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Biomedical subjects

Igor Gregoric

Publications and source records attributed to Igor Gregoric.

15 recordsLinked to original sources
PubMed2006

Aortic wrap as a novel technique of type I endoleak repair.

Type I endoleak after endovascular abdominal repair is associated with a high risk of aneurysm expansion and rupture. Though type I endoleak can frequently be managed with endovascular techniques, in this report we describe a patient whose endoleak was refractory to multiple attempts at endovascular repair. The patient ultimately underwent a novel minimally invasive surgical repair with placement of an aortic wrap around the infrarenal aortic neck, successfully abolishing the endoleak.

Aged, 80 and over↗
PubMed2005

Lung cancer after heart transplantation: a 17-year experience.

BACKGROUND: The effects of heart transplantation on lung cancer incidence in heart transplant recipients are unclear. METHODS: In an observational study, we retrospectively reviewed the charts of all patients undergoing heart transplantation at our institution from July 1982 to July 1999. Data on lung cancer incidence, risk factors, treatment, and outcome were collected. RESULTS: Five hundred seventy-two patients (mean age, 50 +/- 11 years; range, 18 to 73) were considered at risk for lung cancer. Of these, 324 (57%) had a more than 20 pack-year history of smoking before transplantation. Lung cancer developed in 2 patients 1 year or less after transplantation and in 8 patients more than 1 year after transplantation (incidence, 2.2 per 1,000 patients per year of follow-up). Non-small cell lung cancer was diagnosed in all cases. Median survival was 10.8 months (range, 2 to 37.5). Routine annual chest radiographs after transplantation enabled early diagnosis in 5 cases (stages Ia and IIa), which correlated with better mean survival (28.1 months [range, 19 to 37.5] versus 5.1 months [range, 2 to 10.8]; p = 0.0002). CONCLUSIONS: The incidence of lung cancer in our population of heart transplant recipients appears to be no higher than in nontransplant populations with similar risk factors (ie, smoking and age). Routine radiographic imaging of transplant recipients may allow earlier detection of lung cancer and thus offer a survival benefit.

Adolescent↗
PubMed2005

Evaluation of myocardial function in patients with end-stage heart failure during support with the Jarvik 2000 left ventricular assist device.

In 2 patients with the Jarvik 2000 left ventricular assist device (LVAD), we assessed left ventricular systolic function through pressure-volume loops and E(max) at the beginning and end of the support period to potentially predict the possibility of pump removal without transplantation. Immediately before LVAD implantation and explantation, pressure and volume measurements were made with catheters and echocardiography, respectively, the E(max) being calculated from the slope of the pressure-volume loops, and the left ventricular ejection fraction (LVEF) being estimated by echocardiography. Transplantation was performed after 14 and 62 days, respectively, during which the LVEF increased by 75% (from 12% to 21%) in Patient 1 and remained unchanged (from 16% to 18%) in Patient 2, whereas the E(max) increased from 0.63 and 0.42 mm Hg/ml, respectively, to 1.31 and 1.07 mm Hg/ml, reflecting a 107% and 155% improvement. In these 2 cases, the E(max) was a more reliable indicator of intrinsic myocardial contractility than was the LVEF.

Cardiac Catheterization↗
PubMed2004

HeartMate vented-electric left ventricular assist system: technique for intrathoracic or intraperitoneal implantation via a left thoracotomy.

The HeartMate vented-electric left ventricular assist system (Thoratec Corp., Woburn, MA) has become widely accepted as a temporary bridge to transplantation. We describe a left thoracotomy technique in 3 patients for implanting this pump intrathoracically or intraperitoneally. In all 3 cases, long-term pump function was satisfactory. For HeartMate implantation, the left thoracotomy approach may be particularly useful when previous median sternotomies, coupled with the severe debilitation posed by chronic heart failure and hepatic dysfunction with resultant coagulopathy, would greatly increase the mortality and morbidity of a redo median sternotomy.

