An engineering perspective on the development and evolution of implantable cardiac monitors in free-living animals.

The latest technologies associated with implantable physiological monitoring devices can record multiple channels of data (including: heart rates and rhythms, activity, temperature, impedance and posture), and coupled with powerful software applications, have provided novel insights into the physiology of animals in the wild. This perspective details past challenges and lessons learned from the uses and developments of implanted biologgers designed for human clinical application in our research on free-ranging American black bears (Ursus americanus). In addition, we reference other research by colleagues and collaborators who have leveraged these devices in their work, including: brown bears (Ursus arctos), grey wolves (Canis lupus), moose (Alces alces), maned wolves (Chrysocyon brachyurus) and southern elephant seals (Mirounga leonina). We also discuss the potentials for applications of such devices across a range of other species. To date, the devices described have been used in fifteen different wild species, with publications pending in many instances. We have focused our physiological research on the analyses of heart rates and rhythms and thus special attention will be paid to this topic. We then discuss some major expected step changes such as improvements in sensing algorithms, data storage, and the incorporation of next-generation short-range wireless telemetry. The latter provides new avenues for data transfer, and when combined with cloud-based computing, it not only provides means for big data storage but also the ability to readily leverage high-performance computing platforms using artificial intelligence and machine learning algorithms. These advances will dramatically increase both data quantity and quality and will facilitate the development of automated recognition of extreme physiological events or key behaviours of interest in a broad array of environments, thus further aiding wildlife monitoring and management. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.

Towards non-invasive heart rate monitoring in free-ranging cetaceans: a unipolar suction cup tag measured the heart rate of trained Risso's dolphins.

Heart rate monitoring in free-ranging cetaceans to understand their behavioural ecology and diving physiology is challenging. Here, we developed a simple, non-invasive method to monitor the heart rate of cetaceans in the field using an electrocardiogram-measuring device and a single suction cup equipped with an electrode. The unipolar suction cup was placed on the left lateral body surface behind the pectoral fin of Risso's dolphins (Grampus griseus) and a false killer whale (Pseudorca crassidens) in captivity; their heart rate was successfully monitored. We observed large heart rate oscillations corresponding to respiration in the motionless whales during surfacing (a false killer whale, mean 47 bpm, range 20-75 bpm; Risso's dolphins, mean ± s.d. 61 ± 15 bpm, range 28-120 bpm, n = 4 individuals), which was consistent with the sinus arrhythmia pattern (eupneic tachycardia and apneic bradycardia) observed in other cetaceans. Immediately after respiration, the heart rate rapidly increased to approximately twice that observed prior to the breath. Heart rate then gradually decreased at around 20-50 s and remained relatively constant until the next breath. Furthermore, we successfully monitored the heart rate of a free-swimming Risso's dolphin. The all-in-one suction cup device is feasible for field use without restraining animals and is helpful in further understanding the diving physiology of free-ranging cetaceans. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.

Evaluation of echocardiographic variables of morphometry and function in horses submitted to minimally invasive partial pericardiotomy / [Avaliação de variáveis ecocardiográficas morfométricas e funcionais em cavalos submetidos à pericardiotomia parcial minimamente invasiva]

This study aimed to evaluate the impact of minimally invasive partial pericardiotomy on echocardiographic variables of morphometry and function in healthy horses. Minimally invasive pericardiotomy was performed in six healthy horses. Echocardiographic evaluation was executed in different moments: prior to the surgical procedure (M0); 24 hours post procedure (M1); 72 hours post procedure (M2) and 28 days post procedure (M3). The following variables were measured: Right ventricular internal diameter in diastole and systole (RVd and RVs), interventricular septum thickness in diastole and systole (IVSd and IVSs), left ventricular internal diameter in diastole and systole (LVd and LVs), left ventricular free wall thickness in diastole and systole (LVFWd and LVFWs), aortic root diameter (Ao) and left atrial diameter (LA). From this data, the following variables were calculated: fractional shortening (FS%), fractional thickening of the interventricular septum (IVS%), fractional thickening of the left ventricular free wall (LVFW%) and the relationship between left atrial and aortic diameters (LA/Ao). After 28 days, a new thoracoscopy was performed for inspection of the thoracic cavity. In M1 and M2 ECO evaluations, a statistically significant change in LVFW and a decrease in RVd, LVd, LVFWs, LA, LVs, FS% and IVS was documented. Pericardiotomy is a promising technique in horses, with minor postoperative complication. The variations in the echocardiographic parameters were transient and did not cause hemodynamic damage to the animals.(AU)

