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G T Christakis

Publications and source records attributed to G T Christakis.

At least 55 records · Page 3Linked to original sources
PubMed1994

Determinants of low systemic vascular resistance during cardiopulmonary bypass.

Although low systemic vascular resistance occurs during normothermic and hypothermic cardiopulmonary bypass, the determinants of depressed systemic vascular resistance and its effect on outcomes are unknown. To assess the predictors and clinical effects of low systemic vascular resistance, 555 patients undergoing isolated coronary artery bypass grafting were evaluated prospectively. The extent of low systemic vascular resistance during bypass was estimated by the amount of the vasoconstrictor phenylephrine administered: group 1, 0 to 160 micrograms; group 2, 161 to 800 micrograms; group 3, more than 800 micrograms. Multivariate analysis identified bypass temperature, bypass time, and ventricular function as determinants of low systemic vascular resistance. Patients on normothermic bypass accounted for 65% of the patients in group 3 and only 34% of the patients in group 1 (p < 0.0001). The bypass time was longer in the patients in group 3 (97 +/- 28 minutes) than in the patients in group 1 (89 +/- 24 minutes; p < 0.006). Patients with a preoperative left ventricular ejection fraction of 0.40 or less required less phenylephrine during cardiopulmonary bypass (498 +/- 68 micrograms) than did patients with a fraction exceeding 0.40 (1,087 +/- 88 micrograms; p < 0.001). By multivariate analysis, advanced age and the presence of peripheral vascular disease were found to decrease the likelihood of low systemic vascular resistance during normothermic bypass. Diabetes, the left ventricular ejection fraction, the bypass time, and the total cardioplegia infused were found to influence the likelihood of low systemic vascular resistance during hypothermic bypass. Patients in group 3 had a higher cardiac index and lower-mean arterial pressure and systemic vascular resistance postoperatively. In those patients who received a left internal mammary artery graft, the incidences of the low-output syndrome (group 1, 4.9%; group 3, 2.7%; p = not significant) and myocardial infarction (group 1, 1.4%; group 3, 1.8%; p = not significant) were not influenced by the amount of phenylephrine infused during cardiopulmonary bypass. In those patients who were at high risk of suffering a stroke preoperatively, the hypotension induced by the low systemic vascular resistance and its treatment with phenylephrine was not associated with an increased incidence of stroke (group 1, 5.8%; group 3, 2.8%; p = not significant).

Aged↗
PubMed1994

Metaanalysis of prophylactic drug treatment in the prevention of postoperative bleeding.

Prophylactic drug treatment is one of several strategies to reduce postoperative blood loss and potentially limit homologous blood use in open heart surgery. A computerized MEDLINE search supplemented with manual bibliography reviews was performed for randomized clinical trials published in peer-reviewed English-language journals from January 1980 to June 1993. A metaanalysis was conducted of trials evaluating desmopressin (group DD, n = 13), epsilon-aminocaproic acid or tranexamic acid (group EA, n = 4), and aprotinin (group AP, n = 16). Eligible studies used placebo controls and administered the drug in a prophylactic manner. The primary study end point was postoperative chest tube loss (mL, mean +/- standard deviation). There was a significant reduction in postoperative chest tube loss detected for each of the active treatments versus the placebo (DD versus controls: percent reduction 0.11, p = 0.0021; EA versus controls: percent reduction 0.30, p < 0.0001; and AP versus controls: percent reduction 0.36, p < 0.0001). Therapy with EA or AP was associated with a greater reduction in chest tube loss than DD (EA versus DD, p = 0.0033, and AP versus DD, p < 0.0001). Secondary study end points were transfusion requirements, chest reexploration, and perioperative mortality. The volume of postoperative red cell transfusion (mean +/- standard deviation) was reduced with EA (p < 0.0001) or AP treatment (p < 0.0001) compared with a placebo or DD, whereas the proportion of patients given transfusions was limited only in the AP-treated patients (odds ratio 0.23; 95% confidence interval, 0.16 to 0.33; p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminocaproic Acid↗
PubMed1994

Endarterectomy of the left anterior descending coronary artery.

