Stephen Schmaltz - Academia.edu (original) (raw)

Papers by Stephen Schmaltz

Alcoholism-clinical and Experimental Research, 1992

The purpose of the this study was to develop an instrument for measuring the obsessive and compul... more The purpose of the this study was to develop an instrument for measuring the obsessive and compulsive characteristics of drinking-related thought and behavior in subjects who abuse or are dependent on alcohol, and to quantify the extent to which drinking-related thought and behavior in these subjects resemble the obsessions and compulsions seen in obsessive-compulsive disorder (OCD). To achieve these goals, the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was modified to reflect obsessionality and compulsivity specifically related to heavy drinking rather than to obsessions and compulsions generally. The modified Y-BOCS (Y-BOCS-hd) was administered to 62 subjects satisfying DSM-III-R criteria for alcohol abuse or alcohol dependence and 62 matched normal controls. The data showed that the Y-BOCS-hd is a sensitive and specific instrument for measuring the obsessive and compulsive characteristics of drinking-related thought and behavior in alcohol-abusing and alcohol-dependent populations, and that there are specific and quantifiable similarities between these characteristics and the obsessions and compulsions of OCD. The data also indicated that the Y-BOCS-hd may be a useful screening instrument for the presence of alcohol abuse and dependence.

Objective: To determine the positive predictive value of International Classification of Disease,... more Objective: To determine the positive predictive value of International Classification of Disease, 9th Revision, Clinical Modification (ICD-9-CM) discharge codes for acute deep vein thrombosis or pulmonary embolism. Materials and Methods: Retrospective review of 3456 cases hospitalized between 2005 and 2007 that had a discharge code for venous thromboembolism, using 3 sample populations: a single academic hospital, 33 University HealthSystem Consortium hospitals, and 35 community hospitals in a national Joint Commission study. Analysis was stratified by position of the code in the principal versus a secondary position. Results: Among 1096 cases that had a thromboembolism code in the principal position the positive predictive value for any acute venous thrombosis was 95% (95%CI:93-97), whereas among 2360 cases that had a thromboembolism code in a secondary position the predictive value was lower, 75% (95%CI:71-80). The corresponding positive predictive values for lower extremity deep-vein thrombosis or pulmonary embolism were 91% (95%CI:86-95) and 50% (95%CI:41-58), respectively. More highly defined codes had higher predictive value. Among codes in a secondary position that were false positive, 22% (95%CI:16-27) had chronic/prior venous thrombosis, 15% (95%CI:10-19) had an upper extremity thrombosis, 6% (95%CI:4-8) had a superficial vein thrombosis, and 7% (95%CI:4-13) had no mention of any thrombosis. Conclusions: ICD-9-CM codes for venous thromboembolism had high predictive value when present in the principal position, and lower predictive value when in a secondary position. New thromboembolism codes that were added in 2009 that specify chronic thrombosis, upper extremity thrombosis and superficial venous thrombosis should reduce the frequency of false-positive thromboembolism codes.

Therapeutic Drug Monitoring, 1984

ABSTRACT

American Journal of Cardiology, 1990

Journal of The American College of Cardiology, 1988

EF.2 = cpmrphnnc. ously have been demonstrated to result in physiologic elevations in the plasma ... more EF.2 = cpmrphnnc. ously have been demonstrated to result in physiologic elevations in the plasma cpinephrine concentration (6). To determine whether the etTects of epincphrine are influenced by the presence of heart disease, two groups of subjects were studied. one without and one with structural heart disease.

$Research paper thumbnail of Variability in the Measurement of Human Ventricular Refractoriness$

Pace-pacing and Clinical Electrophysiology, 1991

The degree of variability in ventricular refractoriness and factors potentially affecting this va... more The degree of variability in ventricular refractoriness and factors potentially affecting this variability were evaluated in 80 patients undergoing an electrophysiological study. Each of seven variables fstimulation current, coupling interval of the basic drive train to spontaneous rhythm, pause between determinations, bipolar pacing configuration, bipolar vs unipolar pacing, atrioventricular synchrony, and autonomic tone) was evaluated in a group of ten patients to determine its effects on the reproducibility of refractoriness. Measurements were repeated ten times in every patient under each of two conditions. Five variables had significant effects on the reproducibility of measurements. Pacing at 10 mA was associated with less variability in the determination of ventricular refractoriness than pacing at twice threshold (within-subject variance component 4.5 vs 10.1 msec; P < 0.001). The mean difference between the longest and shortest determinations of refractory periods (range) was 6.2 msec at 10 mA and 8.6 msec at twice threshold. The use of a conditioning period of pacing and continuous trains (eight beats with a 3-sec pause) rather than a variable pause between serial trials reduced the mean within-subject variance component from 16.5 to 3.3 (P < 0.001) and the mean range of refractory period determinations from 10.8 to 4.8. The use of the distal rather than the proximal pole as the cathode decreased the mean within-subject variance component from 9.4 to 3.3 (P < 0.001) and the range of determinations from 6.4 to 5.8 msec. Unipolar pacing was associated with less variability than bipolar pacing (mean within-subject variance component 4.6 vs 6.4; P < 0.05, mean range 5.0 vs 7.6 msec). In patients with ventriculoatrial dissociation, atrioventricular simultaneous pacing during the basic drive train decreased the within-subject variance component from 21.2 to 5.7 (P < 0.001) and the mean range of refractory periods from 12.2 to 6.8 msec (P < 0.05). In an eighth group of patients, the significant variables were set to create either the greatest or least variability in refractoriness in order to determine the effects of controlling these factors. Bipolar pacing was used in this group of patients. The within-subject variance component decreased from 31.7 to 3.5 (P < 0.01) and the mean range of refractory period determinations decreased from 15.8 to 4.4 msec (P < 0.01) when the variables found to affect the reproducibility of refractoriness were set in a fashion to decrease variability. In conclusion: (1) Conventional measurement of ventricular refractoriness often is associated with variability in the range of 10–15 msec (2) Pacing at 10 mA, unipolar rather than bipolar pacing, atrioventricular synchrony during basic drive trains, a large number of trains before refractoriness is reached, and bipolar distal cathodal pacing decrease this variability and provide greater reproducibility in the measurement of ventricular refractoriness.

American Journal of Cardiology, 1990

iuiD, and bed h~oiady, MD R ecent studies have shown a decrease in the amplitude of intracardiac ... more iuiD, and bed h~oiady, MD R ecent studies have shown a decrease in the amplitude of intracardiac electrograms during exercise in patients with permanent pacemakers.'-3 However, the mechanism by which exercise decreases the amplitude of the intracardiac electrograms has not been investigated. Because exercise is associated with both an increase in heart rate and an increase in circulating catecholamines,4q5 the purpose of this study was to determine how these factors influence the amplitude of the atria1 and ventricular electrograms.

Journal of The American College of Cardiology, 1990

American Journal of Cardiology, 1990

$Research paper thumbnail of Effect of Interelectrode Distance on the Bipolar Strength-Interval Relationship and Ventricular Effective Refractory Period in Humans$

