Torsion dynamics in the evolution from acute to chronic mitral regurgitation.

BACKGROUND AND AIM OF STUDY: Left ventricular (LV) torsion reduces transmural fiber strain gradients during systole, and torsional recoil in early diastole is thought to assist LV filling. To test the hypothesis that deterioration of torsional dynamics accompanied LV dysfunction during the evolution of mitral regurgitation (MR), torsion was measured during the progression from acute to chronic MR in a canine model. METHODS: Seven dogs underwent cardiopulmonary bypass for LV marker placement and creation of MR by disrupting the posterior leaflet. After 7-10 days, three-dimensional marker coordinates were measured with biplane videofluoroscopy to study LV geometry, size and function, plus maximal torsional deformation, time of maximal torsion relative to end-ejection, and early diastolic torsional recoil during the first 5% of filling. After three months, the animals were re-studied. RESULTS: Progression from acute to chronic MR was associated with a significant decrease in maximum LV dP/dt (1,574+/-213 to 1,300+/-252 mmHg/s, p <0.01) and an increase in LVEDP from 11+/-5 to 15+/-5 mmHg (p <0.01). After three months of MR, maximum torsional deformation decreased from 6.3+/-1.9 to 4.7+/-2.0 degrees (p = 0.04), as did early diastolic recoil (-3.8+/-1.0 to -1.5+/-1.7 degrees, p = 0.03). CONCLUSION: Progression from acute to chronic MR is accompanied by decreased and delayed systolic LV torsional deformation and a decline in early diastolic recoil, which may contribute to LV dysfunction by increasing transmural strain gradients during systole and impairing diastolic filling. As torsional deformation and recoil can be measured non-invasively with MRI in humans, such measurements might prove useful in patients with progressive MR as an adjunct to determine the timing of surgical repair.

Influence of three-dimensional vision on surgical telemanipulator performance.

BACKGROUND: Different viewing conditions (two- and three-dimensional National Television Standard Committee [2D-NTSC and 3D-NTSC] and two-dimensional high-definition television [2D-HDTV]) on telemanipulator performance were evaluated. METHODS: Six taskes were performed by 15 endoscopic surgeons using the daVinci telemanipulation system. Performance time and errors were measured. Encoder data from the system were used for kinematic analysis of motion. A self-evaluation questionnaire regarding performance under various viewing conditions was obtained. RESULTS: Resolution was better with 2D-HDTV. The estimate of relative distance was not influenced by the different visualization systems. Motor skill tasks were performed faster with binocular vision (3D-NTSC) than with monocular vision (2D-NTSC, 2D-HDTV). For both 2D settings, the deceleration phase of motion was prolonged (p < 0.05 vs 3D). Peak velocity was reduced with 2D-HDTV as compared with 3D-NTSC (p = 0.01). The surgeons tended to favor the 3D system despite their use of 2D systems in their own practice. CONCLUSIONS: Three-dimensional vision enhances telemanipulator performance as compared with a 2D system at the same or higher level of resolution. Because it allows faster and more precise movement, future surgical systems should focus on 3D visualization.

Are the indications for tissue valves different in 2001 and how do we communicate these changes to our cardiology colleagues?

The indications for tissue valves in the aortic and mitral positions are becoming better defined with advances in valve design, valve preservation, and management of reoperations. Although some patients who require cardiac valve replacement clearly benefit more from one type of valve than from another, not infrequently one encounters a patient who is in the "gray zone," where the optimal choice is difficult. At present, bioprostheses for the diseased aortic valve include stented porcine and pericardial valves, stentless porcine valves, aortic homograft, and pulmonary autograft. For patients with mitral valve disease, options for tissue valve replacement are a stented porcine or pericardial prosthesis. Generally, factors to consider in choosing the appropriate valve substitute include the patient's age, expected life expectancy, coexisting medical problems, lifestyle, and socioeconomics; the etiology of the valve disease, annular size, and physician and patient preference are also relevant. Despite the known finite durability of tissue valves, which is the main limitation in their use, the long-term results have been satisfactory, particularly in older patients, patients with a limited life expectancy, and those undergoing valve replacement in the aortic position. Distillation of available information and ongoing communication between the surgeon and the cardiologist will enable us to assist the patient in choosing the best valve substitute.

Endoscopic computer-enhanced beating heart coronary artery bypass grafting.

