Edward R. Stephenson

Initial United States clinical trial of robotically assisted endoscopic coronary artery bypass grafting

OBJECTIVES With traditional instruments, endoscopic coronary artery bypass grafting has not been possible. This study was designed to determine the clinical feasibility of using a robotically assisted microsurgical system to create endoscopic coronary anastomoses. METHODS AND RESULTS Ten patients underwent endoscopic coronary artery bypass grafting of the left internal thoracic artery to the left anterior descending artery. Subxiphoid endoscopic ports (2 for instruments, 1 for a camera) were placed, and a robotic system was used to perform the left internal thoracic artery-left anterior descending artery bypass graft. Conventional techniques were used to perform the other grafts. Blood flow through the left internal thoracic artery graft was measured in the operating room and was adequate in 8 of 10 patients. The 2 inadequate grafts were revised successfully by hand. Six weeks after the operation, selective coronary angiography demonstrated a graft patency of 100% (8/8). There were no technical failures of the robotic system. The only postoperative complication was mediastinal hemorrhage in 1 patient. CONCLUSIONS This pilot study demonstrates the feasibility of robotically assisted endoscopic coronary artery bypass grafting.

Initial experience with CentriMag extracorporal membrane oxygenation for support of critically ill patients with refractory cardiogenic shock

BACKGROUND Cardiogenic shock refractory to conventional therapy has very high mortality and limited support options. New technology with peripherally inserted CentriMag (Levitronix LLC, Waltham, MA) extracorporal membrane oxygenation (ECMO) may have the potential to significantly improve survival in these critically ill patients. Outcomes of the first 10 patients to receive this device at our institutions are presented. METHODS Patients were identified by their primary physicians and evaluated by our Mechanical Circulatory Support Team. CentriMag ECMO was initiated at the bedside using sterile percutaneous cannulation of femoral vessels. Patients were admitted to the Heart and Vascular Intensive Care Unit, with care managed by regular nursing staff with special training. RESULTS The patients (5 men, 5 women) were a mean age of 45 +/- 18 years, had a mean left ventricular ejection fraction of 30%, and a mean lactate level of 9 mmol/liter. All patients met criteria for shock refractory to medical therapy, but the etiology varied. Average duration of ECMO support was 5.8 +/- 4 days. Survival was 60%. There were no major complications directly related to the device and no equipment malfunctions. CONCLUSIONS The peripherally inserted CentriMag ECMO was easy to insert, functioned without mechanical error, and significantly reduced expected mortality in critically ill patients. Further research will be necessary to develop standardized algorithms and gain more experience, but this new technology has promising potential.

Prospective Clinical Trial of Robotically Assisted Endoscopic Coronary Grafting With 1-Year Follow-Up

ObjectiveTo follow up in prospective fashion patients with coronary artery anastomoses completed endoscopically with robotic assistance. The robotic system was evaluated for safety and its effectiveness in completing microsurgical coronary anastomoses. Summary Background DataRecently there has been an interest in using robotics and computers to enhance the surgeon’s ability to perform endoscopic cardiac surgery. This interest has stemmed from the rapid advancement of technology and the desire to make cardiac surgery less invasive. Using traditional endoscopic instruments, it has not been possible to perform coronary surgery. MethodsNineteen patients underwent robotically assisted endoscopic coronary artery bypass grafting of the left internal thoracic artery (LITA) to the left anterior descending artery (LAD). Two robotic instruments and one endoscopic camera were placed through three 5-mm ports. A robotic system was used to construct the LITA–LAD anastomosis. All other required grafts were completed by conventional techniques. ResultsSeventeen LITA–LAD grafts (89%) had adequate intraoperative flow. The mean LITA–LAD graft flow was 38.5 ± 5 mL/min. At 8 weeks, LITA–LAD grafts were assessed by angiography and showed 100% patency with thrombolysis in myocardial infarction (TIMI) I flow. At a mean follow-up of 17 ± 4.2 months, all patients were NYHA class I and there were no adverse cardiac events. ConclusionsThe results from the first prospective clinical trial of robotically assisted endoscopic coronary bypass surgery in the United States showed favorable short-term outcomes with no adverse events. Robotic assistance is an enabling technology allowing the performance of endoscopic coronary anastomoses.

Development of aortic insufficiency in patients supported with continuous flow left ventricular assist devices.

