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Biomedical subjects

Q Macmanus

Publications and source records attributed to Q Macmanus.

At least 19 recordsLinked to original sources
PubMed1994

Artificial circulatory support with textured interior surfaces. A counterintuitive approach to minimizing thromboembolism.

BACKGROUND: Although numerous left ventricular assist devices (LVADs) have been used clinically, frequent thromboembolic complications have been reported despite the smooth interior LVAD surfaces and systemic anticoagulant medication. In contrast, the Thermo Cardiosystems HeartMate 1000 IP LVAD has textured interior surfaces that are promptly covered by a densely adherent neointima. We hypothesize that elimination of a direct interface between prosthetic material and blood elements reduces the risk of peripheral embolization and minimizes the necessity for systemic anticoagulant medication. This report defines the thromboembolic risk of this type of LVAD and characterizes the nature and effectiveness of the various anticoagulation regimens that were tested during the initial clinical trial with this device. METHODS AND RESULTS: All values are reported as mean +/- SD. Fifty-four males and three females with an average age of 47 +/- 11 years were supported with the HeartMate 1000 IP LVAD for an average of 62 +/- 76 days at 11 clinical centers in the United States. Patients were prospectively evaluated for thromboembolic complications. Five different anticoagulation regimens were used during the first 4 postoperative weeks: no anticoagulants, low-molecular-weight dextran, heparin, dipyridamole plus aspirin, or miscellaneous agents. After the first 4 weeks, the patients were treated with aspirin plus dipyridamole or miscellaneous agents. Prothrombin time (PT), partial thromboplastin time (PTT), and fibrinogen values for the patients were measured at 0.1, 1, 2, 4, 8, 12, 16, 20, 24, 32, and 46 weeks during support. Two patients (3.5%) suffered thromboembolic cerebrovascular complications, an incidence of 0.2 episodes per patient-year of observation. One episode was due to fungal vegetation developing on the device and the other was due to embolization from a previously placed native mechanical aortic valve prosthesis. In the absence of infection, there were no device-related thromboembolic complications. Mean prothrombin time for all groups was 13.3 +/- 0.5 seconds with no significant intergroup differences. Mean partial thromboplastin time during the first 4 weeks for the heparin-treated group was 53.3 +/- 6.6 seconds, which was significantly longer than for all other groups, but fell to control values after heparin was discontinued at 4 weeks. Mean fibrinogen level for all groups was 370 +/- 48 mg/dL, with no intergroup differences. CONCLUSIONS: The HeartMate 1000 IP LVAD provides adequate circulatory support with a low risk of thromboembolism despite minimal systemic anticoagulation. The use of textured surfaces may be an important factor contributing to the low observed risk of thromboembolic complications.

Anticoagulants↗
PubMed1993

A reliable bridge to cardiac transplantation: the TCI left ventricular assist device.

The Thermo Cardiosystems (TCI) HeartMate, a pneumatically driven, implantable left ventricular assist device, was designed for long-term support of the failing heart. Between February 1990 and August 1992, the HeartMate was implanted in 11 heart transplant candidates because of profound deterioration of left ventricular function. Patients had a mean cardiac index of 1.6 L.min-1 x m-2 and a mean pulmonary capillary wedge pressure of 33 mm Hg despite maximal pharmacologic support with at least three inotropic medications. In addition, 5 patients were being supported with an intraaortic balloon pump. Nine patients were bridged successfully to cardiac transplantation. The mean cardiac index after implantation of the left ventricular assist device was 3.2 L.min-1 x m-2. Support ranged from 2 to 143 days (mean duration, 60 days). One patient died early of low output secondary to right heart failure, and a second died of air embolism, which occurred intraoperatively. All surviving patients became fully ambulatory. There were no thromboembolic complications during a total of 658 patient-days of support on a regimen of only 80 mg of aspirin daily. The 9 bridged patients are currently alive 4 to 34 months after transplantation. The TCI HeartMate provides safe and effective hemodynamic support with low risk of complications and virtual freedom from thromboembolism on a regimen of minimal anticoagulation.

Adult↗
PubMed1992

Surgical complications in bridging to transplantation: the Thermo Cardiosystems LVAD.

Left ventricular assistance with a number of different devices has been used to successfully bridge patients to cardiac transplantation. Surgical complications or complications related to the device itself, however, may preclude transplantation or lead to death. We report our recent experience with the Thermo Cardiosystems model 14 "HeartMate" left ventricular assist device in 3 patients. The device was implanted for 15 to 95 days. Complications included mediastinitis and peritonitis associated with the device in place before transplantation, and colonic perforation, and a late diaphragmatic hernia after transplantation. Despite these and other minor complications, all 3 patients underwent successful cardiac transplantation. Mechanical support for the right ventricle was not necessary. The Thermo Cardiosystems left ventricular assist device provided excellent support in a range of physiological conditions with no mechanical malfunction despite the surgical complications.

Adult↗
PubMed1992

Multicenter clinical evaluation of the HeartMate 1000 IP left ventricular assist device.

The Thermo Cardiosystems Inc (Woburn, MA) HeartMate 1000 IP left ventricular assist device (LVAD) has been evaluated as a bridge to transplantation in 34 patients for up to 324 days at seven clinical centers in the United States. Sixty-five percent of the patients underwent transplantation, 80% of whom were discharged from the hospital. Six additional control patients, transplant candidates who met the entrance criteria but who did not receive the device, were also included in the study. Although 3 (50%) of the control patients received transplants, all 6 died within 77 days of having met the LVAD inclusion criteria (100% mortality). Complications resulting from use of the device were comparable with those previously reported for all ventricular assist devices, except for thromboembolic events: bleeding, 39%; infection, 25%; and right heart failure, 21%. No device-related thromboembolic events occurred, although 1 patient experienced an event related to a mechanical aortic valve in the native heart. None of the complications had a significant negative association with outcome of the patient except for right heart failure. All survivors had a significant improvement in hepatic function before transplantation. Total bilirubin values were reduced by 60% during LVAD support. No significant differences were observed when total bilirubin values were compared at 30 and 60 days after LVAD support and at 30 and 60 days after transplantation in a cohort of 15 patients (p greater than 0.05). The improvement in renal function was less predictable than that of hepatic function. Creatinine values decreased significantly before transplantation; however, the values measured at 30 and 60 days after transplantation were higher than those measured at the same intervals after LVAD support had been initiated, and this increase is presumably related to the immunosuppressive drugs. In conclusion, the HeartMate 1000 IP LVAD has been shown to be effective in supporting end-stage cardiomyopathy patients to transplantation. Thromboembolism, previously regarded as a serious complication with such devices, has not been a problem with this device. Additional patients are being enrolled into the study to further document the safety and effectiveness of this technology.

Adolescent↗
PubMed1991

Celiac artery aneurysms: case reports.

Two recent patients with celiac artery aneurysms focus attention on the relevant diagnosis and therapeutic alternatives that lead to a successful outcome in these patients. Awareness of the nonspecific symptoms associated with splanchnic arterial aneurysms combined with ultrasonography, computerized axial tomography, and arteriography lead to the appropriate diagnosis of a celiac artery aneurysm prior to rupture and exsanguinating hemorrhage. Aneurysm resection offers a definitive means of treatment. Selective use of revascularization techniques bolsters the surgical approach by preventing hepatic ischemia and serving as an additional source of visceral arterial blood flow. Our use of an autogenous or prosthetic graft from the intrarenal abdominal aorta proved to be a helpful adjunctive technique. Long-term vigilance is important because of the association of celiac artery aneurysms with other arterial occlusive and aneurysmal disease.

Adult↗
PubMed1990

Coronary artery bypass surgery: emerging trends in mortality.

In a consecutive series of 4,697 patients undergoing coronary artery bypass surgery, these risk factors were found to be significant for increased postoperative mortality: age greater than 70, female sex, unstable angina, prior myocardial infarction, hypertension, diabetes mellitus, and ejection fraction less than .40. A comparison by year (1980-1988) revealed a steadily increasing incidence of these risk factors. Future analysis of coronary artery bypass mortality should include risk-factor stratification.

Aged↗
PubMed1984

Thrombotic and embolic complications with silastic ball prosthetic valves.

Eighteen years of continuous clinical use with the Starr-Edwards ball-valve prosthesis provides an extensive data base for comparison with more recently introduced cardiac prostheses, and establishes the credentials of this valve for current clinical use. Since 1965, 558 aortic (model 1260) and 285 mitral (model 6120) ball-valve prostheses have been inserted at the University of Oregon. Thromboembolic rates for the entire series (1965-1983) and our more recent experience (1973-1983) were 3.8% per year and 2.8% per year for the aortic valve; and 5.1% per year and 2.6% per year for the mitral valve. Patients who had experienced one embolic episode were substantially more likely to experience a subsequent event. Thrombotic stenosis was seen at rates of 0.1% per patient year and 0.4% per patient year for the aortic and mitral valves, respectively. These results are compared with other current series using a variety of mechanical and tissue prostheses. The Starr-Edwards valve remains a durable mechanical cardiac prosthesis with thromboembolic complications similar to most other current prostheses. Thrombotic stenosis tends to be rare, gradual, and electively managed as opposed to the sudden, unpredictable, and catastrophic thrombosis seen with tilting disc valves.

