Assessment of regional coronary flow reserve by digital angiography in patients with coronary artery disease

Summary Digital angiography provides a convenient means to quantify the progression of a contrast medium bolus injected into a coronary artery throughout the myocardium, which in turn yields information on myocardial perfusion. Sixteen patients presenting a single critical proximal stenosis (estimated diameter reduction >80%) on either the left anterior descending coronary artery (LAD) or the left circumflex coronary artery (LCX) were studied. First, 12 consecutive end-diastolic images of an ECG-triggered intracoronary injection of 4 ml of iopamidol were acquired on 60° left anterior oblique projection under basal conditions. This was repeated 30 s after intracoronary injection of 12 mg of papaverine. For each image sequence, a densogram was computed in each pixel by fitting a curve through its 12 consecutive intensity values. The time of maximal pixel opacification (T_MAX) and the mean ascending time (T_MAT), expressed in cardiac cycles, were determined from each curve. Two myocardial regions of interest (ROI) were defined for each patient, one in the perfusion bed of the LAD, the other in the bed of the LCX. The mean values of T_MAX and T_MAT in each ROI were computed, at rest and during hyperemia. At rest, the mean values of T_MAX and T_MAT obtained from the ROI associated to the stenosis artery were not significantly different from the values obtained in the ROI associated with the intact artery. During hyperemia, a significant decrease of the mean T_MAX and T_MAT was observed in the normally perfused regions (p<0.001). The rest to hyperemia ratios of both T_MAX and T_MAT mean values were considered to be indices of coronary flow reserve. Due to the decrease of T_MAX and T_MAT during hyperemia, the two indices were significantly higher in the normal ROI than in the ischemic ROI (p<0.001).In conclusion: Intracoronary injection of papaverine produces an acceleration of blood flow in normally perfused myocardium despite the increase of vascular volume. This acceleration is absent in regions supplied by a severely stenosed coronary artery. Thus, a differentiation between normally and abnormally perfused myocardial regions is possible by use of indices of coronary flow reserve derived from time parameters of the myocardial circulation.Supported by a grant of the Swiss National Science Foundation.     

Evaluation of myocardial perfusion based on digital subtraction angiocardiography measured contrast medium flow times

The purpose of this study was to discover whether myocardial perfusion can be determined quantitatively by digital subtraction angiocardiography from the passage of contrast medium through the myocardium. Cineangiograms (duration 20 s) were obtained during routine coronary angiography and analyzed by means of a computerized image processing system. Regional myocardial contrast intensity was plotted versus time as a densogram for quantitative assessment. The parameter "medium rise time" showed a good reproducibility (r = 0.92). The average of medium rise time was 2.9 s in well-perfused areas, 3.7 s in less perfused areas, 5.2 s in areas with markedly reduced perfusion and 5.8 s for perfusion defects or scars using Tl-201 scintigrams as reference. The differences between the four groups were significant except between areas of markedly reduced perfusion and perfusion defects or scars (p less than 0.05). The correlation of medium rise time to the extent of the stenosis of the coronary vessel supplying the corresponding myocardial region revealed that the medium rise time on an average was 3.2 s distal to unstenosed vessels, 3.2 s distal to slightly stenosed vessels, 5.4 s distal to highly stenosed vessels and 4.7 s distal to vessel occlusion. The differences between the groups were not significant except between the groups of patients with low and high-grade coronary stenoses. These results indicate that the parameter "medium rise time" of the intensity-time curves determined by digital image processing provides a quantitative assessment of myocardial perfusion from cineangiograms.     

