Centrifugal pump failures.

Centrifugal pumps will not pass gross quantities of gaseous emboli due to the nonocclusive nature of the pump. However, retrograde flow can occur under circumstances that include: product malfunctions, low flows, and human errors. Negative pressure created by falling arterial perfusate can draw air into the cannula. Food and Drug Administration (FDA) records about centrifugal pump malfunctions were obtained. Out of 350,000 cases completed with centrifugal pumps over a 23 month period, the FDA received reports of 68 malfunctions, 22 electrical burning smells, and three speed surges, yielding a failure rate of 1 in 3,763 cases. FDA records revealed five death reports and three serious injury reports. A survey was sent to 2,424 Society of Thoracic Surgeons' members to obtain more information; 285 who use centrifugal pumps responded. Sixty surgeons (21%) reported 108 malfunctions, including 46 complete pump failures. Fifty-one of 243 surgeons (21%) who use centrifugal pumps for bypass reported that perfusionists have forgotten to clamp the pump line, resulting in backflow. We conclude centrifugal pumps are generally safe, but malfunctions, low flows, and human errors can lead to retrograde flow and occasionally air embolization. There are valves that can be added to the bypass circuitry to prevent this risk.

Transmyocardial laser revascularization: clinical experience with twelve-month follow-up.

We are investigating a new technique for myocardial revascularization in which an 800 W carbon dioxide laser is used to drill 1 mm diameter channels into a beating heart after left thoracotomy. Clotting occludes the channels on the subepicardium, and in the long-term setting, blood from the left ventricular cavity flows through these channels to perfuse the ischemic subendocardium. To test the efficacy of this technique in a preliminary clinical trial, we used it as sole therapy for 21 consecutive patients. All patients had hibernating myocardium, reduced coronary flow reserve, or both, had distal diffuse coronary artery disease, and had angina refractory to normal therapy. Eight patients were excluded from follow-up because of death (n=5), rerevascularization (n=2), or diaphragmatic paralysis resulting in postoperative respiratory incapacity (n=1). In the remaining 13 patients available for follow-up, the mean angina class (Canadian Cardiovascular Society) was 3.7 +/- 0.4 before operation and 1.8 +/- 0.6 12 months after operation (p < 0.01). Mean resting left ventricular ejection fraction was 48% +/- 10% before operation and 50% +/- 8% at 12-month follow-up. At 12 months, resting mean subendocardial/subepicardial perfusion ratio had increased by 20% +/- 9% in septal regions treated by laser but decreased by 2% +/- 5% in untreated regions (n=11, p <.001). These results suggest that revascularization by this laser technique positively affects subregional myocardial perfusion and may result in clinical benefits for patients with reversible myocardial ischemia. Studies to date have not demonstrated significant changes in global and regional ventricular contractile function.

Five month survival in a calf supported with an intraventricular axial flow blood pump.

We are studying in vivo an intraventricular axial flow blood pump (Jarvik 2000) designed for long-term left ventricular support. The small (25 cc, 85 g) valveless pump has been placed intraventricularly in seven calves; pumps have functioned for as long as 5 months. In the four most recent long-term studies completed, calves have survived for 70, 120, 155, and 162 days (in that order); weight gain has averaged 0.56 kg/day. One study is ongoing at more than 30 days. Under resting physiologic conditions in the normal calf, the continuous flow pump produces flows of 5-6 L/min with a decreased arterial pulse contour. The device has caused no physiologic complications. Calves in the completed studies had mean free plasma hemoglobin levels of 11.4, 7.1, 6.5, and 4.3 mg/dl, respectively. We have modified the inflow structures of the device, and these results suggest that a thrombus free design with no pannus at or around the inlet of the pump can be achieved. Histopathologic analyses of the heart and kidneys in studies of as long as 5 months show no deleterious effects of this device. These studies demonstrate the feasibility of a small implanted intraventricular blood pump for long-term use. Future developments for permanent implantation will include implanted physiologic control systems, transcutaneous energy transmission systems, and implanted batteries.

Physician understanding of the National Practitioner Data Bank.

