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Biomedical subjects

R D Underwood

Publications and source records attributed to R D Underwood.

13 recordsLinked to original sources
PubMed1997

Evaluation and treatment strategies in patients at high risk of sudden death post myocardial infarction.

Over 50 percent of deaths in patients who survive an acute myocardial infarction are due to fatal ventricular tachyarrhythmias. Patients who survive an episode of sustained ventricular arrhythmia are at highest risk of recurrent cardiac arrest. Electrophysiologic studies have been found to be useful in guiding therapy and reducing mortality in these patients and in patients with syncope due to arrhythmic etiology. Evaluation and treatment of nonsustained ventricular tachycardia post infarction remains somewhat controversial. A recently published trial (MADIT), however, showed improved survival with an implanted defibrillator in patients with coronary disease and asymptomatic nonsustained ventricular tachycardia. Asymptomatic patients post infarction at high risk include those who have significant left ventricular dysfunction, late potentials, high-grade ventricular ectopy, and abnormal heart rate variability. These tests individually, however, have a low positive predictive accuracy. This, combined with the fact that antiarrhythmic drugs are frequently not effective and can be proarrhythmic, leaves the best treatment for these patients uncertain. It is known, however, that beta-adrenoreceptor blocking agents do reduce mortality after an acute myocardial infarction. Early studies have shown mixed results relating to sudden death and total mortality with amiodarone. To date, no other antiarrhythmic drug has shown benefit, while several have been shown to be harmful. Recent studies have also shown some beneficial effects of angiotensin-converting enzyme inhibitors, carvedilol, a third-generation beta-blocking agent with vasodilator properties, and the angiotensin II receptor antagonist losartan. However, their precise role in reducing sudden death needs to be defined further.

Anti-Arrhythmia Agents↗
PubMed1997

The effect of polarity of the initial phase of a biphasic shock waveform on the defibrillation threshold of pectorally implanted defibrillators.

The effect of initial phase polarity on the DFT of two pectorally implanted biphasic ICDs was tested in a randomized, prospective manner at the time of implantation. Twenty-two consecutive patients with VT-VF who received either the Medtronic PCD 7219C Jewel device (10 patients) or PCD 7219D Jewel device (12 patients) were studied. DFT testing was performed in a standard step-down manner. Both initial phase polarities--initial defibrillation current flowing from active can/SVC coil +/- subcutaneous patch) to the RV coil (RV coil to active can/SVC (RV+)--were tested in random order. The mean DFT achieved with RV+ compared with RV-was lower for the 7219C patient group (6.6 +/- 3.1 vs 10.8 +/- 5.5 J; P = 0.007). A similar trend was observed for the 7219D group, though the difference did not reach statistical significance (12.0 +/ 4.0 vs 16.3 +/- 7.3 J; P = 0.07). Seven of the 10 patients in the 7219C group had a lower DFT with RV+, while the initial phase polarity made no difference in 3. In the 7219D group, 7 patients had a lower DFT using RV+, 2 patients had a lower DFT using RV-, and the initial phase polarity made no difference in 3. In conclusion, this study demonstrates that changing the polarity of the initial phase of a biphasic shock waveform can have a significant impact on the DFT achieved at the time of ICD implantation.

Aged↗
PubMed1995

Influence of intimal thickening on coronary blood flow responses in orthotopic heart transplant recipients. A combined intravascular Doppler and ultrasound imaging study.