O objetivo do presente estudo foi avaliar o impacto da pericardiotomia parcial minimamente invasiva sobre as variáveis ecocardiográficas morfométricas e funcionais em cavalos, visto que não há nenhum trabalho que tenha avaliado o impacto da pericardiotomia na espécie equina. Foram utilizados seis cavalos hígidos, nos quais se realizou pericardiotomia minimamente invasiva. Em todos eles, foi efetuado exame ecocardiográfico em diferentes momentos: previamente ao procedimento cirúrgico (M0); 24 horas após (M1); 72 horas após (M2) e 28 dias após (M3). Foram mensurados: diâmetro interno do ventrículo direito (VDd e VDs), espessura do septo interventricular (SIVd e SIVs), diâmetro interno do ventrículo esquerdo (VEd e VEs), espessura da parede livre do ventrículo esquerdo (PLVEd e PLVEs), diâmetro interno da aorta (Ao) e diâmetro atrial esquerdo (AE). Foram calculadas as variáveis fração de encurtamento (FEC%), espessamento fracional do septo interventricular (SIV%), espessamento fracional da parede livre do ventrículo esquerdo (PLVE%) e relação entre diâmetro do átrio esquerdo e diâmetro aórtico (AE/Ao). Após 28 dias, realizou-se nova toracoscopia para inspeção da cavidade torácica. Nas avaliações do ECO no M1 e no M2, houve alteração estatisticamente significativa no PLVE em diástole (28±5,5 e 31,7±2, respectivamente) e diminuição dos parâmetros VDd,(30,1±11,6 e 31,7± 10,7) VEd (113,3±21 e 121,7±13,7), PLVEs (42±8,2 e 43,9±2,8), AE (78,5±6,1 e 82,7±4,7), VEs (74,1±16 e 71,5±9,3), FEC (34,4±10,2 e 41,2±5,7) e SIV (27,1±8,7 e 42,3±27,9). A técnica de pericardiotomia empregada mostrou-se promissora em equinos. As variações dos parâmetros ecocardiográficos foram transitórias, não causando prejuízos hemodinâmicos aos animais.(AU)

Interval exercise training increases LIF expression and prevents myocardial infarction-induced skeletal muscle atrophy in rats.

AIMS: Myocardial infarction (MI) is commonly associated with body weight loss and skeletal muscle atrophy. Studies have shown that exercise training could give beneficial effects on skeletal muscle growth. Leukemia inhibitory factor (LIF) is a key regulator of muscle growth and regeneration. The aim of this study was to investigate the effects of interval exercise training (IET) on the expression of LIF and the MI-induced skeletal muscle atrophy. MAIN METHODS: Male Sprague-Dawley rats were used to establish the MI model by ligation of the left anterior descending coronary artery. Infarcted Rats were divided into two groups: sedentary MI group (MI) and MI with interval exercise group (ME), and compared to sham-operated group (Sham). Exercise-trained animals were subjected to eight weeks of IET. Cardiac function, collagen volume fraction, expression of LIF and its receptor LIFR, myofiber size, apoptosis and proliferation in gastrocnemius muscle were analyzed. KEY FINDINGS: IET increased heart functional performance and was accompanied with reversing cardiac pathological remodeling. Moreover, IET increased the expression of LIF and LIFR, activated signal transducer and activator of transcription (STAT3), reduced apoptosis and promoted proliferation in gastrocnemius muscle compared with the MI group. In addition, there was a significant negative correlation between skeletal muscle atrophy and LIF expression which was stimulated by IET in infarcted rats. SIGNIFICANCE: IET reverses MI-induced cardiac dysfunction and skeletal muscle atrophy. In addition, IET up-regulates the expression of muscle LIF/LIFR and activates the STAT3.

An exploratory investigation of echocardiographic parameters and the effects of posture on cardiac structure and function in the Livingstone's fruit bat (Pteropus livingstonii).

There is growing evidence that dilated cardiomyopathy may be a major cause of death in captive Livingstone's fruit bats (Pteropus livingstonii). Therefore, the primary aim of this prospective, exploratory study was to examine whether a systematic cardiac ultrasound protocol is feasible in this critically endangered species and to report basic measures of cardiac structure and function from a cohort of apparently healthy bats. A secondary aim was to test the effect posture (dorsal recumbency vs. roosting) has upon cardiac function in this species. Transthoracic echocardiograms, including 2D, Doppler, and tissue Doppler measures of cardiac structure and function were completed as part of routine health examinations for bats at a single center (n = 19). Bats were then grouped by age and disease status and the mean and range data reported for each group. In healthy adult bats, with the exception of a reduction in heart rate (P ≤ 0.05), right atrial systolic area (P ≤ 0.05), and right ventricular velocity during atrial contraction, there were no significant changes in cardiac structure or function in response to the roosting position. However, in the bats presenting with dilated cardiomyopathy the current data suggest that left ventricular ejection fraction is improved while roosting. Further work is required to confirm our initial findings, generate diagnostic reference intervals, and explore the causes of dilated cardiomyopathy in this species.

Assessment of left ventricular volume and function in healthy dogs by use of one-, two-, and three-dimensional echocardiography versus multidetector computed tomography.

OBJECTIVE To compare left ventricle (LV) volume and function variables obtained by use of 1-D, 2-D, and real-time 3-D echocardiography versus ECG-gated multidetector row CT (MDCT) angiography, which was considered the criterion-referenced standard. ANIMALS 6 healthy, purpose-bred dogs. PROCEDURES Dogs were anesthetized and administered a constant rate infusion of esmolol, and 1-D, 2-D, and 3-D echocardiography and ECG-gated, contrast-enhanced MDCT were performed. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume, and ejection fraction (EF) were calculated by use of the Teichholz method for 1-D echocardiography, single-plane and biplane modified Simpson method of disks (MOD) and area-length method for 2-D echocardiography, and real-time biplane echocardiography (RTBPE) and real-time 3-D echocardiography (RT3DE) for 3-D echocardiography. Volumes were indexed to body surface area and body weight. Median values, correlations, and limits of agreement were compared between echocardiographic modalities and MDCT. RESULTS EDV and ESV measured by use of RTBPE and RT3DE had the strongest correlations with results for MDCT. Values obtained for EDV, ESV, stroke volume, and EF did not differ significantly between echocardiographic methods and MDCT. Use of RT3DE and RTBPE slightly underestimated EDV, ESV, and EF, compared with values for MDCT, as determined with Bland-Altman analysis. CONCLUSIONS AND CLINICAL RELEVANCE Values for EDV and ESV obtained by use of 3-D echocardiography, including RTBPE and RT3DE, had the highest correlation with slight underestimation, compared with values obtained by use of MDCT. This was similar to results for 3-D echocardiography in human medicine.

Evaluation of the non-calibrated pulse contour cardiac output monitor FloTrac/Vigileo against thermodilution in standing horses.

OBJECTIVE: To evaluate the non-calibrated, minimally invasive cardiac output (CO) monitor FloTrac/Vigileo (FloTrac) against thermodilution (TD) CO in standing horses. STUDY DESIGN: Prospective, experimental trial. ANIMALS: Nine adult horses weighing a median (range) of 535 (470-602) kg. METHODS: Catheters were placed in the right atrium, pulmonary artery and carotid artery under local anaesthesia. CO was measured 147 times by TD and FloTrac and indexed to body weight. Changes in CO were achieved with romifidine or xylazine and dobutamine constant rate infusions. Bland-Altman analysis, concordance and polar plot analysis were used to assess agreement and ability to track changes in CO. RESULTS: Mean ± standard deviation COTD of 48 ± 16 mL kg(-1) minute(-1) (range: 19-93 mL kg(-1) minute(-1) ) and mean COF loTrac of 9 ± 3 mL kg(-1) minute(-1) (range: 5-21 mL kg(-1) minute(-1) ) were measured. Low agreement with a large mean bias of 39 mL kg(-1) minute(-1) and wide limits of agreement of 8-70 mL kg(-1) minute(-1) were found. The percentage error of 108% and precision of TD of ± 18% resulted in an estimated precision of FloTrac of ± 106%. Comparison of changes in COF loTrac with changes in COTD gave a concordance rate of 52% in the four-quadrant plot, and a mean polar angle of -11° with radial limits of agreement of ± 61 ° in the polar plot. Mean arterial pressure (MAP) and COF loTrac were positively correlated (r = 0.5, p < 0.0001). No correlation of MAP with COTD was observed. CONCLUSIONS AND CLINICAL RELEVANCE: The FloTrac system, originally designed for use in humans, neither measured absolute CO in standing horses accurately nor tracked relative changes in CO measured by TD correctly. The false dependence of COF loTrac on arterial blood pressure further discourages the use of this technique in horses.

