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61. |
Effect of Myocardial Fiber Direction on Epicardial Potentials |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3076-3090
Bruno Taccardi,
Emilio Macchi,
Robert Lux,
Philip Ershler,
Santa Spaggiari,
Silvana Baruffi,
Yonild Vyhmeister,
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摘要:
BackgroundUnderstanding the relations between the architecture of myocardial fibers, the spread of excitation, and the associated ECG signals is necessary for addressing the forward problem of electrocardiography, that is, predicting intracardiac and extracardiac ECGs from known intracardiac activity. So far, these relations have been studied experimentally only in small myocardial areas. In this study, we tested the hypothesis that potential distributions measured over extensive epicardial regions during paced beats reflect the direction of superficial and intramural fibers through which excitation is spreading in both the initial and later stages of ventricular excitation. We also tried to establish whether the features of the epicardial potential distribution that correlate with fiber direction vary as a function of pacing site, intramural pacing depth, and time elapsed after the stimulus. An additional purpose was to compare measured epicardial potentials with recently published numerical simulations depicting the three-dimensional spread of excitation in the heart muscle and the associated potential fields.Methods and ResultsThe hearts of 18 mongrel dogs were exposed and 182 to 744 unipolar electrograms were recorded from epicardial electrode arrays (2.3 × 3.0 to 6.5 × 6.5 cm). Hearts were paced at various intramural depths through an intramural needle. The overall number of pacing sites in 18 dogs was 241. Epicardial potential distributions, electrographic waveforms, and excitation time maps were displayed, and fiber directions in the ventricular wall underlying the electrodes were determined histologically. During the early stages of ventricular excitation, the position of the epicardial maxima and minima revealed the orientation of myocardial fibers near the pacing site in all cases of epicardial and intramural pacing and in 60% of cases of endocardial or subendocardial pacing. During later stages of propagation, the rotation and expansion of the positive areas correlated with the helical spread of excitation through intramurally rotating fibers. Marked asymmetry of potential patterns probably reflected epicardial-endocardial obliqueness of intramural fibers. Multiple maxima appeared in the expanding positive areas.ConclusionsFor 93% of pacing sites, results verified our hypothesis that epicardial potential patterns elicited by ventricular pacing reflect the direction of fibers through which excitation is spreading during both the initial and later stages of propagation. Epicardial potential distributions provided information on the site of origin and subsequent helical spread of excitation in an epicardial-endocardial, endocardial-epicardial, or double direction. Results were in agreement with previously published numerical simulations except for the asymmetry and fragmentation of the positive areas.
ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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62. |
Suppression of Thrombolysis in a Canine Model of Pulmonary Embolism |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3091-3097
James Marsh,
Ronald Konopka,
Irene Lang,
Huan-you Wang,
Craig Pedersen,
Peter Chiles,
Christopher Reilly,
Kenneth Moser,
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摘要:
BackgroundThe brisk fibrinolytic response of canines has impaired efforts to develop a canine model of chronic thromboembolic pulmonary hypertension. Difficulties in retaining chronic embolic residuals were partially overcome by administration of tranexamic acid (TXA) (Circulation. 1991;83:1272–1279.). In this study, we used type 1 plasminogen activator inhibitor (PAI-1), a major inhibitor of the endogenous fibrinolytic system, to determine its efficacy in the suppression of thrombolysis in canines.Methods and ResultsThrombus was induced in the inferior vena cava of anesthetized mongrel dogs with thrombin and a special double-balloon catheter; 2 hours later, the thrombus was embolized. In one group of dogs, activated type 1 plasminogen activator inhibitor (PAI-1) (130 μg) was delivered directly into the forming thrombus; in another, TXA (110 mg/kg) was given intravenously before thrombus formation; in controls, thrombus was induced without inhibitors. Cross-linked fibrin degradation product (D-dimer) appeared in the blood of control animals within 1 hour of thrombus induction (176 ± 62.5 versus 1.02 ± 0.39 ng/mL baseline; mean ± SEM), was maximal by 4 hours (413 ± 110 ng/mL) and remained elevated at 24 hours (90.8 ± 19.5 ng/mL). Compared with controls, PAI- 1 and TXA suppressed D-dimer release by 80% and 85%, respectively, over the first 24 hours. One week later, animals were killed, and residual emboli were harvested. Perfusion scan defects persisted in all animals at this time, but there were no scan defect differences among groups. However, emboli recovered from animals receiving PAI-1 still harbored immunoreactive PAI-1 and were, on average, more than twofold greater in mass (393 ± 56 mg) than emboli recovered from either controls (183 ± 76 mg) or animals receiving TXA (180 ± 80 mg).ConclusionsIntravenous TXA and intrathrombus PAI-1 effectively suppress thrombolysis for 24 hours in canines. Thromboemboli enriched with PAI-1 appear to resist lysis for longer periods of time (up to 1 week). These findings are consistent with the hypothesis that PAI-1 remains associated with the embolus, where it continues to inhibit lysis, whereas TXA eventually diffuses out of the embolus, allowing lysis to ensue.
ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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63. |
Survival and Predictors of Survival in Patients With Congestive Heart Failure Due to Chagas' Cardiomyopathy |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3098-3102
Charles Mady,
Rita Cardoso,
Antonio Barretto,
Protásio da Luz,
Giovanni Bellotti,
Fulvio Pileggi,
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摘要:
BackgroundThe fundamental determinant of the natural history of Chagas' disease is cardiac involvement.Methods and ResultsWe studied 104 male patients with congestive heart failure due to Chagas' disease to estimate the survival distribution function and to evaluate age, functional class (FC), maximal oxygen consumption (&OV0622;O2max), and ejection fraction (EF) as predictors of survival. Statistical evaluation was performed through univariate (Student's t test and χ2test) and multivariate analyses (Cox's regression model). Overall survival was 66% at 1 year, 56% at 3 years, and 48% at 5 years. Ages were not statistically different (P= .9811) between survivor (40.3 ± 8.7) and nonsurvivor (40.3 ± 9.4) groups. The ejection fraction(s) were statistically different (P= .0001) between survival (43.6 ± 9.9) and nonsurvival (30.6 ± 8.1) groups, as was &OV0622;O2max (P= .0001) (21.0 ± 4.7 and 15.0 ± 4.9, respectively). Most of the surviving patients were in FC II and most of the nonsurvivors were in FC IV (P= .0001). &OV0622;O2max (P= .0001) and EF (P= .0008) are highly associated with survival time in the multivariate analysis, but FC (P= .0578) is less important. Age (P= .9811) did not influence survival.ConclusionsWe conclude that 50% of the patients with heart failure due to Chagas' disease die in 47 months and that &OV0622;O2max and EF are important indices of survival in this group.
ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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64. |
Value of Physical Signs in the Diagnosis of Ventricular Tachycardia |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3103-3107
Clifford Garratt,
Michael Griffith,
Glenn Young,
Nicholas Curzen,
Stephen Brecker,
Anthony Rickards,
A. Camm,
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摘要:
BackgroundAlthough the use of physical signs for the diagnosis of ventricular tachycardia (VT) was described in the early 1900s, their value in this role has never been systematically assessed.Methods and ResultsUsing a blinded, randomized protocol, we examined the ability of 26 clinicians to detect ventriculoatrial (VA) dissociation during cardiac pacing in 21 patients with both atrial and ventricular pacing wires in situ after successful ablation of accessory pathways. In protocol 1 (10 patients), pacing was randomized to either ventricular pacing alone (simulating VT) or to atrioventricular sequential pacing (simulating supraventricular tachycardia or VT with intact VA conduction) at rates of 150 or 180 beats per minute. Each patients was examined by four clinicians blinded to the pacing mode. Clinicians were asked to make a diagnosis of “VA association” or “VA dissociation” after examining the patient for variability of the arterial pulse, jugular venous pulse (JVP), and first heart sound. In protocol 2 (11 patients), randomization of pacing mode was performed between examination of each of the three physical signs so that the value of each sign was assessed individually. In protocol 1, a diagnosis of VA dissociation (VT) was made in 21 of 40 observations, with a specificity of 75%, sensitivity of 70%, and a positive predictive value (PPV) of 71%. In protocol 2, from a total of 132 observations (44 for each sign), the sensitivity, specificity, and PPV for a diagnosis of VT were as follows: arterial pulse, 61%, 71%, 70%; JVP, 96%, 75%, 82%; and first heart sound, 58%, 100%, 100%.ConclusionsIt is concluded that, in patients with a regular tachycardia of uncertain origin, clinically detectable variations in the first heart sound and JVP are highly specific and sensitive indicators, respectively, of a diagnosis of VT. Assessment of the arterial pulse is of little value in this role.
ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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65. |
Decompensated DiabetesNew Features of an Old Problem |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3108-3112
Victor Lavis,
Denzil D'Souza,
Steven Brown,
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ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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66. |
Cardiac Rhabdomyomas in Tuberous Sclerosis (Bourneville's Disease) |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3113-3114
Humberto Guerrero G.,
Pablo Campos M.,
Carlos Harrison G.,
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ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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67. |
The Prognostic Significance of Nonsustained Ventricular Tachycardia in Hypertrophic Cardiomyopathy |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3115-3117
William McKenna,
Nicolas Sadoul,
Alistair Slade,
Richard Saumarez,
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ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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68. |
The French ParadoxVegetables or Wine |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3118-3119
Sabine Artaud-Wild,
Sonja Connor,
Gary Sexton,
William Connor,
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ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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69. |
Effects of Combined Supplementation With Antioxidants on Low‐Density Lipoprotein Oxidation |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3119-3120
I. Jialal,
S. Grundy,
B. Huet,
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ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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70. |
Effects of Combined Supplementation With Antioxidants on Low‐Density Lipoprotein Oxidation |
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Circulation,
Volume 90,
Issue 6,
1994,
Page 3120-3121
Ian Black,
Diane Fatkin,
Kiran Sagar,
Bijoy Khandheria,
Dominic Leung,
James Galloway,
Michael Feneley,
Warren Walsh,
Richard Grimm,
Claudia Stollberger,
Patrick Verhorst,
Allan Klein,
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ISSN:0009-7322
出版商:OVID
年代:1994
数据来源: OVID
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