Canine Preparation Research Articles

The influence of the tooth preparation finish line position on the expression of matrix metalloproteinase-9 and the presence of periodontopathogens in the gingival crevicular fluid.

The objective of the study was to determine the concentration of matrix metalloproteinase 9 (MMP-9) and changes in the presence of periodontopathogens in the gingival crevicular fluid before and after tooth preparation with the subgingival and equigingival finish line position. The clinical prospective study included 20 subjects with an indication for upper canine preparation, with the subgingival (group 1) and equigingival finish line (group 2). Samples were taken in four observation intervals: 5 minutes before (control samples), as well as 15 minutes, 24 and 72 hours after tooth preparation (experimental samples). Measurement of MMP-9 was done using Enzyme-linked Immunosorbent Assay (ELISA). The presence of bacteria in the gingival fluid was proven by the Polymerase chain reaction (PCR) analysis. The MMP-9 values did not differ statistically significantly between the groups (p=0.524). The MMP-9 values showed a statistically significant difference in the given observation period (p<0.001) with a significant linear increase in values (p<0.001). A significant quadratic trend recorded a decrease in the MMP-9 values 15 minutes after preparation, and an increase 24 hours after preparation, without a significant difference in the interaction between groups (p=0.392). After preparation, a significant difference in the presence of periodontopathogens was confirmed, i.e., a decrease in the presence of Prevotella intermedia (p=0.025) and Tannerella forsythia (p=0.016) in group 1, and an increase in the presence of Aggregatibacter actinomycetemcomitans in both groups (p=0.029, p=0.026). The study is a good basis for determining the influence of tooth preparation on gingival inflammation, with therapeutic (choice of preparation technique) and preventive significance regarding the protection of the periodontal tissue from possible iatrogenic damage.

Doxycycline hyclate in late-term pregnant mares: pharmacokinetics, diffusion to the fetoplacental unit and safety in the resulting foal

Doxycycline is a second-generation tetracycline with excellent tissue penetration, high-protein-binding, and 5-10-fold higher lipophilic character than tetracycline. It is used to treat difficult-to-identify and atypical pathogens in diseases such as granulocytic anaplasmosis, Potomac fever, Lyme disease, and placentitis caused by Leptospira and nocardioform Actinomycetes. Despite routine use of doxycycline in pregnant mares, there is no data on their pharmacokinetics during pregnancy, transplacental diffusion, or potential toxicity to the fetus and resulting foal. This study aimed to determine the pharmacokinetics of doxycycline in the late-pregnant mare, its diffusion to the fetoplacental unit and its safety in the neonate. The study hypothesizes that doxycycline crosses the equine fetoplacental unit after administration during late-term pregnancy and is safe for the resulting foal. In experiment 1, six mares received a dose of compounded doxycycline hyclate (10mg/kg, p.o.) at 300d of gestation. Doxycycline plasma concentrations were measured with LC-MS/MS at 0, 0.25, 0.5, 0.75, 1, 2, 3, 4, 6, 8, 10, 12, 24, and 48h after administration to confirm absorption and pharmacokinetics. The compounded doxycycline used herein was absorbed rapidly, and maximum plasma concentrations were achieved in 0.79h. Pharmacokinetic parameters of the doxycycline were similar to previous studies using commercial canine preparations. In experiment 2, transplacental diffusion and safety to the resulting foal were studied after administration of repeated doses ofdoxycycline to late-term pregnant mares. Seven mares received doxycycline (10mg/kg p.o. q12h) from 320d of gestation until foaling, and six gestationally-age-matched mares served as controls. Once impending signs of imminent parturition were detected coupled with mammary gland secretion pH ≤6.4, foaling was induced with oxytocin (10-units, intramuscularly) to ensure a controlled sampling of fetal fluids. Fetal fluids and foal synovial fluids were harvested at foaling to determine doxycycline concentrations with LC-MS/MS. After parturition, foals had daily clinical examinations, blood chemistry, and complete blood cell counts performed for seven days. Shapiro-Wilk was used to test normal distribution and data were analyzed with ANOVA and Tukey's as post hoc. Mares received doxycycline on average for 15±2d (range 9-23d). No adverse side effects were associated with doxycycline treatment, and complete blood cell count or blood chemistry pre- and post-partum remained within normal reference ranges. Gestation length for doxycycline-treated mares (335±2d) was similar to controls (339±4) (P=0.4). Concentrations of doxycycline were 9-fold higher in the allantoic fluid (73.5±13.9ng/mL) than amniotic fluid (8.3±3.3ng/mL) and 1.5-fold higher in the foal's plasma (35.5±4.3ng/mL than its synovial fluid (23.6±4.3ng/mL). In conclusion, doxycycline was well-absorbed and detectable in fetal fluids, foal plasma, and synovial fluid, and no adverse effects were observed in mares nor their foals.