BACKGROUND: Intravascular ultrasound imaging detects epicardial intimal thickening in the majority of heart transplant recipients with angiographically normal epicardial coronary arteries. Although coronary artery vasoreactivity is abnormal after cardiac transplantation, intimal thickening does not appear to affect conduit vessel responses. However, the effect of intimal thickening on both conduit and resistance vessel responses, as measured by changes in volumetric coronary blood flow (CBF), is unknown. METHODS AND RESULTS: Epicardial coronary artery conductance and microvascular resistance vessel responses were studied after intracoronary adenosine and nitroglycerin administration in 36 orthotopic heart transplant recipients 1 month to 7 years after transplantation. Sequentially measured coronary flow average peak velocity ([APV, cm/s] 0.018 in Doppler guide wire) and epicardial luminal cross-sectional area ([CSA, mm2] 4.3F 30-MHz ultrasound catheter) data were obtained at baseline and during peak hyperemia after administration of 12 to 18 micrograms IC adenosine and 150 to 200 micrograms IC nitroglycerin. Volumetric CBF (mL/min) was calculated as CBF = APV (cm/s) x CSA (mm2) x 60 seconds/1 min x 1 cm2/100 mm2 x 0.5. Measurements were made from a discrete position in the proximal left anterior descending (LAD) artery (n = 22), mid-LAD artery (n = 7), proximal circumflex artery (n = 6), and proximal right coronary artery (n = 1). Intimal thickening was present in 19 of 32 patients (60%). Both adenosine and nitroglycerin increased APV (from 18.9 +/- 4.9 to 56.0 +/- 11.5 cm/s for adenosine and from 20.2 +/- 5.3 to 49.1 +/- 11.5 cm/s for nitroglycerin; both P < .05). Coronary flow velocity reserve was significantly higher for adenosine compared with nitroglycerin (3.1 +/- 0.6 versus 2.5 +/- 0.7, respectively; P < .001). Epicardial luminal CSA was unchanged during adenosine hyperemia compared with baseline (17.4 +/- 3.8 versus 17.3 +/- 4.0 mm2, respectively; P = NS) but was significantly greater during nitroglycerin hyperemia compared with baseline (18.7 +/- 3.8 versus 17.3 +/- 4.0 mm2, 6.2 +/- 3.6% change; P < .05). Baseline CBF was similar before drug administration. Hyperemic adenosine and nitroglycerin CBF responses (297 +/- 99 and 276 +/- 87 mL/min, respectively; P = NS) and CBF reserve (3.0 +/- 0.7 and 2.7 +/- 0.7, respectively; P = NS) were not significantly different. Importantly, intimal thickening did not diminish resting or hyperemic APV, coronary flow velocity reserve, luminal CSA, CBF, or CBF reserve responses. CONCLUSIONS: In this study of angiographically normal heart transplant recipients, epicardial intimal thickening does not diminish conduit and resistance vessel responses during endothelial-independent vasodilator administration.

Adenosine↗
PubMed1995

Radiofrequency catheter ablation of multiple morphologies of ventricular tachycardia by targeting a single region of the left ventricle.

INTRODUCTION: As treatment options for ventricular tachycardia (VT) continue to evolve, the use of radiofrequency catheter ablation is rapidly expanding. However, in the presence of multiple morphologies of VT, achieving successful results may seem less likely. We report two patients with multiple morphologies of VT who underwent successful radiofrequency ablation by application of radiofrequency energy to a single region in the left ventricle. METHODS AND RESULTS: Two patients, each without any apparent cardiac dysfunction and a history of documented VT, were referred to our institution for further management. They underwent an electrophysiologic study and were found to have easily inducible VT, of three morphologies in one patient and two in the other. Using a transaortic approach, left ventricular mapping was performed for detecting a site with presystolic potentials, earliest ventricular activation, or both. Application of radiofrequency energy to a single area in the left ventricle resulted in the elimination of all previously inducible VT in each patient. CONCLUSION: VTs with distinctly different morphologies can occur in patients with no detectable structural heart disease. These VT circuits may share a common pathway and, therefore, may readily be amenable to therapy with radiofrequency catheter ablation.

Adult↗
PubMed1992

Endothelin in thoracic inferior vena caval constriction model of heart failure.

Recent studies have found endothelin-1 (ET), a potent vasoconstrictor of endothelial cell origin, is increased in congestive heart failure (CHF) in plasma and correlates with increased atrial pressures. Additionally, it has been shown that, despite increased circulating ET concentrations in CHF, a decreased responsiveness to exogenous ET infusion exists in an experimental model of CHF induced by rapid pacing. The present study was designed to determine whether plasma ET would be increased in a model of low cardiac output congestive failure without elevated atrial pressures produced by thoracic inferior vena caval constriction (TIVCC). In addition, we sought to determine whether this model of low cardiac output would show a full vasoconstrictive response to exogenous ET infusion and whether atrial natriuretic factor (ANF) infused acutely to achieve pathophysiological concentrations would modulate the systemic and renal hemodynamic responses to exogenous ET. Dogs were studied in the anesthetized state at 8-9 days after the TIVCC or sham operation. Baseline ET levels were significantly increased in the TIVCC dogs (n = 14) compared with sham operated dogs (n = 6; 41.4 +/- 7.1 vs. 17.9 +/- 1.5 pg/ml, respectively; P less than 0.05). With exogenous ET infusion (5 ng.kg-1.min-1), an intact systemic and renal vasoconstrictor response in the TIVCC dogs was observed. ANF prevented the systemic vascular and arterial pressure responses to ET. However, the potent renal vasoconstricting action of ET was not prevented by ANF. These studies suggest that ET may play an important role in maintaining blood pressure in the setting of low cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The chaplain/pastoral counselor as a behavioral medicine consultant in cardiac rehabilitation: a team approach.

