摘要:

BackgroundConventional programmed ventricular stimulation protocols are inefficient compared with more recently proposed protocols. The purpose of the present study was to determine if additional efficiency could be derived from a 6-step programmed ventricular stimulation protocol that exclusively uses four extrastimuli.Methods and ResultsThe subjects were 209 consecutive patients with coronary artery disease and documented sustained monomorphic ventricular tachycardia, nonsustained ventricular tachycardia, aborted sudden death, or syncope. These patients underwent 159 electrophysiological tests in the absence of antiarrhythmic drug therapy and 105 electrophysiological tests in the presence of antiarrhythmic therapy. Programmed stimulation was performed with two protocols in random order in each patient. Both protocols used an eight-beat drive train, 4-s intertrain pause, and basic drive cycle lengths of 350, 400, and 600 ms. The 6-step protocol started with coupling intervals of 290, 280, 270, and 260 ms, which were shortened simultaneously in 10-ms steps until S2 was refractory. The 18-step protocol used one, two and three extrastimuli in conventional sequential fashion. The end points were 30 s of sustained monomorphic ventricular tachycardia, two episodes of polymorphic ventricular tachycardia requiring cardioversion, or completion of the protocol at two right ventricular sites. There was no significant difference in the yield of sustained monomorphic ventricular tachycardia using the two protocols, regardless of the clinical presentation or treatment with antiarrhythmic drugs. Polymorphic ventricular tachycardia occurred with the 18-step protocol twice as frequently as with the 6-step protocol (6% versus 3%,P< .001). The duration of the 18-step protocol was significantly longer than that of the 6-step protocol in patients with inducible ventricular tachycardia (5.5 ± 7 versus 2.3 ± 2 minutes,P< .001), as well as in patients without inducible ventricular tachycardia (25.4 ± 7 versus 6.9 ± 2 minutes,P< .001).ConclusionsA stimulation protocol that exclusively uses four extrastimuli improves the specificity and efficiency of programmed ventricular stimulation without compromising the yield of monomorphic ventricular tachycardia in patients with coronary artery disease.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundNonthoracotomy-implantable cardioverter/defibrillator (ICD) systems may represent a significant advance in the treatment of patients with life-threatening ventricular arrhythmias, but their merits relative to those of the well-established thoracotomy systems remain largely unknown. The objective of this study was to compare the short- and long-term clinical outcomes after attempted ICD implantation via a nonthoracotomy versus thoracotomy approach in similar groups of patients.Methods and ResultsBetween September 1990 and December 1992, 212 consecutive patients underwent attempted ICD system implantation without concomitant cardiac surgery at a single institution. Approach selection was not randomized but rather was based primarily on hardware availability. Primary comparisons of short- and long-term outcome were performed according to the “intention-to-treat” principle. Implantation was attempted via a nonthoracotomy approach in 120 patients (57%) and via a thoracotomy approach in 92 patients (43%). Prior cardiac surgery was more prevalent in the nonthoracotomy patients; otherwise, groups did not differ significantly in terms of prognostically relevant clinical characteristics. Nonthoracotomy implantation was successful in 101 patients (84%). After crossover to thoracotomy implantation (14 patients), the eventual success rate for ICD system implantation was 96% in the nonthoracotomy group. Thoracotomy implantation was successful in 89 patients (97%). Operative mortality was 3.3% in the nonthoracotomy and 4.3% in the thoracotomy groups (P= .73). Nonthoracotomy group patients were less likely to experience postoperative congestive heart failure (6% versus 16%;P= .02) or supraventricular arrhythmia (6% versus 18%;P= .004) and had significantly shorter postoperative intensive care and total hospitalization. Total hospital costs were significantly lower in the nonthoracotomy group ($32,205 versus $37,265;P= .001). After a follow-up of 16 ± 9 months, there were 17 deaths in the nonthoracotomy group (none sudden) and 12 deaths in the thoracotomy group (1 sudden). One- and 2-year Kaplan-Meier survival probabilities were .87 (95% CI, .78 to .91) and .80 (95% CI, .68 to .88) in the nonthoracotomy group and .90 (95% CI, .82 to .95) and .87 (95% CI, .77 to .93) in the thoracotomy group (P= .56; log-rank test).ConclusionsNonthoracotomy ICD implantation is associated with reduced surgical morbidity, postoperative hospital care requirement, and hospital costs and has similar efficacy in preventing sudden death relative to the thoracotomy approach. From these nonrandomized data, it appears that a nonthoracotomy approach should be considered preferable in most patients requiring ICD therapy.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe Cardiac Arrhythmia Suppression Trial (CAST) was designed to test the hypothesis that suppression of ventricular ectopy with antiarrhythmic drugs after a myocardial infarction reduces the incidence of sudden arrhythmic death. Patients in whom ventricular ectopy could be suppressed with encainide, flecainide, or moricizine were randomly assigned to receive either active drug or placebo. The encainide and flecainide arms of the study were discontinued in 1989 (CAST-I) and the moricizine arm in 1991 (CAST-II) because of excess mortality. To explore the mechanisms of these adverse outcomes, we examined the interaction of baseline characteristics with the hazard of therapy with encainide, flecainide, or moricizine compared with their respective placebos.Methods and ResultsCAST-I comprised 755 patients assigned to flecainide or encainide and 743 patients assigned to placebo, whereas in CAST-II, 502 patients received moricizine and 491 patients received placebo. Clinical and laboratory baseline variables of patients receiving active drug and those receiving placebo were similar. In CAST-I patients, there was a significant interaction of active therapy with both all-cause death/cardiac arrest and arrhythmic death/cardiac arrest for non-Q-wave myocardial infarction (total mortality hazard ratios, 1.8 versus 7.9 for Q-wave versus non–Q-wave infarction,P= .03). Ventricular premature depolarization (VPD) frequency ≥ 50/h and heart rate ≥ 74 beats per minute each interacted significantly with total mortality/cardiac arrest only. In the sicker CAST-II patients (ejection fraction ≤ 40%), only diuretic use at baseline interacted significantly with moricizine use for both all-cause death/cardiac arrest and arrhythmic death/cardiac arrest (total mortality hazard ratios, 1.9 versus 0.7 for diuretic use versus no use,P= .01).ConclusionsAlthough active treatment in CAST- I was associated with greater mortality than placebo with respect to almost all baseline variables, the therapeutic hazard was more than expected in patients with non–Q-wave myocardial infarction and (for total mortality) frequent premature VPDs and higher heart rates, suggesting that the adverse effect of encainide or flecainide therapy is greater when ischemic and electrical instability are present. The relative hazard of therapy with moricizine in the sicker CAST-II population was greater in those using diuretics. Thus, although these drugs have the common ability to suppress ventricular ectopy after myocardial infarction, their detrimental effects on survival may be mediated by different mechanisms in different populations, emphasizing the complex, poorly understood hazards associated with antiarrhythmic drug treatment.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundEndothelium-derived nitric oxide is an important modulator of resting vascular tone in animals and humans. However, the contribution of nitric oxide to exercise-induced vasodilation is unknown.Methods and ResultsThe effect ofNG-monomethyl-L-arginine (L- NMMA), an inhibitor of nitric oxide synthesis, on exercise-induced vasodilation was studied in 18 healthy subjects (mean ± SD, 40 ± 10 years; 10 women). Acetylcholine was used to test the efficacy of L-NMMA in inhibiting stimulation of nitric oxide synthesis and sodium nitroprusside to test the specificity of L-NMMA in inhibiting endothelium-dependent vasodilation. Intermittent handgrip exercise and infusions of acetylcholine and sodium nitroprusside were performed during intra-arterial infusion of 5% dextrose (control) and L-NMMA (4 to 16 μmol/min). Forearm blood flow was determined by strain-gauge plethysmography. Forearm oxygen extraction was measured from arterial and venous oxygen saturations. In a separate study, 10 subjects performed exercise during infusions of 5% dextrose, L-arginine (the substrate for nitric oxide production), and D-arginine (the stereoisomer that is not a substrate for nitric oxide production). L-NMMA reduced exercise blood flow by 7 ± 13% (P= .04), increased exercise resistance by 18 ± 20% (P= .02), and increased exercise oxygen extraction by 16 ± 17% (P< .001). The degree of inhibition of acetylcholine-induced vasodilation with L-NMMA correlated positively with the degree of reduction in exercise blood flow (r = .55,P= .02). The highest dose of L-NMMA (16 μmol/min) produced the greatest effect; exercise blood flow was reduced by 11 ± 14% (P= .03), and vascular resistance increased by 26 ± 23% (P= .005). L-NMMA did not affect the forearm vasodilation produced by sodium nitroprusside. Exercise blood flow, resistance, and oxygen extraction were not significantly modified by infusions of either L- or D-arginine.ConclusionsInhibition of nitric oxide synthesis reduces exercise-induced vasodilation in the human forearm, indicating that nitric oxide plays a role in exercise-induced vasodilation. Increased availability of nitric oxide substrate does not enhance exercise-induced vasodilation in healthy subjects. These findings have important implications for disease states in which endothelium-derived nitric oxide production is impaired.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundNonmodulation seems to represent an inheritable trait characterized by abnormal angiotensin-mediated control of aldosterone release and renal blood supply and salt-sensitive hypertension. Recently, we demonstrated that atrial natriuretic peptide (ANP) response to angiotensin II also is altered in nonmodulators. Moreover, an abnormal ANP response to acute volume expansion has been shown by others in hypertensive patients displaying some features of nonmodulators. These data induced us to hypothesize that nonmodulators. These data induced us to hypothesize that nonmodulation could be characterized by an abnormal ANP response to saline load.Methods and ResultsForty-three essential hypertensive men were subdivided into low-renin patients (n = 12), nonmodulators (n = 15), and modulators (n = 16) according to their renin profile and ability to modulate aldosterone andp-aminohippurate clearance responses to a graded angiotensin II infusion (1.0 ng.kg-1·min−1and 3.0 ng·kg−1.min−1for 30 minutes each) on both a low- (10 mmol Na+per day) and a high- (210 mmol Na+per day) Na+intake. The intravenous saline load (0.25 mL.kg−1−min−1for 2 hours) performed on a low-Na+diet increased plasma ANP levels in low-renin (from 14.30 ± 4.68 to 23.30 ± 7.52 fmol/mL at 120 minutes,P< .05) and modulating patients (from 10.95 ± 3.55 to 18.21 ± 5.42 fmol/mL at 120 minutes,P< .05), whereas it did not change the hormone levels in nonmodulators (from 10.77 ± 3.25 to 13.83 ± 5.70 fmol/mL at 120 minutes,P= NS). When patients switched from a low- to a high-NaCl diet, plasma ANP levels increased significantly in all groups. However, when the saline load was repeated on a high-NaCl intake, ANP levels increased in both low-renin and modulating patients (P< .05), whereas it failed to increase in nonmodulators.ConclusionsNonmodulating hypertensive patients showed a reduced ANP response to saline infusion in the presence of a normal increase of plasma ANP with dietary NaCl load. The impaired ANP response to saline infusion could be due to a different distribution of volume load and contribute to determining the reduced ability to excrete sodium that is commonly described in nonmodulators.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThis study was undertaken to assess whether ambulatory blood pressure (BP) in a population of stage I hypertensive individuals was lower in the subjects performing regular exercise training.Methods and ResultsThe study was carried out in 796 young hypertensive patients (592 men) who had never been treated who took part in the HARVEST trial. The diagnosis of stage I hypertension was made on the basis of six office BP measurements. Subjects underwent noninvasive 24-hour ambulatory BP monitoring, 24-hour urine collection for catecholamine assessment, and echocardiography (n = 457). They were classified as exercisers if they reported at least one session of aerobic sports per week and as nonexercisers if they did not engage regularly in sports activities. Age (P< .0001), body mass index (P= .002), 24-hour heart rate (P< .0001), alcohol intake (P= .02), smoking (P= .02), and norepinephrine output (P= .04) were lower in the active (n = 153) than the inactive (n = 439) men. Physically active men exhibited a lower 24-hour and daytime diastolic BP than the inactive men, while there were no group differences in office BP or in nighttime diastolic BP and in ambulatory systolic BP. The between-group ambulatory diastolic BP difference remained statistically significant after adjustment for age, body mass index, alcohol intake, and smoking (P< .0001). Of the nonexercisers, 46.2% were confirmed hypertensives, compared with only 26.8% of the exercisers (P< .0001), on the basis of daytime diastolic BP. Echocardiographic left ventricular dimensional and functional indexes were similar in the two groups of men. Similar findings were shown by the 16 women who engaged in aerobic sports.ConclusionsThese data suggest that participation in aerobic sports may attenuate the risk of hypertension in young subjects whose office BP is in the stage I hypertensive range at office measurement.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundPlatelets play an important role in the pathogenesis of cardiovascular diseases. It is also noticed that on one hand, regular exercise can reduce the risk of cardiovascular diseases, and on the other hand, vigorous exercise provokes sudden cardiac death. We therefore hypothesize that various intensities of exercise may affect platelet function differently.Methods and ResultsStrenuous and moderate exercise (about 50% to 55% of peak oxygen consumption, VO2peak) on a bicycle ergometer in 10 sedentary and 10 physically active healthy young men was executed on two separate occasions. Blood samples were collected before and immediately after exercise. A newly designed tapered parallel plate chamber was used to assess platelet adhesiveness. Platelet aggregation induced by ADP was evaluated by the percentage of reduction in single platelet count. β-Thromboglobulin (β-TG) and platelet factor 4 (PF4) were measured by ELISA. In addition, a similar study on 5 patients with stable angina were also conducted. Our results showed that (1) in the sedentary healthy group, platelet adhesiveness and aggregation were increased by strenuous exercise and depressed by moderate exercise; (2) in the active healthy group, platelet adhesiveness and aggregation were enhanced by severe exercise, whereas only aggregation was decreased by moderate exercise; (3) in the patients with stable angina, platelet adhesiveness and aggregation were enhanced by strenuous exercise and adhesiveness was suppressed by moderate exercise; (4) the degree of hemoconcentration induced by acute exercise tended to be related to the severity of exercise in all subjects; and (5) although severe exercise elevated β-TG and PF4, there were no significant changes in β-TG, PF4, and the ratio of β-TG to PF4 in healthy subjects after exercise.ConclusionsIt is concluded that platelet adhesiveness and aggregability may be sensitized by strenuous exercise in both healthy subjects and patients with stable angina. In contrast, platelet function can be suppressed significantly by moderate exercise in the healthy and tends to be depressed in patients with stable angina. The former may increase the risk of cardiac arrest and the latter may protect us from cardiovascular diseases. In addition, the effects of acute exercise tend to be more pronounced in the sedentary than in the active.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundWe wished to determine the role of NO in exercise-induced metabolic forearm vasodilation.Methods and ResultsYoung healthy volunteers (n = 11) underwent static handgrip exercise (4 to 5 kg, 3 minutes). Forearm blood flow (FBF) measured by strain plethysmography increased from 4.1 ± 0.7 mL.min−1·100 mL−1at rest to 9.8 ± 1.2 mL·min−1·100 mL−1immediately after exercise and gradually decreased thereafter. Exercise was repeated after intrabrachial artery infusion ofNG-monomethyl-L-arginine (L-NMMA) at 4.0 μmol/min for 5 minutes. L- NMMA did not alter blood pressure and heart rate. L-NMMA decreased FBF at rest to 2.9 ± 0.4 mL.min-1.100 mL−1(P< .01), peak FBF immediately after exercise to 7.2 ± 0.7 mL.min−1.100 mL−1(P< .01), and FBF during the mid to late phase of metabolic vasodilation (P< .01). Calculated oxygen consumption during peak exercise was comparable before and after L-NMMA. Intra-arterially infused L-arginine (10 mg/min, 5 minutes) reversed the inhibitory effect of L-NMMA. To determine the effect of the decrease in resting FBF on exercise-induced hyperemia, we normalized FBF after exercise by resting FBF. The percent increases in FBF after exercise from resting FBF were similar before and after L-NMMA. Furthermore, we examined the effect of intra-arterially infused angiotensin II on FBF at rest and after exercise (n = 7). Angiotensin II decreased FBF at rest from 3.1 ± 0.3 to 1.8 ± 0.3 mL.min−1.100 mL−1(P< .01), peak FBF after exercise from 8.1 ± 0.5 to 5.6 ± 0.5 mL.min−1.100 mL−1(P< .01), and FBF during the mid to late phase of metabolic vasodilation. The effects of L-NMMA and angiotensin II on FBF at rest and exercise were similar.ConclusionsOur results suggest that L-NMMA decreased FBF after exercise largely by decreasing resting FBF. These results suggest that NO may not play a significant role in exercise-induced metabolic arteriolar vasodilation in the forearm of healthy humans.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundAortic stenosis is the most common valvular lesion occurring among elderly patients and has become extremely frequent because of changing demographics in industrialized countries. Surgical risk after the age of 70 has increased. The increasing older age of patients having surgery justifies an analysis of mortality predictive factors.Methods and ResultsBetween 1976 and February 1993, we performed 2871 operations for aortic stenosis. This study concerns 675 patients (278 men and 397 women) who were ≥ 75 years old. Mean age was 78.5 ± 3 years. Associated lesions were found in 226 patients. A bioprosthesis was implanted in 632 patients (93.6%). Concomitant surgical procedures were performed in 133 patients. Surgical mortality was 12.4% (84 deaths). A longitudinal analysis has been carried out over four successive time periods to evaluate population evolution during these 17 years. Statistical analysis was performed on 46 variables. Multivariate analysis found age (P< .0001), left ventricular failure (P< .0001), lack of sinus rhythm (P< .01), and emergency status (P< .02) to be presurgical independent predictive factors of mortality.ConclusionsRisk-reducing strategy should both favor relatively early surgery to avoid cardiac failure and emergency situations and pay careful attention to the use of myocardial protection and cardiopulmonary bypass. Indications for surgery should remain broad since analysis failed to determine specific high-risk groups to be eliminated, and surgery remains the only treatment for aortic stenosis.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundLeft ventricular function is the main predictor of long-term survival in patients with coronary artery disease. In patients with impaired left ventricular function after myocardial infarction, end-systolic volume is a better predictor than the global ejection fraction. We analyzed long-term follow-up of patients with impaired left ventricular function undergoing coronary artery bypass graft surgery to evaluate preoperative predictors of survival.Methods and ResultsConsecutive patients with ejection fractions ≤ = 40% (n = 193) who had undergone surgical revascularization were followed to assess the predictive value of preoperative baseline characteristics and catheterization findings for long-term survival. Patients were followed for 133 ± 30.7 months. At the time of surgery, patient age was 56 ± 7.9 years and 169 patients (87.6%) had a history of previous myocardial infarction. Thirty-one patients (16%) were female. The ejection fraction was 32 ± 7%, and the end-systolic volume was 147.4 ± 52.6 mL. One hundred sixty-four patients (84.9%) had three-vessel disease, and 44 (22.8%) had a left main stenosis with > 50% diameter loss. Follow-up was complete in 99%. Fourteen patients died (7.3%) within the first 30 days after surgery. Twelve-month actuarial survival was 86%, 4-year survival was 80%, and 10-year survival was 40%. Predictors of poor long-term survival on multivariate analysis were end-systolic volume index (χ 2 = 14.02,P= .002), number of previous myocardial infarctions (χ2= 6.47,P= .001), preoperative stenosis score (χ2= 4.97,P= .02), and age at the time of surgery (χ2= 4.45,P= .03).ConclusionsEnd-systolic volume index is the major predictor of survival after coronary artery bypass graft surgery in patients with impaired left ventricular function. Strategies to prevent ventricular dilatation, such as angiotensin-converting enzyme inhibitors, may improve the long-term outcome in these patients.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID