摘要:

Background Little information is available to explain why beta -blockers are beneficial in certain patients with congestive heart failure (CHF). Since catecholamines alter immune function, we asked whether beta -blocker treatment leads to enhancement of immune function.Methods and Results Fifteen patients with New York Heart Association class III-IV CHF secondary to dilated cardiomyopathy were titrated to a minimum dose of metoprolol 25 mg BID on a background therapy of digoxin, diuretic, and angiotensin-converting enzyme inhibitors. Cardiac and immunologic studies were done before and 6 months to 1 year after treatment. While these patients served as their own controls, an additional population of patients with heart failure was followed for a similar time period on traditional medications. A panel of seven delayed hypersensitivity skin tests were placed at 6- to 12-month intervals on the patient's forearm. Seventy percent of all CHF patients were anergic (unable to respond to more than 1 antigen). The 30% who could respond averaged 2.2 antigens. After treatment with metoprolol, only 20% remained anergic (P<.001). The 80% of responders averaged 4.2 antigens (P<.001). Additionally, patients treated with metoprolol had an increased percentage of T cells, natural killer cells, and increased interleukin-2 receptor density upon stimulation with concanavalin A. These changes correlated to increases in ejection fraction. Patients not treated with metoprolol remained anergic and had no beneficial immunologic changes.Conclusions It appears that patients with dilated cardiomyopathy who are treated with metoprolol have enhancement of cell-mediated immunity and improvement of T-cell function; these improvements are correlated to improvement in ejection fraction. (Circulation. 1994;90:1774-1780.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background This study was performed to assess the initial results and long-term follow-up of Morrow septal myectomy for patients with hypertrophic obstructive cardiomyopathy (HOCM).Methods and Results We studied 38 consecutive patients with HOCM (age, 13 to 74 years) who underwent a Morrow septal myectomy between 1977 and 1992. There were no perioperative deaths, and the postoperative course was uneventful for all except 2 of the patients. One patient required implantation of a pacemaker due to a complete heart block, and in 1 patient a small ventricular septal defect was caused. Follow-up (mean, 6.8 years) was 100% complete. No patient was reoperated for recurrent HOCM. All except 1 patient experienced a major functional improvement with a decrease of the mean New York Heart Association functional class from 3.0 before operation to 1.5 at follow-up (P<.001). Symptoms persisting during follow-up were angina pectoris in 3 of 22 patients (14%), dyspnea in 6 of 30 patients (20%), dizzy spells in 2 of 12 patients (17%), and syncope in 2 of 10 patients (20%). During follow-up no HOCM related death occurred. All patients were restudied by Doppler echocardiography. The peak gradient in the left ventricular outflow tract decreased from 72+-30 mm Hg (range, 31 to 144 mm Hg) to 6+-4 mm Hg (range, 0 to 20; P<.001). A systolic anterior movement was seen in 8 patients (21%) compared with 32 patients (97%) before the operation (P<.001). The left ventricular outflow tract diameter increased from 17+-3 mm (range, 10 to 23 mm) to 22+-3 mm (range, 15 to 33 mm; P<.001), and the mean subaortic septal thickness decreased from 23+-5 mm (range, 15 to 35 mm) to 15+-6 mm (range, 8 to 30 mm; P<.001).Conclusions Morrow septal myectomy for patients with HOCM is a safe procedure with an excellent clinical and Doppler echocardiographic long-term follow-up. (Circulation. 1994;90:1781-1785.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background During the past half-century, the ECG has been used extensively for the diagnosis of left ventricular hypertrophy. Persons with ECG evidence of left ventricular hypertrophy are at increased risk for the development of cardiovascular disease.Methods and Results Subjects from the Framingham Heart Study with ECG evidence of left ventricular hypertrophy were eligible for this investigation if they were free of cardiovascular disease and did not have complete bundle-branch block or Wolff-Parkinson-White syndrome. Logistic regression analyses of pooled biennial examinations were used to determine risk for cardiovascular disease as a function of baseline voltage (sum of R wave in aVL plus S wave in V3) and repolarization and as a function of serial changes in these ECG features of hypertrophy. The eligible sample consisted of 274 men (mean age, 60 years) and 250 women (mean age, 64 years) who contributed 2660 person-examinations. During follow-up, there were 269 new cardiovascular events. Compared with subjects in the first quartile of voltage at baseline, the age-adjusted odds ratio for cardiovascular disease among subjects in the fourth quartile was 3.08 (95% confidence interval (CI), 1.87 to 5.07) in men and 3.29 (95% CI, 1.78 to 6.09) in women. Compared with a normal repolarization pattern, the presence of severe repolarization abnormalities was associated with an age-adjusted odds ratio of 5.84 (95% CI, 3.55 to 9.62) in men and 2.47 (95% CI, 1.38 to 4.42) in women. Subjects with a serial decline in voltage were at lower risk for cardiovascular disease than were those with no serial change (men: odds ratio after adjusting for age and baseline voltage, 0.46; 95% CI, 0.26 to 0.84; women: odds ratio, 0.56; 95% CI, 0.30 to 1.04). In contrast, those with a serial increase in voltage were at greater risk for cardiovascular disease (men: odds ratio, 1.86; 95% CI, 1.14 to 3.03; women: odds ratio, 1.61; 95% CI, 0.91 to 2.84). Compared with those with no serial change, an improvement in repolarization was associated with a marginally significant reduction in cardiovascular risk in men (odds ratio after adjusting for age and baseline repolarization, 0.45; 95% CI, 0.20 to 1.01). Worsening of repolarization was associated with increased risk for cardiovascular disease in both sexes (men: odds ratio, 1.89; 95% CI, 1.05 to 3.40; women: odds ratio, 2.02; 95% CI, 1.07 to 3.81).Conclusions The results of this investigation suggest that regression of ECG features of left ventricular hypertrophy confers an improvement in risk for cardiovascular disease, whereas serial worsening imposes increased risk. The benefits to be derived from regression of left ventricular hypertrophy must be confirmed in other clinical settings. (Circulation. 1994;90:1786-1793.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Sympathetic excitation characterizes heart failure, but the underlying mechanisms remain unknown. Abnormal baroreflex restraint of sympathetic neural outflow has been proposed, since baroreflexes are known to be abnormal in heart failure. The purpose of this study was to determine if sympathetic activation in humans with heart failure is limited to regions governed by the baroreflexes or is generalized to other regions free from baroreflex control.Methods and Results We report the first direct recordings of skin sympathetic nerve activity (free from baroreflex control) in humans with heart failure and compare simultaneous skin and muscle (baroreflex-dependent) sympathetic peroneal nerve activity in six patients with severe heart failure (mean left ventricular ejection fraction, 0.19+-0.06) and in six age-matched normal control subjects. Although muscle sympathetic nerve activity was markedly increased in heart failure patients (heart failure versus controls, 69+-3 versus 21+-2 bursts per minute; P<.001), skin sympathetic nerve activity was not increased (heart failure versus controls, 12+-1 versus 15+-1 bursts per minute; P=NS).Conclusions The finding that skin sympathetic nerve activity in contrast to muscle sympathetic nerve activity is not increased in heart failure supports the concept that an altered reflex system, such as the baroreflexes, with nonuniform effects on muscle and skin sympathetic nerve activity, underlies sympathoexcitation in heart failure. (Circulation. 1994;90:1794-1798.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background The efficacy of transcatheter ablation of atrioventricular (AV) accessory pathways (APs) located in the posteroseptal region using a right atrial approach and radiofrequency energy was evaluated.Methods and Results Fifty consecutive patients with APs in the posteroseptal region underwent radiofrequency catheter ablation. Manifest preexcitation was present in 36 patients and a concealed AP in 14. In 18 patients (group 1), the ventriculoatrial (VA) interval during orthodromic tachycardia was prolonged by 21+-7 milliseconds (range, 10 to 30 milliseconds) with functional left bundle-branch block. In 16 patients (group 2), functional left bundle-branch block caused no VA interval prolongation. The remaining 16 patients (group 3) had no inducible left bundle-branch block during orthodromic tachycardia. Functional right bundle-branch block was induced in 30 patients with no effect on the VA interval. In group 1, of 14 patients with manifest preexcitation during sinus rhythm, 10 patients had a positive delta wave in lead V1. Of 10 group 2 patients with manifest preexcitation, only 5 had a positive delta wave in lead V1. In group 3, of 12 patients with manifest preexcitation, 7 exhibited a positive delta wave in lead V1. All posteroseptal APs were successfully ablated, and this was achieved via a right atrial approach in 48 patients and left ventricular approach in only 2. Successful sites were at the posteroseptal region of the tricuspid annulus (30 patients), within the terminal 1 cm of the coronary sinus including its ostium (16 patients), and at the inferomedial aspect of the right atrium posterior to the coronary sinus ostium (2 patients). The posteroseptal region of the left ventricle was the site of successful ablation in 2 patients. Six patients with a recurrence of AP conduction required a repeat ablation, with successful results in 5. Thirty-five patients had a complete electrophysiological evaluation 2 to 3 months after their successful ablation and were found to have no functioning AP. In 49 patients with a final successful ablation, no recurrence of symptoms was noted during a mean follow-up period of 12+-9 months. Complications occurring in 3 patients were cardiac tamponade requiring surgical drainage and repair of a right ventricular tear, pericardial effusion with no hemodynamic consequence that spontaneously resolved, and a transient 2:1 atrioventricular block.Conclusions These data suggest that posteroseptal APs are amenable to successful ablation using a right atrial approach. Success was achieved in 47 cases (94%) in this series even though the ECG and/or electrophysiological characteristics of the posteroseptal APs of some patients were suggestive of "left-sided" pathways. (Circulation. 1994;90:1799-1810.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background The autonomic nervous system appears to play an important role in the development of clinical ventricular arrhythmias, and beta -adrenergic sympathetic stimulation may be important in modulating the electrophysiologic effects of class III antiarrhythmic agents. This study prospectively determined the effects of isoproterenol on the frequency-dependent actions of sematilide (a pure class III agent that selectively blocks the delayed rectifier potassium current) and amiodarone (a class III agent with a complex pharmacologic profile) on ventricular repolarization, refractoriness, and conduction.48 hours) dosing with sematilide (455+-5 mg/d (mean+-SEM)) or after 10.5 days of amiodarone loading (1618+-32 mg/d), and (3) during isoproterenol administration (35 ng/kg per minute) to patients receiving sematilide or amiodarone. Electrophysiologic determinations were made at paced cycle lengths of 300 to 500 ms. The two groups were similar in all clinical characteristics. The ventricular action potential duration at 90% repolarization (APD90) was significantly prolonged by sematilide (mean increase, 7+-1%, P<.01 by ANOVA) and amiodarone (mean increase, 12+-1%, P<.001). However, while sematilide-induced APD90prolongation was fully reversed to baseline values during isoproterenol infusion, the APD90in patients receiving amiodarone remained significantly prolonged by a mean of 6+-1% compared with baseline (P=.005). The reduction in the APD90was frequency dependent for both agents, with a greater reduction at longer than shorter paced cycle lengths (P<.02). During isoproterenol infusion the right ventricular effective refractory period (RVERP) in patients receiving sematilide was significantly reduced to mean values of 8+-2% below baseline (P<.05), whereas the RVERP in patients receiving amiodarone remained significantly prolonged by a mean of 7+-1% above baseline values (P=.01). Sematilide and sematilide/isoproterenol had no effect on ventricular conduction. Amiodarone increased the QRS duration by 14+-4% (paced cycle length, 500 ms) to 32+-5% (paced cycle length, 300 ms) compared with baseline values. Isoproterenol attenuated amiodarone-induced QRS prolongation by a mean of 5+-1% (P=.005), without frequency-dependent effects, consistent with isoproterenol-induced increases in the sodium current. During isoproterenol infusion there was a trend for the sustained VT cycle length to be reduced below baseline in patients receiving sematilide (275+-16 versus 298+-55 ms, P=.06), whereas it remained significantly prolonged compared with baseline in patients receiving amiodarone (327+-17 versus 257+-12 ms, P<.001).Conclusions Isoproterenol fully reversed the effects of selective potassium channel block with sematilide on the APD sub 90 and further reduced the RVERP to values significantly below baseline; it partially attenuated but did not fully reverse amiodarone-induced prolongation of the APD90and RVERP, which remained significantly prolonged beyond baseline values. Isoproterenol exerted frequency-dependent effects in both patient groups on the APD90; it modestly attenuated amiodarone-induced conduction slowing without frequency-dependent actions; and the sustained VT cycle length remained significantly prolonged during isoproterenol administration to patients receiving amiodarone but not in those receiving sematilide. These findings may have important clinical implications regarding protection from arrhythmia development in patients receiving pure class III agents or amiodarone. (Circulation. 1994;90:1811-1819.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Reduction in R-wave amplitude immediately after defibrillation shocks in an integrated shock/sense transvenous cardioverter-defibrillator (TCD) lead system has prompted concerns regarding adequate sensing after failed shocks. We therefore studied redetection characteristics for ventricular fibrillation after unsuccessful defibrillation shocks in a TCD system to determine if these observations have clinical relevance.=10 seconds) showed no significant differences in clinical or implantation characteristics when compared with 42 individuals without extended RDT.Conclusions In this integrated shock/sense TCD lead system, unsuccessful shock delivery has no significant effect on redetection of ventricular fibrillation at device implantation or up to 6 months of follow-up, despite an observed reduction in postshock R-wave amplitude. Therefore, the reported reduction in electrogram quality after a shock is of no practical importance because sensing of ventricular fibrillation does not appear to be compromised in this particular TCD system. Whether this applies to other implantable cardioverter-defibrillator pulse generators and lead systems with different sensing characteristics requires further evaluation. (Circulation. 1994;90:1820-1825.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background The powers of the low-frequency (LF) and high-frequency (HF) oscillations characterizing heart rate variability (HRV) appear to reflect, in their reciprocal relationship, changes in the state of the sympathovagal balance occurring during numerous physiological and pathophysiological conditions. However, no adequate information is available on the quantitative resolution of this methodology.Methods and Results We studied 22 healthy volunteers (median age, 46.5 years) who were subjected after a rest period to a series of passive head-up tilt steps randomly chosen from the following angles: 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. From the continuous ECG, after appropriate analog-to-digital conversion, a personal computer was used to compute, with an autoregressive methodology, time and frequency domain indexes of RR interval variability. Spectral and cross-spectral analysis with the simultaneously recorded respiratory signal excluded its contribution to LF. Age was significantly correlated to variance and to the absolute values in milliseconds squared of very-low-frequency (VLF), LF, and HF components. The tilt angle was correlated to both LF and HF (expressed in normalized units (nu)) and to the LF-to-HF ratio (r=.78, -.72, and.68; respectively). Lower levels of correlation were found with HF (in ms[2]) and RR interval. No correlation was present between tilt angle and variance, VLF, or LF (in ms2). Individual analysis confirmed that the use of nu provided the greatest consistency of results.Conclusions Spectral analysis of HRV, using nu or LF-to-HF ratio, appears to be capable of providing a noninvasive quantitative evaluation of graded changes in the state of the sympathovagal balance. (Circulation. 1994;90:1826-1831.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background The antiarrhythmic effects of sodium channel and calcium channel blockers are known to be rate dependent. Little is known about the rate-dependent effect of adenosine on human atrioventricular (AV) nodal conduction. The purpose of this study was to determine whether the negative dromotropic effect of adenosine is dependent on heart rate.Methods and Results Atrial pacing at 20-millisecond increments decreasing stepwise was performed, and the curves that relate the AH interval to the atrial pacing cycle length were analyzed. The change in AV nodal function was evaluated in three protocols: (1) In 8 group 1A and 6 group 1B patients, an intravenous infusion of adenosine at a dose of 140 and 320 micrograms x kg sup -1 x min sup -1 was given, respectively; (2) a bolus injection of a fixed dose of adenosine was given to 12 group 2A patients without and 6 group 2B patients with propranolol (0.1 mg/kg) treatment; and (3) in 12 group 3 patients, the AV nodal function was evaluated after intravenous propranolol (0.05 mg/kg) and after subsequent intravenous aminophylline (loading dose, 5 mg/kg; maintenance dose, 0.9 mg x kg sup -1 x h sup -1). No significant depression of AV nodal function could be demonstrated during intravenous infusion of adenosine. The bolus injection of adenosine could prolong the AH interval, which was dependent on heart rate and more significant at a shorter pacing cycle length. Intravenous propranolol significantly depressed the AV nodal conduction and shifted the curves of the AH interval versus the pacing cycle length to the right. Subsequent intravenous aminophylline shortened the AV nodal conduction time, however, in a rate-independent manner.Conclusions The negative dromotropic effects induced by intravenous bolus injection of adenosine became more pronounced at fast atrial pacing rates. These results indicate that adenosine causes rate-dependent prolongation of AV nodal conduction in humans. (Circulation. 1994;90:1832-1839.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background The time constant of truncated exponential pulses used with implantable defibrillators is determined by the output capacitor size and defibrillation pathway resistance. The optimal capacitor size is unknown.=61 Omega, the DFT was <=15 J for 19% of pathways using monophasic 120- mu F pulses versus 95% for 60- mu F pulses. Similarly, the DFT was <=10 J for 48% of pathways using biphasic 120- mu F capacitors versus 83% for 60- mu F pulses.Conclusions In comparison with conventional 120- mu F capacitors, 60- mu F capacitors had clinically insignificant higher DFTs for low-resistance pathways and clinically important lower DFTs for high-resistance pathways. Optimal capacitance is inversely related to pathway resistance for clinical defibrillation pathways and waveforms. (Circulation. 1994;90:1840-1846.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID