摘要:

ABSTRACTWe evaluated the effects of selective activation of H, receptors on coronary hemodynamics in 16 patients divided into two groups: group A, 11 patients with atypical angina or valvular heart disease and normal coronary arteries, and group B, five patients with spontaneous angina, four of whom had significant (>70% stenosis) coronary artery disease and one with normal coronaries. Selective H, receptor stimulation was achieved by infusing 0.5,ug/kg/min of histamine intravenously for 5 min after pretreatment with cimetidine (25 mg/kg). Heart rate was maintained constant (100 beats/min) by coronary sinus pacing and coronary blood flow (CBF) was measured by thermodilution. In group A, during histamine infusion mean aortic pressure fell from 99 5 to 77 4 mm Hg (mean + SEM, p < .001), coronary vascular resistance (CVR) decreased from 1.07 0.17 to 0.82 + 0. 14 mm Hg/ml/min (p < .02), and CBF and myocardial oxygen consumption remained unchanged. None of the patients in this subgroup developed angina during histamine infusion. In group B, while no significant average changes in mean arterial pressure, CVR, or CBF were observed, two of the five patients (40%) developed angina during histamine infusion, accompanied by ST-T elevation, a decrease in CBF, and an increase in CVR. In one of these two patients circumflex coronary arterial spasm was angiographically demonstrated during histamine-induced angina. Our results suggest that stimulation of the H1 receptor induces a reduction of CVR, probably resulting from vasodilation of small coronary resistance vessels. In a considerable percentage of patients with vasospastic angina with or without coronary artery disease, however, H1 receptor-induced vasoconstriction of large capacitance coronary arteries may prevail over peripheral vasodilatation. These findings contribute to our understanding of the pathophysiologic effects of histamine on CBF in man and may have practical relevance in patients undergoing treatment with H2 receptor-blocking drugs.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTWe investigated the relationship between oxygen delivery (DO2), oxygen consumption (V02), and influence of oxyhemoglobin dissociation (P50) on VO2 in 40 patients with complicated myocardial infarction. A decrease in V02 and an increase in P50 were observed as DO2 decreased due to pump failure. In a given range of DO2, VO2 was related to P50 in survivors (r values .472 to .647, p < .01). Each millimeter of mercury increase in P50 was associated with a 5.2 to 6.5 ml/min m2 increase in VO2 when DO2 was less than 450 ml/min m2. No similar correlation was found for nonsurvivors. Lactate was higher in nonsurvivors despite the fact that DO2 and V02 were similar in the two groups. The lack of compensatory increases in P50 may be pathologic in nonsurvivors. However, the value of V02 as an indicator of tissue oxygenation or survival in patients with acute myocardial infarction is questionable.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTDespite having smaller infarct size and better left ventricular function, patients with non-Q wave myocardial infarction (NQMI) appear to have an unexpectedly high long-term mortality that is ultimately comparable to that of patients with Q-wave myocardial infarction (QMI). Patients with NQMI may lose their initial prognostic advantage because there is more viable tissue in the perfusion zone of the infarct-related vessel, rendering myocardium more prone to reinfarction. We tested this hypothesis in a prospective study of 241 consecutive patients 65 years of age or younger with acute uncomplicated myocardial infarction confirmed by creatine kinase levels (MB fraction). All patients received customary care and none underwent thrombolytic therapy or emergency angioplasty. Predischarge coronary angiography, radionuclide ventriculography, 24 hr Holter monitoring, and quantitative thallium-201 (201T1) scintigraphy during treadmill exercise were performed 10 + 3 days after infarction. Infarcts were designated as QMI (n = 154) or NQMI (n = 87) by accepted criteria applied to serial electrocardiograms obtained on days 1, 2, 3, and 10. The baseline Norris coronary prognostic index, angiographic jeopardy scores, and prevalence of Lown grade ventricular arrhythmias were similar between groups despite evidence for less necrosis with NQMI vs QMI, reflected by lower peak creatine kinase levels (520 vs 1334 IU/liter; p = .0001, 4 hr sampling), higher resting left ventricular ejection fraction (53% vs 46%; p = .0001), fewer akinetic or dyskinetic segments (1.2 vs 2.4; p = .0001), and fewer persistent 201TI defects in the infarct zone (0.9 vs 1.9; p = .0001). Patientswith NQMI also had more patent infarct-related vessels (54% vs 25%; p < .0001) and a shorter time from onset of infarction to peak creatine kinase level (16.9 vs 22.5 hr; p = .0001). Importantly, the prevalence and extent of quantitatively determined 201T1 redistribution within the infarct zone on exercise scintigraphy was greater in patients with NQMI vs those with QMI (60% vs 36%, p = .007; and 0.98 vs 0.53 myocardial segments, p = .0003); when the two groups were stratified on the basis of the infarct-related vessel, subset analysis revealed the same findings. During 30 months median followup, cardiac mortality was low, 8.4% in the QMI group and 9.2% in the NQMI group (p = NS). However, patients with NQMI had a higher reinfarction rate (18.4% vs 6.5%; p = .009), a higher rate of unstable angina necessitating hospitalization (36% vs 22%; p = .034), and had a greater incidence of subsequent bypass surgery or angioplasty (33% vs 19%; p = .018). Moreover, 88% of the recurrent infarctions in the NQMI group involved the same area as the original infarction compared with only 20% in the QMI group (p < .01). Thus, in a consecutive series of patients with uncomplicated myocardial infarction who were eligible for predischarge exercise testing, NQMI was characterized by: (1) similar long-term mortality despite a smaller infarct size and better left ventricular function, (2) a higher rate of reinfarction and incidence of angina and bypass surgery at 30 months, and (3) more evidence of residual infarct zone ischemia as compared to patients with QMI. Our data also suggest that the pathogenesis of NQMI may involve spontaneous reperfusion, since 47% of our patients had ST segment elevation on their admission electrocardiograms, the time to peak creatine kinase level was shorter than that in patients with QMI, and 54% of our patients with NQMI had patent infarct-related vessels during predischarge angiography.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTThere is currently no accepted approach for intraoperative evaluation of the technical adequacy of coronary artery bypass graft anastomoses. High-frequency epicardial echocardiography performed intraoperatively could assess coronary artery bypass graft anastomoses by providing on-line short-axis (cross-sectional) and longitudinal two-dimensional images of the vessels. To validate measurements of anastomoses with high-frequency epicardial echocardiography, luminal diameter determined by high-frequency epicardial echocardiography was compared with that determined histologically after perfusion fixation in 12 dogs studied after coronary artery bypass grafting. Technical errors were deliberately created in some grafts. The results of these animal validation studies showed that maximum luminal diameter of the anastomosis by high-frequency epicardial echocardiography correlated well with histologic measurements (r = .92; high-frequency epicardial echocardiography = 0.8 histology + 0.3). All deliberately created technical errors were detected by an independent observer using high-frequency epicardial echocardiography. After completion of the animal studies, we demonstrated the clinical applicability of this approach in 12 patients. Fifteen coronary artery bypass graft anastomoses were examined intraoperatively with high-frequency epicardial echocardiography. The measured maximum luminal diameter of the anastomosis was greater than the maximum luminal diameter of the native artery, as expected, in all end-to-side anastomoses. However, the maximum luminal diameter of the side-to-side anastomoses was equal to or slightly less than that of the native artery. In this initial patient group, minor technical errors were noted in two of 15 graft anastomoses. In conclusion, high-frequency epicardial echocardiography can accurately measure coronary arterial bypass graft anastomoses and has potential for intraoperative detection of technical errors and inadequacies.Such information may provide a means to detect and correct these technical errors and inadequacies intraoperatively.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTHeart rate and central venous blood temperature (CVT) were measured in 31 people with different exercise capacities by means of a thermistor intergrated into a lead that was placed in the right ventricle. Bicycle ergometric and treadmill stress tests with increasing workloads were performed. The maximum increase in CVT with ergometric exercise was found to be 1.30 C at 250 W in healthy young volunteers and 1.00 C at 125 W in cardiac patients. Despite a relatively greater increase in CVT in the elderly patients compared with the volunteers, the correlation between the increase in CVT and that in heart rate at the end of each exercise stage was found to be very high (r = .9693 in volunteers and r = .9864 in cardiac patients), independent of physical fitness. Even with everyday activities such as walking there was a marked increase in CVT. Due to its close relationship to human metabolism, CVT represents a good parameter for physiologic control of pacing rate.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTFrom 1975 to 1979, 540 patients undergoing valve replacement were entered into a randomized trial and received either a Bjdrk-Shiley (273 patients) or a porcine heterograft prosthesis (initially a Hancock valve [107 patients] and later a Carpentier-Edwards prosthesis [160 patients]). Two hundred and sixty-two patients required mitral valve replacement, 210 required aortic valve replacement,60 required mitral and aortic valve replacement, and eight also required associated tricuspid valve replacement (six mitral valve replacement; two mitral plus aortic valve replacement). Analysis of 34 preoperative and operative variables showed the treatment groups to be well randomized. In-hospital mortality was not significantly different among patients receiving the three prostheses for aortic valve replacement (7.6% overall) and mitral plus aortic valve replacement (10% overall), but there was a higher in-hospital mortality for patients undergoing mitral valve replacement with the Carpentier-Edwards prosthesis (15.5% compared with 8.8% overall; p = .03). This difference could not be explained on the basis of any preoperative or operative variable. Median follow-up was 5.6 (range 2.8 to 8.3) years. Actuarial survival after mitral valve replacement was 56.7 + 7.0% at 7 years, that after aortic valve replacement was 69.6 ± 9.6% at 7 years, and that after mitral plus aortic valve replacement was 62.5 ± 20.0% at 7 years. There was no significant difference in actuarial survival of patients receiving the three prostheses within the mitral, aortic, and mitral plus aortic valve replacement groups, nor was there a difference when these groups were amalgamated. Thirty-seven patients required reoperation for valve failure (15 with Bjbrk-Shiley, 12 with Hancock, and 10 with Carpentier-Edwards valves; p = NS) and 11 died at reoperation (four with Bjdrk-Shiley, four with Hancock, and three with Carpentier-Edwards valves; overall operative mortality 29.7%). Up to 7 years after surgery, there wasno significant difference in the incidence of thromboembolism in patients with the different prostheses undergoing mitral or aortic valve replacement. There were too few patients undergoing mitral plus aortic valve replacement for meaningful comparison. There was no significant beneficial effect of anticoagulants in patients undergoing mitral or aortic valve replacement with porcine prostheses, but patients were not randomly allocated to anticoagulant treatment. All patients with Bjdrk-Shiley prostheses received anticoagulants. Multivariate analysis of factors associated with embolism identified atrial fibrillation with mitral valve replacement (p < .001) and age less than 65 years (p < .01) and arheumatic cause of valvular disease (p < .01) with aortic valve replacement. The risks of anticoagulation were low, with an overall incidence of complications of approximately one per 100 years treatment.To date no significant advantage of any of the three prostheses has been observed, but further follow-up is necessary because important differences may yet emerge.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTObstruction to blood flow is accompanied by a pressure gradient across the obstructed site. In certain clinical settings, magnitude of pressure gradient has been used to judge severity of obstruction, and gradient reduction to judge success of an interventional procedure. In percutaneous transluminal coronary angioplasty (PTCA) the relationships between transstenotic pressure gradient, diameter stenosis, and lesion length are imprecisely known. We therefore examined 4263 sets of measurements in patients who underwent PTCA on single, discrete coronary arterial lesions. Multivariate regression analysis demonstrated that pressure gradient was artifactually elevated by about 12 mm Hg at low values of diameter stenosis but increased by the 4th power of stenosis as expected from fluid dynamics models. Pressure gradient was dampened and relatively constant at values of diameter stenosis of 60% or higher, probably because of total or near-total occlusion of the artery. Lesion length was not found to influence pressure gradient. Reductions in diameter stenosis (AD) and pressure gradient (AG) were related nonlinearly, with AD proportional to the square root of AG, suggesting that a reduction in gradient is directly proportional to an increase in cross-sectional area of the stenosis. The predictive value of final post-PTCA pressure gradients was found: a final gradient of 15 mm Hg or less predicted a final post-PTCA diameter stenosis of 30% or less, with 75% sensitivity and 29% specificity (p < .01). The results of this study suggest that (1) pressure gradient as currently measured during PTCA is related to diameter stenosis but not to lesion length (2) reductions in pressure gradient and diameter stenosis are nonlinearly related, and (3) reductions in pressure gradient and final post-PTCA pressure gradient are useful indicators of initial angiographic outcome.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTAlthough amiodarone is effective for the suppression of complex ventricular arrhythmias, a major problem with its use is the long delay between the initiation of therapy and the onset of effective suppression of arrhythmia. To test the hypothesis that rapid loading with oral amiodarone to a target serum concentration can overcome much of this delay, eight patients with refractory, sustained, hemodynamically compromising ventricular arrhythmias and 10 patients with potentially life-threatening ventricular arrhythmias were treated with a flexible, very high dose, oral loading protocol (800 to 2000 mg two to three times a day). Dosage was adjusted on the basis of amiodarone serum concentrations to maintain the trough serum concentrations between 2.0 and 3.0 gug/ml. Comparison of 24 hr Holter electrocardiograms obtained before and during therapy revealed statistically significant reductions in premature ventricular complexes (PVCs) and paired PVCs beginning the first day of therapy and a reduction in ventricular tachycardia (VT) beginning the second day. By day 2, four of eight patients with sustained VT and six of 10 patients with nonsustained VT showed no VT. Pulmonary arterial catheterization during the first 24 hr (mean amiodarone dose 3933 mg) revealed no significant hemodynamic alterations. Minor side effects were common (10 patients) but major side effects were rare (one patient). High-dose oral loading with amiodarone utilizing serum concentration guidelines is a safe and effective method of rapidly controlling life-threatening arrhythmias in selected patients.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTTo determine whether a regional approach to surgery for ventricular tachycardia would improve on the results of previously reported methods of endocardial resection, an analysis was performed of our surgical experience over a 5 year period. Of 46 consecutive patients operated on for recurrent sustained ventricular tachycardia or ventricular fibrillation, 39 patients with ischemic heart disease underwent subendocardial resection and/or cryoablation. The mean age of the patients was 61 + 8 (SD) years, the mean left ventricular ejection fraction was 32 ± 1 1 %, and the mean number of ineffective antiarrhythmic drugs was 3.8 ± 1.2 per patient. In 35 of 39 patients in whom mapping data were obtainable, 56 (86%) tachycardias had earliest sites of activation in the left ventricle and nine (14%) had earliest sites in the right ventricle. Ten patients had 14 tachycardias (21 %) mapped to areas outside visible dense scar. Of these 35 patients, 10 underwent localized subendocardial resection and 25 underwent a regional procedure in which all areas activated before the surface QRS during ventricular tachycardia were excised and/or cryoablated. In the operative survivors of electrophysiologically guided surgery, three of eight (38%) patients with the localized and one of 24 (4%) patients who underwent the regional procedure had recurrence of ventricular tachycardia during a follow-up period of 1 to 59 (mean 22 ± 17) months (p = .04). The favorable outcome of regional surgery was not influenced by the presence of multiple morphologies in 54%, disparate sites of origin in 29%, or inferior wall foci in 46% of patients. These data suggest that (1) some ventricular tachycardias have earliest sites of activation outside visible dense scar and/or within the right ventricle, (2) a regional approach to arrhythmia ablation can lead to operative success in over 90% of patients, and (3) multiple morphologies, disparate sites, and inferior wall origin are not adverse prognostic factors to success when this approach is used.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTTo investigate the mechanism of the antianginal action of diltiazem in stress-induced myocardial ischemia, we studied 12 patients with stable exertional angina and disease of the proximal left anterior descending artery by measuring great cardiac vein flow (GVCF) and calculating anterior regional coronary resistance (ARCR) during myocardial ischemia induced by atrial pacing before and after intravenous administration of diltiazem (0.25 mg/kg in a bolus dose followed by continuous infusion of 0.005 mg/kg/min). Diltiazem increased the pacing time to angina from 6.9 ± 3.5 to 10.7 + 4 min (p < .001). At peak pacing heart rate was increased after diltiazem (from 128 + 17 to 145 + 17 beats/min, p < .005), while mean arterial pressure was decreased (from 131 + 19 to 1 13 + 17 mm Hg, p < .025), leaving the double product unaltered. At peak pacing no changes were observed in GCVF (from I 15 + 46 to 1 19 + 46 ml/min, p = NS), ARCR (from 1.3 ± 0.4 to 1. 1 + 0.4 mm Hg/ml/min), or myocardial oxygen consumption of the anterior region (from 14.5 + 4.2 to 13.4 ± 4.7 ml/min). Reduction of myocardial oxygen demand plays a major role in the antianginal action of diltiazem in patients with stress-induced myocardial ischemia.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID