Genetic analysis of the Utah population: a comparison of STR and VNTR loci

Genetic data are reported for nine short tandem repeat (STR) loci (D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, and D7S820) and six variable number of tandem repeat (VNTR) loci (D2S44, D10S28, D4S139, D1S7, D5S110, and D17S79) in samples of Utah African Americans, European Americans, and Hispanics. Little evidence of departures from Hardy-Weinberg equilibrium or gametic equilibrium was found in these populations. Because of their relatively higher mutation rates, the VNTR loci exhibited higher average heterozygosity and lower FST levels than did the STR loci. Genetic distance analysis showed congruence between the two types of systems, and a genetic distance analysis of the STR data showed that the three Utah populations are genetically similar to the same ethnic groups in other parts of the United States. In addition, this analysis showed that the African American population is the most genetically divergent, with greater similarity between the Hispanic and European American populations. This analysis demonstrates a high degree of consistency for population designations commonly used in forensic analysis.

Fever in acute pulmonary embolism

BACKGROUND

Although fever has been reported in several case series of acute pulmonary embolism (PE), the extent to which fever may be caused by PE, and not associated disease, has not been adequately sorted out. Clarification of the frequency and severity of fever in acute PE may assist in achieving an accurate clinical impression, and perhaps avoid an inadvertent exclusion of the diagnosis.

PURPOSE

The purpose of this investigation is to evaluate the extent to which fever is caused by acute PE.

METHODS

Patients participated in the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). Temperature was evaluated among patients with angiographically proven PE. A determination of whether other causes of fever were present was based on a retrospective analysis of discharge summaries, PIOPED summaries, and a computerized list of all discharge diagnoses.

RESULTS

Among patients with PE and no other source of fever, fever was present in 43 of 311 patients (14%). Fever in patients with pulmonary hemorrhage or infarction was not more frequent than among those with no pulmonary hemorrhage or infarction, 39 of 267 patients (15%) vs 4 of 44 patients (9%; not significant). Clinical evidence of deep venous thrombosis was often present in patients with PE and otherwise unexplained fever.

CONCLUSION

Low-grade fever is not uncommon in PE, and high fever, although rare, may occur. Fever need not be accompanied by pulmonary hemorrhage or infarction.

Reassessment of pulmonary angiography for the diagnosis of pulmonary embolism: relation of interpreter agreement to the order of the involved pulmonary arterial branch

PURPOSE

To reassess the validity of conventional pulmonary angiography in the diagnosis of pulmonary embolism (PE) in main, lobar, segmental, and subsegmental pulmonary arteries.

MATERIALS AND METHODS

Data are from examinations of 375 patients with angiographically diagnosed PE who participated in the Prospective Investigation of Pulmonary Embolism Diagnosis. The average co-positivity of readings of the pulmonary angiograms was evaluated in relation to the order of the largest pulmonary artery that showed PE.

RESULTS

Among 217 patients whose angiograms showed PE in main or lobar pulmonary arteries, as well as in smaller orders of arteries, there was an average co-positivity of 98% (95% Cl = 96%, 98%). Among 136 patients whose pulmonary angiograms showed PE in segmental or subsegmental pulmonary arteries but not in larger orders of arteries, the average co-positivity was 90% (95% Cl = 85%, 95%). Among 22 patients with PE limited to the subsegmental arteries, the average co-positivity was 66% (95% Cl = 46%, 86%).

CONCLUSION

Conventional pulmonary angiography is not precise for the diagnosis of PE limited to subsegmental arteries. To evaluate subsegmental arteries, techniques that improve the visualization of PE in small arteries should be used.

The extent to which compensation for the prismatic effects of spectacle lenses is maintained

PURPOSE

The ability of subjects to compensate for the visual displacement caused by the prismatic effects of spectacle lenses was studied over 4 days.

METHODS

Subjects were made myopic using contact lenses and then corrected with spectacles. Pointing behavior was used to assess directional localization. Compensation for the refractive lenses was induced by showing subjects their pointing errors.

RESULTS

Compensation was maintained for 4 days in 3 of 4 subjects despite 24 h of normal viewing between testing sessions. One subject demonstrated a negative directional aftereffect which has not been previously reported in studies of spectacle lens adaptation.

CONCLUSIONS

Compensation for the prismatic effects of spectacle lenses can be maintained for several days in some subjects. This compensation may be functionally useful for some patients who switch between spectacles and contact lenses.

Clinical characteristics of patients with acute pulmonary embolism stratified according to their presenting syndromes

PURPOSE

The purpose of this investigation is to determine the characteristics of the history, physical examination, chest radiograph, and ECG, and the ventilation/perfusion (V/Q) lung scan probability in patients with pulmonary embolism (PE) stratified according to their presenting syndrome.

BACKGROUND

In considering a possible diagnosis of acute PE, it is helpful to consider the patient in terms of the presenting syndrome (pulmonary infarction, isolated dyspnea, or circulatory collapse). In assessing the possibility of acute PE, it would be more useful to know the detailed characteristics of the particular syndrome rather than the clinical characteristics of all patients with PE.

METHODS

Patients described in this investigation participated in the national collaborative trial of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). All had PE diagnosed by pulmonary angiography. None had prior cardiopulmonary disease. All examinations and laboratory tests were obtained within 24 h of the pulmonary angiogram and most were within 12 h of the pulmonary angiogram.

