Biomedical subjects

D J Lang

Publications and source records attributed to D J Lang.

At least 19 recordsLinked to original sources

PubMed2003

Abnormalities of myelination in schizophrenia detected in vivo with MRI, and post-mortem with analysis of oligodendrocyte proteins.

Schizophrenia unfolds during the late period of brain maturation, while myelination is still continuing. In the present study, we used MRI and T2 relaxation analysis to measure the myelin water fraction in schizophrenia. In schizophrenia (n=30) compared with healthy subjects (n=27), overall white matter showed 12% lower myelin water fraction (P=0.031), with the most prominent effects on the left genu of the corpus callosum (36% lower, P=0.002). The left anterior genu was affected in both first-episode (P=0.035) and chronic patients (P=0.011). In healthy subjects, myelin water fraction in total white matter and in frontal white matter increased with age, and with years of education, indicating ongoing maturation. In patients with schizophrenia, neither relation was statistically significant. Post-mortem studies of anterior frontal cortex demonstrated less immunoreactivity of two oligodendrocyte-associated proteins in schizophrenia (2',3'-cyclic nucleotide 3'-phosphodiesterase by 33%, P=0.05; myelin-associated glycoprotein by 27%, P=0.14). Impaired myelination in schizophrenia could contribute to abnormalities of neural connectivity and persistent functional impairment in the illness.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗

PubMed2001

Clinical validation of new pacing-sensing configurations for atrial automatic capture verification in pacemakers.

INTRODUCTION: This study evaluated an atrial automatic capture verification scheme based on atrial evoked response (AER). Atrial pacing was between Atip and Can (Atip-Can) using different coupling capacitances (CCs). Independent pairs of sensing electrodes between Aring and Vtip (Aring-Vtip) or between Aring and a separate indifferent electrode (Aring-Indiff) were used to reduce pacing-induced afterpotentials. METHODS AND RESULTS: A custom-made external pacing system was used to perform automatic step-up and step-down pacing (0.1 to 7.1 V at 0.5 msec, step size of 0.1 V) using different CCs (2 or 15 microF). Intracardiac signals from Aring-Indiff and Aring-Vtip were independently recorded and analyzed both in real time and off-line to detect AER. Every paced beat also was visually inspected and compared with surface ECG to verify the captures. With the intracardiac signals properly filtered, AER detection was based on the signal within a window of 12 to 65 msec after the stimulus. Data from 27 patients (4 chronic and 23 acute implantations; age 65.6+/-13.9 years) were analyzed. Bipolar atrial lead measurements using a standard pacing system analyzer were as follows (mean +/- SD): impedance 695+/-227 ohms, P wave amplitude 4.2+/-2.3 mV, slew rate 1.1+/-0.9 V/sec, and pacing threshold at 0.5 msec 1.0+/-0.5 V. The results with CC = 2 microF showed that of 9,500 atrial paced beats, correct capture verification rates were 99.8% (Aring-Indiff) and 99.4% (Aring-Vtip). Similar results were achieved with CC = 15 microF (99.7% and 99.5%, respectively). CONCLUSION: AER can be reliably detected using independent pacing (Atip-Can) and sensing (Aring-Vtip or Aring-Indiff) electrodes. Therefore, atrial automatic capture verification by AER detection is feasible.

Adult↗

PubMed2001

An MRI study of basal ganglia volumes in first-episode schizophrenia patients treated with risperidone.

OBJECTIVE: The basal ganglia may contribute to extrapyramidal movement disorders, affective disturbances, and cognitive deficits in schizophrenia. Basal ganglia volumes are putatively affected by antipsychotic medications. The purpose of this study was to determine the long-term effects of risperidone treatment in a cohort of first-episode patients with schizophrenia. METHOD: The subjects were 30 patients with first-episode schizophrenia, 12 patients chronically treated with typical antipsychotics, and 23 healthy comparison subjects. They were scanned by magnetic resonance imaging at baseline. The first-episode patients received 1 year of continuous risperidone treatment, after which they and the comparison subjects were rescanned. Caudate, putamen, and globus pallidus volumes were determined from coronal images. RESULTS: The baseline caudate, putamen, and globus pallidus volumes were significantly larger in the chronically treated patients than in the untreated first-episode subjects and comparison subjects. These volumes did not differ between the first-episode patients and healthy comparison subjects. Basal ganglia volumes were unchanged after 1 year of exposure to risperidone in the first-episode subjects. Extrapyramidal movement disorders were present in the majority of chronically treated patients and more than one-third of the never-medicated first-episode patients at baseline. CONCLUSIONS: This group of first-episode patients did not exhibit abnormalities of basal ganglia volumes, nor were basal ganglia volumes affected by exposure to risperidone. Movement disorders were observed in both first-episode and chronically treated patients, suggesting effects of both illness and medications.

Adult↗

PubMed2000

Hemodynamic sensors.

Present adaptive-rate pacemakers use a range of sensors for implementation in open-loop and closed-loop control systems. Hemodynamic sensors that detect the mechanical action of the heart and blood flow offer additional features to implement physiologic rate adaption in rate-controlling systems and rate-limiting systems. Examples of 2 such sensors are presented.

Arrhythmias, Cardiac↗

PubMed2000

Detection of atrial arrhythmia for cardiac rhythm management by implantable devices.

Implantable atrial defibrillators (IAD) should provide pacing therapy whenever appropriate (ie, typical atrial flutter) to minimize shock-related patient discomfort. Additionally, IADs should provide diagnostics regarding atrial arrhythmia type and frequency of occurrence to enable improved physician management of atrial arrhythmia. To achieve this, IADs should accurately classify atrial arrhythmia such as atrial fibrillation (AF) and atrial flutter (AFL) This article evaluates the performance of an algorithm, atrial rhythm classification (ARC), designed to classify AF and AFL. The ARC algorithm uses maximum rate, standard deviation, and range of the 12 most recent atrial cycle lengths to plot a point in a three-dimensional space. A decision boundary divides the space into 2 regions--faster/unstable atrial cycle lengths (AF) or slower/stable cycle lengths (AFL). Classifications are made on a sliding window of 12 consecutive cycles until the end of the episode is reached. In this way, continuous episode feedback is provided that can be used to help guide device therapy, measure arrhythmia type and frequency of occurrence. Bipolar (1-cm) electrogram episodes of AF (n = 16) and AFL (n = 7) were acquired from 20 patients and retrospectively analyzed using the ARC algorithm. The sensitivity and specificity in this study was 0.993 and 0.982, respectively. The ARC algorithm would have appropriately guided atrial therapy and minimized discomfort associated with defibrillation shocks in this small patient data set warranting further studies. The ARC algorithm may also be beneficial as a diagnostic tool to assist physician management of atrial arrhythmia.

Algorithms↗

PubMed2000

Efficacy of preoxygenation with tidal volume breathing. Comparison of breathing systems.

BACKGROUND: Preoxygenation before tracheal intubation is intended to increase oxygen reserves and delay the onset of hypoxemia during apnea. Various systems are used for preoxygenation. Designed specifically for preoxygenation, the NasOral system uses a small nasal mask for inspiration and a mouthpiece for exhalation. One-way valves in the nasal mask and the mouthpiece ensure unidirectional flow. This investigation compares the efficacy of preoxygenation using the standard circle system with the NasOral system and five different resuscitation bags. METHODS: Twenty consenting, healthy volunteers were studied in the supine position for 5-min periods of tidal volume breathing using the circle absorber system, the NasOral system, and five resuscitation bags in a randomized order. Data were collected during room air breathing and at 30-s intervals during 5 min of oxygen administration. Inspired oxygen, end-tidal oxygen, and end-tidal nitrogen were measured by mass spectrometry. RESULTS: At 2. 5 min of oxygenation, end-tidal oxygen plateaued at 88.1 +/- 4.8 and 89.3 +/- 6.4% (mean +/- SD) for the circle absorber and NasOral systems, respectively. This was associated with inverse decreases in end-tidal nitrogen. At no time did these end-tidal oxygen or nitrogen values differ from each other. Three of the resuscitation bags (one disk type and two duck-bill type with one-way exhalation valves) delivered inspired oxygen more than 90%, and the end-tidal oxygen plateaued between 77 and 89% at 2 min of tidal volume breathing. The other two resuscitation bags (both duck-bill bags without exhalation valves) delivered inspired oxygen less than 40%, and the end-tidal oxygen values ranged between 21.8 +/- 5.0 and 31.9 +/- 8.7%. CONCLUSIONS: The circle absorber and NasOral systems were equally effective in achieving maximal preoxygenation during tidal volume breathing. Resuscitation bags differed markedly in effectiveness during preoxygenation; those with duck-bill valves without one-way exhalation valves were the least effective. Thus, the use of these bags should be avoided for preoxygenation.

Adult↗

PubMed1999

A preview of implantable cardioverter defibrillator systems in the next millennium: an integrative cardiac rhythm management approach.

The implantable cardioverter defibrillator (ICD), a primary therapeutic option for preventing sudden cardiac death, has rapidly evolved since being introduced clinically in 1980. Technologic advances in several key areas have enabled ICDs to provide more sophisticated rhythm management. Recent emphasis has been placed on dual-chamber ICDs possessing adaptive-rate pacing capabilities. Adoption of dual-chamber ICD systems has been rapid. The capabilities of future ICD systems will be governed by an integrative strategy that brings together sets of features specifically targeted at multifaceted rhythm disorders. The addition of atrial therapy will require more sophisticated rhythm discrimination algorithms. ICD technology will improve on several fronts including leads, integrated circuits, batteries, and capacitors. Additionally, state-of-the-art pacemaker technology will continue to be incorporated into ICDs. As these new ICD systems become increasingly sophisticated from an engineering viewpoint, tremendous emphasis will be placed on decreasing the complexity of programming, device interrogation, and patient monitoring during routine patient follow-up. Vast improvements in ICD programming systems may ultimately permit the 1-minute follow-up.

Death, Sudden, Cardiac↗

PubMed1999

Future of bradyarrhythmia therapy systems: automaticity.

Since the first fixed-rate ventricular pacemaker was introduced in the late 1950s, pacing systems have evolved rapidly. Current developments focus on making devices more sophisticated and less complex--a challenging combination. Automaticity features such as beat-by-beat capture verification, sensitivity threshold adaptation, and algorithms to govern dynamically the maximum sensor rate have either recently been introduced or are likely to be introduced in the near future. Technologic advances are likely to allow meaningful improvements in current drain, battery performance, memory capacity, signal processing, telemetry, and programmer interface. Bradyarrhythmia therapy devices of the future promise to go beyond the pacemaker. Ultimately, pacing systems will become part of integrated cardiac rhythm management systems.

Bradycardia↗

PubMed1999

A new defibrillator discrimination algorithm utilizing electrogram morphology analysis.

Inappropriate therapies delivered by implantable cardioverter defibrillators (ICDs) for supraventricular arrhythmias remain a common problem, particularly in the event of rapidly conducted atrial fibrillation or marked sinus tachycardia. The ability to differentiate between ventricular tachycardia and supraventricular arrhythmias is the major goal of discrimination algorithms. Therefore, we developed a new algorithm, SimDis, utilizing morphological features of the shocking electrograms. This algorithm was developed from electrogram data obtained from 36 patients undergoing ICD implantation. An independent test set was evaluated in 25 patients. Recordings were made in sinus rhythm, sinus tachycardia, and following the induction of ventricular tachycardia and atrial fibrillation. The arrhythmia complex is defined as wide if the duration is at least 30% greater than the template in sinus rhythm. For narrow complexes, four maximum and minimum values were measured to form a 4-element feature vector, which was compared with a representative feature vector during normal sinus rhythm. For each rhythm, any wide complex was classified as ventricular tachycardia. For narrow complexes, the second step of the algorithm compared the electrogram with the template, computing similarity and dissimilarity values. These values were then mapped to determine if they fell within a previously established discrimination boundary. On the independent test set, the SimDis algorithm correctly classified 100% of ventricular tachycardias (27/27), 98% of sinus tachycardias (54/55), and 100% of episodes of atrial fibrillation (37/37). We conclude that the SimDis algorithm yields high sensitivity (100%) and specificity (99%) for arrhythmia discrimination, using the computational capabilities of an ICD system.

Algorithms↗

PubMed1998

Improved internal defibrillation success with shocks timed to the morphology electrogram.

BACKGROUND: A previous retrospective study by our group suggested that shocks timed to the upslope of the shocking lead electrogram improved defibrillation efficacy. The goal of this study was to prospectively determine whether defibrillation threshold could be reduced by use of an algorithm that timed shocks to the upslope of coarse ventricular fibrillation (test treatment) compared with shocks delivered asynchronously after 10 seconds of fibrillation (control treatment). METHODS AND RESULTS: Ten pigs were instrumented with a 3-lead system for internal defibrillation. Initial estimates of the energy required to achieve defibrillation E50 for both treatments were made by an up/down method. Subsequently, additional shocks at V50+/-10% and V50-20% were given for each treatment to obtain data points at higher and lower intensities. Probability-of-success curves were estimated for both treatments by the best-fit method. Energies required were significantly lower for the timed shocks than for the asynchronous shocks (P<0.00 1). E80 was reduced 15.5%, from 27.1+/-2.5 to 22.9+/-1.8 J (P<0.002). The width of the probability-of-success curve (E80-E20) for the test treatment was also significantly narrower than that for the control treatment (7.1+/-0.9 versus 10.8+/-1.7, P<0.01). Normalized curve width (E80-E20)/E50 was decreased from 51+/-5% of E50 for control shocks to 37+/-4% of E50 for synchronous shocks (P<0.02). CONCLUSIONS: In this model, defibrillation threshold is lower and more deterministic when shocks are timed to the upslope of the shocking lead electrogram. If a similar reduction is observed in humans, shock timing may lower defibrillation threshold and simplify programming of shock intensity.

Algorithms↗

PubMed1998

Shock timing lowers transvenous defibrillation energy requirement.

Previous studies suggested that time periods exist during ventricular fibrillation when defibrillation shocks are more effective. However, there is no agreement on the amount of energy that can be saved or whether an implantable defibrillator can time shocks to these time periods. We conducted a study having two parts to investigate if there was any advantage to synchronizing internal defibrillation shocks to morphological patterns in ventricular fibrillation (VF). VF electrograms were recorded from the same three-electrode lead system used for internal defibrillation. In Part 1, we found no difference in the probability of successful defibrillation between shocks that were delivered into coarse and fine VF (48% vs 46%). However, shocks that were delivered to the upslope of coarse VF electrograms were more efficacious than those to the downslope of the waveform (67% vs 39%, P < .001). In the second study, we developed a real time computer system to prospectively deliver shocks on the upslope feature we identified in the first study. We found that the energy requirements at E50 and E80 were significantly lower for shocks delivered on the upslope of coarse VF than those delivered randomly at the end of 10 sec. We estimated a probability of success (POS) defibrillation curve using a maximum likelihood method for the timed and random shocks. The POS curve width was significantly narrower for shocks that were delivered to the upslope feature than the control treatment (7.1 +/- 0.9 vs. 10.8 +/- 1.7 J, P < 0.01). If these findings extend to clinical defibrillation, they may allow programming of internal defibrillators at lower energies. This could reduce potential postshock cardiac dysfunction, allow production of smaller devices, and improve battery life.

Animals↗

PubMed1997

Effect of shock timing on defibrillation success.

The goal of this study was to determine whether delivering transvenous defibrillation shocks, coordinated with the up/down-slope VF waveform patterns in the shocking lead, would improve the probability of successful defibrillation. Anesthetized swine (32-38 kg, n = 8) were implanted with an RV-->SVC + SQArray transvenous system to measure VF waveform patterns and to deliver shocks. The shocks were generated by a Cardiac Pacemakers Inc. biphasic waveform generator. Energy required for 50% success probability (E50) was determined using the multishock up-down protocol. VF was repeatedly induced and defibrillation shocks at E50 were given after 10 seconds. The defibrillation outcome, delivered energy (Ed), peak voltage (V), peak current (I), system impedance (Z) and VF waveform pattern at the time of shock were recorded and measured. Out of a total of 685 shocks, 324 (47%) succeeded and 361 (53%) failed. The Ed, V, I, and Z were similar for the two defibrillation outcome groups (success or failure). VF patterns were classified as high or low amplitude at the time of the shock based on the peak-to-peak amplitude of signals recorded between the shocking electrodes. Shocks that coincided with high amplitude VF patterns were further divided into shocks that occurred on the up-slope or on the down-slope. The probability of success when the E50 shocks were coincident with high or low amplitude fibrillation did not differ significantly (Student's t-test: 46% vs 48%. P = NS). However, during high amplitude fibrillation, shocks delivered on the up-slope were significantly more successful than those delivered on the down-slope (Chi-square: 67% vs 39%; P < 0.001). These results suggest that delivering defibrillation shocks during the up-slope of the high amplitude signal in the shocking lead may improve the probability of successful defibrillation of ICDs.

Animals↗

PubMed1996

Technological advances in implantable cardioverter-defibrillators before the year 2000 and beyond.

The implantable cardioverter-defibrillator (ICD) has evolved rapidly since its clinical introduction; product life cycles have been exceedingly short. This swift transition from early shock-only devices to small, programmable, tiered-therapy systems has been driven by 2 major factors: minimally invasive implant procedures and technological innovation. Yet, while many new ICD systems have been introduced recently, even more advanced products are on the horizon before the year 2000 and beyond. In general, devices will be smaller and smarter. Certainly, ICD volume will be further reduced without detrimentally affecting longevity. Endocardial lead systems will become smaller and more versatile. Rhythm discrimination algorithms will become more effective. New adaptive-rate pacing systems that limit the maximum paced rate based on hemodynamic indices will become features of tachyarrhythmia products. Pacing schemes for prevention of supraventricular tachyarrhythmias and improvement of hemodynamic function in patients with congestive heart failure will likely be introduced for clinical evaluation.

Cardiac Pacing, Artificial↗

PubMed1996

Efficacy of the self-inflating bulb in confirming tracheal intubation in the morbidly obese.

BACKGROUND: This study was designed to determine the incidence of false-negative and false-positive results when the self-inflating bulb (SIB) is used to differentiate tracheal from esophageal intubation in morbidly obese patients using two techniques. In technique 1, the SIB is compressed before it is connected to the tube; in technique 2, the SIB is compressed after connection to the tube. METHODS: With institutional review board approval, 54 consenting adult morbidly obese patients (body mass index > 35) undergoing elective surgical procedures were included in the study. After anesthetic induction and muscle relaxation, both the trachea and esophagus were intubated under direct vision with identical cuffed tubes. The efficacy of the SIB in verifying the position of both tubes was tested by a second anesthesiologist. The speed of reinflation was graded as rapid ( < 4 s) or none ( > 4 s), using both techniques. In the case of tracheal intubation, the absence of reinflation was recorded as a false-negative, whereas in cases of esophageal intubation, rapid reinflation was recorded as a false-positive. Identification of tube location by the second anesthesiologist was based on SIB reinflation results from techniques 1 and 2, as well as the presence of a flatuslike sound elicited by technique 2 in esophageally placed tubes. All patients were retested by the SIB after receiving three breaths of 400-500 ml each. In all patients exhibiting false-negative results, six obese patients exhibiting true-positive results, and four nonobese patients exhibiting true-positive results, tracheal responses to the SIB maneuvers were observed directly by a flexible fiberoptic bronchoscope incorporating an airtight system, 15-20 min after mechanical ventilation was instituted. RESULTS: The incidence of false-negative results was initially 30% with technique 1 and 11% with technique 2, but decreased to 4% when technique 2 was used after the delivery of three breaths. The second anesthesiologist initially identified tube location in 92.5% of patients correctly. After the delivery of three breaths, tube location was correctly identified in 96.3% of patients. Fiberoptic bronchoscopic examination of the patients exhibiting false-negative results revealed exaggerated inward bulging of the posterior tracheal membrane during reinflation of the SIB when technique 1 was used. CONCLUSIONS: Contrary to previous investigations in healthy patients, the current study demonstrates a high incidence of false-negative results when the SIB is used to confirm tracheal intubation in morbidly obese patients. If the SIB is used, the technique should include compression of the SIB after connection to the tube and should be used in conjunction with other clinical signs and technical aids. The mechanism of false-negative results in these patients seems to be related to reduction of caliber of airways secondary to a marked decrease in functional residual capacity, and collapse of large airways due to invagination of the posterior tracheal wall when sub-atmospheric pressure is generated by the SIB.

Adolescent↗

PubMed1995

The temporal lobes, reversed asymmetry and the genetics of schizophrenia.

Mechanisms determining temporal lobe structural asymmetries may be involved in the pathogenesis of schizophrenia. To investigate the temporal lobes in familial schizophrenia, computed tomographic scans were obtained from 51 subjects (seven families). Enlargement of sylvian fissures and temporal lobe sulcal spaces was observed in family members with schizophrenia. The posterior one-third of the sylvian fissure was larger on the left side in subjects with schizophrenia, and larger on the right side in unaffected individuals. This disturbed pattern of posterior sylvian fissure asymmetry suggests that adjacent language regions may be affected in schizophrenia. An intermediate degree of disturbance in subjects who had schizophrenia-related illnesses or were obligate carriers suggests that genetic factors may be important determinants of temporal lobe asymmetries in familial schizophrenia.

Adult↗

PubMed1995

Large capacitor defibrillation waveform reduces peak voltages without increasing energies.

UNLABELLED: This study tested the hypothesis that increasing capacitance would allow a reduction in ICD size without reducing the deliverable energy. For example, the volume of a single 450 microF capacitor (390 V peak) is 1/3 less than that of two 250 microF capacitors (780 V), but it can store equivalent amounts of energy. METHODS: Endocardial defibrillation electrodes (3.4 cm) were positioned in the RV apex and at the RA/SVC junction in six mixed-breed, isoflurane anesthetized pigs (41 +/- 3 kg). Three 17-cm ribbon wires were positioned subcutaneously on the left lateral chest (SQArray). Two CPI VENTAK ECDs were equipped to deliver 60/40 biphasic waveforms using either 125 microF (STD) or 500 microF (LD) of capacitance. A 15 shock up/down protocol was used to determine the 50% probability of success levels for each waveform in each animal. Shocks were delivered from RV(-)-->SVC + SQArray(+) in random order. Results were compared using paired Student's t-tests and are reported as mean +/- SE. RESULTS: The 500 microF, long duration waveform reduced peak voltage 41% (374 +/- 18 V [STD] vs 219 +/- 14 V [LD], P < 0.001) and reduced peak current 38% (11.0 +/- 1.1 A [STD] vs 6.8 +/- 0.6 A [LD], P < 0.001) but did not significantly change the delivered energy (12.4 +/- 1.3 J [STD] vs 13.4 +/- 1.0 J [LD]). Durations increased from 10.0 +/- 0.2 to 17.6 +/- 0.5 msec (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Implantable cardioverter defibrillator lead technology: improved performance and lower defibrillation thresholds.

The performance of an ICD system depends, in part, on the effectiveness with which the lead system functions. Engineering trade-offs are made during the design of a lead to optimize one or more performance characteristics: e.g., lead handling, fatigue life, size, and optimized therapy delivery. To assure low defibrillation thresholds, careful attention must be taken during the design process to prevent these trade-offs from hampering the lead's therapy effectiveness. Four basic design rules are described that capture many of the engineering concepts that will enhance a lead's efficacy: (1) minimize electrode pullback, (2) deliver current to the apex, (3) minimize energy loss in the lead, and (4) use large, efficient electrodes. These rules speak to optimizing delivery of current to the heart and efficiency of the lead and electrode interface. When the lead performs its function well, the complete ICD system of the heart, lead, and implantable pulse generator will provide optimal safety margins for device implant and an increased number of patients that can be implanted with a single-lead system.

Animals↗

PubMed1995

Position of epicardial patch electrodes for implantable defibrillation significantly affects shock strength requirements.

OBJECTIVE: To assess the impact of epicardial patch electrode position on internal defibrillation efficacy. METHODS: Two mesh patch electrodes (13 cm2) were positioned on the epicardium of acute, isoflurane-anesthetized pigs (n = 7, 40-47 kg). Defibrillation efficacy was determined for three different patch positions: P1 = anterior-basal right ventricle (RV) and lateral-apical left ventricle (LV); P2 = lateral RV and lateral LV; and P3 = anterior-basal septal region and posterior-apical septal region. To quantify defibrillation efficacy, single capacitor discharge, fixed-tilt (68%) biphasic waveforms were delivered to the heart 10 seconds after initiation of ventricular fibrillation. Initial shock intensities were selected using an up/down protocol. Conversion data were used to construct sigmoidal curves relating probability of defibrillation to energy delivered, peak voltage, and peak current in each animal. RESULTS: Mean peak voltage and current at 50% defibrillation probability were 40% higher for P2 than they were for either P1 or P3 (p < 0.05). Similarly, mean energy delivered was 75% higher for P2. In this pig model, position of epicardial patch electrodes affects defibrillation efficacy. CONCLUSION: Apical-to-basal shock vectors (P1 and P3) yielded significantly lower defibrillation shock strength requirements than did a lateral-wall-to-lateral-wall vector (P2), which was perpendicular to the intraventricular septum. These data may help explain the disparity in defibrillation thresholds observed in the human population of patients undergoing implantable cardioverter defibrillator testing with epicardial patch electrodes.

Animals↗