Biomedical subjects
Publications and source records attributed to E N Shen.
Radiofrequency catheter ablation is a well-established technique in the therapy of many forms of supraventricular tachyarrhythmias. Its usage in ventricular arrhythmias is little known. This is a report of its first usage in Hawaii in the treatment of 2 specific forms of ventricular tachycardia in 5 patients without structural heart disease. A cure was achieved in 4 of the 5 patients.
This study is a retrospective analysis of 39 consecutive patients who had a prothrombin time of over 25 seconds with respect to the bleeding complications. This study finds that the overall risk of bleeding is low, 2/39 (5.1%), that there is no statistical difference in the values of the patients who bled when compared to those who did not, and that patients who bled tended to have a clearly identifiable precipitating event.
Intraoperative echocardiography in patients undergoing cardiac surgery was first described in 1972. Interest in intraoperative echocardiography has grown in recent years due to the extensive information provided by 2-dimensional (2-D) and color-flow Doppler imaging via the transesophageal approach. The value of this technique also has been verified in large clinical studies involving patients undergoing cardiac surgery. Intraoperative transesophageal echocardiography (TEE) is very useful in preoperative formulation of surgical plans and in immediate post-operative assessment of surgical results in patients undergoing valve surgery.
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Since Andreas Gruentzig first introduced percutaneous transluminal coronary angioplasty (PTCA) in 1977, the ability to revascularize occluded coronary vessels with a catheter has enjoyed an explosive and unimaginable growth. As the equipment and operator experience improved, the possibilities appeared boundless. However, balloon angioplasty is hampered by a significant restenosis rate in the dilated vessel (approximately 30%), which is higher in selected locations (up to 60% in the proximal left anterior descending artery), even in the best of hands. This fundamental limitation may in part be due to the actual nature of the technique itself--stretching the vessel and fissuring the plaque causing remodeling without removal. The uneven, exposed vessel surface post-plaque rupture may contribute to activation of the hemostatic system, with acute thrombosis and release of various platelet and endothelial-derived growth factors, leading to long-term tissue proliferation and restenosis. Atherectomy, the mechanical removal of plaque from the vessel wall, appears to be an answer. This process actually debulks the culprit tissue and leaves behind a smoother, presumably less thrombogenic surface. We wish to report our first experience with a specific form of this technique in 4 consecutive patients, with a brief discussion of its promises and limitations.
Other than atrial fibrillation-flutter, the majority of supraventricular tachyarrhythmias involve either a macro-re-entry circuit utilizing an atrioventricular (AV) accessory pathway or a micro-re-entry circuit inside or around the AV node. The traditional form of therapy has been medical, with suppression by antiarrhythmic agents, most of which carry a heavy side-effect profile. The established alternative for medical therapy has been surgery, with open-chest excisional ablation of the accessory pathway or cryo-modification of the AV node. Even though, as opposed to medical therapy, surgery promises cure, it requires thoracotomy and cardiopulmonary bypass with significant associated morbidity and even mortality, as well as high cost. Ten years ago, the technique of "fulguration" was first introduced, which involved the delivery of an electrical charge through specialized catheters. Our first experience with this technique was reported in this Journal. Unfortunately, despite being a much better tolerated curative procedure involving a very brief hospitalization, the use of high-energy direct current (DC) shocks is associated with a low but significant incidence of serious complications including cardiac perforation, hypotension, coronary artery spasm, and late occurrence of ventricular fibrillation. Concerns about these potential complications have markedly limited the application of the catheter technique. In the past 2 years, adoption of radio-frequency (RF) current as the energy source has allowed the ablation to be performed in a very efficacious and much safer fashion. We would like to report the first experience with this technique in Hawaii.
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A 24-year-old man presented with symptomatic, recurrent, sustained ventricular tachycardia (VT). He was found to have a basal inferior left ventricular diverticulum. His sustained VT was reproduced by programmed electrical stimulation and was unresponsive to procainamide, tocainide, propafenone, and flecainide. Endocardial mapping followed by resection and cryoablative surgery was performed. The patient had only one recurrence after 18 months, with subsequent control with procainamide for over 14 months.
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Wolff-Parkinson-White (WPW) syndrome is a condition characterized by the presence of an atrioventricular (AV) accessory pathway or bypass tract, which is an extraneous piece of muscular tissue connecting atrium to ventricle. This pathway leads to characteristic findings on the electrocardiogram (EKG). Patients with this syndrome are often asymptomatic, but many frequently have various forms of tachyarrhythmias, some of which may be life-threatening. The conventional therapy is medical, by suppression with antiarrhythmic agents. The established alternative to medical therapy has been surgery, with open-chest excisional ablation of the accessory pathway. In experienced centers, this has a high success rate and holds the promise of cure. Unfortunately, it requires thoracotomy, with its not insignificant associated surgical morbidity.
Sudden cardiac death is the major cause of death in the United States today, claiming over 400,000 victims each year, or one per minute. In the majority of cases, the underlying mechanism is malignant ventricular tachyarrhythmia, with the common substrate being abnormal myocardium from ischemic heart disease or congestive cardiomyopathy.
Six patients with coexistent Mahaim and Kent accessory connections are described. Two had left nodoventricular Mahaim connections, the first reported cases demonstrating these findings. In neither were the left-sided Mahaim connections components of a tachycardia and their presence was incidental. In two of four with nodoventricular connections, associated atrioventricular (AV) node conduction and coexistent posteroseptal accessory pathways were found. One of these had the unusual finding of a right-sided Mahaim connection arising from a "fast" AV node pathway. In only one patient did the tachycardia incorporate the Mahaim connection. In this patient, anterograde conduction during tachycardia occurred over a right nodoventricular connection whereas retrograde conduction occurred through a concealed right free wall Kent connection. Two patients had fasciculoventricular connections that were associated with either septal (one patient) or left free wall (one patient) Kent connections. The latter also had evidence of enhanced AV node conduction. This report is unique in that it describes in detail two patients with left nodoventricular connections (Mahaim) inserting in or near the left posterior fascicle. Combined Kent and Mahaim connections, present in the six patients, appear to occur in approximately 5% of patients with the Wolff-Parkinson-White syndrome. Precise identification of bypass connections critical for reentrant circuits is essential for intelligent application of treatment options.
To assess the antiarrhythmic efficacy of intravenous propafenone, 20 patients with inducible sustained supraventricular tachycardia received propafenone, 2 mg/kg body weight, or placebo in a double-blind, randomized, crossover study. Three patients had intra-atrial reentrant tachycardia, 3 had atrioventricular nodal reentrant tachycardia, and 14 had atrioventricular reciprocating tachycardia associated with the Wolff-Parkinson-White syndrome. Termination of supraventricular tachycardia occurred in 15 of the 20 patients receiving propafenone but 0 of the 11 patients receiving placebo (p less than 0.01). Propafenone prolonged refractoriness and slowed conduction of the atrium, the atrioventricular node, and accessory atrioventricular bypass tracts, and these effects provided antiarrhythmic action to halt tachycardia. No adverse effects were observed in any patient. We conclude that intravenous propafenone is safe and effective in the acute treatment of various forms of reentrant supraventricular tachycardia.
Two hundred twenty-four patients underwent ventricular programmed stimulation (VPS) without prior documentation of the clinical occurrence of sustained ventricular tachycardia (VT) or ventricular fibrillation-flutter (VF). Indications for VPS were: palpitations or nonsustained VT during ambulatory monitoring (85 patients), syncope or presyncope (137 patients), and a family history of sudden death (two patients). Sustained VF requiring transthoracic defibrillation was initiated by VPS in 18 patients (8.0%). Four patients were treated for inducible VF with antiarrhythmic agents directed by electropharmacologic testing; five patients were treated empirically; nine patients received no therapy. No patient has had a cardiac arrest or sudden death during a follow-up period 25.2 +/- 13.8 months (mean +/- standard deviation). VF was initiated by two ventricular extrastimuli in three patients and by three extrastimuli in 15 patients. The incidence of VF was similar in patients with and without previous symptoms (8.8% vs 6.9%) or heart disease (7.1% vs 9.6%). It was significantly higher when VPS at three ventricular sites with a current of 5 mA (pulse width 2 msec) was compared to programmed stimulation at two ventricular sites with a current twice diastolic threshold (pulse width 2 msec) (15.2% vs 3.0%, p less than 0.05). VF initiated by VPS in patients without prior VT or VF appears to be a nonspecific finding. Antiarrhythmic therapy for VF may not be necessary in these patients.
Electrophysiologic studies were performed in 15 patients with syncope and/or cardiac arrest who had the long QT syndrome and 11 control subjects who had normal QT intervals. The syndrome was familial in five patients and idiopathic in 10. All patients had a prolonged QT (546 +/- 68 msec, mean +/- SD) and corrected QT (550 +/- 51 msec). Incremental atrial pacing at cycle lengths of 600 to 400 msec resulted in shortening of the QT interval, but there was no significant difference in the magnitude or percent of shortening of the QT interval between patients with the long QT syndrome and control subjects. Intravenous propranolol did not influence the QT interval measured at fixed atrial-paced cycle lengths in patients with either the familial or idiopathic form of the syndrome. Programmed right and left ventricular stimulation with up to three extrastimuli before and during isoproterenol infusion did not induce sustained ventricular tachycardia or ventricular fibrillation in any of the patients. However, rapid polymorphic nonsustained ventricular tachycardia was induced in six of the 15 patients (40%). Neither the inducibility of nonsustained ventricular tachycardia nor the results of electropharmacologic testing with beta-blockers proved to be of any prognostic value during the mean follow-up period of 28 +/- 17 months. Electrophysiologic studies are of limited value in the diagnosis and treatment of patients with the long QT syndrome.
We questioned 113 patients with subsequently diagnosed sustained ventricular tachycardia (VT) regarding the symptoms that prompted their seeking hospital treatment, eliciting the following: 15% of patients had lost consciousness, 15% had near syncope, 35% had mild lightheadedness and 35% had no cerebral symptoms. Patients with preexisting congestive heart failure or a VT rate of 200 beats per minute or greater more often lost consciousness. Other symptoms included palpitations in 57% of patients, chest pain in 27%, dyspnea in 25%, weakness in 6%, nausea or diaphoresis in 3% each and flushing in 2%. In approximately 50% of patients who had mild lightheadedness or no cerebral symptoms, their condition was incorrectly diagnosed as supraventricular tachycardia based on the absence of severe symptoms during the tachycardia. In some patients, VT may be associated with mild or atypical symptoms. The differentiation of supraventricular from ventricular tachycardia should be based on electrocardiographic criteria and should not be influenced by the nature or severity of a patient's symptoms. The severity of cerebral symptoms is at least partially related to the VT rate and a patient's underlying heart disease.
Thirty-two patients with bundle branch block and unexplained syncope underwent electrophysiologic testing, including programmed ventricular stimulation with up to triple extrastimuli. The infranodal conduction time (HV) was 70 ms or greater in 12 patients. Pathologic infranodal block during atrial pacing occurred in 2 patients. Unimorphic ventricular tachycardia (VT) was induced in 9 patients (28%) and polymorphic VT in 5 (16%). A permanent pacemaker was implanted in patients with infranodal block during atrial pacing and, generally, in patients with an HV of 70 ms or more. Patients with inducible unimorphic or sustained polymorphic VT were treated with an antiarrhythmic drug. The mean follow-up period was 19 +/- 14 months (+/- standard deviation). Three patients died suddenly: a noncompliant patient with inducible sustained VT; a patient with a normal electrophysiologic study treated empirically with quinidine for premature ventricular complexes; and a patient with an HV of 70 ms and no inducible VT treated with a permanent pacemaker. The actuarial incidence of sudden death was 10% at 45 months of follow-up. Only 2 patients had recurrent syncope; both had a normal electrophysiologic study. Approximately 50% of patients with bundle branch block and unexplained syncope who undergo electrophysiologic testing are found to have a clinically significant abnormality (HV of 70 ms or more, infranodal block during atrial pacing and inducible unimorphic VT), and some patients have more than 1 abnormality. Long-term management guided by the results of electrophysiologic testing generally is successful in preventing recurrent syncope.(ABSTRACT TRUNCATED AT 250 WORDS)
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