RESUMEN
BACKGROUND: Several animal and clinical studies have shown that thoracic spinal cord stimulation (SCS) may decrease mean arterial pressure (MAP). A previous study in normotensive participants demonstrated a small reduction in MAP during SCS at the T5-T6 spinal level. It has also been demonstrated that chronic SCS at the subthreshold stimulation level significantly improved angina attacks and 6-minute hall walk distance in drug refractory angina patients. OBJECTIVES: To determine if thoracic SCS at 2 different stimulation strengths would decrease blood pressure (BP) and heart rate (HR) during baseline conditions and during activation of the sympathetic system by the cold pressor test (CPT). METHODS: Six hypertensive participants and 9 normotensive participants were evaluated. The SCS leads were implanted under sedation (midazolam and fentanyl) 3 days prior to the study. The SCS device was not implanted at the time of lead implantation; the exteriorized leads were connected to an external programmer at the time of the study. MAP was measured at the finger using beat-to-beat photoplethysmographic recordings at rest and during CPT with a Finometer (Model 1, Finapress Medical Systems, Amsterdam, The Netherlands). SCS at threshold (100%, SCS100) and subthreshold (80%, SCS80) intensities were randomly performed in the T5-T6 region of the spinal cord during normal conditions as well as during CPT. Each participant had 3 CPTs with the placebo (control, no SCS) CPT always performed first. CPT was performed by immersing the right hand into ice water for 90 seconds. Thirty seconds of beat-to-beat data prior to starting each CPT (baseline) was analyzed. During the 90 second CPT, the median values of the last 30 seconds of data were used for analysis. Heart rate variability (HRV) during baseline and SCS was computed using Kubios HRV Version 2.0 software (University of Kuopio, Kuopio, Finland). Since the median values of HR, MAP and their changes did not follow a normal distribution, groups were compared with a non-parametric Friedman's or Wilcoxon's signed rank test. The HRV data were normally distributed and a repeated measures analysis of variance (ANOVA) was used. RESULTS: SCS did not significantly alter MAP or HR at baseline nor did it appear to blunt changes in MAP or HR in response to CPT. In the normotensive group, MAP was significantly elevated by a median value of 16 mmHg (P<0.001) during the placebo phase, and by 18 and 10.5 mmHg during the SCS80 and SCS100 phases, respectively. In the hypertensive group, an enhanced response to the CPT was observed. In these participants, the MAP was significantly elevated by a median value of 26.8 mmHg (P<0.001) during the placebo phase, and by 20 and 17 mmHg during the SCS80 and SCS100 phases, respectively. There was a non-significant trend for the CPT-induced increase in BP to be attenuated during SCS80. HRV tended to decrease in both the time and frequency domain in hypertensive participants, although this decrease was not statistically significant. LIMITATIONS: This was a pilot study including a limited number of participants CONCLUSIONS: Acute SCS at the T5-T6 region did not significantly alter MAP or HR compared to baseline (no SCS) in participants without sedation, supporting our previous findings in sedated patients. Hypertensive participants had a heightened response to transient cold stress, consistent with the literature. The observation of the tendency for a reduction in HRV in both the time and frequency domain in hypertensive participants is also consistent with the literature. In contrast to acute SCS, the hemodynamic effects of chronic SCS should be explored in the future.
Asunto(s)
Terapia por Estimulación Eléctrica/métodos , Electrodos Implantados/normas , Hipertensión/terapia , Médula Espinal/fisiología , Médula Espinal/cirugía , Adulto , Terapia por Estimulación Eléctrica/instrumentación , Femenino , Humanos , Masculino , Persona de Mediana Edad , Proyectos PilotoRESUMEN
The therapy of spinal cord stimulation (SCS) is based on producing an electrical field on the dorsal surface of the spinal cord that blocks only neuropathic pain (ie, pain from damage to the nervous system). Most SCS devices deliver a biphasic pulse consisting of a pair of equal amplitude pulses with opposite polarity. SCS therapy is based on the gate control theory of pain and has been used for the treatment of diverse conditions of neuropathic pain, including complex regional pain syndromes (CRPS). In addition to CRPS, SCS is helpful in patients with failed back surgery syndrome, degenerative disk disease, and in patients with peripheral neuropathies. When used in the right patient, SCS provides significant pain relief in a majority of patients with CRPS. This review focuses on the effects of SCS on CRPS. In addition, an overview of the state of the art technologies used for implantable SCS medical devices is also provided.
Asunto(s)
Síndromes de Dolor Regional Complejo/terapia , Prótesis e Implantes , Médula Espinal/fisiología , Analgesia , Síndromes de Dolor Regional Complejo/fisiopatología , Síndromes de Dolor Regional Complejo/cirugía , Simulación por Computador , Terapia por Estimulación Eléctrica/instrumentación , Terapia por Estimulación Eléctrica/métodos , Humanos , Médula Espinal/fisiopatología , Insuficiencia del TratamientoRESUMEN
BACKGROUND: Several animal studies support the contention that thoracic spinal cord stimulation (SCS) might decrease arterial blood pressure. OBJECTIVE: To determine if electrical stimulation of the dorsal spinal cord in humans will lower mean arterial pressure (MAP) and heart rate (HR). DESIGN: Case Series METHODS: Ten normotensive subjects that were clinically indicated for SCS testing were studied. Two of the 10 patients who underwent testing were excluded from the analysis because they did not respond to the Cold Pressor Test (CPT). Systolic blood pressure, diastolic blood pressure, and heart rate were measured continuously at the wrist (using the Vasotrac device). SCS was administered with quadripolar leads implanted into the epidural space under fluoroscopic guidance. SCS was randomly performed either in the T1-T2 or T5-T6 region of the spinal cord during normal conditions as well as during transient stress induced by CPT. The CPT was conducted by immersing the non-dominant hand in ice-cold water for 2 minutes. RESULTS: There were moderate decreases in MAP and HR during SCS at the T5-T6 region compared to baseline that did not reach statistical significance. However, SCS at the T1-T2 region tended to increase MAP and HR compared to baseline but the change did not reach statistical significance. Arterial blood pressure was transiently elevated by 9.4 +/- 3.8 mmHg using CPT during the control period with SCS turned off and also during SCS at either the T1-T2 region or T5-T6 region of the spinal cord (by 9.2 +/- 5 mmHg and 10.7 +/- 8.4 mmHg, respectively). During SCS at T5-T6, the CPT significantly increased MAP by 5.9+/-7.1 mmHg compared to control CPT (SCS off). CONCLUSION: This study demonstrated that SCS at either the T1-T2 or T5-T6 region did not significantly alter MAP or HR compared to baseline (no SCS). However, during transcient stress (elevated sympathetic tone) induced by CPT, there was a significant increase in MAP and moderate decrease in HR during SCS at T5-T6 region, which is not consistent with previous data in the literature. Acute SCS did not result in adverse cardiovascular responses and proved to be safe.
Asunto(s)
Presión Sanguínea/fisiología , Terapia por Estimulación Eléctrica/efectos adversos , Terapia por Estimulación Eléctrica/métodos , Frecuencia Cardíaca/fisiología , Manejo del Dolor , Estrés Fisiológico/fisiopatología , Adulto , Anciano , Frío , Femenino , Humanos , Masculino , Persona de Mediana Edad , Médula Espinal , Vértebras TorácicasRESUMEN
BACKGROUND: "Begetting," a mechanistic tenet of atrial fibrillation (AF), stipulates that the rate of recurrence of AF after cardioversion is proportional to the preceding arrhythmia duration. However, recent reports suggest that, for brief durations, the incidence of early recurrence of AF (ERAF) is inversely proportional to duration. These reports were based on potentially biased data. OBJECTIVES: We performed a prospective study to examine the impact of AF duration on postcardioversion recurrence. METHODS: Forty-four patients underwent placement of an implantable cardioverter-defibrillator (ICD) capable of delivering patient-elicited AF cardioversion shocks. Subsequently, in the ambulatory setting, the timing of shocks in relationship to perceived AF onset was randomly assigned within individuals to early (as soon as possible) or delayed (1 day later). RESULTS: During a follow-up averaging 199 days per patient, a total of 61 AF episodes among 17 patients occurred for which a patient-elicited cardioversion shock was delivered. Twenty-three shocks were delivered using early protocol (mean 6.8 hours after AF onset), and 38 shocks were delivered using delayed protocol (mean 34.7 hours after AF onset). The incidence of ERAF was significantly lower using the delayed protocol. CONCLUSION: A strategy of approximately 24-hour delay in cardioversion shock timing decreased the incidence of ERAF, relative to a shock delivered within a few hours of AF onset. This observation has important mechanistic and therapeutic implications.
Asunto(s)
Fibrilación Atrial/terapia , Desfibriladores Implantables , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Recurrencia , Factores de TiempoRESUMEN
An implantable cardioverter defibrillator with atrial therapies (ICD-ATs) is an effective therapy to manage atrial tacharrhythmias. Acceptance of this therapy is limited by atrial shock related anxiety and discomfort. Inhaled nitrous oxide (N2O) is a potent sedative-analgesic-anxiolytic agent that may mitigate shock discomfort and anxiety and improve patient ICD-AT acceptance. ICD-AT patients with more than one ambulatory atrial shock within 12 months were enrolled and grouped by ICD-AT shock method; awake (n = 9) or asleep (n = 4) when ambulatory ICD-AT shock is delivered. A baseline questionnaire assessed the most recent ambulatory ICD-AT shock (3 +/- 3 months). A 65% N2O/35% O2 mixture was inhaled for 4 minutes followed by an ICD-AT test shock (18 +/- 8 J). The test shock mimicked the awake shock method. The test shock experience during N2O was evaluated via questionnaire immediately following and 24 hours after the shock. Shock related anxiety, intensity, pain, and discomfort were assessed using a ten-point rank scale. Baseline test shock scores were similar between the shock method groups. In the awake shock method group, N2O greatly reduced preshock anxiety by 48% (6.4 +/- 2.4 to 3.3 +/- 2.0, or), and shock related intensity (5.9 +/- 3.1 to 3.3 +/- 2.5), pain (5.0 +/- 2.6 to 2.0 +/- 2.1), and discomfort (5.6 +/- 2.4 to 1.3 +/- 1.4) from baseline values by 45%, 60%, and 78% (P < 0.05), respectively. The asleep shock method group reported no changes in shock related anxiety, intensity, pain, or discomfort. Atrial shock concern, assessed via a five-point rank scale (5 = extreme concern) was improved by N2O but only in the awake group (3.1 +/- 1.0 baseline to 1.6 +/- 0.5 N2O, P = 0.008). There were no adverse events with N2O and patients fully recovered within 5 minutes after N2O. In conclusion, 65% N2O greatly reduced shock related pain and discomfort, and significantly reduced atrial shock concern but only in the awake shock method group. The benefits of N2O therapy may expand the use and acceptability of ICD-AT therapy into a larger atrial fibrillation cohort.
Asunto(s)
Analgésicos no Narcóticos , Ansiolíticos , Fibrilación Atrial/terapia , Cardioversión Eléctrica/efectos adversos , Hipnóticos y Sedantes , Óxido Nitroso , Administración por Inhalación , Anciano , Analgésicos no Narcóticos/administración & dosificación , Ansiolíticos/administración & dosificación , Desfibriladores Implantables , Femenino , Humanos , Hipnóticos y Sedantes/administración & dosificación , Masculino , Óxido Nitroso/administración & dosificación , Dolor/tratamiento farmacológico , Encuestas y CuestionariosRESUMEN
Recently, device-based low energy cardoversion shocks have been used as therapy for AF. However, discomfort from internal low energy electrical shocks is poorly understood. The aim of this study was to evaluate pain perception with low energy internal discharges. Eighteen patients with ICD devices for malignant ventricular arrhythmias were recruited to receive shocks of 0.4 and 2 J in the nonsedated state. Discharges were delivered in a blinded, random order and questionnaires were used to determine discomfort levels and tolerability. Patients perceived discharges at these energies as relatively uncomfortable, averaging a score of 7.3 on a discomfort scale of 0-10, and could not distinguish 0.4-J shocks from 2-J shocks. Second shocks were perceived as more uncomfortable than initial discharges, regardless of the order in which the shocks were delivered. Despite the perceived discomfort, 83% of patients stated that they would tolerate discharges of this magnitude once per month, and 44% would tolerate weekly discharges. Patients perceive low energy discharges as painful and cannot distinguish between shocks of 0.4 and 2 J. The results suggest that ICD systems developed to treat atrial tachyarrhythmias should minimize the number of shocks delivered to terminate an atrial tachyarrhythmia episode. The majority of the patients tolerated low energy shocks provided the discharges are infrequent (once per month).
Asunto(s)
Cardioversión Eléctrica/efectos adversos , Dolor/etiología , Disfunción Ventricular/terapia , Adulto , Anciano , Anciano de 80 o más Años , Distribución de Chi-Cuadrado , Cardioversión Eléctrica/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Dimensión del Dolor , Umbral del Dolor , Estudios Prospectivos , Estadísticas no Paramétricas , Encuestas y Cuestionarios , Disfunción Ventricular/fisiopatologíaRESUMEN
OBJECTIVES: We sought to gain insights into the early recurrence of atrial fibrillation (ERAF) after cardioversion shocks delivered by permanently implanted rhythm management systems. BACKGROUND: Several reports have characterized ERAF, but these reports used a limited definition and did not evaluate an association between clinical or device variables and ERAF. METHODS: A total of 144 patients with recurrent, drug-resistant, symptomatic atrial fibrillation (AF) underwent implantation of an atrial rhythm management system (Medtronic Jewel AF, Model 7250, Minneapolis, Minnesota). The device was programmed to deliver cardioversion shocks automatically and/or on patient command. The incidence of ERAF was evaluated after 1,092 successful shocks among 97 patients. Three different ERAF definitions were used: recurrence within 1 min, 1 h or 1 day. Multiple clinical and device variables were assessed for their relationship with ERAF. RESULTS: The per-patient incidences of ERAF were 44%, 61% and 70% for ERAF within 1 min, 1 h and 1 day, respectively. The per-episode incidences of ERAF were 17%, 30% and 43% for ERAF within 1 min, 1 h and 1 day, respectively. Variables that were independently associated with ERAF included AF duration <3 h before termination, more than one shock required to cardiovert and the absence of a previous myocardial infarction. The most potent variable was AF duration <3 h, associated with a threefold increase in the incidence of ERAF. CONCLUSIONS: Recurrence of AF early after ambulatory shock cardioversion is common. In this retrospective study, both clinical and device variables were predictive.
Asunto(s)
Fibrilación Atrial/terapia , Desfibriladores Implantables , Fibrilación Atrial/epidemiología , Estudios de Cohortes , Diseño de Equipo , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Recurrencia , Estudios Retrospectivos , Factores de Riesgo , Factores de TiempoRESUMEN
The combined role of atrial pacing lead location and AV timing on cardiovascular performance has not been defined. This study tested the hypothesis that atrial pacing lead location can change the dependence of LA and LV hemodynamics on AV timing in vivo. Dogs anesthetized with isoflurane (n = 8) were instrumented for measurement of hemodynamics including LA pressure, LA volume, and pulmonary venous bloodflow. Data were recorded during normal sinus rhythm, and atrial overdrive pacing from the right atrial appendage (RAA), proximal coronary sinus (CS), and LA lateral wall (LAW). The AV node was then ablated and measurements repeated during synchronous ventricular pacing and during dual chamber pacing from each atrial lead location at various AV delays (20, 60, 120, 180, 240, and 350 ms). Hemodynamics during intrinsic sinus rhythm and overdrive atrial pacing from different sites were similar. In contrast, ventricular or dual chamber pacing caused significant (P < 0.05) changes in cardiac output with different AV timing during RAA (3.5 +/- 0.2 vs 2.9 +/- 0.2 L/min at 120 and 350 ms, respectively) and LAW pacing but not CS pacing. A significant interaction between atrial lead location and AV delay was observed for changes in stroke volume, pulmonary venous blood transport, LA volume, and LV preload. The results indicate that the atrial contribution to cardiac output depends on AV timing and atrial lead location in isoflurane-anesthetized dogs with AV nodal conduction block.