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Biomedical subjects

J C Baldwin

Publications and source records attributed to J C Baldwin.

At least 19 recordsLinked to original sources
PubMed2003

Noninvasive characterization of myocardium after transmyocardial laser revascularization.

AIM: The therapeutic mechanism of transmyocardial revascularization (TMR) is not yet fully understood, and continues to be a subject of controversy and active research. Immediate direct laser channel flow, gradual angiogenesis, denervation, and perioperative infarction of the ischemic area have been all discussed, without clear evidence indicating superiority of individual factors. METHODS: We utilized a prospective noninvasive physiologic dynamic method to assess laser-related myocardial injury. The study protocol included EKGs and echocardiograms, including intraoperative transesophageal echocardiograms (TEE) on consecutive TMR patients. CPK-MB was measured postoperatively, with 5 samples at 6-hour intervals. RESULTS: Fifty male patients averaging 62 years old were enrolled in the study. Two patients experienced postoperative myocardial infarctions, from which 1 died. The average CPK-MB values were 12.8+/-1.28 immediately after surgery, 19.2+/-2.4 at 6 h, 15.2+/-2.3 at 12 h, 12.2+/-6.3 at 18 h, and 11.7+/-1.3 at 24 h. In only 5 patients were the CPK-MB values over 30 units at their peak. The intraoperative wall motion remained unchanged in the patients studied, both using TEE and transthoracic echography. CONCLUSION: Significant myocardial injury after TMR appears unlikely, as indicated by CPK-MB and myocardial wall dynamics. Furthermore, TMR does not seem to aggravate baseline myocardial ischemia. We found no evidence to support a hypothesis that surgical myocardial injury constitutes the mechanism of therapeutic action in TMR.

Adult↗
PubMed2001

Physiologic characteristics of canine skeletal muscle: implications for timing skeletal muscle cardiac assist devices.

BACKGROUND: Optimal clinical stimulation for skeletal muscle cardiac assist systems (such as dynamic cardiomyoplasty) is not clearly defined. The pressure-generating capacity of canine skeletal muscle ventricles (SMVs) at a variety of preloads and stimulation frequencies was examined as was time for SMVs to develop peak pressure. METHODS: SMVs were analyzed just after construction and after 3 months of electrical conditioning. Pressure generation and time to develop peak pressure were determined using a distensible mandrel. RESULTS: Higher preloads resulted in increased pressure generation; conditioned SMVs generated significantly less pressure than unconditioned SMVs. Increasing stimulation frequency from 20 to 50 Hz increased pressure-generating capacity; increases beyond 50 Hz did not result in further increases. Time to 90% peak pressure was least at 10 HZ and 65 Hz. CONCLUSIONS: Higher stimulation frequencies and preloads result in a more quickly contracting muscle, which generates more pressure. Midrange stimulation frequencies of 30 Hz provide optimal muscle strength and minimize time to develop peak pressure. Initiation of contraction should begin before the time maximal pressure is desired.

Animals↗
PubMed2001

Aortic valve replacement: current clinical practice and opportunities for quality improvement.

This is a review of the current clinical practice and opportunities for quality improvement in aortic valve replacement surgery. The topics include trends and regional variation in procedure rates, and changes in the use of aortic valve replacement among the elderly. Recent developments guiding the choice of prosthetic valves and trends in in-hospital mortality rates for aortic valve surgery are summarized. Lastly, a discussion of topics relevant to clinical practice improvement including the implementation of clinical practice guidelines, the need for consensus on risk adjustment, better understanding of volume-outcome effects, and the opportunities for comprehensive assessment of aortic valve surgery.

Aortic Valve↗
PubMed2001

LEPS2, a phosphorus starvation-induced novel acid phosphatase from tomato.

Phosphate (Pi) is one of the least available plant nutrients found in the soil. A significant amount of phosphate is bound in organic forms in the rhizosphere. Phosphatases produced by plants and microbes are presumed to convert organic phosphorus into available Pi, which is absorbed by plants. In this study we describe the isolation and characterization of a novel tomato (Lycopersicon esculentum) phosphate starvation-induced gene (LePS2) representing an acid phosphatase. LePS2 is a member of a small gene family in tomato. The cDNA is 942 bp long and contains an open reading frame encoding a 269-amino acid polypeptide. The amino acid sequence of LePS2 has a significant similarity with a phosphatase from chicken. Distinct regions of the peptide also share significant identity with the members of HAD and DDDD super families of phosphohydrolases. Many plant homologs of LePS2 are found in the databases. The LePS2 transcripts are induced rapidly in tomato plant and cell culture in the absence of Pi. However, the induction is repressible in the presence of Pi. Divided root studies indicate that internal Pi levels regulate the expression of LePS2. The enhanced expression of LePS2 is a specific response to Pi starvation, and it is not affected by starvation of other nutrients or abiotic stresses. The bacterially (Escherichia coli) expressed protein exhibits phosphatase activity against the synthetic substrate p-nitrophenyl phosphate. The pH optimum of the enzyme activity suggests that LePS2 is an acid phosphatase.

