Development and assessment of a novel precordial lead system for accurate detection of right atrial and ventricular depolarization in dogs with various thoracic conformations

Morphology of the aortic arch branching pattern in raccoon dogs (Nyctereutes procyonoides, Gray, 1834)

BACKGROUND

Aortic arch (AA) branching patterns vary among different mammalian species. Most previous studies have focused on dogs, whereas those on raccoon dogs remain unexplored.

OBJECTIVES

The objective of this study was to describe the AA branching pattern in raccoon dogs and compare their morphological features with those of other carnivores.

METHODS

We prepared silicone cast specimens from a total of 36 raccoon dog carcasses via retrograde injection through the abdominal aorta. The brachiocephalic trunk (BCT) branching patterns were classified based on the relationship between the left and right common carotid arteries. The subclavian artery (SB) branching pattern was examined based on the order of the four major branches: the vertebral artery (VT), costocervical trunk (CCT), superficial cervical artery (SC), and internal thoracic artery (IT).

RESULTS

In most cases (88.6%), the BCT branched off from the left common carotid artery and terminated in the right common carotid and right subclavian arteries. In the remaining cases (11.4%), the BCT formed a bicarotid trunk. The SB exhibited various branching patterns, with 26 observed types. Based on the branching order of the four major branches, we identified the main branching pattern, in which the VT branched first (98.6%), the CCT branched second (81.9%), the SC branched third (62.5%), and the IT branched fourth (52.8%).

CONCLUSIONS

The AA branching pattern in raccoon dogs exhibited various branching patterns with both similarities and differences compared to other carnivores.

Comparison of the effects of propofol and alfaxalone on the electrocardiogram of dogs, with particular reference to QT interval

Cardiac electrical activity is often altered by administration of anesthetic drugs. While the effects of propofol in this regard have previously been described in dogs, to date, there are no reports of the effect of alfaxalone. This study investigated the impact of both propofol and alfaxalone on the ECG of 60 dogs, after premedication with acepromazine and methadone. Heart rate increased significantly in both groups. The PR and QRS intervals were significantly increased following propofol while with alfaxalone the QRS duration was significantly increased and ST segment depression was observed. The QT and JT interval were significantly shorter following induction with alfaxalone, but, when corrected (c) for heart rate, QTc and JTc in both groups were significantly greater following induction. When comparing the magnitude of change between groups, the change in RR interval was greater in the alfaxalone group. The change in both QT and JT intervals were significantly greater following alfaxalone, but when QTc and JTc intervals were compared, there were no significant differences between the two drugs. The similarly increased QTc produced by both drugs may suggest comparable proarrhythmic effects.

Localization and characterization of atrial depolarization waves on the surface electrocardiogram in dogs with rapid supraventricular tachycardia

BACKGROUND

Supraventricular tachycardias (SVTs), despite having various anatomical substrates and pathophysiological mechanisms, frequently show similar electrocardiographic presentations.

OBJECTIVES

To locate and characterize atrial deflections (ADs) on 12-lead electrocardiograms in dogs with sustained rapid SVT and assess the utility of different electrocardiographic variables in differentiating types of tachycardia.

ANIMALS

Ninety-two dogs with orthodromic atrioventricular reciprocating tachycardia, 17 with atrial flutter, 33 with focal atrial tachycardia recorded and confirmed by electrophysiological study, and 40 dogs with sinus tachycardia.

METHODS

Atrial deflection position on the 12-lead surface electrocardiogram was assessed according to the sequence of intracardiac activation. Its features were evaluated together with the relationship between AD and QRS complex interval (AD-R) and QRS complex and AD interval (R-AD).

RESULTS

Orthodromic atrioventricular reciprocating tachycardia was characterized by an AD-AD interval of 213 ± 30 ms, mean electrical axis (MEA) of AD of -90 (-90/-78)°, R-AD interval of 75 (65-80) ms, and R-AD/AD-R of 0.54 (0.45-0.64). Atrial flutter was characterized by an AD-AD interval of 199 ± 57 ms, MEA of 76° (72/81), R-AD of 120 (72-144) ms, and R-AD/AD-R of 0.81 (0.63-1.13). Focal atrial tachycardia was characterized by an AD-AD interval of 270 ± 38 ms, MEA of 49 (-72/76)°, R-AD of 160 (120-200) ms, and R-AD/AD-R of 1.45 (0.92-1.67). Sinus tachycardia was characterized by an AD-AD interval of 292 ± 31 ms, MEA of 66° (52/73), R-AD of 215 (192-222) ms, and R-AD/AD-R of 2.68 (2.25-3.08).