Journal of Cardiovascular Electrophysiology, 1990

Effect of Interlectrode Spacing The purpose of this study was to compare the effects of interelec... more Effect of Interlectrode Spacing The purpose of this study was to compare the effects of interelectrode distaices of 1 cm and 0.5 cm on the ventricular effective refractory period (VERP) and the strength-interval relationship during bipolar cathodal pacing. A quadripolar electrode catheter with an interelectrode spacing of 0.5 cm was positioned at the right ventricular apex in 30 subjects, and the VERP was measured in 2-msec steps at twice the late diastolic threshold using bipolar cathodal pacing, first with an electrode spacing of I cm, then 0.5 cm. With the technique used in this study, there was up to 4 msec of variability in the measured VERP. Therefore, a change in the VERP of at least 6 msec was required before concluding that the interelectrode distance had affected the measured VERP In 15 subjects (group 1), the VERP was not affected by a change in electrode spacing; in nine subjects (group 2) the VERP was 6–10 msec longer with the 0.5 cm spacing than with the 1-cm spacing, and in six subjects (group 3) the VERP was 6–12 msec longer with the 1.0-cm spacing than with the 0.5-cm spacing. Determination of unipolar strength-interval curves in ten other subjects demonstrated that anodal curves can be distinguished from cathodal curves by the presence of an early diastolic dip and by the occurrence of the ascent of the curve at a longer extrastimulus coupling interval. These features were used as markers of an anodal contribution to the bipolar strength-interval curves in groups 1, 2, and 3. In subjects in whom there was a difference in the VERP with the two electrode spacings, an anodal contribution to the bipolar strength interval curve was always identifiable in the curve generated with the electrode spacing that had yielded the longer VERP With the bipolar configuration that yielded the longer VERP, the unipolar stimulation threshold at the anode was always 1.6 mA and was always lower than the anodal threshold of the bipolar configuration that yielded the shorter VERP. In conclusion, the VERP may either lengthen or shorten by up to 10–12 msec when the interelectrode distance is changed from 1 to 0.5 cm during bipolar cathodal pacing. The effect of electrode spacing on the measured VERP is attributable to position-dependent effects on the unipolar anodal stimulation threshold. A lower anodal threshold may result in a greater degree of anodal contribution during bipolar pacing, manifest by the occurrence of the ascent of the strength-interval curve later in diastole and a corresponding increase in the VERP measured at a current strength of twice the late diastolic threshold. (J Cardiovasc Electrophysiol, Vol. 1. pp. 103–115, April 1990)

Journal of The American College of Cardiology, 1991

To examine the spatial resolution of unipular pace-mapping . 12 lead electrocardiograms (ECGs) re... more To examine the spatial resolution of unipular pace-mapping . 12 lead electrocardiograms (ECGs) recorded during pacing from each of the poles of a quadrlpolar catheter 13 mm Imerelectrode distance) were examined . Iintpolar pacing was performed Iron, each of the poles at late diastolic threshold. twice threshold and 10 etA at a cycle leng".h or 5W ms-In i5 patients, paziaw vas performed at the right ventricular apex and In 14 at nations left ventricular shes. Paring from The distal catheter pole at threshold )index ECGS was used to simulate the silt of origin of venicular mehyeardia, and all other FCC% were compared with the index EC(, Electrocardiograms were evaluated by two independent ohservers for 1) miser configuration difference, match, new small component, change in the amplitude or individual components or change in QRS shape); 2) major differences in configuration /new large component, marked change in the amplitude of an existing component or Iwo minor changes) : and 3Y peak to peak chaopes in amplitude.

$Research paper thumbnail of The Maximum Effect of an Increase in Rate on Human Ventricular Refractoriness$

Pace-pacing and Clinical Electrophysiology, 1988

The purpose of this study was to determine the maximum shortening of ventricular refractoriness t... more The purpose of this study was to determine the maximum shortening of ventricular refractoriness that occurs following an increase in rate and to quantitate the duration of ventricular pacing required to obtain this maximum shortening of refractoriness. The subjects of the study consisted of 41 patients who underwent a clinically indicated electrophysiologic study. Ventricular refractory periods were measured with an extrastimulus (S2) at basic cycle lengths of 600 and 400 ms by Method A (8 beat basic drive trains and 4 second intertrain paue and Method B (drive train duration of 3 minutes, then an S2 after every eighth basic drive beat, with no pause after the S2). In 23 subjects, the mean ventricular effective refractory period determined by Method B was 12 ± 7 ms (± standard deviation) shorter than when determined by Method A at a basic drive cycle length of 600 ms (p < 0.0001] and 33 ± 9 ms shorter at a basic drive cycle length of 400 ms (p < 0.001]. In these 23 subjects, the drive train duration required for maximum shortening of ventricular refractoriness was estimated by counting the number of drive train beats preceding ventricular capture by an S2 inserted after every fourth basic drive beat at a coupling interval fixed at 5 ms longer than the ventricular effective refractory period determined in that subject by Method B. The mean number of basic drive beats preceding capture by S2 was 114 ±84 beats at a basic drive cycle length of 600 ms and 233 ± 85 beats at a BDCL of 400 ms. In six subjects the ventricular effective refractory period was measured by Methods A and B before and after autonomic blockade with propranolol and atropine, and the amount of shortening in the ventricular effective refractory period with Method B was not affected by autonomic blockade. In conclusion, the basic drive train has a cumulative effect on ventricular refractoriness in humans, and a drive train duration substantially longer than 50 beats often is required to obtain the maximum shortening of ventricular effective refractory period after an increase in rate. Therefore, ventricular effective refractory periods determined conventionally using 8 beat drive trains and a 4 second intertrain pause often may be overestimates of the actual ventricular effective refractory period. The shortening of ventricular refractoriness with long drive train durations is probably related to a prolonged duration of pacing required to obtain a steady-state action potential duration after an increase in rate.

American Journal of Cardiology, 1989

BRIEF REPORTS was effective for controlling 64% of patients, with partial control achieved in an ... more BRIEF REPORTS was effective for controlling 64% of patients, with partial control achieved in an additional 13%. The incidence of side effects necessitating drug withdrawal was 15%. In the study of Hammill et al, most patients (60%) had no significant cardiovascular disease, while 74% of Kerr's group had primary AF without associated heart disease. We had a lower success rate than these 2 previous groups, but our patient population all had underlying heart disease and chronic AF. The arrhythmia may have been more difficult to control due to these 2 vaiiables. cardia. Am J Cardiol 1983;S2:1208ml 213. 2. Podrid PJ, Lown BL. Propafenone: a new agent for ventricular arrhythmia. JACC 1984:4:117-l 25. 3. Dinh Ha, Baker BJ, De Soyza N, Murphy ML. Sustained therapeutic efficacy and safety of oral propafenone for treatment of chronic ventricula;arrhythmia: a 2-year experience. Am Heart J 1988;115:92-96. 4. Manz M, Steinbeck G, Luderitz B. Usefulness of programmed stimulation in predicting efficacy of propafenone in long-term antiarrhythmic therapy for paroxysmal supraventricular tachycardia. Am J Cardiol 1985;56:595-597. 5. Hammill SC, McLaran CJ, Wood DL, Osborn MJ, Gash BJ, Holmes DR. Double-blind study of intravenous propafenone for paroxysmal supraventricular reentrant tachycardia. JACC

$Research paper thumbnail of Comparison of Ventricular Refractory Periods Determined by Incremental and Decremental Scanning of an Extrastimulus$

Pace-pacing and Clinical Electrophysiology, 1989

This study compared the ventricular effective refractory periods measured by scanning diastole wi... more This study compared the ventricular effective refractory periods measured by scanning diastole with an extrastimulus in incremental and decrementaJ steps of 5 msec. The subjects of the study were 80 patients undergoing a clinically indicated electrophysiological test. Eight beat basic drive trains at a cycle length of 600 msec and an intertrain pause of 4 seconds were used to measure the ventricular effective refractory period (VERP). In the incremetal method, the extrastimulus initially was positioned at a coupling interval shorter than the VERP and the coupling interval then was progressively increased until ventricular capture occurred. In the decremental method, the initial extrastimulus coupling interval was longer than the VERP and the coupling interval was progressively shortened until ventricular capture was lost. In 50 subjects, the mean VERP determined by the incremental method, 252 ± 18 (± standard deviation), was significantly longer than the mean VERP determined in the same patients by the decremental method, 248 ± 18 msec (P < 0.0001). In ten subjects, a subthreshold stimulus (S') positioned 10 msec earlier than the VERP had an inhibitory effect that lengthened the VERP by an average of 7 msec; however, when S' was positioned after the seventh beat of an eight heat drive train, no inhibitory effect could be demonstrated. In 20 subjects, VERP's were determined by the incremental and decremental methods using intertrain pauses of 1, 4, 8, 12, and 20 seconds. The mean VERP measured by the incremental method was significantly less than the mean VERP measured by the decremental method when the intertrain pause was 1,4, or 8 seconds, but not when the pause was 12 or 20 seconds. The results of this study demonstrate that incremental scanning of an extrastimulus with eight beat basic drive trains yields a longer VERP than when the extrastimulus is scanned in decremental fashion. The discrepancy between the two methods is not attributable to inhibition by noncapturing extrastimuli in the incremental method, but rather to a decrease in the VERP caused by an effect of extrastimuli that capture the ventricle in the decremental method. Therefore, when a conventional eight beat driye train and 4 second intertrain pause are used to measure ventricular refractoriness, incremental scanning of an extrastimulus yields a more accurate VERP than does decremental scanning.

Pace-pacing and Clinical Electrophysiology, 1993

Two hundred eighty patients with spontaneous nonsusfained ventricular tachycardia were treated ba... more Two hundred eighty patients with spontaneous nonsusfained ventricular tachycardia were treated based on the results of electrophysiological testing. Seventy-nine patients had no evidence of structural heart disease, 134 had coronary artery disease, 43 had idiopathic dilated cardiomyopathy, and 24 patients had miscellaneous types of heart disease. Sustained monomorphic ventricular tachycardia was induced during electrophysiological testing in the drug free state in 52 of 280 patients (19%). Ventricular tachycardia was induced more frequently in patients with coronary artery disease (32%) than in any of the other groups (P < 0.001). The patients with inducible sustained monomorphic ventricular tachycardia underwent a mean of 1.9 ± 1.3 drug trials. Twenty-five patients had the induction of ventricular tachycardia suppressed by pharmacological therapy and were treated with the drug judged to be effective during electropharmacological testing. Twenty-seven patients continued to have inducible sustained monomorphic ventricular tachycardia despite antiarrhythmic therapy and were discharged on the drug that made induced ventricular tachycardia best tolerated. Forty-five of 280 patients (16.1%) died during a mean follow-up period of 19.6 ± 14.4 months, There were 15 sudden cardiac deaths, 21 nonsudden cardiac deaths, 6 noncardiac deaths, and 3 deaths that could not be classified. Sudden cardiac death mortality was lowest in the patients without structural heart disease (0% at 2 years), intermediate in the patients with coronary artery disease and miscellaneous heart disease (4% al 2 years), and highest in the patients with idiopathic dilated cardiomyopathy (13% at 2 years; P < 0.01 for pairwise comparisons). No patient treated with a drug that had suppressed the induction of sustained ventricular tachycardia died suddenly during the follow-up period whereas four of 27 patients who were discharged on “ineffective antiarrhythmic drugs” and 11 of 228 patients without inducible sustained ventricular tachycardia experienced sudden cardiac death during the follow-up period. By multivariate analysis, ejection fraction and inducible ventricular tachycardia during the predischarge eiectrophysiological test were independent predictors of sudden cardiac death. In conclusion, in patients with spontaneous nonsustained ventricular tachycardia: (1) Arrhythmia inducibility varies depending on the underlying heart disease. Ventricular tachycardia is most often inducible in patients with coronary artery disease and least often in patients without structural heart disease; (2) With the exception of patients with idiopathic dilated cardiomyopathy, management of patients with nonsustained ventricular tachycardia guided by electrophysiological testing appears to result in a low incidence of sudden cardiac death although effects on total mortality are less impressive; and (3) Patients with idiopathic dilated cardiomyopathy and patients with other heart diseases who continue to have inducible ventricular tachycardia despite antiarrhythmic drug therapy are at substantial risk of sudden cardiac death.

Journal of Cardiovascular Electrophysiology, 1989

This study determined the effects of a wide range of basic drive cycle lengths on the induction o... more This study determined the effects of a wide range of basic drive cycle lengths on the induction of ventricular tachycardia (VT) by a single extrastimulus (S2). Seventy-one patients with coronary artery disease and inducible sustained monomorphic VT underwent 121 electrophysiology tests either in the control state or during treatment with an antiarrhythmic drug. Ventricular basic drive trains were eight beats in duration and the intertrain interval was three seconds. Programmed ventricular stimulation was performed with S2 using the longest possible basic drive cycle length rounded off to the nearest multiple of 100 msec, then using basic drive train cycle lengths that decreased in 100 msec steps to 400 msec, and finally using a basic drive cycle length of 350 msec. At each drive cycle length, an interval of > 50 msec beyond the effective refractory period (ERP) was scanned with S2. Monomorphic VT was induced by S2 in 52/121 studies (43%). The drive cycle length had a significant linear effect on the log odds of inducing VT (P < 0.0001). The highest yield of VT occurred with a drive cycle length of 350 msec (42/121, 34%), and with each increment in drive cycle length, the expected odds of inducing VT decreased by a factor of 1.7. In 88% of cases in which VT was induced at a particular drive cycle length but not at longer drive cycle lengths, the coupling intervals that induced VT exceeded the ERP measured at one or more of the longer basic drive cycle lengths. In conclusion, there is an inverse relationship between the basic drive cycle length and the yield of monomorphic VT induced by S2. The use of shorter basic drive cycle lengths often facilitates the induction of VT by some effect other than critical shortening of the S2 coupling interval.

$Research paper thumbnail of Effect of the Intertrain Pause on the Ventricular Effective Refractory Period Measured by the Extrastimulus Technique$

Pace-pacing and Clinical Electrophysiology, 1990

This study determined the effect of the duration of the intertrain pause on the ventricular elect... more This study determined the effect of the duration of the intertrain pause on the ventricular elective refractory period (VERP) measured by the extrastimulus technique using conventional eight-beat basic drive trains. In 50 subjects, the VERP was measured using a basic drive train cycle length of 500 msec, 2-msec steps in the extrastimulus coupling interval, and intertrain pauses of 0, 1, 4, 8, 20, 40, 60, or 380 seconds. The VERP increased significantly with each stepwise increment in the intertrain pause up to 20 seconds, then reached a plateau. The VERP measured with an intertrain pause of 20 seconds was a mean of 13 msec longer than when measured with a conventional 4-second pause. The results of this study demonstrate a direct relationship between the VERP and the duration of the pause separating the eight-beat basic drive trains used to measure the VERP. When the cycle length of the basic drive train is 500 msec, the VERP lengthens as the duration of the intertrain pause increases from 1 to 20 seconds, demonstrating that the basic drive trains exert a cumulative effect on the VERP when the intertrain pause is shorter than 20 seconds. A cumulative effect of the basic drive trains on the VERP is lost when the intertrain pause is 20 seconds or more.

Journal of The American College of Cardiology, 1988

The purpose of this study was to determine whether pharmacologically induced elevations In the pl... more The purpose of this study was to determine whether pharmacologically induced elevations In the plasma epinephrine concentration within reported physiologic limits oiler the response t quinidine during dedropbarmacologic testing . Twenty-one patients with coronary artery disease and a history of unimorphle ventricular taehyeordla were found to have inducible sustained unimorphie ventricular tachycardia that was suppressed by treatment with oral quint. dine gluconate. Epinepbrine was Then infused at a rate of either 25 or 50 ng/kg per min and testing was repeated . These infusion rates of epinephrine were previously dem. contrasted to result in elevations of the plasma epinephrine concentration In the range of concentrations that occur during a variety of stresses .