Coronary artery bypass grafting in patients over 70 years old: the influence of age and surgical technique on early and mid-term clinical outcomes

OBJECTIVE

To investigate the influence of age and modern techniques of coronary artery bypass grafting with or without cardiopulmonary bypass on early and mid-term mortality and morbidity in a consecutive series of elderly patients.

METHODS

From April 1996 to December 2000, data of 3842 patients undergoing coronary revascularisation were prospectively entered into a database. Data were extracted for 990 patients older than 70 years: (A) 70-74 years, (n=659); (B) 75 or more years, (n=331).

RESULTS

A total of 990 elderly patients (> or = 70 years) underwent coronary revascularisation, 219 (22.1%) with off-pump surgery. Elderly patients were more likely to have higher CCS, NYHA and EuroScores, history of previous MI, unstable angina, renal dysfunction, left main stem disease > or = 50%, and to be urgent. However, they were less likely to be overweight. In-hospital mortality, occurrence of re-intubation, renal dysfunction, and hospital stay were significantly higher in this elderly group. Overall, the distribution of mortality was doubled in the female gender although this was not statistically significant. Patients undergoing on-pump surgery had lower EuroScore, were less likely to be >75 years of age, likely to have obesity or hypercholesterolaemia, or to have suffered a previous cerebro-vascular accident. However, they had more extensive coronary disease, were more likely to have unstable angina, and received more grafts than those undergoing off-pump surgery. After adjustment for prognostic variables, off-pump surgery was found to be associated with reduced inotropic use, intra-operative arrhythmias, blood loss and transfusion requirement when compared to on-pump coronary surgery (point estimates of odd ratios, 0.26-0.87) (all P<0.05). Mid-term mortality or cardiac-related events were similar in the two groups.

CONCLUSIONS

Early but not mid-term mortality is higher in patients aged 75 or more years when compared with those aged 70-74 years. Off-pump coronary artery bypass surgery is safe and effective in the elderly population.

Detection of postoperative pseudoaneurysms following abdominal aortic aneurysm repair in Behçet's disease by MRA

We report the development of two anastomotic pseudoaneurysms in a patient with Behçet's disease eighteen months after abdominal aortic aneurysm repair. Major asymptomatic vascular complications should be suspected in patients with Behçet's disease with a history of vascular surgery and treated expediently due to the risk of rupture. Magnetic resonance angiography, contrast-enhanced computed tomography or ultrasound scanning should be performed at least every 6 months after vascular surgery.

Myocardial injury in hypertrophic hearts of patients undergoing aortic valve surgery using cold or warm blood cardioplegia

OBJECTIVES

Myocardial protection techniques during cardiac surgery have been largely investigated in the clinical setting of coronary revascularisation. Few studies have been carried out on patients with left ventricular hypertrophy where the choice of delivery, and temperature of cardioplegia remain controversial. This study investigates metabolic changes and myocardial injury in hypertrophic hearts of patients undergoing aortic valve surgery using antegrade cold or warm blood cardioplegia.

METHODS

Thirty-five patients were prospectively randomised to intermittent antegrade cold or warm blood cardioplegia. Left ventricular biopsies were collected at 5min following institution of cardiopulmonary bypass, 30min after cross-clamping the aorta and 20min after cross-clamp removal, and used to determine metabolic changes during surgery. Metabolites (adenine nucleotides, amino acids and lactate) were measured using high pressure liquid chromatography and enzymatic techniques. Postoperative myocardial troponin I release was used as a marker of myocardial injury.

RESULTS

Ischaemic arrest was associated with significant increase in lactate and alanine/glutamate ratio only in the warm blood group. During reperfusion, alanine/glutamate ratio was higher than preischaemic levels in both groups, but the extent of the increase was considerably greater in the warm blood group. Troponin I release was markedly (P<0.05, Mean+/-SD) lower at 1, 24 and 48h postoperatively in the cold compared to the warm blood group (0.51+/-0.37, 0.37+/-0.22 and 0.27+/-0.19 vs. 0.75+/-0.42, 0.73+/-0.51 and 0.54+/-0.38ng/ml for cold vs. warm group, respectively).

CONCLUSIONS

Cold blood cardioplegia is associated with less ischaemic stress and myocardial injury compared to warm blood cardioplegia in patients with aortic stenosis undergoing valve replacement surgery. Both cardioplegic techniques, however, confer sub-optimal myocardial protection.

Coronary revascularization with or without cardiopulmonary bypass in patients with preoperative nondialysis-dependent renal insufficiency

BACKGROUND

Preoperative renal insufficiency is a predictor of acute renal failure in patients undergoing conventional coronary artery bypass grafting. Off-pump coronary artery bypass operations have been shown to reduce renal dysfunction in patients with normal renal function, but the effect of this technique in patients with preoperative nondialysis-dependent renal insufficiency is unknown.

METHODS

From June 1996 to December 1999, data of 3,250 consecutive patients undergoing coronary artery bypass grafting were prospectively entered into the Patient Analysis & Tracking Systems (PATS, Dendrite Clinical Systems, London, UK). Two hundred and fifty-three patients with preoperative serum creatinine more than 150 micromol/L were identified (202 patients on-pump, 51 patients off-pump), and clinical outcomes were analyzed. Serum creatinine and urea, in-hospital mortality, and morbidity were compared between groups. The association of perioperative factors with acute renal failure was investigated by multiple logistic regression analysis.

RESULTS

Preoperative characteristics were similar between the groups. Mean number of grafts was 2.9 +/- 0.8 and 2.3 +/- 0.8 in the on-pump and off-pump groups, respectively (p < 0.0001). Comparison between groups showed a significantly higher incidence of stroke, inotropic requirement, blood loss, and transfusion of red packed cell and platelets in the on-pump group (all p < 0.05). Postoperative serum creatinine and urea were higher in the on-pump group with a significant difference at 12 hours postoperatively (p < 0.05). Logistic regression analysis identified cardiopulmonary bypass, serum creatinine level 60 hours postoperatively, inotropic requirement, need for intraaortic balloon pump, transfusion of red packed cell, and hours of ventilation as predictors of postoperative acute renal failure.

CONCLUSIONS

This study suggests that off-pump coronary artery bypass operations reduce in-hospital morbidity and the likelihood of acute renal failure in patients with preoperative nondialysis-dependent renal insufficiency undergoing myocardial revascularization.

One-stage coronary and abdominal aortic operation with or without cardiopulmonary bypass: early and midterm follow-up

BACKGROUND

The aim of this study was to compare hospital, early, and late clinical outcomes for patients undergoing one-stage, coronary and abdominal aortic surgical intervention with and without cardiopulmonary bypass.