CONCLUSIONS AND CLINICAL IMPORTANCE

Analyzing AD on 12-lead electrocardiogram is helpful in differentiating the most common SVTs in dogs.

Electrocardiographic patterns of ventricular pre-excitation in dogs with right-sided accessory pathways

INTRODUCTION

The aim of the study was to describe the electrocardiographic features of ventricular pre-excitation (VPE) patterns characterized by the presence of delta (δ) wave, short P-δQRS interval, wide δQRS complexes in dogs with right-sided accessory pathways.

ANIMALS, MATERIALS AND METHODS

Twenty-six dogs with a confirmed accessory pathways (AP) via electrophysiological mapping were included. All dogs underwent a complete physical examination, 12-lead ECG, thoracic radiography, echocardiographic examination and electrophysiologic mapping. The AP were located in the following regions: right anterior, right posteroseptal, right posterior. The following parameters were determined: P-δQRS interval, δQRS duration, δQRS axis, δQRS morphology, δ-wave polarity, Q-wave, R-wave, R'-wave, S-wave amplitude, and R/S ratio.

RESULTS

In lead II, the median δQRS complex duration was 82.4 (IQR 7.2) and the median P-δQRS interval duration was 54.6 (IQR 4.2) msec. The median δQRS complex axis in the frontal plane was: + 68° (IQR 52.5) for right anterior APs, - 24 ° (IQR 24) for right postero-septal APs, - 43.5 ° (IQR 27.25) for right posterior APs (P = 0.007). In lead II, the polarity of the δ wave was positive in 5/5 right anterior APs and negative in 7/11 postero-septal APs and 8/10 in right posterior APs. In precordial leads of all dogs, R/S was ≤ 1 in V1 and > 1 in all leads from V2 to V6.

CONCLUSION

Surface electrocardiogram can be used to distinguish right anterior APs from right posterior and right postero-septal ahead of an invasive electrophysiological study.

Investigation of the cardiac effects of exercise testing on apparently healthy Boxer dogs

BACKGROUND

Holter electrocardiographic monitoring is a cornerstone of diagnostic testing for arrhythmogenic cardiomyopathy (ACM) in Boxer dogs, but physical activity during monitoring is not controlled. In humans, exercise testing (ExT) can identify latent tachyarrhythmias associated with cardiomyopathy, and exercise increases serum cardiac troponin-I concentrations ([hs-cTnI]). These effects have not yet been investigated in Boxer dogs.

HYPOTHESIS/OBJECTIVES

Subjecting Boxer dogs to brief, moderate-intensity ExT can identify changes in Holter recordings and [hs-cTnI] compared to baseline results.

ANIMALS

Thirty overtly healthy, client-owned Boxer dogs.

METHODS

Prospective interventional study. Dogs underwent baseline diagnostic testing including 24-hour Holter monitoring and [hs-cTnI], followed by brief ExT (accompanied, brisk stair-climbing and -descending for <5 minutes).

RESULTS

Eleven dogs (37%) had >100 premature ventricular complexes (PVCs)/24 hours at baseline (3), ExT (3), or both (5). After ExT, these dogs had more PVCs/24 hours and greater increases in [hs-cTnI] compared to those with ≤100 PVCs/24 hours. Dogs with the striatin mutation had more PVCs/24 hours and a greater increase in [hs-cTnI] after ExT than did dogs without the striatin mutation.

CONCLUSIONS AND CLINICAL IMPORTANCE

Exercise testing may improve the binary classification of Boxer dogs with or without ACM by increasing the number of PVCs and [hs-cTnI] in affected dogs to a greater degree than in unaffected dogs. This effect also is associated with presence or absence of the striatin mutation. Exercise should be a controlled variable when screening Boxer dogs for ACM.

Electrocardiographic Findings and Cardiac Troponin I Assay in Dogs with SIRS Diagnosis

Several studies performed in humans have demonstrated that the onset of systemic inflammatory response syndrome (SIRS) represents a high risk condition to develop myocardial damage and arrhythmias. Therefore, we also hypothesized cardiac involment for dogs affected by SIRS. To assess this hypothesis, 24 dogs with a diagnosis of SIRS (13 entire males, 7 entire females, and 4 spayed females) with an age ranging from 4 to 11 years (mean 5.6 years) and an average weight of 24 kg (range from 5 to 47 kg) were enrolled. The dogs were divided into two groups according to their prognosis: Survivors (G1) and not survivors (G2), composed by 13 and 11 dogs, respectively. Moreover, healthy dogs were included as the control group (CTR). All the dogs with a history of cardiac or renal disease were excluded. At the inclusion, each patient underwent a physical examination and a complete cell count, and a biochemistry panel (including electrolyte profile) was performed; moreover, the blood cardiac Troponin I (cTnI) was measured. For each clinical variable indicative of SIRS, a score between 0 (absence) and 1 (presence) was applied. Furthermore, an electrocardiographic examination was recorded. Seventeen out of 24 (70.8%) dogs with SIRS showed arrhythmias, of which n. 6 belonged to the G1, while n. 11 belonged to the G2. Most represented findings were sinus tachycardia (7/17; 41.1%), followed by monomorphic premature ventricular beats (6/17; 35.3%), less common were first-degree atrioventricular block (2/17; 11.7%) and sinus bradycardia 1/17; 5.8%). Notably, in G1 dogs, only sinus tachycardia and premature ventricular beats were observed. G2 dogs presented a number of total and banded leukocytes significantly higher than those of G1 (p = 0.002 and 0.049), in the same manner, the clinical score suggestive of SIRS (3 vs. 2.1) was significantly higher in G2 than in G1 dogs (p = 0.01). Moreover, a significantly higher value of cTnI was observed in the G2 group compared to the G1 group (p = 0.006). Data presented here suggested a cardiac involvement in dogs with SIRS, analogously to humans, that may significantly influence the patient's prognosis.

Comparative analysis of ECG records depending on body position in domestic swine (Sus scrofa domestica)

Background

Electrocardiography is a method widely applied in diagnosing abnormalities in the functioning of the heart muscle in veterinary medicine. It is a non-invasive and easy to perform test helpful in the general examination and a widely used patient monitoring method during anesthesia. Since the 1980s, pigs have become more and more popular companion animals. Moreover, the pig is a widely used model animal in biomedical research. Therefore, there is need to provide them with higher-quality veterinary services, also in emergency situations. It creates new challenges for veterinarians and the need to expand their knowledge of pigs’ treatment as pets. The aim of the planned experiment was to compare the ECG recordings made with two different body positions and determine if any differences occurred. Standard ECG in swine is performed under general anesthesia in the lying position on the left side, for this position of the body have been developed and reported standards in the literature. However, some procedures performed on swine require a different body position, for which there is less data in the literature.

Methods

The study was carried out on 29 Polish landrace pigs weighing in the range of 33–44 kg. The tests were performed under general anesthesia with the same protocol for each animal, placing the animals first lying down on their right side, and then on their backs. The anesthesia protocol included medetomidine, midazolam, ketamine, and propofol. During the examination, ECG records were performed and analyzed in a 12-lead system with software support.

Results

The results show significant differences in electrocardiogram recordings depending on the animal's body position. Those differences mainly concern the amplitude of the P wave and R wave in the recordings and are even more visible comparing the electrocardiograms of the same specimen. There are also some significant differences in the duration of intervals. Based on the obtained results, reference ranges for the right lateral and dorsal positions were developed.

Conclusion

In conclusion, the body position has a significant impact on the ECG recording in swine, therefore performing this examination, chosen normative value tables should be compatible with the position of the examined animal.

Evaluation of a Novel Precordial Lead System for the Electrocardiographic Diagnosis of Right Ventricular Enlargement in Dogs

The purpose of this study was to evaluate the reliability of precordial leads for the detection of right ventricular enlargement (RVE) in dogs. This was a prospective observational study. The RVE was defined by echocardiography. The amplitude (mV) of the Q, R, and S waves, the R/S ratio, and the mean electrical axis (MEA) of the QRS complex were assessed on the 12-lead ECG. The ROC curve and the Youden index yielded the best cutoffs for RVE detection. An area under the curve (AUC) > 0.7 defined suitable diagnostic accuracy. A total of 84 dogs, 27 with RVE and 57 healthy controls, were enrolled. Q wave amplitude in aVR (cutoff > 0.10 mV; AUC = 0.727), R/S ratio in V4 (cutoff < 1.15; AUC = 0.842), R/S ratio in V5 (cutoff < 1.95; AUC = 0.839) and S wave amplitude in V6 (cutoff > 0.70 mV; AUC = 0.703) showed suitable diagnostic accuracy in detecting RVE. Among dogs with RVE, only 9/27 (33%) presented a right shift of MEA. Differently, 19/27 (70%) showed at least one of the identified precordial lead criteria. Assessment of the R/S ratio in V4 and V5 and S wave amplitude in V6 increases the diagnostic accuracy of ECG in distinguishing between dogs with RVE and healthy dogs.

