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Biomedical subjects

S F Schaal

Publications and source records attributed to S F Schaal.

At least 37 records · Page 2Linked to original sources
PubMed1985

Electrophysiologic mechanisms of provoked atrial flutter in mitral valve prolapse syndrome.

To examine the electrophysiologic determinants of provoked atrial flutter (AF) in patients with mitral valve prolapse (MVP), studies were performed in 4 groups of patients: group 1 (n = 5), patients with MVP and AF; group 2 (n = 6), patients without MVP but with AF; group 3 (n = 6), patients with MVP but without AF; and group 4 (n = 5), patients without MVP and without AF. P-wave duration, intraatrial conduction, interatrial conduction and effective refractory periods for both the high right atrium and the low right atrium were longer in group 2 than in group 1. The effective refractory period of the low right atrium was longer in group 3 than in group 1. The interatrial conduction interval was longer in group 2 than in group 4. Thus, in patients without MVP, atrial conduction delay is the predominant determinant of AF, whereas differences in right atrial refractoriness appear to be most important to the provocation of AF in the patient with MVP. These differences in atrial refractoriness may be a result of abnormal autonomic influences in patients with MVP.

Adolescent↗
PubMed1985

Meobentine sulfate: antiarrhythmic and electrophysiologic effects assessed by programmed electrical stimulation and ambulatory monitoring in patients with complex ventricular tachyarrhythmia. Report of a multicenter evaluation.

Five cardiology centers conducted open-label prospective trials of meobentine sulfate, an intravenously and orally available analog of bethanidine, to assess its potential for treatment of recurrent, drug refractory ventricular tachycardia (VT) or fibrillation (VF), and complex ventricular arrhythmias. The study population comprised 26 patients (mean age, 61 years); 18 were men. Coronary artery disease was present in 15, cardiomyopathy in six, and valvular heart disease in three. Patients presented with both VT and VF (seven), sustained VT alone (12), or frequent ventricular ectopy (PVCs) and nonsustained VT (seven). Of the 26 patients, 5 were enrolled in antiarrhythmic studies (chronic PVC suppression) and 21 were enrolled in programmed electrical stimulation (PES) studies. Two of five in the chronic PVC study showed greater than 75% arrhythmia suppression. Among 21 patients in PES studies, there were eight intravenous (16 mg/kg) and 19 oral trials (400 to 1000 mg every 6 hours, 3 days/dose interval). Five of 22 patients showed efficacy at repeat PES study (neither VT nor VF), one showed partial efficacy, and four were not restudied because of clinical arrhythmia (three) and/or adverse effects (two). Overall, three patients (12%) were continued on the drug for an extended period of time. Adverse experience included hypotension in 50% and gastrointestinal effects (nausea, vomiting, or diarrhea) in 56% (oral trials only). Adverse reactions led to drug discontinuation in six and dosage reduction in eight patients. Thus, meobentine may prevent induction of VT or VF or reduce frequency of complex PVCs in selected patients refractory to other antiarrhythmic agents, but the response rate is relatively low. Symptomatic hypotension or gastrointestinal adverse effects are common and may limit utility of meobentine as a chronic oral antiarrhythmic agent.

Administration, Oral↗
PubMed1985

Arrhythmic syncope: what to do when ambulatory monitoring is non-diagnostic.

The two new methods for defining arrhythmic syncope described in this report represent important additions to the traditional syncope workup. Both techniques uncovered a substantial number of arrhythmic causes of syncope which had not been found by standard techniques. A major strength of each method is that symptoms can be directly related to the arrhythmia. The 68% incidence of diagnostic EPS abnormalities which we found was identical to the study of DiMarco but higher than reported by others (which have ranged from 12 to 48%) (18, 20, 21). More critical patient selection and more comprehensive study techniques most likely account for these differences. It is our opinion that a significant number of patients whose diagnosis was "syncope of undetermined etiology" in previous studies did indeed have an arrhythmic basis for their symptoms which was not identified. At this point the issue of "cost effectiveness" inevitably arises. Do all patients with syncope in whom a cause is not initially apparent (i.e., up to 50% of such patients) require either TTEM or EPS? The answer is obviously no, not for this whole population. However, the evident power of TTEM and EPS requires that the question should be raised. Furthermore, the results of the invasive EPS study strongly suggest that mortality and morbidity can be reduced. Table 11 shows the relative costs for all of the diagnostic tests for arrhythmic syncope. From this it can be seen that TTEM is quite inexpensive and therefore very cost-effective. It is an ideal adjunct to 24 hour ambulatory monitoring in selected patients. Although invasive EPS studies are costly, it is not difficult to incur equal costs by use of several days of prolonged monitoring, especially if done in the hospital. Thus, in identified patients with abnormal but "not diagnostic" ambulatory monitoring studies, patients with abrupt syncope, patients with frequent symptoms or patients with known underlying heart disease, further evaluation with TTEM or EPS should be strongly considered.

Arrhythmias, Cardiac↗
PubMed1984

The electrophysiologic effects of upright posture.

In order to determine the effects of upright posture on the electrophysiologic properties of the human heart, 12 patients underwent electrophysiologic studies in the supine and upright positions. Compared to supine, the upright position significantly reduced basic cycle length from 818 +/- 111 to 680 +/- 141 msec, sinoatrial conduction time from 186 +/- 94 to 135 +/- 56 msec, corrected sinoatrial recovery time from 206 +/- 104 to 108 +/- 55 msec, interatrial conduction time from 76 +/- 17 to 70 +/- 16 msec, and the AV nodal conduction time (AH interval) from 88 +/- 19 to 78 +/- 14 msec (all p less than 0.05). Right intra-atrial and His-Purkinje (HV interval) conduction times were not altered. When the subjects assumed the upright position, the effective refractory periods of the right atrium, atrioventricular node, and right ventricle decreased significantly at basic and paced cycle lengths. For the group as a whole, the upright posture did not significantly augment repetitive responses to atrial and ventricular extrastimuli.

Adolescent↗
PubMed1984

Clinical experience and grading of amiodarone keratopathy.

Eighteen patients receiving the cardiac drug amiodarone were followed prospectively for the development of amiodarone keratopathy. Seventeen of 18 patients (94%) developed characteristic epithelial keratopathy in at least one eye within three months of the initiation of therapy. The pattern of the epithelial deposits was noted to undergo progressive changes in configuration as a function of the duration of amiodarone therapy. These evolving changes are well defined and allow development of a grading system for amiodarone keratopathy. A grading system as well as a proposed mechanism for evolving pattern of the keratopathy are presented.

Aged↗
PubMed1984

Treatment of prehospital refractory ventricular fibrillation with bretylium tosylate.

Among 218 patients treated for prehospital arrest during an eight-month baseline period prior to addition of bretylium tosylate to the paramedic protocol in Columbus, 16 (7.3%) were seen with refractory ventricular fibrillation (RVF). These patients failed to respond to multiple countershocks, lidocaine, bicarbonate and epinephrine, and either were transported in arrest during cardiopulmonary resuscitation (CPR)(14) or were pronounced dead at the scene (2). A single patient was eventually resuscitated in and discharged from the hospital. During the subsequent 16 1/2-month experience with bretylium used only for prehospital RVF, 421 patients with prehospital arrest were seen, 35 of whom (8.3%) had RVF. All but five patients were defibrillated successfully, and 14 (40%) were converted to a rhythm sufficient to obviate CPR during transportation. Eleven patients (31%) survived to be admitted to the hospital, and eight of 35 (23% vs 1/16 or 6.2% above, P less than .05) were discharged and remained well three to 17 months later. Bretylium tosylate may provide life-saving therapy for refractory prehospital ventricular fibrillation so that survival from an almost uniformly fatal condition is improved. While patients with persistent arrest generally should be transported to the hospital, such patients should not be subjected to the difficulties of CPR in transit unless they are first given bretylium if RVF is present.

Bretylium Compounds↗
PubMed1984

The noninvasive localization of ventricular pacing sites by radionuclide phase imaging.

This study was designed to investigate the potential role of radionuclide angiographic phase imaging in defining ventricular pacing sites. Twenty patients were paced from multiple right ventricular and left ventricular sites. Ten patients had both normal wall motion and normal electrocardiograms (ECGs), while 10 patients had segmental wall motion abnormalities and/or bundle branch block. Both continuous pacing and premature ventricular stimuli were performed. Multiple (two to three) views of each pacing site were obtained by radionuclide angiography and the ventricular site was determined by subsequent phase imaging. Simultaneous 12-lead ECGs were also obtained. The phase-imaging technique accurately localized all 35 right ventricular and 21 of 25 (84%) left ventricular sites to a specific segment. Statistically, this localization ability was independent of baseline wall motion or conduction system disease. In addition, sites as close as 1.5 cm were identified. The 12-lead ECG distinguished left ventricular from right ventricular pacing sites in all patients. Segmental localization by ECG in the right ventricle was accurate in 24 of 35 (69%) and in the left ventricle in 17 of 25 (68%). Thus, radionuclide angiographic phase imaging provides excellent descriptive information regarding the focus of ventricular pacing ectopy and can define both sites of continuous pacing and intermittent premature ventricular stimulation. These findings provide a basis for further assessment of the role of phase imaging in the evaluation of patients with spontaneous ventricular ectopy.

Bundle-Branch Block↗
PubMed1984

Indocyanine green clearance following single and chronic cimetidine doses.

Twenty-five indocyanine green (ICG) clearance determinations were performed in four subjects in the presence of quinidine or propranolol before and after one week of treatment with cimetidine, 1200 mg/day, and following a single 600 mg cimetidine dose. There was no significant difference between the mean ICG clearance before cimetidine treatment and that after one week of therapy with cimetidine, while the mean ICG clearance was 25% lower following single cimetidine doses (p greater than 0.05). It is concluded that cimetidine has only a transient hepatic blood flow lowering effect.

Adult↗
PubMed1983

Comparison between electrophysiologic studies and ambulatory monitoring in patients with syncope.

The efficacy of 24-hour ambulatory monitoring and electrophysiologic studies was determined in sixty-five patients with a history of syncope or pre-syncope. Patients with an obvious cause of syncope and/or significant arrhythmias on the resting ECG were excluded. Monitoring and electrophysiologic studies were performed within one week. Arrhythmias and/or electrophysiologic abnormalities which were considered to be the cause of syncope or pre-syncope were detected with monitoring in 31 patients and with electrophysiologic studies in 42 patients. By combining both methods symptoms were explained in 51 patients (78%). In 22 of the patients arrhythmias were detected with both methods. Thus, in a group of patients with no obvious cause of syncope, abnormalities were readily detected with monitoring and electrophysiologic studies. These methods are complimentary and should be used (monitoring usually first) in the appropriate symptomatic patient.

Arrhythmias, Cardiac↗
PubMed1983

Repolarization variant vs acute pericarditis. A prospective electrocardiographic and echocardiographic evaluation.

Patients with ECG nonischemic ST segment elevation were prospectively studied to determine the accuracy of the initial ECG diagnoses. Evaluations were made of 131 consecutive patients by serial clinical, ECG, and echocardiography to establish a diagnosis. Eighty-six (66 percent) had an initial ECG interpretation of repolarization variant. Only three of the 86 (3 percent) subsequently met clinical criteria for acute pericarditis. Analysis of the mean frontal ST segment vector and PR segment depression revealed no significant differences between the 119 patients with final clinical diagnosis of repolarization variant and the 12 with clinical acute pericarditis. The diagnostic reliability of the initial ECG alone as a means of confirming acute pericarditis is low (9/45, 20 percent) but in the detection of repolarization variant is extremely high (83/86, 97 percent).

Acute Disease↗
PubMed1983

The "holiday heart": electrophysiologic studies of alcohol effects in alcoholics.

Although the "holiday heart syndrome," highlighted by rhythm disturbances after acute alcohol ingestion, is well known, the potential arrhythmogenic effects of alcohol have not been studied. Fourteen patients (two with congestive cardiomyopathy) with a history of rhythm disturbances and alcohol consumption were studied electrophysiologically. One patient had nonsustained ventricular tachycardia, one had nonsustained atrial fibrillation, one had paired ventricular responses, and the remainder had no response to the extrastimulus technique. After 90 mL of 80-proof whiskey, 10 of the 14 patients developed sustained or nonsustained atrial or ventricular tachyarrhythmias. Significant prolongation of His-ventricular conduction was seen after alcohol intake; this was noteworthy as one of the patients had previously shown Mobitz II atrioventricular block after acute alcohol consumption. Alcohol in modest doses has the potential to produce rhythm disturbances in patients with a history of chronic alcohol consumption and heart disease.

Adult↗
PubMed1983

Anthropometric characteristics, cardiac abnormalities and adrenergic activity in patients with primary disorders of sleep.

Sixty-one patients (pts) with sleep apnea (SA), 35 with narcolepsy (N) and 24 with idiopathic hypersomnolence (H) were studied in the Clinical Research Center. The height to body weight ratio was less than normal in SA pts (0.32 +/- 0.01 vs 0.45 +/- 0.01, p less than 0.01), but normal in N and H pts (0.45 +/- 0.02 and 0.45 +/- 0.01, respectively). Twenty-four hour urinary epinephrine (E) plus norepinephrine (NE) was greater than normal (p less than 0.01), but not different among SA, N and H pts. The incidence of mitral valve prolapse (MVP) was greater in N (49%) and H (58%) compared to SA (20%) (p less than 0.01). The ratio of the pre-ejection period to the left ventricular ejection time (PEP/LVET) was abnormal (greater than 0.42) in 36% of the pts with SA and only in one pt with N and H (p = 0.02). The % shortening of the echocardiographic internal diameter (% delta D) was abnormal (less than 28%) in 28% of pts with SA and normal in all pts with N and H (p = 0.02). The incidence of malignant ventricular dysrhythmias (24 hour Holter) was 26% in SA, 3% in N and 4% in H (p = 0.04). Thus, pts with impaired alertness have high adrenergic tone despite evidence for a role of catecholamines in wakefulness. Left ventricular dysfunction, malignant dysrhythmias and obesity are common findings in SA, while MVP is very common in N and H.

Adult↗
PubMed1983

Physiological adjustments to higher- or lower-intensity exercise in elders.

A program of physical activity for people over 60 yr of age was developed to determine whether exercising at lower intensities (LI) is a significant conditioning stimulus. In addition, differences in aerobic capacities (VO2max) elicited by training at LI, as opposed to training at higher intensities (HI), were evaluated. Thirty-two volunteers over 60 yr of age (mean = 67.8 yr) participated in a 9-wk exercise program. After initial testing of VO2max on a cycle ergometer, subjects were assigned randomly to the HI, LI, or control group. Endurance training of the two exercise groups on cycle ergometers was maintained at 30-45% (N = 14) or 60-75% (N = 14) of the range (HRR) between the subject's resting and maximum heart rate for 25 min during each exercise session. These training intensities represented 57 and 70% of the VO2max of the LI and HI groups, respectively. Participants averaged three exercise sessions per week. Non-exercising volunteers served as control subjects. A one-way ANOVA with repeated measures was utilized for comparisons of retest, groups, and interaction. As a result of the exercise program, significant changes (P less than 0.005) in absolute (VO2max, 1 X min-1) and relative (VO2max, ml X min-1 X kg-1) aerobic capacities were realized within each training group while initial and post-training VO2max were not significantly different between the two groups. Similar changes were documented by a reduction in heart rate at submaximal exercise intensities and during recovery. It was concluded that exercising at LI (30-45% HRR) is an adequate training stimulus in older individuals and produces changes in VO2max that are comparable to those elicited by HI (60-75% HRR) training.

Aged↗
PubMed1982

Liquid chromatographic determination of caffeine in biologic fluids.

A high-performance liquid chromatographic procedure was developed for the determination of caffeine in various biologic fluids and coffee. A reversed-phase column and UV detection at 254 nm were used to obtain a sensitivity of 0.1 microgram/ml caffeine in serum and saliva using a sample volume of 0.1 ml. Caffeine metabolites and commonly ingested xanthines do not interfere with the assay. The within-day coefficients of variation were 9.8 and 9.9% at plasma caffeine concentrations of 2 and 10 micrograms/ml, respectively. The day-to-day coefficients of variation were 6.8 and 6.6% at plasma caffeine concentrations of 2 and 10 micrograms/ml, respectively. Serum and saliva caffeine concentrations were determined following a single oral dose of coffee and an intravenous infusion of caffeine in one subject. Computer estimates of caffeine pharmacokinetic parameters in one subject are in excellent agreement with previously published values.

Caffeine↗
PubMed1980

Effect of procainamide on left ventricular performance in patients with primary myocardial disease.

The effect of procainamide (P) on left ventricular function as measured by the systolic time intervals (STI) was studied in 14 patients with primary myocardial disease. P, 7.5 mg/kg body weight, was given intravenously at a rate of 100 mg per minute. Administration of P produced a decrease in left ventricular performance as manifest by a significant prolongation of the pre-ejection period corrected for heart rate (PEPI) and an increase of the PEP to the left ventricular ejection time (LVET) ratio. The peak effect on PEPI and PEP/LVET occurred at 2 minutes after P administration (delta PEPI + 14 +/- 1.9 ms, p < 0.001, delta PEP/LVET + 0.052 +/- 0.007, p < 0.001) with values returning towards baseline by 60 min. In 6 of the patients P blood levels were measured simultaneously with the STI measurements. Changes in PEPI and PEP/LVET directly parallel changes of P blood levels. It is concluded that P given intravenously at the usual therapeutic doses decreases left ventricular performance in patients with primary myocardial disease. These changes in left ventricular performance directly parallel procainamide blood levels.

Adult↗