Cytomorphometric and Clinical Changes in Gingival Tissue after Subgingival Tooth Preparation-A Pilot Study.

Tooth preparation for a metal-ceramic crown with a subgingival finish line can lead to inflammatory changes in the gingival tissue, often accompanied by cell damage. This study aimed to evaluate the clinical signs of inflammation and the cytomorphological status of the gingival tissue before and after tooth preparation. The research included a homogeneous group of 19 patients with an indication for upper canine preparation. Before and after treatment, the gingival and the gingival bleeding indexes were determined, gingival swabs were taken, and direct smears prepared on slides for cytomorphometric analysis. The values of the measured gingival indexes were statistically significantly higher (p < 0.001) after tooth preparation. They decreased over time, which indicated the reversibility of the resulting changes. Cytological examination showed no statistically significant difference between the values of nuclear area, perimeter, Feret diameter, Feret angle, integrated optical density, MinFeret, and roundness, before and after the treatment. Significantly higher values of circularity, integrated optical density, MinFeret (p < 0.05), as well as roundness (p < 0.001) were found after 72 h, compared to those taken 15 min after tooth crown preparation. This study is a pioneering attempt to show gingival changes during fixed prosthodontic treatment and may shed new light on pathogenetic events in prosthodontic patients.

Comparing the accuracy of six intraoral scanners on prepared teeth and effect of scanning sequence.

PURPOSEThe aim of this study was to evaluate the accuracy of six recently introduced intraoral scanners (IOSs) for single crown preparations isolated from the complete arch, and to determine the effect of scanning sequence on accuracy.MATERIALS AND METHODSA complete arch with right and left canine preparations for single crowns was used as a study model. The reference dataset was obtained by scanning the complete arch using a highly accurate industrial scanner (ATOS Core 80, GOM GmbH). Six different IOSs (Trios, iTero, Planmeca Emerald, Cerec Omnicam, Primescan, and Virtuo Vivo) were used to scan the model ten times each. The scans performed with each IOS were divided into two groups, based on whether the scanning sequence started from the right or left quadrant (n=5). The accuracy of digital impression was evaluated using three-dimensional analyzing software (Geomagic Studio 12, 3D Systems). The Kruskal Wallis and Mann-Whitney U statistical tests for trueness analysis and the One-way ANOVA test for precision analysis were performed (α=.05).RESULTSThe trueness and precision values were the lowest with the Primescan (25 and 10 µm), followed by Trios (40.5 and 11 µm), Omnicam (41.5 µm and 18 µm), Virtuo Vivo (52 and 37 µm), iTero (70 and 12 µm) and Emerald (73.5 and 60 µm). Regarding trueness, iTero showed more deviation when scanning started from the right (P=.009).CONCLUSIONThe accuracy of digital impressions varied depending on the IOS and scanning sequence used. Primescan had the highest accuracy, while Emerald showed the most deviation in accuracy for single crown preparations.

Compound Motor Action Potential Measures Acute Changes in Laryngeal Innervation.

Vocal fold paralysis is caused by injury to the recurrent laryngeal nerve (RLN). Current clinical measures of laryngeal innervation are often nonquantitative. Compound motor action potentials (CMAP) measure motor innervation. The goal of this study was to determine whether CMAP can quantify laryngeal innervation following acute nerve injury. Animal study. Twelve canine hemilaryngeal preparations were used. The RLN was serially stimulated with increasing intensities until the nerve was maximally stimulated. The CMAP amplitude was measured for each intensity stimulation and correlated. Next, the RLN was incompletely transected, and the reduction in CMAP amplitude was correlated to the percentage of transected axons. The percentage of transected axons was determined using horseradish peroxidase (HRP) staining. Combining all hemilaryngeal preparations, the submaximal stimulation of the RLN linearly correlated with the resultant CMAP amplitude (r = 0.83; 95% CI, 0.76-0.88). Following partial RLN transection, the percentage of remaining axons linearly correlated with the CMAP amplitude (r = 0.87; 95% CI, 0.34-0.98). CMAP amplitude is a quantitative measure that may correlate with the degree of vocal fold innervation in canines. Following RLN injury, CMAP may help clinicians quantify the number of intact axons, assess the likelihood of recovery, and counsel patients on their prognosis.

