Effect of body position on transesophageal atrial pacing in dogs.

OBJECTIVE: To evaluate the effect of body position on transesophageal atrial pacing (TEAP) in dogs. STUDY DESIGN: Prospective, experimental trial. ANIMALS: A total of eight mixed-breed dogs, median body mass 25 kg (range 11-31 kg). METHODS: TEAP was performed using a 6 Fr (2 mm) pacing catheter introduced transorally and positioned in the lower esophagus in left lateral recumbency. The catheter was withdrawn in 5 mm increments until successful TEAP. The minimum pacing threshold (MPT) was determined at each 5 mm increment until atrial capture could not be achieved at a maximal pulse amplitude of 40 mA. The zone of capture (ZOC) was the total distance over which TEAP was achieved. The same process was repeated in right lateral, ventral and dorsal recumbency. A linear mixed model was used to assess the impact of body position on TEAP and ZOC. RESULTS: TEAP was achieved in all body positions. There was significant random effect of individual dogs on ZOC (p = 0.048) but not on MPT (p = 0.109). MPT was 11.56 ± 8.65 mA (mean ± SD), 8.43 ± 2.29 mA, 10.63 ± 6.91 mA and 10 ± 7.44 mA for dorsal, left and right lateral, and ventral recumbency, respectively. ZOC was 5.12 ± 2.08 cm, 6.35 ± 2.41 cm, 5.94 ± 3.23 cm and 5.31 ± 2.2 cm for dorsal, left lateral and right lateral, and ventral recumbency, respectively. Neither ZOC (p = 0.363) nor MPT (p = 0.716) varied significantly between body positions. CONCLUSIONS AND CLINICAL RELEVANCE: TEAP can be performed successfully in all body positions in dogs. Body position did not significantly influence MPT or ZOC values for TEAP. Further studies are needed to compare the efficacy of TEAP with the efficacy of standard pharmacological therapy for management of bradycardia during general anesthesia in dogs.

Treatment of Congestive Heart Failure with Intravenous Nitroglycerin in Three Dogs with Degenerative Valvular Disease.

We described the use of IV nitroglycerin as adjunctive therapy in three canine patients with left congestive heart failure secondary to degenerative mitral valve disease. All three dogs were admitted for signs of respiratory distress and all were determined to be in left congestive heart failure by history, exam findings, thoracic radiographs, and echocardiography. In addition to standard therapy for left congestive heart failure, IV nitroglycerin was administered as a constant rate infusion at a dose of 1-6 mcg/kg/min. No adverse events attributable to the drug were noted. This is the first reported use of IV nitroglycerin in clinical veterinary patients. Further studies are warranted to investigate the safety, efficacy, and optimal dosing of IV nitroglycerin infusions in dogs with left congestive heart failure.

Effect of pulse width on transesophageal atrial pacing in dogs.

OBJECTIVE: To determine the impact of stimulus pulse width (PW) on pacing threshold (PT), zone of capture (ZOC) and extraneous muscular stimulation (EMS). STUDY DESIGN: Experimental trial in client-owned dogs. ANIMALS: Seventeen dogs, median weight 16.1 kg (interquartile range: 11.4-21.5). METHODS: Transesophageal atrial pacing (TAP) involved a 6 Fr pacing catheter inserted trans-orally into the esophagus to a position aboral to the heart in anesthetized dogs. The catheter was slowly withdrawn until atrial pacing was noted on an electrocardiogram. The catheter was withdrawn in 1 cm increments until TAP could not be achieved. PTs were recorded at each pacing site using PWs of 10.0, 5.0, 2.0 and 1.8 ms, always in that order. RESULTS: The overall lowest mean PTs for all dogs were 6 ± 3 mA, 9 ± 4 mA, 11 ± 5 mA and 13 ± 5 mA at PWs of 10.0, 5.0, 2.0 and 1.8 ms, respectively. A significant decrease in overall minimum PT was noted using a PW of 10.0 ms compared with either 2.0 or 1.8 ms (p = 0.043 and p = 0.001, respectively) and pacing using 5.0 ms compared with 1.8 ms (p = 0.028). A significant increase in ZOC was noted using a PW of 10.0 ms compared with PWs of 5.0, 2.0 and 1.8 ms (p = 0.0047, p = 0.0006 and p = 0.0003, respectively), using a PW of 5.0 ms compared with PWs of 2.0 and 1.8 ms (p = 0.0011 and p = 0.0003, respectively) and using a PW of 2.0 compared with one of 1.8 ms (p = 0.0084). CONCLUSIONS AND CLINICAL RELEVANCE: Use of 10.0 or 5.0 ms PW to perform TAP minimized the power required to pace the atria, while a PW of 10.0 ms maximized the size of the ZOC.

Utility of transesophageal electrocardiography to guide optimal placement of a transesophageal pacing catheter in dogs.

OBJECTIVE: To determine if the transesophageal atrial (A) wave amplitude or ventricular (V) wave amplitude can be used to guide optimal positioning of a transesophageal pacing catheter in dogs. STUDY DESIGN: Prospective clinical study. ANIMALS: Fourteen client owned healthy dogs with a median weight of 15.4 kg (IQR = 10.6-22.4) and a median age of 12 months (IQR = 6-12). MATERIALS AND METHODS: Transesophageal atrial pacing (TAP) using a 6 Fr pacing catheter was attempted in dogs under general anesthesia. The pacing catheter was inserted orally into the esophagus to a position caudal to the heart. With the pulse generator set at a rate 20 beats/minute(-1) above the intrinsic sinus rate, the catheter was slowly withdrawn until atrial pacing was noted on a surface electrocardiogram (ECG). Then the catheter was withdrawn in 1 cm increments until atrial capture was lost. Minimum pacing threshold (MPT) and transesophageal ECG were recorded at each site. Amplitudes of the A and V waves on transesophageal ECG were then measured and their relationship to MPT was evaluated. RESULTS: TAP was achieved in all dogs. In 9/14 dogs the site of lowest overall MPT was the same as the site of maximal A wave deflection. In dogs with at least three data points, linear regression analysis of the relationship between the estimated site of the lowest overall MPT compared to estimated site of the maximal A and V waveform amplitudes demonstrated a strong correlation (R(2) = 0.99). CONCLUSION AND CLINICAL RELEVANCE: Transesophageal ECG A and V waveforms were correlated to MPT and could be used to direct the placement of a pacing catheter. However, the technique was technically challenging and was not considered to be clinically useful to guide the placement of a pacing catheter.

Cardiovascular abnormalities in dogs with acute pancreatitis.

BACKGROUND: The prevalence and clinical importance of cardiac abnormalities in dogs with acute pancreatitis (AP) is unknown. ANIMALS: Twelve dogs with AP and 60 archived serum samples from dogs with suspected AP. METHODS: Two-phase study. PHASE I: Analysis of archived serum samples from dogs with clinical signs of AP and high Spec cPL concentrations. High sensitivity troponin I (TnIH) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations were measured in achieved serum samples. PHASE II: Prospective observational study. Dogs with AP underwent echocardiography and Holter monitoring. Serum cardiac troponin I (cTnI) and plasma NT-proBNP concentrations were measured. Previously described disease severity indices were calculated for each dog. RESULTS: Phase I: 41 of 60 dogs suspected of having AP had abnormally high TnIH concentrations and 13 of 60 had abnormally high serum NT-proBNP concentrations. Higher TnIH concentrations were observed in dogs with Spec cPL concentration >2000 µg/L as compared to those with concentrations of 1000-2000 µg/L. PHASE II: 11 of 12 dogs diagnosed with pancreatitis had abnormal cTnI concentrations (median: 0.384 ng/mL, range: 0.041-2.966 ng/mL, RI: ≤0.06 ng/mL) and 7 of 12 dogs had plasma NT-proBNP concentrations above the reference interval (median: 971 pmol/L, range: 250-2215 pmol/L, RI: ≤900 pmol/L). Supraventricular and ventricular ectopic beats occurred in 3 dogs. Echocardiographic abnormalities were detected in 5 dogs. Cardiovascular variables were not associated with indices of disease severity. CONCLUSIONS AND CLINICAL IMPORTANCE: Myocardial injury is common in dogs with AP, but clinical consequences appeared to be uncommon in our small cohort. Cardiac biomarkers should be interpreted with caution in dogs with AP.

Evaluation of plasma N-terminal pro-B-type natriuretic peptide levels in healthy North American Salukis with normal echocardiographic measurements.

Measurement of N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels has been shown to have clinical significance for diagnosis and management of heart disease in dogs. Evaluation of current reference limits for specific breeds is necessary to ensure the test can accurately distinguish between healthy and diseased animals. The objective of this study is to evaluate the adequacy of currently established NT-proBNP reference limits for clinical use in healthy Salukis. Cardiac health of 33 clinically healthy Salukis was evaluated via echocardiography using available breed standards. Plasma concentrations of NT-proBNP were measured using a commercially available assay. A one-sided 97.5% upper reference limit for the NT-proBNP concentrations was calculated using non-parametric percentile method. The 97.5% upper reference limit was 769 pmol/L (90% CI, 547-1214 pmol/L) for the study dogs. This upper reference limit was within the currently established non-breed specific NT-proBNP upper reference limit of 900 pmol/L. No relationship between sex, age, or body weight on plasma levels of NT-proBNP was noted. Results of this study supports the use of currently available non-breed specific NT-proBNP cut-off values for clinical evaluation of healthy Salukis.

Safety of transesophageal pacing for 24 hours in a canine model.

BACKGROUND: Temporary epicardial pacing is often necessary following surgical correction of congenital heart disease. Epicardial pacing wires, while generally effective, can, however, become nonfunctional. Transesophageal atrial pacing (TEAP) can be a useful adjunct in this setting. The potential for esophageal damage with sustained TEAP is unknown. We assessed the safety of continuous (24 hours) TEAP by evaluating gross and histological changes to the esophagus in a canine model. METHODS: Thirteen juvenile beagle dogs were fitted with a 4-Fr multipolar catheter placed transnasally into the esophagus to a level to sustain atrial capture. Pacing was established in nine dogs for 24 hours while four control dogs had catheters but no pacing stimulus applied. Paced dogs were divided into two groups: group A (n = 5) that were euthanized immediately and group B (n = 4) that were euthanized 7 days after the pacing period. Nonpaced dogs (group C, n = 4) were treated similar to group A. Gross and histological examination of the esophageal tissue was completed. RESULTS: Gross and histological evidence of mild esophagitis was noted in dogs from groups A and C but not in dogs from group B. There was no evidence of esophageal stricture or fibrosis in any dog from any group. CONCLUSIONS: TEAP did not result in permanent esophageal changes after 24 hours of stimulation. Microscopic lesions of mild erosive esophagitis, seen after 24 hours of TEAP, were absent 7 days postpacing. Mechanical irritation from the catheter cannot be ruled out as a cause of these changes.

Ambulatory electrocardiographic evaluation of the occurrence of arrhythmias in healthy Salukis.

OBJECTIVE To determine the frequency and complexity of ventricular arrhythmias in a group of healthy Salukis evaluated by means of continuous Holter monitoring for 7 days. DESIGN Prospective case series. ANIMALS 25 healthy Salukis > 18 months old. PROCEDURES In all dogs, a history was obtained and a physical examination and transthoracic echocardiography were performed to verify the absence of structural cardiac disease. Dogs then underwent Holter monitoring for 7 days. Data recorded included heart rate parameters and the occurrence of conduction disturbances, ventricular premature complexes, ventricular couplets, ventricular triplets, ventricular bigeminy, ventricular trigeminy, and ventricular tachycardia. RESULTS 25 dogs (13 sexually intact females, 2 spayed females, and 10 sexually intact males) were enrolled in the study. All 25 dogs had at least one 24-hour period during which ventricular premature complexes were detected. Median number of ventricular premature complexes during any 24-hour period in all dogs was 2 (interquartile [25th to 75th percentile] range, 0 to 4). There were no significant differences between males and females in regard to median number of ventricular premature complexes per 24-hour period or recorded heart rate parameters. CONCLUSIONS AND CLINICAL RELEVANCE For Salukis in the study population, 7-day Holter monitoring revealed infrequent ventricular arrhythmias. These findings suggested that detection of a ventricular arrhythmia in a healthy Saluki may be an indication for further diagnostic evaluation.

Feasibility of transthoracic echocardiographic imaging in non-sedated ovine subjects using a commercial restraint device.

Transthoracic echocardiography (TTE) is a valuable non-invasive imaging research technique. In ovine models of cardiac disease, restraint for TTE often involves sedation even with currently available restraint equipment; our goal was to determine the feasibility of using a commercial restraint device, commonly known as the sheep chair, in minimizing animal stress and the need for sedation while achieving a complete TTE examination. A total of 10 healthy adult Dorset sheep were restrained in a sheep chair for TTE and observed for signs of stress. No animals displayed overt evidence of stress and none required sedation. While individual anatomic variation existed, image quality was sufficient to determine cardiac function. These observations suggest that a sheep chair is a useful aid in minimizing the need for sedation to acquire a full TTE study in ovine subjects.

Effects of catheter shape, interelectrode spacing, and electrode size on transesophageal atrial pacing in dogs.

OBJECTIVE: To determine effects of catheter shape, interelectrode spacing (IS), and electrode size (ES) on pacing threshold (PT), extraneous muscular stimulation (EMS), and zone of capture (ZOC) for dogs undergoing transesophageal atrial pacing (TAP). ANIMALS: 10 purpose-bred dogs without cardiac conduction disturbances. PROCEDURES: 7 configurations for TAP catheters were tested in each dog to evaluate effects of catheter shape (curved or straight), IS (5, 15, and 25 mm), and ES (2, 4, and 6 mm). Each catheter was passed into the esophagus to a location aboral to the heart and slowly withdrawn until atrial pacing was achieved. Then, catheters were withdrawn in 5-mm increments until pacing could not be achieved. Outcomes measured at each pacing site included PT, degree of EMS, and ZOC. RESULTS: There was a significantly lower PT, wider ZOC, and less EMS for the curved catheter than for the straight catheter. An ES of 6 mm induced significantly more EMS than was induced by an ES of 2 or 4 mm. An IS of 5 mm induced significantly less EMS and a significantly narrower ZOC but required a significantly higher PT, compared with results for an ES of 15 or 25 mm. Additionally, there was a significant direct correlation between IS and ZOC. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that a curved catheter with multiple 4-mm electrodes that provides for variable IS would be ideal for TAP in dogs. IMPACT FOR HUMAN MEDICINE: TAP catheters currently used in human medicine are straight. The PT in humans may potentially be reduced with curved catheters.

Retrospective evaluation of intravenous premixed amiodarone use and adverse effects in dogs (17 cases: 2011-2014).

OBJECTIVE: The goal of this study was to evaluate the number and frequency of adverse effects in a population of clinical canine patients receiving Nexterone. ANIMALS: Seventeen canine patients receiving Nexterone (five of which were treated during cardiopulmonary arrest). METHODS: An electronic records search for canine patients receiving intravenous Nexterone at the Michigan State University Veterinary Teaching Hospital was performed and retrospectively evaluated for patient demographic information, pre- and post-treatment values for heart rate, blood pressure and rhythm diagnosis, as well as any documented adverse effects (hypotension, anaphylaxis, vomiting, phlebitis, and death). Data including the underlying cardiac or systemic disease, concurrent medications, as well as the final clinical diagnosis and treatment outcome were also recorded. RESULTS: No adverse effects were noted in this population of clinical canine patients receiving Nexterone. The median pre-treatment heart rate and blood pressure values were 160 bpm (range 120-300 bpm) and 105 mmHg (range 60-170 mmHg), respectively. After treatment, the median heart rate was significantly lower (120 bpm; range 68-172 bpm). The median blood pressure similar to the pre-treatment blood pressure (115 mmHg; range 100-150 mmHg). CONCLUSION: In this study of 17 dogs receiving the premixed formulation of injectable Nexterone, no dogs were found to have acute adverse side effects. Nexterone appears to be a safe drug choice for in-hospital treatment of canine arrhythmias. Further studies are needed to assess the efficacy and long-term effects of this medication and the ideal dosing protocol for various arrhythmias.

Identification of 8-nonenal as an important contributor to "plastic" off-odor in polyethylene packaging.