Acid Phosphatase↗
PubMed2001

Technique of transmyocardial revascularization: avoiding complications in high-risk patients.

BACKGROUND: Transmyocardial revascularization (TMR) is an emerging therapy for coronary artery disease, with 7 years of published clinical research and nearly three years of clinical application. Every report thus far has confirmed that TMR relieves severe angina pectoris. It is primarily an alternative therapy for angina which has been refractory to conventional medical and surgical treatment. Operative mortality of 3% to 10% has been reported. METHODS: Seventy-seven patients were treated with TMR using a Holmium: YAG laser. Admission criteria included severe angina despite high doses of at least two anti-angina medications and nitroglycerin, reversible ischemia by thallium scan, and unsuitability for CABG or angioplasty. Patients had end-stage ischemic heart disease and multiple previous conventional procedures. TMR was performed through small left anterior thoracotomies using a 10.16 cm or less incision. RESULTS: Seventy-five patients recovered from surgery without major complications. One patient (1.3%) died of an autopsy-proven myocardial infarction in the treated region, and two additional patients had a myocardial infarction (4.3%). Four patients had paresis of the left phrenic nerve, as determined by an elevated left hemi-diaphragm on chest X-ray, from which three recovered fully. Patients had no bleeding or wound infections. Patients were intubated for an average of 1.5 hours and remained in ICU an average 0.8 days. Mean hospitalization was 3.4 days. CONCLUSIONS: Technically well-done TMR through a small anterior thoracotomy can have good therapeutic results and low morbidity and mortality. We will describe operative techniques which minimize pain and stress and help to insure surgical success.

Aged↗
PubMed2000

Chest radiograph heterogeneity predicts functional improvement with volume reduction surgery.

BACKGROUND: Using a historical cohort study model, we tested the hypothesis that heterogeneity of emphysematous changes on the preoperative chest radiograph correlated with favorable outcome of lung volume reduction surgery. METHODS: The test population consisted of 21 patients with severe emphysema who were being treated at a 1,000-bed university-affiliated tertiary teaching hospital. A simple but quantitative index of heterogeneity has been devised, whereby the preoperative posteroanterior chest radiographic lung fields are divided into four geometric quadrants. Each quadrant is scored (0 to 4) for emphysematous changes by two radiologists blinded as to subsequent patient management and outcome. Criteria for determining presence of emphysema were hyperlucency, decreased vascular markings, and parenchymal crowding indicating compressed lung. Heterogeneity index is the sum of the two highest scores minus the two lowest, with a maximum index of 8 and a minimum of 0. Preoperative chest radiographs and postoperative changes in forced expiratory volume in 1 second were examined. RESULTS: The heterogeneity index was positively correlated with change in forced expiratory volume in 1 second after operation with an r2 of 0.31 and an average increase of 117 mL per unit increase in heterogeneity index (p < 0.009). CONCLUSIONS: This simple index of heterogeneity may be useful as a predictor of improved pulmonary function after lung volume reduction surgery.

Aged↗
PubMed2000

Surgical management of primary aortoesophageal fistula secondary to thoracic aneurysm.

Aortoesophageal fistula, secondary to thoracic aortic aneurysm, is an uncommon cause of gastrointestinal bleeding that is uniformly fatal without surgical intervention. These may be primary fistulas, in cases of thoracic aortic aneurysm without previous repair, or secondary fistulas occurring after surgical repair of thoracic aortic aneurysm. Surgical treatment has been successful in a small number of cases of primary aortoesophageal fistula, secondary to thoracic aortic aneurysm, but techniques used have varied. We report a successful repair of primary aortoesophageal fistula, secondary to descending thoracic aortic aneurysm, and review the evolution of management since the three previously reported successful repairs at our institution.

Aorta, Thoracic↗
PubMed2000

Bilateral internal thoracic artery operations in the elderly.

