Profiles of automated peritoneal dialysis prescriptions in the US 1997-2003.

Automated peritoneal dialysis (PD) is the dominant mode of delivery of PD in the US. Information about actual prescribing patterns has been limited. The present study examines cycler prescription use in large cohorts during the years 1997, 2000, and 2003.

Electrocardiographic changes during acute treatment of hypertensive emergencies with sodium nitroprusside or fenoldopam.

Background: Electrocardiograms are routinely obtained before and during the acute treatment of hypertensive emergencies, usually to rule out "ischemic changes." Despite a few anecdotal reports of electrocardiographic changes, little is known about the incidence and significance of such changes, or their relationship to the treatment used.

Methods: We prospectively analyzed 12-lead electrocardiograms from 21 patients admitted for hypertensive emergencies (average blood pressure, 222 +/- 4/140 +/- 3 mm Hg).

Torsade de pointes complicating acute myocardial infarction: the importance of autonomic dysfunction as assessed by heart rate variability.

Torsade de pointes is a polymorphic ventricular tachycardia associated with QT-interval prolongation rarely reported to occur in the setting of an acute myocardial infarction. Autonomic dysfunction has been implicated as a major stimulus for the development of this dysrhythmia. We describe the case of an 80-year-old woman who presented with an acute myocardial infarction and progressive QT-interval lengthening.

Informed consent in emergency research. Prehospital thrombolytic therapy for acute myocardial infarction.

Can the conscious patient in the midst of a medical emergency provide adequate informed consent for a clinical research protocol? Adequate consent is crucial to the ethical conduct of clinical trials, including those performed in emergency settings. We examine the problem of emergency informed consent. As an illustrative case, we discuss a pilot trial of prehospital thrombolytic therapy for myocardial infarction.

Evaluation of patients for the need of thrombolytic therapy in the prehospital setting.

Maximum benefit from thrombolytic therapy in acute myocardial infarction is obtained with early therapy. The earliest possible time to treat is during the initial evaluation of the patient in the home or ambulance, which requires accurate diagnosis of acute myocardial infarction in the prehospital setting. In our study, paramedics evaluated patients who had chest pain with a 12-lead ECG transmitted by cellular telephone and a checklist for inclusion and exclusion criteria for thrombolytic therapy.

Cellular telephone transmission of 12-lead electrocardiograms from ambulance to hospital.

Currently, only single-lead, serial telemetry rhythm strips can be transmitted from ambulances. Triage of patients with chest pain and administration of thrombolytic therapy in ambulances is limited by the lack of specific electrocardiographic (ECG) diagnosis. A new technique is described using cellular telephone transmission of simultaneous 12-lead ECGs from ambulance to hospital to overcome this limitation.

Optimal ECG monitoring during percutaneous transluminal coronary angioplasty of the left anterior descending artery.

During percutaneous transluminal coronary angioplasty (PTCA) frontal ECG leads are routinely monitored. The detection of ST segment deviation during the procedure is important for decisions regarding guiding catheter seating and the timing of balloon inflation and deflation. ST segment deviation appears on intracoronary electrograms in the absence of changes on the surface ECG in many patients, while the reverse is true in some individuals.

R wave of the surface and intracoronary electrogram during acute coronary artery occlusion.

Increases in electrocardiographic R-wave amplitude in humans have been described with positive and negative dynamic exercise test findings, episodes of variant angina and myocardial ischemia and infarction. The role of factors other than acute reversible ischemia in the genesis of these R-wave size alterations is unclear. To evaluate the contribution of acute ischemia to changes in R-wave size in the absence of other confounding variables, electrocardiograms were recorded before and during coronary angioplasty balloon inflation.

Change in ventricular cavity size: differential effects on QRS and T wave amplitude.

Although many factors have been reported to change the R wave amplitude of the electrocardiogram (ECG), few observations have been made of the associated changes in T wave amplitude. We hypothesized that changes in R and T wave amplitude should parallel each other. To test this hypothesis, R and T wave amplitudes were measured in 15 normal subjects during increased and decreased left ventricular dimensions induced by infusion of methoxamine and by Valsalva maneuver, respectively, as well as during changes in the proximity of the left ventricle to the chest wall (i.

Relation of electrocardiographic R-wave amplitude to changes in left ventricular chamber size and position in normal subjects.

Although exercise-induced changes in electrocardiographic R-wave amplitude have been ascribed to changes in left ventricular (LV) size, QRS axis, heart rate and ischemia, the physiologic mechanism remains unclear. To clarify the relation between R-wave amplitude and changes in LV size and position, simultaneous 9-lead electrocardiograms and targeted M-mode echocardiograms were recorded from 15 normal subjects. Recordings were made at rest, during Valsalva maneuver and during methoxamine infusion.

Supernormality: recent developments.

The major advance in our understanding of supernormality is the following hypothesis. Focal accumulations of extruded potassium ion in unstirred-clefts (invaginated extensions of the extracellular space in Purkinje fibers) cause threshold to fall by virtue of the early effects of hyperkalemia: lowering of threshold and acceleration of conduction. These effects rapidly dissipate in diastole as ionic equilibration takes place; threshold rises and assumes its late diastolic value.

Heterotopic bone formation: An apparently benign complication of median sternotomy.

Two cases are reported that involve heterotopic bone formation in midline sternotomy scars. The authors relate similar complications associated with abdominal incisions and discuss possible causes.

Electrophysiological changes in the canine atrium and ventricle during progressive hyperkalaemia: electrocardiographical correlates and the in vivo validation of in vitro predictions.

The electrophysiological response to hyperkalaemia was reinvestigated in the whole dog for several reasons including: the paucity of comparative electrophysiological and electrocardiographical studies in which atrial and ventricular tissues were simultaneously investigated; the contrast between the clarity of findings in previous in vitro studies as compared with the rather conflicting results in earlier in vivo investigations; and the difficulty in validating the extrapolation from in vitro results and theory to the in vivo situation because of deficiences in the literature. Biphasic alterations in atrial and ventricular conduction times as well as excitability in response to progressively increasing hyperkalaemia were documented. The alterations in conduction times were reflected quite accurately by relevant electrocardiographical changes.

The junctional premature beat: an instructional exercise in modes of concealment.

?The relative brevity of the main His bundle refractory period compared with that of the A-V node above, and the trifascicular system below, makes it likely that premature beats originating in the His bundle will encounter physiologic delay, or block in both antegrade and retrograde modes. Two clinical cases of junctional premature beats are presented, which demonstrate many facets of concealment (antegrade, retrograde and bidirectional). Hitherto unreported is a ventricular echo which was induced by a junctional premature beat, the antegrade concealment of which was due to functional trifascicular block.