Biomedical subjects
W T Miller
Publications and source records attributed to W T Miller.
Subcutaneous emphysema in a young man.
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Tuberculosis in the immunosuppressed patient.
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Extracellular potentials related to intracellular action potentials during impulse conduction in anisotropic canine cardiac muscle.
This paper considers a quantitative description of intracellular and transmembrane currents in anisotropic muscle, with emphasis on the factors that determine the extracellular potentials. Although Vmax of the intracellular action potential had no relation to changes in conduction velocity in anisotropic tissue with constant membrane properties, the extracellular waveforms were quite sensitive to velocity changes. Large amplitude biphasic deflection occurred in the fast areas, and in the slow areas the waveforms were of lower amplitude and triphasic in shape; i.e., negative potentials preceded the biphasic positive-negative deflection. The extracellular potentials were simulated on the bases of a model of intracellular currents, and the theoretical and measured results showed good agreement. In tissue with anisotropic conductivity, the relationship between the spatial intracellualr potential gradient and the magnitude of the extracellular potential of the excitation wave was opposite to the classical relationship in isotropic tissue. Due to the influence of the effective intracellular conductivity on the spread of intracellular currents and on conduction velocity, in anisotropic tissue the extracellular potential decreased as the intracellular potential gradient increased. The peak values of the positive and negative potentials and the spatial distribution of the potential gradients varied considerably along the activation front. These findings were accounted for by differences in the distribution and spatial extent of the transmembrane currents, which were determined by the intracellular currents. The theoretical analysis showed that intracellular and transmembrane currents were proportional to the local conduction velocities of the wavefront. Thereby, it was not possible to have a "uniform layer" of current when there were differences in conduction velocity along the length of the excitation wave. The implications of the analysis are considerable, since the gratifying agreement between the theoretical and measured results indicates that the details of the extracellular waveforms can be explained on the basis of the distribution of intracellular currents; i.e., extracellular potentials provide a sensitive index of intracellular current flow.
Summertime pneumonias in Philadelphia in 1976. An epidemiologic study.
Summertime pneumonias in Philadelphia during 1976 were studied epidemiologically, and the epidemiologic, clinical, and laboratory features of pneumonia cases serologically positive for Legionnaires' disease were compared with features of serologically negative cases. Both groups were similar in many respects, but in patients with Legionnaires' disease diarrhea and neurologic findings were significantly more frequent (P = 0.01 and P = 0.05 respectively). A diagnosis of Legionnaires' disease was also suggested by an elevated serum creatinine phosphokinase level (P = 0.02) and the presence of occult blood in the urine with fewer than six erythrocytes per highpower field. Abnormalities in renal function tests or liver function tests were commoner in patients with Legionnaires' disease (P = 0.05). Radiographic features, however, could not be used to separate pneumonia cases. The high frequency of extrapulmonary manifestations involving the gastrointestinal tract, the central nervous system, kidneys, and liver suggests that Legionnaires' disease is a multisystemic disorder possibly caused by a toxin-producing organism.
Simulation studies of the electrocardiogram. I. The normal heart.
A digital computer model is presented for the simulation of the body surface electrocardiogram (ECG) during ventricular activation and recovery. The ventricles of the heart are represented in detail by a three-dimensional array of approximately 4000 points which is subdivided into 23 regions. Excitation sequence and cellular action potential data taken from the literature are used to determine the spatial distribution of intracellular potentials at each instant of time during a simulated cardiac cycle. The moment of the single dipole representing each region is determined by summing the spatial gradient of the intracellular potential distribution throughout the region. The resulting set of 23 dipoles is then used to calculate the potentials on the surface of a bounded homogeneous volume conductor with the shape of an adult torso. Simulated isopotential surface maps during both activation and recovery are in good agreement with data for humans reported in the literature.
Simulation studies of the electrocardiogram. II. Ischemia and infarction.
Experimental studies of the myocardial action potentials following coronary artery occlusion have shown that the resulting regional ischemia is reflected by characteristics changes in the shapes of the action potentials in the ischemic region. The principal changes are decreases in the magnitude of the resting potential and in the action potential duration. Action potentials with prolonged durations have been observed in the infarcted regions of experimental animals after the development of inverted T waves in the surface electrocardiogram (ECG). We use such abnormal action potentials in our digital computer model to study the effects of acute myocardial ischemia and infarction on the surface ECG. The heart is represented in sufficient detail to allow variations in the location and size of the ischemic injury and in the distribution of the severity of injury within the injured region. The evolution of acute infarctions is simulated by progressively modifying the abnormal action potentials assigned to the injured region. Calculated standard 12 lead ECGs and torso isopotential surface maps for simulated acute ischemia and infarction are in good agreement with patient data reported in the literature. Typical simulations include anterior and inferior transmural ischemia and infarction and anterior subendocardial ischemia. The model is used to examine relationships between torso surface potentials during ventricular activation and recovery and the site and size of the ischemic injury.
Long-term therapy with rifampin and the secondary antibody response to killed influenza vaccine.
The secondary antibody response was studied in 22 patients with tuberculosis, 11 of whom were taking rifampin as part of their antituberculous regimen. The mean duration of rifampin therapy was 12.7 months. Hemagglutination-inhibiting antibody titers to bivalent influenza vaccine were determined before, and 4 and 8 weeks after, vaccination. There was no significant difference in the number of patients who developed a 4-fold or greater increase in titer, or in the level of titer response between the rifampin and control groups. Long-term therapy with rifampin was not found to suppress the secondary antibody response to influenza vaccination.
Tuberculosis: frequency of unusual radiographic findings.
The changing pattern of the radiologic presentation of tuberculosis was noted in a review of 100 consecutive cases of pulmonary tuberculosis. Active tuberculosis was not suggested as a radiologic diagnosis in 43% of the patients. Of the 100 cases, only 66 had characteristics of reactivation tuberculosis (i.e., minimal upper lobe infiltrate or more advanced cavitary disease). Of the other 34 patients, 18 had less usual presentations, making the radiographic diagnosis difficult. The remaining 16 patients had radiographic patterns quite unusual for tuberculosis, including masslike densities resembling carcinoma; chronic infiltrates in a lower lobe; miliary tuberculosis, either superimposed on diffuse interstitial lung disease or associated with a diffuse lung pattern atypical for miliary disease; and normal chest radiograph.
Bronchioloalveolar carcinoma: two clinical entities with one pathologic diagnosis.
Bronchioloalveolar carcinoma may present with a variety of radiologic and clinical patterns. Two types of this primary carcinoma of the lung have been recognized: a solitary lesion and a diffuse form. Charts and radiographs of 61 cases of bronchioloalveolar carcinoma were reviewed as well as the pertinent literature. Our experience indicates that the localized form seldom, if ever, becomes diffuse and has a good prognosis following appropriate surgery (lobectomy or pneumonectomy). If the lesion is diffuse, death almost invariably results within 3 years. Based on available clinical information, we suggest that at least two primary tumors of the lung have the histologic pattern of bronchioloalveolar carcinoma: one of these tumors is diffuse and the other is solitary.
A clinical and pathological staging system for soft tissue sarcomas.
A system for staging the clinical status of patients with soft tissue sarcomas is presented, based on the clinical characteristics of the primary tumor (size, extension), the involvement of lymph nodes, the presence of metastases, and the grade of the tumor. This represents the TNM system with grade of tumor (G) added. The system evolved was based on examination of 1215 cases of 13 types of soft tissues sarcomas, primarily in the extremities (fibrosarcoma, liposarcoma, etc.). Nine stages are described, and they are correlated with survival in the cases reviewed. The staging system now can be used for case evaluation for therapy determination and for intercomparison of series of patients as to incidence of different kinds of tumors, effects of treatment, and survival.
Roentgenogram of the month. Right paratracheal shadow in an asymptomatic young man.
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Von Recklinghausen's disease: incidence of roentgenographic findings with a clinical review of the literature.
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Sarcoidosis: a multisystem disease.
Most commonly, sarcoid involves the lungs and thoracic lymph nodes, liver, skin and eyes. The heart, gastrointestinal tract, kidneys and brain may also be involved. The classic form of lymphadenopathy involves both hilar areas and the mediastinum, producing the "1, 2, 3 sign." Adenopathy generally precedes parenchymal pulmonary involvement, which may take several forms.
The esophagus in collagen disease. Radiologic findings.
A prospective cineradiographic and manometric study of pharyngeal and esophageal dysfunction was performed in 54 patients with rigidly defined scleroderma, polymyositis, systemic lupus erythematosus, and rheumatoid arthritis. Cineradiography was inaccurate in pharyngeal dysfunctions specific for polymyositis. Manometry was an accurate but insensitive test. Manometry was also significantly more accurate than cineradiography in identifying patients with smooth muscle dysfunction (scleroderma). Cineradiographic finding of absent esophageal peristalsis accurately identified patients with scleroderma but it identified only a small percentage (33 percent). Cineradiography finding of diminished esophageal peristalsis was found in scleroderma (23 percent), polymyositis, (30 percent), and SLE (11 percent) and has been reported in rheumatoid arthritis. This finding is a non specific finding suggestive of collagen vascular disease rather than specific for scleroderms.
Prospective, randomized study of diagnosis and outcome in acute upper-gastrointestinal bleeding: endoscopy versus conventional radiography.
Sixty patients with mild to moderate upper-gastrointestinal bleeding were admitted to a prospective, controlled study of diagnosis and management, and were randomized to endoscopy or upper-gastrointestinal (UGI) barium series as the initial study. Definitive localization of the source of bleeding was made initially in 69% of the endoscopy group and 21% of the UGI group (P less than 0.0005). Of 54 patients undergoing both studies, endoscopy was definitive in 67% and UGI series in 22%. Thus, endoscopy also made more diagnoses when used as the second study (P less than .01). The use of endoscopy as the initial procedure led to significantly more rapid diagnosis than with UGI series. However, there were no significant differences between the two groups in clinical outcome. Endoscopy is the initial diagnostic procedure of choice in patients with mild to moderate upper-gastrointestinal bleeding because it enables detection of superficial bleeding lesions and has significantly increased the speed of diagnosis.
Asbestos exposure and multiple primary tumors.
Recently we observed 5 patients with multiple primary tumors who also had a history of occupational asbestos exposure. Two patients had a lung carcinoma and a colon carcinoma and 3 others had 2 distinct pulmonary carcinomas. Most of the attending physicians were unaware of the patient's occupational risk for asbestos exposure and the resultant health hazards. Therefore, we review the uses of asbestos and occupations at risk for asbestos exposure.