Daniel H. Benckart

Characterization of Signal Properties in Atherosclerotic Plaque Components by Intravascular MRI

Magnetic resonance imaging (MRI) is capable of distinguishing between atherosclerotic plaque components solely on the basis of biochemical differences. However, to date, the majority of plaque characterization has been performed by using high-field strength units or special coils, which are not clinically applicable. Thus, the purpose of the present study was to evaluate MRI properties in histologically verified plaque components in excised human carotid endarterectomy specimens with the use of a 5F catheter-based imaging coil, standard acquisition software, and a clinical scanner operating at 0.5 T. Human carotid endarterectomy specimens from 17 patients were imaged at 37 degrees C by use of an opposed solenoid intravascular radiofrequency coil integrated into a 5F double-lumen catheter interfaced to a 0.5-T General Electric interventional scanner. Cross-sectional intravascular MRI (156x250 microm in-plane resolution) that used different imaging parameters permitted the calculation of absolute T1and T2, the magnetization transfer contrast ratio, the magnitude of regional signal loss associated with an inversion recovery sequence (inversion ratio), and regional signal loss in gradient echo (gradient echo-to-spin echo ratio) in plaque components. Histological staining included hematoxylin and eosin, Massons trichrome, Kossa, oil red O, and Gomoris iron stain. X-ray micrographs were also used to identify regions of calcium. Seven plaque components were evaluated: fibrous cap, smooth muscle cells, organizing thrombus, fresh thrombus, lipid, edema, and calcium. The magnetization transfer contrast ratio was significantly less in the fibrous cap (0.62+/-13) than in all other components (P<0.05) The inversion ratio was greater in lipid (0.91+/-0.09) than all other components (P<0.05). Calcium was best distinguished by using the gradient echo-to-spin echo ratio, which was lower in calcium (0.36+/-0.2) than in all plaque components, except for the organizing thrombus (P<0.04). Absolute T1 (range 300+/-140 ms for lipid to 630+/-321 ms for calcium) and T2 (range 40+/-12 ms for fresh thrombus to 59+/-21 ms for smooth muscle cells) were not significantly different between groups. In vitro intravascular MRI with catheter-based coils and standard software permits sufficient spatial resolution to visualize major plaque components. Pulse sequences that take advantage of differences in biochemical structure of individual plaque components show quantitative differences in signal properties between fibrous cap, lipid, and calcium. Therefore, catheter-based imaging coils may have the potential to identify and characterize those intraplaque components associated with plaque stability by use of existing whole-body scanners.

Paced skeletal muscle for dynamic cardiomyoplasty

Four patients, each with a history of myocardial infarction and diffuse coronary artery disease, underwent application of left latissimus dorsi (LD) muscle with intact neurovascular bundle to the anterolateral wall of the left ventricle. The muscle was conditioned over a six-week period subsequent to operation in 3 patients and was conditioned preoperatively with a burst stimulus in the fourth. Biopsy specimens confirm the experimental data that human skeletal muscle can be electrically conditioned over a six- to ten-week period to contain mainly fatigue-resistant type I fibers. All patients survived the procedure, and 3 showed improvement secondary to aneurysmectomy. In Patient 1, a modified resection was performed, and at 28 months after operation, at the 75-W level of exercise, the ejection fraction was 54% paced versus 45% nonpaced. In Patient 2, at 12 months, the ejection fraction at rest was 44% paced versus 30% nonpaced. Doppler echo studies confirmed the presence of the flap and its function in the paced and nonpaced mode. The third patient died of a sudden ventricular arrhythmia 2 months following operation. An infected, nonfunctioning, degenerated flap was found at autopsy. Patient 4 did not have an aneurysm. She received a bypass graft to the right coronary artery and underwent cardiomyopexy in an attempt to relieve medically refractory incapacitating chronic congestive heart failure. Ten months postoperatively, ejection fraction at rest was 33% paced versus 25% nonpaced. Constrictive myopathy has not been encountered in any of these patients.

Mechanical Support of the Failing Heart

Mechanical ventricular assist with a centrifugal pump with or without anticoagulation for an extended period has been used in 41 patients with postcardiotomy ventricular failure. Left ventricular, right ventricular, and biventricular assist were required. The efficacy and safety of mechanical ventricular assist have been documented. Marked improvement in survival has been observed in the more recent part of this series, and is attributed to earlier employment of the assist device, maintenance of better flow rates near physiological levels, and use of biventricular assist to provide effective circulatory support. Mechanical ventricular assist is easy to use, and the conversion from ordinary cardiopulmonary bypass is also easy. Therefore, mechanical assist provides a very effective means of temporary circulatory assist.

Partial versus full sternotomy for aortic valve replacement.

BACKGROUNDnRecent trends suggest that smaller incisions reduce postoperative morbidity. This study tests the hypothesis that a partial upper sternotomy improves patient outcome for aortic valve replacement.nnnMETHODSnA group of 50 patients who underwent aortic valve surgery through a partial upper sternotomy (group I) were compared to 50 patients who underwent aortic valve replacement through a median sternotomy during the same time period (group II). The mean age (60+/-2 versus 63+/-2 years; mean +/- SEM) and preoperative ejection fractions (53+/-2 versus 54+/-2) were similar. Operations were performed with central cannulation, and antegrade/retrograde blood cardioplegia.nnnRESULTSnThere was one death in each group. No differences were found in aortic occlusion time, mediastinal drainage, transfusion incidence, narcotic requirement, length of stay, or cost. The incidence of pleural and pericardial effusions was increased (18.4% versus 3.9%, p < 0.03), and the need for postoperative inotropic support was higher (38.7% versus 19.6%, p < 0.03) in the partial sternotomy group.nnnCONCLUSIONSnAortic valve replacement can be performed through a partial sternotomy with results comparable to full sternotomy. The partial sternotomy offers a cosmetic benefit, but does not significantly reduce postoperative pain, length of stay, or cost.

Paced latissimus dorsi used for dynamic cardiomyoplasty of left ventricular aneurysms.

Two patients are described, each with a large left ventricular aneurysm and severe coronary artery disease, and each with an ejection fraction lower than 30% and in congestive heart failure. In both, the left latissimus dorsi (LD) muscle was used in the repair of the ventricular aneurysm because preoperative studies demonstrated that there was concomitant coronary artery disease, and there was a strong suggestion that resection of the entire aneurysm would seriously compromise the residual ventricular capacity. One patient had an 18-year history of coronary occlusion with two infarctions. A large, calcified ventricular aneurysm developed, and despite vigorous medical treatment, intractable congestive heart failure and angina persisted. The diffuse coronary artery disease made this patient a poor candidate for bypass grafting. The other patient sustained an acute myocardial infarction 5 months prior to operation. The left anterior descending coronary artery was totally occluded, and a large apical aneurysm developed along with an akinetic anterior wall and septum. After his heart attack, the patient had progressive dyspnea on exertion. Following operation in both patients, the transpositioned LD, then a component in the repair of the left ventricular wall, was electrically trained to synchronously contract with each systole, driven by a standard dual-chamber cardiac pacemaker. Steady improvement and a return to normal activities were observed in both patients. There was an indication of improved ejection fraction with synchronous contraction of the skeletal muscle.

Reduced incidence of atrial fibrillation with minimally invasive direct coronary artery bypass

BACKGROUNDnAtrial fibrillation (AF) is a frequent complication after coronary artery bypass graft (CABG) surgery. The purpose of this study was to determine the incidence of postoperative AF after minimally invasive direct coronary artery bypass (MIDCAB) in comparison with CABG.nnnMETHODSnBetween November 1995 and May 1997, 96 MIDCAB procedures were performed. During the same period, 42 patients underwent traditional single CABG using the left internal mammary artery graft (S-CABG). The incidence of in-hospital AF, defined as a sustained episode requiring treatment, was compared between the two groups.nnnRESULTSnThere was no difference in age, ejection fraction, or preoperative risk score between the groups. The use of beta-blockers before or after surgery was not different. The incidence of postoperative AF in the first 6 weeks after surgery was 4% (4 of 96) for MIDCAB and 28% (12 of 42) for S-CABG (p = 0.003). Patients with postoperati

Left pleural effusion after coronary artery bypass decreases with a supplemental pleural drain

BACKGROUNDnThis prospective study was undertaken to determine the incidence of symptomatic left pleural effusion after coronary artery bypass grafting, and to determine if routine drainage of the pleural cavity with a supplemental flexible drain reduces this incidence.nnnMETHODSnThe clinical course of study patients was prospectively recorded during the initial hospitalization and at 6-weeks after surgery. All patients had a mediastinal and a left pleural tube, which were removed on the 1st postoperative day. The supplemental drain system was implanted in a subset of patients and remained in place for 3 to 5 days. A symptomatic effusion was defined as one that required thoracentesis, tube thoracostomy, or readmission for treatment.nnnRESULTSnA total of 460 patients were studied, of whom 115 had a supplemental drain. The two groups (supplemental drain versus control) were equivalent with respect to age, gender distribution, and comorbid diseases. The incidence of symptomatic left pleural effusion for the entire group was 9.8% (45 of 460). Symptomatic left pleural effusion occurred in 11.9% (41 of 345) patients when only chest tubes were used, and in 3.5% (4 of 115) when a supplemental drain was placed. This difference was significant (F ratio 7.583, p < 0.005). There were no complications from the supplemental drain.nnnCONCLUSIONSnThe incidence of symptomatic left pleural effusion can be greatly reduced with the use of a supplemental pleural drain that remains in place for several days after surgery.

Preoperative statin is associated with decreased operative mortality in high risk coronary artery bypass patients

BackgroundStatins are widely prescribed to patients with atherosclerosis. A retrospective database analysis was used to examine the role of preoperative statin use in hospital mortality, for patients undergoing isolated coronary artery bypass grafting (CABG.)MethodsThe study population comprised 2377 patients who had isolated CABG at Allegheny General Hospital between 2000 and 2004. Mean age of the patients was 65 ± 11 years (range 27 to 92 years). 1594 (67%) were male, 5% had previous open heart procedures, and 4% had emergency surgery. 1004 patients (42%) were being treated with a statin at the time of admission. Univariate, bivariate (Chi2, Fishers Exact and Students t-tests) and multivariate (stepwise linear regression) analyses were used to evaluate the association of statin use with mortality following CABG.ResultsAnnual prevalence of preoperative statin use was similar over the study period and averaged 40%. Preoperative clinical risk assessment demonstrated a 2% risk of mortality in both the statin and non-statin groups. Operative mortality was 2.4% for all patients, 1.7% for statin users and 2.8% for non-statin users (p < 0.07). Using multivariate analysis, lack of statin use was found to be an independent predictor of mortality in high-risk patients (n = 245, 12.9% vs. 5.6%, p < 0.05).ConclusionsBetween 2000 and 2004 less than 50% of patients at this institution were receiving statins before admission for isolated CABG. A retrospective analysis of this cohort provides evidence that preoperative statin use is associated with lower operative mortality in high-risk patients.

Traumatic Aortic Transection: Repair Using Left Atrial to Femoral Bypass

Traumatic aortic transaction is a life‐threatening surgical emergency. Therapy must be directed at rapid repair and prevention of postoperative complications, the most serious being paraplegia. Controversy over the optimal method of repair exists‐specifically whether the use of a shunt modifies the outcome. Our series of 17 patients using left atrial to femoral bypass with the Biomedicus pump will be discussed. Preoperative preparation and operative technique will be outlined. Mortality in this series was 18%, the incidence of paraplegia was 0.

Challenging Neck Anatomy Is Associated With Need for Intraoperative Endovascular Adjuncts During Endovascular Aortic Aneurysm Repair (EVAR)

BACKGROUNDnThe purpose of this study was to determine which proximal seal zone characteristics were predictive of early and late type Ia endoleak development after endovascular aortic aneurysm repair (EVAR) for infrarenal abdominal aortic aneurysmal disease.nnnMETHODSnWe evaluated 146 patients who underwent EVAR between January 2006 and March 2007. In the cohort, high-resolution computed tomography images of 100 (68.5%) patients were available, which showed detailed measurement of proximal neck parameters, including diameter, length, calcification, thrombus, suprarenal and infrarenal angles, and reverse taper morphology. Postprocessing of digital data sets was performed to obtain centerline-of-flow measurements. Relevant medical records and follow-up computed tomography scans were reviewed.nnnRESULTSnMean age of the patients was 72.7 years, with 78% being male. Of these patients, 66% did not satisfy the instructions for use for the Zenith EVAR device, and 50% did not satisfy the instructions for use for the AneuRx device. Nine patients had intraoperative type Ia endoleaks. A 100% assisted primary technical success rate was achieved with the adjunctive use of angioplasty (n = 4), uncovered stent (n = 3), and extension cuff (n = 2) placement. There was a significant association between type Ia endoleak development and magnitude of the infrarenal angle (p < 0.01); however, other parameters were not significant. At follow-up (mean, 587 days), no patient had a type Ia endoleak, and there were no aneurysm-related deaths.nnnCONCLUSIONSnOur data indicate that infrarenal angle is related to intraoperative type Ia endoleak occurrence, but other factors often thought to be indicative of adverse neck anatomy are not significant predictors. Moreover, all type Ia endoleaks in this cohort were successfully eliminated intraoperatively, and durability was confirmed on postoperative surveillance. These data demonstrate that challenging neck anatomy is associated with the need for intraoperative endovascular adjuncts, and that effective and durable aneurysm exclusion should still be expected.