Pilot study investigating the feasibility of mitral valve repair without aortic cross-clamping and cardioplegia.

There is evidence that perfusing the heart with a heart and lung machine is less injurious than cross-clamping the aorta and administering cardioplegia during cardiac surgery. Although mitral valve replacement has been carried out without aortic cross-clamping and cardioplegia, it has been stated that cross-clamping is necessary in order to maintain visualization and a motionless surgical field for mitral valve repair. The purpose of this study was to determine the surgical feasibility of mitral valve repair without cross-clamping the aorta and using cardioplegia. Our hypothesis was that a completely bloodless and motion-free field would not be necessary to carry out mitral valve repair with annuloplasty and synthetic chordae tendineae sutures. Papillary muscles, chordae tendineae, annulus, and mitral valve leaflets were all readily visualized. Chordae tendineae sutures were used and annuloplasty was conducted without visual obstruction or motion interference. Our results show that mitral valve repair is feasible without cross-clamping the aorta and using cardioplegia.

Des évidences existent que la perfusion du coeur avec une machine coeur-poumon artificielle est moins dommageable que le clampage de l'aorte et une cardioplégie lors de chirurgie cardiaque. Bien que le remplacement de valvules mitrales ait été réalisé sans clampage de l'aorte et cardioplégie, il a été mentionné que le clampage est nécessaire afin de maintenir une visualisation et un champ chirurgical sans mouvement pour la réparation de valvule mitrale. Le but de la présente étude était de déterminer la faisabilité chirurgicale de réparation de la valvule mitrale sans clampage de l'aorte et en utilisant la cardioplégie. Notre hypothèse était qu'un champ avec absence complète de sang et sans mouvement ne serait pas nécessaire pour effectuer une réparation de la valvule mitrale avec annuloplastie et sutures avec des cordages tendineux synthétiques. Les muscles papillaires, les cordages tendineux, l'annulus, et les feuillets de la valve mitrale étaient tous facilement visualisables. La suture des cordons tendineux fut utilisée et l'annuloplastie menée sans aucune obstruction visuelle ou interférence par les mouvements. Nos résultats suggèrent que la réparation des valvules mitrales est faisable sans clampage de l'aorte et sans cardioplagie.(Traduit par Docteur Serge Messier).

Evaluation of left ventricular dimension and systolic function by standard transthoracic echocardiography before and 24-hours after percutaneous closure of patent ductus arteriosus in 120 dogs.

One hundred and twenty dogs were enrolled to value the effect of loading condition changes on left ventricular volumes before and 24-hours after the patent ductus arteriosus (PDA) occlusion by Amplatzer Canine Duct Occluder (ACDO) using standard echocardiography. The animals were divided in pure breed (n. 94) and mixed breed (n. 26); subsequently, the pure breed dogs were divided on the basis of the size of the breed of belonging in 3 groups (small size n. 36; medium size n. 8; large size n. 50). Moreover, the animals were divided in three classes based on their age: until 6 months; 6-12 months; over 12 months. A significant reduction of all the examined parameters (left ventricle internal diameter at end-diastole-LVIDd; left ventricle internal diameter at end-systole-LVIDs; end-diastolic volume-EDV; end-systolic volume-ESV; end-diastolic volume index-EDVI; end-systolic volume index-ESVI; fractional shortening-FS) was observed after ductal closure. Twenty-four hours after the closure, the evaluation of the relative percentage difference (RPD) of the echocardiographic parameters showed a significant reduction, higher in small size breed than in large size breed dogs. No significant difference related to breed size was observed only for RPD_FS variable. A significant interaction effect, between breed size and age classes, was observed only for RPD_EDVI (F = 3.39; p = 0.039). Until six months of age there was no significant difference in RPD_EDVI reduction, but over 6 months a significant reduction between small size and large size breed dogs at 24-hours from the occlusion was observed. In conclusion, our data seem to indicate that small breed dogs show a greater tolerance to congenital volume overload than large breed dogs, and this finding could be justify a delay of PDA closure in order to simplify the interventional procedure.

Prevalence of major complications and procedural mortality in 336 dogs undergoing interventional cardiology procedures in a single academic center.