Methods for the Preparation of an Excised, Cross-Circulated Rat Heart.

The Emax-Pressure-Volume Area (PVA)-VO2 framework proposed by Dr. Suga for canine hearts has dramatically advanced the field of cardiac mechanical work and energetics, i.e., mechanoenergetics. He and his collaborators investigated mechanoenergetics in the left ventricle (LV) of excised, cross-circulated canine heart preparations. We instituted the excised cross-circulated rat whole heart preparations and found a curvilinear end-systolic pressure-volume relation (ESPVR) in the rat LV, in contrast to the linear ESPVR in canine, rabbit, and human LVs. Although Emax, the slope of the linear ESPVR, could be used as an index of LV contractility, it was not applicable for evaluating LV contractility in the rat LV. Thus, we proposed a new index of contractility, equivalent Emax (eEmax) in the rat LV. We also found a linear VO2-PVA relationship in the rat LV. Here, we introduce the methods for the preparation of excised, cross-circulated rat whole hearts and the eEmax-PVA-VO2 framework in the rat LV. Using this method, we can obtain accurate LV volume and myocardial O2 consumption in real time for estimating cardiac mechanoenergetics, which is very challenging in in vivo experiments.

犬の歯肉炎に対するイヌインターフェロンα製剤投与後の長期経過観察

犬の歯肉炎に対するイヌインターフェロンα製剤投与後の長期経過観察

Lateral Cricoarytenoid Release: Development of a Novel Surgical Treatment Option for Adductor Spasmodic Dysphonia in a Canine Laryngeal Model.

To investigate the efficacy of a novel adductor muscle-releasing technique designed to decrease the force of vocal fold adduction, as a potential surgical therapy for patients with adductor spasmodic dysphonia (ADSD). Experimental animal study. A canine laryngeal model was used to assess the acute and sustained efficacy of a lateral cricoarytenoid (LCA) muscle release. A total of 34 canine hemilaryngeal preparations were divided among 7 experimental groups. The LCA muscle was separated from its cricoid cartilage origin via an open, anterior, submucosal approach. The laryngeal adductory pressures (LAP) were assessed pre- and post-muscle release via direct recurrent laryngeal nerve stimulation. Measurements were repeated at 1.5, 3, or 6 months postoperatively. Another study evaluated release of the thyroarytenoid (TA) muscle from its thyroid cartilage origin. Releasing the LCA muscle demonstrated a significant decrease in LAP acutely and was maintained at all 3 time points with the aid of a barrier (P < .05). Without the barrier, the LCA muscle reattached to the cricoid. Acute release of the TA muscle did not significantly decrease the LAP. The proposed LCA release procedure may provide patients with a permanent treatment option for ADSD. However, longer-term studies and human trials are needed.

Partial Uncoupling of Impulse Source to Atrial Tissue by Ablation Triggers De Novo Ectopic Beats Through Paradoxical Improvement of Impulse Propagation

Background A source-sink mechanism plays a crucial role in transmission of electrical impulse to tissue. We hypothesized that partial uncoupling of impulse source to tissue by ablation might generate ectopic beats. Methods Canine right atrial preparations (n = 5) were coronary perfused and optically mapped using ANBDQBS, a near-infrared voltage-sensitive dye, to assess the origin and spread of excitation in transmural layers. The sinus node (SN) and surrounding atrial tissue in the field of view were reconstructed after Masson-trichrome, H&E, and immunofluorescence. Masson-trichrome histology was merged with the optical mapping. Cryoablation at –70°C for >3 minutes was performed in the SN and the atrial tissue. Results At baseline, sinus impulse originated from a specific cluster of the histologically demarcated SN (n = 5, 124 ± 23 bpm). Random extensive cryoablation on the SN and atrial tissue caused de novo activation of the ectopic foci outside the field of view (n = 3/5). We also observed the ectopic focus outside the histologic SN independently producing only spontaneous electrical oscillatory waves at baseline before ablation (n = 1), which was composed of HCN4 + cells in immunohistochemistry. However, this isolated electrical activity failed to propagate to the large atrium, as evidenced by the inability of this cluster to generate P waves on the pseudo-ECG. We created partial uncoupling of the nonpropagated ectopic source to the large atrium by cryoablation. In contrast to preablation, the nonpropagated ectopic source acquired the ability to propagate to the surviving atrial myocardium and generated ectopic beats. Conclusions The current study suggests that incomplete ablation may induce ectopic beats through paradoxical improvement of impulse conduction to the cardiac tissue by reducing coupling of impulse source to atrial sink. The current study may provide a mechanistic insight and clinical implications on generation of ectopic beats.

