American College of Cardiology/European Society of Cardiology International Study of Angiographic Data Compression Phase I: The effect of lossy data compression on recognition of diagnostic features in digital coronary angiography.

OBJECTIVES: This study intended to determine the effect of varying degrees of lossy Joint Photographic Experts Group (JPEG) compression on detection of coronary angiographic features. BACKGROUND: Compression of digital coronary angiograms facilitates playback of images and decreases cost. There are little data on the effect of compression on the accuracy of coronary angiography. METHODS: At six centers, 71 angiographers each reviewed a set of 100 angiographic sequences. The 100 sequences were divided into four, 25-sequence subsets. Each subset of 25 was displayed either as original images or at one of three compression ratios (CRs) (6:1, 10:1 or 16:1). The effect of lossy compression on the sensitivity and specificity for detection of diagnostic features was determined. The effect of compression on subjective measures of image quality graded by the angiographers was also examined. RESULTS: Lossy compression at a ratio of 16:1 decreased the sensitivity for the detection of diagnostic features (76% vs. 80% p = 0.004). The largest effect was in the detection of calcification (52% vs. 63% at 16:1 compression vs. original images, p < 0.001). Subjective indicators of image quality indicated a reduction in confidence in interpretation at CRs of 10:1 and 16:1. CONCLUSIONS: With increased ratios of lossy compression, a degradation of digital coronary angiograms occurs that results in decreased diagnostic accuracy. The sensitivity for detection of common diagnostic features was decreased, and subjective assessment of image quality was impaired. Caution is warranted in the interpretation of coronary angiograms that have been subjected to lossy JPEG compression beyond a ratio of 6:1.

Coronary flow velocity response to adenosine characterizes coronary microvascular function in women with chest pain and no obstructive coronary disease. Results from the pilot phase of the Women's Ischemia Syndrome Evaluation (WISE) study.

OBJECTIVES: We sought to develop and validate a definition of coronary microvascular dysfunction in women with chest pain and no significant epicardial obstruction based on adenosine-induced changes in coronary flow velocity (i.e., coronary velocity reserve). BACKGROUND: Chest pain is frequently not caused by fixed obstructive coronary artery disease (CAD) of large vessels in women. Coronary microvascular dysfunction is an alternative mechanism of chest pain that is more prevalent in women and is associated with attenuated coronary volumetric flow augmentation in response to hyperemic stimuli (i.e., abnormal coronary flow reserve). However, traditional assessment of coronary volumetric flow reserve is time-consuming and not uniformly available. METHODS: As part of the Women's Ischemia Syndrome Evaluation (WISE) study, 48 women with chest pain and normal coronary arteries or minimal coronary luminal irregularities (mean stenosis = 7%) underwent assessment of coronary blood flow reserve and coronary flow velocity reserve. Blood flow responses to intracoronary adenosine were measured using intracoronary Doppler ultrasonography and quantitative angiography. RESULTS: Coronary volumetric flow reserve correlated with coronary velocity reserve (Pearson correlation = 0.87, p < 0.001). In 29 (60%) women with abnormal coronary microcirculation (mean coronary flow reserve = 1.84), adenosine increased coronary velocity by 89% (p < 0.001) but did not change coronary cross-sectional area. In 19 (40%) women with normal microcirculation (mean flow reserve = 3.24), adenosine increased coronary velocity and area by 179% (p < 0.001) and 17% (p < 0.001), respectively. A coronary velocity reserve threshold of 2.24 provided the best balance between sensitivity and specificity (90% and 89%, respectively) for the diagnosis of microvascular dysfunction. In addition, failure of the epicardial coronary to dilate at least 9% was found to be a sensitive (79%) and specific (79%) surrogate marker of microvascular dysfunction. CONCLUSIONS: Coronary flow velocity response to intracoronary adenosine characterizes coronary microvascular function in women with chest pain in the absence of obstructive CAD. Attenuated epicardial coronary dilation response to adenosine may be a surrogate marker of microvascular dysfunction in women with chest pain and no obstructive CAD.

Differential antagonism of cardiac actions of adenosine by theophylline.

OBJECTIVE: To determine the relative sensitivity of cardiac A1- and A2-adenosine receptor-mediated effects to antagonism by theophylline in man. METHODS: Baseline measurements of the A-H interval (A1-adenosine receptor-mediated effect) and coronary blood flow (A2-adenosine receptor-mediated effect) were made in 10 patients with angiographically normal coronary arteries. Adenosine was then administered as a continuous intravenous infusion followed by a rapid intravenous bolus, and measurements repeated. Theophylline (5 mg/kg i.v.) was then administered, and the adenosine infusion repeated. To corroborate the results found in man, the cardiac A1- and A2-adenosine receptor-mediated effects were measured in guinea pig isolated hearts exposed to increasing concentrations of adenosine, in the absence and presence of theophylline (60 microM). RESULTS: Compared to baseline, adenosine infusion and bolus caused significant prolongation of the A-H interval (109 +/- 41 vs. 116 +/- 44 vs. 168 +/- 57 ms, respectively), and increase in coronary blood flow (46 +/- 37 vs. 86 +/- 71 vs. 172 +/- 98 ml/min, respectively). Theophylline abolished the prolongation of the A-H interval during adenosine infusion and bolus (99 +/- 36 and 107 +/- 44 ms, respectively), yet had minimal effect on the increase in coronary blood flow (63 +/- 51 and 136 +/- 121 ml/min, respectively). In guinea pig isolated hearts, theophylline was shown to significantly antagonize the A2-adenosine receptor-mediated effects only when the concentrations of adenosine were < or = 1.0 microM. CONCLUSIONS: In man, theophylline completely antagonizes the A1-adenosine receptor-mediated prolongation of the A-H interval, but has minimal effect on the A2-receptor-mediated coronary vasodilation, particularly when adenosine concentrations exceed 1.0 microM.

Decrease in hematocrit after coronary stent placement and dextran therapy.

In summary, dextran 40, when given after coronary stent placement, results in a marked decrease in hematocrit within 24 hours. Hematocrit often returns to near baseline levels within 48 hours of stopping dextran. This phenomenon most likely reflects dextran-related hemodilution. This hemodilutional decrease in hematocrit is often misinterpreted as acute blood loss and may result in blood transfusion in patients with low baseline hematocrit. However, far less aggressive anticoagulation regimens, which do not include dextran, are under investigation in patients undergoing coronary stent placement.

Effect of alteration in loading conditions on both normal and abnormal patterns of left ventricular filling in healthy individuals.

Doppler analysis of mitral flow provides a means of analyzing left ventricular (LV) diastolic function. While experimental studies have suggested that changes in left atrial pressure may affect the normal pattern of early diastolic filling, the effect of such changes on abnormal patterns of filling is unknown. Accordingly, the Doppler pattern of LV filling was analyzed in 20 subjects with LV hypertrophy (mean age 59 +/- 13 years, +/- standard deviation), in 25 healthy normal subjects (29 +/- 6 years) and in 11 elderly subjects (68 +/- 5 years). All underwent Doppler examination of LV inflow at rest and immediately after postural changes. In all 3 groups, head-down positioning increased early diastolic flow velocity (E) (p less than 0.001), and raised the E to late diastolic flow velocity (A) ratio (p less than 0.01). However, an abnormal E/A ratio never approached a normal resting value. Likewise, although E and the E/A ratio decreased significantly in normal subjects with head-up positioning, it did not become abnormal. The magnitude of change in E, A and E/A ratio did not differ among the 3 groups in response to postural changes. Thus, alterations of LV loading conditions alter the pattern of LV filling, whether normal or abnormal at baseline. The magnitude of change appears to be independent of the resting flow pattern. Although loading conditions may affect the Doppler pattern of filling, simple changes in venous return do not "normalize" an abnormal pattern, nor do they "abnormalize" a normal pattern.

Effect of theophylline on the warm-up phenomenon.

This study examined whether the adenosine receptor antagonist theophylline prevents the warm-up phenomenon in patients with stable angina undergoing serial exercise tests. Our findings offer evidence that adenosine does not play a role in the warm-up phenomenon, and indirectly suggest that the warm-up phenomenon does not represent ischemic preconditioning in humans.

Detailed angiographic analysis of women with suspected ischemic chest pain (pilot phase data from the NHLBI-sponsored Women's Ischemia Syndrome Evaluation [WISE] Study Angiographic Core Laboratory).

The purpose of this study is to provide a contemporary qualitative and quantitative analysis of coronary angiograms from a large series of women enrolled in the Women's Ischemia Syndrome Evaluation (WISE) study who had suspected ischemic chest pain. Previous studies have suggested that women with chest pain have a lower prevalence of significant coronary artery disease (CAD) compared with men. Detailed analyses of angiographic findings relative to risk factors and outcomes are not available. All coronary angiograms were reviewed in a central core laboratory. Quantitative measurement of percent stenosis was used to assess the presence and severity of disease. Of the 323 women enrolled in the pilot phase, 34% had no detectable, 23% had measurable but minimal, and 43% had significant ( > 50% diameter stenosis) CAD. Of those with significant CAD, most had multivessel disease. Features suggesting complex plaque were identified in < 10%. Age, hypertension, diabetes mellitus, prior myocardial infarction (MI), current hormone replacement therapy, and unstable angina were all significant, independent predictors of presence of significant disease (p < 0.05). Subsequent hospitalization for a cardiac cause occurred more frequently in those women with minimal and significant disease compared with no disease (p = 0.001). The common findings of no and extensive CAD among symptomatic women at coronary angiography highlight the need for better clinical noninvasive evaluations for ischemia. Women with minimal CAD have intermediate rates of rehospitalization and cardiovascular events, and thus should not be considered low risk.

Myocardial infarction related atrial fibrillation: role of endogenous adenosine.

Exogenous administration of adenosine induces atrial fibrillation in up to 7.0% of patients. Animal studies affirm endogenous adenosine released in response to tissue hypoxia may play a mechanistic role in arrhythmias associated with myocardial ischaemia or hypoxia. Therefore, atrial fibrillation occurring early after the acute phase of myocardial infarction involving atrial tissue may be secondary to an excessive accumulation of adenosine that leads to a shortening of atrial refractory period. Early in the course of acute inferior myocardial infarction, two patients (males aged 45 and 68) suffered new onset sustained atrial fibrillation that was abrupt in onset and complicated their clinical management. They were administered 250 mg theophylline as a slow intravenous injection at a rate of 100 mg/min or until conversion to normal sinus rhythm occurred. Both patients converted to normal sinus rhythm within five minutes of the administration of theophylline. In up to 52 hours of continuous ECG monitoring after the theophylline administration the atrial fibrillation did not recur. Neither patient experienced any adverse outcome from theophylline administration. These observations are the first reported in humans or laboratory animals to suggest that atrial fibrillation, presumably due to elevated interstitial atrial concentration of adenosine caused by myocardial ischaemia, can be terminated with an adenosine receptor antagonist. However, the hypothesis that excessive accumulation of endogenous adenosine in atrial tissue may induce atrial fibrillation is well substantiated by other investigators. Thus, A1 adenosine receptor antagonists may prove to be valuable in the management of ischaemia related atrial fibrillation.

Antegrade filling of an occluded right coronary artery via collaterals from a separate conus artery, a previously undescribed collateral pathway.

The conus artery is known to be a frequent supplier of collaterals to the LAD and distal marginal branches of the RCA. In this report we describe a patient with an ostial RCA occlusion who was found to have, during selective conus artery injection, excellent collaterals directly to the proximal RCA. This anatomy was initially mistaken for diffuse disease of the ostium and proximal portion of the RCA.

Worse six-month outcome for patients with multiple stents in a single coronary artery.

BACKGROUND: Before the "era" of optimal stent deployment, very few data concerning multiple stents in a single coronary artery showed restenosis rates up to 60%. OBJECTIVE: To evaluate the 6-month outcome of patients receiving multiple Palmaz-Schatz stents (> or =2 stents) in a single coronary artery compared to those receiving single stents. METHODS: Three hundred and forty-eight patients having multiple stents were compared to 174 patients receiving single stents during a 6-month follow-up. RESULTS: Repeat target lesion revascularization (RTLR), either repeat PTCA or CABG, was 10.4% in the single-stent group, 22.6% in the two-stent group, and 23.1% in the > or =2 stent group (p = 0.001, single versus 2 or > or =2 stents). There was not a significant difference between single stent and multiple stent groups in myocardial infarction and death during 6-month follow-up. Multivariate analysis showed multiple stents, diabetes mellitus, and type C lesion to be predictors of RTLR. CONCLUSIONS: Placement of two or more stents was associated with a significantly higher RTLR compared with single stent placement. The optimal approach to diffuse coronary artery disease remains to be defined.

Ischemic preconditioning: clinical relevance and investigative studies.

Experimental animal studies have shown that repetitive brief coronary occlusions render the heart resistant to myocardial infarction from subsequent, more prolonged, coronary occlusions. This phenomenon in animal models has been called ischemic preconditioning. In a number of clinical scenarios, the second in a series of ischemic episodes appears to be less severe than the first, suggesting that ischemic preconditioning also occurs in humans. If the mediator of preconditioning could be identified, it is conceivable that this agent could be administered to patients with coronary artery disease as a myocardial protectant. However, the definite clinical relevance of this interesting experimental finding remains unknown. Unlike the case in animal models subjected to an abrupt occlusion, preconditioning is difficult to study in the clinical setting. This article reviews the findings and limitations of the relevant clinical studies looking for ischemic preconditioning in humans.