INTRODUCTION: Overall complication rates associated with a wide range of diagnostic and therapeutic interventional cardiac procedures in a contemporary academic setting have not been reported. ANIMALS, MATERIALS AND METHODS: Consecutive interventional procedures performed for client-owned dogs were retrospectively analyzed to characterize procedural complications and mortality. RESULTS: Three hundred sixty-four procedures were performed on 336 dogs. Interventions included attempted or completed transvenous pacemaker (PM) implantation (n = 134) with subsequent pacing system revision (n = 8), pulmonic balloon valvuloplasty (BVP) (n = 117) with a subset of patients undergoing an additional BVP (n = 14), transarterial closure of left-to-right shunting patent ductus arteriosus (PDA) (n = 66), diagnostic angiography and/or cardiovascular pressure measurement (n = 9), transvenous temporary pacing (n = 7), septal defect occlusion (n = 5), heartworm extraction (n = 3), and BVP catheter fragment retrieval (n = 1). The prevalence of major perioperative and postoperative complications for all procedures was 5% and 6%, respectively, and the procedural mortality rate was 2%. The overall rate of major complications was 12% for the PM group, 11% for the BVP group, and 2% for the PDA occlusion group. Both PM implantation and BVP have higher rates of major complications overall compared with PDA occlusion (p=0.0151). CONCLUSIONS: The results of this study indicate that the prevalence of major complications and mortality associated with interventional cardiac procedures is low; however, significant differences exist in complication rates between procedures.

Cardiac Interventions in Small Animals: Areas of Uncertainty.

There remain areas of uncertainty in optimal technique, preferred candidates, and expected outcome for small animal patients undergoing cardiac intervention. This article highlights issues within interventional cardiology that are in need of study and offers the author's opinion and experience on topics such as variants of pulmonary valve anatomy and alternatives to conventional balloon dilation for pulmonary valve stenosis, patient selection for cutting or high-pressure balloon dilation of aortic valvar or subaortic stenosis, occlusion of patent ductus arteriosus in very small dogs, ductal stenting in conditions with reduced pulmonary blood flow, and alternative considerations for vascular access and closure.

Interventional Cardiology: What's New?

Interventional cardiology in veterinary medicine continues to expand beyond the standard 3 procedures of patent ductus arteriosus occlusion, balloon pulmonary valvuloplasty, and transvenous pacing. Opportunities for fellowship training; advances in equipment, including high-resolution digital fluoroscopy, real-time 3-dimensional transesophageal echocardiography, fusion imaging, and rotational angiography; ultrasound-guided access and vascular closure devices; and refinement of techniques, including cutting and high-pressure ballooning, intracardiac and intravascular stent implantation, septal defect occlusion, transcatheter valve implantation, and hybrid approaches, are likely to transform the field over the next decade.

Electrical velocimetry for noninvasive cardiac output and stroke volume variation measurements in dogs undergoing cardiovascular surgery.

OBJECTIVE: To compare electrical velocimetry (EV) noninvasive measures of cardiac output (CO) and stroke volume variation (SVV) in dogs undergoing cardiovascular surgery with those obtained with the conventional thermodilution technique using a pulmonary artery catheter. STUDY DESIGN: Prospective experimental trial. ANIMALS: Seven adult Beagle dogs with a median weight of 13.6 kg. METHODS: Simultaneous, coupled cardiac index (CI; CO indexed to body surface area) measurements by EV (CIEV) and the reference pulmonary artery catheter thermodilution method (CIPAC) were obtained in seven sevoflurane-anaesthetized, mechanically ventilated dogs undergoing experimental open-chest cardiovascular surgery for isolated right ventricular failure. Relationships between SVV or central venous pressure (CVP) and stroke volume (SV) were analysed to estimate fluid responsiveness. Haemodynamic data were recorded intraoperatively and before and after fluid challenge. RESULTS: Bland-Altman analysis of 332 matched sets of CI data revealed an overall bias and precision of - 0.22 ± 0.52 L minute-1 m-2 for CIEV and CIPAC (percentage error: 30.4%). Trend analysis showed a concordance of 88% for CIEV. SVV showed a significant positive correlation (r2 = 0.442, p < 0.0001) with SV changes to a volume loading of 200 mL, but CVP did not (r2 = 0.0002, p = 0.94). Better prediction of SV responsiveness (rise of SV index of ≥ 10%) was observed for SVV (0.74 ± 0.09; p = 0.014) with a significant area under the receiver operating characteristic curve in comparison with CVP (0.53 ± 0.98; p = 0.78), with a cut-off value of 14.5% (60% specificity and 83% sensitivity). CONCLUSIONS AND CLINICAL RELEVANCE: In dogs undergoing cardiovascular surgery, EV provided accurate CO measurements compared with CIPAC, although its trending ability was poor. Further, SVV by EV, but not CVP, reliably predicted fluid responsiveness during mechanical ventilation in dogs.

Complication rates associated with transvenous pacemaker implantation in dogs with high-grade atrioventricular block performed during versus after normal business hours.

BACKGROUND: Transvenous pacemaker implantation in dogs is associated with a relatively high complication rate. At our institution, pacemaker implantation in dogs with high-grade atrioventricular block (HG-AVB) frequently is performed as an after-hours emergency. HYPOTHESIS: Among dogs with HG-AVB, the rate of major complications is higher when pacemakers are implanted after hours (AH) compared to during business hours (BH). ANIMALS: Client-owned dogs with HG-AVB that underwent transvenous pacemaker implantation between January 2002 and December 2012 at the North Carolina State University Veterinary Teaching Hospital. METHODS: Retrospective medical record review. Two-year follow-up was required for complications analysis. RESULTS: Major complications occurred in 14/79 dogs (18%) and included lead dislodgement, lead or generator infection, lead or generator migration, and pacing failure. Incidence of major complications was significantly higher AH (10/36, 28%) compared to BH (4/43, 9%; P = .041), and all infectious complications occurred AH. Median survival time for all dogs was 27 months and did not differ between AH and BH groups for either all-cause (P = .70) or cardiac (P = .40) mortality. AH dogs were younger than BH dogs (P = .010), but there were no other clinically relevant differences between BH and AH groups in terms of demographic, clinical, or procedural variables. CONCLUSIONS AND CLINICAL IMPORTANCE: At our institution, AH transvenous pacemaker placement is associated with a higher rate of major complications (especially infections) compared to BH placement. This difference may be because of a variety of human factor differences AH versus BH.

A percutaneous fetal cardiac catheterization technique for pulmonary valvuloplasty and valvulotomy in a mid-gestation lamb model.

OBJECTIVE: We aimed to assess the feasibility of using a percutaneous transhepatic cardiac catheterization technique to perform fetal pulmonary valvuloplasty and valvulotomy under ultrasound guidance at mid-gestation. METHOD: In 13 mid-gestation fetal lambs without cardiac pathology, percutaneous transhepatic cardiac catheterization was used to position a coronary angioplasty catheter within the pulmonary valve. The balloon was inflated/deflated several times, simulating pulmonary valvuloplasty. In another two fetal lambs, a guidewire tip was positioned against the pulmonary valve, and unipolar diathermy was applied to simulate perforation of an atretic valve. RESULTS: Percutaneous access followed by right heart catheterization was successful in all cases. One fetus died following right ventricle perforation. Simulated pulmonary valvuloplasty was successful in nine cases using catheters with 6-mm-long balloons but unsuccessful in two cases (both survived) using 12-mm-long balloons. In one case, the catheter could not be inserted as the cannula became dislodged. Diathermy of the pulmonary valve was successful in both attempts. CONCLUSION: We successfully simulated in utero perforation and dilation of the pulmonary valve using percutaneous transhepatic access in fetal lambs. The technique has potential for clinical translation into treatment for human fetuses with critical pulmonary stenosis or pulmonary atresia with intact ventricular septum.

Isolation and excision of murine aorta; a versatile technique in the study of cardiovascular disease.

Cardiovascular disease is a broad term describing disease of the heart and/or blood vessels. The main blood vessel supplying the body with oxygenated blood is the aorta. The aorta may become affected in diseases such as atherosclerosis and aneurysm. Researchers investigating these diseases would benefit from direct observation of the aorta to characterize disease progression as well as to evaluate efficacy of potential therapeutics. The goal of this protocol is to describe proper isolation and excision of the aorta to aid investigators researching cardiovascular disease. Isolation and excision of the aorta allows investigators to look at gross morphometric changes as wells as allowing them to preserve and stain the tissue to look at histologic changes if desired. The aorta may be used for molecular studies to evaluate protein and gene expression to discover targets of interest and mechanisms of action. This technique is superior to imaging modalities as they have inherent limitations in technology and cost. Additionally, primary isolated cells from a freshly isolated and excised aorta can allowing researchers to perform further in situ and in vitro assays. The isolation and excision of the aorta has the limitation of having to sacrifice the animal however, in this case the benefits outweigh the harm as it is the most versatile technique in the study of aortic disease.

Direct blood pressure monitoring in laboratory rodents via implantable radio telemetry.

The ability to monitor and record precise blood pressure fluctuations in research animals is vital to research for human hypertension. Direct measurement of blood pressure via implantable radio telemetry devices is the preferred method for automatic collection of chronic, continuous blood pressure data. Two surgical techniques are described for instrumenting the two most commonly used laboratory rodent species with radiotelemetry devices. The basic rat procedure involves advancing a blood pressure catheter into the abdominal aorta and placing a radio transmitting device in the peritoneal cavity. The mouse technique involves advancing a thin, flexible catheter from the left carotid artery into the aortic arch and placing the telemetry device under the skin along the animal's flank. Both procedures yield a chronically instrumented model to provide accurate blood pressure data from an unrestrained animal in its home cage.

Measuring kidney function in conscious mice.

Mice lacking or over-expressing a gene of experimental interest have become important tools to understand the regulation of kidney function and water and electrolyte homeostasis. The use of mice in physiological studies is becoming more widespread, but there are still a number of technical limitations that preclude the full utilization of mouse models in renal research. The present chapter focuses upon a set of methods developed in our laboratory to quantify renal function in conscious mice. These measurements are based upon surgical instrumentation of mice with chronic indwelling arterial and venous catheters. This preparation permits direct measurement of arterial blood pressure, direct sampling of arterial and/or venous blood, intravenous or intra-arterial infusion of substances, and quantification of daily sodium balance. The advantage of these techniques is that all of these procedures can be performed in conscious mice freely moving in their home cages. As such, this in vivo preparation provides an assessment of physiological function in mice in their native state.

Mouse surgical models in cardiovascular research.

Mouse models that mimic human diseases are important tools for investigating underlying mechanisms in many disease states. Although the demand for these models is high, there are few schools or courses available for surgeons to obtain the necessary skills. Researchers are usually exposed to brief descriptions of the procedures in scientific journals, which they then attempt to reproduce by trial and error. This often leads to a number of mistakes and unnecessary loss of animals. This chapter provides comprehensive details of three major surgical procedures currently employed in cardiovascular research: aortic constriction (of both ascending and transverse portions), pulmonary artery banding, and myocardial infarction (including ischemia-reperfusion). It guides the reader through the entire procedure, from the preparation of the animal for surgery until its full recovery, and includes a list of all necessary tools and devices. Due consideration has been given to the pitfalls and possible complications in the course of surgery. Adhering to our recommendations should improve reproducibility of the models and bring the number of the animal subjects to the minimum.

Transcatheter atrial septal defect closure with the Amplatzer atrial septal occluder in 13 dogs: short- and mid-term outcome.

BACKGROUND: Transcatheter atrial septal defect (ASD) closure in the dog was first reported in 2005. OBJECTIVES: Describe the technique and both short- and mid-term outcome of transcatheter ASD closure with the Amplatzer atrial septal occluder (ASO). ANIMALS: Thirteen client-owned dogs with ASD. METHODS: Records of the initial 13 dogs in which transcatheter ASD closure was attempted at Texas A&M University were reviewed. RESULTS: All dogs had hemodynamically relevant septum secundum ASD. Two dogs had concurrent congenital abnormalities. ASOs were deployed in 13 dogs and released in 12. Eleven were released by a right jugular approach and 1 by a transatrial approach through a right lateral thoracotomy. Transthoracic echocardiographic estimates of ASD size were 14.0 + or - 5.4 mm (mean + or - 1 standard deviation) with a range of 7-22 mm. Accidental right atrial release occurred in 1 dog and embolization after release occurred in 2 dogs. Transcatheter ASD closure was successful in 10 dogs. Transthoracic color Doppler echocardiography the day after ASD closure indicated complete occlusion in 5 dogs, trivial to mild residual shunting in 4 dogs, and moderate residual shunting in 1 dog. Follow-up echocardiograms (mean of 12.4 + or - 7.4 months postprocedure) were available for 9 dogs. There was no residual ASD shunting in 6 dogs. In 3 of the 5 dogs with postoperative residual shunting it was judged to be decreased and hemodynamically unimportant relative to the dogs' postoperative evaluations. The mean length of event-free survival in the 10 dogs that underwent successful transcatheter ASD closure was 22.2 + or - 10.2 months.

