Functionally competent cardiac stem cells can be isolated from endomyocardial biopsies of patients with advanced cardiomyopathies.

RATIONALE: Two categories of cardiac stem cells (CSCs) with predominantly myogenic (mCSC) and vasculogenic (vCSC) properties have been characterized in the human heart. However, it is unknown whether functionally competent CSCs of both classes are present in the myocardium of patients affected by end-stage cardiac failure, and whether these cells can be harvested from relatively small myocardial samples. OBJECTIVE: To establish whether a clinically relevant number of mCSCs and vCSCs can be isolated and expanded from endomyocardial biopsies of patients undergoing cardiac transplantation or left ventricular assist device implantation. METHODS AND RESULTS: Endomyocardial biopsies were collected with a bioptome from the right side of the septum of explanted hearts or the apical LV core at the time of left ventricular assist device implantation. Two to 5 biopsies from each patient were enzymatically dissociated, and, after expansion, cells were sorted for c-kit (mCSCs) or c-kit and KDR (vCSCs) and characterized. mCSCs and vCSCs constituted 97% and 3% of the c-kit population, respectively. Population doubling time averaged 27 hours in mCSCs and vCSCs; 5×10(6) mCSCs and vCSCs were obtained in 28 and 41 days, respectively. Both CSC classes possessed significant growth reserve as documented by high telomerase activity and relatively long telomeres. mCSCs formed mostly cardiomyocytes, and vCSCs endothelial and smooth muscle cells. CONCLUSIONS: The growth properties of mCSCs and vCSCs isolated from endomyocardial biopsies from patients with advanced heart failure were comparable to those obtained previously from larger myocardial samples of patients undergoing elective cardiac surgery.

The Sutureless Biological Bentall Procedure: A New Technique to Create a Modular Valve-Conduit Construct.

The Perceval sutureless valve (Corcym, Saluggia, Italy) has been effectively adopted by surgeons for the treatment of degenerative aortic valve stenosis. Its simplified true sutureless implantation technique has proven useful for minimally invasive cases, but the use of Perceval as part of more complex root replacement has not previously been described. We present a novel technical modification to the manufactured biologic Bentall, called the sutureless biological Bentall. This technique allows for a true modular valve-conduit construction that will simplify future reintervention.

Transmural atrial fibrosis after epicardial and endocardial argon-powered CryoMaze ablation.

BACKGROUND: The CryoMaze procedure is usually limited to endocardial ablation under cardio-pulmonary bypass. Epicardial ablation is considered inferior as endocardial islets of atrial tissue could theoretically remain viable, protected from cryoinjury by epicardial fat and endocardial circulating warm blood. Novel argon-powered cryoprobes with lower ablation temperatures have recently become available. It is unclear if these instruments can reliably induce transmural atrial fibrosis by epicardial cryoablation on the beating heart. METHODS: Ten sheep were divided into two equal groups. CryoMaze ablations were applied using an argon-powered cryoprobe with an ablation temperature of -185°C. In the control group, standardized ablations (n = 50) were applied endocardially under cardiopulmonary bypass. In the experimental group, corresponding ablations (n = 50) were applied epicardially on the beating heart. Postoperatively the animals were monitored for 30 days. At necropsy, the lesions were explanted and analyzed histologically for evidence of transmural fibrosis. RESULTS: Two animals in the control group and one animal in the experimental group died prematurely. Autopsy of the remaining animals showed that all lesions (n = 70) had retained their structural integrity. In the control group, histology demonstrated transmural fibrosis in 94% (28/30) of the endocardially applied lesions. In the experimental group, histology demonstrated transmural fibrosis in 95% (38/40) of the epicardially applied lesions. Statistical analysis revealed no significant difference between the two groups (p = 0.96). CONCLUSION: Argon-powered epicardial cryoablation on the beating heart is as efficient in inducing transmural fibrosis as the traditional technique of endocardial ablation under cardio-pulmonary bypass.

Cardiac hemangioma presenting with angina pectoris.

A 60-year-old female presented with a two-year history of exertional chest pain and progressive dyspnea. Resection of a cardiac hemangioma arising from the area of the bifurcation of the left anterior descending and circumflex coronary arteries resulted in complete resolution of her symptoms. The symptoms were likely caused by coronary steal.

Development of a sheep model of atrial fibrillation for preclinical prosthetic valve testing.

Currently, prosthetic heart valve testing is performed on animal models with no underlying cardiovascular pathologies. Unfortunately, unforeseen adverse events may occur when heart valves tested in animals in normal sinus rhythm are implanted in patients suffering from arrhythmias. For example, the Medtronic Parallel valve functioned well in pre-clinical testing, but a high rate of thromboembolic complications appeared when the valve was placed in patients with atrial fibrillation (AF). Given the increasing number of patients afflicted with AF, an animal model of the disorder is needed to more accurately predict a valve's function in the clinical setting. Among methods available for inducing AF, electrophysiological pacing is the most practiced, but the challenges associated with pacing have led to the development of alternative methods of inducing AF These methods include gene transfer and a pharmacologic approach with acetylcholine and catecholamines. Finally, although stem cells have been widely investigated in terms of their therapeutic benefits, the use of their well-reported pro-arrhythmic behavior shows great promise for the development of an AF model in sheep. Such a model would have the potential for detecting adverse outcomes with mechanical heart valves before implantation in the clinical setting.

In-vivo experience with the Triflo trileaflet mechanical heart valve.

BACKGROUND AND AIM OF THE STUDY: The in-vivo performance of the Triflo trileaflet mechanical valve was evaluated in an ovine model. The aim of long-term follow up was to gather site-specific performance data demonstrating device safety, as required for regulatory approval of this new valve design, prior to its use in clinical trials. METHODS: The Triflo trileaflet valve was implanted in 26 sheep using 29-mm mitral (n=8; animal body weight 63.3 +/- 10.3 kg, age 112.0 +/- 30.7 weeks) or 21-mm aortic mechanical valves (n=19; body weight 73.0 +/- 4.36 kg, age 112.6 +/- 23.6 weeks) using standard techniques. Animals were allocated to 150- or 365-day survival cohorts. The 150-day cohort was further subdivided into mitral valve (n=6) and aortic valve (n=11) implants. The 365-day cohort was organized into aortic (n=7) and mitral (n=2) implants. Angiography, echocardiography, and pathology were performed to assess valve performance. RESULTS: Angiographically monitored pressure measurements for the trileaflet mitral valve at 150 and 365 days were within established ranges in terms of mean aortic pressure, systolic and diastolic aortic pressure, and left ventricular end-diastolic pressure. In animals receiving a mitral valve the transvalvular gradient was 3.5 +/- 0.71 mmHg at 365 days, and 0.2 +/- 0.4 mmHg at 150 days. The Triflo mitral valve had only mild (physiologic) regurgitation. Cardiac output was within normal limits in animals receiving the Triflo valve in the aortic position. Laboratory values reflected no ongoing infection or destruction of blood cells as a result of device implantation. No significant abnormality was noted at necropsy in any animal, except for evidence of thromboembolic events in the kidneys (4-20%). Pathological evaluation was reflected by mild to moderate fibrous tissue formation at the inflow orifice (n=15), and minimal growth was observed in the outflow tract of one valve. This was consistent with that seen in sheep implanted with a standard St. Jude Medical bileaflet valve. CONCLUSION: The study results showed the Triflo valve to perform to safety levels comparable with those of the standard St. Jude Medical bileaflet design, when implanted in the aortic and mitral positions. Additional analysis of historic control data suggested that the trileaflet valve design may offer a reduction in outflow tract obstruction by allowing for a greater effective orifice area index when compared to an equal-sized-orifice bileaflet valve. Notably, the Triflo valve was associated with a statistically significant reduction in myocardial hypertrophy, further reducing the potential for patient-prosthesis mismatch. Overall, the Triflo valve appeared to more closely emulate the hemodynamic properties of the native tissue valve than the traditional bileaflet design. Hence, the trileaflet design may offer the function of a tissue valve while retaining the durability of the mechanical valve.

Rat intubation and ventilation for surgical research.

Effective outcomes in cardiothoracic surgical research using rodents are dependent upon adequate techniques for intubation and mechanical ventilation. Multiple methods are available for intubation of the rat; however, not all techniques are appropriate for survival studies. This article presents a refinement of intubation techniques and a simplified mechanical ventilation setup necessary for intrathoracic surgical procedures using volatile anesthetics. The procedure is defined and complications of the procedure are elucidated that provide a justification for animal numbers needed for initiating new studies. Lewis rats weighing 178-400 g (287 +/- 44) were anesthetized using Enflurane and intubated with a 16-G angiocatheter using transillumination. Mechanical ventilation (85 bpm, 2.5 mL TV, enflurane 1.5-2%) maintained adequate sedation for completion of an intrathoracic procedure. Complications of the intubation and ventilation included mortality from anesthetic overdose, intubation difficulty, pneumothorax, traumatic extubation, and ventilation disconnection. Anesthetic agents and their related effects on the rat heart and reflexes are compared. This article also underscores the importance of refinement, reduction, and replacement in the context of cardiothoracic surgery using rodent models.