Using Cardiac Biomarkers in Veterinary Practice.

Blood-based assays for various cardiac biomarkers can assist in the diagnosis of heart disease in dogs and cats. The two most common markers are cardiac troponin-I and N-terminal pro-B-type natriuretic peptide. Biomarker assays can assist in differentiating cardiac from noncardiac causes of respiratory signs and detection of preclinical cardiomyopathy. Increasingly, studies indicate that cardiac biomarker testing can help assess the risk of morbidity and mortality in animals with heart disease. Usage of cardiac biomarker testing in clinical practice relies on proper patient selection, correct interpretation of test results, and incorporation of biomarker testing into existing diagnostic methods.

Comparison of echocardiographic measurements in elite and nonelite Arabian endurance horses.

OBJECTIVE: To determine whether echocardiographic variables differed between successful (elite) and less successful (nonelite) Arabian endurance horses. ANIMALS: 34 Arabian horses that competed in endurance racing. PROCEDURES: Horses were assigned to either an elite or nonelite group on the basis of results of a previous competition, and a standardized echocardiographic examination was performed on each horse within 1 to 4 weeks after that competition. Multivariable logistic regression with backward stepwise elimination was used to create a prediction model for the determination of horse status (elite or nonelite) as a function of the measured echocardiographic variables. RESULTS: The elite and nonelite groups consisted of 23 and 11 horses, respectively. One horse in the nonelite group had a frequent ventricular dysrhythmia that could have negatively affected its performance and rider's safety, whereas none of the horses in the elite group had remarkable cardiac abnormalities. The left ventricular internal diameter during systole and diastole and left ventricular mass and stroke volume were significantly greater for horses in the elite group, compared with those for horses in the nonelite group. The final logistic regression model correctly predicted the horse status for all of the horses in the elite group and 8 of 11 horses in the nonelite group. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that heart size was significantly associated with performance for Arabian endurance horses in a manner similar to findings for Thoroughbred and Standardbred racehorses in active competition.

Comparison of cardiac output determined by an ultrasound velocity dilution cardiac output method and by the lithium dilution cardiac output method in juvenile horses with experimentally induced hypovolemia.

OBJECTIVE: To assess the accuracy of an ultrasound velocity dilution cardiac output (UDCO) method, compared with that of the lithium dilution cardiac output (LiDCO) method, for determination of cardiac output (CO) in juvenile horses with experimentally induced hypovolemia. ANIMALS: 12 anesthetized 2- to 6-month-old horses. PROCEDURES: For each anesthetized horse, CO was determined by the LiDCO and UDCO methods prior to any intervention (baseline state), after withdrawal of approximately 40% of the horse's blood volume (low CO state), after maintenance of hypovolemia and infusion of norepinephrine until mean arterial blood pressure was equal to baseline value (high CO state), and after further infusion of norepinephrine and back-transfusion of withdrawn blood (posttransfusion state). For each of the 4 hemodynamic situations, CO and calculated cardiac index (CI) values were obtained by each method in duplicate (8 pairs of measurements/horse); mean values for each horse and overall mean values across all horses were calculated. Agreement between CI determined by each method (96 paired values) was assessed by Bland-Altman analysis. RESULTS: For the UDCO method-derived CI measurements among the 12 horses, mean ± SD bias was -4 ± 11.3 mL/kg/min (95% limits of agreement, -26.1 to 18.2 mL/kg/min) and mean relative bias was -10.4 ± 21.5% (95% limits of agreement, -52.6% to 31.8%). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that, compared with the LiDCO method, the UDCO method has acceptable clinical usefulness for determination of CO in foals.

Cardiac output monitoring in horses.

Cardiac output (CO) is the volume of blood pumped out by the heart in 1 minute. Monitoring of CO can guide therapy and improve clinical outcome in critically ill patients and during anesthesia. Although there is increasing research into clinically useful methods of monitoring CO in equine patients, there are limitations to the available methods. There are 4 basic methods of measuring CO: (1) indicator methods, (2) a derivation of the Fick principle, (3) arterial pulse wave analysis, and (4) imaging diagnostic techniques. This article discusses the importance of CO, available technology, and challenges of monitoring CO in equine medicine.

Tei index (myocardial performance index) and cardiac biomarkers in dogs with parvoviral enteritis.

Tei index (myocardial performance) and cardiac biomarkers were evaluated in dogs with parvoviral enteritis (PVE). Tei index was calculated as isovolumic contraction time plus isovolumic relaxation time divided by ejection time. Myocardial and skeletal muscle damages were assessed by serum levels of cardiac troponin I (cTnI), creatine (phospho) kinase, lactate dehydrogenase and aspartate aminotransferase. Serum magnesium level was also determined. According to treatment response, dogs were divided into the survivor (n=20) and non-survivor groups (n=23). Seven healthy dogs served as controls. The mean value of the Tei index was higher in non-survivors, compared with survivors (p<0.02) and healthy controls (p<0.01). Serum level of cTnI in non-survivors was higher than that of survivors and controls (p<0.05). Tei index showed the highest sensitivity and specificity to predict mortality. The findings of an elevated Tei index and an increase in serum cTnI are factors associated with a poor prognosis in cases of canine parvovirosis.

Comparison of cardiac output determined by arterial pulse pressure waveform analysis method (FloTrac/Vigileo) versus lithium dilution method in anesthetized dogs.

OBJECTIVE: To compare the determination of cardiac output (CO) via arterial pulse pressure waveform analysis (FloTrac/Vigileo) versus lithium dilution method. DESIGN: Prospective study. SETTING: University teaching hospital. ANIMALS: Six adult dogs. INTERVENTIONS: Dogs were instrumented for CO determinations using lithium dilution (LiDCO) and FloTrac/Vigileo methods. Direct blood pressure, heart rate, arterial blood gases, and end-tidal isoflurane (ETIso) and CO(2) concentrations were measured throughout the study while CO was manipulated with different depth of anesthesia and rapid administration of isotonic crystalloids at 60 mL/kg/h. MEASUREMENTS AND MAIN RESULTS: Baseline CO measurements were obtained at 1.3% ETIso and were lowered by 3% ETIso. Measurements were obtained in duplicate or triplicate with LiDCO and averaged for comparison with corresponding values measured continuously with the FloTrac/Vigileo method. For 30 comparisons between methods, a mean bias of -100 mL/kg/min and 95% limits of agreement between -311 and +112 mL/kg/min (212 mL/kg/min) was determined. The mean (mL/kg/min) of the differences of LiDCO-Vigileo=62.0402+-0.8383 × Vigileo, and the correlation coefficient (r) between the 2 methods 0.70 for all CO determinations. The repeatability coefficients for the individual LiDCO and FloTrac/Vigileo methods were 187 and 400 mL/kg/min, respectively. Mean LiDCO and FloTrac/Vigileo values from all measurements were 145 ± 68 mL/kg/min (range, 64-354) and 244 ± 144 mL/kg/min (range, 89-624), respectively. The overall mean relative error was 48 ± 14%. CONCLUSION: The FloTrac/Vigileo overestimated CO values compared with LiDCO and the relative error was high, which makes this method unreliable for use in dogs.

Assessment of cardiac output measurement in dogs by transpulmonary pulse contour analysis.

OBJECTIVE: To determine if metatarsal artery pressure (COmet) is comparable to femoral artery pressure (COfem) as the input for transpulmonary pulse contour analysis (PiCCO) in anesthetized dogs, using the lithium dilution method (LiDCO) as a standard for cardiac output (CO) measurement. DESIGN: Prospective randomized study. SETTING: University research laboratory. ANIMALS: Ten healthy purpose-bred mixed breed dogs were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. INTERVENTIONS: The CO was measured using LiDCO and PiCCO techniques. Animals had their right femoral and left distal metatarsal artery catheterized for proximal (COfem) and distal (COmet) PiCCO analysis, respectively. Measurements were obtained from each animal during low, normal, and high CO states by changing amount of inhalant anesthetics and heart rate. Measurements were converted to CO indexed to body weigh (CI(BW) =CO/kg) for statistical analysis. Agreement was determined using Bland and Altman analysis and concordance correlation coefficients. MEASUREMENTS AND MAIN RESULTS: Thirty paired measurements were taken. The LiDCO CI(BW) (± SD) was 68.7 ± 30.3, 176.0 ± 53.0, and 211.1 ± 76.5 mL/kg/min during low, normal, and high CO states, respectively. There was a significant effect of CI(BW) state on bias and relative bias with COmet (P<0.001 and P=0.003, respectively). Bias of the COmet method (± SD) was -116.6 (70.5), 20.1(76.4), and 91.3 (92.0) mL/kg/min at low, normal, and high CI(BW), respectively. Bias of the COfem (± SD) was -20.3 (19.0), 8.6 (70.9), and -2.9 (83.0) mL/kg/min at low, normal, and high CI(BW) , respectively. The mean relative bias for COfem was -6.7 ± 44% (limits of agreements: -81.2 to 67.9%). CONCLUSION: Compared with lithium dilution, the pulse contour analysis provides a good estimation of CO, but requires femoral artery catheterization in anesthetized dogs.

Determination of cardiac output in neonatal foals by ultrasound velocity dilution and its comparison to the lithium dilution method.

OBJECTIVE: To compare cardiac output (CO) measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in conditions of high, intermediate, and low CO in anesthetized foals. DESIGN: Original prospective study. SETTING: University teaching hospital. ANIMALS: Six foals 1-3 days of age (38-45 kg). INTERVENTIONS: Neonatal foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. The CO was measured by use of LiDCO and UDCO techniques. Measurements were obtained from each foal at baseline and during low, intermediate, and high CO states. Measurements were converted to cardiac index (cardiac index=CO/body weight) values for statistical analysis. Agreement between the 2 methods was determined using Bland and Altman analysis and concordance correlation coefficients. MEASUREMENTS AND MAIN RESULTS: LiDCO determinations of CO ranged between 4.0 and 14.0 L/min resulting in cardiac index ranging between 75.5 and 310 mL/kg/min. There was no significant effect of blood pressure variation on bias or relative bias (P=0.62 and 0.93, respectively). The mean bias and relative bias of UDCO (+/-SD) compared with LiDCO were -20.1+/-39.2 mL/kg/min and -7.7+/-23.4%, respectively. Concordance correlation coefficient between LiDCO and UDCO was 0.833. CONCLUSIONS: When compared with LiDCO, the UDCO technique has acceptable clinical utility for measuring CO in healthy anesthetized newborn foals.

Determination of cardiac output in anesthetized neonatal foals by use of two pulse wave analysis methods.

OBJECTIVE: To compare cardiac output (CO) measured by lithium arterial pressure waveform analysis (PULSECO) and CO measured by transpulmonary pulse contour analysis (PICCO) in anesthetized foals, with CO measured by use of lithium dilution (LIDCO) considered the criterion-referenced standard. SAMPLE POPULATION: 6 neonatal (1- to 4-day-old) foals that weighed 38 to 45 kg. Procedures-Foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. The CO was measured by use of PULSECO, PICCO, and LIDCO techniques. Measurements were converted to specific CO (sCO) values for statistical analysis. Measurements were obtained during low, intermediate, and high CO states. RESULTS: sCO ranged from 75.5 to 310 mL/kg/min. Mean +/- SD PICCO bias varied significantly among CO states and was -51.9 +/- 23.1 mL/kg/min, 20.0 +/- 19.5 mL/kg/min, and 87.2 +/- 19.5 mL/kg/min at low, intermediate, and high CO states, respectively. Mean PULSECO bias (11.0 +/- 37.5 mL/kg/min) was significantly lower than that of PICCO and did not vary among CO states. Concordance correlation coefficient between LIDCO and PULSECO was significantly greater than that between LIDCO and PICCO. The proportion of observations with a relative bias < +/- 30% was significantly lower with the PULSECO method than with the PICCO method. CONCLUSIONS AND CLINICAL RELEVANCE: Values for the PULSECO method were more reproducible and agreed better with values for the LIDCO method than did values for the PICCO method and were able to more accurately monitor changes in CO in anesthetized newborn foals.