Left Atrial Tachycardia and Third-Degree Atrioventricular Block in a Dog

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SVT may affect only the LA in the dog.

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Spectral and 2D Doppler echocardiography help confirm that an SVT is confined to the LA.

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Left atrial SVT was identified by comparing MV and TV inflows via spectral Doppler.

Feasibility of electroanatomic mapping and radiofrequency catheter ablation in Boxer dogs with symptomatic ventricular tachycardia

Background

Treatment for Boxers with ventricular tachycardia (VT) is limited. Electroanatomic mapping (EAM) facilitates identification of arrhythmogenic substrate for radiofrequency catheter ablation (RFCA).

Objective

Describe the use of EAM to guide RFCA in Boxers with VT.

Animals

Five client‐owned Boxers with symptomatic VT or persistent VT despite antiarrhythmic medications.

Methods

Case series evaluating clinical, EAM, and before and after RFCA Holter data.

Results

Sustained VT was inducible in 3 dogs, but required aggressive stimulation protocols. Low‐voltage areas consistent with electroanatomic scar were found in 2 dogs, located at the right ventricular (RV) outflow tract and cranial RV. Two dogs had a focal activation pattern of VT and 1 dog had a reentrant mechanism. After RFCA, all dogs no longer collapsed and had fewer runs of VT, 3 of which had 0 runs of VT. Number of ventricular premature beats increased in 3 dogs and decreased in 2 dogs, 1 of which had nearly complete resolution of all arrhythmias. Procedural complications included ventricular fibrillation (n = 2) with successful defibrillation, bruising or hemorrhage at the vascular access site (n = 4), retroperitoneal hemorrhage (n = 1), aortic and mitral regurgitation (n = 1), onset of frequent supraventricular tachycardia (n = 1), and persistent right pelvic limb lameness (n = 1).

Conclusions and Clinical Importance

Electroanatomic mapping and RFCA are feasible in Boxers with VT. Based on this small cohort, RFCA may help decrease runs of VT and improve clinical signs. The anatomic substrate and electrophysiologic mechanisms are variable and require further study.

Echocardiographic parameters and indices in 23 healthy Maltese dogs

BACKGROUND

Echocardiography is a primary tool used by veterinarians to evaluate heart diseases. In recent years, various studies have targeted standard echocardiographic values for different breeds. Reference data are currently lacking in Maltese dogs and it is important to fill this gap as this breed is predisposed to myxomatous mitral valve disease, which is a volume overload disease.

OBJECTIVES

To establish the normal echocardiographic parameters for Maltese dogs.

METHODS

In total, 23 healthy Maltese dogs were involved in this study. Blood pressure measurements, thoracic radiography, and complete transthoracic echocardiography were performed. The effects of body weight, age and sex were evaluated, and the correlations between weight and linear and volumetric dimensions were calculated by regression analysis.

RESULTS

The mean vertebral heart size was 9.1 ± 0.4. Aside from the ejection fraction, fractional shortening, and the left atrial to aorta root ratio, all the other echocardiographic parameters were significantly correlated with weight.

CONCLUSION

This study describes normal echocardiographic parameters that may be useful in the echocardiographic evaluation of Maltese dogs.

Radiofrequency catheter ablation of cranial vena cava flutter in four dogs

Four dogs were referred to our institution for incessant supraventricular tachycardias causing weakness; congestive heart failure was present in one dog. At admission, all dogs had a surface electrocardiogram showing a narrow QRS complex tachycardia with a ventricular rate ranging from 80 to 300 bpm, variable atrioventricular conduction ratio from 1:1 to 3:1, and positive atrial depolarizations in inferior leads (II, II, III, and aVF), with isoelectric lines between them. Three of four dogs had a dilated cardiomyopathy phenotype; one dog had a heart base tumor involving the cranial vena cava wall. According to the electrocardiographic findings, a presumptive diagnosis of reverse typical or atypical atrial flutter was considered, and endocardial mapping was planned for each dog. During the electrophysiologic study, continuous atrial activation compatible with atypical atrial flutter was observed in all dogs, with concealed entrainment obtained at the level of the isthmus located at the distal portion of the cranial vena cava, close to the entrance into the right atrium. A linear radiofrequency catheter ablation was performed from the right atrial wall to the distal part of the cranial vena cava with a permanent interruption of the isthmic conduction in all dogs at a 6-month follow-up.

