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Biomedical subjects

P Venugopal

Publications and source records attributed to P Venugopal.

At least 91 records · Page 5Linked to original sources
PubMed1996

Interpretation of calcifications in screen/film, digitized, and wavelet-enhanced monitor-displayed mammograms: a receiver operating characteristic study.

RATIONALE AND OBJECTIVES: The acceptance of filmless digital mammography is currently limited by digitization and display drawbacks, as well as bias toward hard-copy interpretation. In the current study, we evaluated a wavelet-based image enhancement method for the filmless interpretation of breast calcifications. METHODS: A set of 100 mammograms (58 with calcification clusters) was digitized at 105 microns and 4,096 gray levels per pixel and was processed with nonlinear filters and wavelets. Standard receiver operating characteristic analysis was performed by four radiologists, who independently read the films, the unprocessed digital images, and unprocessed and wavelet-enhanced digital images presented simultaneously. RESULTS: Statistical differences were observed between screen/film and unprocessed digitized mammography displayed on monitors. Differences were not significant when wavelet enhancement was included in the monitor display. Interobserver variation in the digitized reading was greater than in film reading, but the wavelet enhancement reduced the difference. CONCLUSION: Wavelet-enhanced digital mammograms may assist radiologists in diagnosing calcifications directly from computer monitors and may compensate for current technologic limitations. A study with a larger data-base is needed before this method is accepted for clinical use.

Breast Diseases↗
PubMed1996

A paradigm shift in myelodysplastic syndromes.

A poorly defined transforming event(s) affects the pluripotential bone marrow (BM) stem cell in myelodysplastic syndromes (MDS), conferring a growth advantage upon it which leads eventually to monoclonal hematopoiesis. The progeny of this transformed ancestor undergo recognizable albeit dysplastic maturation. We propose that this picture is further complicated by a variety of cytokines, tumor necrosis factor alpha (TNF-alpha), transforming growth factor beta (TGF-beta) and interleukin 1beta (IL-1beta) which exert a dual effect on the diseased cells. The immature CD34+ cells are stimulated to proliferate, while their later differentiated daughters are induced to undergo apoptosis accounting for the clinical syndrome of pancytopenia despite hypercellular BMs. Studies directed at measuring the rates of proliferation and apoptosis as well as the levels of TNF-alpha, TGF-beta and IL-1beta confirm this hypothesis and are presented in greater detail. A novel approach towards MDS therapy emerges as a result of this paradigm shift based upon the premise that anti-cytokine therapy would prevent excessive intramedullary apoptosis and result in improved cytopenias as well as cause a slowing down of the diseased precursor cell proliferation resulting in resumption of polyclonal hematopoiesis. Because a number of cytokines function through common lipid second messengers, interruption of this pathway should theoretically cause disruption in the signalling of a cascade of cytokines.

Apoptosis↗
PubMed1995

Serial echocardiography for decision making in rapid two-stage arterial switch operation.

BACKGROUND: Rapid two-stage arterial switch operation is advocated in infants with simple transposition presenting late. Accurate assessment of left ventricular preparation is crucial to successful outcome. The role of echocardiography alone in surgical decision making remains unclear. METHODS: Seventeen patients with simple transposition (mean age, 4 months) underwent pulmonary artery banding and modified Blalock-Taussig shunt (first stage) to prepare the left ventricle for the arterial switch operation (second stage). Serial echocardiography was performed in the interval phase to assess left ventricular growth. Sixteen patients underwent arterial switch operation after a mean interval of 10.4 +/- 4 days, with 14 successful conversions. There was one mortality (5.9%) and two conversions to a Senning repair. RESULTS: In all patients a mean increase in left ventricular mass (40.8 +/- 17.8 g/m2 to 81.4 +/- 25.4 g/m2) and posterior wall thickness (3.37 +/- 0.47 mm to 4.63 +/- 0.58 mm) was recorded. Left ventricular end-diastolic internal diameter increased in all except the two switch failures. In all the successful cases the left ventricle had assumed a circular shape on cross-section with the interventricular septum contracting in synergy with the left ventricular mass. In the two failures, however, the interventricular septum had remained flat. CONCLUSIONS: Echocardiography can be used reliably in surgical decision making in rapid two-stage arterial switch operation. Increase in left ventricular mass, left ventricular posterior wall thickness, and left ventricular end-diastolic internal diameter toward normal combined with an acquisition of circular left ventricular configuration with the interventricular septum contracting in synergy with the left ventricular mass appear to best predict successful outcome.

Anastomosis, Surgical↗
PubMed1995

Univentricular repair. Early and midterm results.

