ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

AbstractSeven conscious dogs documented to be at high risk by the occurrence of ventricular fibrillation (VF) during acute myocardial ischemia were randomly assigned to 6 weeks of either daily exercise training or cage rest followed by exercise training. After 6 weeks of daily treadmill training, heart rate variability, a marker of vagal tone, increased by 74% (P< .001); baroreflex sensitivity, a marker of the capability to reflexly augnent vagal activity, increased by 69% (P< .01); the repetitive extrasystole threshold, a marker of ventricular electrical stability, increased by 44% (P< .05). After exercise training, the incidence of ventricular fibrillation during acute myocardial ischemia decreased by 100%, as all animals survived. Neither passage of time nor heart rate level during ischemia contributed to the outcome. The most likely mechanism to explain the striking change in risk status is the shift in autonomic balance characterized by increased cardiac vagal activity, which was previously shown to have an antifibrillatory effect. These results suggest that exercise training in healthy individuals may decrease their likelihood of developing lethal arrhythmias during acute myocardial ischemia.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundSubjects in sinus rhythm have two distinct diastolic flow velocities in the left ventricular (LV) outflow tract directed toward the aortic valve. These follow E and A waves of the transmitral flow and are referred to as Er and Ar waves, respectively. The A wave transit time from the mitral valve to the LV outflow tract is shorter than that of the E wave and is shorter in those with LV hypertrophy and the aged, suggesting its possible dependence on LV late diastolic stiffness.Methods and ResultsWe measured the peak-to-peak and onset-to-onset A wave transit times from the mitral valve to the LV outflow tract (AArpand AAr, intervals, respectively) using Doppler echocardiography in 20 patients undergoing left heart catheterization for evaluation of coronary artery disease. These intervals were correlated with indices of LV late diastolic stiffness obtained from high-fidelity LV pressure tracings and angiographic volume assessments. The AArp and AAr. intervals correlated significantly with LV Dp/DV (conventionally dP/dV) (r= − .68 and − .83, respectively), volume stiffness, V Dp/DV (r= − .74 and − .80, respectively) and LV (V/P) (Dp/DV) (r= − .69 and − .74, respectively). The AAr. interval correlated better with the square roots of LV Dp/DV and volume stiffness (r= − .86 and − .87, respectively).ConclusionsWe conclude that AArp and AAr. intervals are easily obtainable Doppler parameters that reflect LV late diastolic stiffness in natients with coronary artery disease and possibly in other patient groups.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe heart has been demonstrated not only to be a pumping organ but also an endocrine organ secreting atrial natriuretic peptide (ANP). We hypothesized that myocardial ischemia may affect ANP secretion and that reperfusion therapy for acute myocardial infarction can preserve endocrine function of the heart.Methods and ResultsTwenty patients with acute right ventricular infarction were examined who underwent reperfusion therapy on admission. These patients had proximal occlusion of the dominant right coronary artery involving the right atrial branches: 9 patients with successful reperfusion (SRP group) and the remaining 11 patients with unsuccessful reperfusion URP group). Within 24 hours after the onset of infarction, a volume loading test was performed after reperfusion therapy with measurements for plasma ANP levels and hemodynamics. Before the volume loading test, the plasma ANP level and mean right atrial pressure were similar between these two groups. However, in the URP group, percent increase in ANP in response to volume loading was strikingly smaller (URP, 45±18% versus SRP, 133±25%;P< .01) despite similar percent increase in mean right atrial pressure (URP, 100±46% versus SRP, 86±23%). The peak ANP level occurred significantly later in the URP group (69±16 hours) than in the SRP group (28±9 hours,P< .001) after the onset of infarction.ConclusionsThe response of ANP release to volume loading is attenuated in patients with right ventricular infarction without coronary reperfusion. However, successful reperfusion induces a rapid recovery of cardiac endocrine function as well as its mechanical function. A sufficiently elevated plasma ANP level may be a useful predictor of hemodynamic improvement in patients with right ventricular infarction.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundBecause genetic factors are believed to contribute to the etiology of coronary artery disease (CAD), it has been suggested that DNA polymorphisms at candidate loci might identify individuals at high risk for developing disease. In this regard, apolipoprotein genes represent extremely promising loci because levels of apolipoproteins and their associated lipoproteins represent a major risk factor for CAD, and rare dysfunctional mutations in these genes result in a significant risk for CAD. To date, although some reports indicate that DNA polymorphisms at these loci are associated with increased risk of CAD, other reports have failed to find such associations.Methods and ResultsTo resolve the question of whether genetic polymorphisms at apolipoprotein loci can be used to identify individuals at increased risk for CAD, we evaluated the distribution of apolipoprotein genetic polymorphisms in a large series of subjects (n=848) undergoing coronary angiography. Blinded assessment of angiograms was used to discriminate between patients with CAD (≥60% stenosis of any major branch, n=444) and control subjects without disease (<10% stenosis, n=404). A total of 12 polymorphisms were evaluated at the following loci: apolipoprotein (apo) A-I/C-III/A-IV (five restriction site polymorphisms–MspI,PstI,SstI,PvuIla,PvuIb), apo B (three restriction site polymorphisms–XbaI,EcoRI,MspI, plus an insertion/deletion polymorphism), apo A-II (MspI polymorphism), apo C-II (TaqI polymorphism), and apo E (protein isoforms revealed by DNA analysis). All subjects were of Northern European (primarily Angloscandinavian) descent, and, within each sex, patients and control subjects were of comparable age. All 12 loci were in Hardy- Weinberg equilibrium, with no indication of population heterogeneity. As expected, patients were distinguished from control subjects by their lipid profiles and a higher frequency of known risk factors for CAD. However, analysis by log-linear models indicated that there were no significant associations between apolipoprotein polymorphisms and the risk of CAD (P= .10 to .90). The lack of association was maintained irrespective of whether the analysis was carried out for the entire sample or the contrast was made more stringent by comparing patients most likely to have a genetic component to their disease (ie, young patients with early-onset CAD) with the control subjects least likely to have genetic susceptibility (ie, older control subjects who had ample time to develop CAD).ConclsionsDespite the fundamental role of apolipoprotein genes in lipid metabolism, we find no evidence that common genetic polymorphisms of the major apolipoprotein loci have a significant influence on the risk of developing angiographically defined CAD in this representative population. Therefore, at this time we find no support for the hypothesis that mass screening for genetic polymorphisms at candidate loci can reduce the burden of CAD by identifying a substantial proportion of high-risk individuals. Instead, it appears more appropriate to direct attention toward modifying high-risk behaviors to alleviate the consequences of traditional environmental risk factors.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background99mTc-sestamibi and thallium imaging have similar accuracy when used for diagnostic purposes, but whether sestamibi provides accurate information regarding myocardial viability in patients with chronic coronary artery disease has not been established. Since there is minimal redistribution of sestamibi over time, it may overestimate nonviable myocardium in patients with left ventricular dysfunction, in whom blood flow may be reduced at rest.Methods and ResultsWe studied 54 patients with chronic coronary artery disease with a mean ejection fraction of 34±14%. Patients underwent stress/redistribution/reinjection thallium tomography and, within a mean of 5 days, same-day rest/stress sestamibi imaging using the same exercise protocol and with patients achieving the same exercise duration. Of the 111 reversible thallium defects on either the redistribution or reinjection study, 40 (36%) were determined to be irreversible on the rest/stress sestamibi study, whereas only 3 of 63 irreversible thallium defects despite reinjection (5%) were classified to be reversible by sestamibi imaging. The concordance regarding reversibility of myocardial defects between thallium stress/redistribution/reinjection and same day rest/ stress sestamibi studies was 75%. A subgroup of 25 patients also underwent positron emission tomography (PET) studies with15O-labeled water and [18F]fluorodeoxyglucose (FDG) at rest after an oral glucose load. As in the overall group of 54 patients, there was concordance between thallium and sestamibi imaging regarding defect reversibility in 51 of 73 regions (70%). In the remaining 22 discordant regions (30%), 18 (82%) appeared irreversible by sestamibi imaging but were reversible by thallium imaging. Myocardial viability was confirmed in 17 of 18 regions, as evidenced by normal FDG uptake (10 regions) or FDG/blood flow mismatch (7 regions) on PET. These regions were present in 16 of the 25 patients studied (64%). We then explored methods to improve the sestamibi results. First, when the 18 discordant regions with irreversible sestamibi defects were further analyzed according to the severity of defects, 14 (78%) demonstrated only mild-tomoderate reduction in sestamibi activity (51% to 85% of normal activity), suggestive of predominantly viable myocardium, and the overall concordance between thallium and sestamibi studies increased to 93%. Second, when an additional 4-hour redistribution image was acquired in 18 patients after the injection of sestamibi at rest, 6 of 16 discordant irreversible regions (38%) on the rest/stress sestamibi study became reversible, thereby increasing the concordance between thallium and sestamibi studies to 82%.ConclusionsThese data indicate that same-day rest/stress sestamibi imaging will incorrectly identify 36% of myocardial regions as being irreversibly impaired and nonviable compared with both thallium redistribution/reinjection and PET. However, the identification of reversible and viable myocardium can be greatly enhanced with sestamibi if an additional redistribution image is acquired after the rest sestamibi injection or if the severity of reduction in sestamibi activity within irreversible defects is considered.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundAspirin, by nonselectively blocking cyclooxygenase both in platelets and in endothelial cells, not only inhibits the thromboxane A2pathway of platelet activation but at the same time also the generation of vasodilating and platelet-inhibitory prostanoids, such as prostacyclin, by the endothelial cells. Ridogrel, by inhibiting thromboxane A2synthase and blocking the thromboxane A2/prostaglandin endoperoxide receptors, is a more potent antiplatelet agent than aspirin and might offer an advantage over aspirin as an adjunct to thrombolysis. This study was performed to compare the efficacy and safety of ridogrel with that of aspirin as conjunctive therapy for thrombolysis in patients with acute myocardial infarction.Methods and ResultsA total of 907 patients with acute myocardial infarction were randomized between aspirin and ridogrel given in addition to streptokinase (1.5 MU over a period of 1 hour). The primary end point was coronary patency (TIMI flow grades 2 and 3) at predischarge angiography to be performed between 7 and 14 days after admission. A patent infarct-related vessel was found in similar proportions of patients in the two treatment groups: 72.2% in the ridogrel and 75.5% in the aspirin group. The presence of clinical markers of reperfusion at 2 hours and the incidence of major clinical events during hospital stay were also similar in both groups. However, in a post hoc analysis, a lower incidence of new ischemic events (reinfarction, recurrent angina, ischemic stroke) was observed with ridogrel: 13% versus 19% in the aspirin group (a 32% reduction;P< .025). No excess of serious bleeding complications, including hemorrhagic stroke, was found.ConclusionsRidogrel is not superior to aspirin in enhancing the fibrinolytic efficacy of streptokinase but might be more effective in preventing new ischemic events.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundPatients with unstable angina despite intensive medical therapy, ie, refractory angina, are at high risk for developing thrombotic complications: myocardial infarction or coronary occlusion during percutaneous transluminal coronary angioplasty (PTCA). Chimeric 7E3 (c7E3) Fab is an antibody fragment that blocks the platelet glycoprotein (GP) Ib/IIIa receptor and potently inhibits platelet aggregation.Methods and ResultsTo evaluate whether potent platelet inhibition could reduce these complications, 60 patients with dynamic ST-T changes and recurrent pain despite intensive medical therapy were randomized toc7E3 Fab or placebo. After initial angiography had demonstrated a culprit lesion suitable for PTCA, placebo orc7E3 Fab was administered as 0.25 mg/kg bolus injection followed by 10 μg/min for 18 to 24 hours until 1 hour after completion of second angiography and PTCA. During study drug infusion, ischemia occurred in 9c7E3 Fab and 16 placebo patients (P= .06). During hospital stay, 12 major events occurred in 7 placebo patients (23%), including 1 death, 4 infarcts, and 7 urgent interventions. In thec7E3 Fab group, only 1 event (an infarct) occurred (3%,P= .03). Angiography showed improved TIMI flow in 4 placebo and 6c7E3 Fab patients and worsening of flow in 3 placebo patients but in none of thec7E3 Fab patients. Quantitative analysis showed significant improvement of the lesion in the patients treated with c7E3 Fab, which was not observed in the placebo group, although the difference between the two treatment groups was not significant. Measurement of platelet function and bleeding time demonstrated >90% blockade of GPIIb/IIIa receptors, >90% reduction of ex vivo platelet aggregation to ADP, and a significantly prolonged bleeding time during c7E3 Fab infusion, without excess bleeding.ConclusionsCombined therapy withc7E3 Fab, heparin, and aspirin appears safe. These pilot study results support the concept that effective blockade of the platelet GPIIb/IIIa receptors can reduce myocardial infarction and facilitate PTCA in patients with refractory unstable angina.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID