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Biomedical subjects

A B Curtis

Publications and source records attributed to A B Curtis.

At least 37 records · Page 2Linked to original sources
PubMed1997

QT dispersion is a marker for life-threatening ventricular arrhythmias after atrioventricular nodal ablation using radiofrequency energy.

QT dispersion has been cited as a measure of nonuniform myocardial repolarization and a predictor of sudden cardiac death. We describe 38 patients who underwent atrioventricular nodal ablation, 3 of whom had an increase in measured QT dispersion and experienced potentially fatal, pulseless, polymorphic ventricular tachycardia after the procedure.

Cardiac Pacing, Artificial↗
PubMed1997

Influence of patient characteristics in the selection of patients for defibrillator implantation (the AVID Registry). Antiarrhythmics Versus Implantable Defibrillators.

The Antiarrhythmics Versus Implantable Defibrillators (AVID) trial is a prospective, randomized study of treatment for life-threatening ventricular arrhythmias. Patients who are eligible for the main trial but who are not enrolled for any reason are followed in a registry. The objective of the present study was to determine whether there are identifiable patient characteristics among these registry patients that may influence whether a patient is treated with an implantable defibrillator. The 914 patients in the registry were divided into 2 groups according to whether the primary treatment was an implantable defibrillator. The mean age of defibrillator patients was 60 years, compared with 65 years in the nondefibrillator group (p <0.001). Only 11.2% of defibrillator recipients were minorities, whereas the percentage of minorities in the nondefibrillator group was 18.7% (p <0.003). A history of recurrent ventricular fibrillation was more likely in the group treated with defibrillators (8.9% vs 4.4%, p <0.01), whereas a history of atrial fibrillation or diabetes mellitus were both significantly more likely in the nondefibrillator group. Among defibrillator patients, a higher proportion had ventricular fibrillation as the index arrhythmia; patients with ventricular tachycardia were significantly more likely to be treated without devices. In this prospective but nonrandomized cohort of patients treated for life-threatening ventricular arrhythmias, older age, minority status, and comorbidity reduced the chances that a patient would be treated with a defibrillator.

Aged↗
PubMed1997

Termination and suppression of idiopathic left ventricular tachycardia by diltiazem.

Idiopathic left ventricular tachycardia is known to be responsive to verapamil in many cases. However, the role of other calcium-channel blockers, such as diltiazem, in treating this specific type of ventricular tachycardia is unknown. We report a case of idiopathic left ventricular tachycardia in a patient with a structurally normal heart, which was terminated and suppressed in the electrophysiology laboratory by a single dose of diltiazem intravenously, and was subsequently suppressed long-term with sustained-release diltiazem. Our finding suggests that idiopathic left ventricular tachycardia may be managed effectively with diltiazem in both the acute and chronic settings.

Adult↗
PubMed1997

Baseline characteristics of patients in the coronary artery bypass graft (CABG) Patch Trial.

BACKGROUND: Patients with left ventricular dysfunction who undergo coronary artery bypass graft (CABG) surgery frequently have late sudden cardiac death. The CABG Patch Trial is a prospective, randomized, multicenter clinical trial that randomized patients at high risk at the completion of CABG surgery to implantation of an epicardial implantable cardioverter defibrillator (ICD) or to no antiarrhythmic treatment. The trial was designed to determine whether prophylactic implantation of an ICD at the time of CABG surgery would result in a lower total mortality in long-term follow-up. METHODS: Patients undergoing CABG surgery were eligible for the trial if they were younger than 80 years, had a left ventricular ejection fraction less than 0.36, and had an abnormal signal averaged electrocardiogram. Patients with a history of sustained ventricular tachycardia or ventricular fibrillation were excluded from the trial. All patients were scheduled to undergo follow-up at 3-month intervals until 42 months after surgery. RESULTS: Randomization of patients in the trial ended in February 1996. During the recruitment period 71,855 patients were screened, 1,422 were eligible, 1,055 were enrolled (signed consent forms), and 900 patients (76% of eligible patients) were randomized. The mean age of the 446 patients in the ICD group was 64 years versus 63 years for the 454 patients in the control group. A total of 87% of the participants in the ICD group were men versus 82% in the control group (p = NS). Most of the patients had a history of hypertension (55%), smoking (78%), and hypercholesterolemia (54%). Half of the patients had clinical heart failure, and the mean ejection fraction for both patient groups was 0.27 +/- 0.06. No difference was seen in the history of myocardial infarction (83%), congestive heart failure (50%), or atrial (11%) or ventricular (17%) arrhythmias between the two groups. Major clinical characteristics (age, sex, number of previous infarctions, incidence of heart failure, and mean left ventricular ejection fraction) were almost identical to those found in another ICD primary prevention trial, the Multicenter Automatic Defibrillator Implantation Trial (MADIT). CONCLUSIONS: A high risk sample of patients was enrolled in The CABG Patch Trial, as shown by examination of their baseline characteristics.