Cardiopulmonary Bypass↗
PubMed2004

Preclinical assessment of a trileaflet mechanical valve in the mitral position in a calf model.

BACKGROUND: The bileaflet valve is currently the mechanical replacement valve of choice. Though durable, it does not closely mimic native valve hemodynamics and remains potentially thrombogenic. METHODS: Prototype trileaflet valves (T1 and T2) were implanted in the mitral position in calves. Group I calves received either a T1 valve (n = 12) or a control bileaflet valve (n = 5); Group II, either a T2 valve (n = 7) or a control bileaflet valve (n = 5). Valve function, perivalvular leakage, and transvalvular pressure gradients were evaluated. Also, long-term prototype leaflet wear was evaluated in vivo in one Group I calf (502 days) and two Group II calves (385 and 366 days). Calves were euthanized and necropsied at study termination, and major organs weighed and examined. RESULTS: Valve function was excellent and hematologic parameters remained normal in all calves that survived to study termination. Mean peak transvalvular pressure gradients were 10 +/- 7 mm Hg for T1 valves, 6 +/- 3 mm Hg for T2 valves, and 12 +/- 4 mm Hg for bileaflet control valves. Clinically insignificant valvular regurgitation was observed in both prototypes. Explanted valves showed no thrombus-impaired leaflet motion, except in two T1-fitted calves and one T2-fitted calf. Major organs showed no evidence of clinically significant thromboembolic events. There were no other significant differences between the results of experimental and control groups. CONCLUSIONS: Prototype trileaflet valves performed safely and effectively in the mitral position in calves, even without long-term anticoagulation. This warrants their evaluation as an equivalent alternative to bileaflet valves.

Animals↗
PubMed2004

The total artificial heart: where we stand.

The AbioCor total artificial heart (TAH) is undergoing clinical feasibility testing as destination therapy in patients with end-stage congestive heart failure. So far, the device has been implanted in 11 of a projected 15 patients. The TAH has performed reliably, providing adequate circulatory support while extending survival and improving quality of life in most recipients. Thromboembolism remains a problem but is being addressed by optimizing device and patient management and refining the anticoagulation protocol. Because the device is totally implantable and requires no penetration of the skin, infection has been minimized. All recipients so far have been men. The device is large and this limits its use in smaller patients (i.e. women, small men and children). A smaller version is being developed. Although it has yet to receive Food and Drug Administration approval, the early clinical results suggest that the AbioCor TAH may become an accepted alternative to heart transplantation for selected patients with end-stage congestive heart failure. Further investigation with regard to its primary clinical applicability, i.e. as a rescue device for sudden catastrophic heart failure, is warranted.

Aged↗
PubMed2003

Continuous flow pumps and total artificial hearts: management issues.

Feasibility studies are underway for new axial flow ventricular assist systems and with a total artificial heart (TAH). The axial flow pumps provide continuous flow from the left ventricle (LV) to the aorta; the TAH provides pulsatile flow to the pulmonary and systemic circulation. Understanding the differences between these systems is necessary for appropriate patient selection and management. We compared the Jarvik 2000 axial-flow pump and the AbioCor TAH. The Jarvik 2000 pump is placed in the LV with its outflow graft anastomosed to the aorta. This system is used for bridge-to-transplantation and destination therapy. The AbioCor TAH provides complete circulatory support. The AbioCor is used for destination therapy in patients expected to die in less than 30 days. Worldwide, 45 patients have received the Jarvik 2000 as a bridge to transplantation (n = 34) or destination therapy (n = 11) for an average duration of support of 132.8 days (5 to 853 days). In 30 bridge-to-transplantation cases, 14 patients (47%) have undergone heart transplantation, 5 (17%) continue to be supported with the Jarvik 2000 device, and 11 (37%) have died. Five of 7 patients supported by the AbioCor TAH survived beyond the perioperative period; 4 were ambulatory, 2 were discharged from the hospital, and 1 is at home 13 months after implantation. Anticoagulation therapy and infection management are necessary for both systems. Therapy with inotropic agents, vasoactive drugs, a pacemaker, and electrolyte normalization is necessary for Jarvik patients. AbioCor-supported patients do not require medications to support heart function. Vasoactive agents may be useful for controlling blood pressure.

Heart Failure↗
PubMed2003

Dobutamine stress echocardiography predicts myocardial improvement in patients supported by left ventricular assist devices (LVADs): hemodynamic and histologic evidence of improvement before LVAD explantation.

BACKGROUND: Cardiac function may improve in patients with end-stage heart failure who receive long-term support (>30 days) with left ventricular assist devices (LVADs). Dobutamine stress echocardiography (DSE) has been used to quantitate myocardial recovery in patients with heart failure supported with LVADs. By recording the hemodynamic response with the use of DSE, we evaluated and applied the resulting data to patients receiving LVAD support. METHODS AND RESULTS: The study population included 16 patients who underwent LVAD implantation, regained functional capacity on full LVAD support, and tolerated decreased mechanical support with no worsening of dyspnea or fatigue. All 16 patients underwent dobutamine stress with increasing doses of dobutamine (from 5 to 40 mcg/kg/min). Hemodynamics and 2-dimensional (2-D) echocardiography was performed at each dose level. In addition, paired myocardial samples were obtained and analyzed histologically to determine myocyte size and collagen content. Dobutamine stress separated the study population into 2 groups: those who had favorable responses to dobutamine (9/16) and those who had unfavorable responses (i.e., experienced hemodynamic deterioration; 7/16). Favorable dobutamine responses were characterized by improved cardiac index, improved force-frequency relationship in the left ventricle (dP/dt), improved left ventricular ejection fraction, and decreased left ventricular end-diastolic dimension. All 9 favorable responders underwent LVAD explantation, and 6 survived for more than 12 months. In all patients studied, LVAD support resulted in decreased myocyte size (n = 14, 33.9 +/- 0.9 microm before vs 16.6 +/- 0.8 microm after support, p = 0.0001; normal, 5-15 microm) but resulted in no consistent changes in collagen content. CONCLUSIONS: Dobutamine stress echocardiography with hemodynamic assessment may be a useful tool in assessing physiologic improvement in myocardial function of patients with end-stage heart failure who receive LVAD support. It may help predict which patients can tolerate LVAD removal. Prospective analysis of cardiac function is now warranted to better define myocardial recovery in patients supported with LVADs.

Adult↗
PubMed2003

Off-pump coronary artery bypass grafting and transmyocardial laser revascularization via a left thoracotomy.

Off-pump coronary artery bypass grafting may be combined with adjunctive transmyocardial laser revascularization to optimize revascularization. This approach may be advantageous for high-risk patients, particularly those having undergone previous sternotomies. From October 2000 through May 2001, 17 patients (9 women and 8 men) underwent off-pump coronary artery bypass grafting and transmyocardial laser revascularization via a left thoracotomy. The patients had a mean age of 63 years and a mean ejection fraction of 0.33. All but 1 patient had undergone previous coronary surgery. In each patient, the heart was approached via a left thoracotomy through the 5th intercostal space, and 37 transmural channels, 1 mm in diameter, were each created with a single pulse of the carbon dioxide laser. Coronary artery bypass grafting was then performed with left internal thoracic artery or saphenous vein grafts. The follow-up period ranged from 2.1 to 9.3 months (mean, 6.2 months). The patients received 28 bypass grafts (mean, 1.6 grafts). Postoperatively, 2 patients required inotropic support. On day 8, 1 patient died of ventricular fibrillation. After a mean hospitalization of 7.7 days, the remaining patients were discharged, free of angina. At follow-up examination after a mean of 6 months (range, 2-9 months), 15 patients remained free of angina and one had mild angina. None had required further hospitalization. Performed via a left thoracotomy, off-pump coronary artery bypass grafting plus transmyocardial laser revascularization yielded an acceptable mortality rate, no major morbidity, and substantial angina relief in this carefully selected group of challenging, high-risk patients.

Adult↗
PubMed2002

Use of autologous auricular chondrocytes for lining artificial surfaces: a feasibility study.

BACKGROUND: Auricular elastic cartilage is a potential source of autologous cells for lining the luminal surfaces of cardiovascular prostheses. We tested this potential in vitro and in vivo using a left ventricular assist device (LVAD) and a calf model. METHODS: In vitro, auricular cartilage was harvested from the anesthetized ear of a calf, isolated, and cultured on tissue culture dishes. Primary chondrocytes were typed by immunocytochemistry, transferred into culture media, passaged twice, and seeded onto the blood-contacting luminal surfaces of four LVADs (HeartMate; Thoratec Corporation, Woburn, MA). Seeded cell linings were preconditioned under simulated flow conditions to promote cell adhesion to luminal surfaces. Seeding efficiency and cumulative cell loss under flow conditions were quantitated. In vivo, one of the four autologous chondrocyte-lined and preconditioned LVADs was implanted into the tissue-donor calf; run for 7 days; explanted; and evaluated grossly, by scanning electron microscopy, and by transmission electron microscopy. RESULTS: The efficiency of seeding chondrocytes onto the luminal surfaces of the four LVADs was 95.11% +/- 4.23% (n = 4). Cumulative cell loss during preconditioning under flow conditions in vitro did not exceed 12% (n = 4). After 7 days of in vivo implantation, the luminal surfaces of the implanted LVAD demonstrated an intact, strongly adherent cellular lining. CONCLUSIONS: Auricular elastic cartilage is a ready and easily accessible source of chondrocytes whose ability to produce collagen II and other important extracellular matrix constituents allows them to adhere strongly to the luminal surfaces of LVADs. The simple method of isolating and expanding auricular chondrocytes presented here could be used to provide strongly adherent autologous cell linings for LVADs and other cardiovascular devices. If and when chondrocytes can be genetically engineered to produce antithrombogenic factors and then used to line the luminal surfaces of LVADs or other cardiovascular prostheses, they may be able to improve the hemocompatibility of the blood-biomaterial interface in such devices. Our successful feasibility study in a calf model warrants further studies of this concept in vivo.

Animals↗
PubMedDate not supplied

Surgical treatment of congestive heart failure.

Cardiac transplantation is the definitive surgical treatment for patients with severe left ventricular dysfunction and congestive heart failure. Unfortunately, however, the supply of donor hearts remains severely limited, so transplantation is an option for only a minority of these patients. Even after being approved for a heart transplant, patients often have a long wait until a suitable donor heart can be found. This waiting period entails a significant mortality rate. Because the supply of donor hearts is not expected to increase, surgeons have introduced several alternatives to heart transplantation, including partial left ventriculectomy, mitral valve repair, myocardial revascularization, and endoventricular circular patch plasty. For maximal benefit, surgeons must refine the selection criteria for determining which patients are the best candidates for each of these procedures.

Heart Aneurysm↗
PubMedDate not supplied

Vascular thrombosis during support with continuous flow ventricular assist devices: correlation with computerized flow simulations.

Continuous flow pumps are increasingly used to treat severe heart failure. These pumps alter flow physiology by lowering pulsatility in the arterial circulation. In patients with peripheral stenosis, continuous flow pumps may lead to thrombosis of peripheral vessels, possibly predisposing to vascular thrombosis in areas of non-flow-limiting stenosis. The authors performed a computerized flow modeling simulation to analyze the effects of altered hemodynamics in a stenotic area. Drawing on previous clinical experience, we modeled a stenotic area in the common carotid artery. Computerized flow modeling revealed blood stagnation zones with low shear stress and velocity adjacent to the stenotic area during nonpulsatile flow. Such stagnation was not present during pulsatile flow. These results indicate a mechanism by which altered physiologic flow may accelerate occlusion of arterial conduits in patients with preexisting stenosis. This finding may be important for patients with continuous flow devices who have peripheral vascular disease; therefore, further study is warranted.

Blood Flow Velocity↗