METHODS

From March 1990 to September 1999, 42 consecutive patients underwent combined operations at a single institution. Cardiopulmonary bypass and cardioplegic arrest were used during coronary revascularization in the first 20 patients (on-pump group), and the next 22 patients received the one-stage operations on the beating heart (off-pump group).

RESULTS

Baseline characteristics were similar between groups. Three cardiac-related hospital deaths occurred in the on-pump group and one such death in the off-pump group (p = 0.25). Cardiac-related events, pulmonary complications, inotropic support, blood loss and transfusion requirements, intensive care unit stay, and hospital stay were significantly reduced in the off-pump group (all, p < 0.05). The actuarial survival rates in the on-pump and off-pump groups were 80% and 95%, respectively, at 1 year (p = 0.13) and 75% and 89%, respectively, at 3 years (p = 0.22). Freedom from cardiac-related events at 1-year follow-up was 91% in the off-pump group and 65% in the on-pump group (p < 0.05). No difference in cardiac-related events between groups was observed at 3 years.

CONCLUSIONS

Off-pump coronary surgical procedures decrease postoperative complications in high-risk patients undergoing simultaneous coronary and abdominal aortic operations compared with the conventional one-stage procedure. The early benefits achieved with off-pump surgical intervention are not at the expense of the long-term clinical outcome.

Clinical and angiographic outcome of different surgical strategies of bilateral internal mammary artery grafting

Long-term survival, relief of angina, and prevention of myocardial infarction after coronary revascularization are related to the preoperative status of the patient, progression of coronary artery atherosclerosis, and the patency of the conduits used. The increased use of the internal mammary artery for coronary grafting depends upon the accumulation of data on superior late patency compared with venous conduits. These data have supported the simultaneous use of both left and right internal mammary arteries with reported improved late survival. However, controversy still surrounds the clinical and angiographic outcomes of some of the surgical strategies of bilateral internal mammary artery grafting. This review examines a range of surgical strategies of bilateral internal mammary artery grafting and their mid- and long-term clinical and angiographic outcomes. From the available data, careful preoperative selection of patients is paramount. Clinical and angiographic outcome of bilateral internal mammary grafting is superior to single internal mammary grafting with supplemental vein grafts when pedicled, sequential, or free aorto-coronary internal mammary artery is used. Further studies are needed to evaluate the midterm and long-term clinical and angiographic outcomes of complex strategies such as Y or T procedures.

Reduced postoperative blood loss and transfusion requirement after beating-heart coronary operations: a prospective randomized study

OBJECTIVE

Coronary artery bypass grafting on the beating heart through median sternotomy is a relatively new treatment, which allows multiple revascularization without the use of cardiopulmonary bypass. A prospective randomized study was designed to investigate the effect of coronary bypass with or without cardiopulmonary bypass on postoperative blood loss and transfusion requirement.

METHODS

Two hundred patients with coronary artery disease were prospectively randomized to (1) on-pump treatment with conventional cardiopulmonary bypass and cardioplegic arrest and (2) off-pump treatment on the beating heart. Postoperative blood loss identified as total chest tube drainage, transfusion requirement, and related costs together with hematologic indices and clotting profiles were analyzed.

RESULTS

There was no difference between the groups with respect to preoperative and intraoperative patient variables. The mean ratio of postoperative blood loss and 95% confidence interval between groups was 1.64 and 1.39 to 1.94, respectively, suggesting on average a postoperative blood loss 1.6 times higher in the on-pump group compared with the off-pump group. Seventy-seven patients in the off-pump group required no blood transfusion compared with only 48 in the on-pump group (P <.01). Furthermore, less than 5% of patients in the on-pump group required fresh frozen plasma and platelet transfusion compared with 30% and 25%, respectively, in the on-pump group (both P <.05). Mean transfusion cost per patient was higher in the on-pump compared with that in the off-pump group ($184.8 +/- $35.2 vs $21.47 +/- $6.9, P <.01).

CONCLUSIONS

Coronary artery bypass grafting on the beating heart is associated with a significant reduction in postoperative blood loss, transfusion requirement, and transfusion-related cost when compared with conventional revascularization with cardiopulmonary bypass and cardioplegic arrest.

Off-pump coronary artery bypass surgery for critical left main stem disease: safety, efficacy and outcome

OBJECTIVES

To determine whether patients with critical left main stem (LMS) coronary artery disease can undergo off-pump coronary artery bypass (OPCAB) surgery safely and successfully.

METHODS

From May 1996 to March 2000 data for patients with critical (> or =50%) LMS stenosis who underwent conventional coronary artery bypass surgery with cardiopulmonary bypass (CCAB) or without (OPCAB) were collected prospectively using the Patient Analysis & Tracking System. A reusable pressure stabilizer, intra-coronary shunts and a single posterior pericardial stitch exposure technique were used in all OPCAB cases. Non-randomized, retrospective data analysis included demographic and preoperative risk factors, operative details, clinical outcome and early follow-up.

RESULTS

During the study period 387 patients with LMS stenosis underwent surgery (OPCAB n=75, CCAB n=312). Groups were similar in terms of preoperative and intraoperative variables although CCAB patients received significantly more grafts per patient (3.1+/-0.73 vs. 2.6+/-0.76, P< or =0.001). Mortality was similar in both groups (OPCAB 1.3% vs. CCAB 2.6%). OPCAB patients when compared to CCAB patients had a lower requirement for postoperative inotropes (12.0% vs. 38.1%, P=0.0001), temporary postoperative pacing (2.7% vs. 10.1%, P=0.02), and blood product transfusion (6.7% vs. 31.4%, P<0.0001), a lower incidence of postoperative chest infection (0% vs. 6.7%, P=0.02) and a slightly reduced postoperative length of stay (7.9+/-5.46 vs. 8.3+/-5.11 days, P=0.01). At 24 months follow-up, CCAB and OPCAB actuarial survival was 94.1+/-1.7% and 97.7+/-2.3%, respectively.

CONCLUSIONS

OPCAB surgery is safe and effective in patients with critical LMS disease.

Haemodynamic changes during beating heart coronary surgery with the 'Bristol Technique'

OBJECTIVES

Optimal exposure and stabilization of the target coronary vessel is essential to allow the construction of a precise coronary anastomosis during off pump coronary surgery. However, this might be achieved at the expense of significant haemodynamic deterioration, particularly while grafting the circumflex and the posterior descending coronary arteries. The present study was designed to assess the haemodynamic changes with the beating heart positioned for grafting the three main coronaries.