National Practitioner Data Bank (NPDB) reports are part of the process for acquiring staff privileges, professional credentials, and licenses throughout a physician's entire career. We surveyed our hospital's 66 residents to assess their understanding of NPDB. Only 9 residents had heard about NPDB. A follow-up survey of the 10 medical schools in Pennsylvania and Maryland showed just 4 schools covered NPDB in their curricula. Finally, we did a third survey--of 1,410 Pennsylvania Medical Society members. Eighty-one percent did not know that denial of initial license application was not a reportable offense; 69% did not know that voluntary entrance into alcohol/drug rehabilitation was not reportable; and 75% did not know that denial of expanded privileges because of level of clinical competence was reportable. Only 13% knew how to obtain their files. Our surveys suggest physicians have a poor understanding of NPDB even though these reports could have career-jeopardizing implications, especially if the Clinton administration expands access to NPDB.

Results of the unidirectional Centri-Safe arterial valve for prevention of retrograde flow during cardiopulmonary bypass.

Retrograde blood from the aortic cannula into the cardiopulmonary circuit may lead to aortic air emboli when nonocclusive centrifugal pumps are used. The authors tested a nonregurgitant, unidirectional valve containing a Teflon ball occluder to prevent backflow. In vitro measurements of leakage rate, forward flow pressure drop, burst strength, and hemolysis levels along with animal (n = 12) and human (n = 12) in vivo hematologic and hemolysis levels were measured. Data were analyzed by paired and unpaired Student's t-test. Pressure drop differences at flows of 5 l/min were 7.3 +/- 0.3 mmHg before and 7.6 +/- 0.1 mmHg after 10,800 cycles of pulsatile pumping. (P = NS). Leakage rate during this period at pressures of 100 mmHg was not significant. Volume required to close the Teflon ball was less than 1 ml. Hemolysis analysis done in vitro and in vivo in control (no valve) and experimental (valve) groups used hemoglobin, hematocrit, platelets, plasma free hemoglobin, and lactic dehydrogenase as hemolysis indices. There were no statistical differences. The authors conclude that the CentriSafe valve (Cardiac Systems, Inc., Conshohocken, PA) is safe and prevents fatal backflow and air emboli. The valve is nonthrombotic in anticoagulated blood, can be opened and closed thousands of times, and has a burst strength equal to or greater than other components in the perfusion setup.

New technique for coronary sinus cannulation using a fiberoptic stylet.

Fluoroscopy, echocardiography, blind digital approach, and direct visual insertion have been used for retrograde cannulation of the coronary sinus. We cannulate the coronary sinus by transillumination using a standard flexible retroplegia cannula with a reusable fiberoptic stylet designed by our open heart program. An attachable light source illuminates the tip, which is guided into the coronary sinus ostium. We have used the technique in 16 patients who could not be cannulated with the blind digital method.

Management of patent saphenous vein grafts during reoperative coronary artery bypass grafting.

A patient was referred for coronary artery bypass reoperation. After a left internal mammary artery was grafted to the left anterior descending coronary artery, the diseased but patent old saphenous vein graft was ligated. This resulted in severe myocardial failure, which was corrected only after restoration of flow through the old vein graft. We suggest the decision to ligate or replace an old vein graft should be individualized to avoid the risk of myocardial ischemia.

New approaches for cardiac assists: "back to the future".

The treatment of the modern epidemic of coronary artery disease requires the availability of various cardiac assist devices. A review and future implications of the use of retrograde coronary venous perfusion, the intraaortic balloon, a new ascending aortic pump, variable atrial septal defect, and novel energy sources are discussed.

Endomyocardial biopsy: variations in venous access for endomyocardial biopsy in cardiac transplantation.

With the increasing number of cardiac transplantation procedures performed worldwide, a strategy for endomyocardial biopsy techniques has evolved at our institution. Specific approaches for venous access for biopsy purposes are described. These include approaches via the right internal jugular vein, right external jugular vein, left subclavian vein, and the femoral veins. Particular emphasis is placed on the technical nuances of each approach. In approximately 2,000 endomyocardial biopsies performed on 155 transplant patients from 1984-1989, only two major complications occurred, only one of which required operative intervention. This was a perforated right ventricle, and the patient recovered after repair without further sequelae. No pneumothoraces or infection occurred during this time period. With proper understanding of regional anatomy, fluoroscopic appearance, and experience, endomyocardial biopsies can be performed with an extremely low incidence of major or minor complications.

Successful heart transplantation in recipients with recent preoperative pulmonary emboli.

Acute pulmonary embolus (less than 6 weeks old) has been considered an absolute contraindication to heart transplantation for fear of the potential problems of lung abscess, empyema, bronchopleural fistula, and systemic sepsis in an immunosuppressed patient. It is difficult to adhere to this principle because 30% to 50% of patients with dilated cardiomyopathy may have an acute pulmonary embolus and would be excluded from transplantation. Several centers have considered such patients for heart transplantation if they are young, on maximal medical therapy, and in extremis. The surgical management of the postoperative pulmonary problems can include bronchoscopy, antibiotics, surgical drainage, decortication, and pulmonary resection with or without muscle flaps. We describe our approach to two such patients who were managed successfully with lobectomies and latissimus dorsi muscle flaps to seal the bronchus and fill the pleural space.

New polyurethane valves in new soft artificial hearts.

This article describes new bistable valves, and introduces a new soft heart that is easy to implant. Earlier, five polyurethane (PU) valves were implanted in the mitral position in sheep. All five survived for 1 year or more, and the valves, although calcified, were intact. Since the opening resistance was somewhat high, valves that are bistable were developed, which means they may be open or closed. These valves have lower opening resistance, and regurgitation is similar to that of mechanical valves. Eight calves have been implanted with a new, soft total artificial heart (TAH). Seven had bistable leaflet valves; the eighth had mechanical (Bicer) valves in the inflow position. Four of the calves were sacrificed after 22 to 43 days. At autopsy, the number of thromboemboli found, particularly in the kidneys, was low compared with previous experiments. None of these animals received anticoagulants other than the heparin given during heart/lung bypass.

Development of the Philadelphia Heart System.

A new pneumatic artificial heart system has been developed. The design criteria have been to produce an integrated series of blood pumps and drive systems that would reduce blood trauma and reactivity, while incorporating industrial, mass-production techniques. The system attempts to reproduce the natural heart's pressure and flow waveforms and allows the prosthetic valves to be installed in a manner consistent with their design. The system's ventricles are constructed entirely of polyurethane by a combination of vacuum-forming and solution-casting techniques. The atrial cuffs and arterial grafts are permanently attached to the pumps and do not incorporate a quick connect system. The prosthetic valves are sewn into the inflow and outflow tracts using their clinical sewing rings. Besides eliminating the crevices normally found in quick connect systems, this method mounts the valves in an extremely compliant housing to increase shock absorption. The drive system produces a systolic air flow with a variable pressure rise (dP/dt) to reduce mitral valve closing velocity. This system has been implanted into 25 calves to date, of which 17 were chronic experiments. In 14 animals, St. Jude bileaflet valves were used and these animals had a mean survival of 39 days. Six of these animals survived over 30 days, with the longest being 129 days. All of the animals showed the characteristic postoperative drop in red blood cell count and hematocrit that returned to near preoperative values in about 3 weeks. The plasma free hemoglobin values generally remained below 5 mg/dl. The necropsies performed on several of the earlier animals revealed renal infarcts. However, in two of the later experiments, no kidney damage was found. The blood contacting surfaces of the atrial cuffs from the animals surviving over 100 days were covered with a fibroproliferative pseudoneointimal growth that extended from the sewing rings to the natural atrial tissue. Grossly, this appears to be the same type of tissue response seen when only a valve is implanted in a natural calf heart.

Sternotomy closure with Parham bands.

The closure of a median sternotomy incision requires secure bony approximation to prevent postoperative pain, sternal click, and/or nonunion of bone. The standard technique of sternotomy closure involves the use of stainless steel wires for reapproximation of the sternum. These wires occasionally break or pull through bone, resulting in instability of either a portion of the sternum or the entire sternum. Presented here is our technique for sternotomy closure that provides secure closure with reduced postoperative morbidity.