A study of the inter- and intra-operator variability on selected echocardiographic measurements in dogs.

Standard transthoracic echocardiography is considered the non-invasive gold standard for the diagnosis of most cardiac diseases. Defining reproducibility, repeatability, and reliability of this exam is imperative to reduce errors in clinical evaluations. The present study aimed at: (1) evaluating the reproducibility and repeatability of 15 echocardiographic parameters in dogs by analyzing measurements obtained from several operators with different levels of experience and comparing them to the ones obtained from two board-certified operators (gold standards - GSs); (2) assessing whether different formative paths have an influence on the variability of the echocardiographic measurements. Fifty-one operators have been included in this study, along with two diplomates of the European College of Veterinary Internal Medicine - Cardiology. Ten dogs were enrolled, 5 Golden Retrievers and 5 Cavalier King Charles Spaniels. Echocardiographic examination was performed on each dog by one GS and several operators on the same day. Results show the highest deviation from the GS and a poor inter-operator reproducibility for the M-mode measurements of the interventricular septum and the left ventricular free wall. Differently, M-mode-obtained internal diameters of the left ventricle in systole and diastole, and measurements of the aortic annulus and root show moderate to excellent intra- and inter-operator reliability and a good concordance with the GSs, demonstrating that all the operators correctly assess left ventricular systolic function and dilation, and evaluate the aortic valve. Furthermore, a specialist clinical activity, more than the acquired theoretical knowledge, affects the reliability of the echocardiographic examination by reducing the difference from the GS' measurements.

Immunofluorescent Localization of Plakoglobin Is Altered in Endomyocardial Biopsy Samples from Dogs with Clinically Relevant Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC).

Diagnosing the early stages of canine Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is complicated by day-to-day arrhythmia variability, and absence of reliable, transthoracic echocardiographic features. Definitive diagnosis requires histopathologic identification of transmural fibrofatty replacement of the right ventricle. Reduction of immunofluorescent signal for plakoglobin (PG) at the intercalated disc (ID) is reported in ARVC-affected humans and boxers. Our objective was to determine whether reduced immunofluorescent signal for PG in endomyocardial biopsy samples (EMBs) correspond with a histopathologic diagnosis of ARVC. Here, 49 dogs were evaluated: 43 with advanced cardiac disease and 6 non-clinical boxers with mild to moderate ventricular arrhythmia (VA) burden. EMBs were obtained from all dogs; samples were prepared with antibodies recognizing cadherin (PC) and PG and evaluated with confocal microscopy. Investigators were blinded to breed and clinical status. ARVC was histopathologically diagnosed in 8 out of 49 dogs. Of these, three out of eight had clinical signs consistent with ARVC (two boxers, one English bulldog) and reduced PG signal at ID; five out of eight were non-clinical boxers with moderate VA and no reduction in PG. A total of 41 out of 49 dogs were histopathologically diagnosed with non-ARVC cardiac disease; 1 out of 41 showed reduction of PG at ID, while 40 out of 41 had no PG reduction. These results suggest that EMB PG signal is reduced in dogs with advanced ARVC, but not in the occult phase of the disease. Additionally, presence of PG at ID supports a diagnosis of non-ARVC cardiac disease in dogs with clinical signs. These results may offer an additional test that helps differentiate advanced ARVC from other myocardial diseases.

Evaluation of the diagnostic value of an implantable loop recorder in dogs with unexplained syncope.

OBJECTIVE: To evaluate the diagnostic value of an implantable loop recorder (ILR) in dogs with unexplained syncope. DESIGN: Prospective case series. ANIMALS: 12 dogs with recurrent unexplained syncope. PROCEDURES: An ILR was surgically inserted in a pocket created in the subcutaneous tissues of the left hemithorax of each dog. The ILRs were programmed for manual and automatic activation, and event analysis and programming were performed at 3-month intervals and after each syncopal episode. RESULTS: The ILR was manually activated in 7 of 12 dogs at least once within 45 to 218 days (median, 120 days) after implantation. Four dogs had syncopal episodes associated with sinus tachycardia followed by sinus bradycardia and asystolic pauses. Two dogs had ventricular tachycardia, and 1 dog had sinus node dysfunction with prolonged sinus arrest that coincided with loss of consciousness and falling. Four dogs had no additional syncopal episodes after implantation of the ILR. In the remaining dog, the owner was unable to activate the ILR during the only syncopal episode observed for that dog after ILR implantation. In all 12 dogs, analysis of ECG traces after automatic activation of recording revealed normal cardiac rhythms. CONCLUSIONS AND CLINICAL RELEVANCE: Data gained after manual activation of an ILR provided valuable diagnostic and prognostic information in almost all dogs with unexplained syncopal episodes by confirming or disproving an association between syncope and arrhythmias. However, detection of disturbances in cardiac rhythm after automatic activation did not appear to improve the diagnostic value for an ILR implanted in dogs.