Echocardiographic assessment of wall motion in ST-segment alternans during coronary angioplasty.

ST alternans occurs in the setting of severe and extensive myocardial ischemia. In this particular case, ST alternans occurred well after the onset of ischemia-induced left ventricular dysfunction. There is no echocardiographic evidence of beat-to-beat variation in contractility to correspond to this ST-segment phenomenon. Further studies of left ventricular function during ST alternans in patients are needed to determine whether this finding applies to all patients with ischemic heart disease.

The effects of intracoronary adenosine on preconditioning during coronary angioplasty.

There is evidence that the first balloon inflation during coronary angioplasty provides a preconditioning stimulus leading to decreased ischemia during subsequent balloon inflations. Endogenous adenosine release may play a role in ischemic preconditioning. Therefore, intracoronary adenosine administration prior to the first balloon inflation during percutaneous transluminal coronary angioplasty (PTCA) might modify the preconditioning response to the first balloon inflation. Forty-one patients underwent double-blind randomization to treatment with 100 mcg of intracoronary adenosine or placebo prior to coronary angioplasty. Twenty patients (11 adenosine, 9 placebo) had complete resolution of ischemia between inflations allowing comparison between the first and second inflation. An angioplasty guidewire was used to obtain an intracoronary electrocardiogram. The mean reduction in ST elevation during the second inflation compared with the first was 4.8 mm in the placebo group and -0.8 in the adenosine group (p < 0.05 placebo vs. adenosine). Seven of 9 placebo patients had a decrease in ischemia during the second inflation compared with the first, while only 2 of 11 adenosine patients showed a reduction. It was concluded that (1) the first inflation during PTCA is a preconditioning stimulus leading to a decrease in ischemia during later inflations, and (2) intracoronary adenosine administration prior to PTCA modifies the preconditioning effect of the first inflation. These data suggest that adenosine plays a role in ischemic preconditioning in humans.

Venous activated clotting time after intra-arterial heparin: effect of site of administration and timing of sampling.

It is not known how the site of arterial administration of heparin and the timing of the activated clotting time (ACT) measurement affect the ACT during coronary interventions. We measured serial femoral venous ACTs after heparin was administered either via the angioplasty guiding catheter into the central aorta or peripherally via a sheath into the femoral artery. When heparin was administered into the central aorta, the ACT rose gradually and by 60 sec plateaued without further increase. When heparin was given into the femoral artery, the ACT displayed a marked "overshoot" early (20-270 sec after heparin) and did not plateau until sometime between 270 and 800 sec after heparin administration. We conclude that the site of administration and timing of venous sampling markedly affect the measured ACT during coronary interventions. Operators should be aware of these effects when assessing the accuracy of the ACT during coronary interventions.

Lysis of intravascular thrombus prior to coronary stenting using the dispatch infusion catheter.

The presence of angiographic evidence of thrombus is generally thought to be a contraindication to coronary stent placement. This report describes four patients in whom angiographic thrombus was lysed using the Dispatch infusion catheter prior to coronary stenting. Urokinase was infused via the Dispatch catheter with resolution of angiographic evidence of thrombus in all cases. No complications were encountered using this technique, and all patients had excellent angiographic results after stenting. We conclude that lysis of intracoronary thrombus using the Dispatch infusion catheter is feasible and appears safe in this small study. Further trials are needed to determine if this technique reduces the acute stent thrombosis rate compared to other techniques for stent deployment in the presence of angiographic evidence of thrombus.

Selective attenuation by N-0861 (N6-endonorboran-2-yl-9-methyladenine) of cardiac A1 adenosine receptor-mediated effects in humans.

BACKGROUND: To determine the adenosine receptor subtype selectivity of the novel antagonist N-0861, the A1 and A2 receptor-mediated cardiac effects of adenosine were investigated in 13 patients during continuous intravenous infusion and boluses of adenosine before and after intravenous infusion of N-0861. METHODS AND RESULTS: Measurements of the the atria-to-His (A-H) interval, chest pain severity, and coronary blood flow velocity were made before and after low-dose (69 microg x kg(-1) x min(-1)) intravenous infusion and bolus (2.5 mg) adenosine. Two doses of N-0861 were infused intravenously, and the adenosine protocol was repeated. N-0861 0.25 mg/kg abolished the negative dromotropic effect (A-H interval prolongation) and chest discomfort experienced during infusion of adenosine and attenuated discomfort observed during the boluses of adenosine; however, the increase in coronary blood flow velocity was not significantly affected. CONCLUSIONS: These actions of N-0861 support the concept that the negative dromotropic effect and anginalike pain caused by adenosine are A1 adenosine receptor-mediated, whereas the increase in coronary blood flow velocity is due to activation of A2 adenosine receptors. N-0861 appears to be an effective and selective A1 adenosine receptor antagonist in humans.

Constrictor and dilator responses to intracoronary acetylcholine in adjacent segments of the same coronary artery in patients with coronary artery disease. Endothelial function revisited.

BACKGROUND: In patients with angiographically detectable atherosclerosis or in those with risk factors for coronary artery disease, intracoronary acetylcholine causes coronary constriction instead of endothelium-derived relaxing factor-mediated dilation. Therefore, it has been hypothesized that diffuse endothelial dysfunction precedes development of coronary atherosclerosis. We tested this hypothesis in a systematic investigation of the effects of ascending doses of acetylcholine on the diameters of nonstenotic segments of the left coronary artery in patients with advanced atherosclerosis and coronary risk factors. METHODS AND RESULTS: Effects of intracoronary infusion of acetylcholine (10(-6) to 10(-4) mol/L) on diameters of proximal, middle, and distal nonstenotic segments of the left coronary artery were studied in 28 consecutive patients with chronic stable angina, positive exercise tests, and angiographic evidence of obstructive atherosclerosis (> or = 50% reduction in lumen diameter in at least one vessel). Two patterns of response to the maximal acetylcholine dose (10(-4) mol/L) were observed. In 21 patients (group 1), only constriction was observed in all left anterior descending and circumflex artery segments studied (16 +/- 3%, 19 +/- 4%, and 23 +/- 4%, respectively; P < .01 compared with control). In 7 other patients (group 2), both constriction and dilation were observed in adjacent segments of the same vessel; maximal acetylcholine dose caused constriction in 14 left anterior descending artery segments from a control diameter of 1.94 +/- 0.19 to 1.33 +/- 0.26 mm (37% reduction, P < .01) and dilation in 16 other segments from 1.63 +/- 0.22 to 1.93 +/- 0.21 mm (25% increase, P < .01). In the circumflex artery, this dose caused constriction in 16 segments from a control diameter of 1.88 +/- 0.14 to 1.33 +/- 0.17 mm (31% reduction, P < .01) and dilation in 12 segments from 1.37 +/- 0.12 to 1.71 +/- 0.09 mm (34% increase, P < .01). CONCLUSIONS: In 25% of patients studied with advanced angiographic coronary atherosclerosis and coronary risk factors, coronary segments with acetylcholine-inducible dilatation are present. In these patients, the endothelium is not diffusely dysfunctional as currently believed but rather shows marked segmental heterogeneity in the response to acetylcholine reflecting degrees of endothelial dysfunction.

American College of Cardiology/ European Society of Cardiology international study of angiographic data compression phase I. The effects of lossy data compression on recognition of diagnostic features in digital coronary angiography.

OBJECTIVES: This study intended to determine the effect of varying degrees of lossy Joint Photographic Experts Group (JPEG) compression on detection of coronary angiographic features. Background Compression of digital coronary angiograms facilitates playback of images and decreases cost. There are little data on the effect of compression on the accuracy of coronary angiography. METHODS: At six centers, 71 angiographers each reviewed a set of 100 angiographic sequences. The 100 sequences were divided into four, 25-sequence subsets. Each subset of 25 was displayed either as original images or at one of three compression ratios (CRs) (6:1, 10:1 or 16:1). The effect of lossy compression on the sensitivity and specificity for detection of diagnostic features was determined. The effect of compression on subjective measures of image quality graded by the angiographers was also examined. RESULTS: Lossy compression at a ratio of 16:1 decreased the sensitivity for the detection of diagnostic features (76% vs. 80%P=0.004). The largest effect was in the detection of calcification (52% vs. 63% at 16:1 compression vs. original images, P<0.001). Subjective indicators of image quality indicated a reduction in confidence in interpretation at CRs of 10:1 and 16:1. CONCLUSIONS: With increased ratios of lossy compression, a degradation of digital coronary angiograms occurs that results in decreased diagnostic accuracy. The sensitivity for detection of common diagnostic features was decreased, and subjective assessment of image quality was impaired. Caution is warranted in the interpretation of coronary angiograms that have been subjected to lossy JPEG compression beyond a ratio of 6:1.