could not be established at 7.1-8.0 weeks because of the small number of embryonic or fetal deaths in this age group; however, all embryos with heart rates below 110 beats per minute at 7.1-8.0 weeks died. We conclude that the lower limit of normal is 100 beats per minute up to 6.2 weeks' gestation and 120 bpm at 6.3-7.0 weeks.     

Prognostic value of an exercise test one year after myocardial infarction

An exercise test was performed in 306 patients who had had acute myocardial infarction one year previously. The five year cumulative coronary heart disease mortality was 40.0%, when the test had to be discontinued because of ventricular arrhythmias but only 13.0% if discontinued because of fatigue (P less than 0.05). If the maximum work load was less than 80 W the mortality was 30.7% compared with 16.6% in patients who exercised at least 80 W (P less than 0.01). If maximum systolic blood pressure was less than or equal to 150 mmHg mortality was 40.3% compared with 8.5% in patients with greater than 200 mgHg (P less than 0.001). The mortality was 38.2% in patients having single monoform ventricular ectopic beats at a rate of three or more per minute or multiform, paired or early cycle ventricular ectopic beats or ventricular tachycardias: this compared with 14.1% (P less than 0.001) in patients having no or only single monoform ventricular ectopic beats at a rate of less than three per minute. ST-segment depression in univariate testing had no prognostic value. When both exercise test and clinical variables were used in survival analysis (Cox's regression) the most important variable was heart volume and after that ventricular arrhythmias. In multivariate regression analysis ST segment depression also had additional prognostic value. Thus ventricular arrhythmias turned out to be the most important prognostic factor measured during exercise test.     

Rate-Adaptive Cardiac Pacing in Children Using a Minute Ventilation Biosensor

YABEK, S.M., ET AL.: Rate-Adaptive Cardiac Pacing in Children Using a Minute Ventilation Biosensor. Chronotropic integrity is required for a normal cardiac output response to exercise. We evaluated a rate-adaptive ventricular demand pacemaker (Telectronics, META-MV) which uses minute ventilation as the sensed physiological variable for adjusting pacing rate, in seven young patients with a mean age of 11.4 years. All patients had clinically significant bradycardia related to complete heart block (n = 4) or sinus node dysfunction (n = 3). For the entire group, paced heart rates increased from 70 ± 10 beats/min to 151 ± 19 beats/min with exercise testing. The onset of rate adaptation took < 30 seconds. Changes in paced rate were linearly related to workload, VO₂ (5.9 to 20.7 mL/min/kg) and minute ventilation (8–65 L/min). The decline in pacing rate after exercise was related directly to the gradual decrease in minute ventilation and VO₂. Our data show that minute ventilation closely and accurately reflects the metabolic demands of varying workloads in children and can be used to achieve physiological, rate-adaptive pacing.     

Diltiazem to treat sinus tachycardia in critically ill patients: a four-year experience

OBJECTIVES: To determine whether an intravenous infusion of the calcium channel blocker diltiazem was effective and safe in treating sinus tachycardia in critically ill adult patients with contraindications to beta-blockers or in whom beta-blockers were ineffective. DESIGN: Retrospective chart review. SETTING: University medical center. PATIENTS: The records of 171 surgical intensive care unit patients with sinus tachycardia treated with intravenous diltiazem were evaluated. INTERVENTIONS: In all patients with sinus tachycardia (heart rate >100 beats/min), heart rate control with intravenous diltiazem was attempted after adequate intravascular volume expansion, pain, and anxiety control. In all patients, beta-blockade either was contraindicated or (in 7%) had failed. Intravenous diltiazem was administered as a slow 10-mg bolus dose (0.1-0.2 mg/kg ideal body weight), and then an infusion was started at 5 or 10 mg/hr and increased up to 30 mg/hr, as needed, to decrease heart rate to <100 beats/min. Variables retrospectively collected included demographic data, preinfusion blood pressure, mean arterial pressure, heart rate, and preinfusion pressure-rate quotients (pressure-rate quotient = mean arterial pressure / heart rate). Intravenous bolus dose, when given, and diltiazem infusion rate and time necessary to achieve the target heart rate also were recorded. The lowest heart rate recorded within 24 hrs from the initiation of the infusion and the time necessary to achieve the lowest heart rate after beginning the infusion were recorded. MEASUREMENTS AND RESULTS: Of 171 patients studied, 97 (56%) were classified as responders. Multiple linear regression suggested that response could be predicted by age, pressure-rate quotients, baseline mean arterial pressure, and central nervous system failure. In the responders, a heart rate <100 beats/min was achieved in an average of 2 hrs, at a mean diltiazem infusion of 13.3 mg/hr. The lowest rate reached by the responders in a 24-hr period averaged 86 beats/min and was achieved in 4.8 hrs with a mean infusion rate of 14.8 mg/hr. Both target and lowest rate values were statistically different from baseline heart rate. CONCLUSION: Diltiazem was effective in achieving short-term control of heart rate in 56% of the patients, virtually without adverse effects, where beta-blockade was contraindicated or ineffective.     

64层MDCT冠状动脉成像不同心率扇区重建的应用价值

目的：了解扇区重建技术在冠状动脉CT成像中的应用价值。方法：58例受检者,根据心率分为3组,A组,心率〈75次/min,单扇区重建;B组,心率75~94次/min,双扇区重建;C组,心率95~115次/min,四扇区重建。分别测量冠状窦开口处增强前后CT值的变化,并计算强化率,同时测量受检者的受辐射剂量CTD和DLP值。对三维冠状动脉重建图像质量按5个等级进行主观评分：5分无伪影;4分轻微伪影,仅主干的某一段轻微模糊,诊断不受影响;3分为中等伪影,某一支冠状动脉主干的1/2以上模糊,但可以诊断;2分为严重伪影,某一支冠状动脉主干全长均模糊不清或不连续,诊断受限;1分为冠状动脉主干不能识别,不能作出诊断。其中4分以上因伪影的干扰较少定为优良。结果：①主观评分：A组：共29例,优良率为100%;B组：共20例,优良率为85%;C组：共9例,优良率为56%;②客观评估：3组病例的强化均值、强化率、CTD和DLP值之间均存在显著差异（P〈0.05）,单扇区扫描获得的图像的强化效果最佳,且受检者在检查过程中的所受到的辐射剂量最小。结论：受检者在检查前服用β受体阻滞剂控制心率,并采用单扇区重建技术能获得理想的冠状动脉诊断图像。     

The Effect of Maximum Heart Rate On Oxygen Kinetics and Exercise Performance at Low and High Workloads

The normal heart rate is lineurly related to oxygen consumption during exercise. The maximum heart rate of the normal sinus node is approximated by the formula: HR_max= (220-age) with a variance of approximately 15%. However, the nominal upper rate of most permanent pacemakers is 120 beats/min, a value that remains unchanged for many patients. As this nominal setting falls well below the maximum predicted heart rate for most patients, it is possible that the chronotropic response of rate adaptive pacemakers during moderate und maximal exercise workloads may be less than optimal. The purpose of this study was to determine the effect of the upper programmed rate on oxygen kinetics during submaximal exercise workloads and maximum exercise performance during symptom-limited treadmill exercise. Exercise performance with an upper rate programmed to 220-age was compared with an upper rate of 120 beats/min. Eleven patients (5 men and 6 women, mean age 54 ± 10 years) with complete heart block following catheter ablation of the atrioventricular junction for refractory atrial fibrillation who were implanted with permanent, rate-modulating VVIR pacemakers comprised the study population. The rate adaptive sensors were based on activity in 8 patients, minute ventilation in 2 patients, and mixed venous oxygen saturation in 1 patient. After performing a symptom-limited treadmill exercise test to determine maximum exercise capacity and to optimize programming of the rate adaptive sensor, each subject performed two treadmill exercise tests in random sequence with a rest period of at least 1 hour between tests. During one of the tests the upper rate was programmed to a value calculated by the formula: HR_max= (220-age). During the other exercise test the upper rate was programmed to 120 beats/min. Patients were blinded as to their programmed values and to the hypothesis of the study. A novel treadmill exercise protocol was used that consisted of a 6 minute, constant-workload phase at approximately 50% of maximum workload followed immedictely by incremental, symptom-limited exercise using a modified Chronotropic Assessment Exercise Protocol (CAEP) with 1 minute stages until peak exertion. Breath-by-breath analysis of expired gases was performed with subjective scoring of exertional difficulty at the end of the constant workload phase and during each stage of incremental exercise using the Borg Perceived Exertion Scale. Exercise duration was significantly longer (6.37 ± 47 vs 611 ±48 seconds. P < 0.005) with the higher programmed upper rate. Oxygen kinetics were also significantly improved with an age predicted upper rate with a lower O₂ deficit (258 ± 88 vs 395 ± 155 ml, P = 0.002) and higher VO₂ rate constant (3.6 ± 1.0 vs 2.4 ± 0.7. P < 0.001.). The V0_2maxduring peak exertion was higher with an age predicted upper rate than with an upper rate of 120 beats/min (1807 ± 751 vs 1716 ± 702 mL/min, P = 0.01). The mean Borg score was lower during the last common treadmill stage during maximum exercise with an age predicted upper rate than with an upper rate of 120 beats/min (15.7 ± 2.0 vs 16.5 ± 1.9. P = 0.04). The mean Borg score during submaximal. constant workload exercise was also lower with a higher upper rate (9.0 ±2.5 vs 9.6 ± 2.2, P = 0.10). Programming the upper rate of rate adaptive pacemakers based on the age of the patient improves exercise performance and exertional symptoms during both low and high exercise workloads as compared with a standard nominal value of 120 beats/min.     

