Human heart conjugate cooling simulation: unsteady thermo-fluid-stress analysis.

The main objective of this work was to demonstrate computationally that realistic human hearts can be cooled much faster by performing conjugate heat transfer consisting of pumping a cold liquid through the cardiac chambers and major veins while keeping the heart submerged in cold gelatin filling a cooling container. The human heart geometry used for simulations was obtained from three-dimensional, high resolution CT-angio scans. Two fluid flow domains for the right (pulmonic) and left (systemic) heart circulations, and two solid domains for the heart tissue and gelatin solution were defined for multi-domain numerical simulation. Detailed unsteady temperature fields within the heart tissue were calculated during the conjugate cooling process. A linear thermoelasticity analysis was performed to assess the stresses applied on the heart due to the coolant fluid shear and normal forces and to examine the thermal stress caused by temperature variation inside the heart. It was demonstrated that a conjugate cooling effort with coolant temperature at +4°C is capable of reducing the average heart temperature from +37°C to +8°C in 25 minutes for cases in which the coolant was steadily pumped only through major heart inlet veins and cavities.

A novel approach to ICD lead revision in a patient with extensive vascular thrombosis.

Chronic extensive thrombosis of the venous system is a commonly encountered problem in end stage renal disease (ESRD) patients undergoing transvenous device implantation, lead extraction or lead revision. We describe a case of an ESRD patient with an implantable cardioverter defibrillator (ICD) that failed to deliver therapy due to lead fracture. Patient needed revision of the ICD lead system, but had extensive axillary-subclavian-superior vena cava occlusion. Patient refused a thoracotomy approach as well as lead extraction as he had a complicated course of lead extraction in the past. We successfully improvised a novel technique to revise the ICD system.

Quantification of tryptophan transport and metabolism in lung tumors using PET.

UNLABELLED: Abnormal tryptophan metabolism catalyzed by indoleamine 2,3-dioxygenase may play a prominent role in tumor immunoresistance in many tumor types, including lung tumors. The goal of this study was to evaluate the in vivo kinetics of alpha-(11)C-methyl-l-tryptophan (AMT), a PET tracer for tryptophan metabolism, in human lung tumors. METHODS: Tracer transport and metabolic rates were evaluated in 18 lesions of 10 patients using dynamic PET/CT with AMT. The kinetic values were compared between tumors and unaffected lung tissue, tested against a simplified analytic approach requiring no arterial blood sampling, and correlated with standardized uptake values (SUVs) obtained from (18)F-FDG PET/CT scans. RESULTS: Most non-small cell lung cancers (NSCLCs) showed prolonged retention of AMT, but 3 other lesions (2 benign lesions and a rectal cancer metastasis) and unaffected lung tissue showed no such retention. Transport and metabolic rates of AMT were substantially higher in NSCLCs than in the other tumors and unaffected lung tissue. A simplified analytic approach provided an excellent estimate of transport rates but only suboptimal approximation of tryptophan metabolic rates. (18)F-FDG SUVs showed a positive correlation with AMT uptake, suggesting higher tryptophan transport and metabolism in tumors with higher proliferation rates. CONCLUSION: Prolonged retention of AMT in NSCLCs suggests high metabolic rates of tryptophan in these tumors. AMT PET/CT may be a clinically useful molecular imaging method for personalized cancer treatment by identifying and monitoring patients who have increased tumor tryptophan metabolism and are potentially sensitive to immunopharmacotherapy with indoleamine 2,3-dioxygenase inhibitors.

Successful management of recalcitrant groin lymphorrhoea with the combination of intraoperative lymphatic mapping and muscle flap.

Recalcitrant groin lymphorrhoea in high-risk patients remains a problem. In this report, a cardiac transplant patient with recalcitrant groin lymphorrhoea was successfully treated with a combination of intraoperative lymphatic mapping and sartorius muscle flap. We believe that the combined use of these two treatment options offers a more effective approach for surgical treatment of recalcitrant groin lymphorrhoea and should be considered when managing this difficult clinical problem, especially in high-risk patients.

Methemoglobinemia secondary to topical benzocaine use in a lung transplant patient.

OBJECTIVE: To report a case of methemoglobinemia secondary to the administration of topical benzocaine spray in an anemic patient who had previously undergone a lung transplant. CASE SUMMARY: A 40-year-old white man with a past medical history significant for lung transplant acutely decompensated following oropharyngeal administration of topical benzocaine spray. Subsequent blood analysis revealed a methemoglobin concentration of 51.2%. Following the administration of a single dose of methylene blue 2 mg/kg intravenously, the patient's respiratory status dramatically improved and stabilized. DISCUSSION: Methemoglobinemia is a rare but potentially fatal condition that may be either acquired or congenital; however, the disorder is most commonly acquired secondary to exposure to oxidizing chemicals, which are often routinely prescribed medications, including benzocaine. Benzocaine can react with hemoglobin to form methemoglobin at a rate that exceeds reduction capabilities, which may result in oxygenation difficulty and respiratory distress. In severe or symptomatic methemoglobinemia, the treatment of choice is methylene blue. CONCLUSIONS: Application of the Naranjo probability scale established a highly probable relationship between topical benzocaine spray and methemoglobinemia and associated respiratory compromise. The risks of palliative use of topical benzocaine in patients with preexisting disorders that compromise oxygen delivery may outweigh any benefit. In our patient, anemia and lung disease increased his risk for clinically significant adverse respiratory events secondary to deficiencies or interferences in oxygen delivery. Topical benzocaine should be administered with caution and careful monitoring in such patient populations.

Successful treatment of refractory bleeding after bridging from acute to chronic left ventricular assist device support with recombinant activated factor VII.

Cardiac surgery often is associated with a significant disruption of the coagulation system, particularly in high risk patients such as those undergoing placement of ventricular assist devices. This type of severe coagulopathy can lead to life threatening bleeding that can require massive transfusions to restore hemostasis. Recently, recombinant activated factor VII (rFVlla) has been +used as an alternative to massive transfusion for the treatment of refractory bleeding in several patient populations, including cardiac surgery patients. In the case reported here, the patient's risk was compounded by multiple operations in a short period of time and circulatory collapse that was initially managed with a shortterm left ventricular assist device. After multiple failed attempts at weaning the patient from circulatory assistance, he was taken back to the operating room for conversion to a chronic, implantable device. This procedure was complicated by a severe coagulopathy secondary to a myriad of factors commonly encountered after the use of cardiopulmonary bypass. The administration of rFVlla resulted in a rapid cessation of bleeding without thrombotic complications. This is the first case reported involving an acute to chronic bridge patient. Despite the anecdotal success of rFVlla, further clinical research is needed to establish both the safety and economic feasibility of this agent.

Recombinant factor VIIa for refractory bleeding following orthotopic heart transplantation.

OBJECTIVE: To report a case of successful use of recombinant factor VIIa (rFVIIa) for the treatment of refractory bleeding in a patient undergoing orthotopic heart transplantation. CASE SUMMARY: A 57-year-old white male with idiopathic cardiomyopathy was taken to the operating room for explantation of his left-ventricular assist device and orthotopic heart transplantation. He experienced excessive generalized oozing that required transfusions of multiple units of blood products and significant amounts of Cellsaver (washed red blood cells via autotransfusion) without achieving adequate hemostasis. After ruling out any obvious surgical sources of bleeding and attempting to correct all coagulation deficiencies, the clinicians administered rFVIIa 90 microg/kg. The oozing rapidly declined to a negligible level, chest tubes and sternal wires were placed, and the chest was closed. The patient was on minimal inotropic support and was transferred to the intensive care unit in stable condition. DISCUSSION: Cardiac surgery is often associated with significant disruption of the coagulation system, particularly in high-risk patients, such as those undergoing removal of a ventricular assist device and subsequent orthotopic heart transplantation. This can lead to life-threatening bleeding that can require multiple hemostatic agents and significant transfusions to restore hemostasis. Recently, rFVIIa has been utilized as an alternative to massive transfusion for treatment of refractory bleeding in several patient populations, including some cardiac surgery patients. CONCLUSIONS: rFVIIa appears to be a viable option as rescue therapy for treatment of refractory bleeding following orthotopic heart transplantation. Despite the anecdotal success of rFVIIa in this setting, further clinical research is needed.

Effects of in vivo myocardial ischemia and reperfusion on interstitial nitric oxide metabolites.

BACKGROUND: There have been numerous studies examining the role of nitric oxide (NO) in myocardial ischemia-reperfusion injury; however, few studies have included measurements of NO or related reactive nitrogen species. The purpose of this study was to determine the effects of in vivo regional myocardial ischemia on interstitial fluid (ISF) reactive nitrogen species. METHODS: Open chest pigs were submitted to one of three protocols: (1) 15 minutes coronary occlusion and 2 hours reperfusion, (2) 60 minutes coronary occlusion and 2 hours reperfusion, or (3) two-cycle ischemic preconditioning (IPC) followed by prolonged ischemia and 2 hours reperfusion. The stable NO metabolites, nitrite plus nitrate (NOx), in cardiac microdialysis samples were measured by ozone chemiluminescence. RESULTS: NOx concentration decreased 40% +/- 6% (p < 0.05) during brief ischemia but returned to baseline during reperfusion. Dialysate NOx levels decreased further after 60 minutes ischemia (60% +/- 3% of baseline, p < 0.01) but reperfusion dialysate NOx concentration increased 34% +/- 9% above baseline (p < 0.05). Preconditioning did not increase dialysate NOx but did accelerate the ischemia-induced decrease in NOx levels (p < 0.05). Reperfusion NOx levels in preconditioned pigs were significantly lower than in nonpreconditioned pigs (p < 0.05). CONCLUSIONS: These results suggest that ischemia is associated with decreased ISF NOx concentration. Reperfusion NOx levels are increased after prolonged ischemia, an effect that is significantly blunted by ischemic preconditioning.

Heart transplants: need versus availability.

Every year in the US heart failure accounts for roughly 60,000 deaths and is the contributing cause in another 300,000 deaths. The two-year survival rate for patients with advanced heart failure is less than 50%, with the incidence of death at 106 in 100,000, more than that for AIDS and breast cancer combined. As these figures attest, the economic burden is quite extensive. The Centers for Medicaid and Medicare estimate a cost of $10 billion a year for this diagnosis alone. Both the human and financial cost have impelled doctors and researchers to improve their capacity to treat heart failure both through conventional methods and, in the most serious cases, through transplantation. Many pioneers have either directly or indirectly contributed to our ability to treat heart failure. Among these early researchers were: Dr Alexis Carrel, who was awarded the Nobel Prize for his pioneering work in vascular anastomosis; Dr John Gibbon, who did important work in the development of the cardiopulmonary bypass machine; Drs Normal Shumway, Richard Lower, and Demikhov, who developed heart transplant procedures in the canine model; Dr Christian Barnaard, who performed the first technically successful human-to-human heart transplant (1967); and Dr Thomas Hardy, who attempted the first xenotransplant (1963). While these achievements were phenomenal advances, long-term survival for transplant recipients was minimal until progress was made in immunosuppressive techniques.