Amiodarone-induced lens opacities.

Amiodarone hydrochloride is a benzofurane derivative used for cardiac abnormalities. Its use is commonly associated with an asymptomatic keratopathy. Although lipid deposits have been observed with the electron microscope in the lens epithelium of one patient with a history of amiodarone therapy, lens opacities have not been reported in patients using this drug. Visually inconsequential, anterior subcapsular lens opacities in seven of 14 patients using moderate to high doses of amiodarone who were examined at the Veterans Administration Hospital in San Francisco are reviewed.

A non-contact vital signs monitor.

The expansion and contraction of the lungs and heart result in movement of the chest wall that can be detected and monitored to determine respiration and heart rate. A prototype non-contact Vital Signs Monitor (VSM) has been developed which uses very low power, high frequency Doppler radar to detect these motions. Digital signal processing (DSP) techniques, imbedded in the VSM, are used to extract heart and respiration rate information from the resultant waveform. A 10-GHz prototype VSM was developed for the Air Force in the mid-1980s using analog technology. The objective was to assess a fallen soldier's clinical condition at distances up to 100 meters before committing resources to assist that individual. An updated and improved version of the original VSM was developed in 1997. This device was designed to operate at shorter distances, use a higher frequency carrier, and provide more specific heart and respiration rate information using digital signal processing techniques. The VSM radar system is a straightforward homodyne receiver. It operates using frequency modulated continuous wave (FM-CW) transmission, which allows for very low power levels. The safe human power density exposure level at its operating frequency of 35 GHz is 10 mW/cm2. A simple approximation using uniform distribution and an antenna aperture of 2 cm by 3 cm gives a power density at the antenna face of 0.017 mW/cm2, nearly a factor of 1000 below the safe level. When the VSM's antenna is trained on the chest wall of a subject, the VSM is capable of measuring and distinguishing minute movements resulting from the mechanical activity of the heart and lungs. As the subject's chest wall moves, the exact phase of the return signal changes. To avoid the possibility of phase-related dead spots, two signals differing in phase by 90 degrees are used to demodulate the signal to baseband (DC). The two resulting "time-varying DC" signals represent the sine and cosine of a phase angle corresponding to the changing position of the target, in this case the motion of the chest wall. The current VSM operates at a frequency of 35 GHz with a corresponding wavelength of only 8.6 mm. This provides a response sensitive enough to detect the small motions caused by cardiac function. The Vital Signs Monitor has several possible application areas. The fact that it is noncontacting would make it especially attractive for monitoring patients in burn units, NICUs, or trauma centers, where attaching electrodes is either inconvenient or not feasible. Results to date indicate a strong correlation between the cardiac component of the motion signal and an electrocardiogram (ECG). With careful signal processing and analysis, it may be possible to extract clinically useful information about cardiac condition, function, or performance from the surface-motion waveform. This could provide a safe, inexpensive, and painless addition to the diagnostic and monitoring tools currently available to cardiologists. Although there are technical obstacles to overcome in filtering gross motions of the subject, the VSM offers significant advances over conventional methods of measuring heart and respiration rate.

Arrhythmias in single-chamber pacemakers.

Arrhythmias mediated by normal pacemaker functions and induced by pacemaker malfunctions are listed in Tables 1 and 2. Frequently, a careful review of the performance specifications in the technical or physician manual of the pacemaker model in question will provide a better understanding of pacemaker-related arrhythmias. By reprogramming selected parameters, the physician may eliminate the arrhythmia and avoid replacement of a normally functioning pulse generator.

A patient-centric approach to telemedicine database development.

Computer and telecommunications technologies have unleashed a wide range of powerful tools for gathering, storing, and distributing patient information. Computerized records enable healthcare providers to rapidly access patient data and to closely monitor patients from a distance. These significant advantages can be further extended by using the technology to more fully involve patients in their own healthcare management. A patient-centric approach to telemedicine means that the patient takes on additional responsibility and control, and the benefits from increased patient involvement will translate into improved compliance, reduced litigation, lower costs, and better outcomes. Furthermore, there are often important ethical questions that are best decided by the informed patient. Patients have a right to know what information is being gathered and who will be authorized to access that information. Current health information systems do not adequately address these issues, and telemedicine applications--particularly home based telemedicine--is forcing everyone to take a closer look at patients' roles in their own healthcare. In this presentation, a patient-centric home telemedicine database is described, the limitations are discussed, and future directions are proposed.

Noise mode response at peak exercise in a DDD pacemaker.

The noise sampling period has been recognized as a cause of apparent sensing malfunction in demand pacemakers. Physiologic signals as well as external electromagnetic interference can cause certain demand pacemakers to remain refractory and escape asynchronously at a specified rate. In this case, noise mode reversion pacing at the programmed lower rate limit of a Cordis 415A DDD pacemaker was observed during exercise when P-waves fell within the noise sampling period.

Permanent pacemaker implantation in the cardiac catheterization laboratory: the subclavian vein approach.

During a 36-month period, 171 permanent pacemaker procedures were performed in the cardiac catheterization laboratory by invasive cardiologists. This included 111 initial pacemaker system implants, via the percutaneous subclavian vein approach, 45 pulse generator changes, and 15 miscellaneous procedures. In no case did subclavian vein puncture result in pneumothorax, hemothorax, or brachial plexus injury. In patients undergoing initial lead placement, the dislodgment rate was 0.8% over a 16-month follow-up period. The reoperation rate for causes other than premature battery depletion was 5.4% during the first 12 months. The implantation of permanent pacemakers can be safely and effectively accomplished by experienced invasive cardiologists in the cardiac catheterization laboratory. In our series not only was continuity of patient care improved, but also medical costs were reduced.