Actuarial Analysis↗
PubMed1980

Early results with composite strut caged ball prostheses.

The Starr-Edwards model 6400/10 mitral and 2400/10 aortic valve prostheses incorporate metallic tracks on the inner aspects of cloth-covered struts in an attempt to preserve the favorable thromboembolic performance of cloth-covered valves while avoiding the risk of cloth wear. Two hundred severity operative survivors of mitral valve replacement with the model 6400/10 prosthesis, all on continuous anticoagulant therapy, have been followed up for a mean period of 2.3 (maximal 6) years. The late survival rate is 91 percent and the removal-free rate is 94 percent at 5 years. The rate of embolism (mean +/- standard error of the mean) is 4.6 +/- 0.9 percent per patient-year. Significant bleeding complications occurred at a rate of 1.0 +/- 0.2 percent per patient-year; there were no deaths. Two hundred forty operative survivors of aortic valve replacement with a model 2400/10 prosthesis, all on continuous anticoagulant therapy, have been followed up for a mean of 2.0 (maximal 7) years. The 5 year survival rate is 84 percent and the removal-free rate is 98 percent. Embolism occurred at a rate of 3.3 +/- 0.8 percnet per patient-year. Hemorrhagic complications occurred at a rate of 2.1 +/- 0.6 percent per patient-year; there were three families. Cloth wear and hemolysis have not been significant problems with this prosthesis, and the rates of thromboembolism are comparable with those reported for xenograft bioprostheses. The composite strut (track) valve prosthesis is a durable alternative to tissue valves in patients who are able to tolerate anticoagulant therapy.

Aortic Valve↗
PubMed1980

The use of time-interrelated covariates to predict survival following aortic valve replacement.

One hundred four patients survived isolated aortic valve replacement with the model 1200 prosthesis between 1965 and 1968, with a 12-year survival of 64%. Multiple regression survival analysis was employed in an attempt to determine which of 26 preoperative variables affected late survival and to devise a formula to predict survival for a given individual. The most important variables in the regression equation were right atrial mean pressure, etiology, and sex. The effect of the last two were found to vary with time over the 12-year post-operative period. An extension of the standard regression analysis technique was developed to incorporate time-related cofactors into the model. Based on the multiple regression model, 12-year survival was estimated to range from 92% to 14% for the best and worst combinations, respectively, of the three significant variables. The advantages of the regression method are outlined and the findings of other studies with regard to factors affecting survival after aortic valve replacement are summarized and discussed.

Adult↗
PubMed1980

Post-traumatic bronchial stenosis and acute respiratory insufficiency.

A 31-year-old woman sustained multiple injuries, including severe contusion of the right lung with massive subcutaneous emphysema. Four weeks later she was transferred to our institution with post-traumatic adult respiratory distress syndrome and carbon dioxide retention, resulting from a postlaceration stenosis of the left main-stem bronchus. Bronchoplasty was contraindicated because of the serious condition of the patient. Repeated bronchial dilatations produced initial improvement in oxygenation and minute ventilation requirements. However, because of the nature of the stenosis and the lack of recovery of right lung function, the patient's encouraging clinical course reached a plateau and attempts at weaning from the respirator were unsuccessful. Bronchoplasty was performed on postadmission day 50 and resulted in gradual recovery of pulmonary function. Six months following discharge, the patient continues a steady improvement. Management of the patient's injuries represented a unique challenge previously unencountered.

Adult↗
PubMed1980

Year of operation as a risk factor in the late results of valve replacement.

The actuarial thromboembolic rates of aortic and mitral silicone ball valves used during the second decade of cardiac valve replacement are significantly lower than the rates for the same prostheses implanted during the first decade, as shown in the following table: (Formula: see text). The embolus-free rates are significantly different (p < 0.01) in both the mitral and aortic series. Five-year embolus-free rates for the composite-strut caged-ball, Björk-Shiley tilting disc, and porcine xenograft valves all fall in the range of from 81% to 92% for the mitral position and from 91% to 97% for the aortic. Thus the standard silicone ball-valve prosthesis, used during the current era, has a thromboembolic risk as low as that reported with other concurrently utilized valve substitutes. This striking reduction in thrombogenicity demonstrates that the time frame of implantation must be considered when evaluating the results of cardiac valve replacement.

