摘要:

Nuclear magnetic resonance (NMR) is used to generate cross-sectional images of the human body that show excellent anatomic and functional definition. The NMR imaging process involves interactions between electromagnetic fields and the hydrogen nuclei being imaged. These interactions occur on time scales of milliseconds to seconds. Consequently, the motion of these nuclei, for instance, when carried by blood, produces distinct signatures that are used to assess flow in major vessels. Myocardial dyskinesis also produces visible effects. Because of these effects, NMR imaging may be a safe and effective tool in the diagnosis and assessment of cardiovascular disease.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

We studied regional blood flow (QR) using radiolabeled microspheres and measured hemodynamic variables in 20 anesthetized dogs in normal sinus rhythm and during ventricular fibrillation treated with cardiopulmonary resuscitation (CPR). Nonsimultaneous compression and ventilation CPR (NSCV-CPR) was performed in seven dogs with a pneumatic piston that gave 50 chest compressions/min with an open airway with 10 ventilations at an airway pressure of 33 mm Hg interposed between each fifth and sixth compression. Simultaneous compression and ventilation (SCV-CPR) was performed in seven dogs with the piston and in six other dogs with a circumferential pneumatic vest. Both devices gave 30 compressions/min simultaneously with 30 ventilations that elevated airway pressure to 80 mm Hg. The abdomen was bound during SCV-CPR. Regional blood flow (mean SD) to the cerebral hemispheres, cardiac ventricles, and kidneys, expressed as ml/min/100 g tissue, was 3.1 + 4.0, 3.4 3.3 and 1.5 1.5, respectively, during NSCV-CPR; 11.5 + 5.9, 4.9 4.7 and 2.7 2.7 during SCV-CPR (vest); and 16.2 + 7.2, 11.0 4.0 and 20.1 20.2 during SCV-CPR (piston) (all p < 0.05 compared with NSCV-CPR). These results indicate that QR to all organs studied is reduced below normal sinus rhythm levels during CPR for ventricular fibrillation, QR to the brain is proportionately greater than QR to the heart and kidneys, and QR to the brain is greater with both forms of SCV-CPR than with NSCV-CPR.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Recent studies have demonstrated that for the same chest compression force during mechanical cardiopulmonary resuscitation (CPR), the carotid artery-to-jugular vein pressure gradient and carotid blood flow are increased when the phasic rise of intrathoracic pressure is enhanced by abdominal binding and simultaneous ventilation at high airway pressure with each chest compression (SCV). The objective of the present study was to assess whether cerebral blood flow is also enhanced, since it is known that fluctuations in intrathoracic pressure are transmitted to the intracranial space and affect intracranial pressure (ICP). In two series of pentobarbital-anesthetized dogs, one of two CPR techniques was initiated immediately after inducing ventricular fibrillation. Brain blood flow was measured by the radiolabeled microsphere technique immediately before cardiac arrest and at 1 and 3 minutes after commencing CPR. Evidence of adequate mixing of spheres and lack of sedimentation under these low-flow conditions was verified by correlation with brain venous outflow, comparison of the arterial concentration-time profile of spheres and a nonsedimentary marker (thallium-201 in solution), and use of multiple arterial sampling sites. During SCV CPR with abdominal binding, mean carotid artery pressure (60 ± 3 mm Hg) was higher than that during conventional CPR (25 ± 2 mm Hg). Pulsations of ICP occurred that were in phase with chest compression and greater than jugular venous pressure. Mean ICP was higher during SCV (46 ± 2 mm Hg) than conventional CPR (20 ± 2 mm Hg). However, the net brain perfusion pressure gradient (carotid artery pressure -ICP) was greater with SCV (14 ± 3 mm Hg) than with conventional CPR (5 0.4 mm Hg). Cerebral blood flow was significantly greater during SCV CPR (32 ± 7% of prearrest cerebral flow) than during conventional CPR (3 ± 2%). We conclude that SCV CPR combined with abdominal binding substantially improved brain perfusion by enhancing cerebral perfusion pressure in this experimental model.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A prospective, randomized study of i.v. nitroglycerin (TNG) in the management of repetitive spontaneous angina pectoris was undertaken in 40 consecutive patients. The clinical effectiveness of i.v. TNG (group A) was compared with that of oral isosorbide dinitrate (ISDN) and topical 2% nitroglycerin ointment (NO) in combination (group B) during a 72-hour treatment period. The doses of both nitrate regimens were adjusted so that the mean arterial pressure in the two groups was reduced by 15 ± 3% of control values to the same level (77 mm Hg). The i.v. TNG dose of 10–200, gg/min yielded arterial plasma TNG levels of 1.2–65.3 ng/m] and estimated plasma (arterial) clearance of 106 ± 55 ml/min/kg of body weight (mean ± SD). In group B, the doses were 20–60 mg (oral ISDN) and 1/2-2 inches (NO) every 6 hours. Intravenous TNG reduced the number of spontaneous ischemic episodes from 3.3 ± 0.8 per 24 hours during the control period to 1.0 ± 0.3 per 24 hours during the treatment period (p < 0.01), while the ISDN/NO combination reduced the number of episodes from 3.1 ± 0.4 to 1.4 ± 0.3 (p < 0.01). Overall, the magnitude of the therapeutic effect of i.v. TNG was statistically indistinguishable from that of ISDN/NO, although i.v. TNG did have somewhat greater clinical benefit on day 2 of the 3-day treatment period. Furthermore, the data suggested more consistent control of ischemic episodes with i.v. TNG during the first 24 hours of the trial. Although both regimens markedly reduced the frequency of spontaneous ischemic episodes, only 36% of patients in group A and 17% in group B experienced no ischemic episodes during the study period (NS). Forty-three percent of patients in group A and 61% in group B (NS) required early coronary artery bypass surgery to control recurrent ischemic episodes refractory to medical therapy. We conclude that i.v. TNG and ISDN/NO, when administered in doses adjusted to produce similar effects on systemic arterial pressure, have nearly equivalent clinical effects in the management of patients with frequent episodes of spontaneous angina pectoris. Intravenous TNG offers the advantage of more consistent control of ischemic episodes during the first 24 hours of treatment. Nevertheless, the recurrence rate of spontaneous ischemic episodes during medical therapy is high with both regimens, and early coronary artery bypass surgery may be required for long-term management.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

We analyzed the clinical outcomes in 688 patients with isolated stenosis of one major coronary artery. The survival rate among patients with disease of the right coronary artery (RCA) was higher than that among patients with left anterior descending (LAD) or left circumflex coronary artery (LCA) disease. The survival rate among patients in all three anatomic subgroups exceeded 90% at 5 years. The presence of a lesion proximal to the first septal perforator of the LAD was associated with decreased survival compared with the presence of a more distal lesion. For the entire group of one-vessel disease patients, total ischemic events (death and nonfatal infarction) occurred at similar rates regardless of the anatomic location of the lesion. Left ventricular ejection fraction was the baseline descriptor most strongly associated with survival, and the characteristics of the angina had the strongest relationship with nonfatal myocardial infarction. No differences in survival or total cardiac event rates were found with surgical or nonsurgical therapy. The relief of angina was superior with surgical therapy, although the majority of nonsurgically treated patients had significant relief of angina. The survival rate of patients with one-vessel coronary disease is excellent, and the risk of nonfatal infarction is low. Clinical strategies for the care of these patients must consider the long-term clinical course of one-vessel coronary disease.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

To compare acute effects of nitroglycerin (0.8 mg sublingually), nifedipine (5 ng/kg/min i.v.) and metoprolol (0.15 mg/kg i.v.) on normal, ischemic and scarred myocardial segments in man, we performed simultaneous hemodynamic and radionuclide measurements of left ventricular function. Sixteen patients with isolated left anterior descending (LAD) disease were studied at rest and during exercise. Nine patients had angina and exercise-induced ischemia (LAD stenosis) and seven patients had previous transmural myocardial infarction and no ischemic changes during thallium imaging (LAD occlusion). The effects of the drugs on regional ejection fraction of the involved anteroseptal region and the normal posterolateral area were compared.Global ejection fraction at rest did not change after nitroglycerin, increased after nifedipine and decreased after metoprolol. In patients with ischemia, the exercise ejection fraction improved after all drugs due to increased regional ejection fraction in ischemic segments; i.e., a regional antiischemic effect evidenced by improved regional function could be demonstrated with all three agents. Regional ejection fraction increased from 35.8 ± 19.5% to 66.2 ± 15.2% (± SD) after nitroglycerin (p< 0.001), to 61.7 ± 8.7% after nifedipine (p< 0.001), and to 48.4 ± 7.0% after metoprolol (p< 0.01). In regions of myocardial scar, regional ejection fraction was not changed after any drug. In normal areas, regional ejection fraction remained unchanged after nitroglycerin and nifedipine, but decreased after metoprolol. Despite similar antiischemic effects of all three drugs, underlying hemodynamic mechanisms were quite different and may provide a rationale for combined forms of treatment. These results may help to select optimal drug combinations to improve myocardial performance in patients with chronic ischemic heart disease.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

There are few data on the long-term effects of new Q waves on survival and morbidity after coronary bypass graft surgery (CABG). We followed 1340 patients who underwent CABG in 1978 at 10 hospitals participating in the Coronary Artery Surgery Study (CASS). The incidence of perioperative Qwave infarction was 4.6% (range 0.0–10.3% by hospital). The rate of infarction was higher in patients who had an increased left ventricular end-diastolic pressure or cardiomegaly on the preoperative chest radiograph. Patients who received more grafts or who had longer cardiopulmonary bypass time were also at higher risk of infarction. In a stepwise discriminant analysis of 44 clinical, angiographic and surgical variables, cardiopulmonary bypass time, topical cardiac hypothermia and cardiomegaly entered the stepwise selection of variables.Long-term survival was adversely affected by the appearance of new postoperative Q waves. The hospital mortality was 9.7% in the 62 patients who had new postoperative Q waves and 1.0% in the 1278 patients who did not (p< 0.001); the 3-year cumulative survival rates were 85% and 95%, respectively (p< 0.001). In patients who survived to hospital discharge, the presence of new postoperative Q waves did not adversely affect 3-year survival (94% and 96%, respectively). The survival rates were worse in patients who had a history of infarction or who had impaired left ventricular function preoperatively. The number of readmissions to hospital after CABG among the patients who had a transmural perioperative infarction was similar to that among patients who did not.We conclude that the appearance of new Q waves after CABG adversely affects survival. The major impact on mortality occurs before hospital discharge. Patients who are destined to have a perioperative infarct cannot be predicted from commonly measured preoperative and angiographic variables.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Exercise, ergonovine and the cold pressor test have been used to provoke variant angina attacks. The sensitivity of these three tests was compared in 34 hospitalized patients with well documented, active variant angina who had recently undergone coronary arteriography. The three tests were usually perfornmed on three consecutive days, and 28 of the 34 had the three tests within 1 week. Angina was provoked by ergonovine in all 34 patients, by exercise in 17 and by the cold pressor test in only five (p < 0.00). ST eltion developed during the ergonovine test in 32 (94%), during exercise in 10 (29%) and durin the cold preor test in only three (9%). With ergonovine, one patient had only ST depression and owe had no ECG changes. During the cold pressor test two patients had pseudonormalization of abnormally negative T waves and 29 had no ECG changes. Exercise induced T-wave pseudonormalization in four patiets, ST dess in nine others and no ECG changes in 11. ST elevation was more frequent with ergonovine than with either of the other tests (p < 0.0001). ST elevation or T-wave pseudonormalization occurred more often with exercise than with cold (p < 0.05), but both occurred less often than with ergnovine (p < 0.0001).We conclude that the sensitivity of the ergonovine test is very high in patients with active variant angina and that exercise will provoke angina with ST elevation in about 30% of these cases. In contrast, the sensitivity of the cold pressor test is too low to be of much clinical value in the diagnosis of variant angina.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The left ventricular diastolic pressure-volume. relationship shifts upward during angina, but why this happens is not known. To assess regional myocardial stiffness, we studied 12 patients who. had coronary artery disease using simultaneous left ventricular micromanometer pressure recording and Mmode echocardiography before and during angina induced. by pacing tachycardia. All patients had two- or three-vessel coronary artery disease that involved the posterior left ventricular wall circulation and had positive pacing stress tests, i.e., development of angina and a postpacing rise in left ventricular end-diastolic pressure (15±3 to 31±6 mm Hg, p < 0.001). A marked upward shift in the relationship between the diastolic left ventricular pressure and the posterior wall thickness (h) occurred after pacing tachycardia, but the change in left ventricular posterior wall end-diastolic thickness was minimal (8.9±2.1 to 9.2±2.1 mm, NS). After pacing, the peak rate of left ventricular posterior wall thinning decreased (82±37 to 48±27 mm/sec, p < 0.005) and the time constant of relaxation derived from the best exponential fit to the isovolumic left ventricular pressure decay increased (49±5 to 58±7 msec,. p < 0.001). Diastolic active left ventricular pressure decay, extrapolated from the exponential fit, was subtracted from the measured left ventricular pressure (which is equal in magnitude but opposite in sign to the radial stress at the endocardium) to calculate residual left ventricular pressure (PR) and hence residual stress (6R = -PR). A radial stifiness modulus (ER) was determined by the slope of the PR VS log h plots before and after pacing. Over the same range of residual radial stress (aR), ER was always higher during pacing-induced angina, indicating increased residual myocardial stiffness. Increased myocardial stiffness in addition to a decreased rate of wall thinning and slow active pressure decay contribute to the upward shift in left ventricular pressure-wall thickness and pressure-volume relationships during pacing-induced angina.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Resting left ventricular (LV) function was evaluated in 22 patients with permanent ventricular pacemakers. LVejection fraction and volume indexes were determined by gated blood pool scintigraphy at ventricular pacing rates of 50–100 beats/min. In patients with a normal heart size, increases in pacing rates resulted in significant linear decreases in stroke volume index and ejection fraction. However, endsystolic volume index and cardiac index did not change. Patients with cardiomegaly appeared to respond differently. End-diastolic volume index decreased significantly as the pacing rate was increased from 50 to 100 beats/min. Ejection fraction was significantly reduced only at pacing rates of 90 and 100 beats/min. Mean cardiac index was highest at ventricular pacing rates of 70–90 beats/min. Increases in cardiac index, achieved by increasing the pacing rate, were maintained over a 4.3-month follow-up. Patients with underlying sinus rhythm had a 27% increase in cardiac output in association with an increase in ejection fraction from 55% to 62% when sinus rhythm was compared to ventricular pacing at a rate of 60 beats/min.These data suggest that patients with cardiomegaly have a narrow range of optimal pacing rates at rest.

ISSN:0009-7322    

出版商:OVID    

年代:1983

数据来源: OVID