Assessment of laryngeal function by digital subtraction laryngography

The evaluation of vocal cord function can be problematic in the presence of oropharyngeal tumors, hypopharyngeal tumors, and supraglottic lesions and in noncompliant adult and pediatric patients. The use of computer image subtraction techniques coupled with digital fluoroscopy has inherent high-quality resolution that can provide an excellent image of vocal cord symmetry and movement. The use of air as the contrast medium provides the ability to measure the extent of vocal cord excursion as well as the extent of piriform sinus lesions. In addition, it is a noninvasive procedure that requires a minimal imaging exposure time, with the result that the patient undergoes minimal radiation exposure.

Cross-stimulation: the unexpected stimulation of the unpaced chamber

The ability to stimulate one chamber through a lead or output circuit to the opposite cardiac chamber is termed cross-stimulation. Three examples of this phenomenon are presented. The first involves the close proximity of the atrial lead to the ventricular myocardium with ventricular capture occurring at sufficiently high outputs; the second is due to the basic design of dual unipolar pacing systems which have output circuits that share a common anode; the third is a self-limited eccentricity of one device that occurs only during the first phase of magnet-induced asynchronous pacing. The mechanism and clinical significance of these observations are discussed.

Patient-initiated autonomous pacemaker tachycardia

Multiparameter programmable DDD pacemakers are said to have an uncountable number of possible parameter combinations. It is probable that a number of these combinations, particularly when triggered by one or more critically timed native events, will result in bizarre and unanticipated rhythms sustained entirely within the timing circuit of the pulse generator. We report the occurrence and analysis of one such rhythm termed a sustained autonomous pacemaker tachycardia. In this rhythm, both atrial and ventricular outputs occur at the maximum tracking rate of the pacemaker with an apparently shortened AV interval. Once initiated, the ability to sustain the tachycardia requires that the maximum tracking rate interval exceed the atrial escape interval. It will then continue until the pulse generator is programmed to parameters that alter this critical timing or a properly timed ventricular sensed event occurs. It is anticipated that this will be only one of many similar rhythms encountered in patients treated with complex devices from all the manufacturers. In the future, once such a rhythm is noted and its mechanism identified, modifications of the basic circuit design will allow these parameters to be used without danger to the patient and without having to limit the options of the device.

Clinical benefits of telemetered electrograms in assessment of DDD function

The advent of telemetry of the endocardial electrogram is a new capability. It must be convenient to use if it is to gain acceptance. Our experience is still growing but already it is confirming information that was either deduced or previously only available by active invasive procedures. The potential value of the technology has only been touched upon in this presentation. We are convinced that it will grow and that its value will be further established as more physicians have an opportunity to use it and gain additional experience.

Castleman's disease--the lymphoma impostor

The asymptomatic neck mass in the middle-aged adult is not an uncommon clinical dilemma for the otolaryngologist-head and neck surgeon. After a complete medical evaluation and panendoscopy with multiple "blind" biopsies, the patient usually comes to excisional biopsy, when the prior work-up has not added any positive information. Most commonly, in this age group, the mass represents metastatic cancer from a head and neck primary, a carcinoma from a distant site, or a lymphoma. We present a case of Castleman's disease, a benign lymphoepithelial disease that can easily be mistaken for lymphoma.

Use of verapamil to control an inappropriate chronic sinus tachycardia

Sinus tachycardia is an expected physiologic response to endogenous catecholamine stimulation, although it may limit the use of exogenous agents. We report a case in which persistent sinus tachycardia occurring in a patient with severe bronchospastic pulmonary disease was effectively treated with verapamil.

Intraoperative iodine 125 implants. Their use in large tumors in the neck attached to the carotid artery

Twenty-nine patients with large masses attached to the carotid artery underwent surgical resection, preservation of the artery, and intraoperative iodine 125 implantation via an absorbable suture. Eighteen were treated for recurrent neoplasms, having failed prior surgery and/or irradiation therapy. Eleven were treated primarily. With a minimum follow-up of one year, 76% were disease free in the implant volume and 62% were disease free in the entire neck. Distant metastases occurred in 45%. Mean survival was 15 months in the primary group (range, two to 50 months) and 12 months in the recurrent group (range, four to 26 months). This technique shows promise in providing local control without necessity for sacrifice of the carotid artery.

Pseudo-QT prolongation, artifactual electrocardiographic patterns produced by transduction of cardiovascular motion

Four cases are presented in which focal electrocardiographic artifacts mimicked QT segment prolongation with giant T and U waves. Displacement of the recording electrode by a subjacent cardiovascular impulse was the cause of this distortion. The artifacts could be reproduced at the bedside by intentional changes in patient posture and electrode stability. Phasic variation in electrode contact with the electrolyte gel and skin, or intermittent contact between the heart and chest wall, causes shifts in the electrical properties of the recording system which may distort the recorded waveforms during the repolarization phase of the electrocardiogram.

Adverse acute and chronic effects of electrical defibrillation and cardioversion on implanted unipolar cardiac pacing systems

Six cases are presented in which a transient or chronic rise in the stimulation threshold of a permanently implanted unipolar pacemaker resulted in the loss of effective pacing after therapeutic defibrillation or cardioversion. Although damage to the pulse generator may still occur, leading to a loss of function as demonstrated in a seventh patient, improvements in the internal protection circuits of the present generation of pacemakers makes this less likely while possibly predisposing to endocardial burns and increased fibrosis at the electrode-endocardial interface. The theoretical explanations for this phenomenon are discussed, along with recommendations for the prospective and retrospective management of the pacemaker patient who requires defibrillation or cardioversion.

Assessment of atrial capture in committed atrioventricular sequential (DVI) pacing systems

Two patients with committed dual unipolar AV sequential pacing systems are presented in whom atrial capture was unable to be demonstrated on the surface electrocardiogram. The bedside examination is proposed as a means of identifying the presence or absence of atrial capture with subsequent confirmation by M-mode echocardiographs and jugular venous pulse tracings. Mode, rate, and output programmability may aid in the evaluation of these pacing systems. Intentional reduction of the ventricular output to subthreshold levels in pacemakers capable of this degree of programmability will permit the rapid bedside confirmation of atrial capture without the need for expensive and time-consuming noninvasive tests.

Myopotential inhibition of unipolar lithium pacemakers

The effect of isometric upper extremity exercise on pacemaker function was evaluated in 27 patients who remained pacemaker-dependent during testing. Inhibition was demonstrated in eight (31 percent) of which five were symptomatic. Based on design of the sensing amplifier and return to an all-metal housing in the unipolar lithium pulse generators, myopotential inhibition is being recognized as one cause of symptomatic pacemaker inhibition that is more common than generally appreciated. A method of evaluation and management options for symptomatic patients are discussed. Routine testing of all patients should be performed at the time of a regular office evaluation. If one model pulse generator appears to be particularly prone to myopotential inhibition, this knowledge should be considered in the choice of future pacing systems.