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Biomedical subjects

V Falk

Publications and source records attributed to V Falk.

At least 73 records · Page 4Linked to original sources
PubMed1999

Endoscopic coronary artery bypass grafting on the beating heart using a computer enhanced telemanipulation system.

OBJECTIVE: To develop a technique for computer enhanced endoscopic arterial bypass grafting on the beating heart in an experimental canine model. METHODS: Mongrel dogs (30-35 kg) were used. After single lung ventilation of the right lung was initiated the dogs were placed to the right. The videoscope and the end-effectors of the da Vinci telemanipulation system (Intuitive Surgical, Mountain View, CA) were introduced through three ports. Surgery was performed remotely from the console (motion scaling 3:1). After harvesting of the internal thoracic artery (ITA) and preparation of its distal end, the Endostab, a newly developed endoscopic stabilizer, was introduced through an additional port. The anterior wall of the heart was stabilized and the collateral branch (RC) of the left anterior descending artery (LAD) was ligated proximally and distally. The arteriotomy was made and the ITA-graft anastomosed to the RC. The animals were sacrificed and the grafts were checked for patency using bench angiography. RESULTS: In two of five dogs total endoscopic beating heart bypass grafting, including ITA harvest, stabilization, arteriotomy and performance of the anastomosis, was successfully performed using computer enhanced technology and a new endoscopic stabilizer. In two dogs the procedure was completed with femoro-femoral cardiopulmonary bypass (CPB) support on the beating or fibrillating heart, respectively. One dog expired due to VT. Hemodynamically, endoscopic stabilization was well tolerated. All four grafts were patent despite a target vessel diameter of less than 1 mm. CONCLUSION: The endoscopic stabilizer can sufficiently immobilize the heart to enable endoscopic beating heart coronary artery bypass grafting by means of a computer controlled instrumentation system.

Animals↗
PubMed1999

Comparison of MIDCAP versus conventional CABG surgery regarding pain and quality of life.

BACKGROUND: This prospective clinical trial focuses on pain and quality of life (QOL) after minimally invasive direct coronary artery bypass (MIDCAB) grafting versus conventional coronary artery bypass grafting (CABG). METHODS: Group A consisted of 65 consecutive MIDCAB patients using an anterolateral mini-thoracotomy and the "off-pump" technique. Group B consisted of 95 computer-matched patients who underwent conventional CABG with cardiopulmonary bypass (CPB). Pain was graduated using the visual analog scale (VAS), and the verbal rating scale (VRS) [Troidl 1990]. QOL was evaluated at the time of discharge and three months after surgery using modified Nottingham Health Questionnaires that separate physical, social, activity, emotional, pain, and sleeping conditions. RESULTS: Postoperative pain was higher after MIDCAB on postoperative day (POD) 1 (p< 0.002). From POD 4 onwards MIDCAB patients had less pain compared with the conventional group (p<0.04). MIDCAB patients required less pain medication from POD 4 onwards (p<0.05). QOL was significantly better in the MIDCAB group on POD 7 for physical (p< 0.038), activity (p< 0.016), pain (p< 0.041), and sleep (p<0.038) conditions. The three-month questionnaire showed significantly better levels for MIDCAB patients regarding physical (p< 0.03) and pain (p< 0.001) conditions, and a trend for activity (p< 0.08) and emotional (p<0.08) conditions. CONCLUSION: Compared to patients undergoing conventional surgery, MIDCAB patients suffer more pain in the first three postoperative days, probably as a result of the lateral thoracotomy. From POD 4 onwards, MIDCAB patients are significantly better, experiencing less pain and showing better physical, activity, and sleeping conditions even three months after surgery. This can be attributed to the absence of median sternotomy and/or the avoidance of cardiopulmonary bypass.

Aged↗
PubMed1998

Control of endoaortic clamp position during Port-Access mitral valve operations using transcranial Doppler echography.

The technique of computer-aided transcranial Doppler echography for continuous control of cerebral perfusion during minimally invasive mitral valve operations using the Port-Access system is described. Temporary displacement of the endoclamp in the aortic arch (brachiocephalic trunk, left carotid artery) is followed by cerebral embolic signals and a sudden decrease in the blood flow velocity in the middle cerebral arteries.