Adolescent↗
PubMed1978

Late results of triple valve replacement: a 14-year review.

Forty-eight patients have undergone simultaneous triple valve replacement at our institution over the past 14 years. This series was reviewed as a baseline for comparison with more recent tricuspid valve reparative procedures and to assess the natural history of advanced rheumatic heart disease with surgically corrected valvular lesions. Survival was 81% at one month and 32% at 14 years, not significantly different from results with double valve replacement during the same period, and not related to whether the tricuspid involvement was organic or functional. Forty-three percent of the late deaths were clearly valve related, a percentage which would undoubtedly be lowered with currently available prostheses. Functional class was determined in 13 of the 17 current survivors (mean follow-up, 10.3 years), and was improved over preoperative functional class in all but 3 patients. Three patients died of progressive congestive heart failure despite normally functioning prostheses; the reasons for these deaths are open to speculation.

Adult↗
PubMed1978

Technical considerations in patients undergoing combined aortic valve replacement and aortocoronary bypass surgery.

Forty-nine patients have undergone combined aortic valve replacement and aortocoronary saphenous vein bypass graft surgery using a technique of distal coronary perfusion. Vein grafts are placed before replacement of the aortic valve, and continuously perfused by siting the proximal anastomoses high on the aortic root or individually perfusing the grafts before proximal anastomosis. Continuous coronary ostial perfusion is used as well during aortic valve replacement. There were 3 (6.1%) operative deaths and 1 (2%) perioperative myocardial infarction. A comparison of this technique with other reported results suggests that attention to myocardial perfusion distal to significant coronary artery stenosis may decrease the incidence of perioperative myocardial infarction in patients requiring both aortic valve replacement and coronary bypass graft operation.

Adult↗
PubMed1978

Cardioplegic solutions for myocardial preservation: analysis of hypothermic arrest, potassium arrest, and procaine arrest.

Separate effects of perfusion hypothermia, potassium arrest, and procaine arrest were studied in 150 hearts using the isolated rat heart preparation. Aortic flow rate (AFR), coronary flow rate (CFR), and heart rate (HR) were measured before and after ischemic periods of 90 to 300 min. Prior to the ischemic period, the aortic root was infused with Krebs-Henseleit buffer (KHB), buffer with 30 mEq KCl/L (KHB + K), or buffer with 0.2% procaine (KHB + P), at 15 degrees or 5 degrees C. During the ischemic period the hearts were maintained at 15 degrees or 5 degrees C in a hypothermic chamber. The three solutions had similar recoveries of AFR at 15 degrees and 5 degrees C following ischemic periods of 90, 180, and 240 min. The KHB + K and KHB + P had better recoveries of AFR than KHB at 5 degrees C and 300 min of ischemia. The KHB + K and KHB + P also caused more rapid arrest and a higher incidence of spontaneous recovery of sinus rhythm. Arrest at 5 degrees C was equal to or superior to arrest at 15 degrees C. Perfusion hypothermia is the main component of cold cardioplegia. The addition of procaine or potassium results in increased functional recovery at extended ischemic times at 5 degrees C, more rapid arrest, and better electrical recovery.

Animals↗
PubMed1978

Aortic valve replacement and aorta-coronary bypass surgery. Results with perfusion of proximal and distal coronary arteries.

The results in 80 patients undergoing simultaneous aortic valve replacement and aorta-coronary saphenous vein bypass grafting were analyzed to assess the effect of operative technique. The over-all operative mortality rate of 6.3% (five of 80) did not differ significantly from our results with aortic valve replacement alone. All patients who had isolated aortic valve replacement were operated upon with moderate hypothermia. The combined operation was performed in two ways. Thirty-one patients had aortic valve replacement prior to bypass grafting with intermittent coronary ostila perfusion. There were two deaths (6.5%), and five myocardial infarctions (16.1%) were diagnosed by standard electrocardiographic and enzyme criteria. More recently, 49 patients have undergone bypass grafting prior to aortic valve replacement. The proximal ends of the grafts were either anastomosed high on the aortic root or else individually cannulated to provide continuous distal perfusion during subsequent aortic valve replacement, with continuous coronary ostial perfusion. There were three operative deaths (6.1%) and one myocardial infarction (2.0%). The risk of combined aortic valve replacement and coronary bypass need be no greater than the risk of aortic valve replacement alone. Our experience suggests that myocardial perfusion distal to significant coronary artery stenoses reduces the risk of myocardial infarction in patients with coronary artery disease requiring aortic valve replacement.

Adult↗