bluuebunny/crossref_metadata_2025_split huggingface dataset:
Normalization of coronary vasomotion after percutaneous transluminal coronary angioplasty?
Authors: Suter T M , Buechi M , Hess O M , Haemmerli-Saner C , Gaglione A , Krayenbuehl H P 
Published: June 2012

BACKGROUND
Coronary vasomotion was evaluated at rest and during bicycle exercise in 33 patients (age, 53 +/- 7 years) with coronary artery disease. In a first group of patients (n = 15), vasomotion was studied before and 4.3 +/- 2.3 months (early) after percutaneous transluminal coronary angioplasty (PTCA), whereas in a second group (n = 18), exercise coronary arteriography was performed 30 +/- 11 months (late) after successful PTCA. Patients with restenosis (percent area stenosis greater than or equal to 75% or percent diameter stenosis greater than or equal to 50%) were excluded.

METHODS AND RESULTS
Luminal areas of a normal segment and the stenotic segment were determined at rest, during supine bicycle exercise, and 5 minutes after sublingual nitrate administration by using biplane quantitative coronary arteriography. Work loads before and early after PTCA were identical in group 1 and similar late after PTCA in group 2. Percent area stenosis decreased from 86% to 36% (p less than 0.001) in group 1 and from 93% to 46% (p less than 0.001) in group 2. Normal coronary arteries showed mild vasodilation during exercise before (+3%, NS versus rest), early (+7%, NS versus rest), and late after (+10%, p less than 0.05 versus rest) PTCA. Administration of sublingual nitrate was associated with significant vasodilation of the normal vessel segment before (+27%, p less than 0.001 versus rest), early (+31%, p less than 0.001 versus rest), and late (+21%, p less than 0.001 versus rest) after PTCA. In contrast, the stenotic vessel segments showed coronary vasoconstriction during exercise before PTCA (-25%, p less than 0.001 versus rest), whereas minimal vasomotion was observed early (+2%; NS versus rest) as well as late (+5%; NS versus rest) after PTCA. Individual post-PTCA (early and late) exercise data elicited vasodilation in 19, no vasomotion in four, and vasoconstriction in 10 instances. Sublingual administration of nitrate was associated with a significant increase in minimal luminal area before (+18%, p less than 0.05 versus rest), early (+24%, p less than 0.01 versus rest), and late (+16%, p less than 0.001 versus rest) after PTCA. An inverse linear correlation was found between the percent change in minimal luminal area during peak exercise and percent area stenosis at rest (r = 0.77, p less than 0.001).

CONCLUSIONS
Exercise-induced stenosis narrowing is observed before PTCA but normal vasomotion is reestablished in two thirds of all patients early and late after PTCA. In one third, an abnormal reaction to exercise (i.e., vasoconstriction) persisted after PTCA, mainly in those patients with a residual area stenosis of 50% (percent diameter stenosis of 30%) or more. Thus, PTCA appears to have a salutary effect on coronary vasomotion during exercise, which, however, remains dependent on the severity of the residual stenosis.
Regional oxidative metabolism in patients after recovery from reperfused anterior myocardial infarction. Relation to regional blood flow and glucose uptake.
Authors: Vanoverschelde J L , Melin J A , Bol A , Vanbutsele R , Cogneau M , Labar D , Robert A , Michel C , Wijns W 
Published: June 2012

BACKGROUND
Enhanced uptake of the glucose analogue 18F-fluorodeoxyglucose (FDG) in relation to flow has been proposed as an accurate method of identifying viable myocardium. The evaluation of myocardial oxidative metabolism could be an alternate way to identify reversible injury. The aim of the present study was to investigate in patients with reperfused anterior infarction whether differences in regional oxidative metabolism exist among regions with and without flow-metabolism mismatch.