Aorta↗
PubMed1998

Minimally invasive coronary artery bypass grafting without cardiopulmonary bypass: early experience and follow-up.

BACKGROUND: There is renewed interest in coronary artery bypass grafting without cardiopulmonary bypass using the anterolateral minithoracotomy approach. We evaluated 209 patients who underwent minimally invasive direct coronary artery bypass grafting using an anterolateral minithoracotomy. The anastomosis was performed under direct vision on the beating heart without using cardiopulmonary bypass. METHODS: The procedure was performed using a 6- to 9-cm left (or right) anterolateral thoracotomy for internal thoracic artery graft harvesting and anastomosis. Different devices were used for local immobilization. In 195 patients a single internal thoracic artery to left anterior descending coronary artery bypass was performed, in 3 patients a single right internal thoracic artery to right coronary artery bypass, and in 11 patients the radial artery was used together with the internal thoracic artery as a T-graft. RESULTS: Conversion to sternotomy or cardiopulmonary bypass was necessary in 10 (4.7%) patients. Intraoperative myocardial infarction was observed in 4 patients (1.9%). Early postoperative redo operation was necessary in 5 patients (2.4%). Mortality was 0.47%. Postoperatively, 191 patients (91.3%) underwent angiography for graft patency control. The overall patency rate was 97.3%. Minor stenosis of the internal thoracic artery graft was observed in 18 patients (9.4%); moderate stenosis was observed in 5 patients (2.6%). Midterm angiographic follow-up after 6 months was performed in 58 patients. The patency rate was 98.2%. One patient with severe symptomatic stenosis (1.7%) underwent reoperation. CONCLUSIONS: With the help of the local immobilization systems off-pump coronary artery bypass grafting was safely performed through a minithoracotomy. The incidence of intraoperative and postoperative complications was low and follow-up showed good results. Thus, minimally invasive direct coronary artery bypass grafting is an excellent technique for arterial revascularization in patients having symptomatic left anterior descending coronary artery disease.

Adult↗
PubMed1998

Comparison of different anticalcification treatments for stentless bioprostheses.

BACKGROUND: New anticalcificant treatments have been developed because tissue calcification is a major contributing factor for bioprosthetic valve failure. METHODS: Aortic valve leaflet and aortic root tissue samples from stentless bioprostheses treated with No-React (Biocor, Belo Horizonte, Brazil), AOA (Medtronic freestyle, Minneapolis, MN), and BiLinx (St. Jude Medical, St. Paul, MN) were compared to a control group by subcutaneous implantation in 60 male weanling Sprague-Dawley rats. RESULTS: Calcium levels were in the range of 0.3 to 2.2 mg/g dry tissue at 3 and 12 weeks in all three treated aortic valve leaflet implants. The BiLinx treatment proved anticalcificant effectiveness on aortic root samples as well. There were statistically significant differences for valve leaflet tissue samples: No-React = AOA < BiLinx < < Control and for aortic root tissue samples: BiLinx < < AOA < Control = No-React. CONCLUSION: Calcification of aortic valve leaflets was significantly reduced by all new anticalcificant treatments. Inhibition of cellular calcification (BiLinx) resulted in additional reduction of aortic root calcification. Maximum anticalcificant properties upon both leaflet and aortic root is important as these are considered a functional unit in stentless bioprostheses.

Aluminum↗
PubMed1998

Minimally invasive port-access mitral valve surgery.

OBJECTIVES: This study evaluates the feasibility of video-assisted minimally invasive mitral valve surgery by means of the Port-Access system. The aim of the study was to minimize surgical access and to develop a video-assisted surgical technique. METHODS: The Port-Access system allows for closed chest endoluminal aortic clamping, cardioplegic arrest, and decompression of the heart. The mitral valve was either repaired (n = 28) or replaced (n = 23) in 51 patients by means of a minimally invasive approach through a right lateral minithoracotomy and under videoscopic guidance. RESULTS: Mean length of incision was 5.4 +/- 1.8 cm (range 3.8 to 8 cm). Mean duration of operation, cardiopulmonary bypass, and crossclamp time was 196 +/- 53, 133 +/- 52, and 72 +/- 27 minutes, respectively. Median intubation time was 25.5 hours (range 5 to 264 hours). Median duration of intensive care and hospital stay was 2 days (range 1 to 36 days) and 13 days (10 to 36 days), respectively. Hospital mortality was 9.8% (5/51). Overall morbidity was relatively high. In two patients acute retrograde aortic dissection led to conversion of the procedure. At follow-up (261 +/- 13 days), three patients required reoperation for paravalvular leakage. Baseline mean Duke activity index score was 19.3 +/- 11.3 before the operation and increased to 23.2 +/- 10 at 6 weeks' and 24.2 +/- 10.3 at 12 weeks' follow-up, respectively. CONCLUSION: The Port-Access system allows for video-assisted minimally invasive replacement and complex repair of the mitral valve through a right lateral minithoracotomy. However, morbidity and mortality associated with this novel technique were high.

Aged↗
PubMed1998

Conversion of complex neonatal Ebstein's anomaly into functional tricuspid or pulmonary atresia.

BACKGROUND: Ebstein's anomaly, due to failure of delamination of one or more leaflets of the tricuspid valve (TV), is associated with varying degrees of tricuspid regurgitation (TR) and dysplasia of the right ventricle (RV). Although refinement of tricuspid valvuloplasty and plication techniques have opened the way to a satisfactory outlook for the majority of older children and adults, Ebstein's anomaly presenting at neonatal age, secondary to ineffective forward flow into the pulmonary and systemic circulation, has a reported mortality rate of as high as 75%. In order to improve the dismal outcome in neonatal Ebstein's anomaly, we have strived for early univentricular palliation. PATIENTS AND METHODS: Univentricular repair was performed in five neonates (median age 5 days; range 2-14 days) with Ebstein's anomaly, ductal dependent pulmonary blood flow, severe TR, absence of forward flow across the pulmonary valve, and small left ventricular (LV) area due to right-to-left bowing of the ventricular septum and ineffective LV loading (median indexed LV area 10.5 cm2/m2). In addition, two neonates had moderate pulmonary regurgitation (PR), one with additional pulmonary stenosis. In all patients, the indexed area of the combined right atrium and atrialized RV was greater than that of the combined functional RV, left atrium, and left ventricle (median 22.0 and 20.8 cm2/m2, respectively). The median preoperative systemic oxygen tension was 35 mmHg and the median pH 7.28. Repair consisted of TV closure with a pericardial patch (with the coronary sinus draining into the RV) (n = 3) or, in the presence of PR, resection of the dysplastic TV and division and oversewing of the main pulmonary artery (n = 2), as well as excision of the atrial septum, resection of redundant right atrial wall, and construction of an aortopulmonary shunt (n = 5). RESULTS: The median indexed LV area increased from 10.5 to 18.8 cm2/m2 as a result of more effective loading of the left ventricle. There was no intraoperative or late mortality. The patients were extubated at a median of 7 days postoperatively. At discharge, the median systemic oxygen tension was 46 mmHg. In all five patients, at 6, 7, 10, 12 and 16 weeks of age, a bidirectional cavopulmonary anastomosis has been constructed. CONCLUSIONS: In neonates with Ebstein's anomaly and ductal dependent pulmonary blood flow, rational palliation consists of the surgical creation of tricuspid atresia or, in the additional presence of PR or pulmonary stenosis, the creation of pulmonary atresia. These procedures may result in effective LV decompression and more effective volume loading of the left ventricle with increase of systemic output and improved clinical outcome.

Aorta↗
PubMed1998

Less-invasive coronary artery bypass grafting: different techniques and approaches.

OBJECTIVE: The aim of this study was to compare four different techniques for less-invasive coronary artery bypass surgery with and without cardiopulmonary bypass (CPB) in terms of feasibility as well as in terms of the intra- and postoperative course. METHODS: One hundred and fourteen patients were divided into four groups, according to the surgical technique. Group I: minithoracotomy, internal thoracic artery (ITA) harvesting and anastomosis under direct vision using cardiopulmonary bypass (CPB) on the fibrillating heart (n = 31). Group II: sternotomy and beating heart without CPB (n = 13). Group III: MIDCAB with CPB and cardioplegic cardiac arrest using endo-aortic balloon-occlusion, Port Access system (n = 9). Group IV: MIDCAB on the beating heart without CPB (n = 61). In total, 104 single and ten double graft procedures were performed using the radial artery T-graft technique in seven cases (groups III and IV). RESULTS: Harvesting of the ITA graft took 41+/-16.2 min in group I and could be reduced to 31+/-8.3 min in group IV by the use of a specially-designed retractor. Complications were: death (n = 1, group I), myocardial infarction, (n = 1, group I), early occlusion of the graft (n = 1, group IV), early stenosis of the anastomosis (n = 2, groups I and IV), late stenosis of the anastomosis (n = 1, group IV), thrombosis of the femoral vein (n = 1, group III). Postoperative ventilation, ICU and hospital stay were similar among groups. CONCLUSIONS: Based on our results, the following strategy has been developed: MIDCAB without CPB is the preferred technique for one-vessel graft procedures to the left anterior descendens (LAD) or RCA. The Port Access system (with CPB) is reserved as a second option for young patients requiring multiple-vessel grafting to the left coronary circulation (LAD/CX) and as a backup to avoid conversion. Sternotomy and an off-pump technique is used for single-vessel or multiple-vessel graft procedures in selected patients (emergency procedure, acute myocardial infarction, in the very obese).

Algorithms↗
PubMed1998

S-shaped in comparison to L-shaped partial sternotomy for less invasive aortic valve replacement.

OBJECTIVE: Evaluation of less invasive aortic valve replacement to minimize surgical trauma and achieve a better postoperative quality of life. METHODS: Thirty-three patients had aortic valve replacement using a 4-6 cm small incision and partial sternotomy only. Partial sternotomy was performed proximal (16), S-shaped (14) or horizontal (3). Access for cardiopulmonary bypass was via sternotomy (24) or the right femoral vessels (9). Patient age was 58+/-13 years, 21 had aortic stenosis and 12 aortic incompetence. RESULTS: Surgical exposure was sufficient and allowed for uncomplicated AVR in all patients. Mechanical valves (20), conventional bioprostheses (3), stentless bioprostheses (9) or a homograft (1) were implanted. Crossclamp time was not prolonged in comparison to the conventional technique. Intensive care stay and hospital stay were 1 and 10 days, respectively. One patient had to be reoperated for paravalvular leakage, two patients (horizontal sternotomy) had sternal dehiscence. Postoperative pain was low in most patients. CONCLUSION: Less invasive aortic valve replacement is feasible with good functional results. The S-shaped sternotomy approach is advantageous whereas the horizontal sternotomy is no longer performed due to a high rate of instability. This new technique will be further evaluated in comparison to the conventional approach.

Aortic Valve↗
PubMed1998

An experimental approach to quantitative thermal coronary angiography.

Thermal coronary angiography is a noninvasive but not yet quantitative method to intraoperatively assess graft patency in CABG surgery. Aim of this study was to quantify graft flow by measuring perfusion-induced myocardial temperature changes over time. Saphenous vein grafts to the left anterior descending artery were perfused at flow rates of 16-105 ml/min with warm saline. A thermal scanner with a 256 x 256 focal-plane array detector providing a spatial resolution of 1.2 mrad was used. The resulting temperature curves were averaged and a non-linear fit procedure was performed to calculate the time constant (tau) at each flow rate. An increase of myocardial temperature along the LAD with different flow rates could be demonstrated. There was an excellent correlation between the calculated time constant and actual flow (r = 0.96, p < 0.0002). By determining the time constant for different flow rates an estimate of actual graft flow is possible using thermal coronary angiography. Clinical studies have to show if the time constant can be used as a predictor of graft flow in patients.

Animals↗
PubMed1998

Changes of leukocyte subsets in coronary artery bypass surgery: cardiopulmonary bypass versus 'off-pump' techniques.