Pastoral Behavioral Medicine Consultants can make a valuable contribution to the modern hospital particularly if physicians and other health care professionals are joined in offering creative and effective programs for healing. This article discusses several programs in which the traditional hospital chaplain's role is extended to that of a pastoral/behavioral medicine consultant (PBMC). The examples are meant to stimulate the reader's interest, ideas and intuition about innovative ways that the modern PBMC can not only survive but flourish in chaplain/pastoral counseling ministries.

Behavioral Medicine↗
PubMed1989

Cytomorphometry of large cell carcinoma of the lung.

A computerized morphometry system was used to evaluate criteria for the cytologic diagnosis of large cell carcinoma (LCC) and poorly differentiated adenocarcinoma of the lung. There were 143 cells measured in six cases of LCC (five sputums and one bronchial washing) and 61 cells in four cases of adenocarcinoma (all sputum samples). Cellular and nuclear areas were significantly larger in adenocarcinoma whereas nucleolar area was greater in LCC, producing a higher nucleolar/nuclear area ratio in LCC. Cellular and nuclear form factors were smaller in LCC while the minor axis was longer in adenocarcinoma, resulting in a smaller axial ratio in adenocarcinoma. These data indicate that adenocarcinoma cells are larger and have a more rounded shape and less nucleolar material, as compared to the smaller, more ellipsoid and convoluted cells of LCC, which have more nucleolar area. A logistic regression identified cellular area, nucleolar/nuclear area ratio and cellular and nuclear form factors as significant contributors to the discrimination of LCC from adenocarcinoma, with a positive predictive value of 92%. Morphometry may therefore be helpful in the differential cytologic diagnosis of adenocarcinoma and LCC.

Adenocarcinoma↗
PubMed1987

Malignant pleural effusions. A clinical cytopathologic study.

From 1978 to 1982, 620 pleural fluid cytology specimens were examined, of which 80 were positive in 64 patients. Of these 64, three (0.5%) specimens had false-positive results. Adenocarcinoma of the lung was the most frequent (25 of 61) primary site, followed by breast (12 of 61), ovary (six of 61), and pancreas (five of 61). Comparing cytology with pleural core needle biopsy specimens in 26 patients, the cytology results were positive in 96%, while the needle biopsy specimens alone were positive in only 69%. Following the diagnoses of malignant pleural effusions, the patients receiving combined chemotherapy and radiotherapy had a mean survival of 328 days, compared with only 79 days for those who received no therapy. In conclusion, cytologic examination of Papanicolaou-stained smears yielded a greater percentage of positive diagnoses than either cell block preparations or pleural needle biopsy specimens. Over the past 25 years, the mean survival after the diagnosis of malignant pleural effusions has shown no improvement.

Adult↗
PubMedDate not supplied

Conventional respiratory cytology versus fine needle aspiration cytology in the diagnosis of lung cancer.

The results of 184 fine needle aspiration (FNA) cytologic examinations were compared with the findings of "conventional" respiratory cytology (on sputums, bronchial brushings and bronchial washings) and histology (on biopsy and autopsy samples) and with the medical records. Positive cytologic results were obtained in 6 (10%) of 60 sputums, 17 (21%) of 80 brushings, 16 (19%) of 84 washings and 82 (44%) of 184 aspirates. These positive results were confirmed by biopsy for 6 of 6 sputums, 16 of 17 brushings and 15 of 16 washings. Among the 82 patients with a positive FNA cytology, malignancy was confirmed by lung biopsy in 39 and by autopsy in 2; the cytologic diagnosis was supported by clinical and radiographic findings in all but 1 of the remaining 41 patients. Using transbronchial lung biopsy, autopsy and medical records as final standards, the positive predictive values were 100% for sputum, 94.1% for brushings, 93.0% for washings and 98.6% for FNA samples. The high positive predictive values of FNA and the other cytologic procedures indicate that these diagnostic modalities provide simple, rapid and reliable methods for the diagnosis of lung cancer.

Autopsy↗
PubMedDate not supplied

Diagnosis and typing of lung carcinomas by cytopathologic methods. A review of 108 cases.

A correlative review was made of the type of cytology specimens (sputum, bronchial washing and bronchial brushing) together with the corresponding histopathologic specimens of 108 patients. One hundred patients had primary pulmonary carcinomas diagnosed histopathologically (84) or clinically (16); 5 had carcinomas metastatic to the lungs and 3 had apparently false-positive cytologic results for lung cancer. The correlative review was used to determine the diagnostic reliability of pulmonary cytopathologic techniques in the detection and classification of lung carcinomas (i.e., the sensitivity and accuracy). The overall sensitivities of sputum, bronchial washing and bronchial brushing cytology were 60%, 66% and 77%, respectively (p less than 0.05). Bronchial brushing had a higher sensitivity (80%) for peripheral and metastatic lesions than did sputum (37%) or bronchial washing (60%). The overall accuracies of sputum, bronchial washing and bronchial brushing cytology were 79%, 75% and 76%, respectively, which is not statistically different. Regardless of the sampling methods, cytologic typing of squamous-cell and small-cell carcinomas was highly accurate but was less satisfactory for the other types of lung carcinomas. In the 16 cases in which endoscopic biopsies were either not attempted or gave negative results, one or more pulmonary cytologic specimens showed malignant cells. It is concluded that: (1) pulmonary cytopathologic techniques have excellent sensitivity and accuracy in the diagnosis of lung carcinomas; (2) they may establish the diagnosis of pulmonary carcinomas when endoscopic biopsies give negative results; and (3) they are particularly helpful in cases in which endoscopic biopsies suffer from a low yield (peripheral lesions) or create a considerable danger to the patients (iatrogenic hemorrhage).

Bronchi↗
PubMedDate not supplied

Management strategies in patients at high risk of sudden cardiac death following myocardial infarction.

Over 50 percent of deaths in patients who survive an acute myocardial infarction (MI) are due to fatal ventricular tachyarrhythmias. Patients who survive an episode of sustained ventricular arrhythmia are at highest risk of recurrent cardiac arrest. Electrophysiological studies have been found to be useful in guiding therapy and reducing mortality in these patients. However, evaluation and treatment of nonsustained ventricular tachycardia following MI remains controversial. Asymptomatic patients at high risk after MI include those who have significant left ventricular dysfunction, positive late potentials on signal-averaged electrocardiogram (SAECG), high grade ventricular ectopy and abnormal heart rate variability. These tests, however, have a low positive predictive accuracy and are not helpful to guide therapy with antiarrhythmic drugs which are usually ineffective and can frequently harm these patients. Beta-adrenoreceptor blocking agents, however, have been shown to reduce mortality after an acute myocardial infarction.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Sputum cytology within and across laboratories. A reliability study.

A total of 11 cytotechnologists at sites in Texas (TX1, TX2), California (CA) and Arkansas (AR) were assessed for agreement of six-category diagnoses of sputum cytology slides prepared by the method of Saccomanno. For three observers at TX1 there was more agreement within observers (27-60%) than across observers (13-50%). Within-1 category intraobserver agreement underwent a twofold to threefold increase, to 77-93%; within-2 category agreement was 90-100%. Interobserver within-1 category agreement was 47-92%; within-2 category agreement was 83-100%. Agreement was significantly greater than chance (using kappa) in 69% of all intraobserver and interobserver pairings. Intralaboratory agreement was 40% for CA and 40-57% for TX2. Among pairings of the four sites, the range of interlaboratory agreement was 13-60% over several occasions. The overall range of agreement with the TX1 standard was 17-50% over observers/occasions. Within certain categories, outside agreement with the TX1 standard was 53-90% for normal, 39-80% for squamous metaplasia, 68-84% for mild atypia, 80-100% for moderate atypia and 93-100% for severe atypia or carcinoma. We conclude that agreement is acceptable for extreme atypia, but more training or refinement of the guidelines may be needed, if justified, to better differentiate the lowest categories. Good agreement appears to be as likely for observers with many years of overall experience as for those with high exposure to the Saccomanno method. For potential statistical analyses, the scale should probably be condensed into three to four categories to reduce extraneous variability.

Cytodiagnosis↗