The effect of balloon dilatation on post-stenotic myocardial perfusion before and after stimulation of coronary flow reserve: evaluation by the densitometric parameter ''mean rise time''

Summary From densitometric evaluation of digital subtraction cineangiocardiograms the parameter Mean Rise Time (MRT), defined as the time from the onset of local myocardial contrast medium opacification to the point of maximal opacification can be derived; this parameter revealed a close correlation with the results on myocardial perfusion obtained by Thallium-201 scintigraphy. A prolonged Mean Rise Time was indicative of an impairment of myocardial perfusion.We have developed a heart-phase gated real-time digitization procedure and computer-supported method for the densitometric estimation of the MRT to obtain information about the effect of coronary balloon dilatation on myocardial perfusion before and after stimulation of coronary flow reserve by Moxaverin. In 22 patients with single vessel coronary artery disease Moxaverin caused a significant prolongation of the post-stenotic MRT (2.3±1.2s (mean ± s.d.) vs. 2.9±1.1s, p<0.05), while after successful dilatation of the obstructive lesion a significant shortening of the MRT was found after stimulation of the coronary flow reserve (2.5±1.2s vs. 1.9±0.9s, p<0.05). A highly significant decrease in MRT after Moxaverin was measured post-dilatation in comparison to the initial pre-dilatation results (2.9±1.1s vs. 1.9±0.9s, p<0.005); this shows that the effect of successful balloon dilatation on the post-stenotic myocardial perfusion can be described very well by this parameter. These results demonstrate that information about post-stenotic myocardial perfusion during interventional heart catheterization can be obtained from digital densitometry.     

TIMI myocardial perfusion frame count: A new method to assess myocardial perfusion and its predictive value for short‐term prognosis

Objectives: We sought to develop a new quantitative method to evaluate the degree of myocardial perfusion. Background: Currently available methods for assessing myocardial perfusion, both TIMI myocardial perfusion grading (TMPG) and myocardial blush grading (MBG), are subjective. Methods: TIMI Myocardial Perfusion Frame Count (TMPFC), an objective method that measures the filling and clearance of contrast in the myocardium using cine‐angiographic frame‐counting, was developed to quantify myocardial perfusion. Myocardial perfusion of 45 normal coronary arteries in 15 patients, and 137 culprit arteries in 137 patients immediately after primary angioplasty, was successfully assessed with TMPFC. Results: The mean TMPFC in the normal arteries was 83.47 ± 17.96 frames (95% CI: 78.07 frames ≤ TMPFC ≤ 88.86 frames). Therefore, TMPFC < 90 frames, a value representing the upper bound of the 95% CI for the TMPFC observed in normal arteries, was defined as normal myocardial perfusion. In 137 culprit arteries, the mean TMPFC values after primary angioplasty for the right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex artery (LCX) were 141 ± 82.6, 112 ± 80.3, and 102 ± 37.5 frames, respectively. Patients with suboptimal myocardial perfusion (ex: TMPG ≤ 2 or MBG ≤ 2 grade) had higher levels of TMPFC. Furthermore, multivariate analysis shows that the TMPFC was an independent predictor for 30‐day (P = 0.0261) and 6‐month incidence of MACE (P = 0.0207). Conclusions: TMPFC is a quantitative index for the assessment of myocardial perfusion; it allows quantification of TMPG and may serve as a discerning tool to predict prognosis in patients undergoing primary angioplasty. © 2009 Wiley‐Liss, Inc.     

Evaluation of the long-term functional outcome assessed by myocardial perfusion scintigraphy following excimer laser angioplasty compared to balloon angioplasty in longer coronary lesions

