Biomedical subjects

T J Gardner

Publications and source records attributed to T J Gardner.

At least 109 records · Page 6Linked to original sources

PubMed1986

Major stroke after coronary artery bypass surgery: changing magnitude of the problem.

Between January 1974 and December 1984, 3816 patients underwent isolated CABG at this hospital. During this 11-year interval, the number of patients having operation annually as well as the mean age at operation of the patients have increased significantly. The increase in the mean age from 51.9 years in 1974 to 59.4 years in 1984 occurred while the operative mortality rate fell significantly from 3.9% in 1974 to 2.0% in 1984. Although the overall incidence of major stroke was 1.8%, the stroke rate increased during this interval to 2.4% from 1982 to 1984. This higher stroke rate correlates significantly with the increasing age of the CABG patients, with the stroke risk five times greater for patients in their 70s compared with patients between 51 and 60 years old. Specific risk factors for the development of stroke during CABG in addition to age were examined and discussed.

Aged↗

PubMed1986

Anatomic and anesthetic considerations in experimental cardiopulmonary surgery in swine.

We have used immature commercial swine (13-25 kg) successfully in a variety of experimental cardiopulmonary surgical procedures in our laboratories since 1981. Multiple drug anesthetic protocols using barbiturates, narcotics, paralytic and antiarrhythmic agents have been employed in over 400 procedures per year. Complications, including fatal cardiac arrhythmias, have been greatly reduced by anesthetic protocols and surgical procedures developed through experience.

Acepromazine↗

PubMed1986

Five year follow-up after valve replacement with the St. Jude Medical valve in infants and children.

Since 1979, 34 infants and children, 3 weeks to 17 years of age, have undergone cardiac valve replacement with a St. Jude Medical (SJM) prosthesis at our institution. Seventeen children underwent mitral valve replacement (MVR), 16 aortic valve replacement (AVR), and one pulmonary valve replacement. Three hospital deaths were associated with MVR and complex congenital heart disease. All surviving patients were functional in class I. A cumulative 89.1 patient-years of follow-up were analyzed to evaluate valve-related mortality and morbidity. Late complications included thromboembolus (one patient), anticoagulant-related hemorrhage (one patient), and perivalvular leak (one patient). One of six late deaths resulted from mitral valve thrombosis. Actuarial 5 year survival for patients who underwent AVR was 100%, but it was 53% for MVR (p = .03). Freedom from significant morbidity and mortality for up to 5 years after operation was 92 +/- 7% for those who underwent AVR and 45 +/- 16% for those who underwent MVR. Patient-related factors appear to account for an increased rate of complications after MVR. Because of difficulties with achieving anticoagulation with warfarin, aspirin therapy should be used for patients less than 5 years of age, while older patients can be managed with warfarin. The SJM valve is a satisfactory cardiac valve substitute for the pediatric age group.

Adolescent↗

PubMed1985

Reperfusion before global ischemic arrest improves the salvage of infarcting myocardium.

To study the effect of hypothermic global ischemic arrest on an evolving myocardial infarction and of perfusion of the ischemic zone or region at risk before global ischemia, 62 farm pigs underwent 15, 30, or 60 minutes of reversible coronary occlusion. Twenty-eight of these animals served as controls: reflow to the region at risk was established by removal of the coronary occluder without the addition of global ischemia. Another 26 animals had similar periods of coronary occlusion and then were placed on cardiopulmonary bypass; they underwent aortic cross-clamping and cardioplegia-induced global hypothermic arrest for 45 minutes. Eight additional pigs had two hours of reflow to the region at risk after removal of the occluder and before global ischemic arrest. When superimposed on regional ischemia, global ischemia resulted in a 6-fold increase in infarct size after 15 minutes of coronary occlusion (p less than 0.05), a 2.2-fold increase after 30 minutes of coronary occlusion (p less than 0.05), and no significant increase after 60 minutes of coronary occlusion. Reperfusion prior to global ischemia completely prevented infarct extension with 0.4% less infarction (not significant) in this group versus the controls without global ischemia. These results clearly demonstrate that infarct extension occurring when global ischemia is superimposed on regional ischemia is greatest early in infarct evolution but that reflow to the region at risk before global ischemic arrest prevents the additional infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Stroke following coronary artery bypass grafting: a ten-year study.

To identify possible risk factors for the occurrence of stroke during coronary artery bypass grafting (CABG), the cases of 3,279 consecutive patients having isolated CABG from 1974 to 1983 were reviewed. During this period, the risk of death fell from 3.9% to 2.6%. The stroke rate, however, fell initially but then rose from 0.57% in 1979 to 2.4% in 1983. Adjustment of these data for age clearly demonstrated that the risk of stroke has increased largely because of an increase in the mean age of patients undergoing CABG procedures. A case-control study involving all 56 stroke victims and 112 control patients was used to identify those risk factors significantly associated with the development of stroke in univariate analysis: increased age (63 versus 57 years in stroke patients and controls, respectively; p less than 0.0001); preexisting cerebrovascular disease (20% versus 8%; p less than 0.03); severe atherosclerosis of the ascending aorta (14% versus 3%; p less than 0.005); protracted cardiopulmonary bypass time (122 minutes versus 105 minutes; p less than 0.005); and severe perioperative hypotension (23% versus 4%; p less than 0.0001). Other variables not found to correlate with postoperative stroke included previous myocardial infarction, hypertension, diabetes mellitus, lower extremity vascular disease, preoperative left ventricular function, and intraoperative perfusion techniques. Elderly patients who have preexisting cerebrovascular disease or severe atherosclerosis of the ascending aorta or who require extensive revascularization procedures have a significantly increased risk of postoperative stroke.

Age Factors↗

PubMed1985

Coronary artery bypass grafting in women. A ten-year perspective.

Between January 1974 and December 1983, 3279 patients have undergone isolated coronary artery bypass (CAB) grafting at the Johns Hopkins Hospital. There were 639 women in this group. Women represented 18 to 22% of the patients having isolated CAB grafting throughout the 10-year period, except in 1976 when only 13% of the CAB patients were women. Mean age-at-operation for women has increased from 53.9 to 61.1 years since 1974, and was higher than the mean operative age of men during each of the 10 years. Although the oldest woman undergoing CAB grafting in 1974 was 64 years old, the eldest in 1983 was 84 years old. Except for an older mean age-at-operation for women and a higher incidence of unstable angina prior to surgery, the only other significant difference in the clinical status of female versus male CAB patients, detected by a case control analysis, was the smaller body surface area of women compared to men. Although operative mortality was significantly greater for women during most of this review period, mortality was similar during 1983 (2.6% for men versus 2.4% for women), in spite of a significantly higher incidence of unstable angina in the female group (54% for women versus 35% for men). The improved survival noted following coronary bypass grafting in women, which occurred in spite of the advancing age of the female group, supports an aggressive approach to surgical intervention in women with severe coronary artery disease.

Age Factors↗

PubMed1985

The use of perfluorochemicals during open heart surgery.

Several experimental studies of global myocardial ischemia involving different animal models have demonstrated enhanced oxygen delivery and oxygen consumption when oxygenated perfluorochemical cardioplegic solutions were used. Use of these solutions results in improved recovery of ventricular function after prolonged periods of global ischemia when compared with either standard crystalloid cardioplegic solutions or oxygenated blood cardioplegic solutions. Furthermore, intracellular pH and myocardial ATP levels are well maintained during protracted periods of global myocardial ischemia with oxygenated perfluorochemical cardioplegic solutions. Based on these convincing experimental results, clinical investigation of an oxygenated perfluorochemical cardioplegic solution is warranted. Although current methods of myocardial protection during open heart surgery usually are adequate, patients undergoing complicated open heart surgical procedures or those with significant left ventricular dysfunction prior to surgery--that is, those patients most in need of highly effective myocardial protection--would likely benefit substantially if oxygen were delivered via the cardioplegic solution. Furthermore, perfluorochemical solutions may be especially useful for cardiopulmonary bypass pump priming in patients unable to accept whole blood transfusion during open heart surgery.

Blood Substitutes↗

PubMed1985

The use of muscle flaps in the repair of aortic defects.

The successful repair of an infected arterial anastomosis is often hampered by the need to leave prosthetic material at the site of infection. To determine whether an aortic defect could be repaired by direct closure with a muscle flap, thereby eliminating the need for prosthetic material, we subjected 33 young pigs weighing 17 to 19 kg to a left lateral thoracotomy under sterile conditions. An aortic defect 2 cm in diameter was created in the descending thoracic aorta just distal to the origin of the left subclavian artery. In one group (n = 11), this defect was patched with a freshly harvested but devascularized segment of chest wall muscle. In another group (n = 22), the aortic defect was patched with a vascularized chest wall muscle flap. Pigs were followed for up to 12 weeks and evaluated by arteriography and postmortem examination. There were no deaths or vascular complications attributable to the muscle flap repair in any pig. Pseudointimal formation began within 24 hours postoperatively and was of comparable thickness to the original arterial wall by 12 weeks. No aneurysmal changes were noted in any animal, and normal aortic luminal dimensions were preserved despite a tripling in mean body weight over the 12 week period. The loss of flap viability appeared to offer no threat to vascular integrity, as the free muscle patches, although undergoing cell necrosis and substantial remodeling, remained intact. These results demonstrate the short-term feasibility of using viable muscle flaps to patch aortic defects in situations wherein the use of prosthetic material would be undesirable.

Animals↗

PubMed1984

Progression and resolution of myocardial reflow injury.

The development of and recovery from a severe yet nonlethal myocardial injury following hyperkalemic cardioplegia and prolonged hypothermic global ischemia was examined over 14 days in a rat model of heterotopic intraabdominal cardiac isograft transplantation. Mitochondrial enzymatic markers of myocardial ischemic injury and light microscopic signs of damage were examined. Eighteen hearts were arrested in situ using hyperkalemic cardioplegia and subjected to a mean of 38 min of ischemia at 20 degrees C as transplantation was achieved. No changes in mitochondrial creatine kinase (CKm) activity, mitochondrial malate dehydrogenase (MDHm) activity, their ratio, or morphologic evidence of injury were found during 8 days of reperfusion. In a second group of 66 hearts, the duration of hypothermic cardioplegic ischemia was extended by 120 min before transplantation. Neither unreperfused hearts nor hearts reperfused for only 1 hr demonstrated significant depression of enzyme activities or microscopic evidence of injury. However, after 1 day of reperfusion, CKm and MDHm activities were depressed to 36 and 44% of control levels (P less than 0.05). These activities had returned to control levels by 2 days of reperfusion and remained stable for 12 days thereafter. Light microscopic analysis revealed cellular injury to be maximal at 1 to 2 days of reperfusion with gradual improvement noted over the following 12 days. These observations suggest the existence of a mitochondrial injury following prolonged cardioplegic arrest and hypothermic global ischemia that is maximal after 24 hr of reperfusion but shows evidence of improvement thereafter. These findings justify aggressive support of the poorly functioning heart for the first few days after prolonged global ischemia.

Animals↗

PubMed1984

A comparison of Blalock-Taussig, Waterston, and polytetrafluoroethylene shunts in children less than two weeks of age.

Results obtained with Blalock-Taussig, Waterston, and polytetrafluoroethylene (PTFE) shunts were compared in 67 cyanotic infants less than 2 weeks of age. A different shunt was preferably used at each of three institutions. The incidences of early shunt failure (3 out of 21, 14%), mortality after revision of early shunt failure (0 out of 3), and overall hospital mortality (1 out of 21, 5%) were all lowest for the PTFE shunt. Incidence of congestive heart failure secondary to excessive flow was comparable for the Blalock-Taussig and PTFE shunts, both of which were lower than the Waterston shunt. Cumulative probabilities of late shunt adequacy were calculated for hospital survivors. At 1 year, all shunts provided comparable adequate palliation (greater than 80%). Probability of late shunt failure was significantly higher (p = 0.04) for the PTFE shunt at 3.5 years. Results suggest that the PTFE shunt may be the safest and most effective shunt in neonates, but that elective shunt replacement or total repair may be warranted in the first or second year of life.

Age Factors↗

PubMed1984

Identification and control of noncoronary collateral blood flow.

To identify the source of noncoronary collateral myocardial blood flow and to establish methods to control it during induced ischemia, 29 dogs were placed on cardiopulmonary bypass. The right and left ventricles were vented, vent flows were measured volumetrically, and intracavitary left ventricular (LV) pressures were monitored. After induction of ischemia by aortic cross-clamping and infusion of cardioplegic solution, six different microspheres 7 to 10 microns in diameter were injected into the aorta at six different times to measure myocardial blood flow during the following interventions:vent drainage of the right or left ventricle or both, proximal ligation of both coronary arteries, severance of the proximal pulmonary artery or the ascending aorta or both, and ligation of the bronchial arteries. Without effective LV venting, LV intracavitary pressure rose to 7.0 +/- 0.1 mm Hg (mean +/- standard error of the mean) and myocardial blood flow in the anterior left ventricle was 2.3 +/- 1.3 ml/100 gm/min. When the LV vent was opened, vent flow was 35.9 +/- 3.5 ml/min and myocardial blood flow fell to 0.3 +/- 0.2 ml/100 gm/min. Right ventricular (RV) vent flow was absent except when the LV vent was occluded, and this RV vent flow was abolished by ligating the coronary arteries. With bronchial artery ligation, LV vent flow ceased and myocardial blood flow was virtually absent. These studies demonstrate that myocardial blood flow does occur during induced ischemia, but that the source of this blood flow is primarily through systemic-pulmonary channels. True noncoronary collateral myocardial blood flow was virtually nonexistent.

Animals↗

PubMed1984

Operative intervention for postinfarction angina.

Thirty-four patients (26 men and 8 women) underwent myocardial revascularization following myocardial infarction (MI) at the Johns Hopkins Hospital during 1980 through 1982. Average age was 59 years. Of the 33 patients with unstable angina, 61% had ischemia in the infarct zone and 39% had "ischemia at a distance." Mean time from MI to operation was 16 days. The MIs were equally divided between a transmural and a subendocardial location. Eleven patients had a history of congestive heart failure. Intraaortic balloon pumping was used preoperatively for anginal stabilization in 14 patients. Mean ejection fraction for the group was 52%. There were 3 operative deaths, all 3 due to myocardial failure. Late follow-up (mean, 13.7 months; range, 6 to 35 months) is complete for 28 patients. There was 1 late death, secondary to cardiac failure. There were no late MIs. Angina had recurred in 5 patients, but only 2 were taking antianginal medication. At the time of follow-up, 52% of patients were in New York Heart Association Functional Class I. This experience suggests that operative intervention for postinfarction angina can be accomplished with an acceptable mortality and thereby increase survival, reduce the later occurrence of MI, and relieve angina in this high-risk group.

Aged↗

PubMed1984

Percutaneous transluminal balloon valvuloplasty for pulmonary valve stenosis.

Transluminal balloon valvuloplasty was used to treat congenital pulmonary valve stenosis in 20 patients. Follow-up cardiac catheterization was performed in 11 patients at intervals of from 2 to 12 months after the procedure. Peak systolic pressure gradient across the pulmonic valve decreased from 68 +/- 27 to 23 +/- 5 mm Hg (p less than .001) after valvuloplasty. There were no complications. Follow-up catheterization demonstrated persistent relief of right ventricular hypertension in the patients with typical pulmonary valve stenosis.

Adolescent↗

PubMed1984

Maintenance of aerobic metabolism during global ischemia with perfluorocarbon cardioplegia improves myocardial preservation.

We used phosphorus-31 nuclear magnetic resonance to test the ability of a perfluorocarbon blood substitute that has been shown in previous studies to improve oxygen delivery to hypothermic myocardium to maintain aerobic high-energy phosphate metabolism during total global ischemia. Twenty-three isolated perfused rabbit hearts were subjected to 180 min of hypothermic (23 degrees C) global ischemia followed by 45 min of normothermic reperfusion. Hearts received multiple doses of a cardioplegic solution that contained either oxygenated perfluorocarbon (Fluosol O2), nonoxygenated perfluorocarbon (Fluosol N2), or standard crystalloid hyperkalemic cardioplegic solution (STD-KCl) at 30 min intervals. Recovery of isovolumic left ventricular developed pressure (LVDP) was used to assess preservation of contractile function. Recovery of LVDP was 84 +/- 19% of preischemic control values with Fluosol O2, 68 +/- 16% with Fluosol N2, and 67 +/- 17% with STD-KCl (p = .058 vs Fluosol N2 and p = .056 vs STD-KCl). During 3 hr of ischemia intracellular pH (pHi) fell to 6.68 +/- 0.20 with STD-KCl and to 6.71 +/- 0.14 with Fluosol N2 but remained above 7.00 throughout the ischemic period with Fluosol O2 (p less than .0001 vs Fluosol N2 or STD-KCl). Myocardial ATP content was better preserved at 107 +/- 14% of control values with Fluosol O2 compared to 60 +/- 18% of control with Fluosol N2 and 75 +/- 21% of control with STD-KCl (p less than .001 vs Fluosol N2, p = .002 vs STD-KCl). Phosphocreatine (PCr) was also better preserved with Fluosol O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1984

The mechanism of mannitol in reducing ischemic injury: hyperosmolarity or hydroxyl scavenger?

The effectiveness of postischemic reperfusion with mannitol has been well documented in previous studies. Mannitol, a hyperosmolar agent, is also an effective scavenger of the cytotoxic hydroxyl radical. If mannitol acts solely as a hyperosmolar agent, hyperosmolar reperfusion with its isomer, glucose, should be equally effective. To elucidate the beneficial effect of mannitol, 24 isolated rabbit heart preparations were subjected to 60 min of hypothermic (27 degrees C) cardioplegic arrest and normothermic reperfusion. There were three study groups with eight hearts in each. Group I hearts were reperfused with an unmodified isosmolar solution. Group II hearts were reperfused with a hyperosmolar (350 mOsm/liter) solution containing glucose, and group III hearts had hyperosmolar (350 mOsm/liter) reperfusion with mannitol. Left ventricular function (developed pressure and maximum positive dP/dt) was measured isovolumically before and after ischemia. Coronary flow was measured volumetrically during reperfusion, and myocardial edema formation was determined after 45 min of reperfusion. Reperfusion with mannitol resulted in significant improvement in recovery of developed pressure (77.3 +/- 2.8% of control vs 65.5 +/- 2.9% in group I and 62.6 +/- 2.2% in group II; p less than .05). Mannitol-treated hearts also had significantly greater coronary flow throughout the reperfusion period and significantly less marked myocardial edema formation compared with hearts treated with isosmolar and hyperosmolar glucose. These data confirm the particular usefulness of mannitol in improving postischemic ventricular function, maintaining coronary blood flow during early reflow, and reducing myocardial edema formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Propranolol-induced postoperative hypertension following coronary artery bypass grafting.

Fifteen patients receiving propranolol preoperatively and undergoing coronary artery bypass grafting had serum propranolol levels determined preoperatively and at several times early postoperatively. In addition, the patients' hemodynamic parameters and postoperative sodium nitroprusside dose requirements were monitored. All patients had significant multivessel disease and normal left ventricular function. Preoperative serum propranolol levels ranged from 16 to 243 ng/ml, with a mean level of 92 +/- 17 ng/ml; propranolol measured at the end of bypass ranged from 0 to 92 ng/ml, with a mean level of 23 +/- 7 ng/ml. Fourteen patients (93%) had hypertension postoperatively and required intravenous sodium nitroprusside to maintain mean blood pressure at or below 90 mm Hg. According to linear regression analysis, the severity of the postoperative hypertension or, specifically, the nitroprusside dose requirements, correlated significantly with the patients' serum propranolol levels postoperatively (correlation coefficient, R = 0.76, with p less than 0.001). The one normotensive patient had no detectable serum propranolol at any time postoperatively. No correlation was noted between the patient's preoperative serum propranolol levels and the need for nitroprusside therapy postoperatively. These results demonstrate that there is a significant relationship between residual propranolol and the development of hypertension postoperatively.

Adult↗

PubMed1983

Treatment of restenosis of coarctation by percutaneous transluminal angioplasty.

Percutaneous transluminal angioplasty (PTA) was used successfully to treat coarctation restenosis in seven patients. The patients were 10 months to 17 years old at the time of the angioplasty, and the initial coarctation repair had been performed 10 months to 16 1/2 years previously. PTA reduced the systolic pressure gradient across the coarctation from a mean of 58 mm Hg before the procedure to a mean of 13 mm Hg immediately after PTA. Follow-up has been from 1 to 14 months and indicates that the decrease in the systolic pressure gradient is persistent.

Adolescent↗

PubMed1983

Reduction of myocardial ischemic injury with oxygen-derived free radical scavengers.

Experimental data suggesting that oxygen-derived free radicals may play a role in the myocardial injury associated with ischemia and reperfusion are presented. In several studies of prolonged global myocardial ischemia, the administration of free radical scavenging agents, such as superoxide dismutase, catalase, and mannitol, resulted in significantly better recovery of left ventricular function following reperfusion. In a region-at-risk model of localized myocardial ischemia, both superoxide dismutase and allopurinol significantly reduced the extent of myocardial necrosis that developed following reversible coronary arterial branch occlusion. The manner in which oxygen-derived free radicals may be harmful is examined. In particular, the possibility that these toxic species are involved in the exacerbation of the ischemic injury that develops upon reflow and reoxygenation is examined.

Animals↗