DILATED CARDIOMYOPATHY IN SLENDER-TAILED MEERKATS (SURICATA SURICATTA) UNDER HUMAN CARE.

Meerkats (Suricata suricatta) housed at two accredited zoological institutions in the United States were evaluated via echocardiography, thoracic radiography, and blood biomarkers-taurine and feline N-terminal pro-B-type natriuretic peptide-to determine the prevalence and severity of dilated cardiomyopathy (DCM) in both populations. In total, 24 meerkats were evaluated and 7 were diagnosed with DCM based on the following parameters: left ventricular internal diameter at end diastole > 1.30 cm, left ventricular internal diameter at end systole > 1.10 cm, and a fractional shortening of <18%. Echocardiographic parameters were identified and reported for normal and affected meerkats, whereas thoracic radiographs were not useful for screening for DCM. Meerkats with DCM were treated with pimobendan and/or benazepril and furosemide if indicated. Seven meerkats died during the study period, with the majority exhibiting myocardial fibrosis. Of the blood parameters tested, elevated taurine levels were associated with DCM. Further research is necessary to characterize the etiology of DCM in meerkats.

Contemporary Challenges for Veterinary Medical Education: Examining the State of Inter-Professional Education in Veterinary Medicine.

Educational training in professional programs forms the foundation for how a person problem-solves throughout their career. However, training focused on only one profession ignores the value realized through collaborations among multiple professions for solving health-related problems. This is at the core of inter-professional education (IPE). Effective IPE programs can result in inter-professional collaboration and translation science endeavors across the health sciences and beyond. Recent events such as the COVID-19 pandemic and the opioid crisis highlight the importance of veterinary medicine in advancing One Health through IPE. The prevalence of IPE programs in veterinary curricula, and the process by which these have been established, has not been widely described in the literature. Through an 18-question survey sent to associate deans (ADs) of 50 veterinary schools, we sought to determine the status of IPE in the veterinary curriculum. Thirty-nine schools agreed to participate, representing primarily United States Doctor of Veterinary Medicine public and private programs with some representation from Canadian, United Kingdom, and Australasian programs. Schools that provide IPE courses developed their programs in collaboration with other health sciences programs across the 4-year curriculum. The perceived barriers for IPE offerings were no different between schools with or without opportunities; however, a lack of faculty and student-perceived value and lack of adequate space in the academic schedule were common threads. Our findings provide a snapshot of the current state of IPE in veterinary medical curricula, with a particular emphasis on the United States, and point to areas of programmatic need for the field.

Assessing professionalism in health profession degree programs: A scoping review.

BACKGROUND: To identify and classify methods for assessing professionalism across health profession degree programs and identify gaps in the literature regarding types of assessments. METHODS: The authors conducted a scoping review of articles published from database inception through 24 January 2020. Included articles described an assessment approach for professionalism in health profession degree programs available in full-text in the English language. Articles were classified based on profession, timing of assessment, feedback type, assessment type, professionalism dimension, and Barr's modified Kirkpatrick hierarchy. RESULTS: Authors classified 277 articles meeting inclusion criteria. Most articles were from medical education (62.5%) conducted during didactic (62.1%) or experiential/clinical curriculum (49.8%). Few articles (15.5%) described longitudinal assessment. Feedback type was formative (32.2%) or summative (35%), with only 8.3% using both. Assessment types frequently reported included self-administered rating scales (30%), reflections (18.8%), observed clinical encounters (17.3%), and knowledge-based tests (13.4%). Ethical practice principles (65%) and effective interactions with patients (48.4%) were the most frequently assessed dimensions of professionalism. Authors observed balanced distribution among Barr's modified Kirkpatrick model at levels of reaction (38.3%), modification of perceptions and attitudes (33.6%), acquisition of knowledge and skills (39%), and behavioral change (36.1%). IMPLICATIONS: The classification scheme identified in current literature on professionalism assessment does not align with International Ottawa Conference Working Group on the Assessment of Professionalism recommendations. Gaps identified were limited description of professionalism assessment during admissions, infrequent longitudinal assessment, limited use of methods for both formative and summative assessment, and limited reports of assessments applicable to interprofessional education settings.

Functional Consequences of PDK4 Deficiency in Doberman Pinscher Fibroblasts.