Objectives: Evaluation of the long-term functional outcome assessed by exercise myocardial perfusion imaging following excimer laser angioplasty compared to balloon angioplasty in coronary lesions >10 mm in length. Background: Previous randomized studies evaluating the effect of coronary interventions mainly focused on the long-term clinical and angiographic outcome. The functional outcome, assessed by myocardial perfusion scintigraphy, has not been evaluated in a randomized setting. Methods: A total of 308 patients with stable angina and a longer coronary lesion (>10 mm) were randomized to excimer laser angioplasty or balloon angioplasty. A ^99mTechnetium-2-methoxy isobutyl isonitrile (MIBI) single-photon emission computed tomography (SPECT) study was performed in 139 patients before the initial angioplasty procedure and at 6 months follow-up (73 patients in the laser group versus 66 patients in the balloon group, respectively). Exercise tolerance at follow-up was compared to baseline values by means of exercise duration and double product at peak exercise. Myocardial perfusion of the randomized vascular bed was assessed semi-quantitatively on the MIBI SPECT images. The reversible defects were graded as mild, moderate or severe. Myocardial perfusion at follow-up was expressed as a percentage reduction in incidence and grading of the reversible defects compared to baseline values. Results: Forty-four (61%) patients assigned to laser angioplasty were asymptomatic at 6 months follow-up compared to 34 (52%) patients assigned to balloon angioplasty (p = NS). Improvement in exercise duration and double product were 0.7 ± 2.1 min and 4.3 ± 6.2 min/mmHg/1000, respectively, in the laser group, versus 0.3 ± 2.5 min and 3.1 ± 5.5 min/mmHg/1000, respectively, in the balloon group (both p = NS). The percentage reduction of reversible defects was 23% in patients assigned to laser angioplasty vs. 29% in patients assigned to balloon angioplasty (Relative risk [RR]: 0.79, 95% confidence interval [CI]: 0.40–1.57; p = 0.50). The mild, moderate and severe reversible defects improved in 44.4, 63.6 and 66.6%, respectively, in the laser angioplasty group vs. 66.6, 53.8 and 90%, respectively, in the balloon angioplasty group. None of the comparisons were significantly different. Conclusion: Excimer laser angioplasty compared to balloon angioplasty in coronary lesions >10 mm in length yields a similar long-term functional outcome assessed by anginal status, exercise tolerance and myocardial perfusion.     

超声心肌声学造影评价冠状动脉狭窄程度对心肌灌注的影响

目的经冠状动脉超声心肌声学造影(MCE)检测基础状态下不同狭窄程度冠状动脉所供应心肌组织灌注状况。方法30例患者行选择性冠状动脉造影,按有无冠状动脉病变及病变血管狭窄程度,将所涉及的共93个心肌节段分为对照组(18个)和病变组(75个),其中病变组又分为轻度狭窄组(12个)、中度狭窄组(28个)、重度狭窄组(35个);超声声学造影剂由冠状动脉直接注入,完成MCE。对心肌灌注进行定性分析,并由心肌灌注时间强度曲线进行定量分析。结果112个心肌节段中有93个(83.0%)获得较满意图像,经视觉判断,病变组共75个心肌节段中,正常灌注的为58个(77.3%),低灌注为17个(22.7%),其中,轻度狭窄组均为正常心肌灌注。定量分析显示,重度狭窄组反映心肌灌注的3个参数值与对照组均存在明显差异(P<0.05);而轻、中度狭窄组各参数值与对照组无明显差异。结论基础状态下,狭窄程度>90%的冠状动脉病变,其心肌组织灌注水平较正常偏低;而当血管狭窄程度≤90%时,心肌灌注水平与正常相似。     

Arterial blood infusion for myocardial protection during percutaneous transluminal coronary angioplasty

Much of the potential risk of percutaneous transluminal coronaryangioplasty relates to regional myocardial ischaemia duringballoon inflation. We have investigated the protective effectof infusing arterial blood through the angioplasty catheterinto the distal coronary artery during 60 second balloon inflations.Symptomatic, electrocardiographic and echocardiographic indicesof regional ischaemia were monitored during inflations withand without blood infusion. The effect of infusing Hartmann'ssolution was also evaluated to control for washout effects.Twelve patients were studied. Inflation without blood producedchest pain in eight patients, ST-segment elevation in ten patientsand regional wall motion abnormalities in every case. Duringblood infusion manifestations of ischaemia were either delayedor prevented altogether. Chest pain occurred in only one patientwhile ST segment elevation and regional wall motion abnormalitiesoccurred in three and four patients, respectively. Infusionof Hartmann's solution, on the other hand, had no significanteffect on the development of regional myocardial ischaemia duringballoon inflation indicating that delivery of arterial oxygenand not washout of metabolites was responsible for the beneficialeffects of blood infusion. These data indicate that distal coronaryperfusion with arterial blood during angioplasty reduces regionalmyocardial ischaemia and has the potential to improve the safetyof the technique and to permit more prolonged periods of ballooninflation.     