Refinement of in vivo surgical procedures for cardiac gene and cell transfer in rats.

In studies of gene and cell transfer for the treatment of heart disease, direct intramyocardial injection and antegrade intracoronary injection are common methods of delivering biomaterials to the heart. The authors, who carried out these surgical procedures in 377 rats, describe their methodology in detail and discuss surgical refinements that substantially reduced rat mortality. These refinements include a rigorous fluid replacement regimen, use of inhalational anesthesia instead of injectable agents, exposure of the heart without direct contact and use of a chest drainage cannula to remove air from the pleural cavity and prevent lung collapse.

Surgical correction of cor triatriatum dexter in a dog under extracorporeal circulation.

A shiba inu dog with marked abdominal distension was diagnosed with cor triatriatum dexter and surgical correction was performed under extracorporeal circulation. The total duration of cardiac arrest was 11 minutes and total perfusion time was 34 minutes. The dog had an uneventful postoperative recovery. Postoperative contrast radiography of the caudal vena cava revealed normal flow into the right heart. Abdominal distension was no longer observed. Although several methods have been used to treat cor triatriatum dexter in dogs, the authors consider surgical correction under extracorporeal circulation to be a reliable approach.

[In contrast to captopril and enalapril, losartan does not increase mortality of gerbils after carotid ligation]. / Contrairement au captopril et à l'énalapril le losartan n'augmente pas la mortalité de la gerbille après ligature carotidienne.

OBJECTIVE: To check wether the deleterious effect of enalaprilat administered before unilateral caroid ligation in the gerbil reported by Fernandez et al. (J Cardiovasc Pharmacol 1994; 24: 937) is not a molecule specific effect but an angiotensin converting enzyme inhibitor class effect. DESIGN AND METHOD: Survival rate of gerbils (an animal with incomplete Willis hexagona) was measured after unilateral carotid ligation with preadministration (2 hours before by gavage) of saline (0.75 ml) (n = 37); losartan (20 mg/kg) (n = 37), enalaparil (10 mg/kg) (n = 37); a combination of losartan and enalapril at the same dose (n = 37); and of captopril (75 mg/kg) (n = 35). RESULTS: The survival rate of the gerbils 72 hours after carotid ligation was 65% in control, 62% in losartan, 30% in enalapril, 32% in enalapril + losartan, and 32% in captopril groups. Statistical analysis (log rank test) of the Kaplan-Meier survival curves over 72 hours showed no difference between losartan and controls nor between the various groups treated with ACEI. However survival was significantly lower in the ACEI groups than in the group treated by losartan alone (p < 0.02) or controls (p < 0.02). Intraaortic mean arterial pressure was measured in 6 controls, 6 animals treated with losartan and 6 other treated with enalapril. It was comparable in the losartan and enalapril treated animals (65 +/- 2 mm Hg vs 64 +/- 2) but significantly lower than in the controls (77 +/- 2 mmHg) (p < 0.02). CONCLUSIONS: In contrast to oral preadministration of enalapril and captopril that of losartan does not increase the mortality of the gerbil after unilateral carotid ligation in spite of the same decrease in systemic blood pressure. Although a lower mortality than in controls was not observed with losartan as in the princeps study of Fernandez, these data are consistent with the demonstration by this author that angiotensin II plays a critical protective role in acute ischemia probably by promoting collateral circulation recruitment through non-AT1 receptors stimulation.