Pontine μ-opioid receptors mediate bradypnea caused by intravenous remifentanil infusions at clinically relevant concentrations in dogs

Life-threatening side effects such as profound bradypnea or apnea and variable upper airway obstruction limit the use of opioids for analgesia. It is yet unclear which sites containing μ-opioid receptors (μORs) within the intact in vivo mammalian respiratory control network are responsible. The purpose of this study was 1) to define the pontine region in which μOR agonists produce bradypnea and 2) to determine whether antagonism of those μORs reverses bradypnea produced by intravenous remifentanil (remi; 0.1-1.0 μg·kg(-1)·min(-1)). The effects of microinjections of agonist [D-Ala(2),N-Me-Phe(4),Gly-ol(5)]-enkephalin (DAMGO; 100 μM) and antagonist naloxone (NAL; 100 μM) into the dorsal rostral pons on the phrenic neurogram were studied in a decerebrate, vagotomized, ventilated, paralyzed canine preparation during hyperoxia. A 1-mm grid pattern of microinjections was used. The DAMGO-sensitive region extended from 5 to 7 mm lateral of midline and from 0 to 2 mm caudal of the inferior colliculus at a depth of 3-4 mm. During remi-induced bradypnea (~72% reduction in fictive breathing rate) NAL microinjections (~500 nl each) within the region defined by the DAMGO protocol were able to reverse bradypnea by 47% (SD 48.0%) per microinjection, with 13 of 84 microinjections producing complete reversal. Histological examination of fluorescent microsphere injections shows that the sensitive region corresponds to the parabrachial/Kölliker-Fuse complex.

The isolated ventricular wedge preparation: A valid proof of relevance

b ( o a l P t A What exactly are the electrophysiologic bases accountable for the various ECG waves? In the search for an answer to this fundamental question (in particular with regard to the ST segment and the T wave), 16 years ago Yan and Antzelevitch reported the creation of an innovative experimental model—the isolated, coronary-perfused canine ventricular wedge preparation. The thought was to use it as a tool for studying the temporal correlation between action potentials recorded across the ventricular wall and the corresponding “transmural” (pseudo) ECG. In that the ECG electrodes are placed facing the epicardial (Epi [ ]) and endocardial (Endo [ ]) surfaces of these preparations, stimulation applied to Endo results in a depolarization wavefront in the Endo-to-Epi direction, which, in turn, accounts for the electrocardiographic R wave. Conversely, since the repolarization wavefront follows the same direction, the T wave is upright. At the start, a well-defined parameter (of potential clinical relevance) readily derived from the ECG of these isolated tissues. I am referring to the “terminal portion of the T wave,” which is (certainly in the wedge) an expression of transmural dispersion of repolarization and, therefore, an index of vulnerability to arrhythmogenesis. The critical observation is that its peak appreciably coincides with full repolarization of the Epi and its end with full repolarization of the sub-Endo (M-cell) action potentials. This time interval was understandably called Tpeak-Tend. The article by Liu et al in this issue of HeartRhythm eports the results of an encouraging, truly blinded validaion study that further highlights the capability of the wedge reparation—in this case isolated from the left ventricle of he rabbit heart. In their study, not only the proarrhythmic isk of several cardiac and noncardiac drugs could be quanified, but their underlying mechanisms of action could also e “blindly” recognized. In essence, their experimental proocols were designed to differentiate the effect of 14 comounds (at various concentrations and pacing rates) on the asis of their effects on the QRS, QT, Tpeak-Tend, and

Pontine μ‐opioid receptors mediate the bradypnea caused by clinically relevant rates of intravenous remifentanil in dogs

