Biomedical subjects
Publications and source records attributed to C B Higgins.
This article provides some examples of what the previous article outlined. The sections on Image Display and Myocardial Characterization contain numerous illustrations of gating, cross-sectional images, flow signals, and ischemic injury. The possibility of metabolic imaging with NMR and quantitating blood flow is also considered.
The initial clinical experience from 5 centers in the United States with iohexol for routine cardioangiography is presented. The investigation includes 124 patients who received iohexol and 127 patients who received meglumine-Na diatrizoate. Iohexol produced a lesser degree of systemic hypotension after coronary angiography and left ventriculography than diatrizoate. No deleterious electrocardiographic changes were observed after iohexol injections. Iohexol was well tolerated by the patients and it may become a preferred contrast medium for routine clinical cardioangiography.
We have successfully corrected interrupted aortic arch with ventricular septal defect by employing deep hypothermia and circulatory arrest, a median sternotomy incision, and a pulmonary arteriotomy. This simplified technique has the advantage of an abbreviated period of cerebral ischemia, with a relatively simple partitioning of the pulmonary artery.
The clinical, angiocardiographic, and surgical findings in a cyanotic child with dextrocardia, L-loop, laterally inverted but otherwise normally related great arteries, and situs ambiguus are described and compared with other similar cases. Electrocardiographic, echocardiographic, and angiographic data are reviewed, and the segmental approach to diagnosis is stressed. Both systemic and pulmonary veins returned to the right-sided atrium. Blood then passed either through the mitral valve to the morphologically left ventricle and to the aorta or through an atrial septal defect to a small left-sided atrium, right ventricle, and pulmonary artery. Total correction was undertaken with an intra-atrial baffle to direct pulmonary venous return to the morphologically right ventricle and systemic venous return to the right ventricle. The subpulmonic stenosis was alleviated with an outflow patch.
To assess the effects of acute incremental volume overload on cardiac size, function, and the pulmonary circulation, we studied six anesthetized dogs using intravenous digital angiography. Aortocaval (AC) fistulas were placed in four dogs, and fistulas in both a carotid and iliac artery were placed in two dogs. Data were obtained at four points: (1) control stage; (2) partial shunt (PS, where either AC partially open or iliac fistula was open and carotid fistula was closed); (3) full shunt (FS, AC shunt open or both iliac and carotid shunts open); and (4) control stage 2. Little change in heart rate (HR) or arterial pressure occurred. With FS, both mean pulmonary artery and wedge pressures increased (p less than 0.05); however, systemic and pulmonary vascular resistances declined. Cardiac output rose (1.54 +/- 0.42 L/min at control) to 2.44 +/- 0.84 L/min at PC (P less than 0.05 vs control) and to 3.13 +/- 0.89 L/min at full shunt (p less than 0.01 vs control). Both left (0.40 +/- 0.09 to 0.55 +/- 0.10 to 0.66 +/- 0.10, p less than 0.05 and p less than 0.01 vs control, respectively) and right (0.34 +/- 0.10 to 0.40 +/- 0.10 to 0.51 +/- 0.09, the latter p less than 0.01 vs control) ventricular ejection fractions rose, as did left (30.7 +/- 13 ml to 35.1 +/- 13 ml to 37.8 +/- 13 ml, the latter p less than 0.05 vs control) and right (37.4 +/- 6.1 ml to 44.2 +/- 16.6 ml to 51.4 +/- 17 ml, the latter p less than 0.01 vs control) ventricular end-diastolic volumes. Atrial volume (determined at ventricular end-systole) also increased (9.4 +/- 3.6 ml to 11 +/- 3.5 ml to 12.9 +/- 4.3 ml, the latter p less than 0.05 vs control). These increases in cardiac function and size occurred in association with a shortening of pulmonary transit time (5.4 +/- 0.8 to 3.5 +/- 0.7 seconds to 2.9 +/- 0.5 seconds, the latter two p less than 0.05 and p less than 0.01 vs control, respectively), with no significant change in pulmonary blood volume. We conclude that acute volume overload produces cardiac chamber dilatation, along with increases in systolic function. Both pulmonary and systemic vascular resistance declined, and the transit time in the pulmonary circulation shortened. Digital intravenous ventriculography is a useful technique for the analysis of the central circulation during acute hemodynamic manipulations.
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The presumption that the results of left ventricular systolic function tests performed at rest are related to the symptoms of chronic congestive heart failure or to exercise capacity is unproved. Thirty-three patients with chronic congestive cardiomyopathy underwent serial exercise tests, determinations of ejection fraction and systolic time intervals, echocardiograms, assessment of symptom score, chest roentgenogram, and physical examination over a mean ( +/- standard deviation) of 24.8 +/- 14.1 months. Maximal exercise performance achieved correlation with symptoms (r = 0.66) but not with indexes of left ventricular function. Edema, elevated jugular venous pressure, rales and radiologic evidence of pulmonary venous hypertension were more common in patients with severe limitation of exercise capacity. in 17 patients whose functional capacity changed during the follow-up period, congruent changes in left ventricular function measured at rest were not consistently observed. Thus the findings on history, physical examination and radiologic examination correlate with exercise capacity, but indexes of left ventricular performance at rest do not and therefore are of limited use in assessing treatment. The clinical course of patients with chronic congestive cardiomyopathy can be followed up safely, effectively and economically by simple clinical observations. Serial laboratory testing of left ventricular function can be reserved for specific indications, research and patients with valvular heart disease.
To assess regional ventricular wall thickening, we studied 8 open-chest dogs using digital intravenous ventriculography at a control stage, after subtotal and total coronary occlusion, and then after isoproterenol administration. In 3 dogs, 2 pairs of myocardial thickness crystals were implanted. Correlations of measures of wall thickness and percentage of wall thickening with crystal measures were excellent at the base (r greater than or equal to 0.97) and near the apex (r greater than or equal to 0.97). Four areas of the inferoapical wall muscle were measured: the base, mid-wall, distal wall, and apex. Four chamber dimensions were also examined: the long axis, base decreased with ischemia. At completion occlusion, it was -24.6 +/- 6% at the base, -27.3 +/- 5% at the mid-wall, -27.1 +/- 5% at the distal wall, and -24.7 +/- 5% at the apex. Percent thickening decreased with occlusion, although greater at the base and mid-wall than at the distal wall and apex. With isoproterenol, end-diastolic thickness increased only at the apex, with little change at the base, distal wall, and mid-wall. Percent thickening increased. In general, ischemia produced increases in end-diastolic hemichords with little change in the long axis. Isoproterenol reduced the hemichords, although the long axis did not change. We conclude the digital intravenous ventriculograms can be used to assess changes in wall thickness with high degrees of accuracy. Asymmetric thickening occurred at rest, with ischemia and with inotropic stimulation, being greatest at the apex and least at the base.
Fifty-one patients were divided into two groups: 20 patients with proven rheumatic mitral valve disease (RMVD) and 31 patients with left atrial enlargement (LAE) of a nonrheumatic etiology. The latter group included patients with ischemic papillary muscle dysfunction, mitral valve prolapse, and congestive cardiomyopathy. Radiographic studies showed that enlargement of the left atrial appendage (LAAE) was present in 18 of 20 rheumatics but in only one of 31 non-rheumatics. There was no direct relationship between enlargement of the LAA and radiographic or echocardiographic left atrial size, degree of pulmonary venous hypertension (PVH), or presence of atrial fibrillation. It is postulated that rheumatic inflammation of the LAA allows it to dilate out of proportion to the body of the left atrium. In the adult patient with radiographic findings of PVH, LAAE is a valuable and specific radiographic sign of rheumatic mitral valve disease.
The effects of intravenous injection of an ionic contrast material (Renografin-76 [meglumine sodium diatrizoate]) on left ventricular pressure, internal diameter, and wall thickness, and on coronary and femoral hemodynamics were compared with those of a hydrolytically stable nonionic contrast material (iohexol). Renografin-76 caused drastic biphasic changes in left ventricular pressure and dp/dt (rate of change of left ventricular pressure), and moderate changes in end systolic dimension. Iohexol caused little or no change in left ventricular pressure and dimensions. In addition, Renografin-76 caused marked arterial hypotension and large increases in coronary and femoral blood flows, while iohexol caused no significant change in arterial pressure and coronary blood flow, and a mild increase in femoral blood flow. Based on these findings, it is concluded that iohexol is preferable to standard ionic contrast material for deriving basal physiologic information from computed tomographic and digital vascular studies.
Metrizamide was employed in six patients who, during angiography, had had severe anaphylactoid reactions to conventional ionic contrast media. Five of these patients had received corticoid premedication before injection of both conventional contrast medium and metrizamide; anaphylaxis occurred only after administration of conventional contrast media. Four patients had no detectable reaction whatsoever after metrizamide; a fifth had only transient tachycardia. In the sixth patient, delayed edema developed in the region of his cerebral arteriovenous malformation. These observations suggest a marked decrease in the incidence and severity of anaphylactoid reactions when metrizamide is substituted in patients who have reacted to ionic contrast media. Metrizamide, or a comparable nonionic contrast agent, should be strongly considered in patients who have had a severe reaction to conventional contrast medium.
To determine the validity of cardiac output estimates obtained by digital video subtraction angiography (DVSA), they were compared with thermodilution values in 6 anesthetized dogs. Multiple levels of cardiac output were produced in each dog by graded openings of peripheral arteriovenous fistulas. Both direct contrast and mask-mode images were evaluated. There was good correlation between thermodilution and direct contrast values (r = 0.88) as well as between thermodilution and mask-mode values (r = 0.89), though the mask-mode outputs were 12 +/- 1.1% less than the direct contrast values (p less than 0.05). Direct contrast and mask-mode values correlated well (n = 6; r greater than or equal to 0.95). Digital outputs exhibited little variation, indicating excellent reproducibility. These results demonstrate the validity of area-length estimates of cardiac output by DVSA.
A noncomputerized, count-based technique for the determination of left ventricular ejection fraction (LVEF), which does not use geometric assumptions of left ventricular shape, was developed. The noncomputerized technique and computerized multigated ventriculography using both fixed and variable region-of-interest (ROI) methods were performed on 16 patients. The LVEFs obtained with the noncomputerized technique correlated well with both the fixed ROI computerized technique (r = .87) and the variable ROI computerized technique (r = .86). It is concluded that when a computer is not available, the noncomputerized technique is a valid alternative for the determination of LVEF in resting patients in stable sinus rhythm.
Digital video subtraction angiography (DVSA) after central intravenous administration of contrast media was used in experimental animals and in patients with suspected coronary artery disease to quantitate left ventricular dimensions and regional and global contractile function. In animals, measurements of left ventricular (LV) volumes, wall thickness, ejection fraction, segmental contraction, and cardiac output correlated closely with sonocardiometry or thermodilution measurements. In patients, volumes and ejection fractions calculated from mask mode digital images correlated closely with direct left ventriculography. Global and segmental contractile function was displayed in patients by ejection shell images, stroke volume images, and time interval difference images. Central cardiovascular function was also quantitated by measurement of pulmonary transit time and calculation of pulmonary blood volume from digital fluoroscopic images. DVSA was shown to be useful and accurate in the quantitation of central cardiovascular physiology.
Perfluoroctylbromide (PFOB) was evaluated as a liver/spleen-specific and tumor imaging agent in 30 rabbits implanted with VX2 tumors. Computed tomographic (CT) scanning of all rabbits was performed after sacrifice. Half of the animals were given 5 ml/kg of PFOB emulsion intravenously 48 hours prior to sacrifice. Twenty rabbits were used for anatomic correlation and ten for histologic analysis. PFOB concentration was measured in normal liver and spleen in eight rabbits at two days, in six rabbits at seven days, and in six rabbits at 14 days after PFOB administration (5 ml/kg, intravenously). PFOB increased the CT numbers of the liver by 49 HU and the spleen by 250 HU. More important for diagnostic purposes, PFOB produced dense enhancement of the rim of the tumor. The density of the rim of the tumor was increased by 102 HU as a result of accumulation of PFOB in macrophages at the periphery of the tumor. The half-life of PFOB in the liver and the spleen was approximately five days.
The effect of perfluoroctylbromide (PFOB) on liver and tumor echogenicity was evaluated in rabbits. The echogenicity of the kidney, which is not affected by PFOB, was used as the basis for comparison in the liver studies. For the liver echogenicity study, sonography was performed on four rabbits, two with PFOB and two without PFOB, and four rabbits prior to and following the intravenous administration of 5 ml/kg PFOB. All livers were equal to or less echogenic than kidney in the control animals. All livers became more echogenic than kidney two days after administration of PFOB. The effect of PFOB on tumor echogenicity was evaluated in 18 rabbits with VX2 tumor implanted in the liver. Ultrasound studies of all rabbits were performed by the same physician before and two days after half the rabbits had received PFOB (5 ml/kg intravenously). The reviewers correctly identified all rabbits that received PFOB by visualization of an echogenic rim around the hepatic tumors.
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The effects of intracoronary injection of two nonionic contrast media (iohexol and metrizamide) on myocardial contraction and chemical composition of coronary sinus (CS) blood were compared with those caused by the standard ionic contrast material for coronary angiography, sodium meglumine diatrizoate (R76), in 14 anesthetized dogs. The effects of each agent on regional contractility were compared in the normal state and in the presence of a critical coronary artery stenosis. The three contrast media produced equivalent decreases in hematocrit and sodium (both NS), but R76 caused a greater increase in CS osmolality (p less than 0.02). R76 caused a significant decrease in CS potassium and ionized calcium (both p less than 0.001), but neither nonionic contrast medium caused a significant change in either potassium or calcium. In the normal state, R76 caused initial transient (less than 10 seconds) increases in both end-diastolic (p less than 0.006) and end-systolic segment length (p less than 0.02) and a decrease in rate of change of segment length (dL/dt) (p less than 0.002). The nonionic agents caused a mild increase in dL/dt (p less than 0.04) and a decrease in end-systolic segment length (p less than 0.03); both returned to control levels within 1 minute. In the presence of a stenosis, R76 caused a more severe and prolonged increase in end-diastolic and end-systolic segment lengths (p less than 0.03) and a decrease in dL/dt (p less than 0.002), which did not return to control within 2 minutes. The effects of the nonionic agents were similar in both normal and diseased states. We conclude that nonionic contrast media produce fewer alterations than ionic contrast media in coronary sinus blood chemistry and myocardial contractile state. The effect of ionic contrast media on regional contraction is accentuated in the presence of coronary artery stenosis.