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In this case, a patient who is incapable of participating in health-care decisions requires a pacemaker generator replacement. Because the pacemaker may no longer be necessary, the issues of surrogacy and surrogate decision-making are considered. Where there are no involved family members, each state has procedures for finding an appropriate ombudsman for the patient who can assist in healthcare choices., (©2012, The Author. Journal compilation ©2012 Wiley Periodicals, Inc.)

A case is presented examining the need to disclose the truth in cases where there is a question of device and personnel performance. This case examines the responsibilities of physicians to their patients and the community at large to disclose factual accounts of events, even in the case of medical error and potential liability., (©2011, The Author. Journal compilation ©2011 Wiley Periodicals, Inc.)

Signal averaging has been performed to evaluate late potentials following infarction and the administration of thrombolytic therapy. Most studies have recorded signal-averaged electrocardiograms (SAECGs) at least 12 hours after the onset of the infarction. In this study, SAECGs were recorded before thrombolytic therapy and serially over 7-10 days following infarction in 21 patients. The high frequency QRS duration was significantly shortened at 1 and 24 hours compared to presentation (96.8 +/- 11.3 ms and 93.4 +/- 8.0 ms vs 103.3 +/- 14.3 ms, respectively, P < 0.05) and there was an increase in the terminal voltage over time, significant at 1 hour and 3 days (57.3 +/- 29.1 microV and 58.6 +/- 44.7 microV vs 44.4 +/- 35.5 microV, respectively, P < 0.01). Five patients met criteria for ventricular late potentials on at least one SAECG. The prevalence of late potentials was higher in patients with Q wave infarctions, or with occluded infarct related arteries. These changes in myocardial activation may be related to ischemia and reperfusion, and may not correlate with the development of a fixed substrate for reentry.

Signal averaging can be used to assess changes in myocardial activation under a variety of physiological conditions including stress. This study prospectively evaluated patients who underwent rest and exercise recording of signal-averaged electrocardiograms. The 163 patients were divided into three groups based on thallium results: normal (group I), reperfusion (group II), and fixed defect (group III). Patients in group I showed shortening of the high frequency duration (P = 0.02) and the duration of the low amplitude signal (P = 0.024) after exercise. In these patients the terminal root mean square amplitude (RMSA) also increased significantly (P = 0.005). However, patients who were in either group II or group III showed little change in signal averaging measurements after exercise. The amplitude of the QRS in V5 and the RMSA of the total QRS also increased in all groups following exercise, with a lesser increase in the patients with reperfusion by thallium imaging (group II). There was no change among groups in the incidence of ventricular late potentials with exercise. This suggests that patients with ischemia or infarction may not have the same response to an increase in sympathetic tone with exercise as patients without abnormalities of cardiac perfusion. The clinical implications of these findings may include demonstration that an area of slow conduction exists in these latter two groups of patients.

Antitachycardia devices currently use sustained high rate, abrupt changes in cycle length, and probability density function to determine the onset of ventricular tachycardia. Hemodynamic changes occur with the onset of tachycardia and may provide a method of discriminating supraventricular from ventricular tachycardia. In this study, patients had atrial and ventricular pressures measured during rapid atrial and ventricular pacing. Right atrial pressure increased significantly with ventricular pacing but not with atrial pacing. Right ventricular pressures did not significantly differ with atrial or ventricular pacing. The change in atrial pressure compared to baseline was greater, with ventricular pacing compared to atrial pacing. Right ventricular pressure increased compared to baseline with atrial or ventricular pacing, but there was no significant difference between pacing modalities. Measurement of right atrial pressure might prove useful in discriminating supraventricular from ventricular tachycardia.