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Biomedical subjects

G J Magovern

Publications and source records attributed to G J Magovern.

At least 19 recordsLinked to original sources
PubMed1995

Microemboli during coronary artery bypass grafting. Genesis and effect on outcome.

Cerebral dysfunction after coronary artery bypass operations represents some of the most serious and costly complications of cardiac surgery. We used transcranial Doppler ultrasonography to detect and quantify the number of microemboli in the right middle cerebral artery of patients undergoing elective first coronary bypass operations (n = 117) and second coronary bypass operations (n = 10). We hypothesized that total microemboli were related to clinical outcome. A 2 MHz transducer was positioned in front of the ear above the zygomatic arch and depth gated to 50 mm. Microemboli were recorded as perturbations of the blood flow velocity in the middle cerebral artery and aurally monitored. Each episode of microembolism was specified both by clock time and as a perfusion or surgical event. Forty-one patients (32%) completed neuropsychologic evaluation with a battery of tests for cognitive function. Anxiety states and traits were also assessed. The distribution of microembolism showed that there were three groups of patients: < 30 microemboli (n = 83); 30 to 59 (n = 24); and > 60 (n = 20). Seven of 10 patients with cerebral complications (stroke, coma, delirium, aberrant behavior) were in the > 60 microemboli group. Those with cerebral complications had 20.7 +/- 4.5 microemboli from perfusion and 57.4 +/- 15.6 from surgical events. The 13 patients in the > 60 microemboli group without central nervous system symptoms had 95.5 +/- 19.5 microemboli from perfusion and 36.0 +/- 6.9 from surgical events. Neuropsychologic scores were most often depressed for memory (73%), comprehension (49%), attention (46%), and constructional ability (44%). The greatest change was in total score in the > 60 microemboli group (-3.3 +/- 0.6) compared with -1.1 +/- 0.2 and -1.9 +/- 0.2 for the 30 to 59 and < 30 groups, respectively. The incidences of cardiac and pulmonary complications and mortality were different between those patients with < 60 microemboli versus those with > 60 microemboli. Cardiac and pulmonary complications and mortality percentages were 4.7%, 3.7%, and 0.9%, respectively, for the < 60 microemboli group and 20%, 20%, and 15%, respectively, for the > 60 microemboli group. We concluded that transcranial Doppler ultrasonography is a useful technique to quantify and detect the source of microemboli during coronary artery bypass operations and may be useful in assessing new operative strategies, the quality of the perfusion, and potentially as an indicator for pharmacologic therapy in the operating room in patients with high microemboli counts.

Cardiopulmonary Bypass↗
PubMed1995

Myocardial regeneration. Transplanting satellite cells into damaged myocardium.

Millions of Americans suffer from chronic heart failure. Despite treatments with heart transplantation, cardiomyoplasty, and artificial assist devices, an ideal therapy is yet to be found. Since 1988, we have studied the transplantation of myogenic stem cells from skeletal muscle into injured myocardium in the hope that these cells would multiply and differentiate, thereby improving the function of the failing heart. We have achieved 2 goals thus far: the 1st was improving the culture technique to obtain high yield and purity of the satellite cells; the 2nd was successfully implanting cultured satellite cells in dog hearts and later identifying them as new myocardium. We share our findings here to encourage more study in this promising area.

Animals↗
PubMed1992

Clinical cardiomyoplasty: preoperative factors associated with outcome.

Dynamic cardiomyoplasty has been used clinically to augment the ventricular function of a failing heart. Fifteen clinical dynamic cardiomyoplasties have been performed at Allegheny General Hospital since 1985. Left ventricular ejection fraction improved in long-term survivors from a preoperative value of 0.23 +/- 0.02 to 0.32 +/- 0.05 with postoperative cardiomyostimulation (p < 0.05). There was an average reduction of 2 +/- 0.3 New York Heart Association classes (3.6 +/- 0.2 before operation versus 1.6 +/- 0.4 after operation; p < 0.001). Postoperative mortality was 27% (4/15), and early mortality (within 6 months after operation) was 20% (3/15). Significant preoperative differences between survivors and nonsurvivors were found in right ventricular ejection fraction (0.53 +/- 0.03 versus 0.30 +/- 0.07; p < 0.05), pulmonary artery mean pressure (19 +/- 2 versus 34 +/- 6 mm Hg; p < 0.05), pulmonary artery diastolic pressure (12 +/- 1 versus 25 +/- 5 mm Hg; p < 0.05), and pulmonary vascular resistance (1.4 +/- 2 versus 2.5 +/- 0.7 Wood units; p < 0.05). Dynamic cardiomyoplasty can be done with low operative mortality in patients with isolated left ventricular failure, but mortality is high in those with biventricular failure or pulmonary hypertension. Improvement in functional class and ventricular function can be expected in long-term survivors. Application of these findings to patient selection will improve the risk/benefit ratio for dynamic cardiomyoplasty.

Back↗
PubMed1992

Right latissimus dorsi cardiomyoplasty for left ventricular failure.

Recent experimental studies have shown that cardiomyoplasty using the right latissimus dorsi provides excellent hemodynamic augmentation. Based on these experimental findings, this procedure was performed in a 40-year-old man with a dilated cardiomyopathy after a large myocardial infarction. The patient tolerated the procedure well and has had marked functional improvement. Examination 6 months after operation demonstrated decreases in right atrial pressure, pulmonary capillary wedge pressure, and left ventricular end-diastolic volume. In addition, increases were noted in cardiac output, stroke volume, left ventricular stroke-work, right ventricular ejection fraction, and left ventricular ejection fraction. Because of this promising clinical result, we have started a series of right latissimus dorsi cardiomyoplasties for left ventricular failure.

Adult↗
PubMed1992

Isolated biventricular working rat heart preparation.

The isolated perfused heart from small animals has been used extensively for hemodynamic and metabolic studies. The left working heart preparation proved superior to the Langendorff model for functional evaluations but has not allowed study of right heart function. A simple and inexpensive biventricular working heart preparation has been developed by modifying the left working rat heart model. Under general anesthesia the heart was removed surgically leaving sufficient vessels attached to it. Cannulation of the aorta, left atrium, right atrium, and pulmonary artery was completed in 10 minutes. A pressurized compliance chamber allowed rapid and reliable regulation of aortic impedance. For the 7 hearts that were subjected to 3-hour biventricular perfusion (their end points expressed as percent of their initial values), the aortic output (95% +/- 3%), pulmonary flow (88% +/- 9%), mean aortic pressure (109% +/- 5%), mean pulmonary pressure (100% +/- 2%), heart rate (106% +/- 8%), myocardial adenosine triphosphate level (85% +/- 8%), and creatine phosphate level (89% +/- 4%) were all maintained at physiologic levels. For the 11 hearts that were converted from left working heart preparation to biventricular working mode, significant improvement in stroke volume, aortic and cardiac output, and pressure development were observed. Experimental results indicate that the biventricular working model for isolated perfused rat hearts is superior to the left working preparation for studying the function of the total heart. Further study of the biventricular perfused working rat heart appears warranted.

Animals↗
PubMed1992

Prolonged open sternotomy and delayed sternal closure after cardiac operations.

Maintenance of an open sternotomy (OS) after a complicated cardiac operation is an adjunct in the treatment of the severely impaired heart. We hypothesized that predictors of the timing, morbidity, and prognosis of delayed sternal closure (DSC) could be determined by intensive case review. Prolonged OS was used in 107 of 6,030 adult open heart patients (1.8%) between 1987 and 1991. Indications for OS were hemodynamic instability (40), myocardial edema (18), intractable bleeding (23), relentless arrhythmias (9), and ventricular assist devices (17). Delayed sternal closure was carried out in 75 of 107 patients at a mean of 3.4 +/- 0.3 days after OS. Fifty of these 75 (67%) survived and were discharged an average of 43 +/- 6 days after closure. Fifty-seven patients died: 32 before DSC at 3.7 +/- 0.8 days after OS and 25 after DSC at 27 +/- 4 days after OS. Baseline cardiac index (1.7 +/- 0.1 L.min-1.m-2) improved an average of 1.0 +/- 0.1 L.min-1.m-2 after OS (p less than or equal to 0.001) and remained stable through DSC (2.5 +/- 0.3 L.min-1.m-2) and late (9 +/- 0.7 days) follow-up (2.8 +/- 0.1 L.min-1.m-2). Delayed sternal closure in patients without ventricular assist devices was significantly more likely to be successful (45/63 versus 9/27; p less than 0.002) when carried out after the onset of a negative daily fluid balance. Sternal infection occurred in 4 of 75 (5%) patients after DSC and was associated with bleeding as an indication for OS (3/15 versus 1/60; p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Bilateral latissimus dorsi cardiomyoplasty.

This study was undertaken to test the hypothesis that a bilateral latissimus dorsi cardiomyoplasty provides greater hemodynamic augmentation than a unilateral procedure. Two types of bilateral procedure and a left posterior cardiomyoplasty were tested in each of 8 mongrel dogs. R-wave synchronous muscle pacing was achieved with a programmable burst stimulator. Hemodynamic variables of stimulated beats were compared with those of a nonstimulated baseline using paired t tests. The effects of a double anterior muscle wrap were equal to a right anterior/left posterior configuration. Therefore, the data on the two types of bilateral procedure were combined and compared with the left wrap. Stimulation of the bilateral cardiomyoplasty resulted in significant increases in right ventricular pressure (44 +/- 3.1 versus 26 +/- 1.8), first derivative of right ventricular pressure (595 +/- 117 versus 196 +/- 14), pulmonary artery pressure (34 +/- 1.9 versus 23 +/- 1.6), left ventricular pressure (90 +/- 5.9 versus 69 +/- 5.3), first derivative of left ventricular pressure (1454 +/- 141 versus 1072 +/- 107), aortic pressure (80 +/- 5.4 versus 67 +/- 4.9), and peak aortic flow (9.4 +/- 1.1 versus 7.7 +/- 0.8) (p less than 0.05). Significant increases in all of these variables also occurred with stimulation of the left cardiomyoplasty, but the increases in right ventricular pressure, first derivative of right ventricular pressure, pulmonary artery pressure, and aortic pressure were larger for the bilateral than the left cardiomyoplasty. The bilateral and the left procedure can each augment systolic ventricular function. The bilateral procedure appears to have greater effects, especially on right ventricular function.

Animals↗
PubMed1991

Resuscitation of injured myocardium with adenosine and biventricular assist.

Recovery of energy metabolism and contractility in stunned myocardium requires several days, even when mechanical circulatory support is employed. This double-blind study was undertaken to determine if myocardial recovery could be accelerated by intracoronary infusion of adenosine during reperfusion. Ten mongrel dogs were subjected to 45 minutes of global normothermic ischemia while on biventricular support with centrifugal pumps. During initial reperfusion, 20 minutes later, and at hourly intervals for 4 hours, dogs received 100 mL/min of unaltered blood or blood enriched with adenosine (0.2 mmol/L) into the coronary arteries for 5 minutes. Circulatory support was discontinued after 4 hours or sooner if the first time derivative of left ventricular pressure exceeded 2,000 mm Hg/s. Animals that received adenosine were weaned sooner (72 +/- 27 versus 216 +/- 54 minutes) and had higher systolic pressure (110 +/- 21 versus 57 +/- 36 mm Hg), lower left ventricular end-diastolic pressure (23.8 +/- 4.8 versus 34.0 +/- 7.2 mm Hg), and higher first time derivative of left ventricular pressure (3,407 +/- 812 versus 1,510 +/- 1376 mm Hg/s) than controls at the completion of the experiment (p less than 0.05). Final myocardium adenosine triphosphate levels were higher in the adenosine group (20.0 +/- 3.6 versus 14.2 +/- 4.0 mumol/g protein; p less than 0.05). Determination of infusion and coronary sinus blood concentrations demonstrated a 90% uptake of adenosine. All adenosine animals survived, but 2 of 5 control animals died within 1 hour of weaning. Reperfusion with adenosine-enriched blood accelerated recovery of ischemic myocardium and should be considered for patients requiring mechanical circulatory support after a heart operation.

Adenosine↗
PubMed1991

Fatigue resistant muscle with preserved force and mass for cardiac assist.

Sheep under general anesthesia had their left and right latissimus dorsi muscles mobilized for paraneuroelectrode and pulse generator implantation. After a 10-day recovery period, the left-side muscles were stimulated with a gradually increasing duration and rate over 3 months. At 4 months after operation, the tendinous end of each latissimus dorsi muscle was freed from its humeral insertion and attached to a strain gauge force transducer. Both left and right latissimus dorsi muscles, from each animal, were stimulated to contract for 2 hours for the fatigue study before being isolated, trimmed, and weighed. Frozen tissue biopsies were used to determine creatine phosphate, adenosine triphosphate, lactate, and glycogen content and muscle myosine ATPase, and succinate dehydrogenase activities. The arterial diameter in the conditioned muscle was 30% larger than that of the control muscle and had a 40% higher blood flow at rest. A three- to fivefold increase in blood flow during the fatigue test was observed. The force decreased 47% for the conditioned muscle and 91% for the control muscle. The mass and cross-sectional area of conditioned and unconditioned muscles were similar. Electric conditioning increased fatigue resistant fiber content from 33% to 92%, as evidenced by myosine ATPase activity. During the early phase of the fatigue test, higher glucose uptake but significantly lower lactate production were found for the conditioned muscle. This study indicates that it is possible to produce fatigue resistant muscle with preserved force and mass. In addition to skeletal muscle fiber transformation, metabolic adaptations appear to be important factors for fatigue resistance of skeletal muscle.

Animals↗
PubMed1991

A standardized nomenclature for latissimus dorsi cardiomyoplasty.

As worldwide clinical and experimental data accumulate, a standardized nomenclature for latissimus dorsi cardiomyoplasty must be accepted and universally applied in order to increase the potential for meaningful and reproducible comparison of results. This article presents a uniform nomenclature for latissimus dorsi cardiomyoplasty that is precise, anatomic and complete.

Assisted Circulation↗
PubMed1990

Recent experience with major sternal wound complications.

During a recent 1-year period, 31 patients sustained a major sternal wound infection and sternal dehiscence developed in 6 patients. Multiple potential risk factors were tabulated in these patients and in a control group selected from 1,521 patients undergoing sternotomy during the same time period. The overall infection rate was 2.1%, and the mortality rate in the patients with sternal infection or dehiscence was 16.2%. Chronic obstructive pulmonary disease, prolonged intensive care unit stay, respiratory failure, connective tissue disease, and male sex were significantly higher in the group with sternal infection or dehiscence (p less than 0.05). Advanced age and low cardiac output episodes were more frequent in this group, but only approached statistical significance. Although several risk factors may have been interrelated, male sex and the presence of pulmonary disease were statistically independent predictors of sternal wound infection. Risk factors may be helpful in identifying high-risk patients for additional prophylactic measures.

Aged↗
PubMed1990

Diuresis in hemodynamically compromised patients: continuous furosemide infusion.

We have used continuous infusion of furosemide to achieve diuresis in patients who are stable but hemodynamically compromised after heart operations. With a loading dose of 20 mg and a continuous infusion of 4 to 10 mg of furosemide per hour, mean 24-hour urine output was 5.7 L (238 +/- 65 mL/h). Potassium replacement was 115 +/- 20 mmol [115 +/- 20 mEq/L]. Cardiac index, central venous pressure, and diastolic pulmonary artery pressure did not change significantly, even though hemodynamic support was decreased in each patient. Continuous furosemide infusion is a simple, effective, and reliable method to achieve diuresis in select patients.

Adult↗