BACKGROUND: The use of cardiopulmonary bypass (CPB) in coronary bypass grafting is associated with a generalized inflammatory response. This negative impact of CPB may be avoided by using new surgical techniques recently introduced to perform coronary bypass grafting 'off-pump', i.e. without CPB. METHODS: Since the specific effects of CPB on the immunorelevant cells have still not been fully investigated, we measured the changes in leukocyte subsets of the circulating blood in patients who underwent coronary bypass surgery with a conventional sternotomy approach and CPB (group A, n = 10), in patients who underwent the same surgical procedure but without CPB (group B, n = 10), and in patients who underwent a minimally invasively performed single bypass to the left anterior descending artery (LAD) (group C, n = 10). RESULTS: Leukocyte subsets showed a similar change during and after coronary bypass grafting in all three groups. The total number of leukocytes was increased soon after reperfusion in the CPB group. A similar but delayed increase was observed in both off-pump groups. Changes in lymphocyte subsets and T-lymphocyte subsets were similar in all three groups, with a drop of lymphocytes during the first 24 postoperative hours mainly caused by a drop of T4-helper cells. CONCLUSION: The results indicate a reaction of the leukocyte subsets to coronary bypass surgery which is more related to the surgical trauma in general than to CPB in particular.

Aged↗
PubMed1998

Extracardiac repair versus intracardiac baffle repair of complex unroofed coronary sinus.

Complex unroofed coronary sinus with a persistent left superior vena cava has as its commonest major associated intracardiac anomaly a partial or complete atrioventricular canal defect. In this clinical setting, biventricular repair with construction of a complex intra-atrial baffle from the pulmonary veins to the mitral valve has a reported mortality rate of as high as 50%. Looking for an improvement, we have carried out an extracardiac repair of the anomalous systemic venous component with atrial septation. In 2 infants (aged 7 and 12 weeks) with unroofed coronary sinus, bilateral superior venae cavae, right isomerism, and complete atrioventricular canal, in addition to patch closure of the ventricular component of the atrioventricular septal defect, a baffle was constructed between the pulmonary veins and the mitral valve. In four subsequent infants (aged 7,10,16, and 20 weeks) with unroofed coronary sinus, bilateral superior venae cavae, complete atrioventricular canal, right isomerism (n = 2), and mild infundibular stenosis (n = 1), repair consisted of end-to-side anastomosis of the left superior vena cava to the right superior vena cava and complete repair of the atrioventricular canal and associated conditions. There was no mortality. The early postoperative course in the two patients with intra-atrial baffle was characterized by increased left-atrial pressure (18 and 20 mm Hg), with varying degrees of pulmonary venous congestion, supraventricular tachycardias, and systemic hypotension. The pulmonary venous congestion increased, so that one patient was successfully converted 10 weeks postoperatively to an extracardiac repair with septation of the atria and the other will probably follow. In the 4 patients with a primary extracardiac repair, the hemodynamic result was excellent, with a median left-atrial pressure of 11 mm Hg on the first postoperative day. At a median follow-up of 12 months, all 5 patients with an extracardiac repair are clinically well with widely patent anastomoses between the left and right superior venae cavae. The extracardiac repair technique for complex unroofed coronary sinus, as opposed to the intra-atrial baffle repair, avoids creation of a small and low-compliance left-atrial compartment with the potential for development of pulmonary venous congestion.

Cardiac Surgical Procedures↗
PubMed1997

Low-grade intimal hyperplasia in internal mammary and right gastroepiploic arteries as bypass grafts.

BACKGROUND: Knowledge is limited regarding the histology of the internal and right gastroepiploic arteries that have been functioning as coronary artery bypass conduits. METHODS: Four internal mammary arteries, 3 right gastroepiploic arteries, and 1 saphenous vein graft that had been functioning as coronary artery bypass grafts were harvested and examined histologically in 3 male patients who had died at 19, 38, and 47 months after coronary revascularization. RESULTS: All grafts were patent. The mean thicknesses of the intima in the proximal, middle, and distal segments were 41.0, 31.8, and 25.8 microns for the internal mammary artery and 58.0, 40.3, and 34.3 microns for the right gastroepiploic artery. The saphenous vein graft showed severe focal atherosclerosis. CONCLUSIONS: This histologic study in a small number of patients corroborates the reported excellent patency rates at medium- to long-term follow-up of the internal mammary and right gastroepiploic arteries used as coronary artery bypass grafts.

Aged↗