Food and beverage products stored in polyethylene (PE) containers may absorb some of PE's volatile minor components and become tainted by its characteristic "plastic" odor. High-density PE containers that had imparted "plastic" odor to an experimental corn chip product were analyzed by simultaneous distillation/extraction to remove the volatile components, by gas chromatography/olfactometry (GC/O) to locate the offending components and by 2-D GC/mass spectrometry (MS) to identify the major "plastic" odor contributor (8-nonenal). The identification was made using high-resolution electron ionization and chemical ionization MS data to narrow the possibilities to two isomers of nonenal, followed by retrieval of reference spectra and confirmatory synthesis. By monitoring 8-nonenal in HDPE containers and corn chips it was demonstrated that 8-nonenal tracks with "plastic" aroma observed in containers and with "plastic" flavor observed in corn chips stored in the containers.

Elucidation of tautomer structures of 2-acetyltetrahydropyridine using gas chromatography/mass spectrometry and gas chromatography/infrared spectroscopy.

2-Acetyltetrahydropyridine is an important flavor component in heated corn products such as popcorn and corn chips. The compound exists as a mixture of two tautomers that have different flavor/aroma characteristics. The tautomers also exhibit different chromatographic behaviors and are distinguishable spectroscopically. Though their electron ionization mass spectra are different, structure assignment based on low-resolution mass spectra alone has been subject to error. A combination of high resolution exact mass measurement and vapor phase infrared measurement of the separated tautomers was used to unambiguously assign the tautomer structures.

Quantitation of acrylamide in food products by liquid chromatography/mass spectrometry.

A simple and inexpensive liquid chromatography/mass spectrometry (LC/MS) method was developed for the quantitation of acrylamide in various food products. The method involved spiking the isotope-substituted internal standard (1-C13 acrylamide) onto 6.00 g of the food product, adding 40 mL distilled/deionized water, and heating at 65 degrees C for 30 min. Afterwards, 10 mL ethylene dichloride was added and the mixture was homogenized for 30 s and centrifuged at 2700 x g for 30 min, and then 8 g supernatant was extracted with 10, 5, and 5 mL portions of ethyl acetate. The extracts were combined, dried with sodium sulfate, and concentrated to 100-200 microL. Acrylamide was determined by analysis of the final extract on a single quadrupole, bench-top mass spectrometer with electrospray ionization, using a 2 mm id C18 column and monitoring m/z = 72 (acrylamide) and m/z = 73 (internal standard). For difficult food matrixes, such as coffee and cocoa, a solid-phase extraction cleanup step was incorporated to improve both chromatography and column lifetime. The method had a limit of quantitation of 10 ppb, and coefficients of determination (r2) for calibration curves were typically better than 0.998. Acceptable spike recovery results were achieved in 11 different food matrixes. Precision in potato chip analyses was 5-8% (relative standard deviation). This method provides an LC/MS alternative to the current LC/MS/MS methods and derivatization gas chromatography/mass spectrometry methods, and is applicable to difficult food products such as coffee, cocoa, and high-salt foods.

Transcatheter closure of an atrial septal defect in a dog.

Atrial septal defect, while rare in dogs, can result in severe clinical signs. Surgical correction of atrial septal defect requires open-heart surgery. Transcatheter closure techniques provide minimally invasive surgical alternatives.

Acrylamide formation mechanism in heated foods.

Recent findings of a potential human carcinogen, acrylamide, in foods have focused research on the possible mechanisms of formation. We present a mechanism for the formation of acrylamide from the reaction of the amino acid asparagine and a carbonyl-containing compound at typical cooking temperatures. The mechanism involves formation of a Schiff base followed by decarboxylation and elimination of either ammonia or a substituted imine under heat to yield acrylamide. Isotope substitution studies and mass spectrometric analysis of heated model systems confirm the presence of key reaction intermediates. Further confirmation of this mechanism is accomplished through selective removal of asparagine with asparaginase that results in a reduced level of acrylamide in a selected heated food.

Cardioversion of atrial fibrillation in a dog with structural heart disease using an esophageal-right atrial lead configuration.

