Ribose infusion accelerates thallium redistribution with early imaging compared with late 24-hour imaging without ribose.

To determine if early (4-h) thallium-201 imaging with ribose infusion would enhance detection of thallium redistribution better than late (24-h) imaging without ribose infusion, 15 patients with coronary artery disease underwent thallium stress tests by both methods within 2 weeks. All 15 patients had quantitative coronary angiography. After immediate postexercise planar imaging during the first of two exercise tests, patients were randomized to receive either intravenous ribose (3.3 mg/kg per min) or a control infusion of saline solution for 30 min. Images performed at 4 h for the ribose study were compared with those at 24 h for the saline control study. During the second test, exercise was carried to the same rate-pressure product and each patient received the opposite infusion. Four-hour postexercise images after ribose infusion identified 21 reversible defects not seen in the 24-h saline study. Three reversible defects were seen only in saline studies, but not with ribose at 4 h (p less than 0.01); 15 reversible defects were seen with both tests. When analyzed with respect to the 31 vascular territories supplied by a coronary artery with a greater than 50% stenosis, 8 territories had reversible defects present in the ribose but not the saline study and the saline study did not demonstrate reversible defects in territories that were seen in the ribose study (p less than 0.01). In 14 of these territories, reversible defects were seen with both tests. In 6 of 15 patients, additional vascular territories with reversible defects were identified after ribose infusion. It is concluded that ribose enhances the detection of thallium redistribution at 4 h compared with 24-h control images in patients with coronary artery disease and, therefore, substantially improves the identification of viable ischemic myocardium.

Influence of contrast media on thrombus formation during coronary angioplasty.

The influence of contrast media on thrombus formation during percutaneous transluminal coronary angioplasty was assessed in 124 consecutive patients undergoing coronary angioplasty and receiving either ionic (n = 57) (Group I) or nonionic (n = 67) (Group II) contrast medium. The presence of thrombus was assessed by qualitative analysis of angiograms in identical pre- and postangioplasty projections by four observers who had no knowledge of other data. Quantitation of stenosis severity before and after angioplasty and qualitative analysis of lesion eccentricity and complexity and of the presence of dissection were also performed. Although the baseline clinical characteristics of the two groups (including presenting syndromes and procedural and angiographic variables) did not differ, more patients in Group II than Group I developed new thrombus during coronary angioplasty (18% vs. 4%, p less than 0.02). In particular, patients with a presenting syndrome of recent myocardial infarction or rest angina, or both, and patients with an eccentric coronary plaque were more likely to develop new thrombus if they received nonionic than if they received ionic contrast medium (p less than 0.05). Patients with new thrombus formation and patients with thrombus present both before and after angioplasty had a high incidence of acute procedural complications (36% and 23%, respectively). Patients in Groups I and II had a similar incidence of ischemic events during follow-up.

Effect of ribose on thallium-201 myocardial redistribution.

Myocardial 201Tl redistribution after transient ischemia may be too slow to allow identification of a reversible myocardial defect within the routine 201Tl imaging period. To determine whether 201Tl redistribution could be affected by a metabolic intervention, intravenous ribose was administered postischemia. Seventeen domestic swine were subjected to a 10-min ischemic period followed by either a 30-min i.v. ribose (n = 8) or saline (n = 9) infusion. Thallium-201 was injected during ischemia and myocardial 201Tl activity was continuously monitored in ischemic and nonischemic regions with miniature CdTe radiation detection probes. Coronary flow in the ischemic region was reduced to 25% of that in the nonischemic regions in both saline and ribose groups. The 201Tl time-activity curves demonstrated a significant enhancement of % 201Tl redistribution in the ribose-treated animals at the end of ribose infusion: Ribose (48 +/- 11%), Saline (20 +/- 4%), p less than 0.05. Alteration of 201Tl kinetics by ribose may permit earlier recognition of 201Tl myocardial redistribution after transient ischemia.

Effect of thallium-201 blood levels on reversible myocardial defects.

