Papers by rick schuessler
Computers in Cardiology 1998. Vol. 25 (Cat. No.98CH36292), 1998
The authors hypothesized that propagation direction (PD) during atrial fibrillation (AF) is relat... more The authors hypothesized that propagation direction (PD) during atrial fibrillation (AF) is related consistently to gradient of 90% action potential duration (APD90). Monophasic action potentials (MAPs) were recorded at 250 sites from the endocardium of acetylcholine (ACh) perfused canine right atria during pacing. The APD90 field and its gradient were computed from MAP waveforms. Two-dimensional velocity vector fields were estimated from epicardial mapping data acquired during ACh mediated AF. Average PD vector fields were compared to vector fields of APD90 gradient. In 27 episodes of AF, the relationship between PD and APD90 gradient was no different from that of an equal number of uniformly random vectors. However, the curl of PD was higher at sites of large APD90 gradients. Methods were validated in 2-D simulations.
The Journal of Thoracic and Cardiovascular Surgery, 1991
The Journal of Thoracic and Cardiovascular Surgery, 1988
The Journal of Thoracic and Cardiovascular Surgery, 1992
American Journal of Physiology-Heart and Circulatory Physiology, 1988
In open-chest dogs, blood pressure was regulated by titrating doses of phenylephrine and nitropru... more In open-chest dogs, blood pressure was regulated by titrating doses of phenylephrine and nitroprusside to determine its effect on heart rate and pacemaker location. Changes in blood pressure correlated with changes in heart rate (r = 0.86). Activation time mapping demonstrated multicentric atrial activation, with a site of origin-rate relationship. The fastest pacemakers were located in the most cranial regions and slowest in the most caudal areas. In this chloralose-morphine anesthetized model, autonomic blockade with atropine and propranolol suggests that acute baroreflex-induced changes in heart rate were mediated exclusively by either increased sympathetic or parasympathetic tone and were not associated with inhibition of the opposite system. Division of right and left thoracic cardiac nerves indicated the left sympathetics participated in the baroreflex in 50% of the animals and the left parasympathetics in 90% of the animals. Both the right sympathetics and parasympathetics we...
American Journal of Physiology-Heart and Circulatory Physiology, 1986
In open-chest dogs, right- and left-sided cardiac nerves were stimulated to determine their effec... more In open-chest dogs, right- and left-sided cardiac nerves were stimulated to determine their effect on heart rate, rhythm, and pacemaker location. The majority of the nerves produced chronotropic changes; 72% of the induced rhythms originated from within the atrial pacemaker complex. Ten percent of the stimulations produced an atrio-ventricular (AV) nodal rhythm; most of the time this was induced by the left posterior and anterior ansae and ventrolateral nerves. The dominance of a lateral right atrial pacemaker was observed in 8% of the stimulations; the dorsal cardiac and innominate nerves induced this rhythm the majority of the time. The general trend was for a cranial shift in the location of the pacemaker within the pacemaker complex with sympathetic stimulation and a caudal shift with parasympathetic stimulation. Exceptions to the pattern may be explained by the preferential effect of the nerves on the pacemakers in the right atrium. The study demonstrates, in the canine model, ...
American Journal of Physiology-Heart and Circulatory Physiology, 1980
In a study to examine the basis of rate-related changes in the electrocardiographic P wave we fou... more In a study to examine the basis of rate-related changes in the electrocardiographic P wave we found a multicentric rather than unifocal origin of the atrial depolarization wave in dogs. Three to five pacemakers, or origin points, were distributed over a 30- to 40-mm area compared to the 11-mm size of the sinus node. Two or three of the sites could excite simultaneously, or one specific site would dominate excitation. Each separate origin point dominated excitation within a specific range of heart rates, and on reaching either the upper or lower limits of this range, a new focus abruptly dominated and initiated the atrial wave front. We have obtained evidence to suggest that these findings may be explained by a widely distributed atrial pacemaker complex. The spatial distribution of this system exceeded the dimensions of the canine sinus node by a factor of three to four times. The pacemaker centers, although distributed, were consistently located at specific positions along the supe...
American Journal of Physiology-Heart and Circulatory Physiology, 1983
Having previously described the multicentric origin of the atrial impulse from sites widely distr... more Having previously described the multicentric origin of the atrial impulse from sites widely distributed over the right atrium as well as an intrinsic link between these sites of origin and cycle length (CL), we undertook a quantitative study of this relationship. In 132 dogs anesthetized with pentobarbital sodium or fentanyl citrate, we recorded atrial activation sequence maps from 360 closely positioned electrodes and determined locations of impulse origin at heart rates between 80 and 240 (CL between 750 and 250). We used cardiac nerve stimulation and agonist-antagonist infusion to produce changes in CL and impulse origin. Results demonstrate a significant correlation between site of impulse origin and CL. These sites, associated with both the sinus node (SN) and extranodal sites, function predictably and consistently controlling impulse initiation at heart rates above and below rates at which the SN predominates. This relationship can be used to specify an anatomic-functional mod...
American Journal of Physiology-Heart and Circulatory Physiology, 1995
Activation sequence maps derived during normal sinus rhythm from extracellular potentials in the ... more Activation sequence maps derived during normal sinus rhythm from extracellular potentials in the canine right atrium exhibit widely separated sites of origin. The objectives of this study were to characterize the distribution of pacemakers within the right atrium and to determine the relationship of pacemaker action potentials to sites of earliest surface activation as well as to local extracellular electrograms. The right atria of six adult mongrel dogs were rapidly excised under deep pentobarbital sodium anesthesia and perfused with 95% O2-5% CO2 Krebs-Henseleit solution. Action potentials from the epicardial surface were recorded throughout the region bounded by the crista terminalis laterally and the atrial septum medially. Simultaneously, unipolar extracellular electrograms were recorded from 250 endocardial sites. The earliest pacemakers preceded the earliest electrogram by 63 +/- 34 ms; the latest pacemakers followed the earliest electrogram by 71 +/- 40 ms. Primary negativit...
American Journal of Physiology-Heart and Circulatory Physiology, 1990
Unipolar electrograms were recorded from 360 sites in 20 isolated, perfused canine right atria. I... more Unipolar electrograms were recorded from 360 sites in 20 isolated, perfused canine right atria. In 52% of the preparations, spontaneous activation started in the sinus node region. In 32% of the preparations, spontaneous activation was initiated at the junction of the intercaval band and the crista terminalis. Simultaneous multicentric initiation occurred from both sites in 16% of the preparations. With infusion of incrementally increasing doses of norepinephrine, the superior sinus node site consistently assumed dominance. Infusion of incrementally increasing doses of acetylcholine produced no consistent pattern of pacemaker dominance. Propagation velocity during pacing was unaffected by either neurotransmitter. The results demonstrate the presence of two different pacemaker sites in the posterior right atrium that function spontaneously, devoid of any active or significant autonomic input. Exchange of dominance between the two sites occurs in the presence of norepinephrine and ace...
American Journal of Physiology-Heart and Circulatory Physiology, 2001
This study reports the comparative quantitative, morphological, and electrophysiological properti... more This study reports the comparative quantitative, morphological, and electrophysiological properties of two pacemaker cell types, spider and spindle-shaped cells, isolated from the rabbit sinoatrial node. Isolated nodal cells were studied with perforated and ruptured patch whole cell recording techniques. The basic spontaneous cycle length of the spider cells was 381 ± 12 ms, and the basic spontaneous cycle length of the spindle cells was 456 ± 17 ms ( n = 12, P < 0.05). The spider cells had a more positive maximum diastolic potential (−54 ± 1 mV) compared with the spindle cells (−68 ± 1mV, P < 0.05). The overshoot and action potential amplitudes were also smaller in the spider cells. The hyperpolarization-activated inward ( I f) current density, measured from their tail currents, was 15 ± 1.3 pA/pF for the spider cells and 9 ± 0.7 pA/pF for the spindle cells ( P < 0.01). I f current activation voltage was more positive in the spider cells than the spindle cells. Isoproteren...
Computing in Cardiology Conference, Sep 13, 1998
The effect of spatial sampling resolution on estimates of properties of the action potential dura... more The effect of spatial sampling resolution on estimates of properties of the action potential duration (APD90) field was studied in canine atria (n=8). Monophasic action potentials (MAPS) were recorded from the endocardium during Krebs-Henseleit perfusion (KH) (/spl Delta/x=9.5 mm) and were repeated during perfusion with KH+0.5 /spl mu/M acetylcholine (ACh). APD90 was estimated from MAP waveforms. Properties of the APD90 field were computed at spacings (/spl Delta/x) of 3.5 mm, 5 mm, 7.1 mm, 10 mm, and 15 mm. Mean-APD90 and Std-APD90 at spacings greater than 3.5 mm showed no significant difference from estimates based on 9.5 mm (control). Estimates of Mean-GRAD and Std-GRAD (control) based on spacings more than 5 mm were significantly different from estimates based on 3.5 mm. In ACh data, the effect of spacing was similar. Spatial correlation length was similar for sites spaced 10 mm and closer (control & ACh). The authors conclude that accurate characterization of the APDSO field requires a resolution of at least 5 mm. Acetylcholine does not increase resolution requirements.
The heart surgery forum, 2002
The treatment of atrial fibrillation with unipolar radiofrequency (RF) catheter ablation techniqu... more The treatment of atrial fibrillation with unipolar radiofrequency (RF) catheter ablation techniques has been fraught with difficulty. This study was designed to evaluate the potential advantages of bipolar RF energy and its ability to create transmural linear lesions on the beating heart. A right thoracotomy was performed on eight adult sheep. A bipolar RF device was inserted and targeted tissue was clamped between the instrument arms. Ablation was performed on the beating heart. Energy was delivered until the tissue conductance between the two electrodes became constant. A total of 30 lesions were performed. Average ablation time for all lesions was 9.2+/-3.9 seconds with a mean peak temperature of 48.7+/-5.8 OC. Pacing studies demonstrated 100%(30/30) isolation and staining showed that all lesions were transmural. Epicardially delivered bipolar RF energy was able to reproducibly isolate atrial myocardium. As opposed to other energy sources, lesions were always transmural and can b...
Journal of the American College of Surgeons, 2014
Adenosine triphosphate-sensitive (KATP) potassium channel opener diazoxide (DZX) maintains myocyt... more Adenosine triphosphate-sensitive (KATP) potassium channel opener diazoxide (DZX) maintains myocyte volume and contractility during stress via an unknown mechanism when administered at the onset of stress. This study was performed to investigate the cardioprotective potential of DZX when added after the onset of the stresses of hyperkalemic cardioplegia, metabolic inhibition, and hypo-osmotic stress. Isolated mouse ventricular and human atrial myocytes were exposed to control Tyrode's solution (TYR) for 10 to 20 minutes, test solution for 30 minutes (hypothermic hyperkalemic cardioplegia [CPG], CPG + 100uM diazoxide [CPG+DZX], metabolic inhibition [MI], MI+DZX, mild hypo-osmotic stress [0.9T], or 0.9T + DZX), with DZX added after 10 or 20 minutes of stress, followed by 20 minutes of re-exposure to TYR (±DZX). Myocyte volume (human + mouse) and contractility (mouse) were compared. Mouse and human myocytes demonstrated significant swelling during exposure to CPG, MI, and hypo-osmot...
The Journal of thoracic and cardiovascular surgery, 2014
The Cox maze IV procedure has the best results for the surgical treatment of atrial fibrillation.... more The Cox maze IV procedure has the best results for the surgical treatment of atrial fibrillation. It has been traditionally performed through sternotomy with excellent outcomes, but this has been considered to be too invasive. An alternative approach is to perform a less invasive right anterolateral minithoracotomy. This series compared these approaches at a single center in consecutive patients. Patients undergoing a Cox maze IV procedure (n = 356) were retrospectively reviewed from January 2002 to February 2014. Patients were stratified into 2 groups: right minithoracotomy (RMT; n = 104) and sternotomy (ST; n = 252). Preoperative and perioperative variables were compared as well as long-term outcomes. Patients were followed up for 2 years and rhythm was confirmed with an electrocardiogram or prolonged monitoring. Freedom from atrial tachyarrhythmias off antiarrhythmic drugs was 81% and 74% at 1 and 2 years, respectively, using an RMT approach and was not significantly different fr...
Annals of cardiothoracic surgery, 2014
The majority of patients undergoing surgical ablation for atrial fibrillation (AF) worldwide rece... more The majority of patients undergoing surgical ablation for atrial fibrillation (AF) worldwide receive a concomitant mitral valve (MV) procedure. This study compared outcomes of the Cox-Maze IV (CMIV) in patients with lone AF to those with AF and MV disease. A retrospective review of 335 patients receiving either a stand-alone CMIV for AF (n=151) or a CMIV with a MV procedure (n=184) was performed from January 2002 through December of 2012. Data were obtained at 3, 6, 12, 24, and 48 months and patients were evaluated for recurrence of AF. Twenty-four preoperative and perioperative variables were evaluated to identify predictors of AF recurrence at one year. The two groups differed in that stand-alone CMIV patients were younger, had AF of longer duration and had more failed catheter ablations, while patients with AF and MV disease had larger left atria and worse New York Heart Association class (P≤0.001). Operative mortality was higher in the concomitant MV group (1% vs. 5%, P=0.015). ...
Innovations (Philadelphia, Pa.)
Although the advent of ablation technology has simplified and shortened surgery for atrial fibril... more Although the advent of ablation technology has simplified and shortened surgery for atrial fibrillation, only bipolar clamps have reliably been able to create transmural lesions on the beating heart. Currently, there are no devices capable of reproducibly creating the long linear lesions in the right and left atria needed to perform a Cox-Maze procedure. This study evaluated the performance of a novel suction-assisted radiofrequency device that uses both bipolar and monopolar energy to create lesions from an epicardial approach on the beating heart. Six domestic pigs underwent median sternotomy. A dual bipolar/monopolar radiofrequency ablation device was used to create epicardial linear lesions on the superior and inferior vena cavae, the right and left atrial free walls, and the right and left atrial appendages. The heart was stained with 2,3,5-triphenyl-tetrazolium chloride, and each lesion was cross-sectioned at 5-mm intervals. Lesion depth and transmurality were determined. Tran...
Innovations (Philadelphia, Pa.)
Cryoablation is commonly used at present in the surgical treatment of atrial fibrillation (AF). H... more Cryoablation is commonly used at present in the surgical treatment of atrial fibrillation (AF). However, there have been few studies examining the efficacy of the commonly used ablation devices. This report compares the efficacy of two cryoprobes in creating transmural endocardial lesions on the beating heart in a porcine model for chronic AF. In six Hanford miniature swine, the right atrial appendage and the inferior vena cava were isolated using a bipolar radiofrequency clamp to create areas of known conduction block. A connecting ablation line was performed endocardially via a purse string with the novel malleable 10-cm Cryo1 probe for 2 minutes at -40°C. Additional ablation lines were created with the Cryo1 and the 3.5-cm 3011 Maze Linear probe on the right and the left atrial wall. Epicardial activation mapping was performed before and immediately after ablation as well as 14 days postoperatively. Histologic examination was performed 14 days postoperatively. Transmural lesions ...
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Papers by rick schuessler