Life‐threatening side effects such as profound bradypnea or apnea and variable upper airway obstruction limit the use of opioids for analgesia. It is yet unclear which sites containing mu‐opioid receptors (MORs) within the respiratory control network are responsible. The purpose of this study was 1) to define the pontine region in which MOR agonists produce bradypnea and 2) to determine whether antagonism of those MORs reverses bradypnea produced by IV remifentanil (remi; 0.1–1.0 μg/kg/min). The effects of microinjections of agonist [D‐Ala2, N‐Me‐Phe4, Gly‐ol5]‐enkephalin (DAMGO; 100 μM) and antagonist naloxone (NAL; 100 μM) into the dorsal rostral pons on the phrenic neurogram were studied in a decerebrate, vagotomized, ventilated, paralyzed canine preparation during hyperoxia. A 1‐mm grid pattern of microinjections was used. The DAMGO sensitive region extended from 5–7 mm lateral of midline and from 0–2 mm caudal of the inferior colliculus at a depth of 3–4 mm. During remi‐induced bradypnea (71.5±3.6% reduction in breathing rate; 21 dogs) NAL microinjections (860±69 nl each) within the region defined by the DAMGO protocol were able to reverse bradypnea (47.2±5.2%/injection) with 13 of 84 injections producing complete reversal. Histological examination of dye injections shows that the sensitive region corresponds to the parabrachial Kölliker‐Fuse complex. Supported by VA Medical Research Funds.

Heterogeneous electrographic myocardial response during ischemia

Introduction: Myocardial ischemia is a pathological condition initiated by supply and demand imbalance of the blood to the heart. Electrocardiographic ST-segment shifts are often used as markers for ischemia. Literature suggests that the progression of ischemia occurs from the endocardium, which has the highest metabolic demand, and spreads toward the epicardium, eventually becoming transmural. Our study with animal models has found the progression of ischemia to be more complex and heterogeneous in its distribution. Methods: We used in situ canine preparation, wherein the animals were subjected to demand ischemia by reducing coronary flow and increasing the heart rate through atrial pacing. Epicardial and transmural electrograms were recorded using a 247-electrode sock and up to 400 transmural needle electrodes. Results: At reduced coronary flow, increasing heart rates caused pockets of ischemic regions, characterized by ST-potential elevations to appear variously distributed in the epicardial, midmyocardial, and subendocardial regions. Further reduction in coronary flow and simultaneously increasing the heart rates increased the extent and the magnitude of the ischemic regions that eventually became transmural. Conclusion: The electrographic response of the heart to myocardial ischemia, contrary to earlier belief, is a much more complex phenomenon characterized by heterogeneous distribution and progression of ischemic regions.

Therapeutic management for post‐traumatic treatment of the anterior dental region: a case report with long‐term follow up

The treatment plan represents the final step in every diagnostic procedure and is the result of a series of assessments based on information gathered from a detailed clinical history. This clinical case reports the replacement of two central incisors that were lost because of a trauma. The advantages and disadvantages of the two treatment options (i.e. implantology or prosthetic restoration) were carefully evaluated in relation to the case in hand. Patient compliance and aesthetic requirements had been also considered. In this case, a conventional prosthetic restoration was performed using a metal-ceramic bridge, utilising full crowns between the right and left maxillary lateral incisors associated with minimal canine preparation. By this strategy, the treatment plan allows for a future implant restoration, should this become necessary.

Antiarrhythmic and electrophysiological effects in-vivo of the major metabolite of Org 7797 found in canine and rodent liver homogenate preparations.

Org 20781, the major metabolite of Org 7797 found in in-vitro experiments was examined for antiarrhythmic and electrophysiological effects in-vivo. Org 20781 (0.5-2.0mg kg-1, i.v.) inhibited the development of early ischaemia-induced arrhythmias in rats, suppressed spontaneous ventricular tachycardia (VT) in conscious dogs with 24-h old infarcts, and prevented electrical induction of VT in dogs with 5-6 day old infarcts, actions associated with slowing of conduction at all levels of the myocardium. Cardiac refractory periods were only modestly prolonged whilst repolarization was unchanged. Peak plasma levels of the parent compound (infused to total doses of 2-4 mg kg-1) associated with suppression of late arrhythmias were 6-18 microM, whilst the mean plasma elimination half-life (in normal dogs) was 107 min. It was concluded that the major metabolite has a similar antiarrhythmic and electrophysiological profile to the parent compound, is at least half as potent and may contribute to the therapeutic effects of Org 7797 administration.