Development of aortic insufficiency (AI) in patients supported with continuous flow left ventricular assist devices (LVAD) can adversely affect pump performance. In this study, we examined the incidence of new AI after LVAD implant at our institution. Pre- and postoperative echocardiograms of 66 patients who received HeartMate II or Heartware LVAD at our institution since June 2008 were reviewed for presence of new AI. Median LVAD support duration was 221 days. New AI developed in 6 patients (9.5%) after a median time of 374.5 days of support. There were no cases of severe or symptomatic AI. There was no significant difference between the AI incidence between HeartMate II and Heartware recipients. For patients who remained on LVAD support at 6 and 12 months, freedom from AI was 100% and 68.4%, respectively. Age, destination therapy status, and duration of support were predictors of new AI after LVAD implant. In conclusion, AI develops frequently during long-term support with continuous flow LVADs, particularly in those supported for longer than 6 months. As we move to the era of long-term LVAD support and destination therapy, further studies with longer follow-ups are required to determine the progression and clinical significance of AI in these patients.

Computer-assisted endoscopic coronary artery bypass anastomoses: a chronic animal study.

BACKGROUND With traditional instruments, endoscopic coronary artery bypass grafting (ECABG) has not been possible. This study was designed to determine the feasibility of using a robotically-assisted microsurgical system to perform ECABG in a chronic animal model. METHODS Nine calves were placed on cardiopulmonary bypass after harvesting the left internal mammary artery (LIMA). Subxiphoid endoscopic ports (2 instrument, 1 camera) were placed, and a robotic system was used to perform ECABG between the LIMA and left anterior descending coronary artery. LIMA graft flow (LIMAQ) was measured. Animals were sacrificed at 1 month, and hearts underwent angiographic and histologic analyses. RESULTS Acute graft patency was 89% (8/9). Two animals died suddenly within the first 48 hours. There was no significant difference in mean acute and chronic (n = 6) LIMAQ (40.9+/-4.7 and 38.5+/-5.0 ml/min, respectively). Survivors had an angiographic patency rate of 100% (6/6), confirmed by histology. CONCLUSIONS This study shows that ECABG is feasible in a chronic animal model with excellent results.

The Intravenous Anesthetic Propofol Inhibits Human L-Type Calcium Channels by Enhancing Voltage-Dependent Inactivation

Propofol is commonly used to induce anesthesia but has been associated with some negative cardiovascular side effects, including negative inotropy, hypotension, and bradycardia. This study investigated the effect of propofol on L‐type calcium current in acutely isolated human atrial myocytes to better understand the mechanism of these side effects. After informed consent was obtained, the atrial appendage was obtained from patients undergoing open‐heart surgery who required cardiopulmonary bypass. Atrial myocytes were isolated using enzymatic digestion, and L‐type calcium currents were recorded using the whole‐cell patch clamp technique. Propofol enhanced the magnitude and speed of voltage‐dependent inactivation of L‐current. As a result, the propofol‐induced inhibition was increased by protocols that increased inactivation such as longer voltage step duration, holding potential depolarization, and increased pulsing frequency. The preferential enhancement of L‐channel inactivation by propofol can explain the associated cardiovascular side effects. The depolarized resting potential of arterial smooth muscle may render the L‐channels in these cells particularly sensitive to propofol‐induced inhibition, which could explain the hypotension observed in some patients. The enhancement of both inactivation kinetics and steady‐state inactivation by propofol can also explain the negative inotropic effect. However, the enhanced voltage‐dependent inactivation and use dependence could have beneficial effects for patients prone to certain arrhythmias and tachycardia.

Successful treatment of peripartum cardiomyopathy with extracorporeal membrane oxygenation

A 24-year-old female developed heart failure within four months of delivering her first child. Echocardiogram revealed a moderately dilated left ventricle with severely reduced systolic function. She continued to decompensate, requiring intubation and inotropic support. When the use of an intra-aortic balloon pump failed to stabilize the patient, the decision was made to place her on ECMO. The circuit consisted of a Quadrox D membrane oxygenator and a CentriMag® centrifugal pump. After 11 days of support, the patient met the weaning criteria and was successfully removed from ECMO. She was discharged one month after her admission. The new technology available allows for ECMO to be considered as an earlier option for the treatment and management of these patients as a bridge to recovery.

Comparison of Hemolysis Between CentriMag and RotaFlow Rotary Blood Pumps During Extracorporeal Membrane Oxygenation

The purpose of this investigation was to compare the hemolysis levels for patients on extracorporeal membrane oxygenation (ECMO) incorporating two different rotary blood pumps (CentriMag [CMAG] and RotaFlow [RF]) in identical circuits otherwise. The difference between the two pumps is the cost. One is 20-30 times less expensive than the other. A retrospective analysis of all patients placed on ECMO from June 2008 through May 2012 was done to evaluate hemolysis. Daily plasma hemoglobin (pHb), lactate dehydrogenase (LDH), and lactate levels were collected on all patients. Values were compared between those patients who received a CMAG and those who received an RF. Patients had to be on ECMO for more than 2 days to be included in the study. Linear mixed effects models were fit to the data to assess differences over time for each continuous outcome. Forty patients were placed on ECMO incorporating CMAG, whereas 40 patients received an RF. There were no significant statistical differences between CMAG and RF groups when comparing days on support (8.7 ± 5.0; 8.4 ± 5.7), age (44.8 ± 18.3; 46.1 ± 16.0), body surface area (2.03 ± 0.36; 1.96 ± 0.31), gender (male: 58%, female: 42%; male: 55%, female: 45%), etiology, type of support (veno-arterial [VA)]: 78%, veno-venous [VV)]: 22%; VA: 82%, VV: 18%) and pre-ECMO LDH levels (4004.0 ± 3583.2; 3603.7 ± 3354.1). There were also no significant differences between the CMAG and RF groups when comparing the mean values for daily pHb levels (5.7 ± 3.6; 5.7 ± 4.2), lactate levels (2.8 ± 1.9; 3.0 ± 2.1), and LDH levels (2656.3 ± 1606.8; 2688.6 ± 1726.1) or daily lactate, LDH, and pHb levels for the first 10 days of support. From our investigation, there is no difference between the CMAG and the RF blood pumps in regard to the creation of hemolysis during ECMO. The difference in cost of the devices does not correlate with the performance and outcomes.

Clinical Experience With Sternotomy Versus Subcostal Approach for Exchange of HeartMate II Left Ventricular Assist Device

BACKGROUND The safety and efficacy of exchanging the HeartMate II (Thoratec Corp, Pleasanton, CA) left ventricular assist device (LVAD) through a less invasive subcostal approach remains unclear. METHODS We reviewed the records of 17 patients who underwent exchange of their HeartMate II device at our institution since 2007. We divided the cohort into devices exchanged through a subcostal (SC) approach versus a median sternotomy (MS) approach and obtained data pertaining to the short- and long-term outcomes. RESULTS Nine patients had pump exchange through an MS approach versus 8 patients who underwent an SC approach. The mean duration of support with the first pump was 540 ± 450 days. The reason for exchange was electromechanical failure (7 patients), thrombosis (8 patients), and infection (2 patients). There were no 30-day perioperative deaths with either approach. Compared with sternotomy, patients who underwent an SC approach had significantly shorter operative times (131 vs 222 minutes; p = 0.001) and lower reoperation rates for bleeding (0 vs 44.4%; P = 0.05) and required fewer transfused blood products (packed red cells, 3.5 units vs 7.1 units; p < 0.05; cryoprecipitate, 50.7 mL vs 209.3 mL; p = 0.01; and platelets, 292 mL versus 762 mL; p < 0.05). Additionally, patients who underwent an SC approach had shorter postoperative stays in the intensive care unit (ICU) (5 days vs 13.8 days; p < 0.05) and shorter total hospital stays (16.4 days vs 27.2 days; p < 0.05). Long-term survival after mean follow-up of 260 days for the SC group and 232 days for the sternotomy group was 75% and 33%, respectively. CONCLUSIONS Exchange of the HeartMate II pump can be accomplished with low morbidity and mortality and good long-term outcomes through a less invasive SC approach.

End-organ recovery is key to success for extracorporeal membrane oxygenation as a bridge to implantable left ventricular assist device.

Preexisting organ dysfunctions are known factors of death after placement of implantable mechanical circulatory support (MCS). Extracorporeal membrane oxygenation (ECMO) may able to stabilize organ function in patients with cardiogenic shock before MCS implantation. Between 2008 and 2012, 17 patients with cardiogenic shock were supported with ECMO before implantable MCS placement. Patient’s end-organ functions were assessed by metabolic, cardiac, hepatic, renal, and respiratory parameters. Survival data after MCS implantations were analyzed for overall survival to discharge, complications, and breakpoint in days on ECMO to survival. Before MCS implantation, lactate, hepatic, and renal functions were improved and pulmonary edema was resolved. The interval between ECMO initiation and MCS placement was 12.1 ± 7.9 days. Overall survival rate to discharge after left ventricular assist device/total artificial heart placement was 76%. The survival of patients transitioned from ECMO to MCS within 14 days was 92% and was significantly better than the survival of patients from ECMO to MCS supported longer than 14 days, 25%, p < 0.05. ECMO support can immediately stabilize organ dysfunction in patients with cardiogenic shock. After improvement of organ function, MCS implantation should be done without delay, since the patients supported for longer than 14 days with ECMO had inferior survival compared to national data.