Increasing numbers of patients with extensive coronary artery disease present for surgical revascularization. Diffuse atherosclerosis of the anterior descending artery remains a significant challenge and endarterectomy may be required to increase graft outflow. A surgeon may choose local endarterectomy or be accidentally forced into endarterectomy when attempting to split a lesion distal to a critical stenosis. Distal traction endarterectomy may be performed through a medium sized arteriotomy and closed with a vein patch, to which an internal mammary artery (IMA) or saphenous vein graft is constructed. More diffuse disease, or the breaking of an endarterectomy specimen, may require a direct vision total endarterectomy of the entire length of the left anterior descending coronary artery (LAD), which is then closed by a long vein patch. The IMA is not usually grafted to such an extensive reconstruction. There has not been an increase in perioperative risk from LAD endarterectomy when compared to patients undergoing coronary artery bypass grafting without endarterectomy.

Cineangiography↗
PubMed1994

Initial clinical experience with the Toronto Stentless Porcine Valve.

We report our initial experience from April 1992 to November 1993 with a stentless porcine valve (Toronto SPV Valve, St. Jude Medical) for aortic valve replacement (AVR) in 21 consecutive patients and compare this group to a matched cohort that underwent AVR with a Hancock II (Medtronic) bioprosthesis. There were no hospital deaths in either group. Postoperative hospitalization was 5.5 +/- 0.8 versus 7.0 +/- 2.3 days (p = 0.004). Aortic cross-clamp time was 114.5 +/- 15.7 min in the SPV group and 96.0 +/- 25.0 min in the Hancock II group (p = 0.003). Complications in the SPV group were: one patient suffered perioperative infarction, one patient required late reoperation for left main stenosis, and one patient died suddenly following femoral thrombectomy at another center. Complications in the Hancock II group included: one patient with postoperative low output syndrome, and two late deaths (one from an aortic dissection and the other from chronic liver disease secondary to alcohol abuse). Comparison data indicate that the average size valve implanted in the SPV group was higher than in the Hancock II group (26.3 +/- 1.9 vs 24.0 +/- 1.9, p = 0.001). In the SPV group, 16 patients had 0 or trivial regurgitation and 1+ regurgitation was seen in 5 patients; regurgitation did not change over a 12-month follow-up. We observed a decrease in gradients over time (p < 0.01). Our results are compatible with a hypothesis that the ventricle undergoes remodeling over time, once the obstruction is relieved. We think the stentless design is an important feature that allows this to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Optimal antithrombotic therapy following aortocoronary bypass: a meta-analysis.

To evaluate the role of antithrombotic therapy, on preserving graft patency, we performed a meta-analysis of randomized clinical trials involving aspirin (ASA), dipyridamole (D), anticoagulants (AC) and placebo or nontreatment controls (P). Manual literature searches were performed supplemented by computerized MEDLINE listings complete to July 1991. Saphenous vein graft occlusion was determined by angiography (patients with > or = 1 distal anastomotic occlusion). The trial data were aggregated with the methods of Mantel and Haenszel. The results are reported as odds ratios (OR) +/- 95% confidence intervals (CI). Seventeen trials were evaluated. Aspirin strongly influenced graft occlusion [ASA +/- D vs P: OR 0.60, 95% CI 0.51, 0.71, P < 0.0001], but dipyridamole provided no additional benefit [ASA+D vs ASA: OR 0.94, 95% CI 0.72, 1.24, P = 0.71]. Anticoagulants reduced graft occlusion [AC vs P: OR 0.56, 95% CI 0.33, 0.93, P = 0.025] and the results were similar to that achieved with aspirin [ASA vs AC: OR 0.95, 95% CI 0.62, 1.44, P = 0.87]. The combination of aspirin and anticoagulants was superior to anticoagulants alone in two limited trials [ASA+AC vs AC: OR 0.55, 95% CI 0.33, 0.88, P = 0.01]. A low (100 mg) to medium (325 mg) daily aspirin dosage was more effective than a high dose (975 mg). Early postoperative treatment (< or = 6 h) strongly influenced graft occlusion while preoperative administration provided no additional benefit. No mortality advantage was identified for any antithrombotic therapy. Aspirin or anticoagulants enhance saphenous vein graft patency following aortocoronary bypass surgery, and a combination thereof deserves further investigation in a trial large enough to detect the effects of these treatments with respect to clinical events.