Oxygen saturation in endoscopic examinations of the upper gastrointestinal tract

Oxygen saturation and pulse rate were continuously recorded using pulse oximetry in 169 consecutive upper gastrointestinal endoscopies (127 EGD and 42 ERCP). Oxygen saturation dropped to below 90% in 37 of 127 patients with EGD and 13 of 42 with ERCP. In EGD-patients with premedication (diazepam) the SaO2 was significantly lower than in patients without premedication. The lowest SaO2 is found in ERCP-patients with bile duct manipulations (EPT, stone extraction, endoprosthesis). Age, sex, patient's position, duration of the investigation and smoking had no effects. The rate of cardiovascular complications in the upper gastrointestinal endoscopy is very low. The possibility of oximetry monitoring and eventually of nasal oxygen application should be given in elderly risk patients with cardiorespiratory diseases, especially in therapeutic procedures and premedication. In younger patients without cardiac diseases an oximetry monitoring is not necessary with or without premedication. The clinical evaluation of the single patient's risk factors should determine whether or not pulse oximetry or supplementary oxygen is useful.     

Dual-demand pacing for refractory atrioventricular re-entry tachycardia.

An automatic dual-demand pacemaker has been used in six patients to treat refractory attacks of paroxysmal re-entry atrioventricular tachycardia that occurred in the Wolff-Parkinson-White syndrome. The pacemaker was designed to pace at a fixed rate of 70 beats per minute when sensed heart rates were either below this rate or above 150 beats per minute; in the latter case, it would compete with the paroxysmal tachycardia and interrupt it after a short period of random scaning. The best location for the permanent pacing electrode and the feasibility of using the pacemaker were tested in each case during a detailed preliminary intracardiac electrophysiological study. The permanent pacing electrode was positioned in the coronary sinus in three patients and was attached to the epicardium of either the left or right ventricle in another three. All patients were given regular oral doses of verapamil or propranolol to enhance the effectiveness of the pacemaker system and, with the latter, to prevent pacemaker activation during sinus tachycardia. Over a follow-up period of between 11 and 47 months, the pacemaker system remained completely effective in three patients, but developed unreliable sensing in another two (one coronary sinus and one left ventricular lead). In the sixth patient the pacemaker was only effective when the rate of the tachycardia remained below 170 beats a minute, as when she was resting supine; when sitting or standing, however, her tachycardia rate considerably exceeded this value and the pacemaker was ineffective. Explantation of the pacemaker and either successful cryosurgical ablation of the accesory AV pathway or treatment with amiodarone was undertaken in the three patients in whom the pacemaker had failed.     

Embryonal heart rate as a predictor of pregnancy outcome: a prospective analysis

To evaluate the association between embryonal heart rate and pregnancy outcome, we prospectively followed 50 very early pregnancies (4.5 to 7.3 weeks of gestation) through the first trimester. Of the 11 embryos that miscarried, 6 had initial heart rates below 85 beats per minute (bpm); in contrast, none of the viable embryos had initial heart rates of or below 85 bpm (P less than 0.0001). A rise in mean heart rate was seen among the viable embryos with increasing gestational age, in concordance with previously reported rates.     

Abnormal electrocardiographic findings in apheresis donors

Electrocardiographic (ECG) monitoring was performed on 291 donors during apheresis. Twenty-one donors (7.2%) had clinical symptoms such as discomfort, nausea, chill, numbness, and paresthesia, and 13 of this group exhibited ECG abnormalities, such as tachycardia, bradycardia, and other abnormal wave patterns. The donors with tachycardia and slight bradycardia had no symptoms. Ten donors had moderate to severe bradycardia with pulse rates less than 50 beats per minute; four of them had severe bradycardia (less than 45 beats per minute), and three of the four exhibited severe hypotension, vomiting, fainting, or convulsion. Other abnormal ECG changes, such as supraventricular and ventricular premature contractions, right bundle branch block, ST segment elevation or ST segment depression, and tall, flattened, or inverted T waves were observed in 29 donors (10%). These changes were not associated with symptoms. Only three of these donors complained of discomfort or chest heaviness. The abnormal waves appeared more often in granulocytapheresis donors than in plateletapheresis donors.     

Acute physiologic and perceptual responses during three modes of ambulation: walking, axillary crutch walking, and running

This study compared the acute physiologic responses during three modes of ambulation--walking, axillary crutch walking (ACW), and running. Twelve healthy women volunteered to ambulate for one kilometer at their self-selected speeds for each of the three activities. Before the ACW test, the subjects completed one or two training sessions to familiarize themselves with this mode of ambulation. Standardized instruments were used to monitor the cardiorespiratory variables, and perceptual responses were recorded using the Borg scale for ratings of perceived exertion (RPE). The results indicated that walking was the least stressful of the three activities. Comparisons between ACW and running revealed that although the steady-state heart rate and minute oxygen consumption were significantly higher during running (173.5 vs 168.6 beats/min and 2.05 vs 1.06 L/min for running and ACW, respectively), the net metabolic cost per unit distance traveled was significantly higher during ACW (1.77 vs 1.01 kcal/kg/km) because of the longer time taken to ambulate the one-kilometer distance. The other variables studied--the oxygen pulse, ventilatory equivalent for oxygen, and RPE--also clearly indicated that ACW was the most stressful activity. Based on these limited observations, it is suggested that special precautions be taken when prescribing axillary crutches to women who have significant cardiorespiratory problems but are unaware of them, or to cardiac patients because of their coronary insufficiency.