Pacing and clinical electrophysiology : PACE
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Pacing Clin Electrophysiol · Mar 1997
Methods other than tilt testing for diagnosing neurocardiogenic (neurally mediated) syncope.
The recording of spontaneous episodes of bradycardiac neurocardiogenic syncope (NCS) has shown that: a prolonged ventricular asystole seems necessary to cause syncope; asystole is preceded by other bradyarrhythmias in the vast majority of cases; some warning symptoms precede the loss of consciousness in most cases; conventional dual-chamber pacing is efficacious both in patients with a positive response to carotid sinus massage (CSM) and eyeball compression test (EBC) and in those with a positive response to tilt-testing (TT). CSM, EBC, and TT are established tools for diagnosing NCS, when the recording of spontaneous syncope is lacking. When combined together, they are probably able to correctly identify most patients affected by NCS. ⋯ Our knowledge suggests that the correlation may be unsatisfactory, owing to the following: the variability of the mechanism of spontaneous syncope from patient to patient and also, in the same patient, from one episode to another; the discordance of the type of response when 2 or 3 tests are positive in the same patient, the response being more frequently asystolic with CSM and EBC and more frequently vasodepressor with TT: the different timing between hypotension induced by CSM (in which it follows the bradycardia) and that induced by TT (in which it usually precedes the bradycardia) and the uncertainty about the timing of hypotension during the spontaneous syncope; the good reproducibility of the spontaneous event by CSM and EBC, but not by TT, when cardiac asystole is the manifestation of NCS; and the fairly high rate of false-positive results of cardiovascular reflexivity maneuvers. Hypotension is the main reason for the failure of pacemaker therapy in all the forms of neurocardiogenic syncope (NCS), whether diagnosed by CSM, EBC, or TT. Thus, the need arises to correctly identify the magnitude of the hypotensive reflexes of spontaneous events.
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Pacing Clin Electrophysiol · Mar 1997
Cardiovascular syncope is the most common cause of drop attacks in the elderly.
Drop attacks are defined as a sudden loss of postural tone without loss of consciousness. The mechanism is often unknown. This report examines findings in consecutive elderly patients with drop attacks referred to a dedicated "syncope and falls" center. ⋯ A diagnosis was established in 25 (71%); cardioinhibitory cartoid sinus syndrome (CSS) or mixed CSS in 15, vasodepressor CSS in 3, orthostatic hypotension in 5, vasovagal syncope in 1, and gait imbalance in 1. In 21%, more than one pathological diagnosis was present. In conclusion, absence of a history of syncope is unreliable in elderly patients, and these individuals should be routinely investigated for hemodynamic changes during carotid massage and standing.
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Pacing Clin Electrophysiol · Feb 1997
ReviewThe cardiac vulnerable period and reentrant arrhythmias: targets of anti- and proarrhythmic processes.
Because sudden cardiac death is usually preceded by a reentrant arrhythmia, the precipitating arrhythmia must be multicellular in origin. Therefore clinicians seeking to reduce the incidence of reentrant arrhythmias in their patients with antiarrhythmic drugs that alter propagation may reasonably question the applicability of drug classification schemes (e.g. Sicilian Gambit) that are based on measurements in single cells. ⋯ The cycle-to-cycle variation in QRS morphology was caused by the spatial variability of the reentry path. The variability of reentry paths (and hence the degree of polymorphic variation in QRS complexes) was amplified by Class III agents. The results presented here show that multicellular proarrhythmic effects are derived from the same mechanisms that exhibit antiarrhythmic properties in single cells.
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Pacing Clin Electrophysiol · Feb 1997
ReviewHypertrophic cardiomyopathy: evaluation and treatment of patients at high risk for sudden death.
Hypertrophic cardiomyopathy (HCM) is a heritable disease characterized by LV hypertrophy with markedly variable clinical, morphological, and genetic manifestations. It is the most common cause of sudden death in otherwise healthy young individuals. HCM patients often have disabling symptoms and are prone to arrhythmias. ⋯ Over the past decade, progress has been made in identifying patients who are at high risk for sudden death, in elucidating potential mechanisms of sudden death, and in defining therapeutic algorithms that may improve prognosis. It has also been possible to determine the genetic defect in some of the patients and to correlate clinical findings with the molecular defects. An exciting development has been the use of dual chamber pacemaker as an alternative to cardiac surgery to improve symptoms and relieve LV outflow obstruction.
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Pacing Clin Electrophysiol · Feb 1997
Time dependent variation of stimulus requirements in spinal cord stimulation for angina pectoris.
The aim of the study was to observe changes over time of the stimulation requirements in spinal cord stimulation (SCS). Of 60 patients treated with SCS, 25 patients were selected because they had neurostimulators capable of measuring impedance noninvasively, and had not experienced electrode displacement. All 25 patients had Medtronic Pisces Quad 3487A (Medtronic, Inc.) neuroelectrodes with the tip positioned in the thoracic epidural space. ⋯ After that period, only minor deviations were observed in most patients. To optimize the pain reducing effect of the spinal cord stimulation, frequent follow-ups are recommended during the first month; later on, the follow-up intervals can be extended. No tolerance development or pain resistance developed during SCS treatment.