摘要:

BackgroundTraditional lead systems for implantable cardioverter defibrillators (ICDs) require a thoracotomy for placement. Nonthoracotomy lead systems are available and are usually implanted by an electrophysiologist and a surgeon. The purpose of this study was to prospectively evaluate the safety and efficacy of ICD implantation with a nonthoracotomy lead system by electrophysiologists.Methods and ResultsA consecutive series of 100 patients (mean age, 61±13 years, ±SD) underwent ICD implantation with a nonthoracotomy lead system while intubated and under general anesthesia. Seventy-seven patients had coronary artery disease, 15 had idiopathic cardiomyopathy, 6 had miscellaneous heart disease, and 2 had structurally normal hearts. The mean ejection fraction was 0.29±0.13. Sixty-eight patients had suffered a cardiac arrest, and 32 had had ventricular tachycardia or syncope. All patients except 9 underwent electrophysiological testing and had failed 1 ± 1 drug trials before ICD implantation. Three types of nonthoracotomy lead systems were used. The nonthoracotomy lead with an ICD was successfully implanted in 96 patients (96%). Of the unsuccessful implants, 1 patient did not have venous access, the passive fixation lead in 1 would not remain lodged, 1 had elevated defibrillation thresholds, and 1 developed a hemopneumothorax while venous access was being obtained. The mean defibrillation threshold was 17±6 J. The mean procedure duration was 161±57 minutes. When a subcutaneous patch was used (n=58), the procedure duration was 189±5 minutes, and when a subcutaneous patch was not required (n=40), the procedure lasted 123±37 minutes (P<.0001). Patients remained in the hospital 4.5±4.1 days after implantation, with no procedure-related deaths. Acute complications occurred in 10 patients; 2 had lead dislodginents, 1 with previous abdominal surgery had his abdominal cavity entered (without other complications) while the ICD pocket was being made, 1 had postoperative heart failure, 1 developed a large hematoma when anticoagulation therapy was initiated, 3 required reintubation because of excessive anesthesia, 1 developed superficial cellulitis, and 1 developed a hemopneumothorax secondary to a lacerated subclavian vein. During 6±3 months of follow-up, 2 patients developed lead fractures.Conclusions(1) Electrophysiologists can implant an ICD with a nonthoracotomy lead system safely and with a high success rate; (2) use of a subcutaneous patch correlates with longer procedure durations; and (3) special precautions should be taken in patients with previous abdominal surgery.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background“Inappropriate” sinus tachycardia (IST) is an uncommon and poorly defined atrial tachycardia characterized by inappropriate tachycardia and exaggerated acceleration of heart rate with “normal” P wave. The mechanism of this tachycardia is unknown. The purpose of the present study was to determine the role of autonomic balance in the genesis of IST.Methods and ResultsSix female patients aged 23 to 38 years with IST and 10 age- and sex-matched control subjects were assessed with the following autonomic function tests: (1) sympathovagal balance to the sinus node assessed by calculating the LF/HF (low frequency/high frequency) ratio using power spectral analysis both in the supine position and after 10 minutes of head-up tilt to 60°, (2) cardiovagal reflex assessed by cold face test (CFT), (3) β-adrenergic sensitivity as determined by calculating isoproterenol dose-response curves and isoproterenol chronotropic dose 25 (CD25), and (4) intrinsic heart rate (IHR) assessed after autonomic blockade with atropine 0.04 mg/kg and propranolol 0.2 mg/kg administered as an intravenous bolus. No significant differences in the LF/HF ratio both in the supine position (2.8±0.3 versus 2.6±0.4) and during upright tilt (8.7± 1.3 versus 8.5 ±0.5) were observed between control subjects and IST patients. Cardiovagal response to CFT was markedly depressed in all patients (6.3% IST patients versus 24.2% control subjects,P<.001). β-Adrenergic hypersensitivity to isoproterenol was noted in all patients (mean CD25, 0.29±0.10 μg IST patients versus 1.27±0.4 μg control subjects;P<.001), and high IHR was noted in all cases. The patients were treated with high doses of β-blockers with adequate short-term control. Radiofrequency catheter ablation of the sinus node area was performed in one drug-refractory patient.ConclusionsThese findings suggest that the mechanism leading to IST is related to a primary sinus node abnormality characterized by a high IHR, depressed efferent cardiovagal reflex, and β-adrenergic hypersensitivity.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe prognostic implications of alterations in heart rate variability have not been studied in a large community- based population.Methods and ResultsThe first 2 hours of ambulatory ECG recordings obtained on original subjects of the Framingham Heart Study attending the 18th biennial examination were reprocessed to assess heart rate variability. Subjects with transient or persistent nonsinus rhythm, premature beats >10% of total beats, <1 hour of recording time, processed time <50% of recorded time, and those taking antiarrhythmic medications were excluded. The associations between heart rate variability measures and all-cause mortality during 4 years of follow-up were assessed. There were 736 eligible subjects with a mean age (±SD) of 72±6 years. The following five frequency domain measures and three time domain measures were obtained: very-low-frequency power (0.01 to 0.04 Hz), low-frequency power (0.04 to 0.15 Hz), high-frequency power (0.15 to 0.40 Hz), total power (0.01 to 0.40 Hz), the ratio of low-frequency to high-frequency power, the standard deviation of total normal RR intervals, the percentage of differences between adjacent normal RR intervals that are >50 milliseconds, and the square root of the mean of the squared differences between adjacent normal RR intervals. During follow-up, 74 subjects died. In separate proportional hazards regression analyses that adjusted for relevant risk factors, very-low-frequency power (P<.0001), low-frequency power (P<.0001), high-frequency power (P=.0014), total power (P<.0001), and the standard deviation of total normal RR intervals (P=.0019) were significantly associated with all-cause mortality. When all eight heart rate variability measures were assessed in a stepwise analysis that included other risk factors, low-frequency power entered the model first (P<.0001); there-after, none of the other measures of heart rate variability significantly contributed to the prediction of all-cause mortality. A 1 SD decrement in low-frequency power (natural log transformed) was associated with 1.70 times greater hazard for all-cause mortality (95% confidence interval of 1.37 to 2.09).ConclusionsThe estimation of heart rate variability by ambulatory monitoring offers prognostic information beyond that provided by the evaluation of traditional risk factors.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe use of bipolar endocardial electrogram characteristics to guide radiofrequency (RF) current catheter ablation of accessory pathways (APs) has been advocated by several investigators. However, the influences of a varying anatomy of the AP and the atrioventricular groove, of different ablative approaches, and of RF current pulses preceding the final pulse have not been adequately addressed.Methods and ResultsLocal bipolar endocardial electrograms were retrospectively analyzed in a uniform cohort of 62 consecutive patients with a single manifest AP located on the left free wall; in all patients, the AP had been ablated by a uniform approach with a single catheter advanced retrogradely toward the mitral annulus. Electrogram parameters assessed were the presence or absence of a presumed AP potential, the atrial-to-ventricular (A/V) amplitude ratio, the A-V interval, and the onset of delta wave to local ventricular activation (Δ-V) interval. The AP location was classified on fluoroscopy as anterior, lateral, or posterior. Catheter stability was verified by comparing pre- and post-RF amplitudes of local atrial potentials. The ablation site was ventricular in 52 patients (group A) and atrial in 10 (group B). In group A, 26 APs (50%) required a single RF current pulse for ablation. These APs showed no anatomic predilection and no statistically significant differences in electrogram parameters from 24 APs that were ablated only after a median of three pulses had failed, suggestive of a wider ventricular insertion of the latter APs. A lower A/V ratio and a higher incidence of transient AP block found in the remaining 2 group A patients, who had anteriorly located APs requiring > 10 failed pulses, suggested an adverse anatomy of the A-V groove in that region. A stepwise multivariate logistic regression analysis revealed that the simultaneous presence of (1) a presumed AP potential, (2) an A/V ratio.0.10, (3) an A-V interval ≤40 milliseconds, and (4) a Δ-V interval ≤0 milliseconds was associated with a specificity of 94% and a positive predictive accuracy of 87% for an RF pulse to be successfully applied to the ventricular insertion to the AP. Compared with APs of group A, APs of group B were distinguished by unsuccessful ventricular pulses associated with a Δ-V interval >10 milliseconds in the presence of an A/V ratio >0.33 (specificity of 97% and positive predictive accuracy of 82%), which is suggestive of a more epicardial ventricular insertion of these APs.ConclusionsThe effect of anatomic variations of the AP and the A-V groove is reflected in the bipolar endocardial electrogram and needs to be considered in the approach to AP ablation. The stepwise inclusion of the four electrogram criteria introduced in this study may improve the efficacy of RF catheter ablation of a manifest left free-wall AP at its ventricular insertion. Whenever mapping cannot improve on a Δ-V interval >10 milliseconds despite apparently close contact with the mitral annulus (“good” A/V ratio), attempts at ablation are likely to be successful at the atrial aspect of the mitral annulus.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundVasoconstriction occurs after percutaneous transluminal coronary angioplasty (PTCA) along the dilated vessel. The vasomotor changes, initiated by the mechanical stretch of the stenotic region, are thought to be due to various mechanisms but whether the sympathetic nervous system plays a role in this phenomenon remains unknown.Methods and ResultsQuantitative angiography (ARTREK) was performed in 45 patients undergoing an epicardial vessel PTCA for a stenosis of 76±1% (1) in basal conditions, (2) after PTCA, and (3) 30 minutes after PTCA (vasoconstriction). In 14 control patients, the same measurements were obtained up to 60 minutes after PTCA. Coronary diameters were measured along the PTCA vessel at the narrowest stenosis level and at a level peripheral to stenosis. In 36 patients two diameters were also measured at a proximal segment and at a distal segment along a nonmanipulated vessel.Thirty minutes after PTCA the dilated segment under-went a −31±2% (mean±SEM, ANOVA,P<.05) reduction in diameter when compared with PTCA values, and the segment peripheral to stenosis showed a reduction of −17±2% (P<.05).In all patients a significant vasoconstriction also was observed along the control vessel (proximal segment, −14±3%;P<.05 versus basal; and distal segment, −17±2%). At the time of maximal vasoconstriction (30 minutes after PTCA), the patients (treatment groups) received (1) 18 μg/kg IC phentolamine (Phe, n=7), (2) 14 μg/kg IC yohimbine (YO, n=7), (3) 16 μg/kg IC propranolol (Pro) followed by 18 μg/kg IC phentolamine (Pro+Phe, n=7), and (4) 0.2 μg/kg IC bretylium (Bre, n=10). In 14 patients (control groups) an intracoronary injection of warm saline was given. After drug injections, angiograms were repeated at 5-minute intervals for 20 minutes and ended after a 300-μg intracoronary trinitro-glycerin injection. At stenosis level, Phe and Bre counteracted vasoconstriction, inducing a dilatation of +19±3% and +22±6%, respectively, while Pro+Phe caused a dilatation of +16±9% above the PTCA values (P<.05 versus PTCA). YO only partially reversed vasoconstriction (from −33±4% to −12±4%,P=NS versus PTCA). At peripheral-to-stenosis level, vasoconstriction was abolished by Phe (+26±7%,P<.05 versus basal), while it was still present after Pro+Phe (−23±2%) and Bre (−18±4%). In addition, Phe and Bre dilated the control vessel at the proximal segment (+17±6% and +8±4%, respectively,P<.05 versus basal), while YO and Pro+Phe only counteracted vasoconstriction (from −15 ±3% to +7.6±1% and from −16±3% to +4±5%, respectively,P=NS versus basal). At the distal segment only Phe produced a vasodilatation of +23±1%; YO counteracted constriction (from −16±2% to +9±6%,P<.05 versus basal), whereas after Pro+Phe and Bre, the vasoconstriction persisted.ConclusionsThe mechanical stretch and ischemia caused by balloon inflation induced vasoconstriction mediated by a-adrenergic receptors (mainly α1,), overcoming a β-mediated dilatation. The use of different antiadrenergic drugs showed that Phe counteracts post-PTCA vasoconstriction, and the simultaneous use of α- and β-receptor blocking agents (Pro+Phe and Bre) reveals the presence of a peripheral, predominant β-mediated dilatation. The presence of vasoconstriction also along the control vessels not branching from the stretched ramus provides evidence for the existence of neural sympathetic vasoconstrictor reflexes.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundHeparin, an anticoagulant, possesses antiproliferative effects and has been shown to reduce neointimal proliferation and restenosis following vascular injury in experimental studies.Methods and ResultsThe primary aim of this double-blind multicenter study was to determine if 40 mg Enoxaparin, a low molecular weight heparin, administered subcutaneously once daily for 1 month after successful angioplasty would reduce the incidence of restenosis. Four hundred fifty-eight patients were randomized at nine clinical centers (231 to placebo and 227 to Enoxaparin). The primary end point was angiographic or clinical restenosis. Angiographic restenosis was defined as a loss of 50% of the initial gain as measured by quantitative coronary angiography (QCA) at a core laboratory. In the absence of QCA, clinical evidence of restenosis was defined as death, myocardial infarction, repeat revascularization, or worsening angina. Using the intention-to-treat analysis for all patients, restenosis occurred in 51% of the placebo group and 52% of the Enoxaparin group (relative risk, 1.07,P=.625). Likewise, no difference in restenosis was evident when the change in minimal lumen diameter or other angiographic definitions of restenosis were used. Adverse clinical events were infrequent and did not differ between the groups with the exception of minor bleeding complications, which were more common in the Enoxaparin group.ConclusionsEnoxaparin (40 mg/d SC for 1 month) following successful angioplasty did not reduce the incidence of angiographic restenosis or the occurrence of clinical events over 6 months. The treatment was well tolerated, although in-hospital minor bleeding was more common with active treatment.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundWe wished to determine the nature and incidence of changes in the iliofemoral arteries after balloon dilation angioplasty (BDA) for aortic arch obstruction in children and to determine the reliability of gradient magnetic resonance imaging (MRI) in their detection.Methods and ResultsSixty-three children, including 62 with and 1 without arch obstruction, underwent MRI of the iliofemoral vessels. Of these, 36 patients had undergone transfemoral BDA (7 after previous transfemoral diagnostic catheterization), 12 had undergone diagnostic transfemoral catheterization but not BDA, and 15 had no history of femoral arterial catheterization. The iliofemoral arteries were normal on MRI in all 15 children without catheterization. Among the 36 children who had undergone BDA, the ipsilateral iliofemoral artery was normal in 15, mildly narrowed in 7, and severely stenotic or occluded in 14 (39%), including 6 of 9 patients treated for acute femoral artery thrombosis and 8 with no history of femoral artery thrombosis. Two patients had documentation of progressive obstruction. Six patients had concordant conventional angiography. There was a significant correlation between the number of balloon catheters used for the angioplasty and severe occlusive changes. Nine of 19 patients who had undergone diagnostic transfemoral catheterization had severe obstructive changes on MRI; 8 of 9 weighed <10 kg at catheterization.ConclusionsObstructive lesions of the iliofemoral arteries are common after transfemoral BDA of arch obstructions (58%) and can be reliably evaluated with gradient MRI. Catheter size and manipulation are the main contributing factors.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundPatients on cardiopulmonary bypass (CPB) have an increased susceptibility to postoperative bleeding. Previous reports using desmopressin acetate (DDAVP) for the prevention of postoperative bleeding have given contradictory results, whereas the protease inhibitor aprotinin has been shown to reduce blood loss after this type of surgery. This randomized study was performed to assess the efficacy of DDAVP versus aprotinin in the prevention of bleeding after CPB.Methods and ResultsOne hundred nine of 122 eligible patients were randomized to four different groups: Group A (n=28) received aprotinin starting with a bolus of 2×106KIU followed by a continuous infusion of 0.5×106KIU/h until the end of surgery; group B (n=25) received of DDAVP 0.3 μ/kg IV on completion of CPB; group C (n=28) received two doses of DDAVP, the first as in group B and an additional dose 6 hours after surgery; group D (n=28) received no treatment. There was a marked reduction of postoperative blood loss either at 12 hours (P<.01) or 72 hours (P<.02) in the aprotinin group compared with all other groups, whereas no significant effect was observed in either of the two DDAVP regimens. A significant reduction in the amount of blood used was observed only in the aprotinin group (P<.01). Of the plasma fibrinolytic components assayed, there was a significant reduction of the fibrin degradation product generation in the aprotinin group (P<.001), whereas a significant systemic hyperfibrinolysis was observed in both DDAVP-treated groups and the control group. No side effects related to the study drugs were observed in any patient.ConclusionsAprotinin inhibited fibrinolysis; this correlated with a significant reduction of postoperative blood loss and need for blood replacement after CPB. Neither one nor two doses of DDAVP had a beneficial effect. Aprotinin offers better alternative than DDAVP in the prevention of bleeding after CPB.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundLeft ventricular hypertrophy (LVH) defined by either ECG or echocardiographic criteria is a risk factor for cardiovascular morbidity and mortality. A number of determinants of LVH have been described in previous studies, principally male sex, hypertension, obesity, and aortic valvular stenosis. We examined the distribution of LV mass (LVM) in a population of 18- to 42-year-old normotensive men and women who were free of valvular heart disease to establish sex-specific normal values for LVM index (LVMI) and to determine the correlates of LVMI.Methods and ResultsLVM was derived from measurements obtained by M-mode echocardiography. Average LVMI is significantly greater in men (102.9±0.7 g/m2) than women (88.2±0.7 g/m2). By defining LVH as an LVMI greater than the 90th percentile, we developed sex-specific criteria for LVH: men, >125.4 g/m2; women, >110 g/m2. We found that LVH in men is associated with indices of enhanced sympathetic nervous system reactivity and with elevated fasting insulin and triglyceride levels, which may be caused by insulin resistance. In women, LVH was associated with higher body weight and obesity.ConclusionsBefore the onset of hypertension, increased LVMI appears to have different determinants in men and women. We suggest that early LVH in young men is a manifestation of hyperkinetic borderline hypertension, a state previously shown to be associated with increased sympathetic nervous system activity and insulin resistance. The hyperkinetic state is less prevalent in young women, in whom increased adiposity seems to be the predominant factor associated with LVH.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundKnowledge about the volume of collateral flow provides insight into the severity of coarctation of the aorta and may be critical in planning the operative approach. There is currently no method for the quantification of collateral flow in coarctation of the aorta. In this study, we applied velocity encoded cine magnetic resonance imaging (VENC-MR) to establish the flow pattern and volume of collateral flow in the descending thoracic aorta in normal subjects and patients with coarctation, introducing a new possibility to quantify the severity of the coarctation by determining the amount of collateral flow.Methods and ResultsVENC-MR was used to measure flow in the proximal and distal descending thoracic aorta in 10 normal subjects. In 23 patients with coarctation, flow was measured near the coarctation site and above the diaphragm. Patients were divided into a group with moderate to severe coarctation and a group with mild coarctation on the basis of clinical gradient between upper and lower extremities and the estimation of the gradient across the coarctation by Doppler echocardiography. The gradient across the coarctation and the degree of anatomic narrowing were also assessed by MR imaging. In normal volunteers, VENC-MR showed a 7±6% decrease in total flow, from proximal to distal aorta. The interobserver reproducibility was 3.9% to 4.9% (mean, 4.4%). In patients with moderate to severe coarctation, VENC-MR demonstrated an 83±50% increase in total flow from proximal to distal aorta, yielding a significant change compared with normal subjects (P<.01). Patients with mild coarctation showed a normal flow pattern and no significant change in total flow. There was a significant relation between the amount of flow increase in the distal aorta and the reduction in luminal diameter at the coarctation site (r=.94) as well as the clinical gradient (r=.84).ConclusionsThis study shows the normal flow pattern in the descending thoracic aorta and its reversal in coarctation due to collateral flow. Thus, VENC-MR can measure collateral flow in coarctation and serves as a unique method for providing this important measurement of the severity of coarctation of the aorta.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID