On the statistical modelling of coronary arteriographic data: dynamics of coronary atherosclerosis related to systemic and focal parameters. REGRESS Study Group. Regression Growth Evaluation Statin Study

Existing methods to analyse data from repeated arteriographic progression/regression studies are restrictive and do not fully explore the dynamics of coronary artherosclerosis. We present a new approach making a distinction between new occlusions, new lesions, and growth of existing lesions. Random effect models, based on the logistic, the Poisson, and the normal distribution are proposed with correlation depending on distance. The data from the Regression Growth Evaluation Statin Study (REGRESS) are used to validate the model. Lipid lowering treatment of pravastatin resulted in less growth of existing lesions and fewer new lesions than when placebo was given. Fewer new lesions were found in segments influenced by percutaneous transluminal coronary angioplasty (PTCA) than in segments not influenced by PTCA. Similarly, the growth of lesions influenced by PTCA was smaller than lesions not influenced by PTCA. More new occlusions were found in segments influenced by coronary arterial bypass grafting (CABG) than in segments not influenced by CABG, but 98 per cent of the new occlusions were located proximal to the bypass anastomosis. Similarly, existing lesions proximal to the bypass anastomosis showed larger growth (p < 0.001). We conclude that our new approach for analysing the arteriographic data from repeated coronary arteriographic studies appeared a fruitful way to analyse the dynamics of coronary atherosclerosis.

Comparison between manual and semiautomated analysis of left ventricular volume parameters from short-axis MR images

PURPOSE

The goal of this study was to evaluate a newly developed semiautomated contour detection algorithm for the quantitative analysis of cardiovascular MRI.

METHOD

Left ventricular function parameters derived from automatically detected endocardial and epicardial contours were compared with results derived from manually traced contours in short-axis multislice GRE MRI studies of 10 normal volunteers and 10 infarct patients.

RESULTS

Compared with manual image analysis, the semiautomated method resulted in the following systematic and random differences (auto-manual; mean +/- SD): end-diastolic volume: -5.5 +/- 9.7 ml; end-systolic volume: -3.6 +/- 6.5 ml; ejection fraction: 1.7 +/- 4.1%; left ventricular mass: 7.3 +/- 20.6 g. Total analysis time for a complete study was reduced from 3-4 h for the manual analysis to < 20 min using semiautomated contour detection.

CONCLUSION

Global left ventricular function parameters can be obtained with a high degree of accuracy and precision using the present semiautomated contour detection algorithm.

Assessment of regional left ventricular wall parameters from short axis magnetic resonance imaging using a three-dimensional extension to the improved centerline method

RATIONALE AND OBJECTIVES

Short-axis magnetic resonance images of the cardiac left ventricle, acquired in multiple slices and phases, may be used for the quantitative assessment of regional wall parameters. Conventional two-dimensional (2-D) methods for wall thickness measurement rely on information within one imaging plane, which may result in overestimation of the true thickness depending on the local direction of myocardial wall with respect to the imaging plane.

METHODS

To perform wall thickness measurements truly perpendicular to the myocardial wall, a three-dimensional (3-D) wall thickness calculation algorithm has been developed based on the 2-D improved centerline method. An evaluation was performed on left ventricular-shaped software phantoms, and on the magnetic resonance (MR) imaging data obtained from 20 healthy individuals.

RESULTS

The 3-D method applied to software phantoms with an angulation within 20 degrees of the true short-axis orientation demonstrated only a 1.6% overestimation of wall thickness at the mid to low slices, and a 10.6% error at the apex (2-D measurements: 8.1% and 28.6%, respectively). Three-dimensionally calculated wall thickness in the healthy individuals was systematically and significantly smaller than corresponding 2-D wall thickness (by 11.2%, 8.7%, and 2.6% at the apical, low, and mid slices, respectively).

CONCLUSIONS

Cardiac wall thickness measurements from short-axis MR studies can be obtained with a higher accuracy by the newly developed 3-D approach than with the conventional 2-D approach.

Quantitative assessment of the presence of a single leg separation in Björk-Shiley convexoconcave prosthetic heart valves

RATIONALE AND OBJECTIVES

The authors developed an analytic software package for the objective and reproducible assessment of a single leg separation (SLS) in the outlet strut of Björk-Shiley convexoconcave (BSCC) prosthetic heart valves.

METHODS

The radiographic cinefilm recordings of 18 phantom valves (12 intact and 6 SLS) and of 43 patient valves were acquired. After digitization of regions of interest in a cineframe, several processing steps were carried out to obtain a one-dimensional corrected and averaged density profile along the central axis of each strut leg. To characterize the degree of possible separation, two quantitative measures were introduced: the normalized pit depth (NPD) and the depth-sigma ratio (DSR). The group of 43 patient studies was divided into a learning set (25 patients) and a test set (18 patients).

RESULTS

All phantom valves with an SLS were detected (sensitivity, 100%) at a specificity of 100%. The threshold values for the NPD and the DSR to decide whether a fracture was present or not were 3.6 and 2.5, respectively. On the basis of the visual interpretations of the 25 patient studies (learning set) by an expert panel, it was concluded that none of the patients had an SLS. To achieve a 100% specificity by quantitative analysis, the threshold values for the NPD and the DSR were set at 5.8 and 2.5, respectively, for the patient data. Based on these threshold values, the analysis of patient data from the test set resulted in one false-negative detection and three false-positive detections.

CONCLUSIONS

An analytic software package for the detection of an SLS was developed. Phantom data showed excellent sensitivity (100%) and specificity (100%). Further research and software development is needed to increase the sensitivity and specificity for patient data.

Effect of lossy data compression on quantitative coronary measurements

With the accepted use of (lossy) data compression at low compression factors (2, 3 and 4 on the Philips DCI), the question was posed whether higher lossy compression ratios can also be used without statistically affecting the results of quantitative coronary arteriography. In this study the influence of two data compression schemes (LOT and JPEG) at three different compression factors (5, 8 and 12) on coronary measurements was assessed with the Automated Coronary Analysis (ACA) package. A series of 30 original acquired digital images were compressed and decompressed at the different factors, and together with the original non-compressed images processed using the ACA package. In these images a total of 37 obstructed coronary segments were analyzed twice to assess the intra-observer variabilities in the obstruction and reference diameters and in the percent diameter stenosis. The results of the first and second measurements in each image were averaged, and from the differences in corresponding images with different compression ratios, the inter-compression variability was obtained. The results show that the intra-observer systematic errors in the absolute diameters are all small (< 0.07 mm), and statistically not significantly different. The intra-observer random errors for the compressed/decompressed series, however, were all larger (up to 0.21 mm) than for the original series (< 0.13 mm). Statistically significant differences in the intra-observer random errors were found for the JPEG compression scheme at a compression ratio of 5 and for the LOT scheme at a compression ratio of 12. The inter-compression systematic errors in the absolute diameter measurements were also small (< 0.07 mm) and not significant, while the random errors were found to be high in the range between 0.23 mm and 0.31 mm. Given the higher intra-observer variabilities for the compressed/decompressed image series as compared to original images, and the fact that all inter-compression variabilities were found to be so high, we must conclude that the higher compression ratios affect the results of QCA in a negative sense. In conclusion, the use of lossy data compression with JPEG or LOT compression schemes at ratios 5, 8 and 12 must be discouraged for QCA.

Beneficial effect of enalapril on left ventricular remodelling in patients with a severe residual stenosis after acute anterior wall infarction

OBJECTIVE

The present study was designed to evaluate the effects of early angiotensin converting enzyme (ACE) inhibition on left ventricular enlargement in patients with anterior wall infarction following reperfusion therapy.

METHODS

Seventy-one consecutive patients with an anterior wall myocardial infarction were randomly allocated to enalapril (n = 36) or placebo (n = 35). All patients received either thrombolytic therapy (n = 46) or underwent primary coronary angioplasty (n = 25). Medication was started within 48 h admission to hospital and continued for 48 weeks. The process of left ventricular remodelling was assessed with two-dimensional echocardiography at 3 weeks and 1 year after the acute onset, and was related to the severity of the residual stenosis of the infarct-related artery.

RESULTS

Baseline left ventricular ejection fraction was 39.2% +/- 8.7%. During the study period left ventricular end-diastolic volume index increased from 48.2 +/- 9.9 ml.m-2 to 54.6 +/- 12.2 ml.m-2 at 3 weeks, and to 59.4 +/- 17.0 ml.m-2 after 1 year I control patients (P < 0.001). In the enalapril-treated patients, left ventricular end-diastolic volume index increased from 50.0 +/- 16.1 to 57.7 +/- 19.3 ml.m-2 at 3 weeks, and to 61.9 +/- 22.7 ml.m-2 after 1 year (P < 0.001). Both at 3 weeks and after 1 year, no overall differences in left ventricular volumes were observed between the enalapril and the placebo group (both ns). However, patients with a residual stenosis severity of > or = 70% in the infarct-related artery (n = 43) showed significant attenuation of remodelling by enalapril (n = 22) when compared to placebo (n = 21). In patients on enalapril, left ventricular end-diastolic volume index increased from 47.0 +/- 13.0 to 53.7 +/- 17.7 ml.m-2 compared to 48.0 +/- 9.6 to 60.3 +/- 16.3 ml.m-2 in control patients (P < 0.03). Also diastolic filling parameters were significantly improved in patients with > or = 70% residual stenosis.

CONCLUSION

In patients with an anterior wall infarction and a severe residual infarct-related coronary artery stenosis following reperfusion, treatment with enalapril prevents the process of left ventricular remodelling. As left ventricular dilatation is an early process we suggest that treatment with ACE inhibition should be started as soon as possible in this group of patients.