Videodensitometric analysis of human coronary stenoses: validation in vivo by intraoperative high-frequency epicardial echocardiography

Videodensitometry is a nongeometric method of coronary angiographic analysis that can be used to provide an index of coronary luminal area. However, there are few direct studies in vivo of the relationship of videodensitometric data to independent measures of luminal area in humans. Although videodensitometry is theoretically independent of angiographic projection and luminal shape, validation of these assumptions in vivo is also limited. We therefore used intraoperative high-frequency epicardial echocardiography, a technique that can directly determine human coronary luminal area and shape in vivo, to further validate videodensitometry. A total of 36 arterial segments in the left anterior descending and right coronary arteries were studied by videodensitometry and high-frequency echocardiography. Videodensitometry was performed on angiograms in which the arterial segment of interest was not markedly foreshortened and was uniformly filled with contrast. In 22 discrete lesions (13 with circular lumens and nine with oval or complex lumens), videodensitometric and echocardiographic measures of luminal area correlated well (r = .86). In 33 coronary arterial segments, the effect of angiographic projection on videodensitometry was determined by comparison of the results of videodensitometry performed on left anterior oblique vs right anterior oblique angiograms of the segments. Here too, the correlation was good (r = .94, y = 1.04x + 0.002). The good correlation of left anterior oblique with right anterior oblique videodensitometric results held true for lesions with circular and oval or complex lumens. This study further validates the ability of videodensitometry to provide an index of coronary luminal area and confirms in vivo previous assumptions that the results of videodensitometric analysis are independent of angiographic projection and luminal shape.     

Single photon emission computed tomographic teboroxime imaging with a preprocessing masking technique.

We previously reported that single-head SPECT imaging with teboroxime is feasible. However, excessive hepatic uptake in some patients may interfere with image interpretation. This study examined the feasibility of improving image quality by use of a preprocessing masking technique to subtract hepatic activity. A band of 10 pixels in width adjacent to the inferior cardiac silhouette was marked on the raw planar images, and then SPECT reconstruction was done with the Butterworth filter with a frequency cutoff of 0.3 cycles/cm and the power of 10. The stress and rest images were compared before and after masking in 10 patients who underwent SPECT teboroxime imaging during adenosine-induced coronary hyperemia (140 micrograms/kg/min for 6 minutes). SPECT imaging with a single-head detector was performed with the use of a 180-degree anterior arc (from the 45-degree left posterior oblique projection to the 45-degree right anterior oblique projection); 32 images at 8 seconds per stop were obtained (total imaging time = 6.8 minutes). All images were considered subjectively better after the masking technique was used, especially for assessment of inferior wall perfusion pattern. The maximum count in any pixel was in the hepatic region of interest before masking and in the cardiac region of interest after masking (303 +/- 110 counts vs 166 +/- 55 counts; p < 0.001). The difference was especially pronounced in the images that were obtained when patients were at rest (366 +/- 102 counts vs 184 +/- 64 counts; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

根据冠状窦电极走行个体化选择房间隔穿刺时右前斜位透视角度的应用体会

目的总结在行房间隔穿刺时根据冠状窦电极走行特征个体化选择右前斜位透视角度的实际应用体会。方法选择50例因接受房颤导管消融手术而需行房间隔穿刺的患者为研究对象。每例均先经左侧或右侧锁骨下静脉放置冠状窦电极,在后前位透视下,将房间隔穿刺针及长鞘管从上腔静脉回撤至冠状窦口上方1．0～1．5个椎体高度,然后在右前斜位透视下完成穿刺。右前斜位透视角度根据冠状窦电极走行特征选择。记录每例穿刺时的透视角度。结果50例均顺利完成房间隔穿刺,无并发症发生。穿刺时右前斜位透视角度为（35．5±87．21）°,其中多数病例（33例,66％）透视角度为25°～35°。透视角度与左房内径呈弱负相关（P=-0．055,r=-0．27）。结论根据冠状窦电极走行选择房间隔穿刺时的右前斜位透视角度,可以更好地展示房间隔平面,有利于穿刺点准确定位,提高穿刺的成功率及安全性。     

Distal coronary artery perfusion during percutaneous transluminal coronary angioplasty

Perfusion of the coronary artery distal to an occluding angioplasty balloon was performed in 34 patients undergoing coronary angioplasty (PTCA). A randomized crossover study was employed using two exogenous substances as perfusates: lactated Ringer's solution (LR) and a fluorocarbon emulsion (FL), Fluosol-DA 20%. Both substances are electrolyte solutions, but the FL will dissolve more oxygen than the LR. During two attempted coronary artery occlusions of 90 seconds each, we perfused through the central lumen (guidewire channel) of the PTCA catheter at 60 ml/min. With FL perfusion the mean time to onset of angina after occlusion was delayed (41 +/- 21 vs 33 +/- 16 seconds, mean +/- SD; p less than 0.05), the mean duration of angina was shortened (77 +/- 58 vs 92 +/- 70 seconds, p less than 0.05), and the rise in the ST segment of the ECG was reduced (0.15 +/- 0.24 vs 0.2 +/- 0.23 mV, p less than 0.001) when compared to LR perfusion. Balloon occlusion time was able to be extended with FL perfusion (71 +/- 22 vs 59 +/- 22 seconds p less than 0.001). These results indicate that perfusion of the distal coronary artery is possible during PTCA and can reduce ischemia during a prolonged balloon occlusion time.     

Relation between projection positions and X-ray radiation doses during placement of the coronary sinus mapping electrode

Purpose

To reduce X-ray radiation injury, we investigated the relation between projection positions and X-ray radiation doses when a coronary sinus mapping electrode was placed.

Methods

There were 400 patients in whom a coronary sinus mapping electrode was placed for intracardiac electrophysiologic examination or radio-frequency catheter ablation in our hospital between 1 June 2008 and 31 May 2011. The doctors who placed the coronary sinus mapping electrode and the projection positions including posteroanterior, left anterior oblique 45°, and right anterior oblique 30° projection positions were randomly selected. X-ray doses were recorded when the coronary sinus mapping electrode was placed, and then, these were compared between the three projection positions.

Results

The X-ray dose was significantly lower in the right anterior oblique 30° projection position (50.01?±?11.38?mGy) than in the posteroanterior projection position (68.05?±?18.85?mGy, q?=?12.924, p?=?0.000) and the left anterior oblique 45° projection position (71.66?±?16.95?mGy, q?=?15.214, p?=?0.000). There were no statistical significances in X-ray doses between the posteroanterior and the left anterior oblique 45° projection positions (p?=?0.066) and different operators (p?=?0.985).

Conclusion

Based on the results of this study, we suggest that in placing the coronary sinus mapping electrode, the right anterior oblique 30° projection position should be first adopted because it can allow the electrode to be easily placed and reduce the X-ray radiation dose as much as possible.     

Placement of pacemaker leads via the extrathoracic subclavian vein guided by fluoroscopy and venography in the oblique projection

Blind needle puncture of the subclavian vein, which is the standard method used for insertion of pancemaker electrodes, causes an increased risk of lead fractures due to entrapment of the lead by the costoclavicular ligament and/or subclavius muscle. The extrathoracic lead insertion technique was developed to prevent such lead fractures. The present study was performed to evaluate the usefulness of extrathoracic subclavian vein puncture under the guidance of both fluoroscopy and venography in the oblique beam projection. Pacemaker leads were implanted in ten patients under the guidance of both fluoroscopy and venography in the ipsilateral anterior oblique projection. The angle of projection was set as large as possible between 35° and 45°. The needle was held parallel to the X-ray angle of incidence and inserted toward the first rib, then withdrawn until the tip entered the subclavian vein. This modified method of pacemaker implantation was successful in all patients, with no complications during the follow-up period ranging from 4 to 19 months. It also prevented pneumothorax and lead entrapment in soft tissue associated with the clavicle that might be caused by the conventional technique.     

Derivation and validation of a new angiographic score of right coronary artery perfusion

A semi-quantitative right coronary artery score (RCA score)was derived from the ratio of the number of the major left ventricularbranches of the right coronary artery to the total of the rightcoronary and left circumflex arteries, to stratify the extentof perfusion in patients with right coronary artery dominance.Thirty-seven patients with one-vessel coronary disease involvinga dominant right coronary artery proximal to the left ventricularbranches were selected for study. Thallium scintigraphy wasperformed after right intracoronary injection in 11 patients,and 26 patients underwent conventional stress thallium scintigraphy(24 exercise thallium and two dipyridamole thallium scintigraphy).Thallium scores of perfusion region size after right intracoronarythallium injection and perfusion defect size in stress thalliumstudies were quantitated from planar thallium images. Both theRCA score and the regional thallium scores spanned over a widerange. The RCA score (range 0.23–0.85) correlated best with theposterior (70;° left anterior oblique view) plus lateralsegment (40° left anterior oblique view) thallium score(r = 0.88 and 0.53 for intracoronary and stress thallium studiesrespectively). It also correlated with the summed thallium scoresin the posterior, lateral, apical and inferior segments (r =0.73 and 0.54 respectively) but not with thallium scores inthe apex or inferior segment alone. The proposed RCA score quantitates the variable posterolateralperfusion territory of the right coronary artery, and couldstratify the area of myocardium at risk from coronary stenosisin the majority of patients with right coronary dominance.     

Usefulness of coronary angiography for assessing left ventricular systolic function

In previous echocardiographic studies, a correlation between ejection fraction of the left ventricle and change in the movement of mitral annular ring was found. In the light of these studies we planned this study to investigate the relationship between systolic shortening (SS) and percent of systolic shortening (PSS), calculated from long axis frame in coronary angiography and left ventricular systolic functions. One hundred and thirty eight patients (40 women and 98 men; mean age 58±10 years) who had been referred for coronary angiography and left ventriculography were included in the study. Ejection fraction (EF) was calculated from left ventriculography obtained from 30° right anterior oblique projection. Distance from lower border of the ostium of left coronary artery to the most apical border of left anterior descending (LAD) artery was measured at end-systole (ES) and end-diastole (ED) using coronary angiography obtained from the same projection. SS as ED-ES and PSS as SS/ED were calculated. Correlation of SS and PSS with EF was calculated (EF=13.7+4.9×SS, r=0.91 and EF=14.2+6.5×PSS, r=0.90). SS<7 mm and PSS<6% indicated that left ventricle EF was less than 50%, with a sensitivity, specificity and diagnostic accuracy 83%, 100%, 95%; 95%, 86% and 88%, respectively. In conclusion, SS and PSS calculated from coronary angiography have high correlation with left ventricular EF. Therefore, left ventriculography can be omitted in selected patients undergoing coronary angiography if it is not necessary to define the anatomic structure of left ventricle.     

Effects of projection and background correction method upon calculation of right ventricular ejection fraction using first-pass radionuclide angiography

Summary There is no consensus as to the best projection or correction method for first-pass radionuclide studies of the right ventricle. We assessed the effects of two commonly used projections, 30° right anterior oblique and anterior-posterior, on the calculation of right ventricular ejection fraction. In addition two background correction methods, planar background correction to account for scatter, and right atrial correction to account for right atrio-ventricular overlap were assessed. Two first-pass radionuclide angiograms were performed in 19 subjects, one in each projection, using gold-195m (half-life 30.5 seconds), and each study was analysed using the two methods of correction. Right ventricular ejection fraction was highest using the right anterior oblique projection with right atrial correction 35.6 ± 12.5% (mean ± SD), and lowest when using the anterior posterior projection with planar background correction 26.2 ± 11% (p<0.001). The study design allowed assessment of the effects of correction method and projection independently. Correction method appeared to have relatively little effect on right ventricular ejection fraction. Using right atrial correction correlation coefficient (r) between projections was 0.92, and for planar background correction r = 0.76, both p<0.001. However, right ventricular ejection fraction was far more dependent upon projection. When the anterior-posterior projection was used calculated right ventricular ejection fraction was much more dependent on correction method (r = 0.65, p = not significant), than using the right anterior oblique projection (r = 0.85, p<0.001). Comparison of the two methods currently used in clinical studies, showed no significant differences between the means, and r = 0.83 with a standard error of the estimate (SEE) = 7.4%. These data show that the calculation of right ventricular ejection fraction from right anterior oblique studies is less dependent on correction method, and suggest that its use as a standard method which will allow comparisons of results between centres.     

Nonselective preoperative digital subtraction angiography of internal mammary arteries

In preparation for coronary bypass surgery, digital subtraction angiography (DSA) was used to assess the caliber of the left and right internal mammary arteries and to exclude stenoses of their feeding arteries. In 100 patients (86 males, mean age 56 +/- 9 years) DSA was performed with a Siemens Digitron 2 device. A frontal projection was used in 18 patients, and a 10-20 degree right anterior oblique projection was used in 82 patients. The flow was 10 to 25 ml/sec; 20 ml was injected in 45 patients, 30 ml in 41, 40 ml in 5, 50 ml in 8, and 60 ml in 1 patient. Judged on the proximal third, visualization of the left and the right internal mammary artery was good in 80 and 72, fair in 17 and 20, and bad in 3 and 8 arteries, respectively. The diameter (mm) was 2.7 +/- 0.4 (range 1.8-3.4) and 2.7 +/- 0.3 (range 2.0-3.5), and visible length (cm) was 8 +/- 5 (range 1-24) and 9 +/- 4 (range 2-22) for the two arteries, respectively. The 10-20 degree right anterior oblique view separated the left internal mammary artery better from the descending aorta than the frontal view. In more pronounced right anterior oblique views the ascending aorta interfered with the right internal mammary artery. The quality was not different with 20 ml or 30 ml injections. The feeding arteries could not be assessed in 4 patients. One left subclavian artery was found occluded at the orifice. Incidentally, 2 distal right subclavian stenoses and 2 carotid stenoses were detected.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lordotic right posterior oblique projection of the left coronary artery: a speical view for special anatomy.

The lordotic right posterior oblique projection of the left coronary artery is obtained by combining cranial angulation of the X-ray beam with rotation of the patient into the right posterior oblique position. This projection is helpful for separation of the main left coronary artery and the proximal portions of the left anterior descending and circumflex divisions, especially in patients in whom the left anterior descending artery is directed cephalad early in its course. The obtaining of an image from the lordotic right posterior oblique projection adds less than two minutes to the procedure and improves arteriographic assessment of the left coronary artery.     

Diastolic coronary resistance after ischaemia in the isolated rabbit heart: effect of nifedipine

The effect of nifedipine on tension, coronary flow and perfusion pressure was studied in the Langendorff rabbit heart after 15 and 60 min global ischaemia. Nifedipine (1.44 X 10(-8) M) added to the perfusate before 15 min ischaemia prevented the increase of diastolic coronary resistance which occurred on reperfusion in the absence of the drug. The recovery of force of contraction was unaltered. There was no change in the increase in resistance on reperfusion if nifedipine (1.44 X 10(-8) M) was given at the time of reperfusion after 15 min ischaemia. Ventricular fibrillation on reperfusion was prevented if nifedipine was added before 15 min of ischaemia. After a more prolonged period of ischaemia (60 min) the rise of resting tension on reperfusion was not prevented by giving nifedipine (1.44 X 10(-8) M or 1.44 X 10(-7) M) before ischaemia, although the rise during ischaemia was delayed. Both concentrations of nifedipine reduced the increase in diastolic coronary resistance which occurred on reperfusion. These results suggest that nifedipine, in a concentration close to the therapeutic range, increases coronary reperfusion after global ischaemia. This represents one mechanism by which nifedipine can have a beneficial effect on the ischaemic myocardium.     

Upward shift of the lower range of coronary flow autoregulation in hypertensive patients with hypertrophy of the left ventricle.

