David M. Moskowitz

Safety and Efficacy of High-Dose Adenosine-Induced Asystole during Endovascular AAA Repair

Purpose: To assess the safety and efficacy of high-dose adenosine administration to increase the precision of endovascular abdominal aortic aneurysm (AAA) repair using a balloon deployed stent-graft. Methods: From January 1997 to March 1999, 98 AAA patients (79 men; mean age 71 years, range 62–91) were treated with balloon-expandable stent-grafts under an approved protocol. After placing a temporary transvenous ventricular lead or an external transthoracic pacing electrode, adenosine (24 mg initially) was administered in an escalating dose fashion to induce at least 10 seconds of asystole, during which the proximal stent was expanded. Results: Adenosine dosages ranged from 24 to 90 mg (median 24 mg). Nine (9.2%) self-limiting cardiac events were observed: 2 (2.0%) episodes of transient myocardial ischemia, 2 (2.0%) cases of atrial fibrillation requiring cardioversion, 1 (1.0%) transient left bundle branch block lasting <10 seconds, and 4 (4.1%) prolonged periods of asystole requiring temporary pacemaker activation. There were no cases of bronchospasm or worsening obstructive pulmonary disease, and no patients required inotropic support after adenosine-induced asystole. Conclusions: Cardiac events following adenosine-induced asystole are infrequent, mild, and easily treated. The perioperative use of high-dose adenosine to ensure precise stent-graft placement appears to be a safe method of inducing temporary asystole during endovascular aortic repair.

Use of intraoperative transesophageal echocardiography to predict atrial fibrillation after coronary artery bypass grafting.

BackgroundPostoperative atrial fibrillation in coronary artery bypass graft surgery occurs in 10–40% of patients. It is associated with a significant degree of morbidity and results in prolonged lengths of stay in both the intensive care unit and hospital. MethodsThe authors prospectively evaluated patients undergoing coronary artery bypass with detailed transesophageal echocardiography examinations conducted before and after cardiopulmonary bypass to study whether risk factors for atrial fibrillation could be identified. Demographic and surgical parameters were also included in the analysis. Selected variables were subjected to univariate and subsequent multivariate analyses to test for their independent or joint influence on atrial fibrillation. ResultsSeventy-nine patients had assessable transesophageal echocardiography examinations. Significant univariate predictors of atrial fibrillation included advanced age (P = 0.002), pre–cardiopulmonary bypass left atrial appendage area (P = 0.04), and post–cardiopulmonary bypass left upper pulmonary vein systole/diastole velocity ratio (P = 0.03). When these three factors were considered together in a multiple logistic regression analysis, left upper pulmonary vein systole/diastole velocity ratio was a significant predictor (P < 0.05), as was the joint effect of age plus pre–cardiopulmonary bypass left atrial appendage area (P = 0.005). The probability of developing atrial fibrillation for the combination of age = 75 yr, post–cardiopulmonary bypass left upper pulmonary vein systole/diastole velocity ratio = 0.5, and left atrial appendage area = 4.0 cm was 0.83 (95% confidence interval, 0.51–0.96). ConclusionsEarly identification of patients at risk for postoperative atrial fibrillation may be feasible using the parameters identified in this study.

Intraoperative rupture of an abdominal aortic aneurysm during an endovascular stent-graft procedure

PurposeTo highlight the risk of intraoperative rupture as a complication of endovascular aortic repair.Clinical featuresAn 81-yr-old man was admitted for endovascular aortic repair of a 6 cm infrarenal abdominal aortic aneurysm. After establishment of a conduction blockade using a combined spinal-epidural technique, a balloon-activated endovascular stent-graft was advanced to the proximal aneurysmal neck. Approximately four minutes after the stent-graft was deployed, the mean arterial pressure decreased to 30 mmHg and the heart rate increased to 135 bpm. While fluid and vasoactive medications were administered and the airway was secured, repeat aortography confirmed contrast extravasation into the retroperitoneal space at the junction of the proximal aortic neck and the aneurysm sac. The angioplasty deployment balloon was repositioned and inflated proximal to the presumed site of aortic rupture, thus providing aortic control until an open repair of the aorta was undertaken.ConclusionAlthough endovascular stent-graft placement may be a less invasive method than conventional open aortic reconstruction, it must be recognized that the potential for devastating consequences such as aortic rupture is present.RésuméObjectifSouligner le risque de rupture peropératoire comme complication d’une réparation aortique endovasculaire.Éléments cliniquesUn homme de 81 ans a été admis pour la réparation aortique endovasculaire d’un anévrisme infrarénal de l’aorte abdominale. Après avoir établi un bloc de conduction selon une technique rachidienne et péridurale combinée, un greffon-tuteur endovasculaire, activé par un ballonnet, a été introduit jusqu’au collet proximal de l’anévrisme. Environ quatre minutes après le déploiement du greffon-tuteur, la tension artérielle moyenne a chuté à 30 mmHg et la fréquence cardiaque a augmenté à 135 bpm. Pendant l’administration de liquide et de médicaments vasoactifs et les manoeuvres visant à assurer la liberté des voies aériennes, l’aortographie répétée a confirmé une extravasation de contraste dans l’espace rétropéritonéal à la jonction du collet aortique proximal et du sac anévrismal. Le ballonnet a été replacé et gonflé près du site présumé de la rupture aortique, permettant ainsi de préserver l’aorte jusqu’à ce qu’une réparation chirurgicale soit réalisée.ConclusionBien que la mise en place d’un greffon-tuteur endovasculaire soit moins effractif que la reconstruction aortique chirurgicale habituelle, il faut reconnaître la présence potentielle de graves conséquences, comme une rupture aortique.

Does acute normovolemic hemodilution work in cardiac surgery

To the Editor:—In a recent article by Höhn et al., it was concluded that acute normovolemic hemodilution (ANH) in addition to aprotinin was not beneficial in preventing allogeneic blood transfusions compared to aprotinin alone in cardiac surgery. In this randomized, controlled trial, the patients were hemodiluted to a hematocrit of 28% pre–cardiopulmonary bypass (CPB). The transfusion threshold was set at 17% during CPB and at 25% for post-CPB. The total fluid replacement was in excess relative to the amount of ANH (autologous blood) removed (6.4 2.1 l of crystalloid, 2.0 0.7 l of colloid). This led to excessive hemodilution, reducing the hematocrit below the transfusion threshold in the ANH group. Indeed, 50% of the patients in the ANH group required either all (33%) or a portion (22%) of the autologous blood to be transfused during CPB, thus negating its positive effects on erythrocytes and coagulation protection. Consequently, allogeneic erythrocyte transfusion rates and the indirect clinical markers for surgical bleeding (cell saver and 24-h chest tube drainage) were not different between the two groups. One of the goals of ANH is to protect the autologous blood from the negative effects of CPB and to return it after heparin neutralization. Additional hemodilution occurs with the onset of CPB; therefore, hemofiltration or ultrafiltration and/or diuresis should have been employed to remove excess fluid. Alternatively, ANH can be performed just prior to the onset of CPB (by diverting heparinized blood into a storage bag), thus preventing excessive dilutional anemia. The criteria for exclusion from this study were left main disease, severe aortic stenosis, recent myocardial infarction, unstable angina, ejection fraction below 30%, severe carotid stenosis, combined coronary artery bypass grafting and valve cases, respiratory insufficiency, renal insufficiency, and anemia (hemoglobin 12 g/dl). This exclusion process resulted in the selection of a group of patients that we know are at low risk for allogeneic transfusions. Our data (shown below) and those of other investigators demonstrate that patients presenting with adequate hemoglobin levels (average starting hematocrit of 43.3%, body surface area of 1.86) rarely require allogeneic blood. At our institution, the cardiac surgery program utilizes a multidisciplinary approach to blood conservation. In over 300 cardiac surgery cases (coronary artery bypass grafting, valves, and combined procedures), we remove on average 1280 ml of ANH blood per case (based on a formula to reach a target hematocrit on bypass of 20%). The average amount of fluid used for replacement was 1680 ml of crystalloid and 591 ml of colloid (Hextend, Abbott Laboratories, North Chicago, IL). Hemofiltration or ultrafiltration and/or induced diuresis is frequently utilized on CPB to remove excess fluids and to reduce the dilutional effect from the CPB prime. The starting hematocrit averages 39%. We use -aminocaproic acid for low-risk cases and reserve aprotinin (Trasylol, Bayer, West Haven, CT) for high-risk cases. The total amount of cell saver returned is approximately 200 ml, and 24-h chest tube drainage is 428 ml. Allogeneic transfusion rates for packed erythrocytes, fresh frozen plasma, and cryoprecipitate are 11%, 3%, and less than 1%, respectively.

8 Echocardiography in aortic disease

Transoesophageal echocardiography has rapidly become an important diagnostic modality for patients with aortic atherosclerosis or aortic dissection. Use of this modality can help direct patients to proper therapeutic modalities. This paper will review the role of transoesophageal echocardiography in these disease processes.

Aortic Dissection: Is Transesophageal Echocardiography the Diagnostic Method of Choice?

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