Microvascular cytomegalovirus endothelialitis of the lung: a possible cause of secondary pulmonary hypertension in a patient with AIDS.

Postmortem examination of the lungs of a patient with advanced AIDS who had developed pulmonary arterial hypertension late in the course of the illness demonstrated extensive cytomegalovirus (CMV) infection in endothelial cells of the lung microvasculature. Enlarged CMV-infected endothelial cells were present in virtually all histologic sections of the lungs, protruded into and compromised the lumens of the small vessels they lined, and were estimated by image cytometry of immunohistochemically stained sections to comprise 0.8% of the total lung tissue volume. Comparison with experimental microvascular embolization studies suggests that this amount of compromise of the microvascular luminal area of the lung is sufficient to elevate pulmonary arterial pressure significantly. Pathologic features in this case differed from both the plexogenic arteriopathy seen in previously reported cases of AIDS-associated primary pulmonary hypertension and the usual form of CMV pneumonitis in AIDS in which alveolar epithelial cells are the predominant site of infection.

The evaluation of compartmental syndromes using somatosensory evoked potentials in monkeys.

Somatosensory evoked potentials (SEPs) of the median, deep peroneal, and tibial nerves were recorded in experimentally induced compartmental syndromes in nine Macaca mulatta monkeys. A total of 17 trials were performed at the following mean pressure levels: 17, 30, 36, and 40 mm Hg. Evoked potentials were recorded using a four-channel evoked response system. Significant changes in SEP waveforms (greater than 3-millisecond increases in N1 or P1 latencies, or a 50% decrease in wave amplitudes in the presence of normal contralateral waveforms) were seen at pressures as low as 30 mm Hg as early as 45 minutes. Pressures of 35 and 40 mm Hg led to more pronounced abnormalities in SEP waveforms, with marked decreases in wave amplitudes and variability in the time to onset of these changes. Somatosensory evoked potentials are noninvasive, sensitive, and dynamic determinations of nerve function and may have clinical significance in the early detection of nerve dysfunction in compartment syndromes.

Onlay technique for occipitocervical fusion.

Twenty-eight occipitocervical fusions using the onlay technique were performed in 27 patients ranging in age from 13 to 77 years (average age, 47.6 years). The indications for fusion included neurologic involvement from atlantoaxial instability associated with superior migration of the odontoid and destructive changes at the occiput-C1-C2 articulation, causing pain unrelieved by conservative treatment. Preoperative diagnoses included rheumatoid arthritis, congenital anomalies, posttraumatic, failed C1-C2 fusions, ankylosing spondylitis, and tumor. A standard posterior exposure of occiput-C1-C2 was used, and iliac crest bone graft was placed over the area to be fused. Postoperative immobilization consisted of skull tong traction, minerva jacket, and halo apparatus. There were no neurologic complications, two superficial wound infections, and minor difficulties with halo loosening. There was one perioperative death. Primary fusion was obtained in 89% of patients at an average of 12.8 weeks. Occipitocervical fusion by the onlay technique is safe, requires no internal fixation, and has a high success rate when compared with other methods of obtaining fusion in the occipitocervical region.

Effect of C1-C2 rotation on canal size.

An anthropometric study of the atlas and axis was undertaken to determine spinal canal diameters, the degree of narrowing with rotation, and odontoid tilt. The mean sagittal diameter of the atlas was 30.1 mm and the mean coronal diameter was 28.8 mm. The mean sagittal diameter of the axis was 19.0 mm and the mean coronal diameter was 22.8 mm. Approximately 64 degrees of rotation occurred at the atlantoaxial complex before sufficient narrowing caused spinal cord compression in the average specimen. An average of 63 degrees of rotation was required to cause facet dislocation. Most specimens examined had a posterior odontoid tilt up to 45 degrees and a facet angle between 1 degree and 29 degrees. Bilateral facet dislocation occurred at 63 degrees. Spinal canal narrowing to 1 cm occurred at 64 degrees. This narrowing would probably not damage the cord, which averages 1 cm in diameter; however, if the rotary motion of C1 and C2 progressed, cord damage could occur. Facet angles and posterior odontoid tilts that are not within the normal range indicate pathological changes.

Angiographic demonstration of coronary sinus thrombosis: a potential consequence of trauma to the coronary sinus.

Abnormalities of the coronary sinus are rarely encountered. A case is presented demonstrating for the first time the angiographic appearance of coronary sinus thrombosis. This may have been the result of surgical trauma during mitral valve replacement or inadvertent cannulation of the coronary sinus during right heart catheterization or pacemaker insertion. Although the clinical significance of coronary sinus thrombosis is uncertain, obstruction of coronary sinus blood flow should not be deleterious because of multiple anastomoses between the coronary sinus system and the anterior cardiac veins. Difficulty in cannulating the coronary sinus for physiologic studies should suggest the possibility of coronary sinus thrombosis, especially in patients who have undergone mitral valve replacement. This may be confirmed by observing the venous phase of selective left coronary arteriography. Finally, coronary sinus thrombosis may be important as a source of pulmonary emboli. The prevalence of this serious complication requires further study.

Constant-pressure coronary artery perfusion during aortic valve operations.

We considered the theoretical differences between the normal relationships of coronary blood flow and perfusion pressure in the working heart and those obtained with continuous, steady-flow perfusion by a roller pump during aortic valve replacement. Steady pump perfusion should deliver less blood flow to the endocardium because: 1. For the same mean artery perfusion pressure, the average coronary blood flow is less with constant-flow pump perfusion. 2. With constant pump perfusion, pressure would be excessively high during systole, and during diastole it would be significantly lower than the mean perfusion pressure. Instantaneous pressure and flow were measured in the left coronary artery in 8 patients undergoing aortic valve replacement, employing either roller pump perfusion or a gravity flow system to provide a steady pressure source. Although we did not attempt to demonstrate improved endocardial flow, the mean left coronary flow was always greater with gravity perfusion (297 versus 153 ml/min), lending support to the theoretically proposed differences between the two perfusion methods.

The effects of intra-aortic counterpulsation on cardiac performance and metabolism in shock associated with acute myocardial infarction.

The effect of intra-aortic counterpulsation (IACP, 22-94 hr) on hemodynamics and cardiac energetics was evaluated in 10 patients in shock after acute myocardial infarction. The data clearly indicate that IACP improves myocardial oxygenation, enhances peripheral perfusion, and probably improves myocardial contractility in the severely diseased heart. Before treatment, decreases in cardiac index (mean value, 1.22 liter/min per m(2)), systolic ejection rate (67 ml/sec), and time-tension index per minute (1280 mm Hg.sec/min) were observed. Systemic vascular resistance varied widely. Low coronary blood flow (68 ml/min per 100 g) was associated with increased myocardial oxygen extraction (79%), low coronary sinus oxygen tension (20 mm Hg), and abnormal myocardial lactate-pyruvate metabolism. During 4-6 hr of IACP, systolic pressure and left ventricular outflow resistance decreased by 18% and 24%, respectively, while cardiac index improved by 38%. Diastolic arterial pressure rose 98%. Increase in coronary blood flow from an average of 68 to 91 ml/100 g per min (P < 0.001) was significantly correlated with rise in mean arterial pressure (r = 0.685). This correlation was best expressed in a third-order curve, which intercepts the point of no flow at a mean aortic pressure of 30 mm Hg. The flow-pressure curve is relatively flat above 65-70 mm Hg, but becomes steeper as mean aortic pressure falls below this point. Myocardial oxygen consumption remained essentially unchanged during early IACP and tended to rise during the later stages. However, the relationship of cardiac work performed to oxygen availability was markedly improved. Myocardial lactate production of 6% shifted to 15% extraction (P < 0.001). After termination of IACP, hemodynamics and myocardial perfusion and metabolism remained improved in the four patients who could be reevaluated. Although the acute shock state was reversed in all patients, only one left the hospital. Extensive myocardial damage limits the long-term survival of such patients. Therefore early IACP seems desirable, when subtle evidence of pump failure after acute myocardial infarction occurs. Early use of IACP may prevent the development of severe coronary shock or may stabilize cardiac energetics in severe shock facilitating subsequent surgical intervention.