BACKGROUND: Elderly surgical patients have higher operative morbidity and mortality than younger cohorts, particularly when the procedure is lengthy and complex. While use of bilateral internal thoracic arteries (BITA) is often associated with increased surgical risk, we nevertheless hypothesized that the use of BITA in elderly coronary artery bypass patients would not significantly increase their operative risk beyond that encountered using single internal thoracic arterial (SITA) or saphenous vein grafts (SVG). We maintained that arterial grafts remain essentially unaffected by arteriosclerosis, and that extension of a high-quality life is a desirable outcome regardless of age at operation. METHODS EXPERIMENTAL DESIGN: We studied myocardial revascularization in 673 patients over 65 years of age at the time of operation. All operations were conducted or supervised by a single surgeon during a ten-year period from January 1986 to January 1996. Preoperative and operative dates were recorded prospectively. SETTING: All patients underwent coronary artery bypass grafting. INTERVENTIONS: The study compared outcomes in patients having all veins, SITA or BITA operations. For the first analysis, 673 patients were divided into three groups: 163 patients (Group 1) had saphenous vein used for all bypasses; 338 patients had a SITA with supplemental vein grafts (Group 2); and 172 patients (Group 3) had BITAs with additional vein grafts as needed. In the second analysis, Group 3 was subdivided and grouped by the coronary arteries which received the ITA grafts, and the analysis was repeated. One hundred and sixteen patients (Group 3A) underwent traditional placement of ITA bypasses (left ITA to the LAD, right ITA to the RCA); in Group 3B, 56 patients received revascularization of branches of the left coronary artery (left ITA to the circumflex system, right ITA to the LAD). MEASURES: We communicated directly with 90.5% of the patients, their families, or their physicians. The survival status of the remainder was determined through the National Social Security Death Index Network. This allowed us to obtain follow-up longevity data for 100% of the study sample at a mean observation period of 5.03+/-3.1 years with variation between 10.8 years to 2.4 years. RESULTS: A multivariate analysis showed that placement of both ITA grafts to left-sided arteries in older patients independently improved long-term survival (p=0.031). CONCLUSIONS: The BITA procedure does not have greater operative morbidity or mortality in the elderly despite the length or complexity of the surgery. To realize improved long-term survival rates, however, both ITAs must be grafted to the left coronary artery branches.

Aged↗
PubMed1999

Cardiac autotransplant for surgical treatment of a malignant neoplasm.

Because of their anatomic location, cardiac sarcomas often interfere with cardiac function. Excision is considered to palliate the cardiac defect, but complete excision is often difficult owing to access, particularly in left atrial tumors. Incomplete resection results in tumor recurrence. To achieve complete resection of a large left atrial sarcoma, we used the technique of cardiac explantation, extracorporeal resection of the tumor with cardiac reconstruction, and cardiac autotransplantation.

Adult↗
PubMed1999

Holmium:YAG laser transmyocardial revascularization relieves angina and improves functional status.

BACKGROUND: Transmyocardial revascularization (TMR) surgery uses laser channeling of diseased myocardium to treat ischemia and angina. Rigorous prospective randomized studies have been previously unavailable. METHODS: Forty-three patients were randomized to a medication group and 43 to a group scheduled for TMR surgery and medication. All had advanced cardiac ischemia with CCSA class 3 or 4 angina, took at least 2 cardiac medications at maximum doses, and were ineligible for angioplasty or bypass. RESULTS: Forty-two of 43 TMR group patients received surgery and were discharged after hospitalizations averaging 3.2 days. Two suffered perioperative MIs, with one death. Four others died within 12 months of surgery, 3 from cardiac events and 1 from pneumonia. Five medical group patients died from cardiac events within 12 months. Three, 6, and 12 month exams showed angina class improvement in TMR patients compared to preoperative values (3.86 +/- 0.05 vs 1.71 +/- 0.2, P < 0.0001), and to controls at 12 months (3.77 +/- 0.07 vs 1.71 +/- 0.2, P < 0.0001). Exercise tolerance improved in TMR patients over preoperative values, and was better than medication group scores after 12 months (490 +/- 17 sec. vs 294 +/- 12 sec., p = 0.0002). CONCLUSIONS: Holmium:YAG laser channeling of the myocardium improves function and reduces angina in advanced cardiac patients who lack alternative therapeutic options.

Angina Pectoris↗
PubMed1999

Pharmacokinetics of liposomal aerosolized cyclosporine A for pulmonary immunosuppression.

BACKGROUND: The results of pulmonary transplantation are compromised by acute and chronic rejection. We hypothesized that a liposomal form of aerosolized cyclosporine A (CsA) would be selectively deposited and concentrated in the lungs. The theoretical advantage of this therapy is selective pulmonary immunosuppression with prolonged utilization. METHODS: Eighteen dogs were endotracheally intubated; aerosolized liposomal CsA was administered for 15 min. CsA levels were measured in whole blood, lung, trachea, heart, kidney, liver, and spleen at various times after treatment. RESULTS: The lung rapidly absorbs aerosolized liposomal CsA; other organs have much lower concentrations. The retention of pulmonary CsA delivered by liposome aerosol is approximately 120 min in this model. CONCLUSIONS: Aerosolized liposomal CsA is selectively deposited and concentrated in the lungs; other organs absorb less CsA.

Aerosols↗
PubMed1999

Long-term in vivo left ventricular assist device study for 284 days with Gyro PI pump.

A totally implantable centrifugal artificial heart has been developed. The plastic prototype, the Gyro PI 601, passed 2 day hemodynamic tests as a functional total artificial heart (TAH), 2 week screening tests for anti-thrombogenecity, and a 1 month system feasibility study. Based upon these results, a metallic prototype, the Gyro PI 700 series, was subjected to long-term in vivo left ventricular assist device (LVAD) studies of over 1 month. The Gyro PI 700 series has the same inner dimension and same characteristics of the Gyro PI 601 such as an eccentric inlet port, a double pivot bearing system, and a magnet coupling system. The PI metallic pump is also driven with the Vienna DC brushless motor actuator like the PI 601. The pump-actuator package was implanted in 3 calves in the preperitoneal space, bypassing from the left ventricular (LV) apex to the descending aorta. Case 1 achieved a 284 day survival. Case 2 was euthanized early at 72 postoperative days as a result of the functional obstruction of the inlet port due to the excessive growth of the calf. There was no blood clot inside the pumps of either case. Case 3 is on-going (22 days on July 24, 1998). During these periods, all cases showed no physiological abnormalities. In conclusion, the PI 700 series pump has excellent results as a long-term implantable LVAD.

Animals↗
PubMed1999

Actual versus actuarial analysis for cardiac valve complications: the problem of competing risks.

Methods for analyzing rates of events such as heart valve failure following surgery are important for comparing different techniques and devices; however, in patients undergoing major surgery, other risks such as mortality compete with the risk of heart valve failure to determine each patient's final outcome. When multiple, mutually exclusive endpoints are possible, a situation known to statisticians as a competing risks problem arises. No single statistical technique that is currently available provides an entirely satisfactory solution to this problem. We argue that in order for valve failure incidences to be useful clinically, the overall patient outcome milieu from which these failures arise must be considered. In this article, we review recent work in the area of competing-risks analysis as it pertains to heart valve surgery outcome.

Actuarial Analysis↗
PubMed1999

Methods of acute postcardiotomy left ventricular assistance.

OBJECTIVE: Despite many technological advances in cardiovascular surgery, some patients still experience postcardiotomy left ventricular (LV) failure that is refractory to both inotropic support and intra-aortic balloon pump (IABP) placement. The primary author (MJR) recently changed from inflow cannulation at the right superior pulmonary vein/left atrial junction to inflow cannulation at the dome of the left atrium. The purpose of this study was to compare data collected during placement of a left ventricular assist device (LVAD) at the junction of the right superior pulmonary vein with positioning the device in the dome of the left atrium. Experimental design, setting, and participants: the medical records of all patients undergoing cardiac surgery by one author (MJR) between 1994 and 1997 were retrospectively reviewed, and 4 patients requiring LVAD placement for short term postcardiotomy support were identified. Each patient's chart was reviewed for duration of LVAD support, average LVAD blood flows, pulmonary capillary wedge pressures (PCWP), preoperative characteristics, postoperative complications, and final outcome for the patients. RESULTS: Accessing the left atrium through the dome resulted in excellent blood flow through the LVAD and allowed for good LV decompression. Hemostasis remained the most common complication regardless of the technique employed; however, the enhanced visibility provided by accessing the left atrium via the dome made repairs less technically difficult. Three patients (75%) were able to be weaned from the LVAD and were discharged from the hospital to home. Two of these patients were cannulated via the left atrial dome making removal of the LVAD easier, thus exposing the patients to less additional operative time. One patient could not be weaned from LVAD support secondary to development of right ventricular failure requiring RVAD insertion and subsequent development of multiple organ failure syndrome. CONCLUSIONS: Patients requiring LV assistance following cardiopulmonary bypass surgery traditionally have high levels of morbidity and mortality. In spite of the complications associated with the placement of an assist device, we remain encouraged by the excellent LV decompression and systemic flows we achieved following implantation of the LVAD through the dome of the left atrium. The superior ease of implantation and decannulation provided better operative care and postoperative management for our patients.

Acute Disease↗