Robert P. Gallegos

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; 5×106 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.

Effect of Cardiac Stem Cells on Left-Ventricular Remodeling in a Canine Model of Chronic Myocardial Infarction

Background— Regenerative medicine, including cell therapy, is a promising strategy for recovery of the damaged myocardium. C-kit–positive cardiac stem cells (CSCs) have been shown to improve myocardial function after ischemic injury in animal models and in early clinical experience. We used a chronic large animal model of myocardial infarction with substantial reductions in left-ventricular (LV) ejection fraction and adverse remodeling to examine the effect of late autologous CSC intramyocardial injection on long-term cardiac structure and function. Methods and Results— Thoracotomy and ligation of the proximal left anterior descending artery, additional diagonal branches, and atrial biopsy for CSC culture were performed in canines. Baseline cardiac MRI was performed at 6 weeks postinfarct followed by repeat thoracotomy for randomization to intramyocardial injection of CSCs (n=13) or vehicle alone (n=6). At 30 weeks postmyocardial infarction, repeat MRI was performed. Data were analyzed using nonparametric tests (Wilcoxon signed-rank and rank-sum tests). In control animals, LV end-systolic volume and end-diastolic volume increased from 6 to 30 weeks (median and interquartile range, 51.3 mL [43.3–57.4] to 76.1 mL [72.0–82.4]; P=0.03 and 78.5 mL [69.7–86.1] to 99.2 mL [97.1–100.4]; P=0.03). Left-ventricular ejection fraction declined further (35.2% [27.9–38.7] to 26.4% [22.0–31.0]; P=0.12). In the cell-treated animals, this late adverse LV remodeling was attenuated (LV end-systolic volume, 42.6 mL [38.5–50.5] to 56.1 mL [50.3–63.0]; P=0.01 versus control). There was a nonsignificant attenuation in the increase in LV end-diastolic volume (64.8 mL [60.7–71.3] to 83.5 mL [74.7–90.8]; P=0.14 versus control) and LV ejection fraction change over time differed (30.5% [28.4–33.4] to 32.9% [28.6–36.9]; P=0.04 versus control). Conclusions— Intramyocardial injection of autologous CSCs in a late phase model of chronic infarction resulted in less increase in LV end-systolic volume and preservation of LV ejection fraction.

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.

Animal Models for Cardiac Research

The modern era of cardiac surgery is largely considered to have begun in the animal research laboratories. Today, animal models continue to be used for the study of cardiovascular diseases and are required for the preclinical assessment of pharmaceuticals, mechanical devices, therapeutic procedures, and/or continuation therapies. This chapter was designed to provide readers and potential investigators with important background information necessary for the process of matching an experimental hypothesis to an animal species that will serve as an appropriate model for studying a specific cardiovascular disease or for testing a given medical device. A review of the current animal models used in cardiac research is provided and arranged by disease state. Critical factors to consider when choosing an appropriate animal model including cost, reproducibility, and degree of similarity of the model to human disease are discussed. Thus, this chapter can be utilized as a practical guide for planning of research protocols.

Giant Syphilitic Aortic Aneurysm

A 76-year-old man with a history of syphilis presented with progressive dyspnea and leg swelling. Auscultation of the precordium was notable for a diastolic blowing murmur of aortic regurgitation, and there was ECG evidence of left ventricular hypertrophy.

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.

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.

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

Abstract  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. (J Card Surg 2011;26:240‐243)

Post-partum coronary artery dissection.

A healthy 32-year-old female presented with NSTEMI 2 weeks following an uneventful pregnancy and caesarian section. Emergent cardiac catheterization demonstrated a non-stentable coronary artery dissection (Figs. 1 and 2, and Videos 1 and 2). She was treated with CABG (LIMA to LAD) and made an uneventful post-operative recovery. Fig. 1. RAO angiographic view showing the dissected LAD with diluted dye in the false lumen (arrows) and decreased caliber of the coronary true lumen (arrowheads). Fig. 2. RAO angiographic view showing the dissected LAD with residual dye in the false lumen (arrows).

Ethical Issues in Biomaterials and Medical Devices

This chapter focuses on the ethical principles that have been established and applied to the field of biomedical research and development. At the conclusion of this chapter, we describe a pathway for the development of a new prosthetic heart valve which will be used to illustrate the application of biomedical ethics as it applies today.