On-line automated border detection for echocardiographic quantification of right ventricular size and function in children

Rapid, accurate assessment of right ventricular (RV) size is important for the management of children with congenital heart disease. The usefulness of the Acoustic Quantification system of automated border detection (ABD) and on-line quantification (AQ) for assessment of RV size was tested in 36 children. AQ data were compared to "corrected AQ" measurements (after correction for cavity areas erroneously included in the region of interest) required for AQ. Furthermore, the influence of necessary changes to gain settings was tested in "lateral gain control" (LGC) images obtained by removal of ABD overlays. All results were compared to conventional echocardiography (echo), and agreement with magnetic resonance imaging (MRI) RV areas was assessed. Systematic differences (+/-) limits of agreement with MRI (transverse plane) for conventional echo and AQ (apical four-chamber view) were as follows: end-diastolic -0.8 +/- 3.8 (conventional echo) versus -1.7 +/- 4.6 (AQ) cm2/m2 (p < 0.001); end-systolic -1.3 +/- 3.2 versus -4.9 +/- 5.8 (AQ) cm2/m2 (p < 0.001); fractional area change 7.8 +/- 17.0% versus 26.9 +/- 31.4% (AQ) (p < 0.001). Differences between conventional echo, LGC, and corrected AQ areas were not statistically significant. The best agreement between MRI and echocardiography was with conventional echo. We conclude that automated border detection of the RV can be performed successfully with the AQ system at a fixed point in the cardiac cycle. For adequate assessment of RV function manual corrections of online AQ results are still required, which results in an important reduction of the time gain of on-line quantification.

Quantitative analysis of cardiovascular MR images

The diagnosis of cardiovascular disease requires the precise assessment of both morphology and function. Nearly all aspects of cardiovascular function and flow can be quantified nowadays with fast magnetic resonance (MR) imaging techniques. Conventional and breath-hold cine MR imaging allow the precise and highly reproducible assessment of global and regional left ventricular function. During the same examination, velocity encoded cine (VEC) MR imaging provides measurements of blood flow in the heart and great vessels. Quantitative image analysis often still relies on manual tracing of contours in the images. Reliable automated or semi-automated image analysis software would be very helpful to overcome the limitations associated with the manual and tedious processing of the images. Recent progress in MR imaging of the coronary arteries and myocardial perfusion imaging with contrast media, along with the further development of faster imaging sequences, suggest that MR imaging could evolve into a single technique ('one stop shop') for the evaluation of many aspects of heart disease. As a result, it is very likely that the need for automated image segmentation and analysis software algorithms will further increase. In this paper the developments directed towards the automated image analysis and semi-automated contour detection for cardiovascular MR imaging are presented.

Ischemic heart disease: value of MR techniques

BACKGROUND

The cardiovascular applications of magnetic resonance (MR) techniques in coronary artery disease have increased considerably in recent years. Technical advantages of MR imaging are the excellent spatial resolution, the characterization of myocardial tissue, and the potential for three-dimensional imaging. These characteristics allow the accurate assessment of left ventricular mass and volume, the differentiation of infarcted from normal tissue, and the determination of systolic wall thickening and regional wall motion abnormalities.

METHODS

In addition to the conventionally used spin-echo and cine-echo techniques, newer techniques such as myocardial tagging, ultrafast MR imaging and MR coronary angiography have been developed. These newer techniques allow a more accurate assessment of ventricular function (tagging), myocardial perfusion (ultrafast imaging), and evaluation of stenosis severity (MR coronary angiography). Particularly early detection and flow assessment of stenosed coronary arteries and bypasses by MR angiography would constitute a major breakthrough in cardiovascular MR imaging. Apart from the MR imaging techniques, cardiac metabolism may be well assessed using MR spectroscopy. This provides unique information on the metabolic behaviour of the myocardium under conditions stress-induced ischemia. However, the definite niche of cardiac MR spectroscopy has still to be settled.

CONCLUSION

Currently, MR techniques allow the evaluation of anatomy and function (accepted use), perfusion and viability (development phase), and coronary angiography (experimental phase). A particular strength of MR imaging is that one single MR test may encompass cardiac anatomy, perfusion, function, metabolism and coronary angiography. The replacement of multiple diagnostic tests with one MR test may have major effects on cardiovascular healthcare economics and would outweight the cost inherent to the MR angiography procedure.

New approach to quantitative angiographic assessment after stent implantation

The new generation quantitative angiographic systems apply the interpolated technique to calculate the reference diameter at the site of the stenosis by integrating measurements of the segments proximal and distal to the stenosis. After stent implantation these measurements can be misleading as the treated segment, which is frequently larger than the adjacent not stented segments, is included in the measurements. The consequence is an overestimation of the reference diameter and the residual diameter stenosis. The present study was performed to compare this conventional technique of measurement with a new method which excludes the stented segment for the calculation of the reference diameter. Fifty-two lesions treated with poorly radiopaque stents (56% Palmaz-Schatz, 28% NIR, 10% Gianturco-Roubin, 6% Wallstent) expanded at high pressure (> = or 16 atm) were analyzed according to the conventional and stent excluded method. After stent implantation the reference diameter was 3.39 +/- 0.48 mm with conventional measurements and 3.02 +/- 0.45 mm with the stent excluded method (P < 0.05). The corresponding % diameter stenosis was 13 +/- 9 for the conventional technique and 1 +/- 13 for the stent excluded analysis (P < 0.05). The new approach to quantitative coronary analysis after stenting provides higher accuracy in reference diameter calculations and allows a more appropriate matching of stented segments with adjacent normal segments.

Detection and quantification of dysfunctional myocardium by magnetic resonance imaging. A new three-dimensional method for quantitative wall-thickening analysis

BACKGROUND

Regional left ventricular dysfunction is a major consequence of myocardial ischemia, and its extent determines long-term prognosis. Accurate and reproducible analysis of left ventricular dysfunction is therefore useful for risk stratification and patient management.

METHODS AND RESULTS

Short-axis cardiac cine magnetic resonance (MR) imaging was performed in 25 patients after anterior myocardial infarction at 21 +/- 2.1 days after the acute onset. The MR images were analyzed with the use of a dedicated analytical software package (MASS version 1.0), which includes a modified centerline method and a new three-dimensional analysis approach. A database of 48 healthy volunteers was constructed to objectively depict myocardial dysfunction in the patients; this database was compared with enzymatically determined infarct size. The mean (+/-SEM) quantity of dysfunctional myocardium and enzymatically calculated infarct size equaled 24.0 +/- 3.0 and 22.3 +/- 2.9 g, respectively (P = .69). Enzymatically determined infarct size correlated strongly with left ventricular dysfunction determined by cine MR imaging (y = 0.90x + .92. P < .0001). Segments related to the distribution of the left anterior descending coronary artery showed a significantly lower percentage wall thickening in patients than did corresponding segments of 48 normal subjects (46.0 +/- 8.22% versus 87.1 +/- mean SEM, respectively; P < .001). The mean (+/-SEM) end diastolic wall thickness of the infarcted segment did not differ from that of corresponding normal segments (7.4 +/- 0.33 versus 7.5 +/- 0.15 mm; P = .75).

CONCLUSIONS

We conclude that the use of three-dimensional quantitative analysis of cine MR images accurately quantities the extent of regional left ventricular dysfunction in the infarcted heart. This method of analysis may be useful in assessing the effect of interventional therapies.

Angiotensin-converting enzyme inhibitor therapy affects left ventricular mass in patients with ejection fraction > 40% after acute myocardial infarction

OBJECTIVES

We tested the hypothesis that angiotensin-converting enzyme (ACE) inhibitor therapy decreases left ventricular (LV) mass in patients with a left ventricular ejection fraction (LVEF) > 40% and no evidence of heart failure after their first acute Q wave myocardial infarction (MI).

BACKGROUND

Recently, ACE inhibitor therapy has been shown to have an early mortality benefit in unselected patients with acute MI, including patients without heart failure and a LVEF > 35%. However, the effects on LV mass and volume in this patient population have not been studied.

METHODS

Thirty-five patients with a LVEF > 40% after their first acute Q wave MI were randomized to titrated oral ramipril (n = 20) or conventional therapy (control, n = 15). Magnetic resonance imaging (MRI) performed an average of 7 days and 3 months after MI provided LV volumes and mass from summated serial short-axis slices.

RESULTS

Left ventricular end-diastolic volume index did not change in ramipril-treated patients (62 +/- 16 [SD] to 66 +/- 17 ml/m2) or in control patients (62 +/- 16 to 68 +/- 17 ml/m2), and stroke volume index increased significantly in both groups. However, LV mass index decreased in ramipril-treated patients (82 +/- 18 to 73 +/- 19 g/m2, p = 0.0002) but not in the control patients (77 +/- 15 to 79 +/- 23 g/m2). Systolic arterial pressure did not change in either group at 3-month follow-up.

CONCLUSIONS

In patients with a LVEF > 40% after acute MI, ramipril decreased LV mass, and blood pressure and LV function were unchanged after 3 months of therapy. Whether the decrease in mass represents a sustained effect that is associated with a decrease in morbid events requires further investigation.

Reproducibility of left ventricular size, shape and mass with echocardiography, magnetic resonance imaging and radionuclide angiography in patients with anterior wall infarction. A plea for core laboratories

After myocardial infarction, left ventricular volume and ejection fraction can be assessed by echocardiography, magnetic resonance imaging and radionuclide angiography to guide therapy and determine prognosis. Whether a measured parameter gives the same results irrespective of the method used and the observer who performs the analysis is only partly known. Intra-observer and inter-observer variability were determined for echo and magnetic resonance imaging. Left ventricular ejection fraction measured by these techniques was related to radionuclide angiograms performed in the same period. Intra-observer variability for both echo and MRI was low and in most instances below 5%. Inter-observer variability for the echo and MRI measurements were substantially higher than intra-observer variability. Comparison of the three imaging modalities revealed systematic differences. Therefore, in clinical studies, left ventricular volume and function parameters have to be measured with the same technique and by the same observer in qualified core laboratories.

Assessment of the progression of emphysema by quantitative analysis of spirometrically gated computed tomography images

RATIONALE AND OBJECTIVES

The authors assessed the progression of pulmonary emphysema by means of quantitative analysis of computed tomography images.

METHODS

Twenty-three patients suffering from emphysema due to an alpha 1-antitrypsin deficiency, aged 45 +/- 7 years and exsmokers, were scanned twice with a 1-year time interval. At 90% of the vital lung capacity, slices with a thickness of 1.5 mm were acquired at the level of the carina and 5 cm above the carina; slices with a thickness of 1 cm were acquired 5 cm below the carina. The entire lung was scanned spirally at a respiratory status, corresponding with 75% of the total lung capacity at baseline. The mean lung densities (MLD) were calculated in an objective manner with new analytic software featuring automated detection of the lung contours.

RESULTS

Mean lung densities decreased by 14.2 +/- 12.0 Hounsfield units (HU; P < 0.001) above the carina, by 18.1 +/- 14.4 HU (P < 0.001) at the carina level, by 23.6 +/- 15.0 HU (P < 0.001) below the carina, and by 12.8 +/- 22.2 HU (P < 0.01) for the entire lung. The decrease in MLD was most obvious in the lower lung lobes. For the same patient group, the annual decrease in the forced expiratory volume (FEV1) and the carbon monoxide-diffusion were 120 +/- 190 mL (P < 0.01) and 10 +/- 70 mmol/kg/minute ( P < 0.2), respectively. No significant correlation was found between the decrease in MLD and the decrease in FEV1.

CONCLUSIONS

Progression of emphysema can be assessed in an objective manner based on the mean lung density (MLD), measured from computed tomography volume scans as well as from single-slice scans. Mean lung density has proved to be more sensitive than FEV1 and carbon monoxide-diffusion.

Validation of coronary artery saphenous vein bypass graft diameter measurements using quantitative angiography

The accepted value for reproducibility (true change) is two standard deviations (SD) of the differences between repeat measurements. It has been well established for coronary artery measurements using several different quantitative coronary angiography (QCA) systems, but it has not been well documented for saphenous vein grafts (SVG). The purpose of this study was to assess, using the Cardiovascular Measurement System (CMS), the measurement reproducibility of 24 vein grafts from 24 patients who had symptom-directed control angiography. Three equal graft segments were studied separately. Focal narrowings expressed in percent stenosis varied from 5 to 80% (mean 20.8 +/- 15.9%). The average minimum lumen diameter (MLD) was 3.07 +/- 0.81 mm and the average interpolated reference diameter (Ref. D) was 3.87 +/- 0.58 mm. We assessed the reproducibility of measurements obtained from two separate imagings of the graft in the same view but at least 20 minutes apart, near the beginning and at the end of the angiographic procedure (simulating baseline and end-trial examinations). The SD for differences in measurements (variability) was 0.183 mm for the MLD, 0.193 mm for the Ref.D, 0.184 mm for the mean diameter (Mean D) and 3.72% for the percent diameter stenosis (PDS). A reasonable true change cut-off for SVG measurements in our laboratory is > or = 0.4 mm for the minimum and mean lumen diameters, and > or = 10% for the PDS, when QCA is obtained with the QCA-CMS analytical software package.

Echo planar MRI of the heart on a standard system: validation of measurements of left ventricular function and mass

OBJECTIVE

Our goal was to validate cardiac measurements derived from multishot echo planar MRI (EPI) as compared with the well validated conventional GRE technique.

METHOD

Ten healthy subjects underwent breath-hold EPI and non-breath-hold GRE imaging in the short axis orientation of the left ventricle (LV) on a standard 1.5 T MR system. Ten section levels were obtained to encompass the entire LV. Measurements were obtained of end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), LV mass, time to end-systole (TES), and peak filling rate (PFR). Analysis of variance was performed to determine agreement between GRE- and EPI-derived measurements.

RESULTS

The acquisition time for EPI was much shorter than that for GRE (2.5 vs. 15 min). Both imaging techniques yielded good quality images allowing LV volumetrics. Agreement between GRE and EPI was best for measurements of EDV, SV, and LV mass; somewhat less agreement was found for ESV, EF, TES, and PFR. The intraobserver variability for measuring TES and PFR was higher for GRE than EPI (one sided F test; critical values at p = 0.05 were > 3.18).

CONCLUSION

Multishot EPI of the heart provides accurate measurements of LV function and mass in a time-efficient manner.

The Asp9 Asn mutation in the lipoprotein lipase gene is associated with increased progression of coronary atherosclerosis. REGRESS Study Group, Interuniversity Cardiology Institute, Utrecht, The Netherlands. Regression Growth Evaluation Statin Study

BACKGROUND

Many patients suffering from premature coronary artery disease report a family history for such events. A mutation in a particular gene, which confers susceptibility for atherosclerosis, will be found more frequently in individuals suffering from coronary atherosclerosis than in the general population. We have recently reported the identification of an Asp9 Asn substitution in the lipoprotein lipase (LPL) enzyme. We analyzed the impact of this mutation on the progression of coronary atherosclerosis and the effect of pravastatin in both carriers and noncarriers.

METHODS AND RESULTS

All patients were enrolled in the quantitative coronary angiographic clinical trial REGRESS, which studied the impact of pravastatin therapy on coronary atherosclerosis. The Asp9 Asn mutation was identified in 38 of 819 (4.8%) patients. Carriers of the mutation more often had a positive family history of cardiovascular disease and lower HDL cholesterol levels than noncarriers. In the placebo group, carriers showed more progression of coronary atherosclerosis than noncarriers: mean reduction of the minimum obstruction diameter of -0.25 mm versus -0.12 mm (P = .029) and increase of percentage diameter stenosis of 6.4% versus 1.4% (P = .004). Moreover, the adjusted relative risk for a clinical event for carriers was calculated at 2.16 (95% CI, 1.09 to 4.29; P = .027). Although the lipid-lowering effect of pravastatin was attenuated in carriers, it appeared that these patients showed a response similar to noncarriers in terms of less progression of atherosclerosis and event-free survival.

CONCLUSIONS

This study shows that heterozygosity for a mutation in the LPL gene, which causes only subtle changes in fasting plasma lipids, may promote the progression of coronary atherosclerosis and diminish clinical event-free survival.

Comparisons of angiographic core laboratory analyses of phantom and clinical images: interlaboratory variability

Centralized, quantitative coronary analysis (QCA) has become the standard for determining change in coronary anatomy in clinical investigations. QCA systems and laboratory methods, however, vary among core facilities, and analysis variability among angiographic core laboratories (ACL) has not be studied. We evaluated QCA accuracy and variability among active ACL, using differing QCA systems by comparing analyses of phantom and clinical cinefilm images. Automated, unedited analyses were performed on images of 11 plexiglass phantom lumens (0.67-5.05 mm) acquired under varying radiographic conditions. Analysis differences from actual luminal diameters ranged widely (+0.42 - (-)0.45 mm) among ACL. Measurement of diameters < 1.0 mm were overestimated and diameters > 3.0 mm were underestimated. Measurements of midrange diameters (> 1.0 mm and < 3.0 mm) were most comparable among ACL (93% within +/- 0.2 mm). Clinical image analysis was performed using differing QCA systems and laboratory methodology on 11 randomly selected study films. Comparative analyses revealed significant variability between laboratories in the assessment of minimal lumen diameter (0.22 +/- 0.38 mm P < 0.05). These data describe analysis variability among ACL and demonstrate a need for establishing ACL performance standards.

The influence of angiographic endpoints on the outcome of lipid intervention studies. A proposal for standardization. REGRESS study group

The aims of this study were to evaluate the influence of different coronary angiographic endpoints on the outcome of lipid intervention studies and to formulate a proposal for angiographic endpoint standardization. In recent angiographic intervention studies a confusing diversity in angiographic endpoints has been used to determine the outcome. In addition, differences in study populations (eg, bypass patients included or not) could influence results. This makes comparisons between studies cumbersome and raises the question to what extent the results of various studies may be subject to the selection of angiographic endpoints. The investigators compared three frequently used endpoints (mean segment diameter, minimum obstruction diameter, and % stenosis) in a group of 505 patients who had just finished a trial designed to assess the effect of cholesterol lowering by pravastatin. To exclude a potential bias this analysis was carried out at the time that the study was still blinded. They found poor intercorrelation coefficients for mean segment diameter calculated in different ways, ranging from 0.55 to 0.95, dependent on inclusion or exclusion of segments influenced by coronary angioplasty or bypass grafting and on whether or not a value of 0 was assumed for occluded segments and segments distal to occlusions. The correlation between mean segment diameter and minimum obstruction diameter was 0.79; between minimum obstruction diamete and % stenosis, 0.85; and between mean segment diameter and % stenosis, only 0.64. Different endpoints sometimes correlate poorly. This may lead to differences in results of angiographic intervention trials. The authors propose standardization by (1) using both mean sement diameter and minimum obstruction diameter as endpoints and (2) excluding from the primary analysis segments influenced by mechanical interventions.

Regional myocardial shape alterations in patients with anterior myocardial infarction

OBJECTIVE

To assess the impact of regional left ventricular curvature in patients with an acute anterior myocardial infarction on ventricular volume.

METHODS

Left ventricular curvature was calculated at 100 points from apical four chamber echocardiograms of 68 patients with an acute anterior wall infarction. Curvature at any point of the contour was defined as the reciprocal of the radius of the circle that intersects that point tangentially and was independent of volume and geometric assumptions. Curvature, volume and shape of the patient group was compared with these measurements in 20 normal volunteers.

RESULTS

Diastolic curvature differed at the borderzone of the infarct and the apical area. In the basal septal area (point 9-18) mean curvature was lower in the patient group (0.1 +/- 2.7 versus 2.1 +/- 0.7; p < 0.0001) as compared to the normal individuals. In the mid-septal area (point 22 to 27), mean curvature was more concave (-0.1 +/- 2.6) in the patient group corresponding to in the normal population (-0.4 +/- 1.3) p < 0.005. In the apex point 52 and 53 diverged with a curvature of 9.9 +/- 1.9 in patients versus 9.4 +/- 2.9 p < 0.005 in normal individuals. Systolic curvature diverged at the basal septum (point 1-4) with a mean curvature of 1.4 +/- 1.1 in patients compared to 3.5 +/- 2.5 in normal individuals p < 0.01. Curvature differed also in the mid-septal region (point 9-29) with a curvature of -1.7 +/- 1.2 in patients versus 0.4 +/- 0.9 (p < 0.01) in normal individuals and in the apical septum (point 48-52) with a curvature of 16.6 +/- 5.2 in patients and 13.9 +/- 2.6 (p < 0.0001) in healthy individuals Separation of patients with the greatest curvature alteration to those with minor curvature change revealed, that baseline curvature analysis can discriminate patients at risk for left ventricular remodelling.

CONCLUSION

Regional curvature analysis correctly identifies the geometric changes induced by myocardial infarction. Apical systolic curvature can distinguish those patients that are at risk for left ventricular remodelling from those who are not at risk.

Micro stent, quantitative coronary angiography, and procedural results

The Micro stent (MS) is a radiopaque stainless steel balloon expandable intracoronary stent. The stent is mounted on a rapid-exchange delivery system. From August 1994-March 1995, 127 MS were implanted in 85 patients (pts, 1.5 stents/pt, 85 in native vessels and 42 in bypass vein grafts, 61 males and 24 female, age 33-77 yr, mean age 61 +/- 10 yr). Pts studied were scheduled for either elective PTCA (n = 62, 73%) or PTCA for acute myocardial infarction (n = 23, 27%). Elective stent implantation was performed in 45 pts (53%). An MS was implanted because of a suboptimal balloon angioplasty result in 26 pts (31%). The stent was implanted because of threatened or acute vessel closure after balloon angioplasty in 14 pts (16%). During the procedure, 500 mg aspirin and 2 x 7,500 units of heparin were administered intravenously, followed by systemic heparinization for 48 hr. Pts were discharged with 100 mg aspirin daily (n = 50, 59%), or anticoagulant drugs and 100 mg aspirin daily (n = 19, 22%), or anticoagulant drugs only (n = 16, 19%). Angiographic results were analyzed with computer-assisted quantitative coronary arteriography. Angiographic success (defined as a residual stenosis of < 30%) was achieved in 124 of 127 attempts (98%). The mean minimal luminal diameter of the target lesions increased from 0.88 +/- 0.79 mm before stent implantation to 3.08 +/- 0.56 mm (P < 0.001). The percentage of diameter stenosis was reduced from 77.9 +/- 20.9% before to 13.3 +/- 10.5% (P < 0.001) after stent implantation. The average initial gain was 2.53 +/- 1.37 mm. The procedural success rate (defined as a residual stenosis of < 30% without occurrence of major clinical events within 3 wk after procedure) was 84%. Major clinical events included: death 1 pt (1%); cerebrovascular accident, 1 pt (1%); subacute stent closure, 5 pts (6%); coronary artery bypass grafting, 3 pts (4%); false femoral aneurysm, 2 pts (2%). The initial results of Micro stent implantation are promising. No anticoagulant therapy was given to most of the patients (59%). Few vascular and bleeding complications were observed. However, at this stage, no data about the restenosis rate after implantation of a Micro stent are available.