New Risk Stratification Markers in Brugada Syndrome

Although spontaneous type 1 ECG has been reported as a predictor of the Brugada syndrome, many patients without documented ventricular fibrillation (VF) have this ECG type and detailed risk stratification will be required. Recently, we proposed new two ECG markers to predict patients’ risk: fragmented QRS (fQRS) and spontaneous ECG alterations (ECG-alt). The fQRS is defined as multiple spikes within QRS complex in leads V1–V3 (≥4 spikes in one lead). The ECG-alt is defined as day-by-day spontaneous ECG type change or changes in ST level ≥0.2 mV. Both fQRS and ECG-alt were frequent in patients with VF, but less frequent in patients without any symptoms (fQRS: asymptomatic patients 34%, VF patients 95%, p<0.01; ECG-alt: asymptomatic patient 44%, patients with VF 97%, p<0.01). Multivariate analysis showed both fQRS and ECG-alt were associated with occurrence of VF. Experimental studies using canine wedge preparation model of Brugada syndrome showed that the fQRS and the ECG-alt represented delayed conduction and unstable repolarization at right ventricular epicardium, respectively. Existence of both repolarization and depolarization abnormalities will be associated with initiation of the VF. Because new onset of VF is less frequent in asymptomatic patients with Brugada syndrome, these two markers should be verified by future prospective study. A recent prospective study in Italy (PRELUDE) that was reported in HRS2011 showed QRS fragmentation as significant and independent predictors of arrhythmic events (hazard ratio: 4.94).

Contractile Strength during Variable Heart Duration Is Species and Preload Dependent

We investigate the effect of beat-to-beat variability on cardiac contractility. Cardiac trabeculae were isolated from the right ventricle of rabbits and beagle dogs and stimulated to isometrically contract, alternating between fixed steady state versus variable interbeat intervals. Trabeculae were stimulated at physiologically relevant frequencies for each species (dog 1 and 4 Hz; rabbit 2 and 4 Hz) intercalating fixed periods with 40% variability. A subset of the trabeculae (at 90% of optimal length) was stretched prior to stimulation between 5 and 13% and stimulated at the same frequencies with a fixed versus 40% variation. Fixed rate response at the same base frequency was measured before and after each variable period and the average force reported. In canine preparations no change in force was observed as a result of the imposed variability in beat-to-beat duration. In the rabbit, we observed a nonsignificant decrease in force between fixed and variable pacing at both 2 and 4 Hz (n = 8) when 40% variability was introduced. When a 5% and 13% stretch was applied, the correlation coefficient sharply increased, indicating a more prominent impact of the prebeat duration on the following cycle with higher preload.

Counterpoint: Left ventricular volume during diastasis is not the physiological in vivo equilibrium volume and is not related to diastolic suction

Counterpoint: Left ventricular volume during diastasis is not the physiological in vivo equilibrium volume and is not related to diastolic suction

Identification of Hemodynamically Unstable Arrhythmias Using Subcutaneous Photoplethysmography

Determination of hemodynamic status is central to arrhythmia management in the inpatient setting. In contrast, therapy decisions in implantable cardioverter defibrillators (ICDs) are based exclusively on the arrhythmia's electrical signature. Hemodynamic sensing in ICDs would allow tailoring of therapy according to perfusion status. Subcutaneous photoplethysmography (PPG) is an attractive technology for this application because it responds to changes in arterial pressure and can be readily incorporated into the housing of implanted devices. This study evaluated the accuracy of PPG in identifying hemodynamically unstable simulated arrhythmias in an animal model. Rapid atrial and ventricular pacing was used to simulate arrhythmias in an acute preparation of 7 healthy dogs. Aortic pressure and subcutaneous PPG were simultaneously recorded. Simulated arrhythmias were defined as hemodynamically unstable if aortic pressure decreased by >or=15 mmHg, marginally unstable if pressure decreased by 5-15 mmHg, and hemodynamically stable if pressure either increased or decreased by no more than 5 mmHg. An average of 56 arrhythmias were simulated in each animal. Changes in pressure and PPG output were highly correlated, with correlation coefficient of 0.7-0.9. Subcutaneous PPG identified hemodynamically unstable episodes with a sensitivity of 100% for 6 subjects and 80% for 1 subject. Specificity was more than 90% for 6 subjects and was 50% for 1 subject. Subcutaneous PPG detects hemodynamically unstable simulated arrhythmias in an acute canine preparation. If successfully validated in humans, this technology may allow ICD therapy to be specifically tailored according to the hemodynamic status of the arrhythmia.

Relationship between the changes in pulmonary vascular input impedance and the site of action of vasoactive agents in the excised canine lung lobe preparation and model circuit

Relationship between the changes in pulmonary vascular input impedance and the site of action of vasoactive agents in the excised canine lung lobe preparation and model circuit