Temporal changes in clinical and radiographic variables in dogs with preclinical myxomatous mitral valve disease: The EPIC study.

BACKGROUND: The Evaluation of pimobendan in dogs with cardiomegaly caused by preclinical myxomatous mitral valve disease (EPIC) study monitored dogs with myxomatous mitral valve disease (MMVD) as they developed congestive heart failure (CHF). OBJECTIVES: To describe the changes in clinical and radiographic variables occurring as dogs with MMVD and cardiomegaly develop CHF, compared to similar dogs that do not develop CHF. ANIMALS: One hundred and thirty-five, and 73 dogs that did or did not develop CHF, respectively. MATERIALS AND METHODS: The following variables were evaluated in 2 groups of dogs (dogs that did or did not develop CHF): Heart rate (HR), clinic respiratory rate (RR), home-measured resting respiratory rate (RRR), rectal temperature (RT), body weight (BW), and vertebral heart sum (VHS). Absolute value and rate of change of each variable were calculated for each day a dog was in study. Daily means were calculated and plotted against time. The onset of CHF or last visit before leaving the study were set as reference time points. RESULTS: The most extreme values and rate of change occurred in variables immediately before onset of CHF. Vertebral heart sum increased earliest. Heart rate, RR, and RRR also increased. Rectal temperature and BW decreased. Increases in RR and RRR were most extreme and occurred immediately before CHF. CONCLUSIONS AND CLINICAL IMPORTANCE: Dogs with MMVD and cardiomegaly experience increases in HR, RR, RRR, and VHS, and decreases in BW and RT as they develop CHF. The variables with highest absolute change and rate of change were RR and RRR. These findings reinforce the value of RR and RRR as indicators of impending or incipient CHF.

Evaluation of the presence of selected viral and bacterial nucleic acids in pericardial samples from dogs with or without idiopathic pericardial effusion.

Many viruses have been identified in pericardial fluid and in tissue samples from humans with pericarditis by means of molecular diagnostics. In canine idiopathic pericardial effusion there is as yet no conclusive evidence to support the involvement of an infectious agent. This study was designed to investigate a possible relationship between idiopathic pericardial effusion in dogs and viruses most commonly encountered in humans affected with viral pericarditis. Coxsackievirus B3 RNA, influenza virus type A RNA, human adenovirus type 2 DNA, human cytomegalovirus DNA, and parvovirus B19 DNA were investigated using PCR on pericardial effusion samples and pericardial tissue specimens collected from 14 dogs with idiopathic pericardial effusion. PCR was also used to test for two bacteria, Borrelia burgdorferi and Chlamydia pneumoniae. The same microorganisms were also looked for in pericardial effusions or pericardial washes from 10 dogs with neoplastic pericardial effusion, and in samples collected from 10 dogs which died of a non-cardiac disease. One pericardial effusion sample from a dog with the idiopathic form of the disease tested positive for influenza virus type A and sequencing of the amplicon confirmed the PCR result. In another dog from the same group a cytomegalovirus was detected by PCR in the effusion, but sequencing showed this to be a false-positive result. The genomes of the microorganisms investigated were not detected in neoplastic effusions or pericardial washes. The results indicate that viral and bacterial DNA/RNA of relevance for human pericarditis is rare in pericardial samples from dogs with idiopathic pericardial effusion. The finding of influenza type A viral RNA in pericardial fluid from one dog with the idiopathic form of the disease warrants further investigation.

Prevalence of selected cardiotropic pathogens in the myocardium of adult dogs with unexplained myocardial and rhythm disorders or with congenital heart disease.

