Mechanism of coronary microvascular responses to metabolic stimulation.

UNLABELLED: Previous studies from our laboratory have shown that coronary microvascular dilation to increased myocardial oxygen consumption (MVO2) is greater in vessels < 100 microns. The mechanism responsible for this response is uncertain. OBJECTIVES: We tested the hypothesis that microvascular dilation to increased MVO2 is mediated by nitric oxide (NO). Since NO release may occur in response to increased shear, we also tested the hypothesis that metabolic byproducts released in response to increase in MVO2 will stimulate opening of the ATP-sensitive potassium channel. METHODS: Changes in epicardial coronary microvascular diameters were measured in 9 dogs given NG-nitro-L-arginine (LNNA; 100 microM, topically), 7 dogs given glibenclamide (10 microM, topically) and 12 control (C) dogs during increases in metabolic demand using dobutamine (DOB, 10 micrograms/kg/min, i.v.) with rapid atrial pacing (PAC, 300 bpm). Diameters of arterioles were measured using intravital microscopy coupled to stroboscopic epi-illumination. RESULTS: During the protocol, MVO2 increased to a similar degree in both experimental groups (LNNA and glibenclamide). Baseline hemodynamics and coronary microvascular diameters were similar between the two experimental groups and their respective control groups. In the presence of LNNA, coronary arteriolar (< 100 microns) dilation (% change from baseline) was impaired during the protocol (DOB: vehicle 18 +/- 5, LNNA 2 +/- 2 [P < 0.05]; DOB + RAP: vehicle 40 +/- 11, LNNA 6 +/- 2% [P < 0.05]). In contrast, glibenclamide did not impair coronary microvascular responses to increased MVO2 despite increases in MVO2. CONCLUSION: This study indicates that coronary microvascular dilation in response to increased metabolic stimulation using dobutamine in conjunction with rapid pacing is mediated through a nitric-oxide-dependent mechanism and not ATP-sensitive potassium channels. These results may have important implications in pathological disease states where nitric oxide mechanisms are impaired, such as diabetes and hypertension.

Influenza A pneumonitis following treatment of acute cardiac allograft rejection with murine monoclonal anti-CD3 antibody (OKT3).

A 51-year-old man developed fever, cough, and dyspnea 5 days after completing murine monoclonal anti-CD3 antibody (OKT3) treatment for acute cardiac allograft rejection. Samples of BAL fluid grew influenza A virus. Progressive pulmonary infiltrates, respiratory compromise, and hypoxia developed, and the patient ultimately required 5 days of mechanical ventilation. Treatment with amantadine hydrochloride and ribavirin was prescribed, and the patient was discharged after 19 days. Influenza A virus has not been an important pathogen in cardiac transplant recipients. However, this is the first reported case of influenza A pneumonitis complicating anti-T lymphocyte therapy for cardiac allograft rejection. In comparison with our patient, two previously reported cases of influenza A infection in cardiac transplant patients have been less severe. The virulence of our patient's, life-threatening infection appears to be secondary to impairment of T lymphocyte-mediated immunity by OKT3. The role of therapeutic and even prophylactic amantadine therapy in this clinical setting has yet to be determined.

Age-related effects of St Thomas' Hospital cardioplegic solution on isolated cardiomyocyte cell volume.

OBJECTIVES: We tested the hypothesis that neonatal cells are more sensitive to cardioplegia-induced cell swelling than more mature cells and spontaneous swelling in the absence of ischemia can be prevented by cardioplegia with a physiologic KCl product. METHODS: Cell volumes of isolated ventricular myocytes from neonatal (3-5 days), intermediate (10-13 days), and adult (>6 weeks) rabbits were measured by digital video microscopy. After equilibration in 37 degrees C physiologic solution, cells were suprafused with 37 degrees C or 9 degrees C St Thomas' Hospital solution (standard or low Cl(-)) or 9 degrees C physiologic solution followed by reperfusion with 37 degrees C physiologic solution. RESULTS: Neonatal cells swelled 16.2% +/- 1.8% (P <.01) in 37 degrees C St Thomas' Hospital solution and recovered during reperfusion, whereas more mature cells maintained constant volume. In contrast, 9 degrees C St Thomas' Hospital solution caused significant age-dependent swelling (neonatal, 16.8% +/- 1.5%; intermediate, 8.6% +/- 2.1%; adult, 5.6% +/- 1.1%). In contrast to more mature cells, neonatal cells remained significantly edematous throughout reperfusion (8.1% +/- 1.5%). Swelling was not due to hypothermia because 9 degrees C physiologic solution did not affect volume. Lowering the KCl product of St Thomas' Hospital solution by partially replacing Cl(-) with an impermeant anion prevented cellular edema in all groups. CONCLUSION: In the absence of ischemia, neonatal cells were more sensitive to cardioplegia-induced cellular edema than more mature cells, and edema observed in all groups was avoided by decreasing the KCl product of St Thomas' Hospital solution to the physiologic range. Differences in cell volume regulation may explain the sensitivity of neonatal hearts to hyperkalemic cardioplegic arrest and suggest novel approaches to improving myocardial protection.

The epidemiology of hemorrhage related to cardiothoracic operations.

OBJECTIVE: To define the epidemiology, risk factors, and unadjusted cost of hemorrhages related to cardiothoracic operations. STUDY DESIGN: We conducted two case-control studies to evaluate the risk of hemorrhage following cardiothoracic operations. The definition of hemorrhage required one of the following: reoperation for bleeding, postoperative loss of greater than 800 mL of blood over 4 hours, or surgeon-diagnosed excessive intraoperative bleeding. SETTING: The cardiothoracic surgery service of a university hospital. RESULTS: Of 511 patients undergoing cardiothoracic operations, 93 (18%) met the definition of hemorrhage. In the first case-control study, 3 (14%) of 21 cases and 0 of 42 controls died (odds ratio [OR], 15.0; 95% confidence interval [CI95], 1.18-191.55). Compared with controls, cases received significantly more packed red blood cells intraoperatively (OR, 1.18/100 mL; CI95, 1.01-1.38), and significantly more platelets (OR, 3.26/100 mL; CI95, 1.47-7.26) and fresh frozen plasma (OR, 1.73/100 mL; CI95, 1.05-.84) in the intensive-care unit. Cases were more likely than controls to receive protamine postoperatively (OR, 3.74; CI95, 1.27-11.02). Previous sternotomy, preoperative aspirin or heparin, and preoperative laboratory values did not predict bleeding. The median unadjusted hospital cost was $3,458 higher for patients who suffered hemorrhage than for controls. To decrease costs, hetastarch (acquisition cost $45/500 mL) was substituted for albumin (acquisition cost $76/100 mL) in the pump priming solution (estimated possible cost savings, $7,000-$53,000/year). Because hemorrhage rates increased subsequently, we conducted a second case-control study that identified patient age (P=.02) and use of greater than 5 mL/kg of hetastarch (OR, 1.82) as risk factors for hemorrhage. The cost of treating hemorrhages exceeded all estimates of possible cost savings ($7,000-$53,000 per year). CONCLUSIONS: Our definition of hemorrhage identified patients who required increased volumes of blood products and who had an increased crude mortality rate and a higher unadjusted cost of hospitalization. Patient age and hetastarch use were risk factors for hemorrhage. Efforts to save money by substituting less expensive products inadvertently may increase costs by increasing the probability of perioperative adverse events.

Electron beam computed tomography: use in pulmonary embolectomy.

Proximal chronic pulmonary emboli with severe pulmonary hypertension were diagnosed by electron-beam computed tomography and Doppler echocardiography. After successful embolectomy, repeat examinations showed normal pulmonary artery pressures and patency. Electron beam computed tomography can noninvasively identify surgically treatable pulmonary emboli.

Contrast MR of the brain after high-perfusion cardiopulmonary bypass.

PURPOSE: To study the efficacy of contrast MR imaging in the evaluation of central nervous system complications in the cardiopulmonary bypass patient and attempt to explain their pathophysiology based on the MR appearance and the cardiopulmonary bypass protocol. METHOD: Nineteen patients were prospectively studied with contrast MR examinations the day before and 3 to 7 days after cardiopulmonary bypass, to determine the nature, extent, and number of new postoperative MR abnormalities. Cardiopulmonary bypass parameters used in our institution included: membrane oxygenation, arterial filtration with a pore size of 25 microns, and a relatively high perfusion rate to produce a cardiac index of 2.0 to 2.5 L/min per m2. RESULTS: The preoperative noncontrast MR examination showed age-related changes and/or signs of ischemia in 60% of patients on the day before surgery. However, there was no abnormal enhancement or new T2 abnormalities on any postoperative MR examination to suggest hypoperfusion or emboli. None of the 19 patients developed overt neurologic deficits postoperatively. Review of the cardiopulmonary bypass protocol used indicated significant variations in technique at different institutions. CONCLUSION: Contrast MR imaging demonstrated no new abnormalities in patients after cardiopulmonary bypass performed with strict in-line arterial filtration and relatively high perfusion. MR imaging is feasible in the early postoperative period after cardiopulmonary bypass and may offer a convenient method for evaluation of the neurologic impact of technical factors associated with cardiopulmonary bypass.

Modified Cabrol's technique for composite replacement of the aortic valve and ascending aorta.

Composite replacement of the ascending aorta and aortic valve with coronary reimplantation can be complicated by intraoperative hemorrhage from the coronary ostial anastomoses and proximal aortic suture line. Exposure and repair of these suture lines may be quite difficult after the termination of bypass in the intact aortic root. Cabrol originally described connecting the coronary ostia by separate Dacron graft, which was then anastomosed side-to-side to the aortic conduit, and the entire repair wrapped in the aneurysm wall to control bleeding. This article describes a modification of Cabrol's technique in which coronary ostial buttons are mobilized and the entire aortic wall resected. This procedure has been used in five patients with varied pathology, with no perioperative deaths and one minor intraoperative neurological event. The greater ease of operation and improved hemostasis afforded by the technique described in this article warrant its consideration in patients requiring aortic root replacement, and may prove particularly helpful in complex cases and reoperations.

Laparoscopic hernia repair of an incisional hernia secondary to placement of an implantable cardioverter defibrillator.

We present the laparoscopic repair of a large incisional hernia secondary to placement of a subcostal ICD pulse generator. Laparoscopic repair of large incisional hernias provides a unique and technically feasible form of repair in the 2%-13% of patients who will develop an incisional hernia following an abdominal surgery. This form of hernia repair is associated with minimal morbidity and prompt resumption of patient activities and work.

Multiple left-sided cardiac lesions in one of Noonan's original patients.

We describe a complex case of obstruction of the left ventricular outflow tract in one of Dr. Noonan's original patients. Intraoperative findings revealed pathology at the valvar, subvalvar and supravalvar positions. Patients with Noonan syndrome are traditionally described as having right-sided cardiac pathology. Review of the literature revealed left-sided lesions to occur in a substantial number of these patients. We therefore suggest the routine employment of cardiac ultrasonography in all patients with Noonan syndrome with attention directed toward left-sided pathology, as well as the frequent pulmonary valvar pathology.

Late development of functional subvalvar stenosis after repair of truncus arteriosus.

The late development of subvalvar stenosis following truncus repair is described. It may occur in patients with an overriding truncal valve and a relatively small ventricular septal defect (VSD) closed with an inappropriately sized patch. Management consisted in enlarging the VSD and closing it with a large, tailored patch. Consideration should be given to enlarging the VSD at the time of original repair if the truncal valve is overriding.