RESULTS

Among patients with the pulmonary infarction syndrome, 14 of 119 (12%) had neither dyspnea nor tachypnea. Some patients with circulatory collapse did not have dyspnea, tachypnea, or pleuritic pain. A normal ECG was more prevalent among patients with pulmonary infarction syndrome, 45 of 97 (46%), than among patients with isolated dyspnea syndrome, 2 of 21 (10%) (p<0.01). A PaO2 >80 mm Hg was also more prevalent in patients with the pulmonary infarction syndrome, 27 of 99 (27%), than in patients with the isolated dyspnea syndrome, 2 of 19 (11%). A high-probability V/Q lung scan was less prevalent among the pulmonary infarction group, 38 of 119 (32%), than the isolated dyspnea group, 20 of 31 (65%) (p<0.001).

CONCLUSION

Many of the findings in the various syndromes of PE can be understood in terms of the severity of PE as it increases from mild with the pulmonary infarction syndrome to moderate with the isolated dyspnea syndrome to severe with circulatory collapse. The prevalence of various clinical and laboratory characteristics of patients with the syndrome of pulmonary infarction, isolated dyspnea, or circulatory collapse may give clues to the diagnosis or suggest characteristics that may reduce the likelihood of inadvertently discarding the diagnosis of PE.

Prevalence of acute pulmonary embolism in central and subsegmental pulmonary arteries and relation to probability interpretation of ventilation/perfusion lung scans

PURPOSE

The purpose of this investigation is to determine the prevalence of acute pulmonary embolism (PE) limited to subsegmental pulmonary arteries.

BACKGROUND

Contrast-enhanced helical (spiral) and electron-beam CT, in the hands of experienced radiologists who are skillful with this modality, are sensitive for the detection of acute PE in central pulmonary arteries, but have a low sensitivity for the detection of PE limited to subsegmental pulmonary arteries. The potential for CT to diagnose PE, therefore, is partially dependent on the prevalence of PE limited to subsegmental pulmonary arteries.

METHODS

Data are from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). The largest pulmonary arteries that showed PE, as interpreted by the PIOPED angiographic readers, were identified in 375 patients in PIOPED with angiographically diagnosed PE.

RESULTS

Among all patients with PE, 6% (95% confidence interval [CI], 4 to 9%) had PE limited to subsegmental branches of the pulmonary artery. Patients with high-probability ventilation/ perfusion (V/Q) scans had PE limited to subsegmental branches in only 1% (95% CI, 0 to 4%). Among patients with low-probability V/Q lung scans, 17% (95% CI, 8 to 29%) had PE limited to the subsegmental branches. Patients with low-probability V/Q scans and no prior cardiopulmonary disease had PE limited to the subsegmental pulmonary arteries in 30% (95% CI, 13 to 53%), whereas patients with low-probability V/Q scans who had prior cardiopulmonary disease had PE limited to subsegmental pulmonary arteries in 8% (95% CI, 2 to 22%) (p < 0.05).

CONCLUSION

Based on data from all patients with PE in PIOPED, the prevalence of PE limited to subsegmental pulmonary arteries is low, 6%. PE limited to subsegmental pulmonary arteries was most prevalent among patients with low-probability V/Q scans, particularly if they had no prior cardiopulmonary disease.

Matched ventilation, perfusion and chest radiographic abnormalities in acute pulmonary embolism

This investigation assessed the positive predictive value of matched ventilation/perfusion (V/Q) and chest radiographic defects (triple-matched defects) for the detection of acute pulmonary embolism (PE).

METHODS

Data are from the Prospective investigation of Pulmonary Embolism Diagnosis (PIOPED). Only patients randomized for obligatory pulmonary angiography were included. Lungs were excluded if they showed any mismatched V/Q defect or any pleural effusion.

RESULTS

Positive predictive values of triple-matched defects in the upper plus middle zones, 1 of 27 (4%), were less frequent than in the lower zones, 13 of 57 (23%) (p < 0.05). Triple-matched defects that involved 25-50% of a zone showed PE in 12 of 38 (32%) which was a higher positive predictive value than with smaller or larger triple-matched defects, 2 of 46 (4%) (p < 0.001).

CONCLUSION

Refinement of the PIOPED data by elimination of nonrandomized patients, elimination of lungs with mismatched perfusion defects and elimination of lungs with a pleural effusion indicate that triple matches with PE (radiographic pulmonary infarcts) are infrequent in the upper and middle lung zones. When a triple match with PE occurs, it is most likely to be 25-50% of a zone.

Small perfusion defects in suspected pulmonary embolism

The purpose of this investigation was to assess the diagnostic value of 1 to 3 versus > 3 small subsegmental defects on perfusion lung scans of patients with suspected acute pulmonary embolism (PE).

METHODS

Data from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were evaluated from patients with suspected acute PE. Angiograms, follow-up data and outcome classifications were used to determine PE status. The perfusion scan of included patients showed only small subsegmental defects ( < 25% of a segment) in the presence of a regionally normal chest radiograph. Findings on the ventilation scan were irrelevant.

RESULTS

The positive predictive value for PE of perfusion lung scans with 1-3 small subsegmental defects was 1% to 3%, depending on the group analyzed. The positive predictive value for the PE of perfusion lung scans with > 3 small subsegmental defects was 11% to 17% depending on the group analyzed.

CONCLUSION

Perfusion lung scans with 1-3 small subsegmental defects satisfy the criterion for a very low probability ( < 10% positive predictive value) for PE and perfusion lung scans with > 3 small subsegmental defects satisfy the criteria for a low probability ( < 20% positive predictive value) for PE.

Pulmonary embolism among patients with a nearly normal ventilation/perfusion lung scan

BACKGROUND

Among patients with nearly normal ventilation/perfusion (V/Q) lung scans in the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED), pulmonary embolism (PE) was diagnosed more frequently in those who underwent pulmonary angiography than in those in whom PE was diagnosed on the basis of an adverse outcome while receiving no anticoagulant therapy. This may suggest that an adverse outcome is not apparent in patients with PE of such mild severity that the V/Q scan is nearly normal. If this were the case, patients with mild PE might not require treatment.

PURPOSE

The purpose of this investigation was to evaluate patients in PIOPED with nearly normal-V/Q lung scans. The V/Q scans and clinical characteristics of those in whom PE was diagnosed or excluded by pulmonary angiography (angiography group) were compared with those in whom PE was diagnosed or excluded by the presence or absence of an adverse outcome while not receiving anticoagulant therapy (outcome group). If the characteristics were the same, it would suggest that some patients with mild PE do well without treatment. If the characteristics were different, it would indicate that there is no evidence from these data that mild PE need not be treated.

METHODS

Data from PIOPED were evaluated from patients with suspected acute PE who had V/Q scans interpreted as nearly normal. There were 75 patients in the angiography group and 90 patients in the outcome group. Patients with entirely normal V/Q scans were excluded.

RESULTS

PE was more frequent in the angiography group than in the outcome group, 8 of 75 (11%) vs 0 of 90 (0%) (p < 0.01). In patients with nearly normal V/Q scans who were in the outcome group in comparison to the angiography group, the V/Q scan showed fewer mismatched segmental perfusion defects, a lower percentage of low-probability V/Q interpretations by one of the two V/Q readers (compared with very low or normal probability), and a generally lower clinical assessment.

CONCLUSION

The observed lower frequency of PE in the outcome group in comparison to the angiography group can be attributed to a lower likelihood of PE in this group of patients with nearly normal V/Q scans in comparison to those who underwent pulmonary angiography. There is no evidence from these data that occasional patients with nearly normal V/Q scans who have PE do not require treatment.

Can pulmonary angiography be limited to the most suspicious side if the contralateral side appears normal on the ventilation/perfusion lung scan? Data from PIOPED. Prospective Investigation of Pulmonary Embolism Diagnosis

PURPOSE

The purpose of this investigation was to determine the frequency of pulmonary embolism (PE) in a single lung that showed a normal ventilation/perfusion (V/Q) lung scan when the V/Q scan on the contralateral side was interpreted as non-high-probability for PE.

METHODS

Data are from the national collaborative study Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). PE was diagnosed or excluded in all lungs by pulmonary angiography.

RESULTS

Single lungs with no V/Q abnormalities, when the V/Q scan on the contralateral side was interpreted as non-high-probability for PE, showed PE in 2 of 19 (11%) (95% confidence interval [CI], 1 to 33%). If PE was excluded by angiography on the side of the abnormal V/Q scan, then PE on the side of the normal V/Q scan was shown in only 1 of 19 (5%) (95% CI, 0 to 26%).

CONCLUSION

A normal V/Q scan in a single lung, when the contralateral lung was interpreted as non-high-probability for PE, did not completely exclude PE on the apparently normal side. In such lungs, the probability of PE was in the range of low-probability interpretations. If the pulmonary angiogram showed no PE on the side of the abnormal V/Q scan, the probability of PE on the side of the normal V/Q scan satisfied the definition of very low probability for PE. This observation in patients undergoing pulmonary angiography may assist in determining whether the pulmonary angiogram should be bilateral.

Patient stratification by cardiopulmonary status in the diagnosis of pulmonary embolism

The purpose of this investigation is to provide further evidence in support of the interpretation of ventilation/perfusion (V/Q) lung scans on the basis of criteria dependent on whether or not the patient has prior cardiopulmonary disease (CPD).

METHODS

Data are from the collaborative PIOPED study. We evaluated the original PIOPED database to obtain the consensus probability estimates of pulmonary embolism (PE) among patients stratified according to the presence or absence of prior CPD.

RESULTS

Among patients with no prior CPD, nuclear physicians consistently underestimated the probability of PE (odds ratio 1.62, 95% confidence interval 1.10-2.38, p = .014).

CONCLUSION

Past experience guided nuclear physicians into correctly estimating the probability of acute PE on V/Q scans of patients with prior CPD. The criteria they subjectively used was inadequate for estimating the probability of acute PE in patients with no prior CPD. Different criteria, therefore, apply to the interpretation of V/Q scans in these two groups.

Scintigraphic lung scans and clinical assessment in critically ill patients with suspected acute pulmonary embolism

PURPOSE

The purpose of this investigation was to evaluate the diagnostic accuracy of radionuclide scintigraphic lung scans and clinical assessment in critically ill patients with suspected acute pulmonary embolism.