Anticoagulants↗
PubMed1993

Does coronary endarterectomy adversely affect the results of bypass surgery?

Coronary endarterectomy (TEA) is performed infrequently during coronary artery bypass graft (CABG) surgery due to the impression that it results in higher rates of myocardial infarction (MI), operative mortality (OM), and poor long-term outcome. To assess the effectiveness of TEA, 1,228 patients undergoing isolated CABG between 1982 and 1989 were evaluated. The incidence of OM (3.2%) and MI (6.0%) following TEA was similar to conventional CABG (OM = 3.8%, MI = 5.5%, p = NS). The incidence of low output syndrome (LOS, 15.1%) and intraaortic balloon pump insertion (IABP, 4.5%) following TEA was similar to conventional CABG (LOS = 12.6%, IABP = 6.0%, p = NS). The highest level of the cardiac specific isoenzyme (CK-MB) released following surgery was similar for the TEA group (46 +/- 49) and conventional CABG group (42 +/- 44, p = NS). Ventricular dysfunction, urgent surgery, left main stenosis, advanced age, and reoperative surgery were similar in the TEA and conventional CABG groups. At a mean follow-up of 4.2 years, 65.6% of all TEA patients were free of angina, 44.4% were gainfully employed, and 62% were in New York Heart Association Class I. The incidence of late myocardial infarction was 5.4%. The 5-year actuarial survival was 90%. Patients with double TEA and limited TEA ( < or = 3 cm TEA specimens) tended to have a lower 5-year survival. With strict criteria for selection of TEA patients and with significant technical experience, the short- and long-term results of TEA are comparable to conventional CABG.

Adult↗
PubMed1992

A randomized study of the systemic effects of warm heart surgery.

The technique of warm heart surgery is defined as continuous warm blood cardioplegia and normothermic cardiopulmonary bypass. Although the systemic effects of traditional myocardial protection are well known, the effects of warm heart surgery are not. In a prospective trial, 204 patients undergoing coronary artery bypass grafting were randomized to the warm heart surgery technique (normothermic group) or traditional intermittent cold blood cardioplegia and cardiopulmonary bypass (hypothermic group). The groups had similar heparin sodium requirement, activated clotting times, urine output, hematocrit, and blood product utilization. There were no differences in hemodynamics immediately after cardiopulmonary bypass. The normothermic patients had a higher incidence of spontaneous defibrillation at cross-clamp removal (84%) than the hypothermic patients (33%) (p less than 0.01). An increase in the flow rate of low K+ cardioplegia was necessary to eradicate electrical activity during aortic occlusion more often in the normothermic patients (20%) than in the hypothermic patients (3%) (p less than 0.01). When low K+ cardioplegia was ineffective, high K+ cardioplegia was necessary to eradicate electrical activity in 31% of the normothermic patients compared with 10% of the hypothermic patients (p less than 0.05). The total cardioplegia volume delivered to the normothermic group (4.7 +/- 1.9 L) was higher than that delivered to the hypothermic group (2.6 +/- 0.8 L) (p less than 0.01). Although urine output was similar in both groups, the serum K+ levels were higher in the normothermic group (5.7 +/- 0.8 mmol/L) than in the hypothermic group (5.3 +/- 0.8 mmol/L) (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1992

Coronary artery bypass grafting in patients with poor ventricular function. Cardiovascular Surgeons of the University of Toronto.