To determine if 201Tl plasma blood levels correlate with the presence of reversible myocardial defects during exercise testing, 14 patients with stable coronary artery disease underwent two separate exercise 201Tl stress tests. Between initial and delayed imaging, on one test the patients drank an instant breakfast drink (eating) and on the other they drank an equivalent volume of water as a control (H2O). Thallium-201 imaging was performed immediately postexercise, immediately after eating/H2O and 210 min after eating/H2O. Between initial and immediate post eating/H2O images 201Tl reversible defects occurred in 27/38 regions in the H2O test versus 15/38 regions in the eating test (p = 0.02). Over this early time period, plasma 201Tl activity was significantly higher in the H2O test than eating test (p less than 0.05). In conclusion, early reversal of 201Tl defects may, in part, be the result of higher plasma 201Tl activity early after initial postexercise 201Tl imaging.

Ribose facilitates thallium-201 redistribution in patients with coronary artery disease.

To investigate whether i.v. infusion of ribose, an adenine nucleotide precursor, postischemia facilitates thallium-201 (201Tl) redistribution and improves identification of ischemic myocardium in patients with coronary artery disease (CAD), 17 patients underwent two exercise 201Tl stress tests, performed 1-2 wk apart. After immediate postexercise planar imaging, patients received either i.v. ribose (3.3 mg/kg/min x 30 min) or saline as a control. Additional imaging was performed 1 and 4 hr postexercise. Reversible defects were identified by count-profile analysis. Significantly more (nearly twice as many) reversible 201Tl defects were identified on the post-ribose images compared to the post-saline (control) images at both 1 and 4 hr postexercise (p less than 0.001). Quantitative analyses of the coronary arteriogram was available in 13 patients and confirmed that the additional reversible defects were in myocardial regions supplied by stenosed arteries. We conclude that ribose appears to facilitate 201Tl redistribution in patients with CAD and enhances identification of ischemic myocardium.

Effect of eating on thallium-201 myocardial redistribution after myocardial ischemia.

To determine whether eating a high-carbohydrate meal between initial and delayed postexercise thallium-201 (Tl-201) imaging affects detection of Tl-201 redistribution during exercise stress testing, 16 patients with stable angina performed 2 Tl-201 treadmill exercise stress tests within a 14-day interval. Immediately after initial postexercise imaging, patients either drank a commercially available instant breakfast preparation for the intervention test or drank an equivalent volume of water for the control test. Comparable exercise workloads were achieved by exercising patients to the same heart rate for both tests. The order of the 2 (intervention and control) tests were randomized. All patients had at least 1 region of Tl-201 myocardial redistribution on either their eating or control test scans, although only 7 of the 16 had positive treadmill exercise test responses. Forty-six regions showing Tl-201 myocardial redistribution were identified in all 144 regions examined. Significantly more of these regions were identified on control test scans than on eating test scans: 11 of 46 on both test scans, 6 of 46 only on eating test scans and 29 of 46 only on control scans (p less than 0.001). Consistent with results of the quantitative regional analysis, the percentage of Tl-201 clearance over 4 hours in the 46 Tl-201 myocardial redistribution regions was 39 +/- 8% for the eating tests and 29 +/- 8% for control tests (mean +/- standard deviation, p less than 0.003). In 4 patients diagnosis of transient ischemia would have been missed because their 14 Tl-201 myocardial redistribution regions were detected only on the control test scans.(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferative activity in coronary atherectomy tissue. Clinical, histopathologic, and immunohistochemical correlates.

STUDY OBJECTIVE: Although cellular proliferation is considered one of the dominant processes leading to restenosis following coronary intervention, controversy exists over the extent of cellular replication in atherosclerotic tissue. Accordingly, we sought to investigate the level and clinicopathologic correlates of proliferative activity in atherosclerotic tissue obtained via directional coronary atherectomy (DCA). DESIGN: Prospective observational study. SETTING: Tertiary care referral hospital. PATIENTS: Specimens retrieved via DCA from 37 lesions (primary, 26; restenosis, 11) were studied using single-label immunohistochemical staining for the proliferating cell nuclear antigen and basic fibroblast growth factor (bFGF). RESULTS: Restenosis tissue was significantly more likely than primary tissue to contain areas of intimal hyperplasia (64 vs 23%; p < 0.03). However, the frequency of positive staining for proliferating cell nuclear antigen (PCNA) was similar in primary and restenosis lesions (25 vs 30%; p = NS), and the mean percentage of positive cells per slide was similar in the two groups. Positive immunostaining for bFGF was present in 20 lesions (61%), and tended to be more frequently seen in restenotic lesions (80 vs 52%; p = 0.25). However, there was no correlation or colocalization between immunostaining for bFGF and proliferating cell nuclear antigen. We found no clinicopathologic correlations with respect to clinical outcome. CONCLUSIONS: Cellular replication, as measured by expression of the PCNA, occurs in a heterogeneous pattern in both primary and restenotic atherosclerotic tissue obtained from patients undergoing coronary intervention.

Characterization of chronically implanted ventricular endocardial pacing leads.

The expected implant lifetime of pacemaker generators has been extended with the introduction of lithium power sources. Consequently, the pacing lead may become the component that determines the total implant lifetime of the pacemaker. This fact emphasizes the necessity for accurate assessment of the integrity of a chronically implanted lead. In this study, chronic threshold and impedance data from 61 patients having the same type of ventricular endocardial lead for up to 10 years were retrospectively analyzed. The mean acute current threshold was 0.81 +/- 0.33 mA. The chronic current threshold had a range of between 1 and 5 mA, which was approximately two to five times greater than the acute implant value. Chronic voltage threshold and impedance were 0.7 to 4 V and 335 to 775 omega, respectively. The findings of this study provide general guidelines for chronic lead parameters and illustrate some of the difficulties encountered in gathering and interpreting long-term lead data.

Effects of brief coronary occlusion and reperfusion on porcine coronary artery reactivity.

The loss of coronary vasodilator reserve after ischemia-reperfusion may be due to endothelial injury, and this vascular dysfunction may contribute to functional alterations observed after ischemia. To determine whether endothelial dysfunction occurs after relatively brief periods of moderate low-flow ischemia in vivo, open-chest swine were subjected to 15 minutes of critical, subtotal left anterior descending coronary artery occlusion (80%) followed by 60 minutes of reperfusion. Serial measurements of regional coronary flow were made with the radiolabeled microsphere technique. After 60 minutes of reperfusion, the left anterior descending coronary artery was excised together with a section of the normally perfused left circumflex coronary artery to examine in vitro the relaxations to the endothelium-dependent dilators ADP and bradykinin and to the endothelial-independent dilators sodium nitroprusside and adenosine. Contractions to serotonin in quiescent rings were also examined. Endocardial and transmural blood flows recovered to preocclusion levels within 60 minutes of reperfusion, as did the epicardial-to-endocardial ratio. Vascular responses in isolated, reperfused left anterior descending coronary artery rings were significantly different from responses in control left circumflex coronary artery rings. Endothelium-dependent relaxations to adenosine diphosphate and bradykinin were significantly depressed in the left anterior descending coronary artery rings compared with left circumflex coronary artery rings (p less than 0.05). Serotonin-induced contractions were significantly greater in occluded-reperfused left anterior descending than in left circumflex coronary arteries (p less than 0.05). Relaxations to adenosine and sodium nitroprusside were not significantly different between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine and insulin mediate glucose uptake in normoxic rat hearts by different mechanisms.

The effect of adenosine (ADO) and its interaction with insulin (I) on myocardial glucose uptake was evaluated in the normoxic isolated rat heart using 2-[3H]deoxyglucose. Isovolumic hearts were perfused at constant flow with a nonrecirculating bicarbonate buffer containing 5.5 mM glucose as the sole substrate. After a 30-min equilibration period, the glucose and extracellular ([14C]sucrose) tracers were infused for 15 min before initiation of the 15-min experimental period. Both 100 microM ADO and 4 mU/ml I significantly increased glucose uptake (GU) compared with control values (in mumol.min-1 x g-1: ADO = 0.34 +/- 0.03, I = 0.44 +/- 0.03, control = 0.23 +/- 0.02; P < 0.05). In combination, ADO and I produced an additive increase in GU (0.54 +/- 0.03; P < 0.05 vs. control). The mechanism of enhanced GU by ADO and I was investigated with the glucose uptake inhibitors phloridzin (PZ) and phloretin (PT), each of which has a unique site of action on the cell membrane. ADO-mediated GU was completely blocked by 3 mM PZ (ADO + PZ = 0.20 +/- 0.01; P = NS vs. control), but I-stimulated GU was unaffected (I + PZ = 0.38 +/- 0.03; P = NS vs. I). Only GU attributable to ADO was blocked by PZ infused with ADO and I (ADO + I + PZ = 0.43 +/- 0.03; P = NS vs. I). Both ADO- and I-mediated GU were inhibited by 100 microM PT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine antagonism decreases metabolic but not functional recovery from ischemia.

The effect of adenosine receptor antagonism on function and metabolism was examined in isolated hearts during low flow ischemia and reperfusion. Isovolumic rat hearts perfused at constant flow were subjected to 30 min of ischemia followed by 30 min of reperfusion. Infusion of vehicle or 10 microM 8-phenyltheophylline (8-PT) was initiated 10 min before ischemia and maintained throughout reperfusion. 8-PT infusion had no significant effects on hemodynamic parameters or metabolism preischemia. During ischemia, left ventricular developed pressure declined to approximately 15% of preischemic values in control and 8-PT hearts, and ATP and PCr decreased to approximately 73 and 60% of preischemic values. Inorganic phosphate (Pi) increased to 353 = 41 and 424 +/- 53% of preischemic values in control and 8-PT hearts, respectively. After reperfusion, function recovered to greater than 95% of preischemic levels in control and 8-PT hearts. Unlike control hearts, recovery of metabolites was significantly different during reperfusion in 8-PT hearts (P less than 0.05); ATP, phosphocreatine, and Pi recovered to 82 +/- 8, 71 +/- 8, and 281 +/- 27% of preischemic values, respectively. Venous purine washout was significantly greater (P less than 0.05) during reperfusion in 8-PT hearts (327 +/- 113 nmol) than in control hearts (127 +/- 28 nmol). Blockade of adenosine receptors appears to adversely affect metabolic but not functional recovery in the ischemic-reperfused myocardium.

Guidelines for internal peer review in the cardiac catheterization laboratory. Laboratory Performance Standards Committee, Society for Cardiac Angiography and Interventions.

The Laboratory Performance Standards Committee of the Society for Cardiac Angiography and Interventions has proposed guidelines for establishing an internal peer review program in the cardiac catheterization laboratory. The first step is to establish a committee and a data base. This data base should include quality indicators that reflect: physician qualifications, outcomes of procedures, and processes of care. The outcomes must be risk-adjusted to account for the variable severity of illness. Data should be collected by catheterization laboratory personnel and entered into a laboratory-specific computerized data base. These data must be analyzed and organized into profiles that reflect the quality of care. Based on this information, the Committee would institute the following interventions to improve physician performance: education, clinical practice standardization, feedback and benchmarking, professional interaction, incentives, decision-support systems, and administrative interventions. The legal aspects of peer review are reviewed briefly.

Radiographic contrast agents and platelet function: a quenched-flow study.

Radiographic contrast media (RCM) may alter platelet behavior at concentrations achieved during cardiac angiography. We used quenched-flow aggregometry coupled to single-particle counting to study the influence of RCM on the kinetics of platelet aggregation (less than 5.0 sec) induced by adenosine diphosphate (ADP, 2.86 microM). At a concentration in platelet-rich plasma (PRP) of 5 per cent RCM by volume, platelet aggregation was inhibited by diatrizoate, iopamidol and ioxaglate either directly or following incubation of each contrast agent with PRP for 20 minutes. Diatrizoate inhibited more than did iopamidol or ioxaglate (56 +/- 6, versus 39 +/- 3 and 40 +/- 9 per cent respectively; P less than 0.003, p less than 0.009, n = 20 normal subjects). A small reduction (about 16 per cent) in aggregation velocity occurred within 5 seconds of exposure of PRP to all 3 RCM and the onset time (t) or lag period before aggregation begins was significantly prolonged by diatrizoate (p less than 0.03). The RCM vehicles alone (iodinated moiety removed, osmolality readjusted) had no effect on the ADP-induced aggregation. Platelet counts fell significantly after incubation with diatrizoate (12%; p = 0.04). Our data therefore show that early platelet aggregation was inhibited by 3 commonly-used ionic and nonionic contrast agents. Inhibition was apparently caused by the iodinated contrast molecule, began within seconds of platelet-RCM contact and was independent of vehicle composition. Since diatrizoate inhibited aggregation more than iopamidol or ioxaglate, its use may be of additional value during angiographic procedures in clinical situations involving enhanced platelet activation.