Maximal myocardial perfusion by videodensitometry in the assessment of the early and late results of coronary angioplasty: Relationship with coronary artery measurements and left ventricular function at rest

In the assessment of the acute results of percutaneous transluminal coronary angioplasty (PTCA), myocardial perfusion at maximal vasodilatation theoretically has fewer limitations than the coronary flow reserve measurements and quantitative coronary angiography. The purpose of this study was to compare the myocardial perfusion to the measurements of the severity of the lesion (minimal luminal diameter and percent area stenosis) and to relate it to the changes of left ventricular function after PTCA. Regional myocardial perfusion was assessed during intracoronary papaverine, using the inverse mean transit time of contrast medium (1/T_mn), before, 15 min after, 18—24 hr after, and 6 months after successful single-vessel PTCA in 14 patients with stable angina. Left ventricular angiography (before angioplasty, 18—24 hr after, and 6 months later) was analysed by area-length and centerline methods. Immediately after PTCA, 1/T_mn increased from 0.14 ± 0.07 sec^?1 to 0.21 ± 0.09 sec^?1 (P = .001). Maximal myocardial perfusion remained higher than the pre-PTCA value the day after angioplasty (1/T_mn of 0.23 ± 0.09 sec^?1), while it reduced to near pre-PTCA values at follow-up (1/T_mn of 0.16 ± 0.05 sec^?1). Before PTCA, three out of ten patients had ejection fraction of <65%, and seven had mild-to-moderate hypokinesis. The day after PTCA the ejection fraction and the regional dysfunction improved significantly. The change in ejection fraction 18—24 hr after PTCA did not correlate with minimal luminal diameter and percent area stenosis and correlated slightly with the improvement of perfusion (r = 0.54, P = .10). At follow-up left ventricular function deteriorated in the whole group, despite the persistence of angiographic success of PTCA, possibly because of changes in the loading condition. Coronary artery stenosis measurements and 1/T_mn failed to correlate with the left ventricular function. Given the difficulties in routine application of the analysis of time-density curves, the measurement of minimal luminal diameter remains a more practical assessment of the results of the intervention. However, the improvement of myocardial perfusion may give more information than coronary artery dimensions of the early recovery of left ventricular function.     

Double perfusion system for coronary angioplasty at the origin of the main vessel

For the treatment of stenosis near the origin of either the left anterior descending artery or the left circumflex artery, one autoperfusion catheter was used to dilate the lesion while another was used to maintain perfusion of the nonstenosed vessel, which would normally suffer from a decrease in blood flow. This technique was applied to nine procedures in six patients. The balloon could be inflated for more than 60 sec in all cases. Satisfactory dilation was achieved without a significant decrease of systemic blood pressure during the procedure. © 1994 Wiley-Liss,Inc..     

Novel perfusion sleeve for use during balloon angioplasty: Initial clinical experience

The perfusion sleeve (PS) is an “over-the-balloon” catheter designed to add perfusion capability to standard PTCA catheters. To evaluate the clinical effectiveness of this device, eight patients underwent standard PTCA with the PS retracted in the guide (Inflation 1-Control) and after deployment of the PS (Inflation 3-Control). Between standard inflations the PS was advanced and aligned with the already positioned PTCA balloon which was inflated for up to 15 minutes (Inflation 2-Perfusion). TIMI III flow was present in 5/7 and TIMI II flow in 2/7 patients during Inflation 2-Perfusion. Absolute ST segment shift (mm) on the ECG was significantly less at 3 minutes and prior to balloon deflation with the PS in place (1.0 ± 1.4 and 1.1 ± 1.1 mm) compared to Inflation 1-Control and Inflation 3-Control (2.6 ± 1.3 and 2.3 ± 0.3 mm) respectively (P ≤ 0.05). Use of the PS in conjunction with standard PTCA is feasible, provides perfusion during prolonged balloon inflations and reduces the magnitude of ischemia. Cathet. Cardiovasc. Diagn. 44:358–362, 1998. © 1998 Wiley-Liss, Inc.     

Transmural regulation of myocardial perfusion by neuropeptide Y

In vivo studies have shown that sympathetic nerve stimulation improves the transmural distribution of myocardial perfusion by increasing the endocardial/epicardial flow ratio; however, the mechanism of this effect is unknown. During nerve stimulation both norepinephrine (NE) and neuropeptide Y (NPY) are released, either or both of which may exert vasoconstrictor effects. The present studies were performed to examine the effects of these two cotransmitters on the transmural distribution of myocardial perfusion in a canine model. In anesthetized open-chest dogs, during maximal coronary vasodilation with intracoronary adenosine, both neuropeptide Y (29.7 g/min) and norepinephrine (0.5–2.0 g/min) reduced myocardial perfusion to a greater extent in the epicardium than in the subendocardium. The endo/epi ratio with adenosine alone was 1.11±0.02 Norepinephrine increased this by 80%, neuropeptide Y by 20%, and the combination of the two by 76% (P<0.05 for all three vs. adenosine). Neuropeptide Y alone constricted the coronary vasculature but did not alter transmural flow. Thus neuropeptide Y preferentially reduces myocardial perfusion in the epicardium. We speculate that neuronally released neuropeptide Y contributes importantly to the transmural distribution of myocardial perfusion during sympathetic nerve stimulation.     

Residual myocardial perfusion in reversibly damaged myocardium by dipyridamole contrast echocardiography

In patients with previous myocardial infarction and left ventricularasynergy, dipyridamole infusion may have the capacity to unmaskmyocardial viability through transient recovery of contractilefunction in asynergic segments. The purpose of this study wasto assess simultaneous changes in myocardial perfusion and LVfunction—elicited by dipyridamole infusion—in infarcted,asynergic segments. The echo contrast agent Albunex was injectedinto the left coronary artery of 19 patients (17 males, age49–70 years) with previous myocardial infarction and baselineleft ventricular asynergy, both before and after dipyridamoleinfusion (up to 0·56 mg. kg^–1, i.v.). Analysiswas not possible in three patients due to inadequate image qualityand in two due to weak contrast. There were no major adverseevents, or changes in vital signs or demonstrated on the electrocardiogram.After dipyridamole, 7/14 patients, showed an improvement inregional function of asynergic segments (‘responders’),whereas seven patients did not (‘non-responders’).Among non-responders, five had a myocardial perfusion deficitcorresponding to 41% of the total left ventricular area beforedipyridamole and to 38% after dipyridamole. No baseline perfusiondeficits were observed in the remaining two non-responders;one of these, however, developed transient asynergy and perfusiondeficit after dipyridamole. Among responders, five showed anormal perfusion pattern, both before and after dipyridamole,while the remaining two showed a perfusion deficit which markedlydecreased after dipyndamole (from 32% to 13% of total left ventriculararea). Thus, residual contractile reserve of asynergic, infarctedventricular segments appears to be associated with myocardialperfusion either preserved at baseline or recruitable by a coronarydilator stimulus.     

用声学密度定量技术早期评价急性心肌梗死患者直接经皮冠状动脉腔内成形术的疗效

目的　探讨利用声学密度 (AD)定量技术早期评价急性心肌梗死 (AMI)患者行直接经皮冠状动脉腔内成形术 (PTCA)的手术疗效。方法　将 4 0例AMI患者分为两组 :18例病人行直接PTCA治疗 (A组 ) ,2 2例病人用药物治疗 (B组 ) ,比较两组病人在入院第 7天时常规超声心动图检查和用AD技术检测的结果。结果　两组病人常规超声心动图各项检查结果比较差别无显著性 (P >0 0 5 )。AD定量检测结果 :A组的背向散射积分周期变化幅度 (CVIB) (4 2± 1 3)dB明显高于B组 (2 5± 2 4 )dB(P <0 0 1) ;A组校正的周期变化延迟时间 (N Delay) 1 0 9± 0 0 8明显低于B组 1 31± 0 16 (P <0 0 1) ;两组间背向散射积分 (IBS)差异无显著性 (P >0 0 5 )。结论　AD技术能够早期反映AMI再灌注心肌的组织学特征 ,为早期评价介入治疗效果、预测心功能改善情况、判定心肌活性提供了一种新的技术手段。     

Comparison between regional myocardial perfusion reserve and coronary flow reserve in the canine heart

Diameter stenosis and flow reserve are indices of morphologicaland functional severity of coronary artery stenosis. Flow reservecan be determined at coronary arterial or at myocardial level.In the presence of functional collateral circulation, coronaryflow reserve and myocardial perfusion reserve may differ. We studied coronary flow, coronary flow reserve and myocardialperfusion reserve in an open chest dog model with intact collateralcirculation, before and after induction of coronary artery stenosis.Coronary flow was determined with perivascular ultrasonic flowprobes and myocardial perfusion reserve from digital angiographicimages, in the stenotic as well as the adjacent non-stenoticcoronary arteries. Before induction of a stenosis, a significant correlation existedbetween coronary flow reserve and myocardial perfusion reserveof the left anterior descending (r=0·59; P<0·005)and the left circumflex arteries (r=0·84, P<0·005).In stenotic arteries, coronary flow reserve and myocardial perfusionreserve decreased significantly (P<0·005), but inthe adjacent non-stenotic arteries coronary flow reserve wasnot affected Myocardial perfusion reserve in the non-stenoticadjacent left anterior descending artery decreased significantly(P<0·05) and no correlation was found between coronaryflow reserve and myocardial perfusion reserve, whereas in theadjacent non-stenotic left circumflex artery there was no statisticallysignificant decrease (4·1 ± 1·6 3·5± 1·4) but there was a good correlation betweencoronary flow reserve and myocardial perfusion reserve (r=0·85;P<0·005). This study demonstrates that, in the presence of a stenosisand functioning collateral circulation, coronary flow reserveis not a reliable predictor of myocardial perfusion reserve;both parameters provide mutually complementary information.     

Comparison between regional myocardial perfusion reserve and coronary flow reserve in the canine heart

Diameter stenosis and flow reserve are indices of morphologicaland functional severity of coronary artery stenosis. Flow reservecan be determined at coronary arterial or at myocardial level.In the presence of functional collateral circulation, coronaryflow reserve and myocardial perfusion reserve may differ. We studied coronary flow, coronary flow reserve and myocardialperfusion reserve in an open chest dog model with intact collateralcirculation, before and after induction of coronary artery stenosis.Coronary flow was determined with perivascular ultrasonic flowprobes and myocardial perfusion reserve from digital angiographicimages, in the stenotic as well as the adjacent non-stenoticcoronary arteries. Before induction of a stenosis, a significant correlation existedbetween coronary flow reserve and myocardial perfusion reserveof the left anterior descending (r=0.59; P<0.005) and theleft circumflex arteries (r=0.84, P<0.005). In stenotic arteries,coronary flow reserve and myocardial perfusion reserve decreasedsignificantly (P<0.005), but in the adjacent non-stenoticarteries coronary flow reserve was not affected Myocardial perfusionreserve in the non-stenotic adjacent left anterior descendingartery decreased significantly (P<0.05) and no correlationwas found between coronary flow reserve and myocardial perfusionreserve, whereas in the adjacent non-stenotic left circumflexartery there was no statistically significant decrease (4.1± 1.6 3.5 ± 1.4) but there was a good correlationbetween coronary flow reserve and myocardial perfusion reserve(r=0.85; P<0.005). This study demonstrates that, in the presence of a stenosisand functioning collateral circulation, coronary flow reserveis not a reliable predictor of myocardial perfusion reserve;both parameters provide mutually complementary information.     

Quantitative contrast echocardiographic assessment of collateral derived myocardial perfusion during elective coronary angioplasty

OBJECTIVE—To determine whether myocardial contrast echocardiography can be used to quantify collateral derived myocardial flow in humans.
METHODS—In 25 patients undergoing coronary angioplasty, a collateral flow index (CFI) was determined using intracoronary wedge pressure distal to the stenosis to be dilated, with simultaneous mean aortic pressure measurements. During balloon occlusion, echo contrast was injected into both main coronary arteries simultaneously. Echocardiography of the collateral receiving myocardial area was performed. The time course of myocardial contrast enhancement in images acquired at end diastole was quantified by measuring pixel intensities (256 grey units) within a region of interest. Perfusion variables, such as background subtracted peak pixel intensity and contrast transit rate, were obtained from a fitted γ variate curve.
RESULTS—16 patients had a left anterior descending coronary artery stenosis, four had a left circumflex coronary artery stenosis, and five had a right coronary artery stenosis. The mean (SD) CFI was 19 (12)% (range 0-47%). Mean contrast transit rate was 11 (8) seconds. In 17 patients, a significant collateral contrast effect was observed (defined as peak pixel intensity more than the mean + 2 SD of background). Peak pixel intensity was linearly related to CFI in patients with a significant contrast effect (p = 0.002, r = 0.69) as well as in all patients (p = 0.0003, r = 0.66).
CONCLUSIONS—Collateral derived perfusion of myocardial areas at risk can be demonstrated using intracoronary echo contrast injections. The peak echo contrast effect is directly related to the magnitude of collateral flow.


Keywords: collateral circulation; quantitative myocardial contrast echocardiography; intracoronary pressure; myocardial perfusion     

Clinical methods to determine coronary flow and myocardial perfusion

In this overview, currently available clinical methods to measure flow in the coronary circulation will be discussed. Methods only applicable in the experimental laboratory or in the anaesthetized patient during cardiac surgery, will not be described. We distinguish between methods that measure global blood flow, and methods that determine regional flow, either at the level of the coronary arteries or at the level of the myocardium. Since it is difficult to measure coronary flow in absolute values, flow reserve is often used as an alternative. Flow reserve is calculated by dividing maximal flow, usually pharmacologically induced, by basal flow. Consequently, assessment of flow reserve requires only measurements of relative changes of coronary flow. The applicability and relative merits and limitations of the techniques are discussed.     

X-ray densitometry for the measurement of regional myocardial perfusion

The evaluation of regional myocardial blood flow (RMBF) during cardiac catheterization is of particular diagnostic interest. The purpose of this investigation was to validate x-ray densitometric parameters for the evaluation of RMBF. In five anesthetized dogs, arterial flow in the circumflex coronary artery was measured continuously with an electromagnetic flowmeter, and RMBF was determined by colored microspheres. Five different perfusion levels were created by mechanical obstruction of the coronary artery or by intravenous infusion of adenosine. At each steady-state perfusion level, digital subtraction coronary angiograms were obtained for densitometric analysis. Results documented a close correlation between the related time parameters 1/Mean Transit Time (1/MTT, r² = 0.969), and 1/Rise Time (1/RT, r² = 0.965) and RMBF over a wide range between 0.36 ml/(min · g) and 11.16 ml/(min · g). Maximum myocardial contrast density (Imax) also showed a good, but inverse correlation (r² = 0.889) with RMBF and, therefore, did not reflect vascular volume. Contrast medium Appearance Time (AT) showed no correlation to RMBF (r² = 0.017). Repeat densitometric measurements for different perfusion levels revealed a good reproducibility for MTT (accuracy: 0.001 s; precision: 0.447 s or 6.7%) and RT (accuracy: 0.014 s; precision: 0.202 s or 10.4%), while AT (accuracy: 0.072 s; precision: 0.420 s or 68.5%) and Imax (accuracy: 0.022 GL; precision: 1.197 GL or 44.5%) showed substantial variation. Myocardial perfusion reserve (MPR) calculated from RT (r² = 0.90) or MTT (r² = 0.94) showed better correlations to RMBF reserve than MPR calculated from AT (r² = 0.04). In conclusion, only 1/MTT and 1/RT showed a good reproducibility and a close correlation to RMBF. Therefore, only these parameters can be recommended for calculations of RMBF and its reserve under clinical conditions. Received: 2 November 1999, Returned for revision: 5 January 2000, Revision received: 1 February 2000, Accepted: 6 February 2000     

Intraoperative assessment of myocardial perfusion using contrast echocardiography

Myocardial contrast echocardiography is a new technique capable of assessing regional myocardial perfusion in vivo in real time. This article reviews the background, principles, experimental validation, and clinical uses of intraoperative myocardial contrast echocardiography. Data can be derived both for online visual and computer analyses. The technique can be useful in determining the sequence of bypass graft placement and the success of graft anastamoses. Anastamoses can be revised immediately if needed. It is hoped that this technique will improve intraoperative myocardial preservation and will diminish the rate of perioperative myocardial infarction.     

Mean transit time for videodensitometric assessment of myocardial perfusion and the concept of maximal flow ratio: A validation study in the intact dog and a pilot study in man

Summary Over the last decade it has become more and more obvious that besides anatomical information about the severity of coronary artery stenoses, information about coronary and myocardial blood flow is necessary to understand the functional significance of these obstructions and to evaluate the result of an intervention. Several methods have been proposed for this purpose, each of these having their particular limitations.In this study a new method is shortly described which allows the accurate calculation of relative maximal myocardial perfusion by ECG-triggered digital radiography (videodensitometry), using mean transit time (T_mn) as time parameter; this technique is based on the original physiologic principles of indicator dilution theory. This method was validated in 8 instrumented dogs in which an excellent linear relation was present between 1/T_mn and flow (r=0.96 ± 0.03). Although this method does not allow assessment of resting flow and therefore coronary flow reserve (CFR), it provides a means for the reliable comparison of maximal myocardial flow in different situations and it is independent of most factors affecting coronary flow reserve.The ratio between maximal flow after and before an intervention is called maximal flow ratio (MFR) and this concept was applied in a pilot study in man to evaluate PTCA results in 10 patients undergoing elective angioplasty. MFR was compared with the result of exercise testing 24 hours before and 10 days after the angioplasty. MFR 1.5 was always accompanied by reversal of exercise test result from positive to negative.We conclude that the accurate calculation of relative maximal perfusion of the myocardium is possible by videodensitometry and suggest that comparison of maximal flow after and before an intervention can be valuable in man for functional evaluation of the result of the intervention.     

Three-dimensional reconstruction of myocardial contrast perfusion from biplane cineangiograms by means of linear programming techniques

Summary The assessment of coronary flow reserve from the instantaneous distribution of the contrast agent within the coronary vessels and myocardial muscle at the control state and at maximal flow has been limited by the superimposition of myocardial regions of interest in the two-dimensional images. To overcome these limitations, we are in the process of developing a three-dimensional (3D) reconstruction technique to compute the contrast distribution in cross sections of the myocardial muscle from two orthogonal cineangiograms. To limit the number of feasible solutions in the 3D-reconstruction space, the 3D-geometry of the endo- and epicardial boundaries of the myocardium must be determined. For the geometric reconstruction of the epicardium, the centerlines of the left coronary arterial tree are manually or automatically traced in the biplane views. Next, the bifurcations are detected automatically and matched in these two views, allowing a 3D-representation of the coronary tree. Finally, the circumference of the left ventricular myocardium in a selected cross section can be computed from the intersection points of this cross section with the 3D coronary tree using B-splines. For the geometric reconstruction of the left ventricular cavity, we envision to apply the elliptical approximation technique using the LV boundaries defined in the two orthogonal views, or by applying more complex 3D-reconstruction techniques including densitometry. The actual 3D-reconstruction of the contrast distribution in the myocardium is based on a linear programming technique (Transportation model) using cost coefficient matrices. Such a cost coefficient matrix must contain a maximum amount of a priori information, provided by a computer generated model and updated with actual data from the angiographic views. We have only begun to solve this complex problem. However, based on our first experimental results we expect that the linear programming approach with advanced cost coefficient matrices and computed model will lead to acceptable solutions in the 3D-reconstruction of the myocardial contrast distribution from biplane cineangiograms.     

Quantitative automated assessment of myocardial perfusion at cardiac catheterization

Perfusion assessed in the cardiac catheterization laboratory predicts outcomes after myocardial infarction. The aim of this study was to investigate a novel method of assessing perfusion using digital subtraction angiography to generate a time-density curve (TDC) of myocardial blush, incorporating epicardial and myocardial perfusion. Seven pigs underwent temporary occlusion of the left anterior descending coronary artery for 60 minutes. Angiography was performed in the same projections before, during, and after occlusion. Perfusion parameters were obtained from the TDC and compared with Thrombolysis In Myocardial Infarction (TIMI) frame count and myocardial perfusion grade. In addition, safety and feasibility were tested in 8 patients after primary percutaneous coronary intervention. The contrast density differential between the proximal artery and the myocardium derived from the TDC correlated well with TIMI myocardial perfusion grade (R = 0.54, p <0.001). The arterial transit time derived from the TDC correlated with TIMI frame count (R = 0.435, p = 0.011). Using a cutoff of 2.4, the density/time ratio, a ratio of density differential to transit time, had sensitivity and specificity of 100% for coronary arterial occlusion. The positive and negative predictive values were 100%. The generation of a TDC was safe and feasible in 7 patients after acute myocardial infarctions, but the correlation between TDC-derived parameters and TIMI parameters did not reach statistical significance. In conclusion, this novel method of digital subtraction angiography with rapid, automated, quantitative assessment of myocardial perfusion in the cardiac catheterization laboratory correlates well with established angiographic measures of perfusion. Further studies to assess the prognostic value of this technique are warranted.