Left ventricular regression equations from single plane cine and digital X-ray ventriculograms revisited

For the assessment of left ventricular volume from X-ray ventriculograms, widely known regression equations are used to correct for the irregular shape of the left ventricular lumen and the presence of the papillary muscles and trabeculations. These regression equations were derived in the late nineteen sixties and seventies. With all the changes in X-ray technology that have taken place over the past 20-30 years, the question was raised whether these regression equations were still valid. Therefore, 23 left ventricular casts of known volume were imaged in RAO20, RAO30 and RAO40 angiographic views and recorded on 35 mm cinefilm as well as in digital format. All the frames were traced manually by two observers and the volumes calculated by the Area Length and Simpson Rule approaches. The following conclusions could be drawn: inter- and intra-observer variations were small (systematic differences < 1.5 ml; random differences < 2.9 ml) and statistically not significant; the regression equations are virtually the same for the RAO20, RAO30 and RAO40 views under the different circumstances; the Area Length method was associated with slightly smaller values for the standard-error-of-the-estimate (SEE) suggesting a slight preference for this approach versus the Simpson Rule; significant differences were found between the cinefilm and digital regression equations; and the following new regression equations are proposed, which indeed differ significantly from the earliest proposals and less from the monoplane formulas proposed by Kennedy & Lange in the 1970s: [table: see text]

LDL-Apheresis Atherosclerosis Regression Study (LAARS). Effect of aggressive versus conventional lipid lowering treatment on coronary atherosclerosis

BACKGROUND

Intensive lipid lowering may retard the progression of coronary atherosclerosis. LDL-apheresis has the potential to decrease LDL cholesterol to very low levels. To assess the effect of more aggressive lipid lowering with LDL-apheresis, we set up a randomized study in men with hypercholesterolemia and severe coronary atherosclerosis.

METHODS AND RESULTS

For 2 years, 42 men were treated with either biweekly LDL-apheresis plus medication or medication alone. In both groups a dose of simvistatin of 40 mg per day was administered. Baseline (mean+/-SD) LDL cholesterol was 7.8+/-1.9 mmol x L(-1) and 7.9+/-2.3 mmol x L(-1) in the apheresis and medication groups, respectively. The mean reduction in LDL cholesterol was 63% (to 3.0 mmol x L(-1)) and 47% (to 4.1 mmol x L(-1)), respectively. Primary quantitative coronary angiographic end points were changes in average mean segment diameter and minimal obstruction diameter. No differences between the apheresis and medication groups were found in mean segment diameter (-0.01+/-0.16 mm versus 0.03+/-0.16 mm, respectively) or in minimal obstruction diameter (0.01+/-0.13 mm versus 0.01+/-0.11 mm, respectively), expressed as means per patient. On the basis of coronary segment, mean percent stenosis of all lesions showed a tendency to decrease; only in the apheresis group more minor lesions disappeared in comparison to the medication group. On bicycle exercise tests, the time to 0.1 mV ST-segment depression increased significantly by 39% and the maximum level of ST depression decreased significantly by 0.07 mV in the apheresis group versus no changes in the medication group.

CONCLUSIONS

Two years of lipid lowering both with medication alone or LDL-apheresis with medication showed angiographic arrest of the progression of coronary artery disease. However, more aggressive treatment induced functional improvement, which may precede anatomic changes.

Evidence for a synergistic effect of calcium channel blockers with lipid-lowering therapy in retarding progression of coronary atherosclerosis in symptomatic patients with normal to moderately raised cholesterol levels. The REGRESS Study Group

To date, lipid-lowering therapy appears to be the most effective medical intervention to retard progression of coronary atherosclerosis. In spite of promising experimental results, clinical trials completed so far have failed to demonstrate that calcium channel blockers (CCBs) alone influence the evolution of established coronary atherosclerosis. To assess whether the two therapies may have an additive or synergistic beneficial effect on human atherosclerosis, we reviewed in this regard the data of the angiographic Regression Growth Evaluation Statin Study (REGRESS) trial. REGRESS was designed to determine the effect of lipid-lowering therapy with pravastatin in symptomatic patients with normal to moderately raised cholesterol levels. Angiographically, with respect to the minimum obstruction diameter, in the pravastatin group, patients had on average 0.05 mm (95% confidence interval [CI]: 0.01-0.09) less progression if cotreated with CCBs compared with no CCB treatment, whereas in the placebo (no pravastatin) group, no effect of CCB treatment was observed (interaction test for differential effect of CCB treatment in patients with pravastatin compared with patients receiving placebo: P=.0016). With respect to the mean segment diameter, similar although not significant (P=.33) results were found. With respect to new lesion formation, in the pravastatin group, there were 50% (CI: 25-83) fewer patients with new angiographic lesions if cotreated with CCBs compared with no CCB cotreatment, whereas in the placebo (no pravastatin) group, no significant effect of CCB treatment was observed (interaction test: P=.0026). No beneficial effects of CCB treatment on clinical events were observed. Although the REGRESS trial was not designed to evaluate combination therapy, the results suggest strongly that addition of CCBs to 3-hydroxy-3-methyl-glutaryl-coenzyme reductase inhibitor therapy (pravastatin) acts synergistically in retarding the progression of established coronary atherosclerosis.