bluuebunny/crossref_metadata_2025_split huggingface dataset:
Postischemic free radical production in the venous blood of the regionally ischemic swine heart. Effect of deferoxamine.
Authors: Mergner G W , Weglicki W B , Kramer J H 
Published: June 2012

BACKGROUND
We tested the hypothesis that secondarily produced free radicals can be detected in venous coronary effluent without the need for direct exposure of postischemic tissue to the spin trapping agent alpha-phenyl-tert-butylnitrone (PBN).

METHODS AND RESULTS
The left anterior descending coronary artery (LAD) of pigs was ligated for 15, 30, 40, or 60 minutes, and the tissue was subsequently reperfused for 60 minutes. Venous effluent (6.5 ml) from the risk area was withdrawn sequentially at 1.5-minute intervals during reperfusion. The effluent blood was immediately infused (4.5 ml/min) with an isotonic saline solution containing 120 mM PBN: Preischemic control effluent samples were collected in an identical fashion. Plasma from each sample was extracted in organic solvent and subsequently analyzed by electron spin resonance (ESR) spectroscopy. Another group of pigs received an infusion of the metal chelator deferoxamine mesylate (25 mg/kg/hr) into the right atrium starting 1 hour before the 40-minute ligation and continuing throughout ligation and reperfusion. We were able to demonstrate the postischemic production of ESR signals for PBN adduct(s) from untreated hearts having spectral characteristics similar to an alkoxyl adduct (PBN-RO.; hyperfine splitting constants for beta-hydrogen [alpha H] = 2.0-2.25 G; nitrogen [alpha N] = 13.5-13.75 G). The reperfusion time course of PBN adduct production had a unique pattern: 1) multiple low-level bursts during the initial 15 minutes of reperfusion, and 2) a prominent PBN adduct signal during a relatively late time (20-25 minutes) of reperfusion. Total postischemic PBN adduct production rose with increasing duration (15-60 minutes) of ischemia and was associated with a progressive elevation of total lactate dehydrogenase in the effluent. Infusion of deferoxamine markedly diminished PBN adduct production as well as total release of lactate dehydrogenase.

CONCLUSIONS
These data suggest the potential feasibility of using an ex vivo ESR spin trapping technique in blood-perfused models of cardiovascular injury and that chelatable free iron contributes to the production of alkoxyl radicals.
Role of collagen in acute myocardial infarct expansion.
Authors: Whittaker P , Boughner D R , Kloner R A 
Published: June 2012

BACKGROUND
We sought to determine if damage to the myocardial collagen network was the cause of infarct expansion.

METHODS AND RESULTS
Using polarized light microscopy, we examined sections from rat hearts obtained at 1, 2, 3, and 4 days after permanent coronary artery occlusion. Three features of the collagen network likely to be important in resisting infarct expansion were assessed: collagen quality, collagen quantity, and collagen organization. We observed a decrease in the number of normally birefringent collagen fibers in the infarct as early as 1 day after infarction. This decrease correlated significantly with time (r = -0.989, p less than 0.001). In addition, we found that the fewer normally birefringent collagen fibers present, the greater the degree of infarct expansion (assessed by measurement of total left ventricular cross-sectional area). At 4 days after infarction, we noted a loss of intermyocyte collagen struts and loss of interstitial space. These changes coincided with the onset of pronounced infarct expansion. The loss of collagen struts is consistent with the concept that expansion proceeds via slippage of myocytes previously tethered by the struts. The loss of interstitial space may represent the resolution of interstitial edema, which could further weaken the ventricular wall.

CONCLUSIONS
The correlation of infarct expansion with collagen damage and the loss of support provided by collagen struts suggest that collagen is important in maintaining structural integrity after acute myocardial infarction.
Double-transseptal, double-balloon valvuloplasty for congenital mitral stenosis.
Authors: Grifka R G , O'Laughlin M P , Nihill M R , Mullins C E 
Published: June 2012

BACKGROUND
Eight patients with severe congenital mitral stenosis underwent double transseptal, double-balloon valvuloplasty; two had isolated congenital mitral stenosis, six had additional cardiac defects, and one had previous surgical valvotomy. Ages ranged from 0.6 to 36 years (median, 9 years).

METHODS AND RESULTS
All procedures were tolerated well. After valvuloplasty, the left atrial a wave minus the left ventricular end-diastolic pressure (LVEDP) gradient was reduced from 25 +/- 6 mm Hg to 9 +/- 3 mm Hg (p less than 0.001), the mitral valve mean gradient was reduced from 18 +/- 7 mm Hg to 8 +/- 3 mm Hg (p = 0.003), and the LVEDP was unchanged. All patients had marked clinical improvement. Only one patient developed significant mitral regurgitation. Two of the first four patients underwent repeat balloon valvuloplasty 7 months later. Follow-up evaluation on six patients from 4 to 54 months revealed no recurrence of symptoms or increased mitral regurgitation.

CONCLUSIONS
Double transseptal, double-balloon valvuloplasty is an effective treatment for many forms of congenital mitral stenosis. Mitral regurgitation is uncommon after this procedure. The double transseptal approach results in less trauma to the atrial septum and femoral veins and allows easy assessment of any residual postvalvuloplasty gradient.
Independent and incremental prognostic value of tests performed in hierarchical order to evaluate patients with suspected coronary artery disease. Validation of models based on these tests.
Authors: Pollock S G , Abbott R D , Boucher C A , Beller G A , Kaul S 
Published: June 2012

BACKGROUND
The additive prognostic value of tests done in a hierarchical order for the detection of coronary artery disease (CAD) is not always known. The principal goal of this study, therefore, was to assess the incremental prognostic value of data obtained in succession (clinical, exercise stress testing, 201Tl imaging, and coronary angiography) in patients with suspected CAD. A second goal was to develop models for determining prognosis based on results of these tests and to test the clinical validity of these models in unrelated patients.

METHODS AND RESULTS
Data from two groups of patients who had undergone such evaluation and had been followed for a mean of 4.4 years were analyzed. There were 204 patients from Massachusetts General Hospital (MGH) and 299 from the University of Virginia (UVA). There were 20 deaths and 21 nonfatal infarctions in the MGH group and 41 deaths and nine infarctions in the UVA group. Both univariate and multivariate Cox regression analyses were performed to assess the individual and incremental prognostic value of these tests. In both groups, 201Tl imaging provided significant additional prognostic information compared with clinical and exercise stress test data (p less than 0.05). At MGH, where the lung/heart 201Tl ratio had been analyzed, coronary angiography did not provide additional prognostic information. In this group of patients, the combination of clinical and exercise 201Tl variables provided greater prognostic information than the combination of clinical and angiographic data (p less than 0.001). In the UVA cohort, in which the lung/heart ratio had not been analyzed, coronary angiography provided incremental prognostic information compared with clinical and exercise 201Tl data alone (p less than 0.05). When models developed using data from either sample were applied to the other unrelated sample, there was often close agreement between the overall observed rates and those predicted by the models. This was also true for the low-risk and high-risk subgroups. Some models, however, did not perform as well as other models, which suggests that models that do well in one sample may not always be generalized to other groups.

CONCLUSIONS
Tests performed in hierarchical order for the evaluation of suspected CAD provide additional prognostic information. Models developed using clinically relevant combinations of test results obtained from different patient populations are frequently able to predict absolute levels of survival in unrelated but similar samples.
Contractile properties and Ca2+ release activity of the sarcoplasmic reticulum in dilated cardiomyopathy.
Authors: D'Agnolo A , Luciani G B , Mazzucco A , Gallucci V , Salviati G 
Published: June 2012

BACKGROUND
We performed a comparative study on Ca2+ release activity of the sarcoplasmic reticulum and calcium sensitivity of contractile apparatus of chemically skinned myocardial fibers obtained from four nonfailing human hearts and 13 excised hearts from patients with idiopathic dilated cardiomyopathy.

METHODS AND RESULTS
Ca2+ sensitivity of contractile apparatus was studied by following the isometric tension developed by chemically skinned myocardial fibers challenged with solutions of decreasing pCa. Ca2+ release from sarcoplasmic reticulum was monitored indirectly by measurement of the isometric tension developed by skinned fibers challenged with caffeine. We observed no significant difference of Ca2+ sensitivity and cooperativity between normal myocardium (pCa50 = 6.00 +/- 0.05; Hill coefficient, nHill = 2.07 +/- 0.10) and dilated cardiomyopathy (pCa50 = 6.03 +/- 0.07; nHill = 2.72 +/- 0.30) when the fibers were stretched to 130% of the resting length. We also found that both in normal myocardium and dilated cardiomyopathy, stretching to 150% of the resting length increased the Ca2+ sensitivity of the contractile system; pCa50 = 6.21 +/- 0.01 and 6.13 +/- 0.04 in normal and dilated cardiomyopathy, respectively, whereas in dilated cardiomyopathy there was a decrease of Hill coefficient with stretching that was not observed in the control group. The caffeine threshold in idiopathic dilated cardiomyopathy was markedly increased compared with the control group, 1.94 +/- 0.27 mmol/l and 0.29 +/- 0.04 mmol/l caffeine, respectively, whereas there were no significant differences in the extent and rate of caffeine-induced Ca2+ release.

CONCLUSIONS
These results indicate that in idiopathic dilated cardiomyopathy there is no alteration of contractile and regulatory proteins; on the contrary, the gating mechanism of the Ca2+ release channel of sarcoplasmic reticulum is abnormal, suggesting a possible involvement of the excitation-contraction coupling in the pathogenesis of this disease. It should also be taken into account, however, that the increased caffeine threshold in dilated cardiomyopathy would be a result of the enhanced resistance to the skinning procedure secondary to the modification of lipid species and/or content in sarcoplasmic reticulum membrane.
Importance of intraluminal pressure on hemodynamics and vasoconstriction responses of stenotic arteries.
Authors: Ghods M , Mangal R , Iskandrian A S , Santamore W P 
Published: June 2012

BACKGROUND
Clinical and morphological studies clearly indicate that most human coronary artery stenoses are capable of vasomotion. Variable ischemic thresholds, ischemia unrelated to work load, and variant angina further show the presence and importance of vasoconstriction in coronary artery stenosis. Despite the importance of vasoconstriction, the effect of intraluminal pressure on the hemodynamic response to vasoconstrictors has not yet been examined. Intraluminal pressure is a primary determinant of vessel size and the force opposing vasoconstriction. Accordingly, we examined the effects of intraluminal pressure on the hemodynamic response to norepinephrine (NE)-induced vasoconstriction.

METHODS AND RESULTS
In canine carotid arteries perfused with physiological salt solution, pressures at the proximal and distal ends of the artery, as well as flow, were continuously recorded. We altered intraluminal pressure using three diverse interventions: changes in perfusion pressure, decreasing distal resistance, and collaterals. In normal, nonstenotic arteries, NE decreased the external vessel diameter but did not reduce flow. Perfusion pressure changes did not affect the ED50 of the NE-diameter relation. After an intraluminal stenosis was created, NE-induced constriction decreased flow. The threshold concentration of NE needed to decrease flow decreased as the perfusion pressure decreased (38.5 +/- 17.9, 2.3 +/- 1.3, and 0.12 +/- 0.1 x 10(-7) mol/l for 125, 100, and 75 mm Hg of perfusion pressure, respectively; p less than 0.05). Lowering distal resistance decreased stenotic pressure and decreased the threshold NE concentration from 5.4 +/- 1.9 to 0.34 +/- 0.2 x 10(-7) mol/l (p less than 0.05), and increasing stenotic pressure with collaterals increased the threshold NE concentration from 2.6 +/- 1.4 to 7.5 +/- 4.6 x 10(-7) mol/l (p less than 0.05).

CONCLUSIONS
In stenotic arteries, interventions that lowered the intraluminal pressure decreased the threshold NE concentration needed to decrease flow, and interventions that raised the intraluminal pressure increased the threshold NE concentration. This pressure-dependent constrictor sensitivity affects the vasomotor tone and is important in pathophysiology of ischemia occurring with hypotension (low perfusion pressure) or mild increase in myocardial oxygen demand (low distal arteriolar resistance). The results also suggest that collaterals, by maintaining stenotic pressure, could decrease the constrictor sensitivity and prevent ischemia.
Programmed electrical stimulation and drugs identify two subgroups of ventricular tachycardias occurring 16-24 hours after occlusion of the left anterior descending artery.
Authors: Vos M A , Gorgels A P , Leunissen J D , Havenith M G , Kriek E , Smeets J L , Wellens H J 
Published: June 2012

BACKGROUND
Spontaneous sustained ventricular tachycardia (VT) occurring 16-24 hours after left anterior descending (LAD) coronary artery occlusion in the canine heart is most likely based on abnormal automaticity. In vitro, it has been demonstrated that the rate of the arrhythmia and the effect of overdrive pacing depends on the maximal diastolic potential (MDP). The MDP is also of importance in understanding the effect of antiarrhythmic drugs. To study 1) the possible presence of different responses to overdrive pacing and 2) the relation between the response to overdrive pacing and the effect of different antiarrhythmic drugs in the intact heart, we investigated the effect of 1) (prolonged) pacing and 2) lidocaine (3 mg/kg), verapamil (0.4-1.0 mg/kg), or flunarizine (2 mg/kg) during VT.

METHODS AND RESULTS
In 21 conscious dogs with chronic atrioventricular block, 60 sustained VTs were observed 1 day after LAD occlusion. During VT, pacing with interstimulus intervals of 400, 300, and 200 msec for 15, 60, and 120 seconds was done on 40 VTs. Based on their response to pacing, VTs were divided into a pacing-suppressible (PS group) and a pacing-nonsuppressible group (PNS group). The mean cycle length in the PS group was significantly longer (410 +/- 50 msec) than in the PNS group (360 +/- 35 msec, p less than or equal to 0.01). Suppression was directly related to the rate and duration of pacing. Spontaneous recurrence of VTs was observed after 26 +/- 45 seconds. Lidocaine and verapamil increased cycle length of the suppressible VTs and terminated them, whereas flunarizine had no effect. Except for verapamil, which increased cycle length of the VTs, no effects were seen in the PNS group.

CONCLUSIONS
In conscious dogs showing sustained VTs 16-24 hours after LAD occlusion, 1) the slower VTs can be suppressed by pacing, verapamil, and lidocaine but not by flunarizine, and 2) the faster VTs are not affected by pacing, lidocaine, and flunarizine, and are only slowed by verapamil. These findings are compatible with in vitro findings of abnormal automaticity, with the slower VTs originating from a higher MDP than the faster VTs.
Initial and long-term outcome of 354 patients after coronary balloon angioplasty of total coronary artery occlusions.
Authors: Bell M R , Berger P B , Bresnahan J F , Reeder G S , Bailey K R , Holmes D R 
Published: June 2012

BACKGROUND
Coronary balloon angioplasty of chronic total occlusions is associated with relatively low success rates and a high incidence of restenosis. Whether there is long-term benefit in performing angioplasty of these lesions is unknown. The purpose of the present report was to analyze the long-term outcome of a large series of patients undergoing this procedure.

METHODS AND RESULTS
A computerized database analysis of 354 consecutive patients (from 1979 to 1990) who underwent coronary angioplasty of a chronic total coronary occlusion was performed (mean age, 62.3 years). Initial technical success was achieved in 69%; in 66%, success was achieved without procedural death or need for coronary artery surgery. During hospitalization, six patients suffered myocardial infarction, nine required emergency bypass surgery, and nine patients died. During a mean follow-up period of 2.7 years, no difference was found in survival or freedom from myocardial infarction among 234 successfully dilated patients compared with 120 patients with a failed attempt. However, the use of coronary artery bypass surgery was significantly less after successful dilation (p less than 0.0001 versus failed attempt). No significant difference in the cumulative incidence of severe angina was observed between these two patient populations, with the majority remaining asymptomatic. Restenosis occurred in 59% of 69 patients who returned for follow-up angiography.

CONCLUSIONS
Successful recanalization is achieved in the majority of patients undergoing angioplasty of chronic total occlusions and reduces the need for coronary artery bypass surgery. However, no major impact on either survival or incidence of myocardial infarction was noted after successful recanalization when patients with surgery were included.
Effects of lidocaine on relation between defibrillation threshold and upper limit of vulnerability in open-chest dogs.
Authors: Topham S L , Cha Y M , Peters B B , Chen P S 
Published: June 2012

BACKGROUND
The purpose of the present study was to test the effects of lidocaine on the relation between the defibrillation threshold and the upper limit of vulnerability.

METHODS AND RESULTS
The shock strength associated with a 50% probability of successful defibrillation (DFT50) and the shock strength associated with a 50% probability of reaching the upper limit of vulnerability (ULV50) were determined in 11 open-chest dogs by using the delayed up-down method before and during lidocaine (seven dogs) or normal saline (four dogs) infusion. The ventricles were paced at a cycle length of 300 msec. Shocks of various strengths were then given via a patch-patch electrode configuration on the anterior and posterior surfaces of the ventricle to determine the ULV50. Once ventricular fibrillation was induced, shocks were given 15-20 seconds later via the same electrode configuration to determine the DFT50. Lidocaine infusion resulted in a serum level of 15 +/- 4 micrograms/ml. This was associated with a lengthening of the QT interval but not with the widening of the QRS complex. In all dogs, both the ULV50 and the DFT50 increased significantly when tested during lidocaine infusion. Mean ULV50 during lidocaine infusion was 496 +/- 70 V or 13.1 +/- 4.3 J, which were significantly higher than the baseline values of 333 +/- 67 V or 5.3 +/- 2.2 J (p less than 0.001 for both voltage and energy). Mean DFT50 during lidocaine infusion was 407 +/- 41 V or 8.7 +/- 1.7 J, which were significantly higher than the baseline values of 300 +/- 38 V and 4.4 +/- 1.1 J (p = 0.004 for voltage and p = 0.013 for energy). The r values between the ULV50 and the DFT50 were 0.79 (p = 0.037) for voltage and 0.80 (p = 0.030) for energy at baseline and 0.85 (p = 0.016) for voltage and 0.88 (p = 0.009) for energy during the lidocaine infusion. However, the increments of the ULV50 (163 +/- 88 V or 7.8 +/- 4.6 J) were significantly greater than the increments of the DFT50 (107 +/- 51 V or 4.4 +/- 1.9 J, p = 0.035 for voltage and p = 0.023 for energy). Normal saline infusion did not alter DFT50 or ULV50.

CONCLUSIONS
Lidocaine infusion significantly increases both ULV50 and DFT50. These results are compatible with the upper limit of vulnerability hypothesis of defibrillation. However, the greater increase of the upper limit of vulnerability than the defibrillation threshold with lidocaine infusion indicates that other factors may also need to be considered to explain the results.
Evaluation of biplane color Doppler transesophageal echocardiography in 200 consecutive patients.
Authors: Omoto R , Kyo S , Matsumura M , Shah P M , Adachi H , Yokote Y , Kondo Y 
Published: June 2012

BACKGROUND
We developed the first biplane transesophageal echocardiography (TEE) probe with two orthogonal transducers, allowing synchronous side-by-side displays of the heart on a monitor TV, and compared its diagnostic value with that of conventional single-plane TEE using commercially available Doppler equipment in 200 consecutive patients intraoperatively, perioperatively, or on an outpatient basis.

METHODS AND RESULTS
Insertion was easy, except in one patient with a mediastinal tumor, and no complications were encountered. Both transverse and longitudinal scans allowed correct identification of true and false lumina in all 30 aortic dissection examinations, but longitudinal scanning was slightly superior in detecting types I and III entry sites. Three entries that were not detected by transverse scanning (two of DeBakey type I and one of type III) were visualized by longitudinal scanning. Among 37 cases of mitral regurgitation (MR), longitudinal scans were significantly superior (p less than 0.05) in revealing multiple jets (nine compared with two with transverse scanning). Although both planes yielded almost identical mean values for the maximum jet areas, a difference of over 50% in jet area size on the two planes was observed in 19 cases. The measured jet areas showed significant correlation with the angiographic MR grading, especially for the larger of the biplane measurements (p less than 0.01), and different grades showed little overlap. Longitudinal images increased the acoustic window of the heart and aorta from the esophagus. Moreover, longitudinal scanning provided good visualization of both ventricular outflow tracts, the ascending aorta, main pulmonary artery, and superior vena cava.

CONCLUSIONS
This modality greatly facilitates a three-dimensional comprehension of cardiovascular lesions and flow dynamics, especially in aortic dissection and MR, and its safety was demonstrated. Our data demonstrate the usefulness of this new technique in comparison with conventional single-plane TEE.