Optimal cut-off values for obesity: using simple anthropometric indices to predict cardiovascular risk factors in Taiwan.

BACKGROUND: The increased health risks associated with obesity have been found to occur in Asians at lower body mass indices (BMIs). To determine the optimal cut-off values for overweight or obesity in Taiwan, we examined the relationships between four anthropometric indices and cardiovascular risk factors. METHODS: The data were collected from four health-screening centers from 1998 to 2000 in Taiwan. Included were 55 563 subjects (26 359 men and 29 204 women, mean age=37.3+/-10.9 and 37.0+/-11.1 y, respectively). None had known major systemic diseases or were taking medication. Individual body weight, height, waist circumference (WC), and a series of tests related to cardiovascular risk (blood pressure, fasting plasma glucose, triglycerides, total cholesterol, low- and high-density lipoprotein cholesterol) were assessed and their relationships were examined. Receiver operating characteristic (ROC) analysis was used to find out the optimal cut-off values of various anthropometric indices to predict hypertension, diabetes mellitus and dyslipidemia. RESULTS: Of the four anthropometric indices we studied, waist-to-height ratio (WHtR) in women was found to have the largest areas under the ROC curve (women=0.755, 95% CI 0.748-0.763) relative to at least one risk factor (ie hypertension or diabetes or dyslipidemia). The optimal cut-off values for overweight or obesity from our study in men and women showed that BMIs of 23.6 and 22.1 kg/m(2), WCs of 80.5 and 71.5 cm, waist-to-hip ratios (WHpR) of 0.85 and 0.76, and WHtR of 0.48 and 0.45, respectively, may be more appropriate in Taiwan. CONCLUSIONS: WHtR may be a better indicator for screening overweight- or obesity-related CVD risk factors than the other three indexes (BMI, WC and WHpR) in Taiwan. Our study also supported the hypothesis that the cut-off values using BMI and WC to define obesity should be much lower in Taiwan than in Western countries.

Four anthropometric indices and cardiovascular risk factors in Taiwan.

OBJECTIVE: To examine the relationships between four anthropometric measurements and cardiovascular risk factors in Taiwan. DESIGN: The data was collected from four nationwide health screen centers in Taiwan from 1998 to 1999. SUBJECTS: A total of 38 556 subjects: 18 280 men and 20 276 women, mean age=37.0+/-11.1 y. None had any known major systemic diseases or were currently on medication. MEASUREMENTS: Individual body weight, height, waist circumference (WC), and cardiovascular risk factors (blood pressure, fasting plasma glucose, triglycerides, total cholesterol level, low-density and high-density-lipoprotein cholesterol level) were assessed and their relationships were examined. RESULTS: In both sexes, with increasing body mass index (BMI), WC, WHpR (waist-to-hip ratio) and WHtR (waist-to-height ratio), there were significantly higher risks of hypertension, impaired fasting glucose, diabetes and dyslipidemia (P<0.001) in almost all age groups. In the age groups older than 65, however, the relationships were statistically inconsistent. CONCLUSIONS: In Taiwan, the four anthropometric indexes (BMI, WC, WHpR, WHtR) are closely related to cardiovascular risk factors.

Hybrid therapy for ventricular arrhythmia management.

Optimum arrhythmia management has evolved to couple ICD therapy with catheter ablative and drug therapy to attempt to eliminate or reduce arrhythmia risk. No longer should the clinician approach such therapy as a choice among single alternative strategies only. Optimum patient management includes not only recognition of the indications and benefits of such hybrid therapy but also a complete understanding of potential pitfalls of such therapy.

Radiofrequency catheter ablation of postinfarction ventricular tachycardia: long-term success and the significance of inducible nonclinical arrhythmias.

BACKGROUND: Radiofrequency (RF) catheter ablation is effective therapy for monomorphic ventricular tachycardia (VT) in patients without structural heart disease. In patients with postinfarction VT; however, this procedure has been used predominantly as adjunctive therapy, targeting only the patient's clinically documented arrhythmia. By targeting all inducible, sustained VT morphologies, we sought to determine the utility of RF catheter ablation as a primary cure in patients who present with hemodynamically tolerated VT. METHODS AND RESULTS: RF ablation was attempted in 35 patients with a previous myocardial infarction and recurrent, hemodynamically tolerated VT. A mean of 3.9+/-2.7 VTs were induced per patient (range, 1 to 10). The clinically documented arrhythmia was successfully ablated in 30 of 35 patients (86%), and on follow-up electrophysiological testing, 11 patients had no inducible VT and were discharged without other therapy. Nineteen patients had inducible "nonclinical" arrhythmias on follow-up testing, and the majority underwent cardiac defibrillator implantation. Freedom from recurrent arrhythmias, including sudden death, was 91% in patients without inducible VT and 53% in patients with persistently inducible "nonclinical" arrhythmias (P<.05; mean follow-up, 17+/-12 and 12+/-11 months, respectively). CONCLUSIONS: In patients with well-tolerated VT, RF catheter ablation may be useful as a primary cure if no other ventricular arrhythmias are inducible on follow-up testing. Ablation of all hemodynamically tolerated arrhythmias should be attempted in patients with multiple inducible VT morphologies because of the high rate of recurrence of unablated VTs in these patients.

Inappropriate pauses during bradycardia pacing in a third-generation implantable cardioverter defibrillator.

Many ICD devices have the capability for back up bradycardia pacing. Because of the use of a single sensing algorithm for both bradycardia and tachycardia functions, they may be prone to certain "sensing errors." Following implantation of an ICD in a patient with long QT syndrome, "inappropriate" pauses were noted during bradycardia pacing, which were exactly twice the programmed pacing cycle length. This was due to an automatic increase in the device's sensitivity during pacing, a characteristic of the automatic gain control of this particular ICD. Proper recognition of this ICD's special features, known as "lower threshold crossing," allowed noninvasive rectification of the problem and prevented these pauses.

The effects of isoproterenol on the cardiac conduction system: site-specific dose dependence.

INTRODUCTION: Isoproterenol is used to assess and facilitate AV nodal conduction, and thus potentiate the induction of supraventricular arrhythmias. It is commonly administered in increasing doses until a predetermined decrease in sinus cycle length, usually 20% to 30%, occurs. This regimen may result in undesirable side effects. We have observed that effects of isoproterenol on the AV node may occur prior to achieving the target sinus cycle length. The purpose of this study was to determine whether the sinus and AV nodes have equal sensitivity to isoproterenol. METHODS AND RESULTS: Thirty-eight consecutive patients, who underwent electrophysiologic evaluation for a variety of indications, were given incremental doses of isoproterenol at 0.007, 0.014, 0.021, and 0.028 microgram/kg per minute. Sinus cycle length and AV node function were assessed at baseline and after 5 minutes at each dose. The percent change from baseline in AV node function was compared with the change in sinus cycle length at each dose interval. Significantly greater decreases were observed in the anterograde and retrograde AV nodal Wenckebach cycle length (P < 0.0001) than in the sinus cycle length at the lowest isoproterenol dose (0.007 microgram/kg per min). These differences were not apparent at higher doses. A sustained supraventricular tachycardia was inducible in 15 of 38 patients in the presence of isoproterenol, of which 40% occurred at the lowest dose. CONCLUSIONS: The AV node is more sensitive than the sinus node to the effects of isoproterenol. Lower doses of isoproterenol than those commonly used may often facilitate the induction of a supraventricular tachyarrhythmia, thus reducing side effects.

Primary ablation of atrial flutter and atrial fibrillation.

Direct treatment of atrial flutter and atrial fibrillation--that is, attempting to prevent arrhythmia recurrences by ablating atrial tissue--has been a challenge because of uncertainty about the location of optimal target tissues as well as the amount of atrial tissue requiring destruction to effect cure. Advances have yielded success rates for ablation of the common form of atrial flutter comparable to those for other types of supraventricular tachycardia and provide reason for optimism about the use of catheter techniques, to treat atrial fibrillation definitively. This article discusses some of these advances as well as the current status of catheter ablation for atrial flutter and atrial fibrillation and, finally, what the future may bring.

Eliminating bradyarrhythmias after orthotopic heart transplantation.

BACKGROUND: Bradycardia and sinus node dysfunction are common causes of early postoperative morbidity in orthotopic heart transplant recipients and frequently require the use of chronotropic drugs or permanent pacemakers. Several causes have been postulated, including surgical trauma to the sinus node and its blood supply. We sought to eliminate sinus node dysfunction and postoperative bradyarrhythmias by altering the orthotopic heart transplantation technique. METHODS AND RESULTS: Seventy orthotopic heart transplant recipients underwent electrophysiological testing of sinus node function a mean of 9 +/- 3 days after surgery. Standard (atrial anastomosis) orthotopic heart transplantation was performed in 33 patients; total (bicaval anastomosis) heart transplantation was performed in 37 patients. Abnormalities of sinus node function were present in 14 of 33 patients (42%) undergoing standard orthotopic heart transplantation compared with 2 of 37 patients arrhythmia (5%) in whom total heart transplantation was performed (P < .005). The resting sinus heart rate of patients with a normal sinus rhythm was also significantly higher in the total heart transplantation group (90 +/- 12 versus 83 +/- 14 bpm, P < .05). Coronary angiography was performed before discharge in 63 patients. Eleven were found to have an abnormal sinoatrial nodal artery, and 7 of these patients also had evidence of sinus node dysfunction (P < .005). CONCLUSIONS: Surgical trauma to the donor sinus node and/or its blood supply is a significant cause of sinus node dysfunction in the orthotopic heart transplant recipient. By use of a bicaval anastomotic technique, the incidence of and need for treatment of postoperative bradyarrhythmias can be significantly reduced.

Compatibility of a nonthoracotomy lead system with a biphasic implantable cardioverter-defibrillator. Cadence-Endotak 60-Series IDE investigators.

This prospective multicenter study was conducted under the Food and Drug Administration Investigational Device Exemption to evaluate the safety and efficacy of the combination of the Cadence implantable defibrillator (Ventritex, Inc.) and 60-series Endotak C leads (Cardiac Pacemakers, Inc.). Implantation was attempted in 148 patients with hemodynamically compromising ventricular tachycardia or fibrillation (VF), or with pace-terminable ventricular tachycardia. The system was successfully implanted in 97% of patients, with 96% of implants in a transvenous-lead-alone configuration. At implantation, the defibrillation threshold was 455 +/- 94 V (14 +/- 6 J) for lead-alone patients and 532 +/- 40 V (19 +/- 3 J) for those requiring a subcutaneous patch. VF conversion efficacy was reconfirmed in patients who underwent a 3-month chronic induction study. The system successfully detected all 763 induced arrhythmias and terminated 99.5% of them; after system modification, successful conversion was demonstrated in the 2 patients who initially had induced episodes requiring external defibrillation (1 lead revision; 1 reprogramming). All spontaneous episodes were terminated with an implantable-cardioverter defibrillator. Postshock VF redetection times were significantly shorter than initial detection times (4.5 +/- 1.8 seconds detection, 2.1 +/- 0.7 seconds redetection; p<0.0001). During an 8-month mean follow-up (range 1 to 31 months), 2 unwitnessed deaths were classified as sudden cardiac deaths, and 11 patients experienced a total of 12 complications, none of which was associated with the Cadence-Endotak combination.

Efficacy of antitachycardia pacing in patients presenting with cardiac arrest.

The efficacy of antitachycardia pacing (ATP) incorporated into implantable cardioverter defibrillators (ICDs) was assessed in 29 consecutive survivors of cardiac arrest, not attributable to acute myocardial infarction, ischemia, or drug and electrolyte effects. The cohort included 25 men and 4 women with a mean age of 65 years and a mean left ventricular ejection fraction of 29%. Seventeen patients had coronary artery disease, 11 had nonischemic dilated cardiomyopathy, and 1 had long QT syndrome. Programmed stimulation yielded monomorphic ventricular tachycardia (VT) in 17 patients, polymorphic VT in 6, and no inducible VT in 6. During a mean follow-up of 22 months, a total of 91 episodes of monomorphic VT occurred, 73 of which were successfully pace terminated (83%). Monomorphic VT amenable to pace termination recurred only in the group that had this arrhythmia inducible. The recurrent arrhythmias in the 12 patients having either no inducible VT or polymorphic VT were all rapid VTs, having a cycle length < 220 ms; and therefore, not amenable to pace termination. These results suggest that ATP incorporated into ICDs is useful in survivors of cardiac arrest and may significantly reduce the number of shocks that these patients would otherwise receive. Programmed stimulation may also help to define those patients who would receive the maximum benefit from ATP.

Radiofrequency ablation of a supraventricular tachycardia due to interatrial conduction from the recipient to donor atria in an orthotopic heart transplant recipient.

Interatrial conduction of recipient atrial tachycardia to the donor atria of an orthotopic heart transplant recipient resulted in a unique cause of supraventricular tachycardia. An electrophysiologic study was performed, and the recipient atria was found to be in an atrial tachycardia, cycle length of 210 msec, with periods of both 2:1 and 1:1 conduction to the donor atria resulting in a donor atrial cycle length of 420 msec and 210 msec, respectively. The site of interatrial conduction was mapped to the right atrial suture line, along the atrial free wall, and was successfully disrupted with radiofrequency energy. Arrhythmias of a similar mechanism may also be observed in other postsurgical patients.

Electrophysiologic effects of intravenous aminophylline in heart transplant recipients with sinus node dysfunction.

BACKGROUND: Sinus node dysfunction has been reported to occur in up to 50% of orthotopic heart transplant recipients, and oral theophylline has been used in an attempt to limit the morbidity associated with this abnormality. The purpose of this study was to evaluate the electrophysiologic effects of methylxanthines on sinus node function. METHODS: Sinus node testing performed in 26 patients before and after the infusion of 6 mg/kg of aminophylline. Thirteen of these patients had abnormal sinus node function at baseline, and thirteen had normal sinus node function. Sinus node dysfunction was diagnosed by a rhythm other than sinus in five patients, a prolonged corrected sinus node recovery time in two patients, and the presence of a secondary pause in six patients. RESULTS: In patients with abnormal sinus node function a significant decrease was observed in the sinus node recovery time (-14% +/- 5%) and corrected sinus node recovery time (-33% +/- 25%) in response to aminophylline; however, neither parameter was normalized. A decrease in the sinus cycle length (-6% +/- 8%) was not statistically significant. In patients with normal sinus node function, a significant decrease was seen in both the sinus node recovery time (-9% +/- 7%) and sinus cycle length (-9% +/- 4%). The corrected sinus node recovery time decreased by 4% +/- 28% in patients with normal conditions but was not significant. Overall, aminophylline resolved the underlying sinus node abnormality in only one of thirteen patients with abnormal sinus node function. CONCLUSIONS: This study suggests that the use of theophylline in patients with marked sinus node dysfunction may not decrease their risks for subsequent bradycardic events.

Radiofrequency catheter ablation of an atriofascicular pathway during atrial fibrillation: a case report.

INTRODUCTION: A male patient with an atriofascicular pathway underwent catheter ablation of the atriofascicular pathway during atrial fibrillation. METHODS AND RESULTS: The patient had preexcited atrial fibrillation both clinically and repeatedly during electrophysiologic study. A preexcited tachycardia with a 1:1 AV relationship and regular RR intervals was also induced. Catheter ablation of the atriofascicular pathway could only be performed during persistent atrial fibrillation, based on mapping of the pathway's insertion into the right bundle branch. Following successful ablation and cardioversion to sinus rhythm, a regular QRS tachycardia (atrioventricular [AV] nodal reentry) having the same rate, atrial activation sequence, and His-atrial time as the regular preexcited tachycardia noted preablation was initiated. An AV nodal slow pathway modification eliminated this tachycardia. Neither atrial fibrillation nor AV nodal reentry has recurred on follow-up. CONCLUSION: This is the first report of atriofascicular mapping and ablation performed exclusively during atrial fibrillation and illustrates the utility of mapping the pathway's ventricular insertion. Other unusual features ("bystander" pathway activation during AV nodal reentry, possible role of the pathway in genesis of atrial fibrillation) are discussed.

Radiofrequency ablation of Wolff-Parkinson-White syndrome in a donor heart after orthotopic heart transplantation.

Orthotopic heart transplantation was performed in a 65-year-old man with a donor heart with Wolff-Parkinson-White Syndrome. An electrophysiologic study performed 7 days after transplantation showed a left-lateral accessory pathway that exhibited only anterograde conduction. Radiofrequency ablation of the bypass tract was successfully performed, and no evidence of recurrence was found at 12 months' follow-up. We suggest that potential donors with known electrophysiologic abnormalities that are amenable to catheter ablation techniques should be considered for orthotopic heart transplantation, thus broadening the potential donor pool.

Comparison of simultaneous versus sequential defibrillation pulsing techniques using a nonthoracotomy system.

The defibrillation threshold (DFT) using simultaneous (SIML) versus sequential (SEQ) pathways for shock delivery was compared in 16 patients with an implanted cardioverter defibrillator. All patients had three-lead nonthoracotomy systems (NTL) using a left chest subcutaneous patch, a right ventricular endocardial lead, and a lead in the coronary sinus (n = 5) or superior vena cava (n = 11). The DFT were determined 2-44 days (17 +/- 17 days) after implantation. The DFT was defined as the lowest energy shock that resulted in successful defibrillation. The first pathway tested was SIML in 12 and SEQ in 4 patients with output beginning at or above the intraoperative DFT, routinely 18 J. The second pathway was tested beginning 2-4 J above the DFT of the first tested pathway. All shocks were delivered in 2-4 J decrement or increment steps. The SEQ pathway shocks resulted in a significantly lower DFT than SIML pathway shocks (14 +/- 6 vs 18 +/- 6 J; P < 0.01). There was no difference in the time delay after ventricular fibrillation initiation before shock delivery for the successful defibrillation between SIML versus SEQ pathways (7 +/- 2 secs for both pathways). In 7 of 16 patients, defibrillation using SEQ pathway resulted in a > 5 J lowering of DFT, while only one patient had > 5 J lowering of DFT using SIML shocks (P < 0.05). These results have important implications for selecting the optimal pathway for implantable cardioverter defibrillator therapy with a multilead NTL system.

Early postoperative increase in defibrillation threshold with nonthoracotomy system in humans.

The stability of the defibrillation threshold (DFT) early after implantation of an implantable cardioverter defibrillator was evaluated in 15 patients. All but one patient had a three lead nonthoracotomy system using a subcutaneous patch, a right ventricular endocardial lead, and a lead in coronary sinus (n = 5) or superior vena cava (n = 9). Shocks were delivered using simultaneous in nine, sequential in three, and single pathway (coronary sinus not used) in one patient. DFTs were measured at implant (n = 15), 2-8 days postoperation (postop, n = 15), and 4-6 weeks later (n = 8). The DFT was defined as the lowest energy shock that resulted in successful defibrillation. The DFT was assessed with output beginning at 18 joules or 2-4 joules above the implant DFT. All shocks were delivered in 2- to 4-joule increments or decrements. DFTs were significantly higher postoperatively than DFTs at implant (22.7 +/- 7.0 J vs 16.9 +/- 3.9 J; P < 0.05). Eight of 15 patients had DFT determined at all three study periods. In these patients, DFT increased at postop (22.8 +/- 8.3 J vs 16.4 +/- 3.9 J at implant; P < 0.05) and returned to baseline at 4-6 weeks (16 +/- 7.1 J vs 16.4 +/- 3.9 J at implant; P = N.S.). Thus, in patients with a multilead nonthoracotomy system, a DFT rise was observed early after implant. The DFT appears to return to baseline in 4-6 weeks. These results have important implications for programming energy output after implantable cardioverter defibrillator implantation.

Work-up and management of patients with sustained and nonsustained monomorphic ventricular tachycardias.

The approach to patients with hemodynamically-stable sustained monomorphic ventricular tachycardia (VT) must be individualized. The clinical outcome is critically dependent on the type and degree of underlying heart disease, symptoms at presentation, inducibility at electrophysiology study, and responses to antiarrhythmic drugs. Various methods for assessing therapeutic efficacy and both pharmacologic and nonpharmacologic therapies are discussed. The majority of patients with nonsustained VT have no symptoms directly attributable to this arrhythmia that is associated with an increased risk for sudden death in certain patients with coronary artery disease and hypertrophic cardiomyopathy. The optimal means to prophylax against sudden death in these patients is not presently clear, but prospective trials are underway to evaluate this problem.

Is standardization of left ventricular chamber elastance necessary?

Because of the relation between left ventricular (LV) chamber elastance and heart size, it has been hypothesized that maximum time-varying elastance (Emax) must be standardized to differentiate between preserved and depressed LV systolic performance. To test this hypothesis, we studied 66 patients, of whom 25 had a normal LV, 20 had aortic regurgitation, 14 had mitral regurgitation, and seven had cardiomyopathy, with micromanometer-determined LV pressures and radionuclide angiograms during multiple LV loading conditions. Multiple regression analysis established that Emax was independently related to LV end-diastolic volume (r = -0.69). When the Emax and LV end-diastolic volume (EDV) data from all patients were plotted, a curvilinear relation was evident. Data transformation to the base e identified two distinct linear relations, one in the normal patients of lnEmax = -0.60 (lnEDV) +4.34 (r = -0.67, p less than 0.001); and one in the patients with cardiac pathology of lnEmax = -1.06 (lnEDV) +6.12 (r = -0.73, p less than 0.001), which differed from each other (p less than 0.01). When a mathematical standardization was applied to these data to eliminate the independent contribution of heart size to the reduction in lnEmax, the normal patients had a standardized lnEmax versus lnEDV slope of 0, whereas that in the patients with cardiac pathology remained negative and continued to differ from that in the normal patients (p less than 0.001). Dichotomization of patients with cardiac pathology into those with preserved and depressed LV chamber elastance by lnEmax or standardized lnEmax provided highly concordant data (k = 0.73, p less than 0.001). Moreover, the estimated contribution of LVEDV to the reduction in Emax in patients with cardiac pathology averaged only 14 +/- 7%. We conclude from these data that LV chamber elastance calculated with radionuclide angiography has an independent relation with LVEDV, that a mathematical standardization of Emax for heart size does not significantly alter the dichotomization of patients with cardiac pathology into those with preserved and depressed LV systolic performance, and that heart size makes a relatively small contribution to the reduction in this index of LV systolic performance. Thus, standardization for heart size may not be necessary to identify whether preserved or depressed LV chamber elastance exists in an individual adult patient with cardiac pathology compared with normal adult patients.

Alterations in left ventricular relaxation during atrioventricular pacing in humans.

To determine whether the asynchronous left ventricular contraction-relaxation sequence that exists during right ventricular pacing alters left ventricular relaxation, measurements of both the maximal rate of decline of left ventricular pressure (peak negative dP/dt) and the time constant of left ventricular relaxation were obtained during atrial and atrioventricular (AV) pacing in 25 patients referred for diagnostic cardiac catheterization. Heart rate was maintained at 10 to 15 beats/min above the sinus rate at rest, and relaxation was assessed during atrial pacing, AV pacing and repeat atrial pacing. The patients were classified into two groups. Group 1 included 10 patients with normal left ventricular systolic function at rest (ejection fraction greater than 0.55) and without evidence of prior myocardial infarction. Group 2 included 15 patients with a depressed left ventricular ejection fraction or akinesia of one or more left ventricular segments on the contrast ventriculogram, or both. Heart rate, peak left ventricular systolic pressure, end-systolic pressure and end-diastolic pressure remained constant during atrial, AV pacing and repeat atrial pacing in all patients. In group 1 patients, the decrease in peak negative dP/dt (1,507 +/- 200 versus 1,424 +/- 187 mm Hg/s) and the increase in the time constant of left ventricular relaxation (48 +/- 11 versus 51 +/- 11 ms) during AV pacing was not significantly different when compared with values during atrial pacing.(ABSTRACT TRUNCATED AT 250 WORDS)