摘要:

BackgroundA unipolar defibrillation system using a single right ventricular (RV) electrode and the active shell or “CAN” of the implantable cardioverter-defibrillator itself situated in a left infraclavicular pocket has been shown to be as efficient in defibrillation as an epicardial lead system. The purpose of this study was to determine whether defibrillation efficacy can be improved further by adding a superior vena cava (SVC) electrode to this already efficient defibrillation system.Methods and ResultsWe prospectively and randomly compared the defibrillation efficacy of a simplified unipolar defibrillation system, RV→CAN, with that of one incorporating a high SVC electrode, RV→SVC+CAN, in 15 consecutive cardiac arrest survivors undergoing implantation of a presently available transvenous defibrillation system. The RV defibrillation electrode was a 5-cm coil located on a 10.5F lead used as the anode in both lead configurations examined. The active CAN was a 108−cm2surface area shell of a titanium alloy pulse generator used as the cathode in both configurations and placed in a left infraclavicular pocket. The SVC electrode was a 6F 5-cm-long coil and was used as an additional cathode positioned at the junction of the SVC and the left innominate vein. The defibril-lation pulse used was a 65% tilt, asymmetric biphasic waveform delivered from a 120-μF capacitor. The defibrillation threshold (DFT) stored energy, leading edge voltage, current, and pulsing resistance were measured for both lead systems. The single-lead unipolar system, RV→CAN, resulted in a stored energy DFT of 7.4±5.2 J, and the three-electrode dual pathway system, RV→SVC+CAN, resulted in a DFT of 6.0+3.4 J (P= .20). There was no difference in defibrillation efficacy with the more complicated three-electrode system over the unipolar system despite a decrease in pulsing resistance to 48.6±3.5 Ω compared with 61.2±5.9 Ω for the unipolar system (P< .0001) and a slight rise in delivered current to 6.3±1.8 A compared with 5.5 ±2.0 A for the unipolar system (P= .062).ConclusionsThe unipolar single-lead transvenous defibrillation system provides defibrillation at energy levels comparable to that reported with present epicardial lead systems. Coupling of this lead system to a third SVC electrode increases system complexity but offers little defibrillation advantage despite a large decrease in pulsing resistance and a modest increase in delivered current.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundRecurrent sustained ventricular tachycardia (VT) is not responsive to antiarrhythmic drugs in the majority of patients, who therefore need therapy with nonpharmacological methods. We evaluated prospectively the feasibility, safety, and efficacy of transcatheter radiofrequency (RF) ablation of VT in 21 selected patients with ischemic heart disease and VT.Methods and ResultsTwenty-one patients with ischemic heart disease and recurrent, drug-refractory VT documented by 12-lead ECG were selected who had sufficient hemodynamic tolerance of VT to undergo transcatheter mapping. Documented clinical VT was reproduced by programmed cardiac stimulation (PCS), and the site of origin was localized by a combination of techniques, including pace mapping, activation-sequence mapping, recordings of middiastolic potentials, and application of resetting and entrainment principles. RF current at 55 V was applied (3.8+3.1 applications per patient) for as long as 30 seconds at a time to target sites. Twenty-four distinct clinical VTs (mean cycle length, 445±52 milliseconds) were mapped and ablated in 21 patients. In 17 of 21 patients (81%), the procedure was acutely successful, and the target clinical VT could no longer be induced by PCS after the procedure, whereas in 4 patients, clinical VT remained inducible. By contrast, VTs with shorter cycle length and different QRS morphology than the ablated VT could still be induced by PCS in 12 of 21 patients. One patient died in intractable congestive heart failure 10 days after the procedure, and the remaining 20 are alive at the end of the follow-up period. The majority of the patients continued to be treated with at least one additional mode of antiarrhythmic therapy; 12 patients were still taking antiarrhythmic drugs, and 9 patients received an implantable cardioverter/defibrillator. During a mean follow-up period of 13.2+5.0 months, 9 of 20 patients (45%) had recurrent VT. In 4 patients, the recurrent VT was different than the previously ablated one. Clinical VT recurred in all 4 patients in whom RF ablation had been acutely unsuccessful. Four patients with recurrent VT underwent repeat RF ablation procedures that were acutely successful and had no further recurrence.ConclusionsTranscatheter RF ablation is feasible but has only moderately high efficacy in a small, selected group of patients with ischemic heart disease and drug-refractory, highly frequent, hemodynamically tolerated, sustained VT. In the majority of the patients, this treatment technique is palliative rather than definitive, and many of the patients continue to require other methods of antiarrhythmic therapy.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundShortening of the anterograde effective refractory period (ERP) of the fast pathway has been reported after radiofrequency ablation of the slow pathway. We hypothesized that ERP shortening may be related to autonomic changes, possibly catecholamine release, as a result of ablation.Methods and ResultsTo test this, 10 consecutive patients with atrioventricular node reentry undergoing slow pathway ablation were given autonomic blockade before the ablation procedure. This was achieved by atropine 0.03 mg/kg and propranolol 0.15 mg/kg IV supplemented by half the initial dose after ablation and before the final study. A control group of 10 patients underwent the protocol without autonomic blockade. Before ablation, autonomic blockade did not alter the ERP of either the fast pathway (295±22 versus 298±26 milliseconds) or the slow pathway (264±36 versus 269±38 milliseconds). Autonomic blockade obscured dual pathway physiology in 2 patients and brought it out in another 2 without dual pathway physiology initially. Slow pathway ablation shortened the ERP of the fast pathway for the group as a whole (331.5±54 versus 305.5±60 milliseconds, mean±SD,n= 20,P< .04). There was no difference in degree of ERP shortening in control patients (23.5±58 milliseconds) or autonomic blockade patients (25.5±52 milliseconds).ConclusionsThese data suggest that shortening of the ERP of the fast pathway after slow pathway ablation is not mediated by autonomic changes.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe objective of the study was to determine the coronary vasodilatory reserve in reperfused myocardium in patients with acute myocardial infarction and its relation to regional myocardial function.Methods and ResultsThe study population consisted of 22 patients with acute myocardial infarction who underwent successful coronary angioplasty. The vasodilatory reserve in reperfused myocardium was assessed quantitatively using computer-assisted digital subtraction cine-angiography immediately after angioplasty and at follow-up angiography before hospital discharge. Myocardial contrast medium appearance time and density were determined before and after pharmacological hyperemia induced by an intracoronary injection of 12.5 mg papaverine. Global and regional left ventricular functions were determined from contrast angiography. After papaverine, the mean contrast medium appearance time decreased significantly from 3.5±0.7 to 2.7±0.7 cardiac cyclesP< .000005) immediately after successful coronary angioplasty and from 3.8±0.7 to 2.7±0.9 cardiac cycles (P< .000005) angiography before hospital discharge. The mean contrast medium density increased significantly from 48.7±13.8 to 61.0±19.0 pixels (P< .003) and from 49.6±19.7 to 80.3±29.6 pixels (P< .000005), respectively. As a consequence, the calculated coronary flow reserve increased significantly from 1.8±0.7 to 2.6±1.0 (P< .0008). The global ejection fraction increased significantly from 52±12% to 58±14% (P< .03), primarily because of a significant improvement in the regional myocardial function of the infarct zone from 20.8±9.0% to 26.0±10.5% (P< .0001). Coronary flow reserve correlated well with regional myocardial function both during the acute phase (R= .79,P< .002) and at follow-up angiography (R= .82,P< .000004). Interestingly, coronary flow reserve measurement on reperfusion, immediately after angioplasty, correlated significantly with regional myocardial function at follow-up angiography (R= .81,P< .00003).ConclusionsThe results indicate that there is a pharmacologically inducible vasodilatory reserve in reperfused ischemic myocardium after successful coronary angioplasty in patients with acute myocardial infarction and that this is increased at 10-day follow-up angiography. More important, the degree of reactive hyperemic response on reperfusion has a predictive value regarding the ultimate degree of recovery of regional myocardial function. Quantitative assessment of reperfusion may be useful in investigating the role of coronary reperfusion and salvage of myocardial function.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundObservational studies have suggested that prolonged balloon inflation during coronary angioplasty is associated with a high clinical success rate. This randomized clinical trial sought to evaluate the impact of primary gradual and prolonged inflations versus standard short dilatations in patients undergoing elective angioplasty.Methods and ResultsIn phase 1 of the study, patients were randomized to receive two to four standard (1 minute) dilatations one or two prolonged (15 minutes) dilatations after a perfusion balloon had been placed across a single target lesion. Patients with unsuccessful angiographic appearance after phase 1 dilatations had further dilatations in phase 2. Patients were followed for 6 to 12 months after the procedure. Of 478 patients, 242 received a median of one prolonged dilatation of 15 minutes' duration, and 236 received three dilatations for a median of 1 minute. Patients assigned to prolonged dilatations had a higher success rate (≤50% residual visual stenosis) (95% versus 89%;P= .016), less severe residual stenosis by quantitative angiography median [25th and 75th percentiles], 35% [26%, 42%] versus 38% [30%, 46%];P= .001), and a lower rate of major dissections 3% versus 9%;P= .003) at the end of phase 1. A total of 114 patients had further dilatations in phase 2 - 43 in the prolonged arm and 71 in the standard arm. The final procedural success rate was 98% with both primary dilatation strategies, which included additional maneuvers such as prolonged dilatations in the patients randomized to the primary standard dilatation. Overall, 320 of 416 patients (77%) who were discharged after a successful procedure without any in-hospital event (death, myocardial infarction, coronary artery bypass graft surgery, abrupt closure, or repeat angioplasty in target vessel) returned for follow-up angiography. The restenosis rate (>50% residual visual stenosis) was 44% (95% confidence interval, 37% to 52%) in the prolonged dilatation group and 44% (36% to 52%) in the standard dilatation group. The primary angiographic end point of failure at the end of phase 1, abrupt closure, or restenosis throughout the study period was similar in both groups (prolonged, 51%; standard, 49%;P= .62). The secondary end point of absence of clinical events (death, nonfatal myocardial infarction, coronary artery bypass graft surgery, or repeat angioplasty in target vessel) also was similar (prolonged, 66%; standard, 74%;P= .15).ConclusionsPrimary gradual and prolonged dilatations caused less arterial trauma with a modestly larger arterial lumen compared with standard dilatations. This initial improvement in angiographic appearance did not lead to a significant reduction in restenosis or clinical adverse events during follow-up.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundAbrupt vessel closure and early reocclusion remain the principal vascular events underlying early recurrent ischemia complicating elective percutaneous transluminal coronary angioplasty (PTCA). Intracoronary stenting has been used to circumvent emergency bypass surgery after acute vessel closure and as an adjunct for the elective treatment of restenosis. The initial multicenter experience with the Gianturco- Roubin stent is presented, and predictors for early recurrent ischemic events are identified.Methods and ResultsData accrued from 639 serial patients undergoing emergency stenting for abrupt closure (n=415; 65%) or elective deployment for restenosis (n=224; 35%) from October 1989 through May 1991 were analyzed. The incidence of subsequent ischemic events, including death, nonfatal myocardial infarction, and bypass surgery referral within 90 days of the procedure, was higher after acute deployment (20%) compared with elective stenting (9%;P= .0004). Although mortality within the two cohorts was the same (3%;P= NS), there were significant differences in the incidence of nonfatal myocardial infarction (5% versus 0.5%;P= .002) and bypass surgery (12% versus 6%;P= .02) between the acutely and electively stented patients, respectively. These events were significantly more common when the stent was undersized to the target vessel diameter (stent:artery ratio for event, 0.95±0.14 versus no event, 1.04±0.22;P= .0001) or when there was less expansion of the lesion by the deployed device (stent-to-lesion diameter ratio for event, 6.6±9.2 versus no event, 11.0±21.4;P= .0001). In a stepwise logistic regression model, acute stenting (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3 to 2.4), multivessel disease (OR, 1.4; CI, 1.1 to 1.8), larger target lesion diameter (OR, 2.1; CI, 1.4 to 3.2), larger target vessel (OR, 2.9; CI, 1.7 to 4.7), and smaller stent size (OR, 6.1; CI, 3.0 to 12.3) were independent predictors of early, recurrent ischemic events. The presence of thrombus was associated with a higher event rate after elective stenting (OR, 2.3; CI, 1.06 to 5.4) but was not associated with a higher early event rate after acute stenting.ConclusionsEarly ischemic events are more common after acute stenting for abrupt or threatened closure than after elective deployment. These events may be avoided with careful attention to morphometric characteristics to avoid undersizing the stent to the target vessel and ensure adequate lesion expansion.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe long-term success of coronary bypass surgery is dependent on graft patency after surgery. This trial was designed to determine if aspirin improved saphenous vein graft or internal mammary artery (IMA) graft patency between 1 and 3 years after coronary artery bypass grafting (CABG).Methods and ResultsAfter receiving aspirin 325 mg/d for 1 year after CABG and undergoing a 1-year postoperative cardiac catheterization, patients were randomized to receive either aspirin (325 mg) or placebo for 2 additional years. Angiography was performed 3 years after surgery to determine the primary end point-saphenous vein graft patency in 288 patients and IMA graft patency in 167 patients. At 3 years after CABG, the saphenous vein graft occlusion rate was 17.0% (62 of 365) for patients treated with aspirin compared with 19.7% (74 of 376) for those who received placebo (P= .404). For saphenous vein grafts that were patent at 1 year, the occlusion rate at 3 years was 4.8% (15 of 313) for patients treated with aspirin compared with 4.2% (13 of 310) for patients who received placebo (P= .757). At 3 years, the IMA graft occlusion rate was 10.3% (8 of 78) for patients treated with aspirin compared with 7.9% (7 of 89) for patients who received placebo (P= .594). For IMA grafts that were patent at 1 year, the occlusion rate was 4.3% (3 of 70) for patients treated with aspirin compared with 2.5% (2 of 81) for patients who received placebo (P= .541).ConclusionsThese data suggest that aspirin treatment does improve saphenous vein graft or IMA graft patency between and 3 years after CABG.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe exercise-induced rise in arterial potassium concentration ([K+]a) may contribute to exercise hyperpnea and could play a role in exertional fatigue. This study was designed to determine whether the exercise-induced rise in K+]a is altered in patients with chronic heart failure (CHF) and whether physical training affects K+homeostasis.Methods and ResultsWe evaluated 10 subjects with CHF ejection fraction, 23±3.9%) and 10 subjects with normal left ventricular function (NLVF) who had undergone previous coronary artery graft surgery (ejection fraction, 63±8.6%). Subjects performed an incremental cycle ergometer exercise before and after a physical training or detraining program. Changes in [K+Ia and ventilation (VE) during exercise were closely related in both groups. Subjects with CHF did less absolute work and had reduced maximal oxygen consumption Vo2max) compared with subjects with NLVF (P< .01). Exercise- induced rises in [K+]a, VE, norepinephrine, lactate, and heart rate were greater at matched absolute work rates in subjects with CHF than in subjects with NLVF (P< .01). However, when the rise in [K+]a was plotted against percentage of Vo2max to match for relative submaximal effort, there were no differences between the two groups. Physical training resulted in reduced exercise-induced hyperkalemia at matched submaximal work rates in both groups (P< .01) despite no associated change in the concentration of arterial catecholamines. At maximal exercise when trained, peak increases in [K+]a were unaltered, but peak concentrations of catecholamines were raised (P< .05). The decrease in VE at submaximal work rates after training was not significant with this incremental exercise protocol, but both groups had an increased peak VE when trained (P< .01).ConclusionsExercise-induced rises in [K+]Ka, catecholamines, and &OV0622;Eare greater at submaximal work rates in subjects with CHF than in subjects with NLVF. Physical training reduces the exercise-induced rise in [K+], but does not significantly decrease &OV0622;Eduring submaximal exercise with this incremental cycle ergometry protocol. The reduction in exercise-induced hyperkalemia after training is not the result of altered concentrations of arterial catecholamines. The pathophysiological significance of the increased exercise-induced hyperkalemia in CHF and the mechanisms of improved K+homeostasis with training have yet to be established.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe role of cardiac extrinsic innervation in the regulation of sodium balance and blood pressure is controversial.Methods and ResultsWe performed a double-blind study of endocrine and blood pressure responses to 5 days of low- (LS, 10 mmol/d) and 5 days of high- (350 mmol/d) sodium intake in 12 cardiac transplant recipients, 12 matched healthy subjects, and 12 matched subjects with untreated essential hypertension. In transplant recipients on low sodium, supine blood pressure was 137/94±8/4 (mean+SEM) mm Hg and plasma atrial natriuretic peptide (ANP) was 59.3 ±6.3 pg/mL; on high sodium, blood pressure was 148/97±5/3 mm Hg (P< .05 for systolic pressure versus LS), and ANP was 94.3±10.6 pg/mL (P< .01 versus LS), respectively. Plasma ANP for those on each diet was significantly higher in the cardiac transplant recipients than in healthy or hypertensive controls; relative changes in plasma ANP in changing from low- to high-sodium diet were similar in each group. Urinary sodium excretion by the fifth day of each diet was similar in each group. Suppression of plasma renin activity and aldosterone by high-sodium diet was blunted in cardiac transplant recipients compared with healthy subjects (respectively, plasma renin activity: 1.41±0.30 versus 0.68±0.21 ng. mL−1. hW1,P< .05; aldosterone: 391±35 versus 166±21 pmol/L,P< .05).ConclusionsThese results suggest that extensive denervation of the heart does not result in major abnormalities in regulation of large changes in sodium intake and that intact cardiac innervation is not required for plasma ANP responses to altered sodium intake. Blood pressure after cardiac transplantation is sensitive to reduced sodium intake.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundBefore any new diagnostic test is accepted in clinical practice, such a test should be compared with established diagnostic tools in an appropriately large series of patients encompassing the complete spectrum of challenges to which the test is exposed. The aim of the present study was to assess the relative diagnostic and prognostic accuracies of high-dose dipyridamole echocardiography (two-dimensional echocardiographic monitoring during dipyridamole infusion up to 0.84 mg/kg over 10 hours) versus maximal symptomlimited bicycle exercise ECG test in patients with angina.Methods and ResultsWe studied 429 consecutive in-hospital patients who met the following inclusion criteria: history of chest pain, off antianginal therapy for at least 2 days (1 week p-blockers), no previous myocardial infarction and/or obvious regional left ventricular dyssynergy of contraction akinesis or dyskinesis) at baseline, and acceptable acoustic window under resting conditions. All patients underwent dipyridamole echocardiography and exercise ECG -on different days and in random order -within 1 week of coronary angiography (which was performed independent of test results) and were followed up for 37.8±14 months (range, 1 to 73 months). Criteria of positivity were for dipyridamole echocardiography, a transient regional dyssynergy absent in the baseline examination; for exercise ECG, an ST-segment shift of ≥0.1 mV from baseline; and for coronary angiography, a luminal reduction of ≥75% in at least one major coronary vessel (50% for left main). There were 183 patients without and 246 with coronary artery disease; 132 had one-, 70 had two-, and 44 had three- and/or left main vessel disease. The specificity was higher for dipyridamole echocardiography than exercise ECG (90% versus 51%,P< .001). The overall sensitivity of dipyridamole echocardiography was similar to that of exercise ECG (75% versus 74%,P= NS), with no significant differences in the subset with one- (67% versus 69%,P= NS), two- (79% versus 77%,P= NS), or three- (93% versus 86%,P= NS) vessel disease. During the follow-up, there were 20 deaths, 13 nonfatal myocardial infarctions, and 126 revascularization procedures. In the univariate analysis, dipyridamole resulted in higher χ2values than did exercise stress testing. A Cox forward stepwise survival analysis identified the dipyridamole time as the most powerful prognostic predictor of death (χ2=19.4P< .0001) of all invasive and noninvasive parameters. The dipyridamole time also provided independent and additional prognostic information when it was adjusted for age, diabetes, resting ECG, and exercise stress test according to a modified, interactive stepwise procedure. This is true when death only, death and myocardial infarction, and death, myocardial infarction, and revascularization procedures were considered end points.ConclusionsIn patients with no previous myocardial infarction and good resting left ventricular function, compared with exercise ECG, dipyridamole echocardiography has a similar sensitivity and a higher specificity for the noninvasive detection of angiographically assessed coronary artery disease. Dipyridamole echocardiography also provides information addition to that provided by exercise ECG for predicting death, infarction, and all events when the presence as well the timing, severity, and extension of dipyridamole-induced wall motion abnormalities are considered.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID