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Biomedical subjects

S R Spielman

Publications and source records attributed to S R Spielman.

At least 55 records · Page 3Linked to original sources
PubMed1984

Report of the NASPE Mode Code Committee.

The NASPE Mode Code Committee was formed in response to the growing need for efficient means of describing the function of increasingly complex single- and dual-chamber cardiac pacemakers. After considering numeric, alphabetic, and pictorial codes, the Committee recommended the adoption of two codes: a generic code which is similar to the Revised ICHD Code and is suitable for conversational use, and a specific code, based on one developed by Brownlee and others, that permits more detailed specification of both antibradycardia and antitachycardia functions. The specific code described in this report was adopted by the NASPE Executive Advisory Committee as the NASPE Specific Code in March, 1983. The generic code was not adopted but is described herein for future reference in the light of experience to be gained in the use of the recently published Revised ICHD Code.

Pacemaker, Artificial↗
PubMed1984

Selection of patients with recurrence of ventricular tachyarrhythmias for electrical studies.

Clinical cardiac electrophysiologic testing has been employed in the evaluation and treatment of patients with tachyarrhythmias. In patients with recurrent supraventricular tachyarrhythmias, electrophysiologic study is indicated when the arrhythmia is life-threatening or significantly disruptive to lifestyle, when empiric therapy has failed to control the arrhythmia, or when supraventricular tachycardia complicates the Wolff-Parkinson-White syndrome. In patients with ventricular tachyarrhythmias, electrophysiologic study should be undertaken when life-threatening sustained ventricular tachyarrhythmias are documented or when a substantial risk of developing these arrhythmias is noted.

Atrial Fibrillation↗
PubMed1984

Steady-state serum amiodarone concentrations: relationships with antiarrhythmic efficacy and toxicity.

The relationship of apparent steady-state serum concentrations of amiodarone and its metabolite, desethylamiodarone, to therapeutic and toxic effects was assessed in 127 patients who had treatment-resistant ventricular or supraventricular arrhythmias or were intolerant to other agents. After at least 2 months (mean, 9.8) of treatment with daily maintenance doses of 200 to 600 mg, arrhythmias were effectively suppressed in 78% of patients. Arrhythmias recurred in 47% of patients with serum amiodarone concentrations of less than 1.0 mg/L, whereas only 14% of patients with higher concentrations had recurrences (p less than 0.005). Side effects, most of them mild, occurred in 57%; only 9 patients required discontinuation of drug therapy. The risk of developing adverse reactions was related to serum amiodarone concentrations (p less than 0.0001). Adverse reactions were common in patients with serum values exceeding 2.5 mg/L, although pulmonary complications did occur at lower concentrations. Monitoring serum amiodarone concentrations may differentiate failure of drug therapy from suboptimal dosing and reduce the incidence of concentration-related side effects.

Adult↗
PubMed1983

Relation between late potentials on the body surface and directly recorded fragmented electrograms in patients with ventricular tachycardia.

The relation between low-amplitude, late potentials on the body surface and directly recorded electrograms in 8 patients with and 11 patients without ventricular tachycardia (VT) was studied. Bipolar X,Y,Z leads were signal-averaged and filtered with a digital technique. All patients had catheter endocardial left ventricular maps. The VT group had medically intractable VT and an endocardial excision was performed for control of VT. Before bypass, epicardial maps were obtained in the operating room. All studies were performed during normal sinus rhythm. Four patients without VT, each with a previous myocardial infarction, had fragmented endocardial electrograms recorded at 2.0 +/- 1.2 sites. The latest electrogram for each patient ended 87 +/- 8 ms after QRS onset, within the high-amplitude portion of the filtered QRS complex. All patients with VT had fragmented electrograms recorded at 6.1 +/- 3.1 sites/patient. Eighty-eight percent of the fragmented electrograms were endocardial. The latest fragmented electrogram for each patient ended 161 +/- 43 ms after QRS onset, significantly later than the fragmented electrograms from the patients without VT (p = 0.002). Six VT patients had low-amplitude, late potentials at the end of the filtered QRS complex. In these patients, the last 40 ms of the filtered QRS complex contained a higher proportion of fragmented electrograms compared with earlier segments of the QRS complex (68% versus 27%, p less than 0.001). Two patients with VT did not have late potentials. One patient with left bundle branch block had delayed left ventricular epicardial activation which masked the fragmented electrograms. The other had fragmented electrograms of brief duration which ended 80 +/- 12 ms after QRS onset, during the time of normal ventricular activation. It is concluded that the late potential corresponds to delayed, fragmented electrographic activity. Failure to record a late potential may arise from delayed ventricular activation at other sites from bundle branch block or fragmented electrograms of a brief duration.

Adolescent↗
PubMed1983

Ventricular arrhythmias: use of electrophysiologic studies.

The clinical utility of electrophysiologic testing in assessing the long-term efficacy of amiodarone for treatment of life-threatening ventricular arrhythmias is controversial, most investigators reporting little or no correlation between the early effects of the drug on arrhythmia inducibility and subsequent prognosis. We have evaluated 69 consecutive patients given amiodarone for ventricular tachycardia (VT) or fibrillation (VF). All patients underwent provocative electrophysiologic testing with programmed electrical stimulation before and after amiodarone loading. After a standardized amiodarone loading regimen, the patients' arrhythmias were not inducible in 22 patients (group 1) and remained inducible in 47 patients (group 2). No patient in group 1 has had a recurrence of VT/VF, whereas 15 (32%) of 47 patients in group 2 have had recurrences. The characteristics of the arrhythmia induced by programmed stimulation in group 2 accurately predicted the severity of the recurrence. We conclude that electrophysiologic testing may be useful in evaluating the efficacy of amiodarone for the long-term treatment of VT/VF and that its precise role in this context should be further investigated by stringently controlled studies.

Adult↗
PubMed1983

Predictors of the success or failure of medical therapy in patients with chronic recurrent sustained ventricular tachycardia: a discriminant analysis.

To identify predictors of the success or failure of medical therapy in chronic recurrent sustained ventricular tachycardia, univariate and multivariate statistical techniques were used to retrospectively analyze data in 84 patients with this arrhythmia. By univariate analysis, four factors were associated with successful medical treatment: age less than 45 years, ejection fraction greater than 50%, hypokinesia as the only contraction abnormality and the absence of organic heart disease. Four other findings, the induction of ventricular tachycardia with a single ventricular extrastimulus, an HV interval greater than 60 ms, the presence of a left ventricular aneurysm and Q waves on a baseline electrocardiogram, correlated with medical failure. However, none of these variables alone accurately predicted treatment results in more than 75% of cases. By discriminant analysis, a function incorporating eight variables was constructed which correctly classified 81% of patients. Moreover, three-quarters of the patients could be classified into groups with a high or low probability of success where accuracy increased to 90%. When the discriminant function was tested prospectively in 31 similar patients, 25 (81%) fell into the groups with a high or low probability of success. In the latter group, of 20 patients predicted to fail medical therapy, 19 (95%) did fail a complete trial of medical therapy. The overall accuracy remained a high 92%. In clinical application this function would allow patients with a high probability of responding to medical therapy to be selected for serial electrophysiologic drug testing. In patients with a low probability of responding to medical therapy, serial studies could be avoided and alternate forms of therapy explored.

Anti-Arrhythmia Agents↗
PubMed1982

Role of programmed stimulation in assessing vulnerability to ventricular arrhythmias.

Programmed electrical stimulation can now be safely performed in humans for the evaluation of therapy for recurrent ventricular tachyarrhythmia. Such studies may also eventually be found useful in predicting the risk of developing life-threatening ventricular tachyarrhythmias. The repetitive ventricular response phenomenon has been evaluated. Although an association between the intraventricular reentrant phenomenon and sustained ventricular tachyarrhythmias has been found, its predictive value in a population at risk is not sufficient for use in clinical decision making. On the other hand, the initiation of sustained ventricular tachycardia or fibrillation appears closely related to its actual spontaneous clinical occurrence. Serial electrophysiologic studies can be performed and are effective in prospectively evaluating the response to antiarrhythmic drugs. The efficacy of therapy based on the results of programmed stimulation appears to be good.

Anti-Arrhythmia Agents↗
PubMed1982

Role of catheter mapping in the preoperative evaluation of ventricular tachycardia.

Although surgery is an accepted mode of therapy for refractory ventricular tachycardia, routine aneurysmectomy has yielded unpredictable results. This is believed to have occurred because there was no documentation that the arrhythmia actually arose from resected aneurysmal tissue. Catheter endocardial mapping has been used to localize preoperatively the area of origin of the arrhythmia. This technique has established that the arrhythmias arise near the endocardium at the borders of the aneurysm or infarction, or both. These regions, particularly when they occur in the interventricular septum, are not resected by standard aneurysmectomy. Intraoperative endocardial and epicardial mapping have validated the accuracy of this technique. We believe that catheter mapping should be performed before surgery for the following reasons: (1) In some patients ventricular tachycardia is not inducible in the operating room (for example, automatic ventricular tachycardia can be mapped in the catheterization laboratory); (2) in some patients not all morphologic forms of tachycardia can be induced or mapped intraoperatively because of failure of inducibility, time constraints or degeneration of the arrhythmia to ventricular fibrillation; and (3) intraoperative endocardial mapping occasionally cannot be performed because of lack of technical skills, physical factors such as mural thrombosis, or the inability to induce ventricular tachycardia after aneurysmectomy. Other methods currently being evaluated to localize the origin of ventricular tachycardia that do not require induction of arrhythmia are analysis of ventricular electrograms during sinus rhythm and pacemapping.

Cardiac Catheterization↗
PubMed1982

Intravenous nitroglycerin for rest angina. Potential pathophysiologic mechanisms of action.

Twenty patients with refractory rest angina pectoris were treated with intravenously (IV) administered nitroglycerin (mean dosage, 72.4 micrograms/min; range, 15 to 226 micrograms/min). There was a considerable reduction or abolition in the number of ischemic episodes in 85% of patients without overall substantial changes in heart rate, mean arterial BP, pulmonary capillary wedge pressure (PCWP), and pulmonary arterial mean pressure. However, those patients with an initial PCWP of more than 12 mm Hg or a systolic pressure of more than 130 mm Hg had a substantial reduction in PCWP and systolic BP following IV nitroglycerin. We conclude that IV nitroglycerin may relieve rest angina by different pathophysiologic mechanisms. In some patients, IV nitroglycerin favorably altered the hemodynamic determinants of myocardial oxygen consumption. In others, however, no change in these determinants occurred, suggesting a direct effect on the coronary circulation.

Adolescent↗
PubMed1981

Human ventricular refractoriness: effects of increasing current.

The ventricular effective refractory period is commonly employed as a measurement of ventricular excitability. Because the current strength used to make this determination varies among laboratories, the relation of refractoriness and current was examined over a range of current strengths from 0.1 to 10 mA. Sixty determinations of refractoriness at variable current strengths were made in 40 patients using the extrastimulus technique with a rectangular pulse of 1 ms duration. These data were obtained by measuring the effective refractory period at threshold current and at 0.25 to 0.50 mA increments from threshold up to 10 mA. In these studies the drive stimulus (S1) and extrastimulus (S2) were kept at the same amplitude. In all patients the ventricular effective refractory period decreased as the current increased. The total decrease ranged from 8 to 100 ms (mean +/- standard deviation 36.9 +/- 17.1). The current strength at which the ventricular effective refractory period became fixed (that is, less than 2 ms change in ventricular effective refractory period with further increase in current strength) varied among the patients, but in all instances equaled or exceeded 1.8 mA, which in all but three patients was greater than three times threshold. The curves relating current strength and refractoriness were shifted to the left at shorter cycle lengths with no change in threshold. These data suggest that (1) current strength-effective refractory period curves more completely characterize ventricular excitability than does a ventricular effective refractory period at single current strength; and (2) studies of drug effects, alterations of autonomic tone, or reentrant arrhythmias, which may affect or are affected by ventricular refractoriness, may be enhanced by more complete measurements of refractoriness afforded by the current strength-effective refractoriness curves.

Adolescent↗
PubMed1981

Anatomic and electrophysiologic correlates of ventricular tachycardia requiring left ventricular stimulation.

In 108 patients with reproducible initiation of ventricular tachycardia by programmed ventricular stimulation, the ventricular tachycardia was initiated only by left ventricular stimulation in 12 (11 percent). Programmed ventricular stimulation included single and double extrastimuli extrastimuli at three cycle lengths and bursts of rapid pacing to cycle lengths of 250 ms. Clinical, electrocardiographic, angiographic, hemodynamic and electrophysiologic data were available in 74 of 96 patients with ventricular tachycardia initiated by right ventricular stimulation (Group A) and in all 12 patients with ventricular tachycardia initiated only by left ventricular stimulation (Group B). there were no significant differences between Groups A and B in clinical characteristics, hemodynamics or presence and site of infarction or aneurysm. Comparison of electrophysiologic variables revealed no significant differences between Groups A and B mean A-H interval (92 +/- 22 versus 89 +/- 15 ms, respectively), H-V interval (59 +/- 15 versus 59 +/- 15 ms) or right ventricular (241 +/- 38 versus 260 +/- 40 ms) or left ventricular (232 +/- 28 versus 251 +/- 42 ms) effective refractory period. Ventricular tachycardia with right bundle branch block and superior axis was more prevalent in Group B (92 percent versus 31 percent, p less than 0.001) but was observed in 32 patients in Group A. It is concluded that 11 percent of patients with clinically documented sustained ventricular tachycardia will require left ventricular programmed stimulation to reproducibly initiate the tachycardia. No clinical, anatomic, electrocardiographic or electrophysiologic features can predict whether left ventricular programmed stimulation will be required. Because initiation of ventricular tachycardia by programmed ventricular stimulation has important prognostic and therapeutic implications in such patients, stimulation should be performed from the left ventricle when the tachycardia is not initiated by stimulation from the right ventricle.

Adolescent↗
PubMed1981

Torsades de pointes: electrophysiologic studies in patients without transient pharmacologic or metabolic abnormalities.

Electrophysiologic studies were performed in 21 patients who had torsades de pointes. This ventricular tachyarrhythmia, characterized by rapid (200-250 beats/min) and irregular paroxysms and progressively varying QRS amplitude and polarity, occurred in the absence of electrolyte disturbance, antiarrhythmic drug therapy or acute ischemia. The QTc interval was prolonged in seven of 21 patients. Electrophysiologic study included ventricular pacing with the introduction of one to three extrastimuli and rapid ventricular pacing. The effect of i.v. procainamide or quinidine in these patients was also studied. Torsades de pointes was inducible n 19 of 21 patients. Induced episodes closely resembled spontaneous episodes. Torsades de pointes spontaneously progressed to ventricular tachycardia with a uniform morphology in three patients and to ventricular fibrillation in four. In eight patients, procainamide or quinidine converted torsades de pointes into typical reentrant ventricular tachycardia. Our data suggest that torsades de pointes in this setting may be a rapid reentrant ventricular tachycardia closely related to recurrent sustained ventricular tachycardia and a precursor to ventricular fibrillation and sudden death.

Adult↗
PubMed1981

One-to-two atrioventricular conduction in Wolff-Parkinson-White syndrome: a mechanism of initiating supraventricular tachycardia.

A patient with Wolff-Parkinson-White syndrome and recurrent supraventricular tachycardia manifested the unusual finding of two ventricular responses to a single atrial depolarization. The second response occurred due to delay in the His-Purkinje system (H-V prolongation). This phenomenon was a mechanism of initiation of supraventricular tachycardia, not previously described to our knowledge.

Adult↗
PubMed1980

Electrophysiologic and hemodynamic studies in patients resuscitated from cardiac arrest.

Fifty-two patients resuscitated from cardiac arrest underwent electrophysiologic studies. The earliest documented arrhythmia at the time of initial or recurrent (18 patients) cardiac arrest was ventricular fibrillation (30 patients) or ventricular tachycardia (20 patients); in 2 patients no arrhythmia was documented before defibrillation. Programmed ventricular stimulation revealed inducible arrhythmias in 33 patients (63 percent). Of the 30 patients with ventricular fibrillation as the initial arrhythmia, 13 had inducible arrhythmias--ventricular fibrillation (4 patients), sustained ventricular tachycardia (6 patients) and nonsustained ventricular tachycardia (3 patients). In the 20 patients with ventricular tachycardia as the initial arrhythmia, sustained ventricular tachycardia was initiated in 17 patients and torsade de pointes in 1. Patients with inducible arrhythmias had longer mean A-H and H-V intervals than those without inducible arrhythmias (91.1 versus 76.6 ms and 62.5 versus 50.3 ms, respectively). Prolonged H-V intervals (17 of 33) and intraventricular conduction defects (18 of 33) were more common in patients with than in those without inducible arrhythmias (4 of 19 and 7 of 19, respectively). Mean cardiac index was lower (2.4 versus 3.9 liters/min per m2), left ventricular end-diastolic pressure higher (17.0 versus 9.4 mm Hg), and ejection fraction lower (36.1 versus 57.2 percent) in the group with inducible arrhythmias than in those in whom no arrhythmia could be induced. These data suggest that (1) ventricular tachycardia often precipitates cardiac arrest; and (2) electrophysiologic testing may provide data on which to base therapy in patients resuscitated from cardiac arrest.

Adult↗