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Biomedical subjects

J B Conti

Publications and source records attributed to J B Conti.

36 records · Page 2Linked to original sources
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

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↗
PubMed1994

Catheter entrapment in the mitral valve apparatus during radiofrequency ablation.

Catheter ablation of accessory atrioventricular pathways in patients with Wolff-Parkinson-White syndrome has become an increasingly popular therapeutic option. Catheter technology is rapidly evolving, allowing physicians to tailor the choice of catheter to the location of the pathway. We describe catheter entrapment in the mitral valve apparatus while using a valve mapping catheter with a peanut shaped tip to approach a left free-wall pathway retrogradely across the aortic valve.

Adult↗
PubMed1993

Antiarrhythmic therapy in patients with congestive heart failure.

Current information suggests that in patients with congestive heart failure (CHF) who have asymptomatic ventricular arrhythmias, coronary artery disease (dilated ischemic cardiomyopathy), and a positive signal-averaged electrocardiogram, electrophysiologic studies are useful for stratifying risk and guiding therapy. Therapy with amiodarone hydrochloride (Cordarone) appears to improve survival in patients after myocardial infarction. In CHF patients with asymptomatic ventricular arrhythmias and dilated nonischemic cardiomyopathy, electrophysiologic studies are of little value in risk stratification because of their low yield of sustained monomorphic tachycardias. There is little evidence that therapy with conventional antiarrhythmic agents improves survival. Although amiodarone can suppress ventricular ectopic beats, no trial yet conducted has detected an effect on mortality. Randomized, controlled trials with low-dose amiodarone are needed for more definitive information. Most symptomatic patients should undergo electrophysiologic testing and receive guided therapy, either with antiarrhythmic drugs or with an implantable cardioverter-defibrillator.

Amiodarone↗
PubMed1992

Atrial fixation leads--a visual aid confirming actual fixation.

Various active fixation mechanisms are available for atrial lead implantation. Confirmation of actual fixation of the lead tip in the myocardium is sometimes difficult with standard techniques such as fluoroscopy. Our observation of organized clockwise/counterclockwise motions of the fixation stylet in synchrony with atrial systole confirms adequate positioning of the Accufix model #330-801 atrial lead in the right atrial appendage, which is helpful when the screw is difficult to visualize under fluoroscopy. This observation was confirmed in nine patients.

Electrodes, Implanted↗
PubMed1985

Isosorbide dinitrate and nifedipine in variant angina pectoris.

The efficacy of isosorbide dinitrate (ISDN) in variant angina is enhanced by the addition of a calcium antagonist. A prospective double-blind, crossover trial of ISDN, 40 to 120 mg/day, and nifedipine, 40 to 120 mg/day, in 19 patients with variant angina and various degrees of coronary atherosclerosis showed that although both agents were equally effective in controlling angina of vasospastic origin, some patients responded better to one or the other drug. Such response could not be predicted by demographic factors, ECG changes, or degree of coronary atherosclerosis. Since quantitative angiography done in a similar group of patients showed that intracoronary nitroglycerin, 200 micrograms, was a more potent vasodilator than sublingual nifedipine, 10 mg (p less than 0.01), the calcium antagonists may have a different mechanism of preventing variant angina attacks and may act in an additive or synergistic fashion when administered in combination with long-acting nitrates. Such a combination will increase coronary blood flow, reduce ventricular volume and end-diastolic pressure, and reduce systemic arterial resistance. Coronary vasospasm may be directly prevented by a general inhibition of smooth muscle contraction by the calcium antagonist. Clinical studies suggest that combination therapy significantly improves the long-term prognosis of patients with variant angina and reduces the need for bypass surgery. Thus combining ISDN with a calcium antagonist is a rational and effective treatment for variant angina.

Angina Pectoris, Variant↗
PubMed1983

Effect of glyceryl trinitrate on coronary and systemic hemodynamics in man.

The effects of sublingual and intracoronary nitrates on coronary artery diameter were evaluated in five separate experiments in man. The first three are concerned with sublingual nitrates and the last two with intracoronary nitrates. The data obtained indicate that (1) administration of a fixed dose sublingual nitrate results in an increase in percent coronary artery stenosis compared with control measurements; (2) small doses of sublingual nitrates can dilate coronary arteries without a significant reduction in systemic arterial pressure or increase in heart rate; (3) the magnitude of percent coronary artery dilation after a fixed dose of sublingual nitrate is inversely related to the size of the coronary artery, that is, the smaller the coronary artery diameter the greater the relative dilation after administration of sublingual nitrate; (4) fixed dose sublingual nitrate often dilated coronary stenoses, but the more narrow stenoses were less likely to dilate; (5) the optimal dose of intracoronary nitrate required to produce maximal or near maximal coronary dilation without clinically important systemic hemodynamic effects is in the range of 200 micrograms; (6) intracoronary nitrate is a more potent coronary artery dilator than sublingual nifedipine, when administered as a 10 mg dose.

Administration, Oral↗
PubMedDate not supplied

Supportive communication with implantable cardioverter defibrillator patients: seven principles to facilitate psychosocial adjustment.

METHODS: This article incorporates known findings from the psychological literature regarding health behaviors and adjustment to cardiac illness with identified psychosocial needs of implantable cardioverter defibrillator (ICD) patients. An emphasis is placed on healthcare providers' unique ability to facilitate adjustment during routine patient contacts. RESULTS: Seven principles of supportive communication are presented to enhance healthcare providers' awareness of the psychosocial needs of ICD patients. A table of "quotes" representing each principle is provided to show how each form of supportive communication may be delivered to optimize health outcomes for ICD patients. CONCLUSIONS: Brief, routine communication between healthcare providers and ICD patients about psychosocial issues can facilitate patient adjustment. Although not sufficient to meet the needs of all ICD patients, supportive communication bolsters problem-solving and coping strategies of most ICD patients. For patients with more severe psychological adjustment difficulties, supportive communication may lead to better identification of patients who would benefit from referrals to mental health professionals.

Communication↗
PubMedDate not supplied

Biventricular pacing therapy for congestive heart failure: a review of the literature.

Biventricular pacing is a new therapy for patients with congestive heart failure and mechanical dyssynchrony. Its therapeutic intent is to activate both ventricles simultaneously, thus improving the mechanical efficiency of the ventricles. Preliminary evidence indicates improvement in hemodynamics, quality of life, and exercise capacity in patients in sinus rhythm as well as in patients with atrial fibrillation. An improvement in diastolic filling, a decrease in mitral regurgitation, and more efficient systolic ejection are proposed as the mechanisms behind these benefits. In addition, some evidence indicates that the frequency of ventricular arrhythmias is decreased. All clinicians involved in the management of patients with congestive heart failure eagerly await the results of ongoing trials. The results of these trials will define which patients are eligible for this therapy, which patients will derive the most benefit from it, and its effect on morbidity and mortality.

Arrhythmias, Cardiac↗