OBJECTIVE: To determine the prevalence of nucleic acid from selected cardiotropic pathogens in endomyocardial biopsy samples from dogs with unexplained myocardial and rhythm disorders (UMRD) and compare prevalence with that for a group of control dogs with congenital heart disease (CHD). ANIMALS: 47 client-owned dogs. PROCEDURES: Right ventricular endomyocardial biopsy was performed in dogs with UMRD (dilated cardiomyopathy [n = 25], atrioventricular block [6], and nonfamilial ventricular [4] and supraventricular arrhythmias [2]) or CHD (10) that required right ventricular catheterization. Biopsy samples were evaluated histologically, and PCR assays were used for detection of nucleic acid from 12 pathogens. RESULTS: 197 biopsy samples were collected from dogs with UMRD (n = 172) or CHD (25). At least 1 pathogen was detected in 21 of 37 (57%; 95% confidence interval [CI], 41% to 71%) dogs with UMRD, and canine coronavirus was detected in 1 of 10 (10%; 95% CI, 2% to 40%) dogs with CHD. Dogs with UMRD were significantly more likely than dogs with CHD to have pathogens detected in biopsy samples (OR, 11.8; 95% CI, 1.3 to 103.0). The most common pathogens in dogs with UMRD were canine distemper virus, canine coronavirus, canine parvovirus 2, and Bartonella spp. No pathogens were detected in available blood samples from dogs with pathogens detected in biopsy samples. CONCLUSIONS AND CLINICAL RELEVANCE: Detection of nucleic acids from selected cardiotropic pathogens in myocardial tissue from dogs with UMRD suggested a possible association between the 2. Further studies are needed to explore whether this association is causative or clinically important. (J Am Vet Med Assoc 2019;255:1150-1160).

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

OBJECTIVE: To assess recording accuracy of right atrial and ventricular depolarization during 12-lead ECG when precordial lead V1 was positioned at each of 5 locations on the thorax of dogs with various thoracic conformations. ANIMALS: 60 healthy client-owned dogs. PROCEDURES: 20 dogs were allocated to each of 3 groups (brachymorphic, mesomorphic, or dolichomorphic) on the basis of thoracic conformation. Each dog remained unsedated and was positioned in right lateral recumbency for a series of five 12-lead surface ECGs, with V1 located adjacent to the sternum in the fifth intercostal space (ICS; control), at the costochondral junction (CCJ) of the right first ICS (1st-R), at the CCJ of the right third ICS, at the right third ICS where the thorax was the widest, and at the CCJ of the left first ICS. Electrocardiographic variables were compared among the 5 ECG tracings. RESULTS: When V1 was at the control location, the P wave was positive for all dogs; however, consistent recording of right atrial and ventricular depolarization (ie, R wave-to-S wave ratio [R/S] < 1) occurred more frequently for brachymorphic dogs (16/20) than for dolichomorphic (7/20) and mesomorphic (6/20) dogs. When V1 was at the 1st-R location, the P wave was negative for most dogs, and R/S was < 1 for the majority of dogs in the brachymorphic (19/20), mesomorphic (17/20), and dolichomorphic (16/20) groups. The median R/S for V1 at the 1st-R location was significantly lower than that for the other 4 V1 locations. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that placement of V1 at the 1st-R location provided correct evaluation of right atrial and ventricular depolarization in most dogs regardless of thoracic conformation.

Clinical and electrocardiographic presentations of transient trifascicular block in three cats.

This report describes transient trifascicular block in three cats presented with lethargy and inappetence, and elevated cardiac troponin I concentrations. The electrocardiogram (ECG) of cat 1 showed a sinus rhythm with pronounced first-degree atrioventricular (AV) block, right bundle branch block, and left anterior fascicular block. The ECG of cat 2 showed truncular left bundle branch block alternating with left anterior fascicular block coupled with prolonged PR intervals, second-degree heart block, and paroxysmal third-degree AV block. The ECG of cat 3 showed first-degree AV block with concomitant right bundle branch block. The diagnosis of trifascicular block was made when paroxysmal third-degree AV block was documented. All cats recovered with medical management within weeks. Each cat resumed a sinus rhythm. Elevated cardiac troponin I concentrations suggested myocarditis that improved.

International collaborative study to assess cardiovascular risk and evaluate long-term health in cats with preclinical hypertrophic cardiomyopathy and apparently healthy cats: The REVEAL Study.

BACKGROUND: Hypertrophic cardiomyopathy is the most prevalent heart disorder in cats and principal cause of cardiovascular morbidity and mortality. Yet, the impact of preclinical disease is unresolved. HYPOTHESIS/OBJECTIVES: Observational study to characterize cardiovascular morbidity and survival in cats with preclinical nonobstructive (HCM) and obstructive (HOCM) hypertrophic cardiomyopathy and in apparently healthy cats (AH). ANIMALS: One thousand seven hundred and thirty client-owned cats (430 preclinical HCM; 578 preclinical HOCM; 722 AH). METHODS: Retrospective multicenter, longitudinal, cohort study. Cats from 21 countries were followed through medical record review and owner or referring veterinarian interviews. Data were analyzed to compare long-term outcomes, incidence, and risk for congestive heart failure (CHF), arterial thromboembolism (ATE), and cardiovascular death. RESULTS: During the study period, CHF, ATE, or both occurred in 30.5% and cardiovascular death in 27.9% of 1008 HCM/HOCM cats. Risk assessed at 1, 5, and 10 years after study entry was 7.0%/3.5%, 19.9%/9.7%, and 23.9%/11.3% for CHF/ATE, and 6.7%, 22.8%, and 28.3% for cardiovascular death, respectively. There were no statistically significant differences between HOCM compared with HCM for cardiovascular morbidity or mortality, time from diagnosis to development of morbidity, or cardiovascular survival. Cats that developed cardiovascular morbidity had short survival (mean ± standard deviation, 1.3 ± 1.7 years). Overall, prolonged longevity was recorded in a minority of preclinical HCM/HOCM cats with 10% reaching 9-15 years. CONCLUSIONS AND CLINICAL IMPORTANCE: Preclinical HCM/HOCM is a global health problem of cats that carries substantial risk for CHF, ATE, and cardiovascular death. This finding underscores the need to identify therapies and monitoring strategies that decrease morbidity and mortality.

Anatomic distribution and electrophysiologic properties of accessory atrioventricular pathways in dogs.

OBJECTIVE: To evaluate the anatomic distribution and electrophysiologic properties of accessory pathways (APs) in dogs. DESIGN: Case series. ANIMALS: 10 dogs with tachyarrhythmias associated with an AP. PROCEDURES: Each dog underwent electrophysiologic testing to determine the inducibility of documented and undocumented arrhythmias and to identify location, conduction properties, and antegrade and retrograde effective refractory periods of the APs. Radiofrequency catheter ablation was then performed. RESULTS: 15 APs were identified; 7 dogs each had a single AP, and 3 had multiple APs. Fourteen of the 15 APs were right-sided (6 right free wall, 4 posteroseptal, 3 midseptal, and 1 anteroseptal), and 1 was left-sided (left free wall). All APs conducted in an all-or-none fashion. Unidirectional retrograde conduction was observed in 11 APs, and bidirectional conduction was observed in 4. All documented tachyarrhythmias could be induced during electrophysiologic testing; atrial fibrillation was also inducible in 2 dogs. Mean +/- SD cycle duration of orthodromic atrioventricular reciprocating tachycardia was 215.80 +/- 44.87 milliseconds. Mean shortest R-R interval during atrial fibrillation was 247.33 +/- 83.17 milliseconds. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that in dogs, most APs are right-sided, had unidirectional retrograde conduction, and are associated with various arrhythmias, including orthodromic atrioventricular reciprocating tachycardia and atrial fibrillation without evidence of pre-excitation.

Prognostic indicators for dogs with dilated cardiomyopathy.

The purpose of this study was to investigate the prognostic value of various clinical, ECG, echocardiographic, and Doppler echocardiographic variables in dogs with dilated cardiomyopathy. The relationship to survival of 11 variables was evaluated in 63 dogs. Studied variables were age at time of diagnosis, class of heart failure (HF), dyspnea, ascites, atrial fibrillation (AF), ejection fraction (EF), E-point septal separation, end-diastolic volume index, end-systolic volume index (ESV-I), and restrictive or nonrestrictive transmitral flow (TMF) pattern. Median survival time was 671 days (lower 95% confidence limit, 350 days). Survival curves showed that severity of HF, ascites, ESV-I greater than 140 mL/m2, EF less than 25%, and restrictive TMF pattern had a significant negative relation to survival time. Thirty-nine dogs with both sinus rhythm and AF presented adequate TMF recordings; in these dogs, after stratification by TMF pattern, the restrictive TMF pattern was the most important negative prognostic indicator. We conclude that in dogs with dilated cardiomyopathy the restrictive TMF pattern appears to represent a useful prognostic indicator. Class of HF, ascites, ESV-I, and EF are also useful indexes if an adequate TMF pattern is not recorded.

Diagnostic imaging of congenital porto-systemic shunts in dogs and cats: a review.

An overview of clinical, laboratory, and diagnostic imaging features of congenital porto-systemic shunt (PSS) in dogs and cats is presented through the analysis of recent literature, and personal case log. Particular emphasis is given to diagnostic accuracy of ultrasonographic examination of PSS in the evaluation of shunt vessel anatomy, and of ancillary findings such as abnormalities of portal vein flow, portal branches, and liver size. Operative mesenteric portography to obtain information on PSS morphology and position, and quantitative hepatic scintigraphy, which allows the calculation of shunt fractions, are also described. Limitations for each diagnostic imaging technique are given.

Analysis of the atrial repolarization wave in dogs with third-degree atrioventricular block.