Segmental septal dyskinesia associated with an accessory pathway and preexcitation in two Golden Retriever dogs

Ventricular preexcitation secondary to anterograde conduction through an accessory pathway was diagnosed in two Golden Retriever dogs. Both dogs demonstrated similar segmental myocardial thinning and systolic dyskinesia of the basal interventricular wall on echocardiography. These changes are widely recognised in people with ventricular preexcitation but have not been previously described in dogs. Ventricular preexcitation should be considered as a potential cause for segmental wall motion abnormalities in these two dogs.

P-Wave Terminal Force in Dogs With Myxomatous Mitral Valve Disease

P-wave terminal force (PTF) is accepted as an electrocardiographic criteria to assess left atrial abnormalities in humans. In this study, the applicability of PTF in dogs with myxomatous mitral valve disease (MMVD) was evaluated, and compared its ability to identify left atrial dilatation with 4 other P-wave derived parameters. Seventy-four dogs with echocardiographically diagnosed MMVD were recruited for this prospective cross-sectional study. Also, 47 healthy dogs were included to serve as controls. All dogs underwent physical, electrocardiographic and standard echocardiographic examinations prior to enrollment. Electrocardiographic measurements were obtained from simultaneous recordings at three different locations for precordial lead V₁. PTF was defined as the deflection following the second half of the P-wave, and was best documented at the first and third right intercostal spaces. In those locations, the P-wave was negative and P-wave terminal force was recognized as a positive undulation in baseline following P-wave. P-wave terminal force and P-wave duration measured from recordings obtained at either the first or third right intercostal spaces had poor to weak correlations (P < .05) with echocardiographic surrogates of cardiac remodeling and congestion. In dogs with MMVD, only P-wave duration and P-wave area distinguished normal and dilated left atria (P < .05). In conclusion, PTF had positive polarity and was best recorded when precordial lead V₁ electrode was placed at the most cranial right intercostal locations. PTF failed to reliably identify left atrial enlargement in dogs with MMVD.

R-peak time in clinically healthy dogs with different thoracic conformations

R-peak time (RPT) is an electrocardiographic parameter that represents the time taken for electrical activation to spread from the endocardium to the epicardium. In human medicine, right ventricular RPT is measured from lead V₁ to lead V₂, and left ventricular RPT from lead V₅ to lead V₆. The aim of the present study was to define RPT duration in a group of clinically healthy dogs with different thoracic conformations. Sixty clinically healthy dogs underwent a 12-lead electrocardiogram recorded using a previously described precordial system. The dogs were allocated into three morphologic groups. In the brachymorphic group, the median and 25th-75th percentiles for RPT in V₁ were 10.5 ms (10-12 ms); V₂, 18 ms (16.5-20 ms); V₃, 19 ms (18-22 ms); V₄, 20 ms (17-23.5 ms); V₅, 21 ms (18.5-24 ms); and V₆: 22 ms (18.5-25.5 ms). In the mesomorphic group, RPT in V₁ was 16 ms (14-18 ms); V₂, 22 ms (20-24 ms); V₃, 23 ms (21-25 ms); V₄, 23 ms (22-25 ms); V₅, 25 ms (23-27 ms); and V₆, 28 ms (25-30 ms). In the dolichomorphic group, RPT in V₁ was 15 ms (13-17 ms); V₂, 29 ms (26-32.5 ms); V₃, 30 ms (27-33.5 ms); V₄, 29.5 ms (26-35 ms); V₅, 30 ms (28-34 ms); and V₆, 31.5 ms (28-35 ms). RPT in V₁ was significantly shorter than RPT in V₂ to V₆ in all morphotypes (P < 0.05). In all precordial leads, RPT was significantly different between morphotypes (P < 0.05). These results are in agreement with previous findings in humans and with the observation that V₁ reads the right ventricle and V₂ to V₆ read the left ventricle. These preliminary data provide RPT ranges in clinically healthy dogs of different morphotypes.