The current state of in-vivo pre-clinical animal models for heart valve evaluation.

For over 30 years, animal models have remained a central critical component in the pre-clinical safety evaluation of prosthetic heart valves developed for use in humans. Though many advances have been made in valve design, no ideal replacement prosthesis has yet been developed. As a result, valve manufacturers continue to address issues relating to thrombogenicity, structural integrity, fluid dynamics and calcification in their designs. Many animal models have been developed to examine these issues, including dog, pig, calf and sheep, yet no standard model has been accepted. Recently, the International Standard Organization has provided guidelines in document 5840 to address cardiovascular implants. The aim of this report is to provide a summary of the current state of pre-clinical valve evaluation in animals. Changes in ISO 5840 will be addressed that have occurred between 1998 and the present date, and the role of current available animal models. The aim also is to provide rational guidance in the selection of appropriate animal models to match the purpose of valve implantation studies.

The basic science aspect of donor heart preservation: a review.

In cardiac transplantation, the transport time between harvest and recipient is limited by the viability of the donor heart. The problem of viability is a consistent limitation in cardiac transplantation. Since the 1960s, techniques, including hypothermia, perfusion, oxygenation, and hyperbaria, have been used to prolong the preservation of the transplantable heart. Continuing development of cardioplegic solutions has minimized edema and oxygen radical formation, which have resulted in extension of the donor heart viability. New research into the events leading to necrosis, oncosis, and apoptosis may allow further advancement of protective cardioplegic solutions in combination with technology of transporting the heart. With a prolonged preservation time there is potential to increase the donor pool and ultimately improve post-operative outcomes.

Recurrent post-partum coronary artery dissection.

Coronary artery dissection is a rare but well-described cause for myocardial infarction during the post-partum period. Dissection of multiple coronary arteries is even less frequent. Here we present a case of recurrent post-partum coronary artery dissections. This unusual presentation poses unique problems for management. A 35 year-old female, gravida 3 para 2, presented with myocardial infarction 9 weeks and 3 days post-partum. Cardiac catheterization demonstrated left anterior descending (LAD) dissection but an otherwise normal coronary anatomy. The lesion was treated with four everolimus eluting stents. Initially the patient made an unremarkable recovery until ventricular fibrillation arrest occurred on the following day. Unsynchronized cardioversion restored a normal sinus rhythm and repeat catheterization revealed new right coronary artery (RCA) dissection. A wire was passed distally, but it was unclear whether this was through the true or false lumen and no stents could be placed. However, improvement of distal RCA perfusion was noted on angiogram. Despite failure of interventional therapy the patient was therefore treated conservatively. Early operation after myocardial infarction has a significantly elevated risk of mortality and the initial dissection had occurred within 24 hours. This strategy proved successful as follow-up transthoracic echocardiography after four months demonstrated a preserved left ventricular ejection fraction of 55-60% without regional wall motion abnormalities. The patient remained asymptomatic from a cardiac point of view.

Functional paraganglioma of the middle mediastinum.

We describe a 49-year-old woman with refractory hypertension resulting from a functional paraganglioma of the middle mediastinum. After aggressive medical antihypertensive control and reduction of catecholamine production, she underwent surgical resection requiring transection and subsequent reconstruction of the aorta on cardiopulmonary bypass and circulatory arrest. We believe that this is the first report of a functionally active paraganglioma of the mediastinum requiring resection with cardiopulmonary bypass and aortic reconstruction.

Selection of prosthetic heart valves.

Cardiovascular surgery for the repair or replacement of diseased heart valves has continually improved since its introduction in the early 1960s. Despite advances in prosthetic heart valve design, to date there is no valve that is comparable to the native human valve with respect to durability, risk of thrombosis, and overall hemodynamic function. Although bioprosthetic devices are similar to the native valve with respect to thrombogenicity, durability is a significant concern, particularly in younger patients. Approximately 45% of implanted bioprosthetic valves fail at 10 years. In contrast, mechanical prostheses have a significantly lower incidence of structural failure, with an implantation life of greater than 20 years, and are thus more often used for patients under the age of 65. Unfortunately, significant hemodynamic and thrombotic issues have yet to be resolved with the latest generation of mechanical valves. Thus, careful analysis of patient factors and valve-related complications must be considered when treatment of heart valve disease is offered to the patient. The purpose of this review is to discuss the current recommendations for surgical intervention for heart valve disease.

Evaluation of perfusion and viability in hypothermic non-beating isolated porcine hearts using cardiac MRI.

The donor heart undergoes degradation during hypothermic storage. An assessment of donor heart preservation is typically done with histological or biochemical methods that are not feasible in the clinical setting. We describe a method to study the donor heart using cardiac perfusion MRI that is potentially feasible for clinical use. Standard cardiectomy was performed in the pig model and the hearts were stored in normal saline at 5 degrees C. Imaging was performed by using a rapid gradient-echo sequence (FLASH) with saturation-recovery preparation for T1-weighting in the short axis and horizontal long axis views. Approximately 80 serial images were acquired at a rate of 1/s during administration of 0.006 mmol/ml Gd-DTPA (500 ml, 1 l/min). Signal intensity vs. time curves were generated for each heart and slice imaged and compared to a 0.006 mmol/ml Gd-DTPA reference. H&E stained biopsies of the LV, RV, and septum were also obtained. The mean duration of heart storage (N=10) was 8.8 h (range 4.2-19.2 h). Histologically, no differences were seen in H&E stained biopsies among hearts at different storage times. However cardiac MRI revealed a decrease in perfusion units in each subsequent heart tested after 4.2 h. (R=0.49). Average peak up-slope was used as a surrogate measure for flow capacity through the microvasculature and peak contrast enhancement was used as a measurement of viable microvasculature. The 4 h heart had 83% peak contrast enhancement of the reference standard, as compared to 44% for the 19.2 h heart. The decrease in peak enhancement is directly related to the duration of storage time. No correlation of peak up-slope of the intensity curve to storage time was found. This new application of cardiac MRI in the donor heart is applicable to: (1) assessing marginal hearts, (2) evaluating donor heart preservation techniques, and (3) correlating pre- to post-transplant viability.

Cardiac MRI in the isolated porcine heart reveals possible etiology of sudden right heart failure following heart transplantation.

Occurrence of immediate post-transplant heart failure in the cardiac transplant recipient is typically attributed to elevated pulmonary vascular resistance, however other etiologies may play a role. At the completion of the transplant, free air, which has collected in the donor heart, is vented via an aortotomy. Free air may rise into the right coronary artery and obstruct reperfusion of the right ventricle. Cardiac perfusion MRI may offer a method of non-invasively determining the presence of air embolus. The objectives in the pilot study were to identify steps in the donor process where free air could enter into the aortic root causing obstruction of perfusion of the coronary arteries. A change in surgical technique could then be used to eliminate a portal of entry and cardiac perfusion MRI could validate the technique. Standard cardiectomy was compared to a variation in technique in two animals. Pulmonary vein ligation was completed in the experimental model before completion of cardiectomy. Both hearts were isolated and imaged using T1-weighted FLASH sequence and gadolinium contrast via the aortic root. Cardiac perfusion MRI imaging of the heart with the unligated pulmonary vein revealed evidence of air embolus and no perfusion of the right coronary artery compared to the ligated heart. Anatomically, the right coronary artery is anterior in the mediastinum compared to the left coronary artery. Air emboli preferentially rise into the right coronary and can obstruct flow into the right heart. Cardiac perfusion MRI offers an effective method to evaluate the isolated pre-transplant heart for perfusion defects.

Infarct extent by MRI correlates with peak serum troponin level in the canine model.

BACKGROUND: Serum Troponin I is used routinely as an adjunct to EKG for the diagnosis of myocardial infarction (MI); however, a correlation between marker level and infarct size has yet to be documented in vivo. We report findings from a chronic coronary artery ligation model in the canine (n = 12) in which peak Troponin I is related to infarct size as determined by high-resolution cardiac magnetic resonance imaging. METHODS: All animals underwent a left anterior thoracotomy to allow for ligation of the left anterior descending artery. Evidence of myocardial infarction, including EKG changes, elevated Troponin I, along with visual reduction in perfusion and wall motion, was noted in all animals. Thirty days after surgical intervention, cine MRI and contrast-enhanced MRI were performed. Dedicated analysis software was used to quantify global infarction size, LV function and to map regions of MI to a 3D model of the left ventricle. RESULTS: A linear relationship between infarct extent and peak Troponin I level exists (r = 0.98, P < 0.0001). In addition, we observed a negative trend between infarct extent, peak Troponin I, and ejection fraction. CONCLUSION: The findings of this study indicate that Troponin I and cardiac magnetic resonance imaging provide a more accurate estimation of infarct size than was previously reported using markers with less sensitivity and imaging modalities of lower spatial resolution and viability imaging capability.