A total of 202 patients (62 with tricuspid atresia and 140 without tricuspid atresia) underwent univentricular repair at our unit from January 1990 to September 1994. Of these patients, 182 had nonfenestrated and 20 had fenestrated interatrial baffles. Early mortality was 15.9% (29/182) in the group with nonfenestrated baffles and 5% (1/20) in the group with fenestrated baffles. The follow-up period ranged from 2 to 58 months. Seven late deaths occurred, and five patients were lost to follow-up. Of 160 patients who have been evaluated in the outpatient department in the past 3 months, 142 (88.75%) required no cardiac medicines and were in functional class I. Risk factors analyzed for early mortality and significant effusion were age, preoperative diagnosis, type of Fontan modification, cardiopulmonary bypass time, aortic crossclamp time, pulmonary artery size, associated pulmonary arterioplasty, takedown of systemic-pulmonary artery shunt, and pulmonary artery debanding, along with the Fontan operation. Bypass time exceeding 120 minutes was associated with a higher early mortality (12/47 vs 18/155; p = 0.0187). Bypass time exceeding 120 minutes (p = 0.0456) and aortic crossclamp time exceeding 60 minutes (p = 0.0278) were associated with significant postoperative effusion. Other factors were not associated with any significantly increased risk for early mortality or postoperative effusions. Fenestration of the interatrial baffle appeared to decrease early mortality, although the numbers are too small to be statistically significant. The prevalence of effusions did not differ significantly between the group with fenestrated baffles and the group without fenestrated baffles.

Cardiopulmonary Bypass↗
PubMed1995

Regrowth resistance in cancer: why has it been largely ignored?

In drug-sensitive malignancies, treatment failure is a complex phenomenon resulting from both drug resistance and the rapid regrowth of malignant cells in between cycles of chemotherapy. This phenomenon has been referred to as regrowth resistance, and has been identified as a common impediment to the successful treatment of many neoplastic diseases. This phenomenon has received little attention in the past. The administration of maximally tolerated individual dosages of chemotherapeutic agents, combined with the use of biological response modifiers to slow the regrowth between courses of therapy, would be an effective approach to reduce the regrowth resistance. This also could reduce the emergence of drug resistant clones.

Antineoplastic Agents↗
PubMed1995

Coronary angioplasty in high risk patients: comparison of elective intraaortic balloon pump and percutaneous cardiopulmonary bypass support--a randomized study.

Forty patients undergoing percutaneous transluminal coronary angioplasty (PTCA) with severely impaired left ventricular ejection fraction (LVEF) < 30% were randomized between prophylactic intraaortic balloon pump (IABP) support (N = 20) and percutaneous cardiopulmonary bypass (PCPB) support (N = 20). The indications for both groups were left ventricular (LV) dysfunction and a large area of myocardium (> 50%) being perfused by the target vessel. The IABP and PCPB supported groups were comparable in LVEF (20% +/- 6.4% vs 22.8% +/- 8.1%), mean pulmonary artery pressure (46.5 +/- 10.5 mmHg vs 42.6 +/- 12.6 mmHg), average number of vessels dilated (1.4 vs 1.3), mean inflation time (2.8 +/- 0.3 min vs 3.1 +/- 0.5 min), and hospital stay after PTCA (5.6 +/- 1.2 days vs 5.2 +/- 1.4 days). The primary success rate (95% vs 95%) and hospital mortality (5% vs 5%) were also similar in the two groups. Two patients required surgical exploration of the femoral artery and eight patients required blood transfusion in the PCPB group. IABP patients had no vascular complications and did not require blood transfusion. High risk PTCA is equally effective whether using prophylactic IABP or PCPB support. PCPB support, however, has a higher rate of vascular complications and need for blood transfusions. IABP has the additional advantage of ease of insertion and the support can be used for a longer period after PTCA, if required.

Adult↗
PubMed1995

Tree structured wavelet transform segmentation of microcalcifications in digital mammography.

A novel multistage algorithm is proposed for the automatic segmentation of microcalcification clusters (MCCs) in digital mammography. First, a previously reported tree structured nonlinear filter is proposed for suppressing image noise, while preserving image details, to potentially reduce the false positive (FP) detection rate for MCCs. Second, a tree structured wavelet transform (TSWT) is applied to the images for microcalcification segmentation. The TSWT employs quadrature mirror filters as basic subunits for both multiresolution decomposition and reconstruction processes, where selective reconstruction of subimages is used to segment MCCs. Third, automatic linear scaling is then used to display the image of the segmented MCCs on a computer monitor for interpretation. The proposed algorithms were applied to an image database of 100 single view mammograms at a resolution of 105 microns and 12 bits deep (4096 gray levels). The database contained 50 cases of biopsy proven malignant MCCs, 8 benign cases, and 42 normal cases. The measured sensitivity (true positive detection rate) was 94% with a low FP detection rate of 1.6 MCCs/image. The image details of the segmented MCCs were reasonably well preserved, for microcalcification of less than 500 microns, with good delineation of the extent of the microcalcification clusters for each case based on visual criteria.