Although patients with severe ventricular dysfunction have improved long-term survival times after coronary bypass procedures, operative morbidity and mortality rates remain high. This study was designed to identify the contemporary risk factors for isolated coronary artery bypass grafting in this high-risk subgroup. Between January 1982 and December 1990, a total of 12,471 patients underwent isolated coronary artery bypass grafting. The 9445 patients with preoperative ejection fractions greater than 40% had a lower operative mortality rate (2.3%) than that of the 2539 patients with ejection fractions between 20% and 40% (4.8%) and that of the 487 patients with ejection fractions less than 20% (9.8%; p less than 0.001). However, patients with ejection fractions of less than 20% were demographically distinct from those with higher ejection fractions. This group was older, with fewer women, a higher frequency of left main stenosis, and more frequent requirement of urgent operation for unstable angina. The risk factors for operative death also varied with preoperative ejection fraction. The traditionally accepted risk factors--urgency of operation, left main coronary artery stenosis, reoperation, sex, and age--were predictive of risk of operative death for patients with ejection fractions greater than 40%. The risk of operative death for patients with ejection fractions between 20% and 40% was predicted by urgency of operation, reoperation, sex, myocardial protection, and age. The only predictor of risk of operative death for patients with ejection fractions less than 20% was urgency of operation. Patients undergoing isolated coronary artery bypass grafting who have severe ventricular dysfunction are therefore a highly selected, high-risk subgroup of patients who risk depends on the urgency of operation. Strategies to improve the results in these patients should be focused on patient selection, improvement of myocardial protection, and more aggressive preoperative treatment of myocardial ischemia.

Age Factors↗
PubMed1991

Retrograde continuous warm blood cardioplegia: a new concept in myocardial protection.

This report presents the results in our first clinical series of patients receiving continuous warm blood cardioplegia through the coronary sinus. Warm oxygenated blood cardioplegia has certain theoretical advantages, such as continuously supplying oxygen and substrates to the arrested heart while avoiding the side effects of hypothermia. Retrograde infusion of cardioplegia also offers certain advantages (eg, in valve operations and in patients with severe coronary artery disease) that are complementary to warm blood cardioplegia. Retrograde warm blood cardioplegia was used in 113 consecutive patients (85 men and 28 women with a mean age of 61 years) undergoing various procedures. Three percent of the patients died, 7% needed transient intraaortic balloon pump support, 6% had evidence of perioperative myocardial infarction, and 96% had spontaneous return of rhythm. There were no coronary sinus injuries. This new technique of retrograde continuous warm blood cardioplegia is a simple, safe, and reliable method of myocardial protection that may change the way we currently protect the heart intraoperatively.

Adult↗
PubMed1991

Technique and pitfalls of retrograde continuous warm blood cardioplegia.

The recent development of normothermic myocardial preservation and systemic perfusion during bypass has questioned the fundamental need for hypothermia during cardiac operations. The antegrade technique of almost continuous perfusion by the aortic root and vein grafts has been supplemented by continuous normothermic blood cardioplegia through the coronary sinus. Recently, great interest has been shown in this technique. It is important to describe the method in detail along with its potential shortcomings and dangers. This communication describes the technical details, pitfalls, and shortcomings of retrograde continuous warm blood cardioplegia.

Blood↗
PubMed1991

Current risk of coronary bypass for unstable angina.

