Endovascular versus open repair of ruptured abdominal aortic aneurysm

INTRODUCTION

Endovascular aneurysm repair (EVAR) is a comparatively less invasive technique than open repair (OR). Debate remains with regard to the benefit of EVAR for patients with ruptured abdominal aortic aneurysm (RAAA). We sought to evaluate and report outcomes of EVAR for RAAA in an Irish tertiary vascular referral centre.

METHODS

Patients undergoing emergency surgery for ruptured or symptomatic AAA were identified from theatre logbooks and HIPE database. Retrospective chart review was undertaken. Data were exported to IBM SPSS version 21 for statistical analysis with p < 0.05 considered significant.

RESULTS

A total of 41 patients underwent surgery for RAAA. The mean age was 74 years old with a range from 55 to 89 years. The majority (n = 25, 61%) were baseline American Society of Anaesthesiology (ASA) grade 3-4. Of these 56% underwent EVAR with the remaining 44% repaired open. Mortality rate in those undergoing emergency EVAR was 34.8%, compared with 38.9% in those undergoing open surgery. This difference was not statistically significant. The mean overall length of stay was 13 days. With regard to prognostic indicators of patient outcome, increasing patient age was noted to be significantly associated with increased mortality (p = 0.013), as was increased ASA score at time of surgery (p = 0.029).

CONCLUSIONS

Mortality rates in those undergoing EVAR for RAAA are comparable with those undergoing open repair. Increasing age and ASA score are significant predictors of mortality in patients with RAAA undergoing intervention.

The Use of Arteriovenous Fistulae as an Adjunct to Peripheral Arterial Bypass: A Systematic Review and Meta-analysis

BACKGROUND

Peripheral arterial bypass is an effective procedure for the management of patients with critical limb ischaemia. However, it is commonly associated with high rates of graft occlusion and subsequent limb loss. This is particularly apparent when the distal anastomosis is to the below-knee arterial segment. A number of studies have suggested that an arteriovenous fistula (AVF) sited at the distal anastomosis may reduce afterload, improve graft patency, and boost subsequent limb salvage. The aim of this study was to assess the effects of adjuvant AVF on the outcomes of peripheral arterial bypass.

METHODS

The following databases were searched up to May 2015: Medline through Pubmed; the Cochrane Library; EMBASE; and reference lists of articles.

STUDY ELIGIBILITY

All randomised controlled and observational studies that assessed the role of AVF as an adjunct to peripheral arterial bypass were included. Studies were required to include at least one pre-defined outcome. Data were extracted and assessed by two reviewers with any disagreements adjudicated on by the senior author. Pooled risk ratios were calculated using a random effects model. Additional subgroup analyses were performed.

RESULTS

Two randomised controlled trials and seven retrospective cohort studies comprising 966 participants were included. Pooled standardized data showed no difference in primary graft patency (pooled RR = 1.25, 95% CI 0.73-2.16), secondary patency (pooled RR = 1.16, 95% CI 0.82-1.66), or limb salvage at 12-months (pooled RR = 1.13, 95% CI 0.80-1.60) for the peripheral bypass with AVF group compared with peripheral bypass alone. Subgroup analysis indicated a reduction in reintervention rates associated with AVF when performed in conjunction with a synthetic graft (pooled RR = 0.55, 95% CI 0.30-0.98).

CONCLUSION

Although adjuvant AVF is not associated with additional operative complication there is little evidence to support its use. The evidence assessing its merits is weakened by small, retrospective studies with heterogeneous cohorts.

Prosthodontic rehabilitation of hypophosphatasia using dental implants: a review of the literature and two case reports

There are reports in the literature of the various dental features of hypophosphatasia, especially where it affects the deciduous dentition. The descriptions include both the manifestations of the disorder and the subsequent patterns of tooth loss. There are fewer descriptions of the effects of hypophosphatasia on the permanent dentition and little information on the subsequent prosthodontic management of these patients, particularly in relation to the use of dental implants. The aim of this paper was to review the literature on the dental effects of hypophosphatasia, present two cases and describe how one of those patients, a young adult, was successfully rehabilitated using dental implants. That latter patient's pattern of tooth loss as well as some histological and scanning electron microscopic findings of root cementum from the other case is also described.

Differences in displayed pump flow compared to measured flow under varying conditions during simulated cardiopulmonary bypass

Errors in blood flow delivery due to shunting have been reported to reduce flow by, potentially, up to 40-83% during cardiopulmonary bypass. The standard roller-pump measures revolutions per minute and a calibration factor for different tubing sizes calculates and displays flow accordingly. We compared displayed roller-pump flow with ultrasonically measured flow to ascertain if measured flow correlated with the heart-lung pump flow reading. Comparison of flows was measured under varying conditions of pump run duration, temperature, viscosity, varying arterial/venous loops, occlusiveness, outlet pressure, use of silicone or polyvinyl chloride (PVC) in the roller race, different tubing diameters, and use of a venous vacuum-drainage device.

How much heparin do we really need to go on pump? A rethink of current practices

OBJECTIVES

Patients undergoing myocardial revascularisation using extracorporeal circulation require heparin anticoagulation. We aimed to evaluate the effect of reducing heparin dosage on target activated clotting time (ACT) and postoperative blood loss.

METHODS

In a prospective randomised trial, 195 patients undergoing isolated primary CABG were randomised into four groups A, B, C, and D receiving an initial heparin dosage of 100, 200, 250 and 300 iu/kg, respectively. Extra incremental heparin (50 iu/kg) was added if required to achieve a target ACT of 480 s before initiating cardiopulmonary bypass. Postoperative blood loss was measured from the time of heparin reversal to drain removal 24h later.

RESULTS

Target ACT was achieved in 0, 63, 68.3 and 82.4% of patients in groups A, B, C and D, respectively, after the initial dose of heparin. In group B, of those not achieving target act a single increment of heparin was sufficient to achieve target ACT in further 18.6%. The mean ACT after the initial dose in groups B, C and D was 482.9, 519 and 588 s, respectively (P<0.05). Postoperative blood loss in millilitre per kilogram was directly proportional to preoperative heparin dose.

CONCLUSIONS

Patients receiving lower dose of heparin has lower postoperative blood loss. Of those achieving the target ACT, group B was significantly the closest to the target ACT. A starting dose of 200 iu/kg of heparin and if necessary one 50 iu/kg increment achieved target ACT in 81.5% of patients. The added benefit of significant drop in postoperative blood loss is evident.

A new specifically designed forceps for chest drain insertion

Insertion of a chest drain can be associated with serious complications. It is recommended that the drain is inserted with blunt dissection through the chest wall but there is no specific instrument to aid this task. We describe a new reusable forceps that has been designed specifically to facilitate the insertion of chest drains.A feasibility study of its use in patients who required a chest drain as part of elective cardiothoracic operations was undertaken. The primary end-point was successful and accurate placement of the drain. The operators also completed a questionnaire rating defined aspects of the procedure. The new instrument was used to insert the chest drain in 30 patients (19 male, 11 female; median age 61.5 years (range 16-81 years)). The drain was inserted successfully without the trocar in all cases and there were no complications. Use of the instrument rated as significantly easier relative to experience of previous techniques in all specified aspects. The new device can be used to insert intercostal chest drains safely and efficiently without using the trocar or any other instrument.

Electrical failure during cardiopulmonary bypass: an evaluation of incidence, causes, management and guidelines for preventative measures

The incidence of electrical failure during cardiopulmonary bypass (CPB) has been reported to occur in approximately 1 per 1000 cases. While the resultant morbidity and mortality is low, electrical failure is a life-threatening scenario. We report three major electrical failures during CPB in a patient population of 3500 over a 15-year period. These cases involved mains failure and generator shut down, mains failure and generator power surge, and failure of the uninterruptable power supply (UPS), which caused protected sockets to shut down. Protocols for preventative maintenance, necessary equipment, battery backup and guidelines for the successful management of such accidents during CPB are discussed.

The effects of venous cannulation technique and cardioplegia type on plasma potassium concentration and arterial blood pressure during cardiopulmonary bypass

The cannulation method and cardioplegia solution used during cardiopulmonary bypass (CPB) may both influence plasma potassium concentrations ([K+]) and mean arterial blood pressure (MAP). Bi-caval or right atrial cannulation methods are routinely used in conjunction with crystalloid or blood cardioplegia. We investigated the influence of cannulation method and cardioplegia solutions on plasma [K+] and MAP during cardiopulmonary bypass. Sixty consecutive patients undergoing elective coronary artery bypass grafting (CABG) using CPB were studied. They were randomly divided into three groups of 20 patients. Patients in Group A underwent bi-caval venous cannulation and received crystalloid cardioplegia. Group B patients underwent right atrial cannulation and received crystalloid cardioplegia. Group C patients underwent right atrial cannulation and received blood cardioplegia. In each case. cardioplegia was administered antegrade via the aortic root. Plasma [K+], MAP. and hemoglobin concentration (Hb) were measured over an 8-min period following cardioplegia administration (pilot studies indicated pressure changes occuring post cardioplegia administration up to this time). The combination of bi-caval cannulation and crystalloid cardioplegia (Group A) was associated with the least increase in plasma [K+] and no decrease in MAP. The maximum [K+] for this Group was 4.2 mmol/L (4.6% increase). The minimum mean pressure was 57 mmHg (13.6% increase). Both right atrial cannulation groups (B and C) showed a large rise in plasma [K+] and a decrease in MAP. Group B maximum [K+] was 5.2 mmol/L (27.5% increase). Group C was also 5.2 mmol/L (26.0% increase). Group C showed the largest pressure decrease, the minimum mean pressure was 45 mmHg (21.3% decrease). The Group B minimum mean pressure was 45 mmHg (8.7% decrease). Our results show that patients undergoing CPB operations who are deemed to be at increased risk of suffering adverse effects from hypotensive episodes may benefit from bicaval cannulation and caval snaring, in preference to right atrial cannulation. Crystalloid cardioplegia may be preferable to blood cardioplegia in these cases to maintain the MAP.

Contemporary developments in the utilization of metal-ceramic restorations: a review

Numerous porcelain systems and techniques are currently available for utilization in full-coverage anterior crown restorations. Significant improvements have been made in the placement of margins and the reduction of the metal framework in order to enhance the optical effects (e.g., illumination, warmth, and vitality) of these porcelain systems. This article presents several recent developments in the fabrication of metal-ceramic crown restorations, and demonstrates the use of these principles in the aesthetic oral rehabilitation.

Long-term clinical outcome following coronary artery bypass grafting for isolated stenosis of the left anterior descending coronary artery

AIMS

To detail the clinical and angiographic profile, and long-term outcome in consecutive patients with isolated stenosis of the left anterior descending coronary artery undergoing bypass surgery.

METHODS

A retrospective study of all patients (n = 301) (January 1984-December 1990) and undergoing coronary artery bypass grafting for isolated left anterior descending disease, in the Irish Republic, was performed. Survival was compared with that of an exact age- and gender-matched cohort.

RESULTS

Mean age was 53 (+/- 9.3) years. There were 238 (79%) males. In 241 (80%) patients an internal thoracic arterial bypass graft was used. Operative mortality was 1.3%. Of the 280 (93%) patients alive (16 cardiac deaths) at 7.1 (+/- 1.9) years, 105 (35%) had angina, 26 (9%) suffered an interval myocardial infarction, and repeat revascularization was required on 29 (10%). Female gender (P = 0.002), pre-operative myocardial infarction (P = 0.02), significant diagonal disease (P = 0.04) and postoperative myocardial infarction (P = 0.0001) were independently associated with survival. Females were more likely to develop congestive cardiac failure (P = 0.01) or postoperative angina (P = 0.03) than their male counterparts.

CONCLUSIONS

Survivorship (97%) and event-free survival (96%) at 5 years following coronary artery bypass grafting for isolated left anterior descending coronary artery disease is excellent and equivalent to an age-matched and gender-matched cohort.

Coronary artery bypass surgery in the diabetic patient

Coronary artery and peripheral occlusive arterial disease frequently complicate diabetes mellitus, with death due to atherosclerotic coronary artery disease being three times more likely in diabetic compared to non-diabetic patients. The profile of 32 diabetic patients and 32 matched controls who underwent coronary artery bypass (CABG) is studied and their early and late postoperative outcomes are described. The mean age was 61 +/- 1 year in both groups. The diabetic group comprised 26 non-insulin dependent and 6 insulin dependent diabetics, who had a mean duration of diabetes of 8.5 years (range 2 months--35 years). The median number of grafts per patient performed in the diabetic group and the control group was 3.5 and 3 respectively. There was no mortality in the series, however considerably greater wound morbidity rates were encountered in the diabetic group when compared to matched controls. One renal transplant patient in the diabetic group suffered irreversible acute tubular necrosis and became dialysis dependent post-operatively. Longterm follow-up showed no longterm mortality in either group, with full relief of angina achieved in 75% of diabetic patients compared with 87.5% of matched controls. In addition diabetic patients suffered greater longterm cardiac morbidity than the control group (21.8% versus 12.5%). The results of this study suggest that CABG is a safe operation for the diabetic patient. Diabetic patients receive satisfactory symptomatic relief of angina, but suffer increased perioperative wound complications and greater incidence of longterm cardiac morbidity.

Prostacyclin and thromboxane levels in pleural space fluid during cardiopulmonary bypass

Prostaglandins exhibit a variety of cardiovascular actions that may affect the hemodynamic recovery of the ischemic myocardium after cardiopulmonary bypass. We have observed a decrease in the mean arterial pressure on autotransfusion of the accumulated pleural cavity fluid during operation. One aim of this study was to determine the concentrations of prostacyclin and thromboxane A2 in the pleural cavity fluid by measuring their stable metabolites, 6-keto-PGF1 alpha and thromboxane B2, respectively, in 8 consecutive patients undergoing myocardial revascularization, and to compare them with the arterial levels. A second aim was to quantify the hemodynamic effect of the pleural cavity fluid during operation. The concentration of 6-keto-PGF1 alpha in the pleural cavity fluid was significantly higher than the arterial concentration (mean, 21.6 +/- 18.2 ng/mL; p < 0.01). The concentration of thromboxane B2 was also raised compared with the arterial concentration (mean, 3.62 +/- 5.96 ng/mL; p < 0.2). The percentage fall in the mean arterial pressure was 29.7% +/- 8.86% (p < 0.02), which was transient and lasted 1 to 3.5 minutes. The hemoglobin concentration, potassium level, and pH were also measured. This study shows that the pleural cavity fluid during cardiac operations contains significant amounts of endogenous prostacyclin. Considering the potential benefit of prostacyclin on the recovering myocardium, we believe that this fluid should be transfused as a volume replacement, keeping in mind the transient phase of hemodynamic instability.

Atrial myxoma: national incidence, diagnosis and surgical management

Despite being the most common benign intracardiac tumour with an excellent prognosis after surgical excision the incidence of atrial myxoma (except at autopsy) is unknown. We reviewed all patients admitted to the National Cardiac Surgery Unit (n = 26) with an atrial myxoma over a fifteen year period (1977-1991) to compile national incidence data and assess pre-operative diagnosis, management, surgical technique, and outcome. Preoperative symptoms were: congestive cardiac failure (12 patients), embolism (8 patients), constitutional (3 patients), asymptomatic (2 patients) and tachyarrhythmia (1 patient). The diagnosis was confirmed by 2D echocardiography alone in thirteen patients and by a combination of echocardiography and angiography in thirteen patients. At operation the site of the tumour was left atrial in 24 patients and bi-atrial in two patients. All cases were confirmed by histology. All patients made a good post-operative recovery, although one patient survived a pulmonary embolus and one patient developed a deep venous thrombosis. There has been one late death (five months after surgery) from a cerebrovascular accident. Serial echocardiography has revealed one recurrence to date (8 years after surgery). The surgical incidence of these tumours in the Republic of Ireland over the study period was 0.5 atrial myxomas/million population/year. Although rare atrial myxomas are the most important cardiac tumours to diagnose as the results from surgery are excellent.

Mediastinoscopy as a predictor of resectability in patients with bronchogenic carcinoma

Eighty consecutive mediastinoscopies, performed for assessment of patients with bronchogenic carcinoma, were reviewed with regard to accuracy and complications. Thirty patients had mediastinal lymph node metastases: 26 were considered inoperable and thus saved non-therapeutic thoracotomy, 4 were considered operable of whom 3 had a curative resection, and one was inoperable at thoracotomy. Of 50 patients with negative mediastinal nodes 43 had thoracotomy; 42 were resectable and one was unresectable. Seven did not have thoracotomy because of other contraindications. In total of 47 patients undergoing thoracotomy on the basis of mediastinoscopy, 45 were resectable, giving mediastinoscopy a positive predictive value for resectability of 95.7%. There was no mortality and two superficial wound infections occurred giving a morbidity of 2.5%. Mediastinoscopy is a safe, reliable and accurate predictor or resectability in patients with bronchogenic carcinoma and continues to have a major role in the management of these patients.

Repeated echocardiography: essential in the management of Staphylococcus aureus endocarditis

Staphylococcus aureus endocarditis in a previously healthy 25 year old man is described. Repeated echocardiography recorded rapid progression of aortic root and interventricular septal involvement and, even though the patient was clinically stable, early surgery was advised with a satisfactory outcome. This case report clearly demonstrates the vital role of repeated cross-sectional echocardiography in the management of such cases.

Low potassium cardioplegia: its effect on the incidence of complete heart block following cardiac surgery

To investigate whether the concentration of potassium ion in cardioplegic solution was related to the incidence of complete heart block in patients undergoing myocardial revascularisation 163 consecutive cases were studied. Cardiac arrest was with St. Thomas' hospital cardioplegic solution in all patients. Ongoing myocardial protection was provided with St. Thomas' hospital solution (potassium concentration 20 mmol/l) in 56 patients (group A) and with Ringer's injection (potassium concentration 4 mmol/l) in 107 patients (group B). These two groups were studied sequentially. The incidence of complete heart block was higher in group A than in group B. Following aortic unclamping, 27 per cent of patients in group A compared to 14 per cent in group B exhibited the phenomenon (p less than 0.05). At the time of weaning from cardiopulmonary bypass the incidence was 20 per cent in group A compared to 10 per cent in group B (p less than 0.1). No differences were demonstrated between the two groups in terms of myocardial recovery, morbidity or mortality.

Diagnosis of acute and chronic cardiac rejection by magnetic resonance imaging: a non-invasive in-vivo study

To evaluate the potential usefulness for characterization of tissue and anatomical changes associated with cardiac transplantation rejection by nuclear magnetic resonance imaging (MRI), sixteen dogs underwent heterotropic cardiac transplantation with six not immunosuppressed serving as controls. Myocardial biopsy and MRI were obtained and compared on a weekly basis. Untreated allografts showed a significant increase in T2 and intensity values by MRI compared to the native heart as early as one week after transplantation. The MRI findings corresponded to the histological progression of acute rejection process in both treated and untreated groups. The linear relationship between histology and MRI was 0.72 while the correlation between T2 and the water content was 0.92. Serial gated MRI correlated with chronic anatomical changes of transplant rejection with evidence of progressive or increasing myocardial wall thickness and decrease in ventricular chamber size.

Quantitation of intracardiac shunts by cine-CT

Quantitation of intracardiac shunts is important in the evaluation of congenital heart disease and ventricular septal defects postmyocardial infarction. Shunt detection and quantitation is currently performed by either oximetry or radionuclide angiography. Oximetry is an invasive technique and radionuclide angiography, although noninvasive, does not have sufficient spatial resolution to provide detailed anatomic information. The present study evaluated a new technique for quantitating right-to-left shunts by analysis of indicator dilution curves acquired noninvasively using cine-CT. This technique was evaluated in a phantom and in postoperative dogs with a surgically created variable shunt. The phantom model demonstrated the accuracy and reproducibility of the curve analysis algorithm, and the canine model permitted the comparison of oximetry with cine-CT for shunt quantitation. Cine-CT accurately estimated right-to-left shunt fraction when compared with oximetry (r = 0.91) and is more sensitive than oximetry in detecting small shunts. The results of this study suggest that contrast enhanced cine-CT provides a precise noninvasive technique for measuring shunt lesions in congenital and acquired heart diseases.

Magnetic resonance imaging of cardiac transplants: the evaluation of rejection of cardiac allografts with and without immunosuppression

The purpose of this study was to evaluate the potential of magnetic resonance imaging (MRI) in vivo for the characterization of tissue changes associated with acute myocardial rejection after cardiac transplantation. Of 15 dogs that underwent heterotopic cardiac transplantation, six served as untreated controls, and nine received immunosuppressive therapy (25 mg/kg/day cyclosporine, 1 mg/kg/day prednisone). Serial electrocardiographically gated MRI (spin-echo technique) and histologic examinations of allograft biopsy samples were performed for each dog at 2 to 3, 7 to 10, 14 to 17, and 26 to 29 days after transplantation and immediately after animals were killed. Untreated allografts showed a significant increase (p less than .01) in T2 (spin-spin) relaxation time (T2 = 66 +/- 8 msec) and intensity values compared with values in the native hearts (T2 = 44 +/- 6 msec) as early as 1 week after transplantation. The significant difference in T2 values could be observed in vivo as well as on postmortem examination and corresponded to histologic progression of the rejection process. There was no significant difference in T1, T2, or intensity values in cyclosporine-treated allografts and native hearts except in two dogs in which T2 relaxation times and signal intensity in the transplanted hearts increased simultaneously with histologic evidence of rejection, indicating failure of immunosuppressive therapy. There was a significant correlation between histologic grading of severity of rejection and T2 relaxation times of the cardiac transplants (r = .72). Likewise, there was a significant linear relationship between T2 values in vivo and percent water content when the differences between native hearts and allografts were compared (r = .92, p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of ischemia-induced myocardial platelet deposition by exogenous prostacyclin

The antithrombotic effects of prostacyclin infusion on myocardial platelet deposition were studied in a canine model during and after global ischemia. Eleven isolated heart preparations were subjected to 1 hour of cardioplegic arrest under moderate hypothermia (27 degrees to 28 degrees C), including a control group (n = 7) and a prostacyclin-treated group (n = 4). The hearts of four other dogs were continuously perfused for 180 minutes. Platelet deposition was measured at 15 minute intervals throughout the 3 hour study. Serial full-thickness myocardial biopsy specimens were analyzed for activity of 111In-labeled platelets with 99mTc-labeled erythrocyte correction for tissue blood content. The pattern of platelet distribution was determined by scintiscans of each heart, taken with a gamma camera at the end of the 60 minute reperfusion period. Substantial myocardial platelet deposition was found in the control hearts after ischemia but not in the prostacyclin-treated group (p less than 0.05). Furthermore, prostacyclin infusion had a significant disaggregatory effect on intracoronary platelet deposits when the precardioplegic and postcardioplegic biopsy specimens were analyzed (p less than 0.05). Three hours of continuous perfusion did not increase tissue 111In-labeled platelet activity. Ex vivo images showed platelet deposition to be a diffuse patchy process with significantly more 111In activity in the endocardium than in the epicardium after global ischemia (p less than 0.05). These data show the potent antithrombotic properties of prostacyclin in preventing and disaggregating ischemia-induced intracoronary platelet deposition during and after cardioplegic arrest.

Right-sided cardiac transplantation: importance of functional valves

An original surgical procedure had been developed entailing the implantation of a right-sided heterotrophic cardiac graft in 14 dogs. The benchwork preparation included creation of both atrial and ventricular septal defects which allowed transplantation with the avoidance of extracorporeal circulation and the utilization of all transplanted myocardium and parts. The structure and function of this graft were sequentially evaluated using rapid cine-computed tomograms which permitted assessment of forward graft flow, ventricular wall contraction, and diastolic thickness for both the native and grafted hearts. These parameters were followed during the early (E) (less than 3 days), intermediate (I) (4-21 days), and late (L) (greater than 21 days) postoperative periods. Forward flow (E: 3.0, I: 1.5, L: 2.6) through the transplant was maintained by the competence of the implanted valves despite a progressive decrease in the contraction (E: 3.0, I: 1.3, L: 1.0) and associated decrease in the wall thickness (E: 3.0, I: 2.6, L: 2.4). These findings were consistent with severe cardiac graft rejection without immunosuppression. In summary, long-term structural and functional forward flow of this configurated right-sided transplantation had been maintained by the competent valves on both sides of the graft despite severe rejection without immunosuppression as documented by rapid cine-computed tomograms.

Intracoronary platelet aggregation: pattern of deposition after ischemia, cardioplegia, and reperfusion

Platelet deposition in the coronary microvasculature has not been completely defined in the temporal relationship to acute myocardial ischemia, the application of crystalloid cardioplegia, and during reperfusion on heart bypass. Twenty-two canine hearts were serially biopsied for the analysis of radioactively tagged platelets. Eleven hearts underwent an isolated heart support preparation with seven followed by potassium cardioplegic arrest and reperfusion while the remaining 4 were maintained on continuous bypass. All 11 hearts undergoing bypass experienced transient (less than 90 sec) ischemia during bypass preparation and produced platelet aggregation in the myocardium (51.12 +/- 24.0 as compared to nonischemic control group 12.3 +/- 4.7; P = 0.005). Potassium cardioplegia did not completely wash out these platelets to the nonischemic control levels (27.8 +/- 14.9; P = 0.04). With the onset of reperfusion after 1 hr of cardioplegic arrest, platelet radioactivity profoundly increased (133.3 +/- 72.8; P = 0.0101) and remained high throughout the hour of reperfusion (324.7 +/- 269.3; P = 0.0369). In summary, intracoronary platelets are activated after transient ischemic episodes during initiation of heart bypass. These ischemia-activated platelet aggregations persist despite the application of cardioplegia during the arrest period. This deposition, in turn, allowed an ongoing pattern of platelet aggregation during the early and subsequent reperfusion. This pattern of ischemia-activated platelet aggregations probably accounts for the progressive reperfusion injury and support of an antiplatelet treatment for coronary microvasculature protection.

Cardiac transplantations in dogs: evaluation with MR

To assess the potential of magnetic resonance (MR) imaging as an early predictor of cardiac transplant rejection, electrocardiogram-gated (ECG-gated) MR imaging was performed in 12 dogs with heterotopic cardiac transplants. Twenty-two examinations were performed in vivo, and ten postmortem examinations were performed immediately after the dogs were killed. Examinations were performed from 3 days to 14 weeks after transplantation. A 0.35-T superconducting magnet was used with the spin-echo pulse sequence. There was a significant increase (P less than .02 to P less than .001) in T2 relaxation times and intensity values for the transplanted hearts compared with native hearts at all time intervals after transplantation. T1 relaxation times of native and transplanted hearts showed no significant difference on the in vivo ECG-gated studies. However, T1 values calculated on post-mortem studies were significantly longer (P less than .005) in the transplanted compared with the native hearts. With longer pulse repetition and echo delay times, there was an increase in the contrast between the rejecting transplanted heart and the native heart. Thus, ECG-gated MR imaging using the spin-echo technique displays cardiac allograft rejection in vivo. The rejected myocardium in vivo is characterized by a prolonged T2 relaxation time.

Does prostacyclin (PGI2) cardioplegic infusion improve myocardial protection after ischemic arrest?

To determine whether prostacyclin (PGI2) plays a beneficial role in the blood-perfused heart undergoing global ischemia, 20 isolated canine hearts were studied after sustaining one hour of cardioplegic arrest under moderate hypothermia (27 degrees to 28 degrees C). Left ventricular function (peak systolic pressure, rate of rise of left ventricular pressure [dP/dt], and compliance change in left ventricular volume), myocardial edema, coronary blood flow, and oxygen content were measured during the preischemic period and at 15 and 30 minutes during reperfusion. Results showed an improved hemodynamic recovery (peak systolic pressure, p = 0.018 at 30 minutes; dP/dt, p = 0.020 at 15 minutes) in the group of hearts treated with PGI2 infusion compared with controls. There was no difference in ventricular compliance or myocardial edema between the two groups. This benefit was attributed to a significant increase in myocardial blood flow (p = 0.028 at 15 minutes) and oxygen delivery (p = 0.021 at 15 minutes) during the reperfusion period with PGI2. These data suggest a potential clinical role for PGI2 when applied to the globally ischemic heart in the improvement of myocardial resuscitation during the early reperfusion period.