METHODS

Twenty-nine consecutive patients (21 male, mean age 62.6+/-7.1 years) undergoing off pump coronary surgery were enrolled in the study. Three different surgical settings of exposure and stabilization were used according to the site of anastomosis: left anterior descending (LAD - set-up 1; n=29), posterior descending (PDA - set-up 2; n=15), and circumflex (Cx - set-up 3; n=21) coronary arteries. Haemodynamic measurements were recorded before any cardiac manipulation (baseline) in set-ups 1, 2 and 3, and immediately after the completion of each distal anastomosis with the heart returned to its anatomical position.

RESULTS

There were no marked changes in heart rate (HR) and systemic mean arterial pressure during the construction of the anastomoses for any of the three surgical settings. Set-up 1 (LAD) showed a decrease of 15.5% in stroke volume (SV) and an increase of 9% in pulmonary capillary wedge pressure (PCWP) compared to baseline (both P<0.05), with all the other haemodynamic parameters remaining unchanged. Set-up 2 (PDA) showed a marked decrease in SV and cardiac index (CI), and an increase in central venous pressure (CVP) when compared to baseline (all P<0.05). The most extensive changes were observed in set-up 3 (Cx) with a considerable reduction in SV and CI, and an increase in CVP, PCWP, pulmonary arterial pressure, and systemic vascular resistance index (all P<0.05). These haemodynamic changes were transient and totally recovered after the heart was returned to its anatomical position.

CONCLUSIONS

Exposure and stabilization of the three main coronary arteries during beating heart surgery does not produce any appreciable change in systemic blood pressure and HR. The haemodynamic deterioration observed during the construction of the circumflex and posterior descending coronary arteries distal anastomoses is transient and well tolerated with no adverse clinical events.

Predictors of atrial fibrillation after conventional and beating heart coronary surgery: A prospective, randomized study

BACKGROUND

Atrial fibrillation (AF) increases the morbidity of CABG. The pathophysiology is uncertain, and its prevention remains suboptimal. This prospective, randomized study was designed to define the role of cardiopulmonary bypass (CPB) and cardioplegic arrest in the pathogenesis of this complication.

METHODS AND RESULTS

Two hundred patients were prospectively randomized to (1) on-pump conventional surgery [(100 patients, 79 men, mean age 63 (40 to 77) years)] with normothermic CPB and cardioplegic arrest of the heart or (2) off-pump surgery [(100 patients, 82 men, mean age 63 (38 to 86) years)] on the beating heart. Heart rate and rhythm were continuously monitored with an automated arrhythmia detector during the first 72 hours after surgery. Thereafter, routine clinical observation was performed and continuous monitoring restarted in the case of arrhythmia. The association of perioperative factors with AF was investigated by univariate analysis. Significant variables were then included into a stepwise logistic regression model to ascertain their independent influence on the occurrence of AF. There were no significant baseline differences between groups. Thirty-nine patients in the on-pump group and 8 patients in the off-pump group had postoperative sustained AF (P:=0.001). Univariate analysis showed that CPB inclusive of cardioplegic arrest, postoperative inotropic support, intubation time, chest infection, and hospital length of stay were predictors of AF (all P:<0.05). However, stepwise multivariate regression analysis identified CPB inclusive of cardioplegic arrest as the only independent predictor of postoperative AF (OR 7.4; CI 3.4 to 17.9).

CONCLUSIONS

CPB inclusive of cardioplegic arrest is the main independent predictor of postoperative AF in patients undergoing coronary revascularization.

Inflammatory response after coronary revascularization with or without cardiopulmonary bypass

BACKGROUND

We sought to investigate the effect of multiple coronary artery bypass grafting (CABG) with or without cardiopulmonary bypass (CPB) on the perioperative inflammatory response.

METHODS

Sixty patients undergoing CABG were randomly assigned to one of two groups: (A) on pump with conventional CPB and cardioplegic arrest, and (B) off pump on the beating heart. Serum samples were collected for estimation of neutrophil elastase, interleukin 8 (IL-8), C3a, and C5a preoperatively and at 1, 4, 12, and 24 hours postoperatively. Furthermore, white blood cell (WBC), neutrophil, and monocyte counts were carried out preoperatively and at 1, 12, 36 and 60 hours postoperatively. Overall incidence of infection and perioperative clinical outcome were also recorded.

RESULTS

The groups were similar in terms of age, weight, gender ratio, extent of coronary disease, left ventricular function, and number of grafts per patient. Neutrophil elastase concentration peaked early after CPB in the on-pump group, with a decline with time. Repeated-measures analysis of variance between groups and comparisons at each time point (modified Bonferroni) showed elastase concentrations were significantly higher in the on-pump than the off-pump group (both p < 0.0001). IL-8 increased significantly after surgery in the on-pump group, with no decline during the observation period (p = 0.01 vs off pump). C3a and C5a rose early after surgery in both groups when compared with baseline values. Postoperative WBC, neutrophil, and monocyte counts were significantly higher in the on-pump than the off-pump group (p < 0.01). Finally, the incidence of postoperative overall infections was significantly higher in the on-pump group (p < 0.0001 vs off pump).

CONCLUSIONS

CABG on the beating heart is associated with a significant reduction in inflammatory response and postoperative infection when compared with conventional revascularization with CPB and cardioplegic arrest.

Emergency repair of type A aortic dissection in type IV Ehlers-Danlos syndrome

Ehlers-Danlos syndrome type IV is a distinctive syndrome in which thin and fragile skin, premature ageing, bruising and scarring are combined with lethal or life-threatening arterial weakness. Aortic rupture either at the aortic root and arch, or sometimes lower down the artery, are particularly characteristic. Even quite minor injury can produce dangerous vascular tearing and damage. Technical difficulties encountered in arterial repair or venous ligature are particularly worrying. The authors report the treatment of a ruptured type A aortic dissection associated with Ehlers-Danlos syndrome where the extreme fragility of the tissues and tendency to bleed posed a difficult task for the surgeon.

Combined coronary artery and abdominal aortic surgery without cardiopulmonary bypass

To determine the effects of beating heart surgery on patients undergoing simultaneous coronary artery bypass grafting and abdominal aortic surgery, we performed such surgery on 20 patients (mean age, 64.55+/-796 SD years). Abdominal aortic disease was defined as an abdominal aortic aneurysm larger than 5 cm in diameter or as end-stage aortic occlusive disease. Hemodynamic measurements, inotropic requirements, and incidence of perioperative myocardial infarction and arrhythmias were recorded, as were subsystem clinical outcomes, length of intensive care unit and hospital stays, blood loss, and transfusion requirements. There was no incidence of death, perioperative myocardial infarction, stroke, or acute renal failure. The mean number of grafts per patient was 1.95+/-0.69. Only 4 minor postoperative complications were observed: three patients (15%) had evidence of supraventricular tachyarrhythmias, and 1 patient (5%) had chest infection that required a longer-than-average intubation period. Six patients (30%) required minimal-to-moderate inotropic support. The mean blood loss was 673+/-246.8 mL and transfusion requirements were low. The mean intensive care unit and hospital lengths of stay were 2. 12+/-0.33 days and 708+/-1.44 days, respectively. Clinical follow-up (mean, 10 months) showed all patients to be in New York Heart Association functional class I or II with no late cardiac or abdominal events. We conclude that simultaneous coronary artery bypass grafting and abdominal aortic surgery on the beating heart is safe and effective, and has a low perioperative clinical morbidity rate. To our knowledge, ours is the 1st report on this procedure. Larger studies with longer follow-up are needed.

Serum S-100 protein release and neuropsychologic outcome during coronary revascularization on the beating heart: a prospective randomized study

OBJECTIVES

Our purpose was to establish whether coronary revascularization on the beating heart without cardiopulmonary bypass is less harmful to the brain than conventional surgery with cardiopulmonary bypass as indicated by measures of cognitive function or by changes in serum concentrations of S-100 protein, a recognized biochemical marker of cerebral injury.

METHODS

We conducted a prospective randomized trial in which the assessors of the outcome measures were blind to the treatment received. Sixty patients without known neurologic abnormality, undergoing coronary revascularization, were prospectively randomized to 1 of 2 groups: (1) cardiopulmonary bypass (32 degrees C-34 degrees C) and cardioplegic arrest (on pump) with intermittent antegrade warm blood cardioplegia or (2) surgery on the beating heart (off pump). Neuropsychologic performance was assessed before and 12 weeks after the operation. Serum S-100 protein concentration was measured at intervals up to 24 hours after the operation.

RESULTS

The groups had similar preoperative characteristics. There were no deaths or major neurologic complications in either group, nor was there any difference between groups in the chosen index of neurologic deterioration. Serum S-100 protein concentrations were higher in the on-pump group at 30 minutes, but any such difference between groups had disappeared 4 hours later. The extent of the changes in S-100 protein was unrelated to the index of neuropsychologic deterioration.

CONCLUSIONS

The changes in S-100 protein concentration suggest that the brain and/or blood-brain barrier may be more adversely affected during coronary artery surgery with cardiopulmonary bypass than during surgery on the beating heart, but that this may not be reflected in detectable neuropsychologic deterioration at 12 weeks.

Effect of cardiopulmonary bypass on pulmonary gas exchange: a prospective randomized study

BACKGROUND

Conventional coronary artery bypass surgery is associated with postoperative pulmonary dysfunction. Inflammation due to cardiopulmonary bypass has been regarded as one of the main causes. In this study, we investigated the effect of coronary revascularization with or without cardiopulmonary bypass on pulmonary function.

METHODS

Fifty-two patients (40 male, mean age 60.1 years) were prospectively randomized to undergo coronary revascularization via median sternotomy, with or without normothermic cardiopulmonary bypass. Alveolar-arterial oxygen gradients were measured before and after induction of anesthesia, postoperatively in the intensive care unit during mechanical ventilation and 6 hours after tracheal extubation. The techniques of anesthesia and mechanical ventilation were standardized throughout.

RESULTS

Patient characteristics were similar in the two groups. The alveolar-arterial oxygen gradients increased progressively throughout the perioperative period, with no significant differences in the two groups at any time during the study.

CONCLUSIONS

Myocardial revascularization with or without cardiopulmonary bypass caused a similar degree of pulmonary dysfunction, as assessed by alveolar-arterial oxygen gradient. Our study suggests that the deterioration in pulmonary gas exchange associated with cardiac surgery is due to factors other than the use of cardiopulmonary bypass.

Economic outcome of off-pump coronary artery bypass surgery: a prospective randomized study

BACKGROUND

Emphasis on cost containment in coronary artery bypass surgery is becoming increasingly important in modern hospital management. The revival of interest in off-pump (beating heart) coronary artery bypass surgery may influence the economic outcome. This study examines these effects.

METHODS

Two hundred patients undergoing first-time coronary artery bypass surgery were prospectively randomized to either conventional cardiopulmonary bypass and cardioplegic arrest or off-pump surgery. Variable and fixed direct costs were obtained for each group during operative and postoperative care. The data were analyzed using parametric methods.

RESULTS

There was no difference between the groups with respect to pre- and intraoperative patient variables. Off-pump surgery was significantly less costly than conventional on-pump surgery with respect to operating materials, bed occupancy, and transfusion requirements (total mean cost per patient: on pump, $3,731.6+/-1,169.7 vs off-pump, $2,615.13+/-953.6; p < 0.001). Morbidity was significantly higher in the on-pump group, which was reflected in an increased cost.

CONCLUSIONS

Off-pump revascularization offers a safe, cost-effective alternative to conventional coronary revascularization with cardiopulmonary bypass and cardioplegic arrest.

Intraoperative localisation and management of coronary artery fistula using transesophageal echocardiography

Coronary artery fistula is a rare congenital malformation that can be complicated by intracardiac shunts, endocarditis, myocardial infarction, coronary aneurysm and sudden death. Clinical symptomatology depends upon the underlying anatomy and the size of the fistulous connection between the left or right side of the heart. We report the successful management of a giant right coronary artery with fistulization into the right atrium. Intraoperative transesophageal echocardiography with colour flow Doppler was used for precise location of the fistulous communication, selective demonstration of vessels feeding the fistula and documentation of abolition of fistulous flow all without the need for cardiopulmonary bypass. Furthermore the effect of shunt occlusion on regional wall motion was documented which facilitated the successful ligation of the fistula.

Integrated left anterior small thoracotomy and angioplasty for coronary artery revascularization

BACKGROUND

The minimal access surgical technique of a left anterior small thoracotomy (LAST) for coronary artery bypass grafting is now well established. This procedure however, does not allow multivessel revascularization. We present our early experience of an integrated approach using LAST and percutaneous transluminal coronary angioplasty (PTCA), either staged or simultaneous.

METHODS

Eighteen patients (14 men and 4 women), mean age 63 (range 35-87 years) were treated. Four patients underwent simultaneous LAST and PTCA revascularization. The remaining 14 patients were first treated with the LAST procedure, followed 1-3 days later by angioplasty. Angiographic assessment was carried out before PTCA and at 6 months after.

RESULTS

The 14 patients who underwent the staged procedure all had patent left internal mammary artery/left anterior descending coronary artery grafts. Angioplasty was performed on 21 vessels (10 stented) with good early angiographic results. All patients were extubated early, mean intensive care stay was 14.7 + 9.4 hours, mean hospital stay was 5 + 1.5 days. All patients were symptom free at 18 months follow-up.

CONCLUSIONS

Staged LAST and angioplasty is a safe and effective approach suitable for patients in whom there are contraindications to the use of extracorporeal circulation. The simultaneous approach is limited by the risk of bleeding associated with the use of anticoagulation when coronary stenting is required.

Evaluation of myocardial metabolism and function during beating heart coronary surgery

Coronary artery bypass surgery on the beating heart either via a left anterior small thoracotomy (LAST) or a median sternotomy is becoming increasing popular world-wide. Concern still remains about the potential for a temporary regional myocardial ischaemia associated with the stabilisation and occlusion of the coronary during construction of the anastomosis. This review summarises the results of a series of studies intended to evaluate the effect of beating heart coronary revascularization on myocardial function, myocardial tissue injury and clinical outcome.

Abdominal abscess: late complication after gastroepiploic coronary artery bypass grafting

The gastroepiploic artery is widely used an arterial conduit during coronary artery revascularisation surgery. We report an unusual complication of a 56-year-old man who developed a late intra-abdominal abscess extending into the mediastinum adjacent to the right ventricle more than 2 years after surgery. This was managed with percutaneous drainage and the patient made a full recovery. The case illustrates the potential problems associated with harvesting of this artery and the need for careful haemostasis.

On-pump versus off-pump coronary revascularization: evaluation of renal function

BACKGROUND

Coronary revascularization with cardiopulmonary bypass has the potential risk of renal dysfunction related to the nonphysiologic nature of cardiopulmonary bypass. Recently, there has been a revival of interest in performing myocardial revascularization on the beating heart and we investigated whether this prevents renal compromise.

METHODS

A prospective, randomized, controlled trial was performed in 50 patients (45 males, mean age 61+/-3.7 years) undergoing elective coronary artery bypass grafting. Patients were randomly assigned to conventional revascularization with cardiopulmonary bypass (on pump) or beating heart revascularization (off pump). Glomerular and tubular function were assessed up to 48 hours postoperatively.

RESULTS

There were no deaths, myocardial infarctions or acute renal failure in either group. Glomerular filtration as assessed by creatinine clearance and the urinary microalbumin/creatinine ratio was significantly worse in the on pump group (p < 0.0004 and 0.0083, respectively). Renal tubular function was also impaired in the on pump group as assessed by increased N-acetyl glucosaminidase activity (p < 0.0272).

CONCLUSIONS

These results suggest that off pump coronary revascularization offers a superior renal protection when compared with conventional coronary revascularization with cardiopulmonary bypass and cardioplegic arrest in first time coronary bypass patients.

Beating versus arrested heart revascularization: evaluation of myocardial function in a prospective randomized study

OBJECTIVE

Conventional coronary artery bypass grafting (CABG) is both safe and effective. Nevertheless, the use of cardiopulmonary bypass (CPB) and cardioplegic arrest are associated with several adverse effects. Over the last 2 years there has been a revival of interest in performing CABG on the beating heart. In this prospective randomized study we evaluated the efficacy and safety of on and off pump coronary revascularization on myocardial function.

METHODS

Eighty patients (65 males, mean age 61+/-9.7 years) undergoing first time CABG were prospectively randomized to: (i) conventional revascularization with CPB at normothermia and cardioplegic arrest with intermittent warm blood cardioplegia (on pump) or (ii) beating heart revascularization (off pump). Troponin I (Tn I) release was serially measured as a specific marker of myocardial damage. Haemodynamic measurements as well as inotropic requirement, incidence of arrhythmia and postoperative myocardial infarction were also recorded.

RESULTS

There were no significant differences between the two groups in terms of age, sex, extent of disease, left ventricular function and number of grafts. There were no deaths or intraoperative myocardial infarctions in either group. Tn I release was constantly lower in the off pump group and this was significant at 1, 4, 12 and 24 h postoperatively. Furthermore, in this group there was a significantly reduced incidence of arrhythmias. Inotropic requirements were less in the off pump group but this did not reach statistical significance.

CONCLUSION

These results suggest that off pump coronary revascularization is a safe and effective strategy for myocardial revascularization. Myocardial injury as assessed by Tn I release is also reduced when compared with conventional coronary revascularization with CPB and cardioplegic arrest.

Warm blood cardioplegia reduces the fall in the intracellular concentration of taurine in the ischaemic/reperfused heart of patients undergoing aortic valve surgery

The effect of cold and warm intermittent antegrade blood cardioplegia, on the intracellular concentration of taurine in the ischaemic/reperfused heart of patients undergoing aortic valve surgery, was investigated. Intracellular taurine was measured in ventricular biopsies taken before institution of cardiopulmonary bypass, at the end of 30 min of ischaemic arrest and 20 min after reperfusion. There was no significant change in the intracellular concentration of taurine in ventricular biopsies taken after the period of myocardial ischaemia in the two groups of patients (from 10.1 +/- 1.0 to 9.6 +/- 0.9 mumol/g wet weight for cold and from 9.3 +/- 1.3 to 10.0 +/- 1.3 mumol/g wet weight for warm cardioplegia, respectively). Upon reperfusion however, there was a fall in taurine in both groups but was only significant (P < 0.05) in the group receiving cold blood cardioplegia (6.9 +/- 0.8 mumol/g wet weight after cold blood cardioplegia versus 8.0 +/- 0.8 mumol/g wet weight following warm blood cardioplegia). Like taurine, there were no significant changes in the intracellular concentration of ATP after ischaemia in the two groups of patients (from 3.2 +/- 0.32 to 2.95 +/- 0.43 mumol/g wet weight for cold and from 2.75 +/- 0.17 to 2.62 +/- 0.21 mumol/g wet weight for warm cardioplegia, respectively). However upon reperfusion there was a significant fall in ATP in both groups with the extent of the fall being less in the group receiving warm cardioplegia (1.79 +/- 0.19 mumol/g wet weight for cold and 1.98 +/- 0.27 mumol/g wet weight for warm cardioplegia, respectively). This work shows that reperfusion following ischaemic arrest with warm cardioplegia reduces the fall in tissue taurine seen after arrest with cold cardioplegia. Accumulation of intracellular sodium provoked by hypothermia and a fall in ATP, may be responsible for the fall in taurine by way of activating the sodium/taurine symport to efflux taurine.

Bioprosthetic replacement after bioprosthesis failure: a hazardous choice?

BACKGROUND

Following bioprosthetic failure, replacement is usually done with mechanical valves to avoid repeated reoperations.

METHODS

From 1986 to 1996 we operated on 130 patients with bioprosthetic failure, implanting a new bioprosthesis; this group included patients with contraindication to anticoagulation, tricuspid replacement, and specific patient requests. Mean age was 63+/-8 years.

RESULTS

The perioperative mortality was 13.8%. At 10 year follow-up the actuarial estimate of survival was 77.4%+/-6.6%. Freedom from structural valve deterioration was estimated at 81.8%+/-6.3%. Freedom from a third operation was estimated at 85.5%+/-5.2%. No patient was permanently anticoagulated. Freedom from thromboembolism was estimated at 91.5%+/-4%, and there were no hemorrhages. Freedom from cardiac-related deaths was estimated at 85.7%+/-5%.

CONCLUSIONS

This group of patients received the first valve between 1976 and 1986; the range of the cumulative follow-up reaches 20 years, and the extended survival compares favorably with survival of mechanical valves.

The end of the cold era: from intermittent cold to intermittent warm blood cardioplegia

BACKGROUND

A major reduction in the energy demand of the myocardium results from the electromechanical arrest, and cooling contributes to a lesser degree to this reduction. It is from this assumption that strategies of myocardial protection, utilizing warm blood cardioplegic induction, followed by cold cardioplegia with terminal warm reperfusion before removal of the aortic cross clamp, became established as optimal myocardial protection. Continuous normothermic perfusion 'closed the loop' by avoiding myocardial ischemia and linking warm induction and terminal reperfusion. A series of laboratory and clinical data confirmed the benefits of warm heart surgery on myocardial function and metabolism. The disadvantages of continuous warm blood cardioplegia including disturbance of the operative field, led surgeons to administer warm hyperkalaemic blood intermittently as a new cardioplegic strategy.

METHODS

This review examines the laboratory and clinical data with reference to the intermittent warm blood cardioplegia, to establish its experimental basis and place in clinical practice.

CONCLUSIONS

Experimental observation and clinical application have established intermittent warm blood cardioplegia as a practical, effective and cheap myocardial protection technique, particularly with reference to coronary artery surgery.

Metabolic differences between hearts of patients with aortic valve disease and hearts of patients with ischaemic disease

The hypertrophic hearts of patients with aortic valve disease are likely to have metabolic demands different from hearts with ischaemic disease. In this study we measured the myocardial concentration of ATP, ADP, lactate and 16 different amino acids in left ventricular biopsies collected from patients with aortic valve disease and from patients with ischaemic heart disease. Compared to hearts with ischaemic disease, hypertrophic hearts had significantly higher concentrations of ATP, but lower concentrations of lactate, branched-chain amino acids and alanine. These differences have important implications for energy metabolism and protein turnover in the two pathologies.

Intermittent warm blood cardioplegia preserves myocardial beta-adrenergic receptor function

BACKGROUND

Left ventricular dysfunction is frequently observed in patients after hypothermic cardioplegic arrest, and often inotropic intervention is necessary for patients to be successfully weaned from cardiopulmonary bypass (CPB). A myocardial beta-adrenergic receptor (beta AR) desensitization has been noted to occur after hypothermic CPB in patients undergoing coronary artery bypass grafting. This randomized study was undertaken to determine the effect of cardioplegic solution temperature on cardiac beta ARs.

METHODS

Two groups of patients (20 patients in each) scheduled for elective coronary artery bypass grafting underwent CPB with either intermittent warm or cold blood cardioplegia. The density of the beta ARs, the proportion of beta 1- to beta 2-adrenergic receptors, and the beta AR coupling capacity to adenylate cyclase were determined in specimens of the right atrial tissue at baseline, during CPB, and after discontinuation of CPB. Plasma concentrations of catecholamines were also measured in both arterial and coronary sinus samples.

RESULTS

In both cardioplegia groups, no significant modification in either the beta AR density or the proportion of beta 1- to beta 2-adrenergic receptors was detected. However, a significant decrease in adenylate cyclase activity after stimulation with isoproterenol was observed in the cold blood cardioplegia group during CPB (p < 0.01) and 30 minutes after its discontinuation (p < 0.05). Moreover, a significant decrease in adenylate cyclase activity during CPB was detected in this group after stimulation with sodium fluoride (p < 0.05), but this pattern was found to be completely reversed by 30 minutes after discontinuation of CPB. No modification in the basal or stimulated adenylate cyclase activity was observed in the warm blood cardioplegia group during or after CPB.

CONCLUSIONS

Our results confirm the finding from previous studies of a cardiac beta AR desensitization after hypothermic cardioplegic arrest, and provide evidence of the advantages of intermittent warm blood cardioplegia in preserving the autonomic sympathetic function of the heart.

Aortic valve replacement through a minimally invasive approach

Minimally invasive cardiac surgery is rapidly gaining interest because of fast recovery, reduced morbidity, shorter hospital stay, lower costs, and better cosmetic results. Aortic valve surgery can be performed through a small (10- to 12-cm) transverse sternal incision, and femoro-femoral cannulation is used for cardiopulmonary bypass. Exposure of the ascending aorta is satisfactory. From 1 March through 30 September 1996, 7 patients underwent aortic valve replacement through this approach. The mean age of the 5 women and 2 men was 58.8 years. We used this technique mainly in patients with chronic obstructive pulmonary disease, diabetes, or obesity, in the absence of coronary artery disease. There was no mortality, nor was there reoperation for bleeding, stroke, or wound infection. All patients were extubated after 2 hours in intensive care and were discharged on the 4th postoperative day. Additional cases are needed to properly assess the correct indication and surgical technique.

Complement and neutrophil activation during cardiopulmonary bypass: a randomized comparison of hypothermic and normothermic circulation

OBJECTIVE

Activation of both complement and neutrophils has been demonstrated to be involved in many pathological reactions following cardiopulmonary bypass (CPB). The aim of the present study is to evaluate the effect of normothermic and hypothermic CPB on both complement and neutrophil activation.

METHODS

Two groups of patients (n = 20 each) scheduled for elective coronary artery bypass grafting, underwent CPB with intermittent warm or cold blood cardioplegia. Plasma concentration of C3a, C5a and C5b-9, as well as nitro-blu tetrazolium (NBT) scores of circulating neutrophils were measured before anesthesia, 10 and 30 min after the beginning of CPB, and 8, 16 and 24 h, postoperatively.

RESULTS

In both groups, CPB determined a significant complement activation, evidenced as a significant increase in plasma concentration of C3a, C5a and C5b-9. This in turn triggered the neutrophil activation, documented as a significant increase of NTB scores in circulating neutrophils at the end of CPB and in the early postoperative period. Interestingly, in the warm group the extent of both complement and neutrophil activation was significantly higher compared with the cold group during the whole sampling period.

CONCLUSION

In conclusion, our study clearly demonstrates that warm CPB is associated with an increased ability to activate complement and neutrophils in patients undergoing coronary surgery.

[Eco-epidemiological study of Phlebotomus perniciosus in foci of visceral leishmaniasis in Campania]

An entomological survey was carried out during the sandfly season (June-October) of 1993 in three of the main visceral leishmaniasis (VL) foci of the Campania region of Italy. During the period 1989-1993, 39 VL cases were recorded in the three foci: 19 in Maddaloni, 14 in Ercolano and 6 in Ischia. For each focus, collecting stations representative of sandfly habitats (domestic, peri-domestic and sylvatic) located in urban, peri-urban and rural areas were selected for the sandfly investigation. Three monthly captures by means of sticky traps (20 x 20 cm) were carried out in each station. A total of 2,773 sandfly specimens were caught and identified as belonging to 4 species: Phlebotomus perniciosus (66.2%). P. mascittii (0.4%). P. papatasi (0.2%) and Sergentomyia minuta (33.2%). P. perniciosus, the proven vector of VL in Italy, showed the highest prevalence in all foci studied, Maddaloni (61.0%). Ercolano (62.5%) and Ischia (88.2%); the absolute density of the species (number of specimens/m2 of sticky trap) was not so high in all areas and habitats sampled, the values observed being between 0.14 and 22.05/m2. The relationship between the eco-epidemiological aspects and the distribution of P. perniciosus in the foci investigated is discussed.

Carotid endarterectomy and myocardial revascularization. A single stage procedure

Carotid endarterectomy (CEA) and myocardial revascularization can be performed in a single procedure, performing CEA before or during cardio-pulmonary by-pass (CPB), or using a double stage approach. Over a 4 year period, 17 patients underwent CEA and coronary artery by-pass (CAB) with a single stage procedure. Fourteen patients (82.3%) were male, 3 (17.6%) were female. The mean age was 66.3 +/- 7.07. One patient (5.8%) had a previous neurological event (stroke); 5 patients (29.4%) had a previous transient ischemic attacks (TIA). The indications for the combined operations were CAD associated to unilateral internal carotid stenosis greater than 70% or 50% when symptomatic. In all patients CEA was performed after median sternotomy and heparinization, during CPB, with moderate hypotermia (30%C), performing CEA successively. One patient (5.8%) died of acute heart failure secondary to mediastinits. Minor neurological complications were present in 2 patients (11.7%) with signs of cerebral oedema. Myocardial infarction and late neurological deficit did not occur in any patient. We conclude that it is important, in the preoperative assessment of every patients with CAD, the screening for concomitant carotid vascular diseases, in order to avoid neurological complications during CPB, treating the two different diseases with a single stage approach, if carotid stenosis is greater than 70% or greater than 50% when symptomatic.

Protection by coenzyme Q10 from myocardial reperfusion injury during coronary artery bypass grafting

To evaluate the effect of coenzyme Q10 in reducing postoperative cardiac complications after ischemia and reperfusion, we randomly divided 40 patients undergoing elective coronary artery bypass into two groups: patients in group 1 received coenzyme Q10 (150 mg/day) for 7 days before operation, and those in group 2 were the control group. Concentrations of thiobarbituric acid-reactive substances (malondialdehyde), conjugated dienes, and cardiac isoenzymes of creatine kinase were measured in samples from both arterial and coronary sinus sites. Serial sampling was performed 5 minutes after heparin administration, at 10 and 30 minutes during cardiopulmonary bypass, 15 and 30 minutes after aortic cross-clamp removal, and 5 minutes after protamine administration. The concentrations of malondialdehyde, conjugated dienes, and creatine kinase in group 1 were significantly lower than those in group 2. The decrease in plasma malondialdehyde concentrations correlated positively with the decrease in creatine kinase levels in the coronary sinus. The treatment group showed a significantly lower incidence of ventricular arrhythmias during the recovery period than did the control group (p < 0.05). Although the percentage of patients requiring inotropic agents was not significantly different between the two groups, the mean dosage of dopamine required to maintain stable hemodynamics was significantly lower in patients of group 1 than in those of group 2 (p < 0.01). Our findings suggest that pretreatment with coenzyme Q10 may play a protective role during routine bypass grafting by attenuating the degree of peroxidative damage.

Cardiovascular monitoring of drug-resistant lymphoma patients treated with epoch chemotherapy plus high-dose verapamil in continuous-infusion

High dose Verapamil (VP) infusion has been incorporated into cytotoxic chemotherapy in order to circumvent tumor cell drug-resistance. We have evaluated the cardiovascular side-effects produced by high dose VP associated to EPOCH chemotherapy in 12 patients with chemorefractory lymphoma. Continuous monitoring of right ventricular and pulmonary pressure and cardiac index was performed in three patients by a Swan-Ganz catheter. A slight reduction in cardiac index was observed 6 h after the beginning of VP infusion and was followed by spontaneous recovery within 12 h. First degree atrioventricular (AV) block was detected in 6/12 patients. Premature Ventricular Beats (PVB) occurred in one patient, and promptly disappeared after xylocaine administration. All patients experienced mild and transient hypotension, while severe hypotension was observed only in 1 patient, who promptly recovered when VP administration was discontinued. Hypokalemia was detected in 6 patients possibly as a consequence of transient activation of the renin-angiotensin system.

C-ets-1 protooncogene expression alters the growth properties of immortalized rat fibroblasts

Ets family genes have been cloned and characterized from a variety of species ranging from human to Drosophila. The ets proteins encode transcription factors that activate transcription via specific binding to GGAA core sequence present in various promoter/enhancers. To investigate the role of ets protooncogene expression on the growth properties of rat embryo fibroblasts (REF), we constructed and introduced ets expression vectors into primary, as well as immortalized REF cells. The transfected cells contained multiple copies of the vector DNA, and the Northern blot analysis demonstrated overexpression of the c-ets-1-specific mRNA. Although the expression of the ets genes was unable to immortalize primary rat embryo fibroblasts, the expression of ets-1 in REF-1 cells enabled their growth in serum-free medium and effected tumorigenic activity in nude mice.

The Drosophila ets-2 gene: molecular structure, chromosomal localization, and developmental expression

The cellular homologs of the ets gene from the avian erythroblastosis retrovirus E26 have been studied in chickens, humans, mice, and cats. In this report a further evolutionary step is taken by isolating and characterizing a Drosophila ets-related genomic clone. Sequence analysis of this clone has shown it to contain the 3' end of the v-ets gene, called ets-2, corresponding to the last two exons of chicken ets. The predicted amino acid sequence was found to have over 90% homology when compared to that of v-ets. This is the highest level of conservation observed for any previously characterized Drosophila oncogene homolog. Expression of the ets-2 gene occurs throughout development, but is highest during the embryonic and pupal stages. By in situ hybridization, the ets-2 chromosomal position was determined to be 58A/B which corresponds to no known phenotypic mutant. As this is a highly conserved gene, the Drosophila model system should prove useful for the determination of the ets gene function.

Temporal and tissue-specific expression of mouse ets genes

The expression of ets genes has been studied in mouse tissues and regenerating murine liver, an in vivo model for cell proliferation. Our results indicate that the ets-1 and ets-2 loci are transcriptionally active; the ets-2 locus encodes a major mRNA (3.5 kilobases) and is expressed in most of the tissues examined, whereas the ets-1 locus encodes a major 5.3-kilobase and minor 4.0-, 2.5-, and 2.2-kilobase RNA species and is expressed at a high level in thymus; both ets-1 and ets-2 mRNA are abundant in young proliferating tissues and are greatly reduced in terminally differentiated tissues, except thymus; compensatory growth of liver induces ets-2 mRNA before DNA synthesis, but after fos and myc induction; and ets-2 mRNA, but not ets-1 mRNA, is stabilized in the presence of cycloheximide during hepatic regeneration. These results suggest that ets-2 gene expression is intrinsically linked with cell proliferation. Thus, ets-2 expression follows a pattern similar to other members of the nuclear oncogene family. During hepatic regeneration, the ets-1 and ets-2 loci are subject to differential regulation.

Production of oncogene-specific proteins and human T-cell leukemia (lymphotropic) retrovirus (HTLV-I) envelope protein in bacteria and its potential for use in human cancers and seroepidemiological surveys

The oncogenes coding for the Harvey murine sarcoma virus p21ras protein as well as those coding for myc, myb, and mht products were fused to the amino-terminal portion of the bacteriophage lambda cII gene on the expression vector pJL6. In addition two regions of the gene for the human T-cell leukemia virus subgroup I (HTLV-I) envelope were expressed in our bacterial system. Each of 11 human sera tested that had been shown to contain antibodies to HTLV-I or -II by an enzyme-linked immunosorbent assay recognized the bacterially synthesized envelope proteins. No reaction was detected when 17 control sera were tested. This system will be useful for large-scale seroepidemiological surveys for HTLV-I and related human retroviruses. The other oncogene products expressed in our bacterial vector system also demonstrated specific immunoreactivities. In addition to this feature the bacterial ras protein was seen to bind guanosine diphosphate and was capable of autophosphorylation. Taken together these data suggest that the proteins produced with high efficiency by the bacterial expression system can be immunologically recognized as antigens and can in part perform some of their associated biochemical functions.

Two oncogenes in avian carcinoma virus MH2: myc and mht

The 5.2-kilobase (kb) RNA genome of avian carcinoma virus MH2 has the genetic structure 5' - delta gag (0.2 kb)-mht (1.2 kb)-myc (1.4 kb)-c(0.4 kb)-poly (A) (0.2 kb)-3'. delta gag is a partial retroviral core protein, mht and myc are cell-derived MH2-specific sequences, and c is the 3'-terminal retroviral vector sequence. the following results were obtained from the complete nucleotide sequences of the mht and myc genes in MH2. (i) delta gag-mht forms a hybrid gene with a contiguous reading frame of 2682 nucleotides that terminates with a stop codon near the 3' end of the mht gene. The 3' 969 nucleotides of mht up to the stop codon are 80% sequence related to the onc-specific raf sequence of murine sarcoma virus 3611 (MSV 3611) (94% homologous at the deduced amino acid level). (ii) The myc coding region in MH2 is preceded by 181 nucleotides derived from the intron immediately upstream from the second exon of the chicken cellular proto-myc gene, followed by an RNA splice acceptor site shared with the proto-myc gene, followed by an RNA splice acceptor site shared with the proto-myc, beyond which it is colinear up to a 3'-termination codon and 40 noncoding nucleotides with the myc sequences of avian retrovirus MC29 and chicken proto-myc. Thus, myc forms, together with a 5' retroviral exon, a second MH2-specific gene. It is concluded that MH2 contains two genes with oncogenic potential, the delta gag-mht gene, which is closely related to the delta gag-raf transforming gene of MSV 3611, and the myc gene, which is related to the transforming gene of MC29. Furthermore, it may be concluded that the cellular proto-onc genes, which on sequence transduction become viral onc genes, are a small group because among the 19 known onc sequences, 5 are shared by different taxonomic groups of viruses of which the mht/raf homology is the closest so far.

In vitro methylation of specific regions of the cloned Moloney sarcoma virus genome inhibits its transforming activity

The transforming activity of cloned Moloney sarcoma virus (MSV) proviral DNA was inhibited by in vitro methylation of the DNA at cytosine residues, using HpaII and HhaI methylases before transfection into NIH 3T3 cells. The inhibition of transforming activity due to HpaII methylation was reversed by treatment of the transfected cells with 5-azacytidine, a specific inhibitor of methylation. Analysis of the genomic DNA from the transformed cells which resulted from the transfection of methylated MSV DNA revealed that the integrated MSV proviral DNA was sensitive to HpaII digestion in all cell lines examined, suggesting that loss of methyl groups was necessary for transformation. When cells were infected with Moloney murine leukemia virus at various times after transfection with methylated MSV DNA, the amount of transforming virus produced indicated that the loss of methyl groups occurred within 24 h. Methylation of MSV DNA at HhaI sites was as inhibitory to transforming activity as methylation at HpaII sites. In addition, methylation at both HpaII and HhaI sites did not further reduce the transforming activity of the DNA. These results suggested that; whereas methylation of specific sites on the provirus may not be essential for inhibiting the transforming activity of MSV DNA, methylation of specific regions may be necessary. Thus, by cotransfection of plasmids containing only specific regions of the MSV provirus, it was determined that methylation of the v-mos gene was more inhibitory to transformation than methylation of the viral long terminal repeat.