A splice site mutation in the canine pyruvate dehydrogenase kinase 4 (PDK4) gene has been shown to be associated with the development of dilated cardiomyopathy (DCM) in Doberman Pinchers (DPs). Subsequent studies have successfully demonstrated the use of dermal fibroblasts isolated from DPs as models for PDK4 deficiency and have shown activation of the intrinsic (mitochondrial mediated) apoptosis pathway in these cells under starvation conditions. For this study, we sought to further explore the functional consequences of PDK4 deficiency in DP fibroblasts representing PDK4wt/wt, PDK4wt/del, and PDK4del/del genotypes. Our results show that starvation conditions cause increased perinuclear localization of mitochondria and decreased cell proliferation, altered expression levels of pyruvate dehydrogenase phosphatase (PDP) and pyruvate dehydrogenase (PDH), dramatically increased PDH activity, and an impaired response to mitochondrial stress in affected cells. In sum, these results show the broad impact of PDK4 deficiency and reveal mechanistic pathways used by these cells in an attempt to compensate for the condition. Our data help to elucidate the mechanisms at play in this extremely prevalent DP disorder and provide further support demonstrating the general importance of metabolic flexibility in cell health.

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.

Long-term incidence and risk of noncardiovascular and all-cause mortality in apparently healthy cats and cats with preclinical hypertrophic cardiomyopathy.

BACKGROUND: Epidemiologic knowledge regarding noncardiovascular and all-cause mortality in apparently healthy cats (AH) and cats with preclinical hypertrophic cardiomyopathy (pHCM) is limited, hindering development of evidence-based healthcare guidelines. OBJECTIVES: To characterize/compare incidence rates, risk, and survival associated with noncardiovascular and all-cause mortality in AH and pHCM cats. ANIMALS: A total of 1730 client-owned cats (722 AH, 1008 pHCM) from 21 countries. METHODS: Retrospective, multicenter, longitudinal, cohort study. Long-term health data were extracted by medical record review and owner/referring veterinarian interviews. RESULTS: Noncardiovascular death occurred in 534 (30.9%) of 1730 cats observed up to 15.2 years. Proportion of noncardiovascular death did not differ significantly between cats that at study enrollment were AH or had pHCM (P = .48). Cancer, chronic kidney disease, and conditions characterized by chronic weight-loss-vomiting-diarrhea-anorexia were the most frequently recorded noncardiovascular causes of death. Incidence rates/risk of noncardiac death increased with age in AH and pHCM. All-cause death proportions were greater in pHCM than AH (65% versus 40%, respectively; P < .001) because of higher cardiovascular mortality in pHCM cats. Comparing AH with pHCM, median survival (study entry to noncardiovascular death) did not differ (AH, 9.8 years; pHCM, 8.6 years; P = .10), but all-cause survival was significantly shorter in pHCM (P = .0001). CONCLUSIONS AND CLINICAL IMPORTANCE: All-cause mortality was significantly greater in pHCM cats due to disease burden contributed by increased cardiovascular death superimposed upon noncardiovascular death.

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.

Biologic variability of N-terminal pro-brain natriuretic peptide in adult healthy cats.

Objectives The biologic variability of N-terminal pro-brain natriuretic peptide (NT-proBNP) and its impact on diagnostic utility is unknown in healthy cats and those with cardiac disease. The purpose of this study was to determine the biologic variation of NT-proBNP within-day and week-to-week in healthy adult cats. Methods Adult cats were prospectively evaluated by complete blood count (CBC), biochemistry, total thyroxine, echocardiography, electrocardiography and blood pressure, to exclude underlying systemic or cardiac disease. Adult healthy cats were enrolled and blood samples were obtained at 11 time points over a 6 week period (0, 2 h, 4 h, 6 h, 8 h, 10 h and at weeks 2, 3, 4, 5 and 6). The intra-individual (coefficient of variation [CVI]) biologic variation along with index of individuality and reference change values (RCVs) were calculated. Univariate models were analyzed and included comparison of the six different time points for both daily and weekly samples. This was followed by a Tukey's post-hoc adjustment, with a P value of <0.05 being significant. Results The median daily and weekly CVI for the population were 13.1% (range 0-28.7%) and 21.2% (range 3.9-68.1%), respectively. The index of individuality was 0.99 and 1 for daily and weekly samples, respectively. The median daily and weekly RCVs for the population were 39.8% (range 17.0-80.5%) and 60.5% (range 20.1-187.8%), respectively. Conclusions and relevance This study demonstrates high individual variability for NT-proBNP concentrations in a population of adult healthy cats. Further research is warranted to evaluate NT-proBNP variability, particularly how serial measurements of NT-proBNP may be used in the diagnosis and management of cats with cardiac disease.

Aging in cats: Common physical and functional changes.

PRACTICAL RELEVANCE: Aged pets comprise a significant proportion of the small animal veterinarian's patient population; in the USA, for example, it was estimated that over 20% of pet cats were 11 years of age or older in 2011. Certain changes associated with aging are neither positive nor negative, but others are less desirable, associated with illness, changes in mobility or the development of unwanted behaviors. These changes can greatly affect the health and wellbeing of the cat and have a tremendous impact on the owner. CLINICAL CHALLENGES: Regular veterinary examinations are essential for evaluating the health of older patients and for providing owners with guidance regarding optimal care. With the exception of overt disease, however, it is difficult to definitively determine if a cat is displaying changes that are appropriate for age or if they reflect an abnormal process or condition. GOALS: This is the first of two review articles in a Special Issue devoted to feline healthy aging. The goals of the project culminating in these publications included developing a working definition for healthy aging in feline patients and identifying clinical methods that can be used to accurately classify healthy aged cats. This first review provides a thorough, systems-based overview of common health-related changes observed in cats as they age. EVIDENCE BASE: There is a paucity of research in feline aging. The authors have drawn on expert opinion and available data in both the cat and other species.

Evaluating aging in cats: How to determine what is healthy and what is disease.

PRACTICAL RELEVANCE: Many of the changes that occur with aging are not considered pathologic and do not negatively affect overall wellness or quality of life. Ruling out disease is essential, however, when attempting to determine whether an aged cat can be considered 'healthy'. A clear understanding of the normal and abnormal changes that are associated with aging in cats can help practitioners make decisions regarding medical management, feeding interventions and additional testing procedures for their aged patients. CLINICAL CHALLENGES: It can be difficult to determine if a cat is displaying changes that are appropriate for age. For example, healthy aged cats may have hematologic or serum biochemistry changes that differ from those of the general feline population. Assessment of behavioral health and cognitive changes, as well as auditory, olfactory and visual changes, can also be challenging in the aged patient. GOALS: This is the second of two review articles in a Special Issue devoted to feline healthy aging. The goals of the project culminating in these publications included developing a working definition for healthy aging in feline patients and identifying clinical methods that can be used to accurately classify healthy aged cats. This second review proposes criteria for assessing 'healthy aged cats'. EVIDENCE BASE: There is a paucity of research in feline aging. The authors draw on expert opinion and available data in both the cat and other species.

Incorporating Inter-Professional Education into a Veterinary Medical Curriculum.

Inter-professional education (IPE) is identified as an important component of health profession training and is listed in the accreditation requirements for many fields, including veterinary medicine. The goals of IPE are to develop inter-professional skills and to improve patient-oriented care and community health outcomes. To meet these goals, IPE relies on enhanced teamwork, a high level of communication, mutual planning, collective decision making, and shared responsibilities. One Health initiatives have also become integral parts of core competencies for veterinary curricular development. While the overall objectives of an IPE program are similar to those of a One Health initiative, they are not identical. There are unique differences in expectations and outcomes for an IPE program. The purpose of this study was to explore veterinary medical students' perceptions of their interprofessional experiences following participation in a required IPE course that brought together beginning health profession students from the colleges of medicine, dentistry, nursing, pharmacy, nutrition, public health and health professions, and veterinary medicine. Using qualitative research methods, we found that there is powerful experiential learning that occurs for both the veterinary students and the other health profession students when they work together at the beginning of their curriculum as an inter-professional team.

In vitro evaluation of mitochondrial dysfunction and treatment with adeno-associated virus vector in fibroblasts from Doberman Pinschers with dilated cardiomyopathy and a pyruvate dehydrogenase kinase 4 mutation.

OBJECTIVE: To compare mitochondrial oxygen consumption rate (OCR) of fibroblasts from Doberman Pinschers with and without dilated cardiomyopathy (DCM) and mutation of the gene for pyruvate dehydrogenase kinase isozyme 4 (PDK4) and to evaluate in vitro whether treatment with adeno-associated virus (AAV) vector (i.e., gene therapy) would alter metabolic efficiency. ANIMALS: 10 Doberman Pinschers screened for DCM and PDK4 mutation. PROCEDURES Fibroblasts were harvested from skin biopsy specimens obtained from Doberman Pinschers, and dogs were classified as without DCM or PDK4 mutation (n = 3) or with occult DCM and heterozygous (4) or homozygous (3) for PDK4 mutation. Fibroblasts were or were not treated with tyrosine mutant AAV type 2 vector containing PDK4 at multiplicities of infection of 1,000. Mitochondrial OCR was measured to evaluate mitochondrial metabolism. The OCR was compared among dog groups and between untreated and treated fibroblasts within groups. RESULTS: Mean ± SD basal OCR of fibroblasts from heterozygous (74 ± 8 pmol of O2/min) and homozygous (58 ± 12 pmol of O2/min) dogs was significantly lower than that for dogs without PDK4 mutation (115 ± 9 pmol of O2/min). After AAV transduction, OCR did not increase significantly in any group (mutation-free group, 121 ± 26 pmol of O2/min; heterozygous group, 88 ± 6 pmol of O2/min; homozygous group, 59 ± 3 pmol of O2/min). CONCLUSIONS AND CLINICAL RELEVANCE: Mitochondrial function was altered in skin fibroblasts of Doberman Pinschers with DCM and PDK4 mutation. Change in mitochondrial function after in vitro gene therapy at the multiplicities of infection used in this study was not significant.

