ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Myocardial ischemia has, for many decades, been viewed as an all‐or‐none process that causes myocardial necrosis when prolonged and severe, but whose effects are transient when it is brief or mild. In view of the evidence that the ischemic process may "hit, run and stun," perhaps our thinking about the consequences of myocardial ischemia should be expanded. According to this formulation, an ischemic insult not of sufficient severity or duration to produce myocardial necrosis may acutely affect myocardial repolarization and cause angina (hit); but these changes wane rapidly (run), when the balance between myocardial oxygen supply and demand has been reestablished. However, the ischemia may interfere with normal myocardial function, biochemical processes and ultrastructure for prolonged periods (stun). The severity and duration of these postischemic changes depend on the length and intensity of the ischemia, as well as on the condition of the myocardium at the onset of the ischemic episode. Furthermore, it is likely that when the myocardium is repeatedly stunned, it may exhibit chronic postischemic left ventricular dysfunction, an ill-defined condition. If prolonged, chronic postischemic left ventricular dysfunction can progress to myocardial scarring and ischemic cardiomyopathy, it may be important to determine how often it can be ameliorated by permanent improvement of myocardial perfusion by surgical treatment.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We investigated the effects of brief intermittent periods of ischemia on myocardial viability. Brief periodic coronary occlusions were produced up to 18 times by inflating and deflating the balloon of an intracoronary #2F catheter for periods of 15, 10 or 5 minutes, followed by 15‐minuteperiods of reperfusion.Creatine kinase (CK) release, triphenyl tetrazolium chloride staining, and light and electron microscopy were used to detect the presence of myocardial necrosis. For the study of CK release, blood was taken from the great cardiac vein and the aorta before and at 5-minute intervals during each left anterior descending coronary occlusion, as well as during and 1, 5, 10 and 15 minutes after balloon deflation. In seven of 24 dogs with 15-minute occlusions, in five of 21 dogs with 10-minute occlusions, and in three of 32 dogs with 5-minute occlusions, small but distinct areas of subendocardial necrosis were present. In all dogs with morphologic proof of necrosis, there was periodic release of CK into the great cardiac vein, which peaked immediately after reperfusion, reflecting CK washout. Thus, brief periods of ischenia, which when single do not cause necrosis, have a cumulative effect and may cause myocardial necrosis. This mechanism of necrosis may be relevant clinically in patients with frequent anginal episodes. Since many dogs of this study did not have any myocardial necrosis, the findings also suggest that intermittent repefdusion has a beneficial effect and may prevent necrosis, even when total occlusion time exceeds 200 minutes.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Regional myocardial function and blood flow in endocardial layers were correlated in myocardial segments subtending severely ischemic and adjacent, normally perfused myocardium in conscious dogs 1‐3 weeks after recovery from coronary artery occlusion. With coronary artery occlusion induced by a hydraulic occluder, endocardial blood flow (measured with radioactive microspheres) and function (determined with an ultrasonic dimension gauge) in homogeneously nonischemic segments increased slightly but not significantly. In homogeneously ischemic segments, blood flow and function decreased (p < 0.01) by 96 1% and 98 ± 4%, respectively. In segments subtending zones of unequal perfusion, endocardial blood flow increased nonsignificantly in the myocardium surrounding the nonischemic crystal, while decreasing by 93 ± 2% (p < 0.01) in myocardium surrounding the ischemic crystal. Surprisingly, these segments behaved like homogeneously ischemic segments, i.e., endocardial shortening decreased by 92 ± 6% (p < 0.01). Thus, the failure to detect shortening despite normal perfusion of the myocardium surrounding one of the transducers suggests a potential problem with interpretation of regional function measurements or an inability of the apparently nonischemic myocardium to contract.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Left ventricular (LV) diastolic filling is abnormal at rest in many patients with coronary artery disease (CAD), even in the presence of normal resting LV systolic function. To determine the effects of improved myocardial perfusion on impaired LV diastolic filling, we studied 25 patients with one‐vessel CAD by high‐temporal‐resolution radionuclide angiography before and after percutaneous transluminal coronary angioplasty (PICA). No patient had ECG evidence of previous myocardial infarction. Despite normal regional and global LV systolic function at rest in all patients, LV diastolic filling was abnormal (peak LV filling rate [PFR] < 2.5 end-diastolic volumes (EDV)/sec or time to PFR > 180 msec) in 17 of 25 patients. Twenty-three patients had abnormal LV systolic function during exercise. After successful PTCA, LV ejection fraction and heart rate at rest were unchanged, but LV ejection fraction during exercise increased, from 52 8% (± SD) to 63 ± 5% (p< 0.001). LV diastolic filling at rest improved: PFR increased from 2.3 0.6 to 2.8 ± 0.5 EDV/sec (p< 0.001) and time to PFR decreased from 181 ± 22 to 160 ± 18 msec (p< 0.001). Thus, a reduction in exercise‐induced LV systolic dysfunction after PTCA, reflecting a reduction in reversible ischemia, was associated with improved LV diastolic filling at rest. These data suggest that in many CAD patients with normal resting LV systolic function and without previous infarction, abnormalities of resting LV diastolic filling are not fixed, but appear to be reversible manifestations of impaired coronary flow.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

To investigate the accuracy of the 12‐lead ECG in localizing the site of coronary artery narrowings, we reviewed abnormal ECGs obtained during myocardial infarction, spontaneous angina or exercise stress testing in 134 patients with angiographically documented one‐vessel disease. The presence of Q waves, ST‐segment elevation and T‐wave inversion in leads I, aVL and V1‐V4 were all highly correlated with the presence of left anterior descending coronary artery disease (p < 0.001), and the same ECG findings in leads II, III and aVF were associated with right (RCA) or circumflex coronary artery (LCx) narrowings (p < 0.001). In contrast, ST depression alone was not useful in predicting the site of coronary artery narrowing. Q waves correctly identified the location of the coronary disease in 98% of cases, ST elevation in 91%, T-wave inversion in 84%, and ST depression in 60%. No electrocardiographic criteria distinguished RCA from LCx disease, even in patients with a right-dominant circulation. These findings should lead to a better understanding of the value and limitations of the 12-lead ECG in localizing coronary artery disease.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The Coronary Drug Project was a randomized, placebo‐controlled trial of lipid‐influencing drugs in men who had recovered from one or more documented myocardial infarctions. Determinations of high‐density lipoprotein (HDL) cholesterol were made at baseline in a group of 354 men randomized to the placebo group. Five‐year mortality was highest (33.0%) in men with baseline serum HDL cholesterol levels of less than 35 mg/dl; it was 15.9%, 17.7%, and 21.8% in men with levels of 35‐39, 40-44, and 45 mg/dl, respectively (for the linear inverse relationship between HDL cholesterol and 5-year mortality, p = 0.029). Adjustment for 40 baseline variables had minimal effect this relationship (p 0.042).

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Long‐term treatment with timolol in patients ages 65‐75 years who survived myocardial infarction was related to a significant reduction, compared with placebo, in overall mortality (p < 0.05), total cardiac death (p < 0.01), sudden death (p < 0.05) and reinfarction (p < 0.01). The analyses were based on 732 patients (384 taking placebo and 348 timolol) from a cohort of 1884 patients in the Norwegian multicenter timolol study. The dosage of timolol was 10 mg twice daily and the patients were followed for 12‐33 months (mean 17 months). There were 83 deaths in the placebo group and 52 deaths in the timolol group, a reduction of 35.5%. There were 69 initial reinfarctions in the placebo group and 38 in the timolol group, a reduction of 39.2%. There was no difference in the reduction of mortality and reinfarction between patients 65‐75 years of age and patients less than 65 years of age. The incidence of side effects, the number of withdrawals and the reasons for withdrawal were similar in older and younger patients. We conclude that age should not be a decision-making factor concerning timolol therapy in postinfarct patients.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The effects of perioperative myocardial infarction (MI) on long‐term survival and symptomatic status after coronary bypass surgery was assessed by a 64.9‐month follow‐up of the survivors (225) all isolated coronary bypass surgery (227) performed at our institution from November 1975 to July 1976. Patients were separated into three groups: group 1 (111 patients) showed no postoperative ECG changes; group 2 (31 patients) showed appearance and persistence of new or enlarged Q waves with localized ST elevation; and group 3 (83 patients) showed less specific ECG changes. Group 2 had greater technetium pyrophosphate scan positivity (eight of 19 vs one of 35, p < 0.0005) and higher peak MB‐CK activity (83 20 vs 20 ± 3 IU/I (mean ± SEM) (p < 0.01) than group 1. Using the ECG criteria of group 2, the incidence perioperative MI was 13.7% (31 of 227 patients). Groups 1 and 2, compared according to age, prior infarction, number of diseased vessels, left main stenosis, coronary collaterals, left ventricular ejection fraction and number of grafts inserted, were not significantly different. However, both ischemic (aortic cross-clamp) time and total pump time were greater in group 2 than in group 1 (65 ± 3 vs 51 2 minutes and 166 ± 7 vs 132 ± 3 minutes, respectively, p 0.05). There were no perioperative (30-day) deaths in group 1, whereas group 2 had a perioperative mortality rate of 3.2% (one of 31). The 5-year survival rates of group 1 (94.3%), group 2 (96.8%) and group 3 (91.1 %) were not significantly different. Late postoperative status regarding relief of angina, dyspnea, level physical activity, and use of cardiac medications were not different between the groups. In all patients and in those age 55 years or younger, work status was not different. Although perioperative MI may be associated with a higher operative mortality, late survival and cardiac status were not affected by it in 5 years of follow-up.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The responsiveness of ventricular tachycardia (VT) to propafenone, a new antiarrhythmic agent, was evaluated in the conscious dog during acute myocardial infarction (AMI). AMI was produced in the anesthetized closed‐chest dogs with an intracoronary catheter system by permanent occlusion in eight dogs and by 2‐hour occlusion followed by reperfusion of the left anterior descending coronary artery in eight others. Twenty‐four hours after surgery, all dogs in both groups had VTwith similar characteristics (rates of 130‐220 beats/min) in the conscious, nonsedated state. Administration of propafenone, 4 mg/kg i.v. over 2 minutes, immediately and completely suppressed VT in seven of the permanently occluded and in all eight dogs in the reperfused group. The duration of propafenone-induced normal sinus rhythm (NSR) was inversely related to the rate of VT. Intravenous infusion of propafenone, 0.2 mg/kg/min, after a 4-mg/kg i.v. bolus maintained NSR for the duration of infusion. Propafenone did not change the mean blood pressure. Lidocaine, as much as 5 mg/kg i.v., was ineffective when the VT rate was greater than 160 beats/min and restored NSR only transiently (3-6 minutes) when the VT rate was less than 160 beats/min in either group (p < 0.001 compared with propafenone). Propafenone, unlike lidocaine, significantly (p < 0.05) increased both cathodal and bipolar diastolic excitability threshold and shifted upward the tail portion of the strength-interval relation of the right ventricle. Propafenone had no effect on the effective refractory period of the right ventricle. Plasma propafenone levels during propafenone-induced NSR and myocardial excitability measurements were 3.2 1.6 gg/ml in the reperfused group and 3.0 1.68, tg/ml in the permanently occluded group (mean ± SD) (p > 0.1). We conclude that propafenone is very effective against VTduring AMI in the dog, and it may be effective in lidocaine-resistant VT during acute ischemia.

ISSN:0009-7322    

出版商:OVID    

年代:1982

数据来源: OVID