Electrocardiographic "pacemaker pseudo-spikes" and radio frequency interference

Improved pacemaker pulse detection: clinical evaluation of a new high-bandwidth electrocardiographic system

BACKGROUND

This study compares the pacemaker pulse detection performance of the new high-bandwidth (hi-fi) electrocardiographic (ECG) acquisition system to a conventional system in a prospective clinical evaluation.

METHODS

Electrocardiograms from 88 subjects with implanted pacemakers were recorded using different pacemaker programmed outputs and with different noise levels. Each ECG was recorded simultaneously from both systems. A cardiologist independently confirmed the clinically relevant ECGs. The pacemaker pulse detection sensitivity and positive predictive value (PPV) of each system were computed. The efficacy of each system was evaluated using a z test.

RESULTS

For the independently confirmed reports, the hi-fi system was superior, with higher sensitivity (99.2% vs 83.2%, P < .0001) and higher PPV (100% vs 99.9%, P = .33), for the detection of pacemaker pulses.

CONCLUSION

In a large group of subjects with implanted pacemakers and even in noisy conditions, the new hi-fi system was shown to improve pacemaker pulse detection sensitivity and PPV.

[Field 4. Environmental safety practice in the intensive care unit. French-speaking Society of Intensive Care. French Society of Anesthesia and Resuscitation]

Medical devices are known to carry risks from design to scrap. Accident reports in ICU show that medical device account for only 20% of accidents. Formation of users and providing a postmarketing incident reporting are thus essential in health institutions. Clinical and engineering departments should cooperate to produce and secure procedures which should be applied during the lifetime of each clinical device. Several points should be especially fulfilled: close cooperation between clinical departments and biomedical engineering departments with available technicians, computer-based inventory of all devices, evaluation of specifications required before purchasing a new device, education of users on utilisation and maintenance, technical follow-up of devices and keeping maintenance and repair logs, ability to provide users with replacement devices, provision of check-lists before use, forging criteria to decide when device should be discarded. These principles are simple and should be considered as mandatory in order to improve medical device related security.

The postmodern heart: war veterans' experiences of invasive cardiac technology

BACKGROUND

The consequences of war and medical discourse have historical connections to pacemaker technology. Understanding these consequences is important because war veterans, medicine and cardiac technology have a shared history that continues into the present. The incidence of Australian war veterans needing cardiac pacemakers has increased many-fold in recent years, due to advancing age. This need was recognized by the Australian Department of Veteran Affairs and a cardiac programme was established in the veteran hospital that was the setting for this study.

AIM

This paper reports on a study aimed at capturing the interest and sensitizing the practice of nurses involved in the care of war veterans and other health care consumers who have been diagnosed as requiring a cardiac pacemaker. The study sought to answer the question, 'How does the war veteran experience his body in relation to invasive cardiac technology?'.

METHOD

The research was guided by the principles of interpretive interactionism, and used unstructured interviews with eight male war veterans. The data were collected in 2000.

FINDINGS

Thematic and content analysis revealed five themes: emotional knowing; the medical encounter; belief in the myth of miracle; technological constraint; and the altered heart. The findings indicated that the human dimension was characterized by experiences of ambivalence, inner conflict, powerlessness and suffering.

CONCLUSION

Nursing is at the interface of science and patient care, and this study contributes to nursing knowledge by focusing on a previously unresearched topic, namely embodied interactions between war veterans and invasive cardiac pacemakers. Within a highly technical area such as cardiology, nurses can still work around the technology and keep patients as their primary focus, thus promoting quality care. A humanistic rather than a technological focus locates nurses between patients and cardiac technology. In this in-between location, nurses are not an extension of cardiac technology but a valuable source of information, education, and counselling.

Electrosurgery in Otolaryngology???Head and Neck Surgery: Principles, Advances, and Complications

OBJECTIVES/HYPOTHESIS

Electrosurgical instruments are routinely used in many applications by otolaryngologist-head and neck surgeons; and a complete description of their historical development, physics of operation, histological effects, and technological advancements is necessary for our specialty to take full advantage of this instrumentation. Because of the electrical current, heat production, and common use associated with these instruments, compounded by the complex environments in which they are used, potential complications must be considered and are likely underreported in the literature. This thesis describes the important aspects of electrosurgery along with a study of complications so otolaryngologists can use these instruments to their fullest potential while limiting complications.

STUDY DESIGN

National survey of electrosurgical complications.

METHODS

A survey addressing potential complications of electrosurgery was developed based on a review of the electrosurgical and complications literature. The electrosurgical complications were organized in the following categories: 1) unanticipated direct burns as a result of the active electrode contacting some tissue unintentionally; 2) unintentional burns as a result of capacitive coupling where radiofrequency (RF) current passes through a metallic instrument (such as forceps) and burns tissue in contact with that metallic instrument; 3) fires occurring as a result of electrosurgical instruments; 4) electromagnetic interference with a pacemaker, defibrillator, or cardiac monitoring device; and 5) other complications not included in the previous categories. The survey was mailed to the 620 members of the Society of University of Otolaryngologists.

RESULTS

Of the 620 surveys mailed, 35 were returned by the post office for lack of a forwarding address and 296 were returned completed for a response rate of 49.7%. The respondents performed a total of 99,664 cases in the previous year. During that year, 324 complications related to electrosurgical instruments were reported. These included 219 unanticipated direct burns, 48 burns as a result current flow through a metallic retractor or instrument (capacitative coupling), 13 grounding pad burns, 11 fires, 32 cases of electromagnetic interference, and 1 hair loss at an incision site as a result of a cutting electrosurgical instrument. Information regarding the circumstances surrounding these complications and outcome are presented.

CONCLUSIONS

Electrosurgery has proliferated since its original application by William T. Bovie and Harvey Cushing in the 1920s. Because surgeons use this technology frequently, a thorough understanding of these instruments and their potential complications is critical to their safe and successful use. Electrosurgical units operate on basic fundamental principles of physics and involve the passage of electrical current through tissue to create the desired tissue effect. With knowledge of the history, physics, techniques, histological effects, and safety issues of electrosurgery, the field will continue to proliferate and electrosurgery will continue to assist surgeons in alleviating human suffering.

Abnormal electrical stimulus of an intra-aortic balloon pump with concurrent support with continuous veno-venous hemodialysis

Malfunction of electronic medical support apparatus utilized in the ICU usually causes system failure. We report several occurrences of a potentially dangerous interaction between a continuous veno-venous hemodialysis (CVVHD) system and an intra-aortic balloon pump (IABP) counterpulsation device in four patients requiring both systems. The patients had acute renal failure in the face of multi-organ failure and were dependent upon the balloon pump for pressure support. Electrical interference created by the roller pump action of the CVVHD system was identified by the balloon pump as cardiac in origin, and it responded by inflation and deflation. As the blood pump rate was reduced, the interference reduced to the point of complete cessation when the blood pump was shut down. Whereas one patient transiently had a significant drop of mean arterial pressure (from 70 +/- 4 to 40 +/- 2 mm Hg) the other observed occurrences had no clinically significant sequelae. Electrocardiogram (ECG) tracings identified the abnormal stimulus and systematic review identified as potential sources for the creation of this interference static electricity buildup, piezoelectric properties of the polyvinyl chloride tubing, and, possibly but less likely, radiofrequency interference. A newer generation ECG cable and advanced cardiac rhythm recognition software (CardioSync) have been introduced with the Datascope System 98, and the ECG interference, although still occasionally present, does not cause erratic inflation and deflation of the intra-aortic balloon pump. Interference between different electrical support systems may occur, and we suggest that the systems be tested for compatibility before combined use and that older equipment be more rigorously tested for potential clinically significant interference.