Atrial fibrillation is a common arrhythmia in dogs with structural cardiac disease and can result in significant clinical signs. Several methods of electrical cardioversion of atrial fibrillation have been described. Biphasic transthoracic cardioversion of atrial fibrillation in dogs with naturally occurring heart disease has been described in veterinary medicine and has been shown to be highly successful. In humans and research animals intracardiac and transesophageal cardioversion of atrial fibrillation has been described as an alternative to transthoracic cardioversion. While transesophageal cardioversion is very successful in humans and research animals, this technique has not been previously described in a clinical patient with naturally occurring heart disease in veterinary medicine. This report describes the use of transesophageal cardioversion in a dog with atrial fibrillation and structural cardiac disease. Cardioversion was unsuccessful using two electrodes positioned within the esophagus. Cardioversion of atrial fibrillation to normal sinus rhythm was successfully achieved and maintained using one electrode positioned within the esophagus and one electrode positioned within the right atrium using a synchronized monophasic shock of 50 J.

Efficacy of two commercially available cardiac pacing catheters for transesophageal atrial pacing in dogs.

OBJECTIVE: Compare the efficacy of two cardiac pacing catheters for transesophageal atrial pacing (TAP). ANIMALS: Ten healthy dogs. METHODS: Transesophageal atrial pacing was attempted in left lateral recumbency under general anesthesia. In series, a curved electrophysiologic (EP) catheter and a straight transesophageal pacing (TP) catheter were passed transorally into the distal esophagus, caudal to the heart. Each catheter was slowly withdrawn until pacing was initiated. The catheter continued to be withdrawn in 5 mm increments until capture was no longer achieved at maximal pacing setting creating a total zone of capture (tZOC). Minimum pacing threshold (Th(min)) and degree of extraneous muscle stimulation (EMS) were determined at each site. RESULTS: The EP catheter achieved TAP in 10/10 dogs with a Th(min) of 8.8 ± 4.8 mA and tZOC of 4.0 ± 1.7 cm. The TP catheter achieved TAP in 7/10 dogs with a Th(min) of 22.5 ± 5.6 mA and tZOC of 1.2 ± 1.6 cm. No EMS was noted during TAP at Th(min) using the EP catheter. Of the 7 dogs in which TAP was successful, 3/7 experienced considerable EMS at Th(min). There was no significant relationship between patient body weight and Th(min) with either catheter (EP catheter P = 0.09; TP catheter P = 0.81). CONCLUSIONS: The electrophysiology catheter captured the atria of more dogs over a larger area without EMS as compared to the TP catheter. The electrophysiology catheter is recommended for transesophageal atrial pacing in dogs.

Use of transesophageal atrial pacing to provide temporary chronotropic support in a dog undergoing permanent pacemaker implantation.

A 14.5-kg, 13-year-old female spayed Cocker spaniel was evaluated because of episodic hind limb weakness. Results of examination were consistent with sick sinus syndrome with intermittent second-degree atrioventricular block. Transesophageal atrial pacing was successful in providing chronotropic support during permanent pacemaker implantation. Transesophageal atrial pacing appears to be a viable option for temporary atrial pacing in dogs with hemodynamically marked bradycardia without significant atrioventricular blockade.

Efficacy of transesophageal and transgastric cardiac pacing in the dog.

OBJECTIVES: Determine if temporary artificial cardiac pacing can be accomplished from transesophageal or transgastric pacing sites. ANIMALS, MATERIALS AND METHODS: Nine purpose bred Beagle dogs had a multipolar electrophysiology pacing catheter inserted transnasally and advanced into the distal esophagus or stomach under general anesthesia. Artificial atrial pacing was attempted using a bipolar configuration from the distal esophagus with the dogs in left lateral recumbency. Artificial ventricular pacing was attempted from the distal esophagus and stomach using unipolar and bipolar configurations with the dogs in multiple positions. RESULTS: Transesophageal atrial pacing was accomplished in all dogs with a mean threshold of 10.5 mA (+ or - 3.9) and a 15 mm polar separation with no skeletal muscle stimulation. All attempts at transgastric and transesophageal ventricular pacing were unsuccessful. CONCLUSIONS: Transesophageal atrial pacing using standard cardiac pacing equipment is simple to perform and is a viable alternative to temporary transvenous or transthoracic pacing for supraventricular bradyarrhythmias without atrioventricular conduction disturbances. Transesophageal and transgastric ventricular pacing does not appear possible using the pacing configurations in this study.