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Biomedical subjects

L W Castle

Publications and source records attributed to L W Castle.

At least 37 records · Page 2Linked to original sources
PubMed1991

Retrospective analysis of patients undergoing one- or two-stage strategies for myocardial revascularization and implantable cardioverter defibrillator implantation.

Internal defibrillation leads were placed at time of coronary revascularization in 79 patients. In 34, an implantable cardioverter defibrillator (ICD) was placed simultaneously (group I). A two-stage strategy (selective implantation of the ICD in patients with postoperative spontaneous or inducible ventricular tachycardia [VT]) was followed in 45 patients (group II). Group I patients had failed more antiarrhythmic drug trials (2.9 +/- 1.6 vs 1.5 +/- 1.6; P = 0.02), including amiodarone (62% vs 20%; P less than 0.001). There were four operative deaths in each group. Postoperatively, VT was present in 27 group II patients (60%), 25 of whom received an ICD (two refused device implantation). Patients with postoperative VT had a lower left ventricular ejection fraction than those without VT (33 +/- 9 vs 47 +/- 16; P = 0.01). Actuarial survival at 1, 2, and 3 years was 88 +/- 6, 88 +/- 7, and 88 +/- 10 in group I; and 83 +/- 6, 76 +/- 7, and 76 +/- 11 in group II (NS). No patient without an ICD (based on the postoperative electrophysiological study [EPS]) died suddenly. Five patients (6%) had ICD system infection. Sudden death was largely prevented by either strategy, but relatively high rates of operative mortality and ICD system infection were observed. Prospective studies should identify patients more likely to benefit from one or another strategy.

Aged↗
PubMed1990

Chronic transvenous pacemaker lead removal using a unique, sequential transvenous system.

Transvenous removal of 43 consecutive chronic pacemaker leads was successful in 28 patients. For leads not removed by traction at the pacemaker connection terminal, a unique locking stylet was advanced through the inner coil lumen and engaged at the tip to allow traction without lead elongation. Leads not extracted with the locking stylet alone had traction maintained on the stylet as sheaths were advanced over the lead to dilate and detach any fibrous tissue adherent to the lead. By applying traction at the pacemaker connection terminal, 2 leads were removed. The locking stylet alone extracted 9 leads. Both the locking stylet and sheaths were necessary to explant 32 leads. There were 15 right atrial and 22 right ventricular leads completely removed. Additionally, 6 right ventricular leads were subtotally removed leaving only the tip in the right ventricular apex. Avulsed myocardium was removed with the lead in 1 patient without sequelae. A subacute hemothorax developed in 1 patient 18 days after discharge requiring drainage, and subclavian vein thrombosis developed in another, which was successfully treated with anticoagulation. Hypotension occurred in 1 patient during final positioning of new leads, which responded to conservative treatment. Chronic pacemaker leads can be reliably removed without thoracotomy. Both a unique locking stylet to allow traction without lead elongation and a sheath to dilate and detach adherent fibrous tissue are needed for consistent success. Recognized complications included myocardial avulsion without sequelae, subacute hemothorax, subclavian vein thrombosis and transient hypotension.

Adult↗
PubMed1990

Potassium loading as adjunct treatment of repetitive ventricular arrhythmias.

To evaluate potassium supplementation as adjunct therapy for ventricular arrhythmias, consecutive normokalemic patients undergoing in-hospital antiarrhythmic therapy for ventricular tachycardia were randomly assigned to one of four groups: intravenous potassium chloride (Group I, 44 patients) v intravenous saline (Group II, 48 patients); and oral potassium chloride capsules (Group III 50 patients) v no additional treatment (Group IV, 47 patients). All groups underwent serial serum potassium determinations and 24-hour electrocardiographic monitoring. Analysis revealed no significant differences in ventricular ectopic activity among groups, and there was no significant association between serum potassium level and incidence of ventricular arrhythmias. We conclude that normokalemic patients undergoing antiarrhythmic therapy for ventricular tachycardia benefit little from concomitant short-term potassium supplementation.

Female↗
PubMed1990

Pacemaker and defibrillator combination therapy for recurrent ventricular tachycardia.

The judicious use of antitachycardia pacemakers can enhance the benefits of automatic implantable cardioverter defibrillators in certain patients. Both devices were implanted in 10 highly selected patients with drug-refractory pace-terminable sustained ventricular tachycardia. During the observation period of 8 +/- 4.8 months, the automatic pacemakers detected 1,542 episodes of ventricular tachycardia and appropriately managed 1,373. The automatic implantable defibrillator was activated at least once in every patient; on two documented occasions, the defibrillator discharged because the automatic pacemaker accelerated the tachycardia. Concomitant antiarrhythmic drugs could be reduced but not withdrawn. With meticulous device programming and testing, the two systems in combination can work synergistically to manage malignant ventricular arrhythmias in carefully selected patients.

Aged↗
PubMed1989

The use of beep-o-grams in the assessment of automatic implantable cardioverter defibrillator sensing function.

Noninvasive assessment of sensing performance in the automatic implantable cardioverter defibrillator is limited by the absence of telemetry or memory functions. The adaptation of the electrophysiological test mode into a "beep-o-gram" recording, with simultaneous audible tones and a surface electrocardiogram, was used in the confirmation of sensing malfunction. Eleven of 13 recordings in patients with documented or clinically suspected inappropriate defibrillator discharges (group 1) demonstrated evidence of definite oversensing. Nonspecific oversensing or undersensing was present in 77% of 27 randomly selected asymptomatic patients without known sensing malfunction (group 2). The sensitivity and specificity for identifying definite oversensing was 85% and 60%, respectively. The beep-o-gram system is a reliable, noninvasive means of confirming sensing malfunction in the automatic implantable cardioverter defibrillator. Its specificity is limited by the detection of subclinical sensing aberrations, to some degree related to the device's automatic gain control sensing algorithm.

Electric Countershock↗
PubMed1988

The usefulness of head-up tilt testing and hemodynamic investigations in the workup of syncope of unknown origin.

To enhance the clinical evaluation of patients suffering from recurrent syncope of unknown origin, the integrity of mechanisms controlling blood pressure was examined in 151 patients utilizing a screening tilt test. Ninety-eight patients had an abnormal blood pressure and/or heart rate response to tilt testing, including provoked syncopal attacks in 63 patients. Whenever indicated, the screening tilt test was followed by blood volume and hemodynamic determinations, as well as autonomic nervous system testing to identify contributing pathophysiological abnormalities (hypovolemia, venous pooling, autonomic dysfunction). Detailed analysis of this battery of tests allowed us to conclude that: (1) The tilt test is commonly a provocative tool in the workup of patients with recurrent syncope due to vasovagal - vasodepressor reactions and other abnormalities of blood pressure regulation; (2) Its usefulness is augmented by associated hemodynamic and blood volume evaluations; (3) The identification of contributory pathophysiological mechanisms of blood pressure control facilitates specific therapeutic interventions.

Autonomic Nervous System Diseases↗
PubMed1986

Design-dependent cross-talk in a second generation DDD pacemaker.

A unique mechanism of "cross-talk" has recently been described in the Gemini 415A DDD pacemaker in which cross-inhibition of the ventricular output stimulus may occur in the early Gemini 415A models which were manufactured with dual anodal rings interconnected by a wire. The Gemini 415A units with dual anodal rings were implanted under investigational protocol in 53 patients from September 1982 to August 1984. To date, cross-talk has been discovered in six patients during clinical follow-up, manifesting as inappropriate ventricular inhibition. Syncope was documented in one patient. Non-Cordis atrial and ventricular leads were present in all six patients and five patients had at least one chronic lead. Cross-talk was neither evident nor provokable in Gemini 415A units which had compatible Cordis lead systems. Reduction of the atrial output and/or the ventricular sensitivity prevented cross-inhibition in three patients. Cross-talk persisted in three patients despite programming to the lowest atrial output and/or ventricular sensitivity parameters. Cross-talk, spontaneous or provoked, has not occurred in 36 patients having currently designed 415A pulse generators manufactured with a single anodal ring in the ventricular connector channel. We conclude that: this unique form of cross-talk is "design-dependent" and occurs only in Gemini 415As with dual interconnected anodal rings and cannot occur in 415As manufactured with a single anodal ring; this form of cross-talk has occurred only in 415As with non-Cordis leads and appears to be a time-dependent development; reduction of the atrial output or use of pacing modes without atrial pacing or ventricular sensing can prevent cross-talk.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradycardia↗
PubMed1986

Noninvasive assessment of ventriculo-atrial conduction and early experience with the tachycardia termination algorithm in pacemaker-mediated tachycardia.

Since the advent of physiologic dual chamber pacing systems, pacemaker-mediated tachycardia (PMT) has occurred and the need for invasive measurement of ventriculo-atrial conduction (VAC) has arisen. The variability in VAC and the potential for PMT often make it necessary to assess for the presence or absence of VAC at different points in time. We noninvasively evaluated 20 pacemaker patients for the presence or absence of VAC. We compared ventriculo-atrial conduction time (VACT) obtained with the atrial sense event maker with that obtained from Holter monitoring and invasive methods. The incidence of spontaneous (S) and induced (I) PMT and the efficacy of the tachycardia termination algorithm (TTA) was assessed. Fourteen of 20 had VAC with invasive or noninvasive methods. Twelve of 19 had PMT (63%); three were sustained (greater than 15 beats). We conclude that VACT assessed with the atrial sense event marker (ASEM) yielded a high correlation when compared to the Holter monitor data obtained utilizing our methodology. PMT is commonly a nonsustained (less than 15 beats) event, and the TTA is effective in sustained PMT. Myopotential sensing, atrial premature contractions and loss of atrial capture are common mechanisms in the initiation of PMT.

Adult↗
PubMed1986

Electrophysiologic studies of patients with hypertrophic cardiomyopathy presenting with syncope of undetermined etiology.

Patients with hypertrophic cardiomyopathy (HC) have a high risk of sudden death. The best clinical predictors of sudden death from HC are young age, strong family history of sudden death, ventricular tachycardia (VT), and progression of symptoms such as syncope. We performed 24-hour Holter monitoring and electrophysiologic studies (EPS) on 26 patients with HC, some with the obstructive form of the disease and some with syncope, in order to predict their vulnerability to syncope and to potentially malignant arrhythmias. Holter monitoring demonstrated supraventricular tachycardia (SVT) in 9/26 patients whereas atrial programmed electrical stimulation induced SVT in 17/26 patients. Of the 17 patients, nine had symptomatic hypotension with SVT while lying supine. Holter monitoring demonstrated nonsustained VT in 7/26 patients whereas ventricular programmed electrical stimulation induced VT or ventricular fibrillation (VF) in 6/26 patients. The patient who had the longest run of nonsustained VT on Holter had VF induced by ventricular programmed electrical stimulation. He was cardioverted to normal sinus rhythm with no untoward effects. We found that atrial programmed electrical stimulation induced SVT with hypotension best predicted a history of syncope in these patients. Although one patient required direct current cardioversion, EPS was conducted safely in all patients. Further long-term studies are needed to demonstrate the value of clinical decisions based upon EPS in patients with HC.

Adolescent↗
PubMed1984

Amaurosis fugax in a patient with a left ventricular endocardial pacemaker.

A transvenous left ventricular endocardial pacemaker catheter is a potential source of systemic arterial embolization. The case of a woman who presented with left-eye amaurosis fugax is reported. The patient had a history of contralateral carotid atherosclerosis; however, the digital subtraction angiography of the carotid arteries was not sufficiently abnormal to account for her present symptoms. The patient had a history of two myocardial infarctions and the tachycardia-bradycardia syndrome for which she was treated with a demand ventricular pacemaker. The chest x-ray and electrocardiogram suggested pacemaker catheter malposition. By M-mode and two-dimensional echocardiography, the catheter was shown to cross the atrial septum and the mitral valve to implant in the left ventricular endocardium. The approach to diagnosis and therapy that led to surgical removal of the pacing catheter is presented. The causes of the electrocardiographic right bundle branch block pattern in cardiac pacing and the usefulness of echocardiography in evaluating pacing catheters are discussed.

Aged↗
PubMed1982

Long-term control of congestive heart failure with captopril.

The long-term effects of captopril therapy were assessed by sequential hemodynamic studies over a 6 month period in 19 patients with resistant congestive heart failure. Initial improvement during the first week of therapy was noted only in 11 and was marked by significant (p less than 0.005) increases in cardiac output and stroke volume, slowing of heart rate, and reduction of total peripheral resistance. Of the remaining eight patients, seven improved subsequently with maintained therapy so that by the end of 3 months of treatment only one patient failed to respond significantly. The hemodynamic index that reflected response most consistently was the shortening in pulmonary mean transit time. Simultaneously with clinical improvement there was a reduction in cardiopulmonary volume that reflected a reduction in pulmonary congestion and probably systemic vasodilation. Associated with these hemodynamic changes there was an increase in plasma renin activity and a significant reduction in plasma aldosterone, but these changes did not differ significantly between patients who responded markedly and those who responded moderately to converting enzyme inhibition. These results suggest that the response of congestive heart failure to captopril can occur gradually. Improvement was related to peripheral hemodynamic changes which led to a reduction in both total peripheral resistance and cardiopulmonary volume. The reduction in the plasma aldosterone/renin activity ratio was an effective marker of compliance.

Adult↗
PubMed1982

Long-term follow-up of young adults following permanent pacemaker placement for complete heart block.

Young adults with nonsurgically induced complete heart block (CHB) do not necessarily have a benign prognosis and pacemaker (PM) implantation may be necessary. No one has reported long-term PM follow-up in young adults with CHB. We studied 13 patients aged 15 to 37 years (mean 24 years) at PM implantation. There were nine female and four male patients. All were functional class II or III (NYHA) before PM implantation. Syncope, dizziness, fatigue, shortness of breath, and dyspnea on exertion were the most common symptoms. Cardiac catheterization findings (11 of 13 patients) were normal in five, and additional cardiac anomalies were present in six. His bundle studies (9 of 13 patients) showed absent AH intervals in all patients, with HV intervals not identified in two, 20 to 30 msec in one, and 30 to 50 msec in six patients. Holter monitor recordings (8 of 13 patients) demonstrated CHB in all eight with intermittent second- to third-degree block in two of three patients. Two patients had occasional premature ventricular contractions. Stress exercise tests (9 of 13 patients) demonstrated increased ventricular rate response (although subnormal in some patients); symptoms developed in seven. One patient had ventricular ectopy. All 13 patients were contacted 3 months to 7 years (mean 4 years) after PM implantation. Two patients had died, but the deaths were not related to PM dysfunction. All patients who are currently alive had marked improvement in functional symptomatology and all are currently functional class I. CHB is not a benign condition in young adults and may require PM implantation, which improves symptoms and allows the patient to lead a normal life.

Adult↗