METHODS AND RESULTS
Fifteen patients with reperfused anterior myocardial infarction were studied between 2 weeks and 3 months after the acute event. Regional myocardial blood flow (13N-ammonia; three-compartment model), oxidative metabolism (11C-acetate; monoexponential clearance), and glucose uptake (FDG, linear graphic analysis) were evaluated with dynamic positron emission tomography. Flow-metabolism patterns were used to differentiate reversibly (FDG/flow greater than 1.2) from irreversibly injured myocardium (FDG/flow less than 1.2) using circumferential profile technique. Relative 13N-ammonia uptake was reduced in 71 of 90 anterior and/or septal segments, including 24 with (seven patients) and 38 without (eight patients) flow-metabolism mismatch. Acetate clearance (k), reflecting oxidative metabolism, was reduced by 51% in the center of the infarct area versus remote segments (27 +/- 12 versus 55 +/- 13 min-1.10(-3), p less than 0.001). Compared with infarct segments without flow-metabolism mismatch, segments exhibiting increased glucose uptake relative to flow had faster acetate clearance (35 +/- 14 versus 23 +/- 9 min-1.10(-3), p less than 0.01). Similarly, myocardial blood flow was better preserved in segments with flow-metabolism mismatch (54 +/- 13 versus 45 +/- 8 ml/min/100 g, p less than 0.01) compared with segments without mismatch. However, at similar levels of hypoperfusion, there was no significant difference in acetate clearance among segments with and those without flow-metabolism mismatch: 37 +/- 14 versus 41 +/- 15 min-1.10(-3), respectively. A positive correlation (r = 0.89, p less than 0.001) was found between absolute myocardial blood flow and acetate clearance, regardless of the flow-metabolism pattern.

CONCLUSIONS
In patients with reperfused myocardial infarction studied between 2 weeks and 3 months after the acute event, regional oxidative metabolism is reduced in proportion to residual myocardial blood flow and does not differ significantly among similarly hypoperfused segments with and without flow-metabolism mismatch.
Physiological substrate for antidromic reciprocating tachycardia. Prerequisite characteristics of the accessory pathway and atrioventricular conduction system.
Authors: Packer D L , Gallagher J J , Prystowsky E N 
Published: June 2012

BACKGROUND
Although the anatomic "substrate" for the occurrence of antidromic reciprocating tachycardia (ART) has been previously examined, the underlying physiological substrate for this unusual arrhythmia in patients with the Wolff-Parkinson-White syndrome has not been thoroughly characterized.

METHODS AND RESULTS
The electrophysiological properties of the accessory pathway and normal ventriculoatrial conduction system in 30 patients with ART and a single accessory pathway were compared with those observed in a control group of 36 patients without this arrhythmia to elucidate the critical physiological substrate essential for the development and maintenance of ART. Inducible ART had a mean cycle length of 286 +/- 31 msec. The average retrograde ventriculoatrial conduction system effective refractory period in ART patients was significantly less than that in the control group (244 +/- 32 versus 291 +/- 46 msec, p = 0.0002). All of the ART patients showed retrograde conduction over the normal conduction system at cycle lengths of less than or equal to 360 msec; 23 had 1:1 conduction to less than or equal to 300 msec, and 16 showed 1:1 propagation at cycle lengths of less than or equal to 260 msec. The shortest cycle length accompanied by 1:1 retrograde propagation over the normal conduction system in patients with ART was also significantly less than that observed in the control group (274 +/- 39 versus 347 +/- 73 msec, p less than 0.001). The accessory pathway anterograde ERP in ART patients with 1:1 retrograde conduction over the normal ventriculoatrial conduction system at cycle lengths of less than or equal to 360 was significantly less than that seen in comparable control patients (247 +/- 23 versus 284 +/- 56 msec, p = 0.001), and the accessory pathway location was significantly further from the atrioventricular node in 21 patients with ART undergoing surgery than that in 22 operated control patients (3.8 +/- 0.8 versus 2.9 +/- 0.8 mapping units, p = 0.0025) who also had retrograde ventriculoatrial conduction to cycle lengths of less than or equal to 360 msec. No significant differences in anterograde atrioventricular conduction system properties, retrograde accessory pathway refractoriness, or shortest ventricular pacing cycle lengths maintaining 1:1 conduction via the accessory pathway were observed between groups.

CONCLUSIONS
This quantitative characterization of the properties of conduction and refractoriness of both the accessory pathway and ventriculoatrial conduction system and the relation between these characteristics and the accessory pathway location in ART patients provides additional insight into the prerequisites for the initiation and maintenance of this rhythm disturbance.
Effect of xamoterol in Shy-Drager syndrome.
Authors: Obara A , Yamashita H , Onodera S , Yahara O , Honda H , Hasebe N 
Published: June 2012

BACKGROUND
Xamoterol, a cardioselective beta 1-adrenoceptor partial agonist, has been reported to be effective on postural hypotension. We investigated the effect of xamoterol in five patients with Shy-Drager syndrome (SDS) in relation to their prevailing sympathetic nerve activity and sensitivity of beta-adrenoceptors and the change in circadian variation of blood pressure.

METHODS AND RESULTS
Ambulatory blood pressure over 24 hours was monitored by noninvasive sphygmomanometer (model 5200, Spacelab). Plasma norepinephrine levels of SDS patients were significantly lower than that of normal subjects (n = 5) both at rest (54 +/- 15 versus 178 +/- 83 pg/ml) and after 10-minute standing (74 +/- 24 versus 318 +/- 143 pg/ml). Infusion of isoproterenol (0.02 micrograms/kg/min) produced a mild rise of systolic blood pressure and tachycardia in normal subjects but resulted in marked hypotension and tachycardia in SDS subjects. After xamoterol administration (200 mg b.i.d.), systolic blood pressure and heart rate were significantly increased in the averages during the day; however, increases were more pronounced at night. In two of the five patients, the improvement in dizziness was large enough to enable them to increase their daily activities.

CONCLUSIONS
Our observations suggest that 1) beta 1-selective, high intrinsic sympathomimetic activity of xamoterol increases blood pressure and heart rate in patients with SDS as a consequence of their prevailing beta 1-adrenoceptor hypersensitive state, and 2) blood pressure monitoring over 24 hours appears to have important advantages in evaluating the therapeutic effects on postural hypotension.
Prevalence of cardiovascular risk factors in rural and urban Costa Rica.
Authors: Campos H , Mata L , Siles X , Vives M , Ordovas J M , Schaefer E J 
Published: June 2012

BACKGROUND
Coronary artery disease (CAD) is becoming more prevalent in developing countries, particularly in the urban areas, in contrast to the CAD mortality trends observed in some industrialized nations.

METHODS AND RESULTS
We determined the prevalence of cardiovascular risk factors (hypertension, diabetes, smoking, obesity, total cholesterol greater than or equal to 240 mg/dl and greater than or equal to 200 less than or equal to 239 mg/dl, low density lipoprotein (LDL) cholesterol greater than or equal to 160 mg/dl and greater than 130 less than or equal to 159 mg/dl, and high density lipoprotein (HDL) cholesterol less than 35 mg/dl) in 222 men and 243 women from rural and urban areas of Puriscal, Costa Rica, using the American Cholesterol Education Program guidelines. Urban Puriscal men had a significantly (p less than 0.05) higher prevalence of borderline high-risk total cholesterol (26% versus 14%), borderline high-risk LDL cholesterol (21% versus 11%), smoking (32% versus 13%), and higher prevalence of low HDL cholesterol (34% versus 24%), hypertension (16% versus 13%), diabetes (4.5% versus 2.7%), obesity (21% versus 14%), and saturated fat intake greater than 15% of calories (14% versus 7%) than rural men from Puriscal. No significant differences between rural and urban women were found for any of the cardiovascular risk factors. Urban Puriscal residents were also more sedentary than rural Puriscal residents.

CONCLUSIONS
These data indicate that modifiable risk factors are more prevalent in urban than in rural Puriscal, Costa Rica, particularly in men.
In vivo relation of intramyocardial blood volume to myocardial perfusion. Evidence supporting microvascular site for autoregulation.
Authors: Wu X S , Ewert D L , Liu Y H , Ritman E L 
Published: June 2012

BACKGROUND
The goal of this study was to explore the role of several factors that affect intramyocardial blood volume by using minimally invasive computed tomography. Anesthetized dogs were scanned with the dynamic spatial reconstructor, a high-speed tomographic scanner, during injection of a bolus of iohexol into the aortic root.

METHODS AND RESULTS
In control dogs, it is indicated that the fraction of myocardium that is blood (FMB, %) relates to myocardial perfusion (F, milliliters per gram per minute) in that region as FMB congruent to a.F1/2, where a = 9.5 +/- 1.2% (milliliters times minute per gram)1/2 (mean +/- SD) in the subendocardium and a = 9.6 +/- 1.1% in the subepicardium. In another group of dogs, for the myocardium perfused by a stenosed epicardial artery, a increased to approximately 10 for a 25-43% stenosis (or pressure gradient of 9 mm Hg across narrowing) and to greater than 11 for a 50-55% stenosis (or pressure gradient of 40 mm Hg across narrowing). In these dogs, flow was not impaired under control hemodynamic conditions, but the usual increase of flow (i.e., flow reserve) observed under maximum vasodilation conditions was impaired. In another group of dogs, progressive embolization (using 15-microns-diameter microspheres) of the left ventricular myocardial microcirculation caused the value of a to remain at approximately 9.5 with embolization up to 50% of the fatal dose of microspheres, but it then decreased progressively with embolization to 4.6 at the fatal dose.

CONCLUSIONS
We conclude that the FMB/F relation reflects hemodynamic conductance at the microvascular level.
Heat shock protein induction in rat hearts. A role for improved myocardial salvage after ischemia and reperfusion?
Authors: Donnelly T J , Sievers R E , Vissern F L , Welch W J , Wolfe C L 
Published: June 2012

BACKGROUND
To test the hypothesis that the heat shock response is associated with improved myocardial salvage after myocardial ischemia and reperfusion, rats treated with prior whole-body hyperthermia and 24 hours of recovery (n = 26) or 20 minutes of ischemic pretreatment and 8 hours of recovery (n = 24) and control rats (n = 27, n = 24, for hyperthermic and ischemic pretreatment, respectively) were subjected to 35 minutes of left coronary artery (LCA) occlusion and 120 minutes of reperfusion.

METHODS AND RESULTS
Although ventricular samples from rats subjected to either hyperthermia (n = 7) or ischemic pretreatment (n = 6) all showed induction of HSP72 (heat shock protein), Western blot analysis revealed significantly greater amounts of HSP72 in samples obtained from rats subjected to hyperthermia compared with those from rats subjected to ischemic pretreatment. Control rats (n = 7) showed no significant presence of myocardial HSP72. After 35 minutes of LCA occlusion and 2 hours of reperfusion, infarct size was significantly reduced in heat-shocked rats compared with controls (8.4 +/- 1.7%, n = 26 versus 15.5 +/- 1.9%, n = 27; p = 0.007; mean +/- SEM; infarct mass/left ventricular mass x 100). There were no significant differences in left ventricular (LV) systolic pressure, heart rate, LV dP/dt, or rate-pressure product between heat-shocked (n = 11) and control (n = 14) rats during the ischemic period. There were no differences in infarct size between ischemically pretreated and control rats subjected to 35 minutes of ischemia and reperfusion (9.7 +/- 2.1%, n = 23 versus 10.0 +/- 2.1, n = 24; p = NS).

CONCLUSIONS
In this model of ischemia and reperfusion, prior heat shock was associated with significantly improved myocardial salvage after 35 minutes of LCA occlusion and reperfusion. This improved salvage was correlated with marked HSP72 induction and was independent of the hemodynamic determinants of myocardial oxygen supply and myocardial oxygen demand during the ischemic period. In contrast, mild HSP72 induction by ischemic pretreatment was not associated with improved myocardial salvage after myocardial ischemia and reperfusion. Thus, the absolute levels of HSP72 may be important in conferring protection from ischemic injury in this animal model.
Coronary cyclic flow variations "precondition" ischemic myocardium.
Authors: Ovize M , Kloner R A , Hale S L , Przyklenk K 
Published: June 2012

BACKGROUND
Repeated brief episodes of myocardial ischemia performed by mechanical clamping of a coronary artery "precondition" the heart and reduce infarct size after a subsequent sustained ischemia. It is not known, however, whether spontaneous episodes of transient ischemia caused by formation of platelet thrombi, which may occur in unstable angina, have a similar cardioprotective effect.