Adult↗
PubMed1997

Induction of atrioventricular node reentrant tachycardia with adenosine: differential effect of adenosine on fast and slow atrioventricular node pathways.

OBJECTIVES: This study sought to evaluate the sensitivity of fast and slow atrioventricular (AV) node pathways to incremental doses of adenosine in patients with typical AV node reentrant tachycardia. BACKGROUND: Although adenosine is known to depress conduction through the AV node, the relative sensitivity to adenosine of the anterograde fast and slow pathways in patients with dual AV node pathways and typical AV node reentrant tachycardia has not previously been studied. METHODS: Sixteen patients with dual AV node physiology and typical AV node reentrant tachycardia and 10 control patients were given incremental doses of adenosine during atrial pacing. RESULTS: In 14 of 16 patients with dual-AV node physiology, administration of small doses of adenosine during atrial pacing led consistently to transient block of impulse conduction in the fast pathway before block in the slow pathway, resulting in abrupt prolongation of the AH interval with continued 1:1 AV conduction. The mean (+/- SD) doses of adenosine required to cause conduction block in the fast and slow pathways were 2.7 +/- 3.0 and 7.2 +/- 4.7 mg, respectively (p = 0.004). In 9 of 16 patients, administration of low dose adenosine led to initiation of AV node reentrant tachycardia. The control patients showed no abrupt increases in AH interval with administration of adenosine during atrial pacing. CONCLUSIONS: In most patients with dual AV node pathways and typical AV node reentrant tachycardia, the fast pathway is more sensitive than the slow pathway to the effects of adenosine.

Adenosine↗
PubMed1997

Social support, stress, and blood pressure in black adults.

Psychosocial factors arising from socioeconomic disadvantage and discrimination may contribute to the excess risk of elevated blood pressure in African-Americans. The purpose of this study was to assess the association of social support and stress with blood pressure in a community-based sample of 25-to 50-year-old black adults in Pitt County, NC. A stratified random sample of dwellings was selected in 1988, and 1,784 black adults (80% of those eligible) were interviewed. Analyses were sex specific and adjusted for age, obesity, and waist/hip ratio. In separate analyses of emotional support, instrumental support, and stress with blood pressure, all associations were in the predicted direction (inverse for support, direct for stress) but were stronger for systolic than for diastolic blood pressure. Differences in systolic blood pressure associated with low support or high stress ranged from 5.2 to 3.6 mmHg in women and 3.5 to 2.5 mmHg in men. In simultaneous regression analyses of support and stress, each of the separate effects was reduced for women, but a sizable aggregate effect of low support and high stress remained [+7.2 mmHg (95% confidence limits = +1.3, +13.1) for systolic blood pressure and +4.0 mmHg (95% confidence limits = +0.1, +7.9) for diastolic blood pressure.

Adult↗
PubMed1997

Modification of patient driving behavior after implantation of a cardioverter defibrillator.

Driving habits among recipients of ICDs have not been well characterized previously, yet such information may have implications for development of national policy. This study was undertaken to characterize driving behavior after defibrillator implantation in our patient population. From 1988-1993, 82 ICDs were implanted at the University of Florida. All patients received defibrillator teaching preoperatively and postoperatively with particular emphasis placed on driving restrictions. A standardized questionnaire was developed to ascertain driving behavior, compliance with restrictions, and occurrence of motor vehicle accidents following implantation. The patients were divided into two groups according to whether or not they had received a shock from their device since implantation. Group I patients did, and Group II patients did not. Fifty-two out of 82 (63%, Group I) patients had at least one shock. The remaining 30 patients had received no shocks. Mean age and gender were no different between the two groups. Mean time since implantation was 6 +/- 1.3 years in Group I, compared to 4 +/- 1.5 years in Group II (P = 0.001). Forty-seven out of 52 (90%) and 26 out of 30 (87%) in Groups I and II, respectively, resumed driving after defibrillator implantation. There was no difference in the amount of time that passed prior to resumption of driving. Group I patients drove more, 20.5 +/- 27 miles/day compared to patients in Group II, 8.3 +/- 9.7 miles/day (P = 0.02). No patient experienced device discharge during driving; likewise, no patient was involved in a motor vehicle accident secondary to their device firing. Sixty-seven out of 82 (82%) patients complied with the instructions they thought they heard; seven patients in Group I and eight patients in Group II deliberately did not follow our advice. The majority of patients do comply with physician instructions, although the instructions they remember are not always the instructions given. If a national policy is created to prohibit driving after ICD implantation, effective enforcement may be difficult.

Accidents, Traffic↗
PubMed1997

Permanent atrial pacing in cardiac transplant patients.

Thirteen out of 223 consecutive cardiac transplant patients required permanent pacemaker implantation; 11 for sinus node dysfunction and 2 for complete AV block. Patients with sinus node dysfunction were considered for AAIR mode pacemakers if they had intact AV conduction defined as a Wenckebach point of > 120 beats/min. Ten of 11 patients with sinus node dysfunction had a single atrial lead placed. Atrial lead placement was most easily accomplished with a straight, active fixation lead and the use of manually curved stylets to find an optimal position in the donor atrium, although active fixation leads with a preformed atrial J were used as well. Two leads dislodged requiring revision. In contrast, only 1 of 250 atrial leads implanted in nontransplanted hearts dislodged (P < 0.0001). Transvenous endomyocardial biopsies have not caused atrial lead dislodgment. Most transplant recipients requiring permanent pacing have intact AV nodal function and require only atrial pacing. Atrial lead dislodgment requiring lead revision occurs more frequently in heart transplant recipients than in native hearts. Use of a straight active fixation lead with a manually formed curve in the stylet is useful in order to find the optimal position for pacing.

Adult↗
PubMed1997

Job strain and blood pressure in African Americans: the Pitt County Study.

OBJECTIVES: This report examined whether job strain (or its components, decision latitude and job demands) was associated with elevated blood pressure levels in a community-based sample of 726 African-American adults. METHODS: Blood-pressure, anthropometric, behavioral, demographic, and psychosocial data were collected for the current cross-sectional analyses during home interviews conducted for the second wave (1993) of the Pitt County Study (North Carolina), a prospective cohort study of hypertension among African Americans. RESULTS: Job strain was not associated with blood pressure among men or women in this study. However, men in the 80th percentile of decision latitude had more than a 50% decrease in the prevalence of hypertension compared with men in the 20th percentile (odds ratio = .46, 95% confidence interval = .22, .96). CONCLUSIONS: These results indicate that decision latitude may be important for hypertension risk among African-American men. More research is needed on African Americans to determine why job strain and its two component variables differ in their associations with blood pressure for men and women.

Adult↗
PubMed1996

Oversensing of atrial flutter in the recipient atrium of a heart transplant patient with a permanent atrial pacemaker.

Sinus node dysfunction requiring permanent pacemaker implantation is a common problem following heart transplantation. There are unique problems to consider in pacing the transplanted heart. This report describes a case of far-field sensing of atrial flutter in the recipient atrial remnant, with resultant inhibition of the atrial pacemaker in the donor atrium, and symptomatic bradycardia. Although postulated to be a potential problem, oversensing of the recipient atrium has not been reported prior to this case. Awareness of this problem will provide for more effective pacemaker troubleshooting.

Atrial Flutter↗
PubMed1996

Transesophageal echocardiographic guidance of transseptal left heart catheterization during radiofrequency ablation of left-sided accessory pathways in humans.

UNLABELLED: Radiofrequency ablation (RFA) of left-sided accessory pathways can be achieved using catheters introduced by a retrograde or transseptal approach. Transesophageal echocardiography (TEE) has previously been demonstrated to be safe and efficacious in guiding transseptal puncture in patients during mitral valvuloplasty (MV). This study was undertaken to assess the feasibility, safety, and clinical utility of TEE during transseptal puncture and RFA of left-sided accessory pathways. METHODS: TEE was performed during transseptal puncture in 30 patients (41 +/- 12 years, 19 females), 15 patients during attempted RFA of a left-sided accessory pathway and 15 patients during attempted balloon MV. RESULTS: There was no difference in age, sex distribution, or procedural complications when MV patients were compared to RFA patients. At baseline, left atrial dimension was increased and congestive heart failure was more common when MV patients were compared to RFA patients (P < 0.05) Adequate baseline two-dimensional and Doppler TEE images were obtained in all patients. One patient sustained mild esophageal bleeding during the TEE. Positioning of the transseptal catheter in the fossa ovalis was facilitated and confirmed by TEE in 29 of 30 cases. One case of cardiac perforation occurred and was associated with inadequate TEE localization of the fossa ovalis. Thrombus was detected on the transseptal catheter by TEE in two cases prior to systemic heparinization. In both cases, thrombus was removed without embolic event. CONCLUSIONS: TEE safely guides transseptal puncture in patients undergoing RFA of left-sided accessory pathways. TEE markers of the fossa ovalis facilitate puncture and may reduce the risk of cardiac perforation particularly in patients with a normal size left atrium. TEE may be especially valuable for identifying thrombus during transseptal puncture.

Adolescent↗
PubMed1995

Endogenous adenosine is an antiarrhythmic agent.

BACKGROUND: Adenosine administered intravenously terminates supraventricular tachycardias (SVT) involving the AV node as part of the reentrant circuit. Dipyridamole increases interstitial myocardial levels of this nucleoside. This study was designed to determine whether intravenous dipyridamole increases coronary sinus plasma adenosine concentrations ([Ado]cs) in humans to levels sufficient to alter electrophysiological parameters and terminate SVT. METHODS AND RESULTS: A custom-designed catheter and syringe for sampling blood for measurement of [Ado]cs was placed in the coronary sinuses of 7 patients. [Ado]cs and refractory periods and conduction characteristics of the atrium and AV node were determined after autonomic blockade and dipyridamole infusion (5 micrograms.kg-1.min-1 after a loading dose of 0.56 mg/kg). The atrial effective and functional refractory periods remained unchanged after dipyridamole infusion. In contrast, the AV nodal functional refractory period increased from 350 +/- 32 to 381 +/- 41 milliseconds (P = .03); the Wenckebach cycle length also increased from 309 +/- 47 to 350 +/- 57 milliseconds (P < .0001). Coincident with these changes, [ADO]cs increased from 0.18 +/- 0.11 to 0.31 +/- 0.12 mumol/L (P = .02). In another 10 patients with AV or AV nodal reentrant tachycardia, SVT was induced, and coronary sinus blood samples were drawn. Dipyridamole was infused, and coronary sinus blood samples were obtained after 15 minutes or coincident with termination of SVT. Mean [ADO]cs increased from 0.17 +/- 0.06 mumol/L during SVT to 0.38 +/- 0.21 mumol/L after dipyridamole (P = .02). Mean tachycardia cycle length increased from 334 +/- 132 to 375 +/- 139 milliseconds (P = .02); this effect was confined to the AV node, as demonstrated by an increase in AH interval from 171 +/- 144 to 214 +/- 140 milliseconds (P = .003). SVT terminated with the infusion of dipyridamole in 4 of the 10 patients. CONCLUSIONS: Administration of dipyridamole is associated with elevation of [ADO]cs, with coincident prolongation of the mean Wenckebach cycle length and AV nodal functional refractory period. During SVT, dipyridamole leads to prolongation of the AH interval and tachycardia cycle length and to an increase in [ADO]cs, with termination of SVT in four patients. These results support the hypothesis that adenosine may function as an endogenous antiarrhythmic metabolite.

Adenosine↗
PubMed1995

Emergency intracardiac defibrillation for refractory ventricular fibrillation.

Hemodynamically unstable ventricular arrhythmias induced during electrophysiologic testing almost always respond to prompt application of direct current transthoracic shocks. In rare cases, however, ventricular fibrillation may be refractory to conventional treatment. Recently, a technique of intracardiac defibrillation has been successfully used to resuscitate patients with ventricular fibrillation refractory to transthoracic defibrillation. We describe two patients with a history of myocardial infarction and left ventricular dysfunction who were admitted with symptomatic episodes of ventricular tachycardia. Both had inducible sustained monomorphic ventricular tachycardia. During a repeat electrophysiologic study in Patient No. 1 on procainamide and at the initial study in Patient No. 2, right ventricular burst pacing to terminate ventricular tachycardia resulted in ventricular fibrillation refractory to resuscitation efforts, including transthoracic defibrillation with 360 J. Emergency intracardiac defibrillation with 200 and 360 J, respectively, successfully converted both patients to sinus rhythm. Both patients were subsequently discharged from the hospital on amiodarone. These cases illustrate the life-saving capabilities of intracardiac defibrillation.

Aged↗
PubMed1995

Advanced cardiac life support: update on recent guidelines and a look at the future.

The objectives of this article are to provide an update of the American Heart Association (AHA) 1992 National Conference guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiac care and to review the investigation and development of new methods of CPR which may be considered in future recommendations. Despite an organized approach to sudden cardiac arrest, survival in patients receiving CPR is in the range of 5-15%. The new AHA guidelines recommend standard manual CPR performed at a rate of 80-100 compressions/min and organized algorithms of advanced cardiac life support. These guidelines stress widespread community training and rapid response in the following sequence: (1) recognition of early warning signs, (2) activation of the emergency medical system (EMS), (3) basic CPR, (4) early defibrillation, (5) intubation, and (6) intravenous medication. Several new recommendations pertain specifically to in-hospital care and are, therefore, particularly relevant to physician management of cardiac arrest. The best predictor of survival in patients requiring circulatory support after cardiac arrest is attainable coronary and cerebral perfusion. Unfortunately, the minimal levels of end-organ perfusion required to sustain life are often difficult or impossible to achieve with standard manual cardiopulmonary resuscitation and several new techniques have therefore been introduced. The most promising of these techniques are (1) interposed abdominal compression, (2) pneumatic vest, and (3) active compression-decompression resuscitation. Each of these techniques offers unique advantages when compared with standard manual cardiopulmonary resuscitation. The 1992 National Conference recommendations provide a rational framework for the resuscitation of cardiac arrest victims. New methods of cardiopulmonary resuscitation are now available and investigation into these methods continues.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1995

Motor vehicle accidents in patients with an implantable cardioverter-defibrillator.

OBJECTIVES: This study was designed to examine driving safety in patients at risk for sudden death after implantation of a cardioverter-defibrillator. BACKGROUND: Cardioverter-defibrillators are frequently implanted in patients at high risk for sudden death. Despite concern about the safety of driving in these patients, little is known about their actual motor vehicle accident rates. METHODS: Surveys were sent to all 742 physicians in the United States involved in cardioverter-defibrillator implantation and follow-up. Physicians were questioned about numbers of patients followed up, numbers of fatal and nonfatal accidents, physician recommendations to patients about driving and knowledge of state driving laws. RESULTS: Surveys were returned by 452 physicians (61%). A total of 30 motor vehicle accidents related to shocks from implantable defibrillators were reported by 25 physicians over a 12-year period from 1980 to 1992. Of these, nine were fatal accidents involving eight patients with a defibrillator and one passenger in a car driven by a patient. No bystanders were fatally injured. There were 21 nonfatal accidents involving 15 patients, 3 passengers and 3 bystanders. The estimated fatality rate for patients with a defibrillator, 7.5/100,000 patient-years, is significantly lower than that for the general population (18.4/100,000 patient-years, p < 0.05). The estimated injury rate, 17.6/100,000 patient-years, is also significantly lower than that for the general public (2,224/100,000 patient-years, p < 0.05). Only 10.5% (30 of 286) of all defibrillator discharges during driving resulted in accidents. Regarding physician recommendations, most physicians (58.1%) ask their patients to wait a mean (+/- SD) of 7.3 +/- 3.4 months after implantation or a shock before driving again. CONCLUSIONS: The motor vehicle accident rate caused by discharge from an implantable cardioverter-defibrillator is low. Although restricting driving for a short period of time after implantation may be appropriate, excessive restrictions or a total ban on driving appears to be unwarranted.

Accidents, Traffic↗
PubMed1994

Termination of pacemaker-mediated tachycardia by adenosine.

A 30-year-old woman was referred for follow-up right- and left-heart catheterization 4 years after cardiac transplantation. She had an implanted epicardial pacemaker for bradycardia; this was programmed to the DDD mode. At the time of her catheterization, as a pigtail catheter was pulled back across the aortic valve, runs of premature ventricular complexes occurred and tachycardia with ventricular pacing spikes and ventricular capture was initiated at a rate of 126 beats/min. Adenosine 6 mg was given intravenously through a femoral venous sheath and within 20 s the tachycardia broke. The tachycardia was consistent with pacemaker-mediated tachycardia (PMT), a circus movement tachycardia occurring when ventricular pacing causes retrograde atrial depolarization followed by triggering of ventricular pacing. With reprogramming of the pacemaker to an AV delay of 160 ms and a postventricular atrial refractory period of 300 ms, no further episodes of PMT have occurred. This case illustrates that intravenous adenosine can effectively terminate PMT by causing ventriculoatrial block, thus interrupting the reentrant circuit by eliminating retrograde atrial activation.

Adenosine↗