Brian L. Ganzel

The role of neuromonitoring in cardiovascular surgery

This review describes the techniques currently used for quantitative neurophysiologic measurement during cardiac surgery and their potential impact on clinical outcome. Electroencephalography (EEG) characterizes cerebrocortical neuronal electrical activity and was part of some of the earliest cardiopulmonary bypass procedures, yet today it is not widespread use. Each of the common misunderstandings regarding a supposed limitation of this technology is explained. Its major genuine shortcoming, a lack of selectivity, may now be overcome with the combined use of additional monitoring modalities. The influence of intracranial hemodynamics on observed EEG changes may be determined continuously and noninvasively with transcranial Doppler (TCD) ultrasound. TCD provides an indication of sudden change in either blood flow or vascular resistance as well as the detection of emboli. In addition, the metabolic status of cortical neurons can be monitored by regional cerebral venous oxygen saturation (rCVOS) using noninvasive transcranial near-infrared spectroscopy. The % rCVOS tends to remain remarkably stable over a wide range of temperatures, perfusion pressures, and anesthetic states. Marked change in either direction signifies a serious imbalance between oxygen delivery and consumption. Measurement of rCVOS does not require blood flow, pulsatile or otherwise, so that it offers the only means of monitoring during circulatory arrest. By characterizing the dynamic interplay among cerebral hemodynamics, metabolism, and electrogenesis, these technologies permit the rapid detection and correction of potentially hazardous conditions.

Neurophysiologic monitoring to assure delivery of retrograde cerebral perfusion

BACKGROUND Patients undergoing complex aortic procedures performed with deep hypothermia and circulatory arrest have a significant risk of an adverse neurologic event when the arrest period is prolonged. Retrograde cerebral perfusion appears to improve cerebral protection, although collapsed cortical veins or functional jugular venous valves may restrict flow at the frequently recommended maximum pressure of 25 mm Hg. Therefore, the purpose of this study was to demonstrate the benefit of multimodality neurophysiologic monitoring in assuring delivery of retrograde cerebral perfusion. METHODS Electroencephalography, cerebral blood flow velocity, and regional cerebral venous oxygen saturation were used to quantify the intraoperative neurophysiologic changes accompanying retrograde cerebral perfusion. The magnitude of changes was compared with those previously observed during arrest without retrograde cerebral perfusion. RESULTS Thirty patients underwent complex aortic procedures necessitating circulatory arrest, 22 with retrograde cerebral perfusion. The mean retrograde perfusion pressure of 40 mm Hg (30 to 49 mm Hg, 95% confidence interval) and flow rate of 1.2 L/min (0.9 to 1.6 L/min) necessary to achieve documented retrograde cerebral perfusion was much higher than previously recommended. During both retrograde cerebral perfusion and rewarming, cerebral oximetric monitoring guided adjustments in perfusion parameters to limit the rate of desaturation to 0.4% per minute (0.3% to 0.6%). With retrograde cerebral perfusion there was a rapid (1) recovery of electroencephalographic activity during rewarming (21 minutes [range 16 to 26 minutes]) and (2) return of consciousness after the operation (81% [58% to 95%, 95% confidence interval] awake by 12 hours). There was no transcranial Doppler evidence of cerebral edema with retrograde cerebral perfusion. Two neurologic complications occurred in the 22 patients managed with retrograde cerebral perfusion and one in the eight patients managed with arrest only. CONCLUSIONS Multimodality neurologic monitoring assured optimal brain cooling and bihemispheric delivery of retrograde cerebral perfusion. Necessary retrograde pressure and flow were often higher than values previously reported. Avoidance of profound cerebral venous oxygen desaturation during retrograde cerebral perfusion and rewarming was associated with rapid recovery of neurologic function.

Emergency Aortocoronary Bypass After Failed Angioplasty

One thousand two hundred fourteen percutaneous transluminal coronary angioplasties were performed over a 38-month period. Sixty patients required immediate emergency coronary artery bypass grafting after angioplasty failure; 7 of these had evidence of acute myocardial infarction before angioplasty and were excluded from the study. Of the 53 patients remaining, 27 (51%) had electrocardiographic and enzyme evidence of postoperative myocardial infarction. Two patients died (4%), and 10 had postoperative complications (19%). No statistical significance was noted comparing age, sex, incidence of prior myocardial infarction or myocardial dysfunction, time for revascularization, or average number of grafts completed in those with single-vessel (n = 21) versus multiple-vessel (n = 32) coronary artery disease. Postoperatively, those with multiple-vessel disease required intraaortic balloon pump support (p = 0.06) and antiarrhythmic medications more frequently than single-vessel patients (p less than 0.01) and had a higher complication rate (p less than 0.05). Although not reaching statistical significance, the data also suggest a higher death and postoperative myocardial infarction rate in patients with multiple-vessel disease. Emergency coronary artery bypass grafting after failed percutaneous transluminal coronary angioplasty carries a higher morbidity and mortality than elective coronary artery bypass grafting, particularly for patients with multiple-vessel coronary artery disease.

Surgical techniques for the implantation of heterotopic prosthetic ventricles

Mechanical support of the failing heart is becoming an increasingly useful tool for bridging to cardiac transplantation and for recovery of the natural heart. Several options exist for cannulation sites during the implantation of the heterotopic prosthetic ventricles. These options include the left atrial appendage, the left ventricular apex, the interatrial groove, and the left atrial roof. The indications, contraindications, advantages, disadvantages, and surgical technique for each option are described. Operation of the drive console and postoperative care are also discussed.

Thoracic Aortic Mobile Thrombus: Is There a Role for Early Surgical Intervention?

BACKGROUND The diagnosis of thoracic aortic mobile thrombus (TAMT) is rare and is usually made after debilitating embolic events. The optimal treatment strategy is unknown. We report 14 patients with TAMT and aim to better define the role of early (less than 2 weeks) surgical thrombectomy. METHODS Between February 1996 and February 2010, we treated 14 patients (9 women; aged 32 to 84 years, mean age 51 years) with TAMT. Hypercoagulable disorders or a strong family history of vascular thrombosis, or both, occurred in 9 patients. Diagnosis was made by transesophageal echocardiogram in 6, computed tomography angiography in 7, and digital subtraction angiography in 1. Embolic locations were extremities (n=9), cerebral (n=6), and abdominal (n=6). Aortic thrombi (n=17) locations were ascending/arch (n=7), descending (n=8), and thoracoabdominal (n=2). RESULTS All patients were initially treated with heparin and aspirin. Thoracic aortic thrombectomies were performed in 8 patients within 2 weeks of diagnosis: left thoracotomy (n=5), thoracoabdominal (n=1), and median sternotomy (n=2). Left atrial-femoral bypass was used in 5 patients, cardiopulmonary bypass in 2, and no support in 1. Additional procedures were celiac artery (n=1) and left subclavian artery (n=2) thrombectomies. Procedures for embolic complications were performed in 7 patients before aortic thrombectomy. Operative mortality was 0%, with no recurrent embolic events after 24±16 months. One patient had thrombectomy of the ascending aorta and medical therapy with warfarin and aspirin for a second concurrent small thrombus in the descending aorta. One patient presented with multiorgan failure and died shortly after admission. Six patients treated medically were discharged on a regimen of oral warfarin and aspirin (14±11 months follow-up), with 2 fatal recurrent embolic events within 6 weeks (p=0.09). CONCLUSIONS Thoracic aortic mobile thrombus is rare and is commonly associated with morbid thromboembolic events. In our experience, early surgical aortic thrombectomy had a low operative risk and may prevent fatal recurrent embolic events.

Early and Midterm Outcomes Following Surgery for Acute Type A Aortic Dissection

Surgical repair of acute Type A aortic dissection (AADA) is still associated with high in‐hospital mortality. We evaluated the impact of perioperative risk factors on early and midterm survival.

The Pierce-Donachy Ventricular Assist Device as a Bridge to Cardiac Transplantation

The Pierce-Donachy ventricular assist device (VAD) was used as an attempted bridge to orthotopic cardiac transplantation in 12 patients aged 13 to 55 years. Ischemic (4 patients), dilated (4 patients), acute viral (1 patient), postpartum (1 patient), and hypertrophic cardiomyopathy (1 patient), along with a failed transplant (1 patient), were the causative factors of end-stage cardiomyopathy in these patients. All patients were candidates for orthotopic cardiac transplantation but sustained refractory cardiogenic shock (cardiac index less than 2 L/min/m2). Left VADs were placed in all patients; 7 also required right VADs. Four patients died of hemorrhagic complications less than 24 hours after VAD insertion. Ventricular assist device stabilization was successful in 8 patients and support ranged from eight hours to 64 days. Seven patients successfully underwent orthotopic cardiac transplantation. One died postoperatively of hemorrhagic complications, 6 were discharged from the hospital, and 1 patient died at 3 months of cytomegalovirus infection. Five patients are long-term survivors. The Pierce-Donachy VAD is an effective means for supporting critically ill patients with end-stage cardiomyopathy and cardiogenic shock before orthotopic cardiac transplantation. Death is related to hemorrhagic, rather than infectious or thromboembolic, complications. Patients successfully stabilized with the VAD can undergo orthotopic cardiac transplantation with acceptable mortality and morbidity rates.

Experimental aerobic-anaerobic thoracic empyema in the guinea pig.

The clinical and pathological features of experimental aerobic-anaerobic thoracic empyema in the Duncan-Harley guinea pig are described. Thoracic empyema development and early death (less than 14 days after bacterial inoculation) were noted after various concentrations and species were inoculated into the pleural space with a piece of umbilical tape, which was used as a cofactor. The effect of concomitant hemothorax was also tested. Gram-negative infection was found to have a more virulent course than Gram-positive infection in the thoracic cavity. Moreover, these findings support the thesis that intrathoracic inoculation of anaerobic bacteria, even in combination with other anaerobic species, fails to produce clinical empyemas. However, anaerobic bacteria appear to enhance synergistically the virulence of sublethal and subempyema-forming concentrations of aerobic bacteria such as Staphylococcus aureus and Escherichia coli.

Safety of Intracoronary Infusion of 20 Million C-Kit Positive Human Cardiac Stem Cells in Pigs

Background There is mounting interest in using c-kit positive human cardiac stem cells (c-kitpos hCSCs) to repair infarcted myocardium in patients with ischemic cardiomyopathy. A recent phase I clinical trial (SCIPIO) has shown that intracoronary infusion of 1 million hCSCs is safe. Higher doses of CSCs may provide superior reparative ability; however, it is unknown if doses >1 million cells are safe. To address this issue, we examined the effects of 20 million hCSCs in pigs. Methods Right atrial appendage samples were obtained from patients undergoing cardiac surgery. The tissue was processed by an established protocol with eventual immunomagnetic sorting to obtain in vitro expanded hCSCs. A cumulative dose of 20 million cells was given intracoronarily to pigs without stop flow. Safety was assessed by measurement of serial biomarkers (cardiac: troponin I and CK-MB, renal: creatinine and BUN, and hepatic: AST, ALT, and alkaline phosphatase) and echocardiography pre- and post-infusion. hCSC retention 30 days after infusion was quantified by PCR for human genomic DNA. All personnel were blinded as to group assignment. Results Compared with vehicle-treated controls (n=5), pigs that received 20 million hCSCs (n=9) showed no significant change in cardiac function or end organ damage (assessed by organ specific biomarkers) that could be attributed to hCSCs (P>0.05 in all cases). No hCSCs could be detected in left ventricular samples 30 days after infusion. Conclusions Intracoronary infusion of 20 million c-kit positive hCSCs in pigs (equivalent to ~40 million hCSCs in humans) does not cause acute cardiac injury, impairment of cardiac function, or liver and renal injury. These results have immediate translational value and lay the groundwork for using doses of CSCs >1 million in future clinical trials. Further studies are needed to ascertain whether administration of >1 million hCSCs is associated with greater efficacy in patients with ischemic cardiomyopathy.

Successful Treatment of Empyema Thoracis with Polymethylmethacrylate Antibiotic-Impregnated Beads in the Guinea Pig

Two hundred nine Duncan-Harley guinea pigs had intrathoracic inoculation with 10(8) Staphylococcus aureus, accompanied by blood and umbilical tape. One hundred fifty-two animals were excluded because of clinical recovery, early death, or complications related to intrathoracic polymethylmethacrylate (PMMA) bead placement. The remaining 57 animals had clinical signs of empyema thoracis and were the subjects of this study. Group I animals (N = 24) served as the controls and had no therapy. Group II animals (N = 14) were treated by intrathoracic placement of placebo PMMA beads. Group III animals (N = 19) were treated by intrathoracic placement of tobramycin sulfate-impregnated PMMA beads. There were no differences between the groups in pleural reaction or pneumonia scores. These findings demonstrate a similar host response to the established infection. Group III, however, had a higher sterilization rate than Groups I and II (p less than 0.05), a finding underlining the therapeutic effect of tobramycin-treated PMMA beads. We conclude that intrathoracic local antimicrobial therapy with slow-release tobramycin-impregnated PMMA beads may enhance empyema treatment by increasing the rate of local sterilization. More experiments are necessary to assess the efficacy of this potentially important therapeutic arm for the treatment of thoracic empyema.