METHODS AND RESULTS
Therefore, our objective was to determine whether brief spontaneous thrombotic episodes of ischemia/reperfusion could limit infarct size and preserve contractile function following 60 minutes (protocol 1) or 90 minutes (protocol 2) of sustained ischemia and 4-4.5 hours of reperfusion in the canine model. Before the sustained coronary occlusion, dogs underwent a 30-minute "treatment" period consisting of: no intervention (control group), four repeated episodes of 3-minute mechanical occlusion plus 5-minute reperfusion (preconditioned group), or coronary artery stenosis and endothelial injury, resulting in a mean of four spontaneous episodes of cyclic flow variations (CFV group) caused by formation and dislodgment of platelet thrombi. In protocol 1 (60-minute sustained ischemia plus 4.5-hour reperfusion), infarct size was significantly smaller in both the preconditioned and CFV groups compared with controls (3.5 +/- 1.4%,* 3.4 +/- 2.1%,* and 9.9 +/- 2.7% of the myocardium at risk, respectively; *p less than 0.05 versus control). In contrast, neither preconditioning nor CFV preserved contractile function: Segment shortening during sustained occlusion was equally depressed at -15% to -20% of baseline values among the three groups and equally stunned at +12% to +18% of baseline during the 4.5 hours of reflow. In protocol 2 (90-minute sustained ischemia plus 4-hour reperfusion), only CFV continued to exert a cardioprotective effect: Infarct size averaged 15.0 +/- 4.1%, 7.4 +/- 2.5%,* and 16.5 +/- 4.4% of the region at risk in the preconditioned, CFV, and control groups, respectively (*p less than 0.05 versus control). Contractile function, however, was similar among all three groups both during 90 minutes of sustained occlusion and throughout 4 hours of reperfusion.

CONCLUSIONS
We therefore conclude that repeated coronary thrombus formation preconditions the ischemic myocardium: In fact, in contrast to mechanical preconditioning, cardioprotection provided by CFV persisted following 90 minutes of sustained coronary occlusion. However, preconditioning by thrombotic or mechanical occlusion neither preserved myocardial contractile function during sustained coronary occlusion nor prevented stunning after reperfusion. These data raise the possibility that clinical episodes of unstable angina prior to acute myocardial infarction may precondition the ischemic myocardium.
Effects of high arterial oxygen tension on function, blood flow distribution, and metabolism in ischemic myocardium.
Authors: Cason B A , Wisneski J A , Neese R A , Stanley W C , Hickey R F , Shnier C B , Gertz E W 
Published: June 2012

BACKGROUND
Although oxygen inhalation therapy has long been used in the treatment of acute myocardial ischemia, experimental evidence that increased arterial PO2 has any beneficial effect in the absence of hypoxemia is equivocal. In this study, we used a swine model of subendocardial myocardial ischemia to determine the effects of arterial hyperoxia on regional myocardial contractile function (sonomicrometry), myocardial blood flow distribution (microspheres), and regional myocardial glycolytic metabolism (carbon isotope-labeled substrates).

METHODS AND RESULTS
In 10 domestic swine, the left anterior descending coronary artery was cannulated and flow to this artery was strictly controlled via a roller pump in the perfusion circuit. Arterial PO2 was controlled by manipulating inspired oxygen concentration (FIO2). Low-flow myocardial ischemia was induced by reducing pump flow to 50% of the control value, which diminished regional endocardial systolic shortening to 30-50% of normal. After a 15-minute period of flow stability, each animal was exposed in randomized order to two additional 15-minute experimental periods: coronary normoxia (PO2 = 90-110 mm Hg) and coronary hyperoxia (PO2 greater than 400 mm Hg). At each level of oxygenation, we measured regional myocardial function, regional myocardial blood flow and metabolism, and hemodynamic indexes of myocardial oxygen demand. Myocardial ischemia during normoxia reduced systolic shortening to 10.9 +/- 5.3% in the ischemic zone. Hyperoxia increased ischemic zone systolic shortening substantially to 15.2 +/- 4.6%. During myocardial ischemia, endocardial blood flow was decreased to 0.26 +/- 0.06 ml.g-1.min-1 in the ischemic zone. During hyperoxia, endocardial blood flow rose to 0.34 +/- 0.10 ml.g-1.m-1. The endocardial: epicardial flow ratio was 0.45 +/- 0.18 in the initial ischemia period and rose to 0.61 +/- 0.23 in the hyperoxic period. Myocardial ischemia increased regional uptake of glucose, conversion of glucose to released lactate, and net myocardial lactate release. In the ischemic myocardium, coronary hyperoxia decreased both chemically measured lactate production and isotopically measured lactate release and decreased glucose extraction and the conversion of glucose to lactate.

CONCLUSIONS
These data demonstrate for the first time that increasing arterial PO2 to high levels during acute low-flow myocardial ischemia improves both function and flow distribution in the ischemic myocardium and decreases glycolytic metabolism in the ischemic zone. The degree of improvement in contractile function (5% absolute increase in systolic shortening or 25% change normalized to preischemic values) is consistent with the observed increase in subendocardial blood flow.