The risk associated with surgical revascularization for unstable angina is critically dependent upon the clinical presentation of the patient. For this study, between January 1982 and December 1987, clinical, angiographic, operative and hospital outcome data were collected prospectively for 6539 patients undergoing surgery for unstable angina. Urgent surgery was performed in 1523 patients (23.3%), while 5016 (76.7%) underwent semielective revascularization. The mean age was 58.9 +/- 9.2 years and 805 patients (12.3%) were aged 70 years or above. The male:female ratio was 3.6:1. Depressed left ventricular function (left ventricular ejection fraction less than 40%) was present in 27.2% of the population. Preoperative myocardial infarction (within 30 days of surgery) had occurred in 588 patients (9.0%). Operative mortality was 4.6% (301 deaths). Stepwise logistic regression analysis was performed to determine the independent predictors of operative mortality. The following variables were selected in descending order: urgent surgery (P less than 0.001), coronary reoperation (P less than 0.001), depressed left ventricular (P less than 0.001), female gender (P less than 0.001), increasing age (P less than 0.001), left main stenosis (P = 0.002), and preoperative myocardial infarction (P less than 0.001). Predicted operative mortality varied between 0.5 +/- 0.3% and 82.6 +/- 12.7%. The most important determinant for patients with a preoperative myocardial infarction was left ventricular dysfunction, whereas urgent surgery for unstable angina was the most important risk variable in those without preoperative necrosis.

Adult↗
PubMed1991

Technical aspects of warm heart surgery.

Intermittent hypothermic cardioplegia has been adopted as the method of choice for myocardial protection by most surgeons. The most important aspect of this protection is believed to be adequate hypothermia. An alternative technique has been developed, based on the principles of electromechanical arrest and normothermic aerobic perfusion using continuous warm blood cardioplegia. With this method of myocardial protection the heart is maintained at 37 degrees C throughout the operative procedure. The specific technical aspects used shall be described in detail.

Aortic Valve↗
PubMed1991

Recent preoperative myocardial infarction increases the risk of surgery for unstable angina.

Patients with postinfarction angina undergoing surgery for unstable angina face an increased risk of operative mortality. Between January 1982 and December 1987, clinical, angiographic, and operative data was collected prospectively in 588 unstable patients with a prior myocardial infarction within 30 days of surgery (MI) and 5951 unstable patients without preoperative damage (NONMI). MI patients were characterized as being older (age greater than or equal to 70 years: MI, 19.7%; NONMI, 11.6%; p less than 0.001) and having more left ventricular dysfunction (left ventricular ejection fraction less than 40%: MI, 34.8%; NONMI, 26.4%; p less than 0.001). Semi-elective surgery was performed in 82.0% of NONMI patients while 76.9% of MI patients underwent urgent surgery. Operative mortality was increased in MI patients (MI, 11.1%; NONMI, 4.0%; p less than 0.001) which was related to the extent of preoperative MI (non-Q wave, 8.3%; Q wave, 17.5%; p less than 0.001). Stepwise logistic regression analysis identified preoperative MI as an independent risk variable of operative mortality for unstable angina. Separate multivariate analyses were performed to identify the independent predictors for MI and NONMI patients. The multivariate predictors of operative death for MI patients were left ventricular dysfunction, reoperative coronary surgery, nonuse of the internal mammary, age, transmural MI (relative risk 2.11 vs non-Q wave infarction) and left main stenosis. For NONMI patients, the independent variables were urgent operation, left ventricular dysfunction, reoperation, female gender, left main stenosis, and age. The results of this study indicate that recent preoperative MI adversely influences the surgical results in patients with unstable angina. Alternative treatment strategies are warranted for high risk patients, particularly those with transmural MIs and impaired ventricular function.

Adult↗
PubMed1990

Heart valve operations in patients with active infective endocarditis.

Sixty-two consecutive patients underwent heart valve operation for active infective endocarditis. There were 42 men and 20 women whose mean age was 49 years (range, 21 to 79 years). The infection was in the aortic valve in 37 patients, the mitral valve in 18, the aortic and mitral valves in 5, and the tricuspid valve in 2. Twenty-four patients had prosthetic valve endocarditis. Staphylococcus and Streptococcus were responsible for 86% of the infections. Annular abscess was encountered in 33 patients. Complex valve procedures involving reconstruction of the left ventricular inflow or outflow tract or both were performed in 31 patients. There were three operative deaths (4.8%). Predictors of operative mortality were prosthetic valve endocarditis, preoperative shock, and annular abscess. Patients were followed for 1 month to 130 months (mean follow-up, 43 months). Only 1 patient required reoperation for persistent infection. There were ten late deaths. Most survivors (96%) are currently in New York Heart Association class I or II. The 5-year actuarial survival was 79% +/- 7%. These data demonstrate excellent results in patients with native valve endocarditis, and support the premise that patients with prosthetic valve endocarditis should have early surgical intervention.

Adult↗
PubMed1990

Right ventricular function and metabolism.

Right ventricular protection may be limited with current methods of cardioplegic delivery. Sensitive measurements of right and left ventricular function and metabolism were made in 30 patients undergoing elective coronary artery bypass surgery with cold cardioplegic arrest. Myocardial adenine nucleotide concentrations decreased with cardioplegia and reperfusion in both the right and left ventricles despite adequate levels of precursors, suggesting perioperative mitochondrial dysfunction. Postoperatively, right and left ventricular pressures were measured with micromanometer catheters and volumes were measured by nuclear ventriculography. Right and left ventricular systolic elastance was calculated by the isochronic method and by the end-systolic method. Both methods provided sensitive indexes of end-systolic elastance. This study demonstrated that right ventricular function and metabolism can be evaluated by methods analogous to methods used in the left ventricle. These results suggest that right ventricular functional and metabolic recovery are delayed despite apparently adequate myocardial protection. Sensitive measurements may permit improved assessment of alternative methods of right ventricular protection.

Adenine Nucleotides↗
PubMed1989

Operation for acute postinfarction mitral insufficiency using continuous oxygenated blood cardioplegia.

Patients with acute-onset mitral insufficiency and cardiogenic shock after myocardial infarction have a high incidence of operative death and morbidity. Patients with ventricular dysfunction, myocardial ischemia, and limited cardiac reserve undergoing an urgent operation represent a challenge to modern methods of myocardial protection. To improve results of operation a new technique was devised with continuous infusion of cold oxygenated blood cardioplegia during the entire cross-clamp period. Between 1984 and 1988, 19 consecutive patients with severe mitral regurgitation and cardiogenic shock (systolic blood pressure less than 60 mm Hg) after myocardial infarction underwent urgent myocardial revascularization, mitral valve replacement, or both. Left ventricular ejection fraction was less than 40% in 16 of 19 patients. All patients had suffered myocardial infarction within 4 weeks of operation and underwent an urgent operation within 24 hours of the onset of hemodynamic compromise. Severe three-vessel coronary artery disease was present in 16 of the 19 patients. A continuous infusion of blood cardioplegia was instituted at aortic cross-clamping and continued throughout the cross-clamp period. Infusion of continuous blood cardioplegia was also instituted through each completed distal vein graft. Myocardial septal and left ventricular apical temperatures were maintained at 10 degrees +/- 2 degrees C throughout the cross-clamp period. There were two in-hospital deaths (mortality, 10.5%) and low output syndrome was present in 10 patients (53%). At a mean follow-up of 2.5 years, there was one late death and 14 of the 16 remaining patients were in New York Heart Association functional class I or II.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood↗
PubMed1989

Visceral and limb perfusion during thoracoabdominal aortic aneurysm repair.

Patients undergoing thoracoabdominal aortic aneurysm repair are at high risk of operative morbidity and death. Aortic clamping and unclamping stresses the myocardium, interrupts visceral and limb perfusion, and leads to metabolic acidosis. Use of a simple technique to preserve distal perfusion during the period of aortic clamping may reduce perioperative morbidity. We describe a technique of visceral and limb perfusion that may reduce surgical risk in high-risk patients.

Anastomosis, Surgical↗