BACKGROUND: Telemanipulation systems have enabled coronary revascularization on the arrested heart. The purpose of this study was to develop a technique for computer-enhanced endoscopic coronary artery bypass grafting on the beating heart. METHODS: The operation was performed using the daVinci telemanipulation system. Through three ports, the left internal thoracic artery was harvested in 10 mongrel dogs (30 to 35 kg) using single right-lung ventilation and CO2 insufflation. Through a fourth port an articulating stabilizer, manipulated from a second surgical console, was inserted to stabilize the heart. The left anterior descending artery was snared using silicone elastomer slings anchored in the stabilizer cleats and the graft to coronary artery anastomosis was performed. RESULTS: In 7 of 10 dogs, total endoscopic beating heart bypass grafting, cardiac stabilization, arteriotomy, and arterial anastomosis were performed using computer-enhanced technology. Endoscopic stabilization and temporary left anterior descending artery occlusion were well tolerated. All grafts were patent although minor strictures were found in 2. In 3 dogs, the procedure could not be completed (1 ventricular arrhythmia, 1 left atrial laceration, and 1 right ventricular outflow tract compression). CONCLUSIONS: Endoscopic beating heart coronary artery bypass grafting is possible in a canine model using a computer-enhanced instrumentation system and articulating stabilization.

Endoscopic Doppler for detecting vessels in closed chest bypass grafting.

A new method of endoscopic ultrasonography during endoscopic bypass grafting is described. Using a 7.5 MHz ultrasonic catheter (AcuNav, Acuson, Mountain View, CA) that was introduced through a 5mm port and manipulated by robotically enhanced endoscopic instruments, detection of the internal thoracic artery (ITA) and the left anterior descending (LAD) artery was possible through layers of fat and muscle in a canine model.

Endovascular treatment of descending thoracic aortic aneurysms and dissections.

Various endovascular techniques have become viable therapeutic alternatives in the treatment of patients with many types of descending thoracic aortic pathology and aortic dissections. Descending thoracic aortic aneurysms can be successfully treated using stent grafts. This technique is less invasive and is associated with acceptable morbidity and mortality rates. Patients who are particularly likely to benefit include the very elderly population; those with markedly compromised cardiac, pulmonary, or renal status; and individuals who have previously undergone complex operations on the thoracic aorta. Other endovascular methods, such as aortic flap fenestration, stent, or covering of the primary intimal tear in the descending thoracic aorta with a stent graft, have also been effectively employed in the treatment of peripheral arterial complications of aortic dissection. Despite the reported early success of these endovascular percutaneous methods, true assessment of the effectiveness of these various techniques awaits long-term follow-up evaluation in large patient populations.

Tophaceous pseudogout of the mitral valve.

This report describes a 61-year-old patient on chronic hemodialysis with multiple, left-sided, intracardiac masses causing intermittent coronary obstruction. Mitral valve replacement was performed. Massive deposition of calcium pyrophosphate crystals in and around the valve cusps led to the diagnosis of tophaceous pseudogout (tumoral calcinosis) of the mitral valve.

Combined heart and single-lung transplantation in complex congenital heart disease.

We present a patient with a history of tricuspid and pulmonary atresia who underwent a classic Glenn shunt and a Potts shunt during childhood, resulting in different right and left pulmonary physiology. Because of progression of cardiopulmonary disease and the fact that the right lung was "protected," the patient underwent combined heart-left single-lung transplantation. The postoperative course was uneventful. Potential early and late advantages of this approach include simplifying of the operative procedure and mitigating the potential effects of obliterative bronchiolitis.

Composite valve graft versus separate aortic valve and ascending aortic replacement: is there still a role for the separate procedure?

BACKGROUND: To ascertain if operative technique has any bearing on outcome, the surgical results after aortic root replacement using either a composite valve graft (CVG) or a separate graft and valve (GV) were analyzed. METHODS AND RESULTS: Three hundred and ninety consecutive, nonrandomized patients treated for aortic valve disease and ascending aortic aneurysm (n=278) or type A dissection (n=112 [45 acute]) between 1965 and 1995 were analyzed retrospectively. One hundred and thirty-five patients received a CVG, and 255 had separate GV replacement. Mean age was 52+/-16 years (+/-1 SD). Eighty-two patients (44% of the CVG group) had the Marfan syndrome (MFS). Follow-up (96% complete) totaled 2247 patient-years and extended to 27 years. The operative mortality rate was 10+/-3% (+/-70% confidence limits) for patients receiving a CVG and 15+/-2% for GV replacement (P=NS). The 15-year actuarial survival estimate was higher for the CVG group (53+/-14% [+/-SEM] versus 36+/-4%, P=.037). Seven patients in the CVG group required reoperation on the aortic valve or ascending aorta, as did 49 in the GV group. The probabilities of freedom from reoperation on the aortic rootwere 82+/-9% and 75+/-4% at 10 years for the CVG and GV group (P=NS). Thirty variables were analyzed in a multivariate model: pulmonary disease, higher New York Heart Association functional class, and longer cardiopulmonary bypass time were linked with higher operative mortality risk; older age, emergency operation, coronary artery disease, and liver dysfunction were independent determinants of late death. Younger age and use of a bioprosthesis were predictors of late reoperation. Type of procedure (GV versus CVG) was not a significant predictor of any outcome variable. CONCLUSIONS: The long-term results after CVG or GV were similar, which reflects proper patient selection. Use of a composite valve graft theoretically confers more protection against recurrent aortic root aneurysm, and, unless one opts for a valve-sparing aortic root replacement procedure, is most appropriate for younger patients, those with the MFS (including acute dissections), and others with marked pathological involvement of the sinuses. On the other hand, use of a separate GV should not be abandoned; in carefully selected patients (and if properly performed, eg, excision of the sinuses), GV also provides satisfactory results.

Minimally invasive coronary artery bypass grafting.

Minimally invasive cardiac surgery has generated a tremendous amount of enthusiasm in the cardiology and cardiac surgical communities. Coronary revascularization without cardiopulmonary bypass through a small anterior thoracotomy or mediastinotomy has been introduced as an alternative to the conventional approach. An endovascular or port-access technique for cardiopulmonary bypass and cardioplegic arrest has been developed for use in cardiac surgery. This peripherally based system achieves aortic occlusion, cardioplegia delivery, and left ventricular decompression; thus, coronary revascularization and various cardiac procedures can be effectively performed in a less invasive fashion than conventional median sternotomy. Continued technical advances in minimally invasive cardiac surgery will facilitate these procedures, increase patient safety, and contribute to acceptable long-term results.

Minimally invasive mitral valve surgery.

Because of advances in video-assisted general and thoracic surgery, minimally invasive cardiac surgery has been successfully performed experimentally and clinically. Recently described techniques of less invasive mitral valve surgery include limited right thoracotomy, parasternal incision, and partial sternotomy. These methods have been coupled to video-assisted thoracoscopy to further decrease the incision size. Cardiopulmonary bypass (central or peripheral) and either hypothermic fibrillatory arrest or cardioplegic arrest are used. The Port-Access approach is a catheter-based system that provides effective cardiopulmonary bypass, cardioplegic arrest, and ventricular decompression. At Stanford University, 10 Port-Access mitral valve procedures were performed between May 1996 and January 1997. The mean age of the patients (eight men and two women) was 54 +/- 7 (SD) years. Nine patients had severe mitral regurgitation from myxomatous degeneration, and one suffered from severe mitral regurgitation and moderate mitral stenosis from a rheumatic etiology. Five patients underwent mitral valve replacement, and five underwent mitral valve repair. There was no operative mortality. The mean incision length was 8.1 +/- 2.5 cm. The aortic "cross-clamp" time was 99 +/- 22 minutes, and the cardiopulmonary bypass time was 151 +/- 52 minutes. The total hospitalization averaged 4.3 +/- 1.4 days. One patient developed third-degree atrioventricular block, requiring a prolonged stay in the intensive care unit and pacemaker placement; the same patient was found to have a perivalvular leak on follow-up, requiring reoperation at 3 months. Port-Access mitral valve procedures can be performed safely with satisfactory outcome. Greater clinical experience and long-term follow-up are necessary to fully assess these less invasive techniques of mitral valve surgery.

Port-access cardiac operations with cardioplegic arrest.