An index of myocardial performance applied to the right ventricle of Boxers with arrhythmogenic right ventricular cardiomyopathy.

OBJECTIVE: To use an index of myocardial performance (IMP) to assess right ventricular function in Boxers with arrhythmogenic right ventricular cardiomyopathy (ARVC). ANIMALS: 22 Boxers (12 Boxers with ARVC diagnosed by the detection of > or = 1,000 ventricular premature complexes (VPCs)/24 h and 10 Boxers with < or = 5 VPCs/24 h (control dogs). Procedures-Pulsed-wave Doppler recordings of tricuspid inflow and pulmonic outflow were acquired. Preejection period (PEP), ejection time (ET), PEP/ET, and IMP were determined for the right ventricle by use of data from separate cardiac cycles. RESULTS: A significant difference was not identified between groups for right ventricular PEP, right ventricular ET, right ventricular PEP/ET, or right ventricular IMP. Right ventricular IMP was not significantly correlated with VPC number (r = 0.21) or VPC grade (r = -0.3) in Boxers with ARVC. CONCLUSIONS AND CLINICAL RELEVANCE: Boxers with ARVC did not have significant differences in right ventricular IMP, compared with results for control Boxers. This would suggest that right ventricular dysfunction does not develop in Boxers with ARVC or that a more severe phenotype of the disease may be necessary for detection of dysfunction. Additional studies that use more sensitive techniques to evaluate myocardial function may be warranted.

Effectiveness of (99m)Tc-tetrofosmin for assessment of heart functions in micropigs.

This study examined the suitability of a nuclear imaging technique using (99m)Tc-tetrofosmin as an agent to assess the heart functions of healthy micropigs. The mean age of the pigs was 360 days (male), and the mean body weight was 35.3 kg ranging from 34.5-36 kg. There were no significant perfusion defects in any of the reconstructed images. Gated single-photon emission computed tomography imaging can be used to calculate the ventricular volume and ejection fraction (EF). In this case, an EF of 79% was calculated from the ventricular volume of the end-systolic image (10 ml) subtracted from that of the end-diastolic volume (49 ml). A perfusion defect (particularly the apex, lateral wall) is unlikely because of the presence of a preserved wall motion in a segment with a defect. It is concluded that quantitative cardiac scintigraphy, using (99m)Tc-tetrofosmin is an adequate technique for estimating the heart functions of healthy micropigs.

Effects of isoflurane on Tei-index of myocardial performance in healthy dogs.

Recently, the Tei-index, a noninvasive index that combines systolic and diastolic time intervals, has been proposed to assess global cardiac performance. However, the effects of isoflurane on the Tei-index have not been characterized. This study aimed at studying the effects of 1.0 minimal alveolar concentration isoflurane anesthesia on the pre-ejection period (PEP), left ventricular ejection time (LVET), PEP/LVET ratio, isovolumic relaxation time (IVRT), stroke index (SI), cardiac index (CI), heart rate (HR), and the Tei-index in healthy unpremedicated dogs. We observed significant increases in PEP, PEP/LVET ratio, IVRT, and TEI, whose maximal increases obtained throughout the study were 47%, 48%, 78%, and 56%, respectively. The LVET and HR did not change significantly, whereas the SI and CI decreased during anesthesia (29% and 26%, respectively). In conclusion, isoflurane produced direct effects on the Tei-index. The changes in systolic and diastolic parameters were supportive of this finding and were consistent with an overall impairment of left ventricular function during anesthesia.