ESTABLISHMENT OF ECHOCARDIOGRAPHIC PARAMETERS OF CLINICALLY HEALTHY FLORIDA MANATEES (TRICHECHUS MANATUS LATIROSTRIS).

A standardized echocardiographic technique was recently established for the Florida manatee (Trichechus manatus latirostris). There are no available published data on normal echocardiographic parameters in any Sirenian species. The purpose of this study was to report reference parameters for various echocardiographic measurements. These parameters are intended to serve as a comparison for future research into the prevalence of cardiac diseases in the manatee and to aid in diagnosing animals with suspected cardiac disease in rehabilitation facilities. Annual health assessments of free-ranging manatees in Crystal River National Wildlife Refuge, Florida, and pre-release health assessments of rehabilitated manatees at Tampa's Lowry Park Zoo permitted comparison of echocardiographic measurements in adult (n=14), subadult (n=7), and calf (n=8) animals under manual restraint.

Atrial septal pacing in small dogs: a pilot study.

OBJECTIVE: To determine the feasibility of atrial septal pacing via a delivery catheter-guided small non-retracting helix pacing lead. ANIMALS: Six healthy beagles (8.3-12.9 kg). METHODS: Using single plane fluoroscopic guidance, Medtronic(®) 3830 SelectSecure leads were connected to the atrial septum via Medtronic® Attain Select® II standard 90 Left Heart delivery catheter. Pacing threshold and lead impedance were measured at implantation. The Wenckebach point was tested via atrial pacing up to 220 paced pulses per minute (ppm). Thoracic radiographs were performed following implantation to identify the lead position, and repeated at 24 h, 1 month, and 3 months post-operatively. RESULTS: Macro-lead dislodgement occurred in two dogs at 24 h and in three dogs at one-month post-implantation. Lead impedance, measured at the time of implantation, ranged from 583 to 1421 Ω. The Wenckebach point was >220 ppm in four of the six dogs. The remaining two dogs had Wenckebach points of 120 and 190 ppm. CONCLUSIONS: This pilot study suggests the selected implantation technique and lead system were inadequate for secure placement in the atrial septum of these dogs. The possible reasons for inadequate stability include unsuitable lead design for this location, inadequate lead slack at the time of implantation and inadequate seating of the lead as evidenced by low impedance at the time of implantation. Other implantation techniques and/or pacing leads should be investigated to determine the optimal way of pacing the atria in small breed dogs that are prone to sinus node dysfunction.

Echocardiographic evaluation of clinically healthy Florida manatees (Trichechus manatus latirostris).

Antemortem studies pertaining to the manatee cardiovascular and cardiopulmonary systems are limited despite reports of cardiac disease in postmortem specimens. The objective of this project was to develop a technique for echocardiography in the Florida manatee (Trichechus manatus latirostris). Because of their unique anatomy, a ventral approach was employed by use of an echocardiography table designed specifically for this study. Fourteen clinically healthy, free-ranging and captive Florida manatees underwent echocardiography between the fall of 2011 and winter of 2012. Eight females and six males of various age categories were included in the study. Clear visualization of all valves and chambers was accomplished, and length and width measurements of the left atrium, peak aortic flow velocity, and ejection fraction percentage were calculated in most animals. Abnormalities observed during the study included atrioventricular regurgitation and severe right-atrial enlargement. Based on the results of this study, echocardiography in the Florida manatee is possible, which has both clinical and research implications in larger epidemiologic studies evaluating diseases of the cardiopulmonary and cardiovascular systems.

Procedure times, complication rates, and survival times associated with single-chamber versus dual-chamber pacemaker implantation in dogs with clinical signs of bradyarrhythmia: 54 cases (2004-2009).

OBJECTIVE: To compare procedure times and major and minor complication rates associated with single-chamber versus dual-chamber pacemaker implantation and with 1-lead, 2-lead, and 3-lead pacemaker implantation in dogs with clinical signs of bradyarrhythmia. DESIGN: Retrospective case series. ANIMALS: 54 dogs that underwent pacemaker implantation because of clinical signs of bradyarrhythmia. PROCEDURES: Medical records of dogs that received pacemakers between July 2004 and December 2009 were reviewed for information regarding signalment, diagnosis, pacemaker implantation, pacemaker type, complications, and survival time. Analyses were performed to determine significant differences in anesthesia time, procedure time, and outcome for dogs on the basis of pacing mode and number of pacing leads. RESULTS: 28 of 54 (51.9%) dogs received single-chamber pacemakers and 26 (48.1%) received dual-chamber pacemakers. Mean ± SD procedural time was significantly longer for patients with dual-chamber pacemakers (133.5 ± 51.3 minutes) than for patients with single-chamber pacemakers (94.9 ± 37.0 minutes), and procedure time increased significantly as the number of leads increased (1 lead, 102.3 ± 51.1 minutes; 2 leads, 114.9 ± 24.8 minutes; 3 leads, 158.2 ± 8.5 minutes). Rates of major and minor complications were not significantly different between dogs that received single-chamber pacemakers and those that received dual-chamber pacemakers or among dogs grouped on the basis of the number of pacing leads placed. CONCLUSIONS AND CLINICAL RELEVANCE: Although dual-chamber pacemaker implantation did result in increased procedural and anesthesia times, compared with single-chamber pacemaker implantation, this did not result in a higher complication rate.

How to perform combined cutting balloon and high pressure balloon valvuloplasty for dogs with subaortic stenosis.

Subvalvular aortic stenosis (SAS) is one of the most common congenital cardiac malformations in dogs. Unfortunately, the long term success rate and survival data following either open heart surgery or catheter based intervention has been disappointing in dogs with severe subaortic stenosis. Medical therapy is currently the only standard recommended treatment option. A cutting balloon dilation catheter has been used successfully for resistant coronary artery and peripheral pulmonary arterial stenoses in humans. This catheter is unique in that it has the ability to cut, or score, the stenotic region prior to balloon dilatation of the stenosis. The use of cutting balloon valvuloplasty combined with high pressure valvuloplasty for dogs with severe subaortic stenosis has recently been reported to be a safe and feasible alternative therapeutic option. The following report describes this technique, outlines the materials required, and provides some 'tips' for successful percutaneous subaortic balloon valvuloplasty.

Successful closure of left-to-right patent ductus arteriosus in three dogs with concurrent pulmonary hypertension.

Closure of reversed patent ductus arteriosus (PDA) is generally accepted to be contraindicated due to case based evidence of worsened outcomes, but little is known about closure of left-to-right PDA with concurrent pulmonary hypertension (PH). This report describes three dogs presenting with varying severity of PH and clinical signs, all with documented left-to-right PDA. The PDA was closed in each case; either by surgical ligation or transarterial device occlusion, and follow up was available for a minimum of 8 months. Every case had a successful outcome with improvement or resolution of PH and associated clinical signs.

Evaluation of pacing site in dogs with naturally occurring complete heart block.

OBJECTIVE: To compare left ventricular synchronization and systolic performance with transvenous pacing of the right ventricular apex (RVA), left ventricular free wall (LVF) or simultaneous pacing of the RVA and LVF (BiV). ANIMALS, MATERIALS AND METHODS: Seven canine patients with complete heart block. Prospective study evaluating effect of pacing site. Twenty four hours following implantation of transvenous BiV pacing systems, electrocardiograms and echocardiograms were assessed during pacing from the: (1) Right Atrial Appendage/RVA (RAA/RVA), (2) RAA/LVF, and (3) RAA/BiV. RESULTS: QRS duration was significantly shorter with BiV pacing versus LVF pacing (p<0.001), or RVA pacing (p<0.001). Echocardiographic indices of systolic performance fractional shortening (FS), ejection fraction (EF), cardiac output (CO) were significantly higher with BiV pacing than with pacing from the RVA (P=0.023, 0.006, and 0.002 respectively). Cardiac output, measured by the biplane Simpson's method, was higher with LVF versus RVA pacing (P=0.036). There was no difference in FS or EF when comparing LVF to RVA pacing. Tissue Doppler measurements of synchronization and systolic performance did not show any difference between pacing mode, but a significantly increased number of segments were seen to contract following aortic valve closure during LVF pacing (P=0.0268) and RVA pacing (P=0.0197) as compared to BiV pacing. CONCLUSIONS: Findings suggest that BiV pacing improves cardiac output and systolic performance versus RVA pacing. This improvement however, is not reflected in tissue Doppler indices of synchronization and systolic performance.