Calcinosis↗
PubMed1995

Systemic-to-pulmonary artery collateral vessels and surgical shunts in patients with cyanotic congenital heart disease: perioperative treatment by transcatheter embolization.

OBJECTIVE: Systemic-to-pulmonary collateral vessels can develop in patients with obstruction of the right ventricular outflow tract or the pulmonary artery. Occlusion of these vessels is necessary before surgical correction of the primary disease. We report the results of transcatheter coil embolization in the treatment of 56 patients. MATERIALS AND METHODS: Seventy-four procedures were done in the perioperative period for treatment of 67 aortopulmonary collateral arteries, five modified Blalock-Taussig shunts, and two enlarged veins. RESULTS: In the "aortopulmonary collateral" group, occlusion was complete in 51 patients (76%), subtotal in seven (10%), partial in four (6%), and failed in five (8%). Inadvertent embolization to the aorta occurred in two procedures, but both coils were retrieved nonsurgically. During follow-up of 1-12 months (n = 32; mean, 6.3 months), the coils remained in position, without any migration. Follow-up angiograms in 14 embolized vessels showed no recanalization (mean, 5.3 months; range, 2-12 months). In the "shunt" group, occlusion was complete in four patients and failed in one. Distal embolization to the pulmonary artery occurred in one patient. This coil was retrieved during surgery. During follow-up of 3-6 months, coils remained in position in all patients. In one patient, a follow-up angiogram at 3 months showed no recanalization. In the "venous embolization" group, occlusion was complete in one patient. The coils were in position 5 months later. The procedure was unsuccessful in the other patient. CONCLUSION: We conclude that transcatheter coil embolization is useful in the treatment of abnormal systemic-to-pulmonary vessels and shunts in patients with obstruction of the right ventricular outflow tract or the pulmonary artery. Homemade coils are safe and effective in obliterating antegrade flow.

Adolescent↗
PubMed1995

Orthotopic pulmonary valve replacement with a homograft.

Eight pulmonary valve replacements (PVR) have been performed from January 1992 to October 1994. Three patients (mean age 7.7 years, range two to 16 years) had absent pulmonary valve with tetralogy of Fallot and underwent primary PVR at the time of surgical correction. Five other patients, who had correction of tetralogy of Fallot (four cases) and of double outlet right ventricle with ventricular septal defect and pulmonary stenosis (one case), were reoperated for pulmonary regurgitation with progressive right ventricular dysfunction. Mean age at the time of reoperation was 18 years (range seven to 34 years). There was no early death. Early postoperative recovery was satisfactory in all of them. The follow up ranges from six to 35 months (mean 19 months). Seven patients were in functional class I and one in functional class II when they were last evaluated in the out-patient department and five of them were off diuretics and vasodilator. In the presence of right ventricular dysfunction pulmonary regurgitation is poorly tolerated. A competent and non-obstructive pulmonary valve is often life saving in these critically ill patients.

Adolescent↗
PubMed1994

Life-threatening arterial haemorrhage: results of treatment by transcatheter embolization using home-made steel coils.

Major arterial haemorrhage can be fatal. Its management by percutaneous embolization using commercially available embolizing agents is well established. We describe the use of home-made steel coils in the treatment of five patients. These coils were designed during the procedure in order to conform to the dimension of the bleeding artery. The group included two patients with life-threatening haemoptysis after surgical correction for tetralogy of Fallot; one patient each with exsanguinating haemorrhage from a branch of the left profunda femoral artery following violent trauma; massive haematuria due to an inoperable hypernephroma; and haemoptysis due to post-tubercular bronchiectasis. The bleeding vessel was evaluated by selective angiography in each patient. After assessing its length and diameter, steel coils of desired dimensions were made by utilizing a conventional 0.032-in wide guidewire and these were released into the bleeding artery. Occlusion of the bleeding vessel was obtained in all patients, without complication. Fabrication of coils of desired length and diameter can be done within a few minutes during the procedure. These coils provide an effective method of treating life-threatening arterial haemorrhage in selected cases.

Adult↗
PubMed1994

Magnetic resonance imaging (MRI) in evaluation of left atrial masses: an in vitro and in vivo study.

Thirty patients, 15 each of suspected of left atrial myxoma and clot were studied in a prospective study to assess the role of magnetic resonance imaging (MRI) in evaluation of left atrial masses. Upon clinical and echocardiographic suspicion of a left atrial mass, patients were subjected to ECG-gated MRI (in vivo study) and subsequently all of them underwent surgery for the removal of mass and/or mitral valve replacement/repair. Within 6 hours of its removal the mass was subjected to in vitro MRI study and subsequently to histopathological examination. During the study T1, T2 gated images were obtained and tissue characterization was done. A magnetic dye Gd-DTPA was used for contrast enhancement. Cine-display of the images was obtained to demonstrate dynamic movement of the mass across the mitral valve. MRI was found to be highly useful in delineating the exact anatomical details of left atrial masses. Results of MRI diagnosis with illustrations are discussed.

Adolescent↗
PubMed1992

Carcinoma of the rectal pouch following restorative proctocolectomy. Report of a case.

A case of adenocarcinoma developing in the pouch following restorative proctocolectomy is presented. This seems to be the third reported in the literature. The carcinoma developed from the remnants of precancerous rectal mucosa left in the muscular rectal cuff. The patient had been suffering from ulcerative colitis for 17 years prior to the development of the malignancy. He presented with features of subacute intestinal obstruction. Diagnosis was by sigmoidoscopic examination of the pouch and biopsy. He was treated with abdominoperineal resection of the pouch and rectum, followed by chemotherapy.

Adenocarcinoma↗
PubMed1992

Thrombolytic therapy for prosthetic valve thrombosis: a study based on serial Doppler echocardiographic evaluation.

Sixteen patients with echocardiographic and cinefluoroscopic evidence of Björk-Shiley prosthetic valve obstruction (13 mitral valves and 3 aortic valves) were treated with intravenous streptokinase. Streptokinase was administered as an initial bolus of 250,000 units for 30 minutes, followed by an infusion of 100,000 units/hr. Serial cinefluoroscopy and echocardiography (M-mode, two-dimensional, and Doppler) were performed at 0, 24, 48, and 72 hours of treatment. The end point of treatment was defined as near normalization of clinical, echocardiographic, and fluoroscopic parameters. Successful thrombolysis was achieved in all patients. The average duration of streptokinase therapy was 43 hours (range 2 to 72 hours). Two of 16 patients had minor systemic embolism during therapy. Short-term follow-up has shown sustained benefit in 14 of 16 patients. Two patients have had rethrombosis of the mitral prosthetic valves and have undergone thrombectomy. Our study demonstrates the feasibility, safety, and efficacy of thrombolytic therapy in the treatment of prosthetic valve thrombosis. It also emphasizes the role of serial Doppler echocardiography in guiding the duration of therapy and assessing its efficacy.

Adult↗
PubMed1992

Prospective controlled study of post-transfusion hepatitis after cardiac surgery in a large referral hospital in India.

We studied the risk of post-transfusion hepatitis (PTH) in recipients of blood collected from voluntary donors screened for HBsAg. Two hundred and fifty patients without any previous history of liver disease or transfusion were followed up for 12 months subsequent to cardiac surgery. Thirty-five of them had closed-heart surgery without receiving transfusion and served as controls. The remaining 215 patients received single-point transfusions (mean 4 +/- 2.4 units). None of the controls and 15 (6.9%) blood recipients developed PTH. Three (20%) patients had hepatitis-B-virus-induced hepatitis while the remainder (80%) had non A, non B (NANB) hepatitis. The number of units of blood transfused and surrogate markers for development of PTH (donor alanine aminotransferase, anti-HBc and anti-HBs antibody) were not associated with the occurrence of PTH (p greater than 0.05). Nine (60%) of the 15 patients developing PTH were asymptomatic. All the patients recovered from the PTH, except one who died of fulminant hepatitis. At the end of 1 year of follow-up, none of the patients had evidence of chronic hepatitis. Only three (25%) of the patients with NANB-PTH developed anti-hepatitis C virus (HCV) antibody during the follow-up. We conclude that the incidence of PTH in India is similar to other parts of the world and NANB virus was the major cause of the PTH. The absence of chronicity and lack of seroconversion to anti-HCV antibody in the majority of the patients after 1 year of follow-up may suggest the possibility of a NANB virus other than HCV as the major cause of PTH in India.

Adolescent↗