Automated echocardiographic left ventricular dimension assessment in dogs using artificial intelligence: Development and validation.

BACKGROUND: Artificial intelligence (AI) could improve accuracy and reproducibility of echocardiographic measurements in dogs. HYPOTHESIS: A neural network can be trained to measure echocardiographic left ventricular (LV) linear dimensions in dogs. ANIMALS: Training dataset: 1398 frames from 461 canine echocardiograms from a single specialist center. VALIDATION: 50 additional echocardiograms from the same center. METHODS: Training dataset: a right parasternal 4-chamber long axis frame from each study, labeled by 1 of 18 echocardiographers, marking anterior and posterior points of the septum and free wall. VALIDATION DATASET: End-diastolic and end-systolic frames from 50 studies, annotated twice (blindly) by 13 experts, producing 26 measurements of each site from each frame. The neural network also made these measurements. We quantified its accuracy as the deviation from the expert consensus, using the individual-expert deviation from consensus as context for acceptable variation. The deviation of the AI measurement away from the expert consensus was assessed on each individual frame and compared with the root-mean-square-variation of the individual expert opinions away from that consensus. RESULTS: For the septum in end-diastole, individual expert opinions deviated by 0.12 cm from the consensus, while the AI deviated by 0.11 cm (P = .61). For LVD, the corresponding values were 0.20 cm for experts and 0.13 cm for AI (P = .65); for the free wall, experts 0.20 cm, AI 0.13 cm (P < .01). In end-systole, there were no differences between individual expert and AI performances. CONCLUSIONS AND CLINICAL IMPORTANCE: An artificial intelligence network can be trained to adequately measure linear LV dimensions, with performance indistinguishable from that of experts.

Prevalence and Clinical Significance of Heart Murmurs Detected on Cardiac Auscultation in 856 Cats.

BACKGROUND: Cardiac auscultation is one of the most important clinical tools to identify patients with a potential heart disease. Although several publications have reported the prevalence of murmurs in cats, little information is available in relation to the exact origin of the blood flow turbulences responsible for these murmurs. The aim of this study was to determine the prevalence and clinical significance of murmurs detected during physical examination in cats. METHODS: Retrospective evaluation of clinical records and echocardiographic examinations performed in cats for investigation of heart murmurs; Results: Records of 856 cats with full clinical information were available for review. The cause of murmur was identified in 93.1% of cases (72.3% with single blood flow turbulence, 26.4% with two, and 1.3% with three identifiable sources of murmur). Systolic anterior motion of the mitral valve (SAM) was the primary cause of murmur in this population (39.2%), followed by dynamic right ventricular outflow tract obstruction (DRVOTO) (32%) and flow murmurs (6.9%). Most cats with a murmur (56.7%) did not present any structural cardiac abnormality. CONCLUSIONS: This study indicates that some heart murmur characteristics (timing, loudness and point of maximal intensity) can potentially predict the presence of an underlying cardiac disease.

Infection with SARS-CoV-2 variant B.1.1.7 detected in a group of dogs and cats with suspected myocarditis.

BACKGROUND: Domestic pets can contract severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection; however, it is unknown whether the UK B.1.1.7 variant can more easily infect certain animal species or increase the possibility of human-to-animal transmission. METHODS: This is a descriptive case series reporting SARS-CoV-2 B.1.1.7 variant infections in a group of dogs and cats with suspected myocarditis. RESULTS: The study describes the infection of domestic cats and dogs by the B.1.1.7 variant. Two cats and one dog were positive to SARS-CoV-2 PCR on rectal swab, and two cats and one dog were found to have SARS-CoV-2 antibodies 2-6 weeks after they developed signs of cardiac disease. Many owners of these pets had developed respiratory symptoms 3-6 weeks before their pets became ill and had also tested positive for COVID-19. Interestingly, all these pets were referred for acute onset of cardiac disease, including severe myocardial disorders of suspected inflammatory origin but without primary respiratory signs. CONCLUSIONS: These findings demonstrate, for the first time, the ability for pets to be infected by the B.1.1.7 variant and question its possible pathogenicity in these animals.

Prevalence of sudden cardiac death in dogs with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is associated with increased risk of sudden cardiac death (SCD) in humans, independent of secondary risk factors such as thrombogenic disorders. In dogs, SCD is described in a number of heart diseases, but an association between AF and SCD is unreported. HYPOTHESIS: (a) A higher proportion of dogs with AF will experience SCD, and (b) SCD will be associated with complex ventricular arrhythmias. ANIMALS: One-hundred forty-two dogs with AF, and 127 dogs without AF. METHODS: Retrospective, multicenter, case-control study. Dogs included in the AF group were compared to a control group of dogs in sinus rhythm, matched for echocardiographic diagnosis. Descriptive statistics were used to identify proportions of each group suffering SCD, compared using chi-squared testing. Risk factors for SCD in dogs with AF were evaluated at the univariable and multivariable level using binary logistic regression. Significance was P < .05. RESULTS: A significantly higher proportion of dogs with AF suffered SCD than dogs in the control group (14.8% vs 5.5%; P = .01). Younger age at diagnosis, larger left atrial size, and a history of syncope all were independent predictors of SCD in dogs with AF (χ2 , 16.3; P = .04). CONCLUSIONS AND CLINICAL IMPORTANCE: Atrial fibrillation was associated with a higher prevalence of SCD in dogs. A history of syncope may be a useful predictor of SCD risk.

Heart murmurs in apparently healthy cats caused by iatrogenic dynamic right ventricular outflow tract obstruction.

BACKGROUND: Heart murmurs are detected commonly in apparently healthy cats during routine physical examination, and Doppler echocardiography ultimately is required to identify the source of flow turbulence causing the murmur. However, in some cases, the origin of the murmur cannot be identified on echocardiographic examination, even by experienced clinicians. The application of gentle pressure with the ultrasound transducer against the chest wall of a cat can induce temporary narrowing of the mid-right ventricular (RV) lumen, causing blood flow turbulence even in the absence of cardiac abnormalities. OBJECTIVES/HYPOTHESES: To evaluate the effect of pressure of the ultrasound transducer against the chest wall of cats during echocardiography (provocative testing) on RV blood flow. The main hypothesis is that provocative testing can increase RV outflow velocity and cause flow turbulence. The second hypothesis is that the effect of this maneuver is independent of changes in heart rate during testing. ANIMALS: Sixty-one client-owned, apparently healthy cats with heart murmurs on physical examination. METHODS: Retrospective review of echocardiographic examinations of 723 cats presented for investigation of a heart murmur. RESULTS: Outflow systolic velocity increased from 1.05 ± 0.26 to 1.94 ± 0.51 m/s during provocative testing (P < .0001); no correlation was found between RV outflow peak velocity and heart rate during provocative testing (P = .34; r = 0.1237). CONCLUSIONS AND CLINICAL RELEVANCE: Right ventricular outflow tract obstruction and associated heart murmur can be iatrogenically induced in apparently healthy cats by increasing pressure on the right chest wall with an ultrasound probe.

Evaluation of benazepril in cats with heart disease in a prospective, randomized, blinded, placebo-controlled clinical trial.

BACKGROUND: Heart disease is an important cause of morbidity and mortality in cats, but there is limited evidence of the benefit of any medication. HYPOTHESIS: The angiotensin-converting enzyme inhibitor benazepril would delay the time to treatment failure in cats with heart disease of various etiologies. ANIMALS: One hundred fifty-one client-owned cats. METHODS: Cats with heart disease, confirmed by echocardiography, with or without clinical signs of congestive heart failure, were recruited between 2002 and 2005 and randomized to benazepril or placebo in a prospective, multicenter, parallel-group, blinded clinical trial. Benazepril (0.5-1.0 mg/kg) or placebo was administered PO once daily for up to 2 years. The primary endpoint was treatment failure. Analyses were conducted separately for all-cause treatment failure (main analysis) and heart disease-related treatment failure (supportive analysis). RESULTS: No benefit of benazepril versus placebo was detected for time to all-cause treatment failure (P = .42) or time to treatment failure related to heart disease (P = .21). Hazard ratios (95% confidence interval [CI]) from multivariate analysis for benazepril compared with placebo were 1.00 (0.57-1.74) for all-cause failure, and 0.99 (0.50-1.94) for forward selection and 0.93 (0.48-1.81) for bidirectional selection models for heart disease-related failure. There were no significant differences between groups over time after administration of the test articles in left atrium diameter, left ventricle wall thickness, quality of life scores, adverse events, or plasma biochemistry or hematology variables. CONCLUSIONS AND CLINICAL RELEVANCE: Benazepril was tolerated well in cats with heart disease, but no evidence of benefit was detected.

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.

Reliability of an incremental exercise test to evaluate acute blood lactate, heart rate and body temperature responses in Labrador retrievers.

Thirteen healthy Labrador retrievers underwent a 5-stage incremental treadmill exercise test to assess its reliability. Blood lactate (BL), heart rate (HR), and body temperature (BT) were measured at rest, after each stage of exercise, and after a 20-min recovery. Reproducibility was assessed by repeating the test after 7 days. Two-way MANOVAs revealed significant differences between consecutive stages, and between values at rest and after recovery. There was also a significant reduction in physiological strain between the first and second trial (learning effect). Test reliability expressed as typical error (BL = 0.22 mmol/l, HR = 9.81 bpm, BT = 0.22 degrees C), coefficient of variation (BL = 19.3%, HR = 7.9% and BT = 0.6%) and test-retest correlation (BL = 0.89, HR = 0.96, BT = 0.95) was good. Results support test reproducibility although the learning effect needs to be controlled when investigating the exercise-related problems commonly observed in this breed.

Evaluation of serum cardiac troponin I concentration in dogs with renal failure.

OBJECTIVE: To determine whether dogs with renal failure have higher serum cardiac troponin I (cTnI) concentrations than healthy dogs. DESIGN: Case-control study. ANIMALS: 31 dogs with renal failure and 51 healthy dogs. PROCEDURES: Serum concentrations of creatinine and cardiac troponin I, urine specific gravity, and systolic arterial blood pressure were measured for all dogs. Dogs underwent a standardized physical examination, and any dog with evidence of cardiovascular disease or other nonrenal disease was excluded from final analyses. Dogs were considered to be in renal failure when the serum creatinine concentration was >or= 3.0 mg/dL, urine specific gravity was between 1.007 and 1.030, and renal failure had been clinically diagnosed. RESULTS: Dogs with renal failure had significantly higher serum cTnI concentrations (median, 0.35 ng/mL) than did healthy dogs (0.20 ng/mL). The renal failure group also had a significantly higher median systolic blood pressure (156 mm Hg) than did healthy dogs (138 mm Hg), although serum cTnI concentration was not correlated with systolic blood pressure in dogs with renal failure. There was no significant difference in age between dogs with renal failure and healthy dogs, but dogs with renal failure had significantly higher serum creatinine concentration and lower urine specific gravity. CONCLUSIONS AND CLINICAL RELEVANCE: Although dogs with renal failure did not have overt clinical signs of cardiac disease, they had high serum cTnI concentrations, which may have been associated with subclinical cardiovascular disease. The cause of the high serum cTnI concentration in these dogs requires additional investigation.

Recurrent syncope associated with paroxysmal supraventricular tachycardia in a Devon Rex cat diagnosed by implantable loop recorder.

A 9-year-old male neutered Devon Rex cat was presented for continued investigations following a 7-year history of recurrent syncope. Previous diagnostic tests, including 24h (Holter) electrocardiographic monitoring, had failed to identify the aetiology of such episodes, and former empirical treatment with atenolol had not provided satisfactory control of the clinical signs. A conclusive diagnosis was eventually achieved using an implantable loop recorder (Reveal), which identified paroxysmal supraventricular tachycardia (SVT) associated with a syncopal episode. Treatment with oral sotalol was instituted and, 18 months after initiation of anti-arrhythmic therapy, no further syncopal episodes have been observed by the cat's owners.

Comparison of canine capillary and jugular venous blood lactate concentrations determined by use of an enzymatic-amperometric bedside system.

OBJECTIVE: To evaluate the analytical agreement between blood lactate concentrations determined by use of an enzymatic-amperometric bedside system in capillary blood samples from the pinna and in jugular venous blood samples from dogs. ANIMALS: 53 dogs. PROCEDURES: For each dog, venous and capillary blood samples were obtained from a jugular vein and from the ear pinna (by use of a lancing device), respectively, following a randomized sequence of collection. Lactate concentrations in both types of samples were analyzed by use of an enzymatic-amperometric bedside system intended for lactate detection in capillary blood samples from humans that was previously validated in dogs. The Passing-Bablock regression analysis was used to compare venous and capillary blood lactate concentrations; the level of agreement was calculated by use of the Bland-Altman method. RESULTS: Jugular venous blood samples were collected without difficulty from all 53 dogs. A capillary blood sample was obtained from only 47 dogs. The correlation coefficient between lactate concentrations measured in venous and capillary blood samples was 0.58 (slope, 2.0 [95% confidence interval, 1.5 to 3.0]; intercept, -1.2 [95% confidence interval, -3.1 to 0.4]). The mean difference between methods was 0.72 mmol/L (95% confidence interval, 0.38 to 1.06) with limits of agreement of -1.55 to 2.99 mmol/L. CONCLUSIONS AND CLINICAL RELEVANCE: Because of the lack of agreement between lactate concentrations determined in capillary and jugular venous blood samples, measurement of capillary blood lactate concentration in dogs performed with the technique used in the study does not appear to be a reliable alternative to jugular venous blood measurements.

Evaluation of a portable lactate analyzer (Lactate Scout) in dogs.

BACKGROUND: Measurement of blood lactate concentration has become a common practice in canine medicine. However, the accuracy of portable lactate monitors has not been reported in dogs. OBJECTIVES: The aim of this study was to evaluate the accuracy and precision of a portable analyzer (Lactate-Scout) in measuring canine blood lactate concentration. METHODS: A preliminary study was performed to assess the effects of sample storage time and temperature on plasma lactate concentration. Blood samples obtained from 6 canine patients at our hospital were divided into 8 aliquots and stored at 4 degrees C and 20 degrees C; plasma lactate was measured in duplicate with a spectrophotometric system (Konelab) at 0, 30, 60, 120, and 240 minutes after the blood collection. Values were compared with those obtained immediately after blood collection. Lactate values obtained by the portable method also were compared with those obtained by the reference spectrophotometric analyzer on blood samples collected from 48 additional canine patients. RESULTS: There was no significant effect of storage time (P = .89) or temperature (P = .51) on plasma lactate levels. The correlation between lactate values measured with the Lactate-Scout and the Konelab method was r = .98 (slope = .81, 95% confidence interval = .73-.87; intercept = .20, 95% confidence interval = .13-.31). The level of agreement between the 2 methods was generally good for mean lactate concentrations <5 mmol/L. However, at higher lactate concentrations (5 of 48 samples), the values recorded by the Lactate-Scout analyzer were lower than those measured by the Konelab method. CONCLUSION: The Lactate-Scout analyzer is reliably comparable to a reference method for measuring whole blood lactate concentration in dogs; however, caution should be used when interpreting lactate values of 5 mmol/L and higher.

Validation of 2 techniques for electrocardiographic recording in dogs and cats.

BACKGROUND: Standard electrocardiographic (ECG) recording in the dog and cat is commonly performed in right lateral recumbency, by connecting the ECG leads to the skin of the patient via metallic alligator clips. The jaws of the alligator clips are usually filed or flattened to reduce their uncomfortable pressure on the patient's skin. However, filed and flattened alligator clips can occasionally lose their grip to the skin, causing lead detachment during standard ECG recording. HYPOTHESIS: The aim of the study was to validate two novel ECG recording techniques ("gel" and "pads"). ANIMALS: Six-lead standard ECG recording was obtained from 42 dogs and 40 cats using the standard technique, as well as the two novel methods. METHODS: Measurements were taken of the amplitude and duration of P waves and QRS complexes, duration of PQ and QT intervals, and mean electrical axis (MEA). In each recording, five representative complexes were measured, and the results were averaged for each parameter. RESULTS: A good quality ECG recording was obtained with all the three different techniques, although a degree of wandering trace was observed in one third of cats with the "pads" technique. Bland-Altman analysis showed good agreement between the ECG values recorded with the two novel techniques and those recorded with the standard traditional technique. Furthermore, the observed differences were not clinically relevant, except for the R wave amplitude recorded with the "pads" method in cats (-0.35 to 0.37 mV). CONCLUSIONS AND CLINICAL IMPORTANCE: In conclusion, this study supports the reliability and clinical validity of the "gel" and "pads" techniques for ECG recording both in the dog and the cat, with some limitations for the "pads" technique in cats.