Excimer laser coronary angioplasty in high-grade stenoses and chronic occlusion

Excimer-laser-angioplasty offers the advantage of minimal thermal injury to adjacent tissue compared to other laser ablation techniques. Highly flexible glass-fiber-catheter systems are now available, and are capable of transmitting sufficient energy densities to ablate even calcified atherosclerotic coronary plaques. We report initial results of excimer-laser-ablation of severe coronary stenoses and occlusions in 17 patients. An excimer-laser (308 nm) with a pulse duration of 50 ns and a repetition rate of 10 to 40 Hz served as laser source. Eight patients had a chronic total occlusion (RCA, n = 4, RCx, n = 3, LAD, n = 1), nine patients had 90% to 95% stenoses (LAD, n = 7, RCA, n = 2). In all cases a laser-catheter consisting of 17 circumferentially orientated 100 microns glass-fibers and a central 15/1000-inch lumen could be advanced to the stenoses/occlusion over a guidewire that had been passed across the stenoses/occlusion. Stenoses diameter could be reduced by 41.5 +/- 10.1% in all patients and vessel lumen was further increased by subsequent balloon dilatation in 10 cases. After 24 h, 16 vessels were patent and showed no restenoses; one recanalized RCA was found reoccluded. We observed no complications, such as perforation, spasm, or thrombi.     

Detection of ischemia with thallium-201 single photon emission computerized tomography (SPECT) and radionuclide ventriculography in comparison with stress cineventriculography

The accuracy of radionuclide techniques for detection of exercise-induced myocardial ischemia was analyzed with TL-201 single-photon emission computer tomography (SPECT) and gated blood pool ventriculography in 31 patients. Reversible and persistent perfusion defects in the biphasic SPECT studies, parametric phase and amplitude images and global indices of left ventricular function were evaluated and compared to the results of exercise cineventriculography. Out of 25 patients with coronary heart disease, 20 had exercise-induced ischemia and 17 patients had a prior myocardial infarction. SPECT detected ischemia with a sensitivity of 85% and a specificity of 100%, gated blood pool ventriculography had a sensitivity of 60% and a specificity of 91%. Both scintigraphic methods were comparable in the detection of myocardial infarcts (SPECT/gated blood pool ventriculography: sensitivity 88%/82%; specificity 100%/93%; positive predictive value 100%/93%). A difference in detection of ischemia between both methods was found in patients with myocardial infarct and additional ischemia: all patients with additional ischemia were detected by SPECT, whereas gated blood pool ventriculography failed to identify the additional ischemia in 1/4 of these patients (p less than 0.05).     

Quantitative segmental analysis of wall function of the right ventricle in probands with healthy hearts

To investigate and determine the local wall motion of normal right ventricles, biplane angiograms from 14 normal subjects were analyzed. In all patients, organic heart disease was excluded by angiography and right heart catheterization under exercise. Using a radial model, segmental systolic area shortening was determined for the anterior, anteroapical and inferior segment in the RAO-projection and the inferior, anteroapical and anterior (free wall) segment in the LAO-projection. The highest segmental shortening was found for the anterior wall in the RAO-projection (45.6 +/- 7.8%) and for the free wall in the LAO-projection with 42.7 +/- 11.3% (RAO: anteroapical 28.1 +/- 6.3%; inferior: 26.5 +/- 7.8%. LAO: anteroapical: 34.7 +/- 18.8%; inferior: 30.6 +/- 21.6%). Corresponding to these different segment shortenings, right ventricular contraction seems to have a disharmonic pattern in comparison to the left ventricle. Normal local wall motion of segmental area shortening was predicted by the means-2SD (95.5%) confidence interval. The confidence interval of the inferior (-12.6%) and anteroapical (-2.9%) segment in the LAO-projection was poor compared to the other segments (RAO: anterior 30.0%; anteroapical 15.5%; inferior: 10.9%; LAO: free wall: 20.1%). For the LAO-inferior and LAO-anteroapical segment, even akinesia was within the 95.5% confidence interval. In conclusion, quantification of local wall motion seems possible with reasonable confidence for RAO segments and the free wall in the LAO-projection only.     

The kallikrein-kinin system as mediator in vasogenic brain edema. Part 1: Cerebral exposure to bradykinin and plasma

Plasma and bradykinin were perfused into the ventricular system of mongrel dogs to investigate whether either or both induce brain edema. Formation of cerebral edema was determined by measurement of cerebral water and electrolytes in periventricular white matter, cerebral cortex, and caudate nucleus. The response of cerebral tissue to exposure to bradykinin or to plasma, as a carrier of kininogens, was analyzed by assessment of the perfusate composition after ventricle passage. The authors report that cerebral administration of bradykinin induces cerebral edema. Ventricular perfusion with plasma also led to an increase of cerebral water content which was restricted to the white matter, but involved all brain tissue areas, if bradykinin was used. Ventricular perfusion with plasma was associated with consumption of the kinin precursor (kininogens) indicative of formation of kinins. Significant consumption of the precursor was found in five out of nine animals subjected to plasma perfusion of the ventricular system. In these animals a close correlation between the increase of white matter water content and kininogen-consumption as a measure of kinin-formation was obtained. Marked kinin-degrading activity was observed during ventricular perfusion with bradykinin as concluded from a considerable decrease of bradykinin concentration in the cisternal effluent compared to the inflowing perfusate concentration. Ventricular perfusion with plasma was associated with a decrease of K+ clearance capacity with continued duration, and in two animals with a release of glutamate into the plasma perfusate, suggesting an involvement of cytotoxic mechanisms. These findings provide support for the hypothesis of a mediator function of the kallikrein-kinin (KK) system in vasogenic brain edema. The next question that needs to be answered to complete the picture--does spontaneous activation of the KK system occur in conditions leading to vasogenic edema?--is studied in a subsequent report.     

Superficial- and deep-tissue temperature increases in anesthetized dogs during exposure to high specific absorption rates in a 1.5-T MR imager

Superficial- and deep-tissue heating was measured in five dogs during high-specific-absorption-rate radiofrequency (RF) irradiation to see whether significant temperature changes could be produced by a 1.5-T clinical magnetic resonance imager. The RF power output employed was 6.3 times that required for routine imaging. Temperature probes were placed in both deep and superficial tissues, and temperatures were recorded before, during, and after exposure. In each dog, there was a linear temperature increase of several degrees during RF exposure; the maximal average change was 4.6 degrees C in the urinary bladder. The temperature increase was slightly greater in deep tissues than in superficial tissues. The calculated specific absorption rate, based on the temperature change, averaged 7.9 W/kg for all five dogs. These findings argue for continued caution in the design and operation of imagers capable of high specific absorption rates, particularly when they are used for imaging infants or patients with altered thermoregulatory capability.     

Cerebral energy metabolism following fluid-percussion brain injury in cats

Clinical and experimental evidence suggests that head injury can cause alterations of cerebral energy metabolism. However, the etiology of this metabolic perturbation is not known. The objective of this study was to determine the effect of fluid-percussion trauma on cerebral energy metabolism. Seven ventilated, chloralose-anesthetized cats were subjected to a 3.2-atm fluid-percussion brain injury. Before and for 8 hours after trauma, continuous phosphorus-3 1 magnetic resonance spectrography was obtained to noninvasively monitor tissue pH, phosphocreatine (PCr), and inorganic phosphate (Pi) levels. Measurement of cerebral blood flow (CBF) by the radioactive microsphere technique and calculation of oxygen and glucose consumption (CMRO2 and CMRG1) were also performed before trauma as well as 30 minutes and 1, 2, 4, and 8 hours after trauma. The data showed a moderate decrease in tissue pH from 7.04 to 6.89 at 30 minutes following trauma with return to control levels by 3 hours posttrauma. During the 8-hour observation period, CBF, CMRO2, and CMRG1 remained at control levels. Tissue PCr and Pi levels were also unchanged. Fluid-percussion trauma at the 3.2-atm level in ventilated cats causes a moderate and transient decrease in tissue pH that returns to control levels after trauma. No other metabolic changes are seen later than 30 minutes posttrauma. This indicates that a mild metabolic disturbance occurs after trauma in the ventilated animal and quickly returns to normal.     

Quantification of myocardial ischemia and infarction with single photon emission computed tomography

To evaluate the feasibility of ²⁰¹Tl single photon emission computed tomography (SPECT) for quantitative detection of myocardial infarction and ischemia, scintigraphic studies were related to angiographic findings. In study A infarct sizes with SPECT were compared with the angiographic infarct sizes of 30 patients. A linear correlation was found for the % infarct of the left ventricular circumference between both methods (r=0.73; P< 0.001; mean infarct size 20.7%±10.5% (angio) vs 19.8%±12.9% (SPECT), mean±SD). Furthermore, a significant inverse correlation between scintigraphic infarct size and left ventricular ejection fraction (r=-0.87, P< 0.001) was obtained. In study B exercise/rest ²⁰¹Tl SPECT was used for quantification of myocardial ischemia. Forty-three patients underwent both stress ²⁰¹Tl SPECT and biplane exercise left ventriculography. Ischemia was expressed as % defect size of the left ventricular circumference. Sensitivity and specificity for detection of ischemia were 96% and 100% respectively with stress SPECT. Extent of myocardial ischemia correlated significantly with both methods (r=0.63; SPECT defect=1.0 angiographic ischemia +2%; P< 0.001). The regression followed the line of identity and the mean sizes of ischemia were identical (SPECT 12.2±7.6% vs 14.6±12.4% ventriculography, mean±SD) demonstrating the agreement of both methods. However, there was some intraindividual variance between the scintigraphic and the angiographic study. The sensitivity and specificity in single regions with SPECT were lower compared to the global test results. The correlation between the non invasive SPECT and the ventriculography in detection of myocardial infarction and ischemia indicates the clinical value of ²⁰¹Tl SPECT for diagnosis of coronary heart disease.Parts of the results were presented at the 58th sessions of the American Heart Association at Washington, DC (1985)