摘要:

The purpose of this study was to develop a clinically applicable system for quantifying premortem myocardial area at risk. Coronary artery occlusion was performed in 18 closed-chest dogs (1 1 left anterior descending and seven circumflex). 99m Tc (15 mCi)-labeled macroaggregated albumin was then injected through an angiographic catheter into the left main coronary artery. Gated nuclear images were obtained in the left anterior oblique view in dogs with left anterior descending occlusions and in right anterior oblique views in dogs with circumflex artery occlusions. The corresponding enddiastolic images were analyzed. The percent area at risk was determined as the planimetric ratio between the hypoperfused area and that of the total left ventricular myocardium. At the completion of the study the heart was excised and the autoradiographic area at risk for the left ventricle was determined. The theoretic advantage of the use of gated acquisition for determination of area at risk over the use of nongated acquisition was assessed. For each study a time-integrated nongated image was produced by summating all frames of the gated study. The area at risk on this composite image was analyzed in the same manner as for the gated study and compared with the postmortem area at risk. Studies in five control dogs in which concomitant left atrial and intracoronary injection of different radioactive-labeled macroaggregates were used revealed no false-positive defects and similar and relatively homogenous radionuclide distribution. Postmortem autoradiographic area at risk ranged from 3.8% to 36.3% of the left ventricular mass. End-diastolic areas at risk in vivo correlated well with those determined by the postmortem autoradiographic method (r = .95, y = 0. 86x ± 2.7). The regression equations relating interobserver and intraobserver variance for analysis of the end-diastolic image areas at risk were small (r = .98, y = 1.06x − 0.66 and r = .96, y = 1.06x − 0.50, respectively). The interobserver and intraobserver differences for determinations of autoradiographic area at risk were represented by r = .99, y = 1.04x − 0.54 and r = .95, y = 0. 88x ± 2.79. Finally, comparison of the area at risk in vivo for the nongated image with the postmortem area at risk yielded a correlation of r = .79, y = 0. 80x − 2.2. Nongated imaging was less sensitive and accurate than gated imaging and resulted in three false-negative studies, as well as a poorer correlation with results of postmortem autoradiography. We conclude that premortem canine area at risk can be accurately and reproducibly determined with the use of this nuclear imaging technique. Gated nuclear imaging significantly enhances the sensitivity of the determination of area at risk as compared with static image acquisition. Since intracoronary 99mTc-labeled albumin macroaggregates are well tolerated in humans, this technique may be useful in assessing the area at risk in clinical studies of invasive coronary artery reperfusion.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Conventional coronary angiography has significant limitations in quantifying the severity and functional significance of coronary stenoses. However, coronary reactive hyperemia is an excellent physiologic indicator of coronary reserve. Digital subtraction angiography offers the potential to analyze coronary blood flow dynamics quantitatively. Therefore we assessed the accuracy of digital angiographic methods to detect and quantify reductions in coronary flow reserve secondary to stenoses of varying magnitude in an experimental canine preparation. Studies were performed in nine anesthetized open-chest dogs with an electromagnetic flow (EMF) probe and two pneumatic occluders positioned on the left circumflex coronary artery. One occluder served to induce reactive hyperemia by temporary total occlusion, while the other served to produce variable gradations of stenosis. Digital angiography was performed after the subselective injection of contrast under basal conditions and during reactive hyperemia. Time-intensity curves were obtained from digital angiograms for both a coronary and a myocardial region of interest. Measurements included area under the curve, time to peak contrast, and contrast disappearance rate. An index of coronary reserve was computed as the ratio of hyperemic to basal measurements for each of these methods. Coronary blood flow ranged from 6.5 to 142 ml/min, with hyperemic to basal EMF flow ratios of 0.80 to 4.2:1. The index derived from contrast decay rate showed a poor correlation with EMF (r = .34). The correlation between measurements of time to peak myocardial contrast and coronary blood flow was r = .68 (y = 0.16 × ± 0.97). The area under the time-intensity curve from a coronary region of interest showed a close correlation with coronary blood flow (y = 0.91 × ± 0. 1, r = .86). Thus estimates of coronary reserve by computer analysis of digital subtraction angiograms can yield information regarding the physiologic consequences of coronary stenoses.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The data obtained in this study demonstrate that the concentration of serotonin is markedly elevated (18- to 27-fold) at the site of a coronary arterial stenosis in open-chest, anesthetized dogs with cyclic flow variations. Cyclic flow variations in this experimental preparation were abolished by ketanserin, a 5-hydroxytryptamine antagonist, but serotonin concentration at the site of the coronary stenosis remained elevated. The intra-atrial administration of serotonin (0.16 to 1 mg/min) restored cyclic flow variations after they had been abolished by ketanserin. Taken together, these data suggest that serotonin may be one of the important mediators of cyclic flow variations in this experimental preparation.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Hemodynamic measurements in human subjects and in experimental animals are generally made in the supine position; not much attention is paid to potential beneficial or harmful effects of right or left lateral positions on cardiac output or other hemodynamic variables. To evaluate the potential influence of such positional changes on cardiac performance, we measured cardiac output and left and right ventricular pressures (with micromanometer catheters) in anesthetized experimental animals (eight dogs and nine pigs) in the supine, right lateral, and left lateral positions. Cardiac output increased from supine to left lateral (mean SD, 2.6 ± 0.9 to 3.1 ± 1.0 liters/min; p < .001) and from supine to right lateral positions (2.6 ± 0.9 to 3.1 ± 1.1 liters/min; p < .001). There was an associated decrease in arteriovenous oxygen saturation difference from supine to left lateral position (31 ± 8% to 24 ± 4%; p < .001) and from supine to right lateral position (32 ± 9% to 25 ± 6%; p < .001). Left ventricular systolic and end-diastolic pressures increased from supine to left lateral (128 17/9 ± 2 to 147 ± 19/16 ± 4 mm Hg; both p < .001) and from supine to right lateral positions (128 ± 19/9 ± 2 to 141 ± 16/16 ± 7 mm Hg; p < .01 and p < .001, respectively). Similarly, right ventricular systolic and end-diastolic pressures also increased from supine to left lateral (30 ± 7/3 ± 2 to 38 ± 7/8 ± 2 mm Hg; both p < .001) and from supine to right lateral positions (31 ± 8/3 ± 2 to 43 ± 8/11 ± 4 mm Hg; both p < .001). Systolic and end-diastolic right ventricular pressures were significantly higher in the right lateral position than in the left (both p < .001). Heart rate did not change with positional maneuvers. Neither the sequence of positional changes nor the species of animal (dog vs pig) had any apparent influence on the results. Roentgenographic analysis of the differences in height of the right ventricle relative to the inferior vena cava suggests that changes in hydrostatic pressure may be entirely responsible for the increases in right ventricular end-diastolic pressure when animals are changed from the supine to the left or right lateral positions. We conclude that a change from supine to lateral position significantly increases intracardiac pressures and cardiac output in experimental animals. If confirmed in humans, these findings may have significant implications for the assessment of hemodynamic status of patients in intensive care unit and catheterization laboratory settings and for the treatment of patients in low-cardiac output states.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Using a multielectrode conductance catheter to estimate continuous left ventricular volume we determined the end-systolic pressure-volume relationship (ESPVR) in situ in open-chest anesthetized dogs. Dogs (n 8) were studied in the control state and after pharmacologic sympathectomy (hexamethonium) and surgical vagotomy both before and after the administration of dobutamine. ESPVR was measured during brief (5 to 6 sec) preload reduction by balloon occlusion of the inferior vena cava (IVCBO). The relationship was highly reproducible. The slope (Ees) and volume intercept (V,) (mean ± SD) in the control series were 5.8 3.6 mm Hg/ml and 6.5 ± 12.5 ml, respectively. Upon release of the IVCBO (preload recovery), Ees was 7.7 ± 3.6 mm Hg/ml and V0 was 12.4 ± 9.6 ml (p < .01). Autonomic blockade produced a 50% reduction in Ees and a concomitant decrease in Vo (p < .01), and eliminated the difference between ESPVR generated by preload reduction (IVCBO) and preload recovery (IVCBO release). Subsequent dobutamine infusion increased Ees to 6.1 ± 3.5 mm Hg/mI and VO to 4.1 ± 6.9 ml, consistent with reported changes of the ESPVR with positive inotropic intervention. A small artifact of right ventricular filling was observed in the left ventricular volume catheter signal, but this did not appreciably alter the ESPVR. These results demonstrate the feasibility of the determination of ESPVR in situ by the conductance catheter and brief IVCBO and underline the importance of the use of rapid load changes to minimize reflex activation during the measurements.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The hypothesis was tested that regional myocardial contractile dysfunction can detect subtle regional coronary blood flow maldistribution induced by exercise. In seven dogs, left ventricular pressure (micromanometer), regional systolic wall thickening (WTh, sonomicrometry), and myocardial blood flow (MBF, microspheres) were measured when mild degrees of coronary artery stenosis were produced during treadmill exercise. During exercise without coronary stenosis, WTh increased by 21 ± 12% (SD), and transmural MBF increased uniformly. In each dog, two levels of coronary stenosis were produced during exercise by adjusting the coronary hydraulic cuff: (1) St-Ex I, where WTh during exercise failed to increase significantly (average change 0 ± 7%), and (2) St-Ex II, where WTh during exercise decreased moderately from the resting control value (average −20 ± 8%). In the potentially ischemic zone coronary hyperemia occurred with each run: resting subendocardial MBF was 1.09 0.30 mg/g/min, and it was 3.04 ± 0.83 during control exercise, 2.48 ± 0.75 during St-Ex I, and 1.55 0.59 ml/g/min during St-Ex II (p < .01 compared with control exercise and control area). The subendocardial-subepicardial blood flow ratio fell from 1.32 ± 0.27 during control exercise to 1.07 ± 0.20 (p < .05) during St-Ex I, and to 0.64 ± 0.15 (p < .01) with St-Ex II. Changes in the subendocardial electrogram and reactive hyperemia occurred more consistently during St-Ex II than St-Ex I. Thus, failure of regional function to increase during exercise detected slight maldistribution of regional MBF, whereas reduction of regional function during exercise of 10% or more below the resting value was a reliable marker of a regional flow defect and was always associated with other evidence of ischemia. Therefore, regional dysfunction during exercise can detect subcritical but functionally significant coronary stenosis, which may allow regional wall motion to be used for detecting coronary artery disease at a relatively early stage.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID