The Costs of Recurrent Syncope of Unknown Origin in Elderly Patients

Although syncope has been shown to reduce quality-of-life, its impact on resource costs has not been documented. The objective of this study was to quantify the annual medical costs of caring for elderly patients with syncope, especially recurrent syncope of unknown origin. Administrative data from the Health Care Financing Administration were obtained on 7,959 Medicare patients who had at least one inpatient admission with a diagnosis of syncope in 1993. The costs of any inpatient admissions, outpatient procedures, or physician visits with an ICD-CM-9 diagnosis for syncope were summed for a 365-day period from the date of the initial hospitalization for syncope. Patients who had at least two hospitalizations with admission and discharge diagnosis of syncope were deemed to have recurrent syncope of uncertain origin. To better estimate syncope costs for those whose syncope costs could have been attributed to other diagnoses, a regression analysis was performed including variables representing the most frequent secondary diagnoses. The average annual costs of those who were admitted with syncope but who were discharged with another diagnosis was $4,942 in 1993. The average annual cost of patients with recurrent syncope deemed to be of unknown origin was $5,165. For those patients with secondary diagnoses of atherosclerosis, urinary tract infections, or hypokalemia, the annual costs of syncope averaged $6,820, $7,013, or $7,949, respectively.     

A New Defibrillator Discrimination Algorithm Utilizing Electrogram Morphology Analysis

Inappropriate therapies delivered by implantable cardioverter defibrillators (ICDs) for supraventricular arrhythmias remain a common problem, particularly in the event of rapidly conducted atrial fibrillation or marked sinus tachycardia. The ability to differentiate between ventricular tachycardia and supraventricular arrhythmias is the major goal of discrimination algorithms. Therefore, we developed a new algorithm, SimDis, utilizing morphological features of the shocking electrograms. This algorithm was developed from electrogram data obtained from 36 patients undergoing ICD implantation. An independent test set was evaluated in 25 patients. Recordings were made in sinus rhythm, sinus tachycardia, and following the induction of ventricular tachycardia and atrial fibrillation. The arrhythmia complex is defined as wide if the duration is at least 30% greater than the template in sinus rhythm. For narrow complexes, four maximum and minimum values were measured to form a 4-element feature vector, which was compared with a representative feature vector during normal sinus rhythm. For each rhythm, any wide complex was classified as ventricular tachycardia. For narrow complexes, the second step of the algorithm compared the electrogram with the template, computing similarity and dissimilarity values. These values were then mapped to determine if they fell within a previously established discrimination boundary. On the independent test set, the SimDis algorithm correctly classified 100% of ventricular tachycardias (27/27), 98% of sinus tachycardias (54/55), and 100% of episodes of atrial fibrillation (37/37). We conclude that the SimDis algorithm yields high sensitivity (100%) and specificity (99%) for arrhythmia discrimination, using the computational capabilities of an ICD system.     

Laboratory studies of visible-light cured fissure sealants: setting times and depth of polymerization

Measurements were made, using an acoustic transmission method, of the setting times of three visible-light curing sealants (two filled, one unfilled). Five commercially available visible-light polymerizing sources were tested with each material. Only three of the light sources gave setting times not significantly different from the manufacturers' recommended times for all three materials tested. The variation in microhardness with depth of sealant was measured to study the depth of polymerization of the sealants, all of which were adequate. The filled sealants had microhardness values greater than the unfilled sealant, at all depths studied.     

Patient Requests in Family Practice: A Focal Point for Clinical Negotiations

A growing body of literature has stressed the importance ofeliciting the patient's views on the management of health andillness. In particular, it is recognized that patients frequentlyenter into clinical encounters with specific requests for services,that is ideas about how they hope to be helped. The presentinvestigation examined the following two questions: (1) whatkinds of requests do adult patients coming to a family practicecentre have prior to seeing the doctor; and (2) will factoranalysis of a 25-item patient request questionnaire provideevidence of the basic or most common dimensions of patient requestsin this population? Two newly-developed instruments were administeredto a sample of 144 adult patients before their visit to thedoctor. Factor analysis yielded five major request factors—‘medicalinformation’, ‘psycho-social assistance’,‘therapeutic listening’, ‘general health advice’,and ‘biomedical treatment’ —partially replicatingthe findings of an earlier pilot study. The clinical implicationsof eliciting patient requests in the light of current behaviouraland social science research into the doctor-patient relationshipare discussed. Future research directions are also outlined.     

Impedance of Pacemaker Leads: Correlation of Different Methods

This study compares three different pacing system analyzers, which measure impedance at different points during an impulse, with measurements telemetered from implanted pacemakers from four different manufacturers. Measurements were obtained at the time of implantation in a group of 103 patients. The measurements obtained by these different methods differ significantly from each other; the later during the impulse the impedance is measured, the higher in general its value. Interpretation of impedance values should take into account the technique of measurement.     

Radiofrequency Catheter Ablation of the Left and Right Ventricles: Anatomic and Electrophysiologic Observations

Certain untoward effects associated with the use of direct-current electrical catheter ablation of the ventricular endomyocardium have been noted. We assessed the efficacy and safety of closed-chest catheter ablation of the left and right ventricles using radiofrequency (RF) energy (750 kHz) in six dogs. Mean RF energies between 93 and 123 joules (J) were randomly delivered to three left ventricular (LV) sites via two distal adjacent electrodes (bipolar configuration) using 6-7F USCI tripolar or quadripolar catheters with an interelectrode distance of 5-10 mm. Another 90-143 J were given to two right ventricular (RV) sites in single or multiple divided applications between a distal electrode and an external patch electrode (unipolar configuration). Ventricular arrhythmias were not observed during application of RF energy. Programmed ventricular stimulation before and after the procedure did not induce ventricular tachycardia (VT) or fibrillation except in one dog who had inducible VT prior to ablation. There were no significant changes in LV and RV effective refractory periods after the procedures. Occasional premature ventricular beats and rare episodes of non-sustained VT (3-12 beats) were observed in ambulatory electrocardiographic recordings (13-24 hrs) done immediately after ablation. Dogs were sacrificed after 4-5 days. Pathology showed well-demarcated round or ovoid lesions of varying sizes. Mural thrombus was found in one dog. Microscopic findings consisted of circumscribed areas of coagulation necrosis with a peripheral zone of cellular infiltration. Transmural necrosis without perforation was occasionally seen in the thin RV wall when higher energies were delivered. In conclusion, discrete areas of desiccation injury in the ventricles can be achieved by transcatheter bipolar or unipolar ablation using RF energy. The complications associated with this method appear to be minimal. Further experiments are needed to evaluate its potential for catheter ablation of ventricular tachycardia.     

Combined Cardiomyopathy and Skeletal Myopathy: A Variant with Atrial Fibrillation and Ventricular Tachycardia

VLAY, S., et al. : Combined Cardiomyopathy and Skeletal Myopathy: A Variant with Atrial Fibrillation and Ventricular Tachycardia. This article describes a family characterized by combined cardiomyopathy and nonspecific skeletal myopathy who present in the third to fifth decades with cardiac manifestations but earlier have evidence of subtle skeletal muscle dysfunction. They differ from previously defined syndromes and potentially represent a different genetic expression or mutation. Cardiomyopathy presents with atrial arrhythmias including AF and atrial flutter. Life-threatening ventricular tachyarrhythmias occur next with onset of ventricular dysfunction. Electrophysiological study revealed sustained monomorphic VT. Affected family members benefitted from an ICD and progression to congestive heart failure (CHF) occurred late. Skeletal myopathy continues with marked progressive muscle weakness and inability to ambulate without assistance. Genetic analysis is currently ongoing. Neurological evaluation in all three family members revealed nonspecific myopathy affecting the psoas and iliopsoas muscles. Atrophy and wasting of the facial and temporalis muscles were common. Skeletal muscle biopsy revealed myofiber atrophy consistent with myopathy.     

Undersensing of P Waves in the Presence of an Adequate P Wave Due to Automatic Postventricular Atrial Refractory Period Extension

Two cases in which a DDD pacemaker failed to track P waves due to repetitive activation of the automatic postventricular atrial refractory period (PVARP) extension are reported. In one case, the cycle was initiated by a premature ventricular contraction (PVC); in the other, by touching the unipolar pacemaker with a needle while suturing. We demonstrated that chest wall stimulation can be used to induce cycles of repetitive automatic PVARP extension and failure to track P waves. We demonstrated in vitro that touching a unipolar pacemaker with a needle can generate a signal sufficient to mimic a QRS complex, and initiate a cycle of repetitive P wave undersensing.     

Cardiac Activation During External Cardiac Pacing

To determine which cardiac chambers are stimulated during external cardiac pacing we performed external pacing in eight normal volunteers while recording the esophageol electrogram. All subjects demonstrated evidence of pacing, which was ventricular in each case. The atrium was frequently activated retrogradely during pacing. We conclude that external cardiac pacing selectively stimulates the ventricle and is thus not of value for noninvasive atrial pacing studies.     

Apparent Undersensing Due to Oversensing of Low Amplitude Pulses in a Thoracic Impedance-Sensing, Rate-Responsive Pacemaker

A case in which apparent undersensing was caused by detection of low amplitude impedance-measuring pulses emitted by a thoracic impedance-sensing rate-modulated pacemaker is described. The detection of these high frequency pulses was interpreted as "noise" by the pacemaker and led to asynchronous pacing in the interference reversion mode. Increasing the sensitivity failed to correct the problem. Decreasing the sensitivity eliminated oversensing of the low amplitude pulses and the apparent undersensing. Recognition of this phenomenon is important to prevent a misdiagnosis of undersensing.