BACKGROUND. At any given perfusion pressure, coronary reserve is expressed by the difference between autoregulated and maximally vasodilated flow. In hypertension the raised coronary resistance reduces the steepness of the pressure-flow relationship at maximal vasodilatation. In the presence of cardiac hypertrophy the line of autoregulated flow becomes higher. For these reasons coronary reserve is reduced and the point at which baseline flow approaches the maximal achievable flow might be shifted to a higher perfusion pressure. Thus, any reduction below this elevated and critical value of pressure would lower the coronary flow. METHODS AND RESULTS. The investigated patients were normotensive (controls, nine) and hypertensive with normal (group I, seven) or augmented LV mass index because of concentric LV hypertrophy (group II, eight). All had effort-induced angina and angiographically normal left epicardial branches. Flow in the great cardiac vein was measured by thermodilution in the baseline and during stepwise (5 mm Hg every 5 minutes) decrease of the coronary perfusion pressure with a titrated nitroprusside i.v. infusion; perfusion pressures of 60 mm Hg in the controls and 70 mm Hg in the hypertensives were taken as end points. Baseline flow averaged 102 ml/min in normotensives, 104 ml/min in hypertensive group I and 148 ml/min in hypertensive group II. At the end points flow was similar to baseline in the controls and group I. In group II coronary flow started to decline and myocardial O2 extraction started to slightly but significantly rise at perfusion pressures of 90-80 mm Hg; at the end point flow was reduced by 26% (p less than 0.01 from baseline). The perfusion patterns did not seem to be related to the changes in tension-time index and heart rate. CONCLUSIONS. The association of high blood pressure (reduced ability of the coronary arterioles to dilate) and hypertrophy of the myocardium (augmented baseline coronary flow) may shift the point of exhaustion of coronary reserve to a higher perfusion pressure and make the myocardium vulnerable to treatment-induced relative hypertension.     

Intact nitric oxide production is obligatory for the sustained flow response during hypercapnic acidosis in guinea pig heart

OBJECTIVE: The mechanisms underlying hypercapnic coronary dilation remain unsettled. This study tests the hypothesis that flow dependent NO production is obligatory for the hypercapnic flow response. METHODS/RESULTS: In isolated, constant pressure (CP) perfused guinea pig hearts a step change of arterial pCO(2) from 38.6 to 61.4 mm Hg induced a bi-phasic flow response with an early transient (maximum 60 s) and a consecutive persisting flow rise (121.6+/-6.6 (S.D.) % after 10 min). In contrast, when perfused with constant flow (CF), perfusion pressure only transiently (2 min) fell by 7.4+/-4.8 % following the step change of arterial pCO(2). In CP perfused hearts L-NAME (100 micromol/l) specifically abolished the delayed flow rise during hypercapnic acidosis (102.37+/-2.9% after 10 min), whereas the inhibitor had no effect on perfusion pressure response in CF perfused hearts. Under CP perfusion arterial hypercapnia resulted in a transient rise of coronary cGMP release (from 0.69+/-0.35 to 1.12+/-0.68 pmol/ml), which was abolished after L-NAME. Surprisingly, the K(+)ATP channel blocker glibenclamide did not have any significant effect on the hypercapnic flow response but largely blunted reactive hyperemia after a 20 s flow stop. CONCLUSIONS: The delayed steady state hypercapnic flow response in guinea pig heart requires intact NO production. The absence of a persisting decrease in coronary resistance under CF perfusion points to an important role of shear stress dependent NO production.     

Functional characteristics of intramyocardial capacitance vessels during diastole in the dog

In order to evaluate the functional characteristics of the intramyocardial capacitance vessels during prolonged diastole, we analyzed the response of coronary vein flow after stepwise changes of coronary artery pressure in anesthetized open-chest dogs by using our newly developed laser Doppler velocimeter with an optical fiber. The peripheral portion of the great cardiac vein was isolated and the optical fiber tip was inserted into the vessel. The left anterior descending coronary artery was cannulated and connected to a reservoir to regulate coronary perfusion pressure. Intracoronary adenosine administration was carried out to avoid any change in coronary vasomotor tone. After 15 seconds of occlusion of the perfusion route, the heart was arrested by pacing-off. Two seconds later, coronary perfusion pressure was increased stepwise to a preset target pressure. This procedure was repeated by changing target pressure at 4 (or 5) different pressure levels (31-105 mm Hg). The great cardiac vein flow became zero due to the cardiac arrest and remained at zero for a moment (dead time) after the initiation of reperfusion. Then the flow reappeared and increased with first order time delay. The presence of dead time indicates the existence of unstressed volume, and the first order time delay represents the product of resistance and capacitance. The unstressed volume with a minimal vasomotor tone for perfusion pressure of 60-90 mm Hg was 5.2 +/- 2.2 ml per 100 g left ventricle, which is comparable to coronary blood flow for several beats. The capacitance at perfusion pressure of 60-90 mm Hg was 0.08 +/- 0.04 ml/mm Hg per 100 g left ventricle, while that at low perfusion pressure (30-50 mm Hg) was 0.14 +/- 0.09 ml/mm Hg per 100 g left ventricle. These results indicate that the intramyocardial capacitance vessels have two functional components, and that the phasic nature of coronary vein flow is solely the result of the myocardial squeezing of the blood in the capacitance vessels.     

Ultrasound energy improves myocardial perfusion in the presence of coronary occlusion

OBJECTIVES: We evaluated whether ultrasound improves myocardial tissue perfusion in 14 animals with coronary artery occlusion. BACKGROUND: A recent study demonstrated that low-frequency ultrasound improves tissue perfusion in the rabbit ischemic limb, but there are no data on ultrasound enhancement of myocardial perfusion. METHODS: Fourteen animals (9 dogs, 5 pigs) underwent thoracotomy and occlusion of a diagonal branch of the left anterior descending coronary artery. Myocardial tissue perfusion units (TPUs) and pH were measured before coronary occlusion, after occlusion, and after direct exposure of the ischemic myocardium in the presence of fixed occlusion to low-frequency ultrasound (27 kHz). RESULTS: The TPU decreased from 100.9 +/- 13 at baseline to 71.1 +/- 13 (p < 0.01) after 60 min occlusion but rose by 19.7% to 85.1 +/- 8 (p < 0.01) after ultrasound exposure for 60 min. After 60-min coronary occlusion, myocardial pH fell from 7.43 +/- 14 to 7.05 +/- 0.15 (p < 0.01) but then improved to normal (7.46 +/- 0.32) after ultrasound for 60 min. Administration of L-Nomega-nitro-arginine methyl esther (L-NAME), an inhibitor of nitric oxide synthase, before ultrasound exposure, blocked improvement in myocardial tissue perfusion and pH by ultrasound. Quantitative histomorphology showed a significant increase in the capillary area of myocardium exposed to ultrasound versus non-exposed myocardium (16.2 +/- 7.9 vs. 8.2 +/- 2.1, p < 0.02). CONCLUSIONS: Low-frequency, low-intensity ultrasound improves myocardial tissue perfusion and pH in the presence of a fixed coronary artery occlusion.     

Identification of less-irradiating tube angulations in invasive cardiology

OBJECTIVES: We sought to identify tube angulations in invasive cardiology, which promise minimal radiation exposure to patients and operators. BACKGROUND: Radiation exposure in invasive cardiology is high. METHODS: We mapped the fluoroscopic dose-area product per second (DAP/s), applied to an anthropomorphic Alderson-Rando phantom and, in absence of radiation protection devices, the mean personal dose in the operator's position in 10 degrees steps from the 100 degrees right anterior oblique (RAO) to the 100 degrees left anterior oblique (LAO) projection, as well as for all geometrically feasible craniocaudal tube angulations. RESULTS: For our specific setting conditions RAO 20 degrees /0 degrees tube angulation generated the lowest DAP/s and operator's personal dose. The mean patient DAP/s and operator personal dose for all postero-anterior (PA) projections, cranialized and caudalized together, rose significantly: 3.7 and 10.6 times the PA 0 degrees baseline values toward LAO 100 degrees and 3.7 and 2.4 times toward RAO 100 degrees , respectively. Patient and operator values for all PA projections, angulated to the right and left, increased approximately 2.5 times toward 30 degrees craniocaudal angulations. Caudal PA 0 degrees /30 degrees - angulation instead of caudal LAO 60 degrees /20 degrees - angulation for the left coronary main stem and cranial PA 0 degrees /30 degrees + view in place of cranial LAO 60 degrees /20 degrees + view for the left anterior descending coronary artery bifurcation enable 2.6-fold dose reductions to the patient and eight- and five-fold dose reductions to the operator, respectively. CONCLUSIONS: The PA views and RAO views >or=40 degrees , heretofore unconventional in clinical routine, should be favored over steep LAO projections >or=40 degrees whenever possible. Tube angulations that are radiation intensive to the patient exponentially increase the operator's radiation risk.     

Developments towards the slice-wise three-dimensional reconstruction of the distribution of the contrast perfusion in the myocardial muscle from biplane angiographic views

Summary In theory, radiographic myocardial perfusion imaging allows a quantitative assessment of the functional significance of a coronary stenosis. However, in the conventional two-dimensional projection images there does not exist a one-two-one relationship between a selected myocardial region of interest (ROI) and one particular coronary segment perfusing that area due to over-projection of myocardial regions in front of and behind the selected ROI perfused by other arterial segments, which may result in measurements which are difficult to interpret or even unreliable. To overcome these problems, we have developed two algorithms to determine the spatial distribution of perfusion levels in slices of the heart, selected approximately perpendicular to the left ventricular long axis, from two orthogonal angiographic views: the Segmental Reconstruction Technique (SRT) and the Network Programming Reconstruction Technique (NPRT). Both techniques requirea priori geometric information about the myocardium, which can be obtained from the epicardial coronary tree (epicardial boundaries) and the left ventricular lumen (endocardial boundaries).Using the SRT approach, pie-shaped segments are defined for each slice within the myocardial geometric constraints such that superimposition of these segments when projected in orthogonal biplane views is minimal. The reconstruction process uses a model with identical myocardial geometry and definition of segments. Each segment of the model is assigned a relative perfusion level with unit one if no othera priori information is available. In this case, the model contains geometric information only. In casea priori information about expected segmental perfusion levels is available, a level between zero and one is assigned to each segment. Thea priori information on the myocardial perfusion levels can be extracted from either anatomic information about the location and severity of existing coronary arterial obstructions, or from a slice adjacent to the one under reconstruction.Using the NPRT approach perfusion levels are computed for each volume picture element of a slice within the reconstructed myocardial geometry, thus resulting in a much higher spatial resolution than the SRT approach.A priori information of perfusion levels must be included in this approach, again based upon anatomical information, or upon the slice adjacent to the one under reconstruction. The very first slice of a myocardial study will be reconstructed by the SRT approach.Extensive computer simulations for the SRT have proved that the mean difference between the actual and reconstructed segmental perfusion levels, on a scale from 0 to 1, is smaller than 0.45 (SEE=0.0033, REE=1.80) for various coronary artery disease states without the use ofa priori information on expected perfusion levels. This error becomes smaller than 0.36 (SEE=0.0026, REE=1.42), ifa priori information in the reconstruction technique is included. Similar computer simulations for the NPRT have proved that these mean differences, in geometric segments equal to those defined for the SRT, are smaller than 2.94 (SEE=0.0308, REE=0.77) on a scale from 0 to 16, without the use ofa priori information on expected perfusion levels, and smaller than 1.72 (SEE=0.0304, REE=1.10) on the same scale whena priori information is included. Therefore, it may be concluded that slice-wise three-dimensional reconstruction of perfusion levels is feasible from biplane computer-simulated data, and that a similarity exists for mean perfusion levels in corresponding regions in the simulated and reconstructed slices, for various states of single coronary artery disease.