MATERIALS AND METHODS

Critically ill patients were defined as follows: (1) patients who were hypoxemic on room air, and not given ventilatory support (n = 89); (2) patients given ventilatory support (n = 46); and (3) patients in ICUs, but not given ventilatory support (n = 85), and hypotensive patients who were not hypoxemic or given ventilatory support (n = 3). Comparisons were made with patients who had none of these characteristics of critically ill patients (n = 627). Data are from the Prospective Investigation of Pulmonary Embolism Diagnosis.

RESULTS

The sensitivities, specificities, and positive predictive values of high probability lungs scans among each of the four categories of critically ill patients were not statistically significantly lower than values in noncritically ill patients. The positive predictive values of the clinical assessments did not differ to a statistically significant extent from noncritically ill patients. Clinical assessment, when concordant with the lung scan interpretation, usually increased the positive predictive value for pulmonary embolism.

CONCLUSION

Scintigraphic lung scans and clinical assessment retain their diagnostic value even in critically ill patients.

Arterial blood gas analysis in the assessment of suspected acute pulmonary embolism

PURPOSE

The utility of arterial blood gas levels in excluding the diagnosis of acute pulmonary embolism (PE) was evaluated.

METHODS

Data are from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). PE was diagnosed or excluded by pulmonary angiography. Among 330 patients with no prior cardiopulmonary disease, 130 patients had PE and 200 did not. Among 438 patients with prior cardiopulmonary disease, 147 had PE and 291 did not. Definitions were low PaO2 (< 80 mm Hg), low PaCO2 (< 35 mm Hg), and high alveolar-arterial oxygen gradient (P(A-a)O2 [> 20 mm Hg]).

RESULTS

Among patients with no prior cardiopulmonary disease who had values of the PaO2 and PaCO2 that were not low and a P(A-a)O2 that was normal, 16 of 42 or 38% (95% confidence interval [CI] = 24 to 54%) had PE. Among patients with prior cardiopulmonary disease who had PaO2 and PaCO2 values that were not low and a P(A-a)O2 that was normal, 4 of 28 or 14% (95% CI = 4 to 33%) had PE. Other combinations of blood gas levels and the P(A-a)O2 gradient, failed to exclude PE in larger percentages of patients.

CONCLUSION

With various combinations of the PaO2 of 80 mm Hg or more, the PaCO2 of 35 mm Hg or higher, and the P(A-a)O2 gradient of 20 mm Hg or less, PE could not be excluded in more than 30% of patients with no prior cardiopulmonary disease and PE could not be excluded in more than 14% of patients with prior cardiopulmonary disease. Blood gas levels, therefore, are of insufficient discriminant value to permit exclusion of the diagnosis of PE.

Prevalence of acute pulmonary embolism among patients in a general hospital and at autopsy

PURPOSE

The purpose of this investigation is to estimate the prevalence of acute pulmonary embolism (PE) in a general hospital, its frequency among patients who died, and the ability of physicians to diagnose PE antemortem.

METHODS

The prevalence of acute PE among 51,645 patients hospitalized over a 21-month period was assessed in 1 of the 6 clinical centers (Henry Ford Hospital) that participated in the collaborative study, prospective investigation of pulmonary embolism diagnosis (PIOPED). The diagnosis of PE was made by pulmonary angiography, or in those who did not undergo pulmonary angiography because they declined or were ineligible for randomization to angiography in PIOPED, the diagnosis was based on the ventilation/perfusion (V/Q) lung scan. Based on data in PIOPED, PE was considered to be present in 87% of patients with high probability V/Q scam interpretations, 30% with intermediate probability interpretations, 14% with low probability interpretations, and 4% with nearly normal V/Q scans.

RESULTS

The estimated prevalence of acute PE in hospitalized patients was 526 of 51,645 (1.0%; 95% confidence interval [CI], 0.9 to 1.1%). Based on extrapolated data from autopsy, PE was estimated to have caused or contributed to death in 122 of 51,645 (0.2%; 95% CI, 0.19 to 0.29%). Pulmonary embolism was observed at autopsy in 59 of 404 (14.6%; 95% CI, 11.3 to 18.4%). Among patients with PE at autopsy, the PE caused or contributed to death in 22 of 59 (37.3%; 95% CI, 25.0 to 50.9%) and PE was incidental in 37 of 59 (62.7%; 95% CI, 49.1 to 75.0%). Among patients at autopsy who died from PE, the diagnosis was unsuspected in 14 of 20 (70.0%; 95% CI, 45.7 to 88.1%). Most of these patients had advanced associated disease. In these patients, death from PE occurred within 2.5 h in 13 of 14 (92.9%; 95% CI, 66.1 to 99.8%).

CONCLUSION

Pulmonary embolism is common in a general hospital. The prevalence of PE at autopsy has not changed over 3 decades. The frequency of unsuspected PE in patients at autopsy has not diminished. Even among patients who die from PE, the PE is usually unsuspected. Such patients, however, typically have advanced disease. Among moribund patients, incidental PE is rarely diagnosed. Patients who suffer sudden unexplained catastrophic events in the hospital are a group in whom the diagnosis might be suspected more frequently if physicians maintain a high index of suspicion.

Continuing risk of thromboemboli among patients with normal pulmonary angiograms

PURPOSE

The purpose of this investigation was to determine the frequency of future pulmonary embolism (PE) among patients in whom PE was suspected and excluded by pulmonary angiography.

METHODS

Data are from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). The present investigation includes 380 patients in whom PE was excluded by pulmonary angiography and who received no anticoagulant therapy while in the hospital or after discharge. Patients were followed 1 year after their normal pulmonary angiograms.

RESULTS

Pulmonary embolism occurred within 1 year in 6 of 380 (1.6%)(95% confidence interval [CI] 0.3 to 2.9%) patients with suspected PE and normal pulmonary angiograms. Four of six (67%) PE were nonfatal. Three of six (50%) PE occurred in the first 8 days and four of six (67%) PE occurred within the first month. Among patients who subsequently showed PE, a history of thrombophlebitis or an objective test suggestive of deep venous thrombosis was present in five of six (83%). Symptoms, signs, and radiographic abnormalities were similar among patients who showed PE on follow-up and those who did not, although the pulmonary artery mean pressure was higher among those with subsequent PE (34 +/- 25 mm Hg vs 22 +/- 10 mm Hg) (p < 0.01).

CONCLUSION

The frequency of PE on follow-up among patients with normal pulmonary angiograms is small. There is, however, a real and measureable rate of clinically important PE over the subsequent 12 months that is higher than reported in the general population of hospitalized patients. Patients with suspected PE, therefore, even if their angiogram is normal, might benefit from definitive studies of the lower extremities to exclude deep venous thrombosis. The cost benefit ratio of this, however, has not been evaluated.

Asymmetry of the calves in the assessment of patients with suspected acute pulmonary embolism

PURPOSE

The purpose of this investigation was to evaluate measured asymmetry of the calves in the assessment of patients with suspected pulmonary embolism (PE).

METHODS

Patients randomized for pulmonary angiography in the collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were evaluated. Only patients in whom the circumference of the calves was measured were included in this evaluation of PIOPED data. Among these, 232 had angiographically diagnosed PE and 446 had no PE by angiography. For purposes of comparison, measurements of the calves also were made in a nonrandomized current cohort of 101 healthy subjects. All calf measurements were made 10 cm below the tibial tuberosity.

RESULTS

Asymmetry in the circumference of the calves of 1 cm or more was measured in 101 of 232 or 44% (95% confidence interval [CI], 37 to 51%) with PE, 176 of 446 or 39% (95% CI, 34 to 44%) without PE, and in 6 of 101 or 6% (95% CI, 1 to 11%) control subjects (PE vs control subjects, p < 0.001; subjects without PE vs control subjects, p < 0.001; PE vs no PE, p = NS). Among patients with PE, the addition of calf asymmetry of 1 cm or more to qualitative signs of deep venous thrombosis increased the prevalence of a detectable abnormality of the lower extremities from 62 of 232 or 27% (95% CI, 21 to 33%) to 129 of 232 or 56% (95% CI, 49 to 63% [p < 0.001]).

CONCLUSION

Asymmetry of the calves of 1 cm or more is abnormal. Such asymmetry of the calves did not distinguish between patients with PE and those with no PE. When considered in proper perspective with other nonspecific signs and symptoms in patients with suspected acute PE, however, subtle calf asymmetry may call attention to the possibility of thromboembolic disease. The observation of subtle asymmetry may indicate a need for noninvasive diagnostic tests of the lower extremities to determine whether deep venous thrombosis is present.

Untreated patients with pulmonary embolism. Outcome, clinical, and laboratory assessment

PURPOSE

The purpose of this investigation was to evaluate the clinical characteristics of acute pulmonary embolism (PE) among patients with PE who did not receive treatment to assess how the natural course of untreated PE relates to its severity.

METHODS

Data are from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). Among patients with PE diagnosed either by pulmonary angiography or at autopsy, 376 received treatment and 24 escaped treatment in the hospital and were not prescribed anticoagulant therapy at the time of hospital discharge. Among these untreated patients, however, four received anticoagulant therapy during the first 3 months of follow-up. We report the 3-month course of PE in the remaining 20 untreated patients.

RESULTS

Among untreated patients, 1 of 20 (5.0%) died from the effects of the original PE and possibly some contribution from recurrent PE. Nonfatal recurrent PE occurred in 1 of 20 (5.0%). All untreated patients, 20 of 20 (100%), had less than three mismatched segmental perfusion defects compared with 227 of 376 (60%) treated patients (p < 0.001). Pulmonary arteries showed thromboemboli in segmental or smaller arteries in 16 of 19 (84%) untreated patients compared with 132 of 362 (36%) treated patients (p < 0.001). Untreated and treated patients, when grouped according to the size of the ventilation/perfusion lung scan defect or size of vessels involved on the pulmonary angiogram, showed no statistically significant difference in the frequency of fatal PE or nonfatal recurrent PE.

CONCLUSION

Mild untreated PE carries a lower immediate mortality and lower mortality from recurrent PE than overt PE described in prior decades.

Alveolar-arterial oxygen gradient in the assessment of acute pulmonary embolism

PURPOSE

The purpose of this investigation is to evaluate the utility of the alveolar-arterial (A-a) oxygen gradient in the diagnosis of acute pulmonary embolism (PE) among patients who participated in the Prospective Investigation of Pulmonary Embolism Diagnosis (PIO-PED).

METHODS

Pulmonary embolism was diagnosed (n = 280) or excluded (n = 499) by angiography in all patients. Patients were then categorized as (1) the entire cohort, (2) no prior cardiopulmonary disease and no prior PE, and (3) no prior PE or deep venous thrombosis. Normal values of the A-a gradient were defined in three ways: (1) values < or = 20 mm Hg; (2) values < or = age/4 + 4; and (3) values based on age from the literature.

RESULTS

When a normal A-a gradient was defined as < or = 20 mmHg, 11 to 14% of patients with PE in the three categories of patients had a normal A-a gradient. When the equation age/4 + 4 was used, 8% to 10% of patients with PE in the three categories of patients had a normal A-a gradient. With age-related values from the literature, 20 to 23% of patients with PE in the three categories of patients had a normal A-a gradient. The A-a gradient was normal in comparable percentages of patients who did not have PE.

CONCLUSION

Normal values of the A-a gradient did not exclude the diagnosis of acute PE.

Right ventricular dilatation, right ventricular wall thickening, and Doppler evidence of pulmonary hypertension in patients with a pure restrictive ventilatory impairment

The purpose of this investigation was to determine the severity of pure restrictive ventilatory impairment that results in right ventricular (RV) dilatation, increased RV wall thickness, and pulmonary hypertension. Two dimensional (2-D) echocardiography, Doppler measurements of pulmonary flow, and spirometry were performed on 26 unselected patients (17 female, 9 male) with a pure restrictive ventilatory impairment. A restrictive ventilatory impairment was defined as a forced vital capacity (FVC) < or = 80 percent predicted with a normal FEV1/FVC ratio (FEV1 = 1 s forced expiratory volume). The patients were grouped according to the severity of the restrictive ventilatory defect: mild (FVC, 65 to 80 percent predicted), moderate (FVC, 51 to 64 percent predicted), and severe (FVC < or = 50 percent predicted). An increased RV area (> 20.4 cm2) was shown in 0 of 10 (0 percent) patients with a mild impairment, 6 of 12 (50 percent) patients with moderate restriction, and 2 of 4 (50 percent) patients with severe restriction. Increased RV wall thickness (> 0.5 cm) was observed in 0 of 10 (0 percent) patients with mild restrictive impairment, 3 of 12 (25 percent) with moderate impairment, and 1 of 4 (25 percent) with severe restrictive impairment. Doppler evidence of pulmonary hypertension (ACT/ET ratio < 0.32) (ACT = acceleration time, ET = ejection time) was shown in 0 of 10 (0 percent) patients with a mild restrictive impairment, 8 of 12 (66 percent) patients with moderate restriction, and 4 of 4 (100 percent) patients with severe restriction (p < 0.01 mild vs moderate and mild vs severe). The RV area by 2-D echocardiography correlated well with the FVC percent predicted (r = 0.90, p < 0.001). The ACT/ET ratio also correlated well with the FVC percent predicted (r = 0.73, p < 0.001). In conclusion, RV enlargement and pulmonary hypertension were seen only in patients with a moderate or severe restrictive ventilatory impairment. These data may be useful in the assessment of the likelihood of subtle RV enlargement in patients with occupational pleuropulmonary disease.

Chest radiographs fail to detect right ventricular enlargement and right atrial enlargement in patients with a pure restrictive ventilatory impairment

The validity of measurements of the cardiac silhouette on chest radiographs for the evaluation of right ventricular enlargement and right atrial enlargement in patients with a pure restrictive ventilatory impairment was investigated in 19 patients. The forced vital capacity (FVC) percent predicted in these patients was 59 +/- 12 percent (mean +/- SD) (range, 29 to 79 percent). Right ventricular enlargement, by two-dimensional echocardiography, was defined as a right ventricular area > 20.4 cm2 and right atrial enlargement was defined as a right atrial area > 15.3 cm2. Chest radiographic measurements in the posteroanterior (PA) projection included distance from the midline to the farthest point of the right border of the cardiac silhouette, transverse cardiac diameter, and cardiothoracic ratio. Measurements in the lateral projection included the lateral horizontal transverse diameter, ventral portion of the lateral broad diameter, and obliteration of the retrosternal space. Neither the right ventricular area nor the right atrial area correlated with any of these radiographic measurements. There were no differences in these chest radiographic measurements among patients with normal right ventricular and right atrial dimensions, patients with right ventricular enlargement, and patients with right atrial enlargement. We conclude, therefore, that PA and lateral chest radiographs do not reliably detect right ventricular enlargement or right atrial enlargement in patients with a pure restrictive ventilatory impairment.

Effects of cyclic flexion of coronary arteries on progression of atherosclerosis

The purpose of this investigation was to test the hypothesis that cyclic flexion of the coronary arteries contributes to the progression of atherosclerotic plaques. Coronary arteriograms were evaluated in 33 unselected patients who underwent 2 studies over a period of 25 +/- 16 months (mean +/- SD). Among the 33 patients, 103 plaques were identified. Plaques that showed progression were compared with plaques that showed no progression. The angle of flexion that occurred during systole at the site of the plaque was measured on the first arteriogram. In comparing progression versus no progression, the interval between arteriograms was 29 +/- 18 versus 23 +/- 14 months (p = NS) and percent stenosis at the first arteriogram was 42 +/- 28 versus 45 +/- 19% (p = NS). Percent stenosis at the time of the second arteriogram among plaques that progressed was 78 +/- 21%, and by definition, it remained 45 +/- 19% among those that did not progress. Among arteries with plaques that showed a progression of stenosis, the angle of flexion during systole was 19 +/- 13 degrees versus 9 +/- 15 degrees among arteries with plaques that did not progress (p < 0.01). Linear regression showed that the correlation of the angle of flexion with percent change of stenosis was relatively low (r = 0.32) but statistically significant (p < 0.005). Mathematic modeling of flexible and stiff plaques showed stresses approximately 1.5 to 1.9 times greater with 20 degrees than with 10 degrees flexion. Stresses due to flexion were usually greatest proximal and distal to the plaque along the subendothelial layer of the inner wall of the curved vessel. Data show that the angle of cyclic flexion, and consequently the stresses due to cyclic flexion of the artery were greatest in the region of plaques that progressed over the period of observation. Such stresses may have contributed to tissue damage of fatigue resulting in a more rapid progression of the atheromatous plaques.

Neural network in the clinical diagnosis of acute pulmonary embolism

The purpose of this investigation was to test the hypothesis that computer-based pattern recognition can accurately assess the likelihood of acute pulmonary embolism (PE) based on readily obtainable clinical characteristics. Data were obtained from 1,213 patients who participated in the collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). Characteristics of the history, physical examination, electrocardiograph, chest radiograph, and arterial blood gases of patients with suspected acute PE were presented to a back propagation neural network. The 1,213 patients were divided into training set A (n = 606) and test set B (n = 607). These groups were then reversed into training set B (n = 607) and test set A (n = 606). A receiver operating characteristic (ROC) curve was constructed from PIOPED clinical assessment, and from neural network clinical assessment in groups A and B. Areas under the respective ROC curves were 0.7450, 0.7477, and 0.7324. All differences were not significant. Areas under ROC curves for PIOPED clinical assessment combined with ventilation/perfusion (V/Q) scan results were compared with neural network clinical assessment combined with V/Q scan results in groups A and B. The respective ROC areas were 0.8324, 0.8203, 0.8496 (all differences not significant). These data show that neural networks were able to predict the clinical likelihood of PE with an accuracy comparable to experienced clinicians.

Mismatched vascular defects. An easy alternative to mismatched segmental equivalent defects for the interpretation of ventilation/perfusion lung scans in pulmonary embolism

The purpose of this investigation was to test the hypothesis that ventilation/perfusion (V/Q) lung scans in patients with suspected acute pulmonary embolism (PE) can be evaluated on the basis of the total number of mismatched vascular defects, irrespective of whether such defects are moderate or large size segmental defects. Lung scan data from the national collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were assessed in 383 patients with acute PE and 681 patients in whom suspected PE was excluded. The predictive value of the cumulative number of mismatched moderate size segmental defects (irrespective of the number of mismatched large segmental defects) was nearly the same as that of mismatched large segmental defects (irrespective of the number of mismatched moderate size segmental defects). This suggests that the diagnostic value of mismatched moderate size segmental defects is the same as mismatched large segmental defects. Lung scans evaluated on the basis of the number of mismatched vascular defects (moderate and/or large segmental defects) were compared with V/Q scans evaluated on the basis of the number of mismatched segmental equivalents. The maximum likelihood estimates of the areas under the receiver operating characteristic (ROC) curves for the number of mismatched vascular defects and for mismatched segmental equivalents were similar (0.8512 vs 0.8530) (NS). Stratification according to the presence or absence of prior cardiopulmonary disease permitted a more accurate assessment of both clinical groups. Evaluation of V/Q scans by vascular defects and by segmental equivalents showed similar areas under the ROC curves. In conclusion, the number of mismatched vascular defects is as powerful for the assessment of V/Q scans as the number of mismatched segmental equivalents. The number of mismatched vascular defects, however, is easier to interpret, and permits a more objective evaluation.

Stratification of patients according to prior cardiopulmonary disease and probability assessment based on the number of mismatched segmental equivalent perfusion defects. Approaches to strengthen the diagnostic value of ventilation/perfusion lung scans in acute pulmonary embolism

A categorical diagnosis of "high probability" or "intermediate probability" encompasses a spectrum of diagnostic probabilities of pulmonary embolism (PE) that is not communicated to the referring physician. The diagnostic value of ventilation/perfusion lung scans, in the present investigation, was strengthened by use of a table to determine the likelihood of PE in individual patients on the basis of the observed number of mismatched segmental equivalent perfusion defects. In addition, we tested the hypothesis that stratification of patients according to the presence or absence of prior cardiopulmonary disease may enhance the ventilation/perfusion scan assessment of the probability of PE among both of these clinical categories of patients. Data were derived from the collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). Ventilation/perfusion lung scans were evaluated in 378 patients with acute PE and 672 patients in whom suspected PE was excluded. Among patients with no prior cardiopulmonary disease, > or = 1.0 mismatched segmental equivalents was indicative of PE in 102 of 118 (86 percent) vs 113 of 155 (73 percent) among patients with prior cardiopulmonary disease (p < 0.02). Among patients with prior cardiopulmonary disease, > or = 2 mismatched segmental equivalents were required to indicate > or = 80 percent probability of PE. Stratification on the basis of the presence or absence of prior cardiopulmonary disease, therefore, enhanced the ability of ventilation/perfusion scan readers to assign an accurate positive predictive value and specificity to individual patients based on the observed number of mismatched segmental equivalent defects. Among patients with no prior cardiopulmonary disease, fewer mismatched segmental equivalent defects were required to indicate a high probability of PE than were required by PIOPED criteria. The findings from some of these patients, by PIOPED criteria, would have indicated intermediate probability. Some indeterminate probability readings, therefore, will be eliminated among patients stratified with no prior cardiopulmonary disease.

The addition of clinical assessment to stratification according to prior cardiopulmonary disease further optimizes the interpretation of ventilation/perfusion lung scans in pulmonary embolism

The purpose of this investigation was to test the hypothesis that prior clinical assessment among patients stratified according to the presence or absence of prior cardiopulmonary disease enhances the accuracy of the predictive value of pulmonary embolism (PE) in the various categories. Diagnostic evaluation was made on the cumulative spectrum of mismatched defects, rather than a probability based on a preassigned number of mismatched segmental equivalent defects or mismatched vascular defects. Families of curves were derived that allowed an accurate assessment of the predictive value for each category of patients. The families of curves were comparable, irrespective of whether ventilation/perfusion scans were assessed on the basis of mismatched segmental equivalent defects or mismatched vascular defects, although the latter eliminated the necessity of estimating whether segmental defects were large or moderate in size. Clinical assessment was shown to prominently affect the predictive value of PE. Prior clinical assessment among patients stratified according to prior cardiopulmonary disease enhanced the accuracy of the predictive value of PE in the various groups of patients.

Left ventricular wall tension and stress during exercise in athletes and sedentary men

This investigation examines the hypothesis that hypertrophy attenuates wall stress during exercise, when left ventricular wall tension is highest and most likely to contribute to hypertrophy. Upright bicycle exercise was performed by 17 endurance-trained male athletes and 15 sedentary men. M-mode echocardiograms were obtained during submaximal exercise at predetermined heart rates. At all levels of exercise, at a matched heart rate, wall tension was higher in athletes than in sedentary subjects. In both groups, wall tension increased with exercise, then plateaued. Wall stress did not differ significantly in athletes and sedentary subjects at rest and at heart rates of 110 and 150 beats/min, although a difference was observed at a heart rate of 130 beats/min. Wall stress decreased in both athletes and sedentary subjects with exercise. In conclusion, left ventricular hypertrophy caused wall stress in athletes to be maintained at values similar to sedentary subjects during exercise as well as at rest.

Left ventricular response to submaximal exercise in endurance-trained athletes and sedentary adults

This investigation examines the hypothesis that athletes increase stroke volume with submaximal exercise through an augmentation of left ventricular (LV) end-diastolic volume and a reduction of LV end-systolic volume, whereas sedentary adults only increase stroke volume modestly, because LV end-diastolic volume does not increase. Upright bicycle exercise was performed by 17 endurance-trained male athletes and 15 sedentary men. M-mode echocardiograms were obtained during submaximal exercise at predetermined heart rates. Athletes, at a heart rate of 130 beats/min, increased their stroke volume 67% from 72 +/- 18 ml to 120 +/- 26 ml (p less than 0.001). This resulted from an increase of LV end-diastolic volume from 119 +/- 23 to 152 +/- 28 ml (p less than 0.001) and a reduction in LV end-systolic volume from 46 +/- 14 to 31 +/- 9 ml (p less than 0.001). Sedentary men at the same heart rate increased stroke volume 22% from 63 +/- 15 to 77 +/- 21 ml (p less than 0.05). LV end-diastolic volume did not change (96 +/- 20 vs 97 +/- 28 ml) (p = not significant), but LV end-systolic volume decreased (33 +/- 11 vs 20 +/- 9 ml) (p less than 0.001). In conclusion, athletes increased cardiac output through a more prominent augmentation of stroke volume than sedentary subjects at submaximal exercise. This was accomplished through an augmentation of LV end-diastolic volume. This may have a conserving effect on myocardial oxygen consumption at these levels of exercise.

Relation of plain chest radiographic findings to pulmonary arterial pressure and arterial blood oxygen levels in patients with acute pulmonary embolism

Abnormalities of the plain chest radiograph of 123 patients with acute pulmonary embolism (PE) and no prior cardiac or pulmonary disease were related to the pulmonary arterial mean pressure, the partial pressure of oxygen in arterial blood, and the alveolar-arterial oxygen gradient. Patients with either a prominent central pulmonary artery or cardiomegaly had higher pulmonary arterial mean pressures than did patients with atelectasis, a pulmonary parenchymal abnormality or pleural effusion (p less than 0.001). These radiographic findings give clues to the severity of pulmonary hypertension in acute PE and suggest that pulmonary infarction or hemorrhage is associated with less severe PE.