OBJECTIVE: To characterize the electrocardiographic features of the atrial repolarization (Ta) wave in dogs with third-degree atrioventricular (AV) block. SAMPLE: ECGs of 36 dogs with third-degree AV block and no identifiable structural heart diseases. PROCEDURES: Standard 12-lead ECGs were acquired with a digital system, and measurements were manually edited. RESULTS: A Ta wave was detectable in all dogs for at least 1 ECG lead. The Ta wave had negative polarity in leads I, II, III, and aVF and positive polarity in leads aVL and aVR, with a mean electrical axis of -114.26°. Mean duration and mean amplitude of the Ta wave in lead II were 140.2 milliseconds and -0.09 mV, respectively, with the ratio for the Ta-to-P wave duration of 2.3 and the ratio of Ta-to-P wave amplitude of -0.35. Significant correlations were found between the Ta wave duration and duration of the P-Ta interval, Ta wave amplitude and the ECG lead, Ta wave duration and body weight, and duration of the P-Ta interval and atrial rate. Measurements of the Ta wave were repeatable. CONCLUSIONS AND CLINICAL RELEVANCE: Measurements of the Ta wave in dogs with third-degree AV block were repeatable. The values for the Ta wave reported here can be used as reference values for dogs with AV conduction disturbances and an echocardiographically normal atrial size. Further studies are needed to validate these results in dogs with structural heart diseases.

Radiofrequency catheter ablation of atypical atrial flutter in dogs.

Five dogs were presented to our institution for fatigue caused by an incessant supraventricular tachycardia. In all dogs, an ECG on admission showed a narrow QRS complex tachycardia with a median ventricular cycle length of 220 ms (range 180-360 ms), and a positive atrial depolarization identifiable in the ST segment following the previous QRS complex. There was a 1:1 atrioventricular conduction ratio in all but one dog, which presented with 2:1 atrioventricular block. Electrophysiologic studies identified the underlying arrhythmogenic mechanism as a right atrial macro-reentrant tachycardia with two distinct isthmic areas: right septal (RS) in three dogs and right atrial free wall (RAFW) in two dogs. Linear radiofrequency catheter ablation was performed during tachycardia in all dogs at the identified isthmic area, which acutely blocked the macroreentrant circuit. At 18-month follow-up, 3 dogs (1 with RAFW isthmus and 2 with RS isthmus) showed no recurrence of the arrhythmia on Holter monitoring. One dog with RS isthmus showed recurrence of the supraventricular tachycardia 15 days post-ablation, and 1 dog with RAFW isthmus presented with persistent atrial fibrillation 2 months post-ablation.

Permanent junctional reciprocating tachycardia in a dog.

A 5-year-old male English Bulldog was presented with a 1-year history of paroxysmal supraventricular tachycardia (SVT) partially responsive to amiodarone. At admission the surface ECG showed sustained runs of a narrow QRS complex tachycardia, with a ventricular cycle length (R-R interval) of 260 ms, alternating with periods of sinus rhythm. Endocardial mapping identified the electrogenic mechanism of the SVT as a circus movement tachycardia with retrograde and decremental conduction along a concealed postero-septal atrioventricular pathway (AP) and anterograde conduction along the atrioventricular node. These characteristics were indicative of a permanent junctional reciprocating tachycardia (PJRT). Radiofrequency catheter ablation of the AP successfully terminated the PJRT, with no recurrence of tachycardia on Holter monitoring at 12 months follow-up.

Orthodromic atrioventricular reciprocating tachycardia conducted with intraventricular conduction disturbance mimicking ventricular tachycardia in an English Bulldog.

Electrocardiographic tracings of an English Bulldog referred for cardiogenic shock due to an orthodromic atrioventricular reciprocating tachycardia conducted with intraventricular conduction disturbance and mimicking ventricular tachycardia (VT) are presented. At admission the surface ECG showed a wide QRS complex tachycardia (WCT) that was converted to sinus rhythm using manual cardioversion (chest thump). This change revealed pre-existing right bundle branch block, and a final diagnosis of supraventricular tachycardia (SVT) with intraventricular conduction disturbance was made. Electrophysiologic study defined the SVT mechanism as an atrioventricular macroreentrant tachycardia mediated by a single mid-septal accessory pathway. The differentiation between various types of WCT is essential when antiarrhythmic therapy is considered. The surface ECG should be systematically evaluated in order to recognize the characteristic features of SVT and VT. Moreover chest thump procedure can be very helpful in the attempt to convert the rhythm to sinus rhythm and to correctly recognize the underlying arrhythmia.