BACKGROUND: A less invasive approach to cardiac surgery has been propelled by recent advances in video-assisted surgery. Previous obstacles to minimally invasive cardiac operations with cardioplegic arrest included limitations in operative exposure, inadequate perfusion technology, and inability to provide myocardial protection. METHODS: Port-access technology allows endovascular aortic occlusion, cardioplegia delivery, and left ventricular decompression. The endoaortic clamp is a triple-lumen catheter with an inflatable balloon at its distal end. Antegrade cardioplegia is delivered through a central lumen, which also acts as an aortic root vent, a second lumen is used as an aortic root pressure monitor, and a third lumen is used for balloon inflation to provide aortic occlusion. RESULTS: Experimental and clinical studies have demonstrated the feasibility of port-access coronary artery bypass grafting and port-access mitral valve procedures. Endovascular cardiopulmonary bypass using the endoaortic clamp was effective in achieving cardiac arrest and myocardial protection to allow internal mammary artery to coronary artery anastomosis in a still and bloodless field. Intracardiac procedures, such as mitral valve replacement or repair, have been successfully performed clinically. CONCLUSION: The port-access system effectively achieves cardiopulmonary bypass and cardioplegic arrest, thereby enabling the surgeon to perform cardiac procedures in a minimally invasive fashion. This system provides for endovascular aortic occlusion, cardioplegia delivery, and left ventricular decompression.

Simultaneous abdominal aortic replacement and thoracic stent-graft placement for multilevel aortic disease.

PURPOSE: Patients with aneurysmal disease involving both the descending thoracic and abdominal aorta have historically required simultaneous or sequential conventional operations, but the morbidity rate is high with either approach in these patients, who often exhibit coexisting cardiopulmonary disease. Transluminally placed endovascular grafts have recently been developed for repair of aortic aneurysms, and we have implemented these techniques to eliminate the need for a thoracotomy in patients with multilevel aortic disease. METHODS: Since January 1994, 18 patients have undergone conventional abdominal aortic replacement with endovascular stent-graft placement into the descending thoracic aorta under fluoroscopic guidance through a 10 mm Dacron side limb off the abdominal graft. Abdominal aortic replacement required a tube graft in eight patients and bifurcated grafts in 10 patients. Thoracic stent-grafts (custom fabricated, woven Dacron covered, self-expandable stents) averaged 12.2 +/- 4.2 cm (mean +/- SD) in length. RESULTS: One patient died, resulting in a hospital mortality rate of 6%. No patients required further surgical intervention to treat their aortic disease. Seventeen patients (94%) are currently well 14 +/- 8 months after surgery (range, 3 to 29 months) with completely excluded thoracic aortic disease, no stent migration, and no change in stent configuration documented by serial radiologic examinations. CONCLUSIONS: Simultaneous abdominal aortic replacement and deployment of a thoracic stent-graft can safely exclude multilevel aortic aneurysmal disease and may be a valuable treatment option for these otherwise high-risk patients.

Port-access cardiac surgery with cardiopulmonary bypass and cardioplegic arrest.

In the past decade, laparoscopic and thoracoscopiC technology have significantly and irreversibly altered the approach to many general and thoracic surgical diseases. With advances in laparoscopy and thoracoscopy, the concept of a minimally invasive approach to cardiac surgery has been realized.

Twenty-year clinical experience with porcine bioprostheses.

BACKGROUND: For the past 25 years, porcine valves have been the most widely implanted bioprosthesis, thereby becoming the standard for comparison with newer bioprosthetic valves. METHODS: We retrospectively analyzed 2,879 patients who underwent aortic (AVR; n = 1,594) or mitral (MVR; n = 1,285) valve replacement between 1971 and 1990. Follow-up was 97% complete and extended to 20 years (total, 17,976 patient-years). Patient age ranged from 16 to 94 years; mean age in patients who underwent AVR was 60 +/- 15 (+/- standard deviation) years; that for patients who underwent MVR was 58 +/- 13 years. RESULTS: The operative mortality rates were 7% +/- 1% (70% confidence limits) for AVR and 10% +/- 1% for MVR. Actuarial estimates of freedom from structural valve deterioration at 10 and 15 years were 78% +/- 2% (SE) and 49% +/- 4%, respectively, for the AVR subgroup; and 69% +/- 2% and 32% +/- 4%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from reoperation at 10 and 15 years were 76% +/- 2% and 53% +/- 4%, respectively, for the AVR subgroup and 70% +/- 2% and 33% +/- 4%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from thromboembolism at 10 and 15 years were 92% +/- 1% and 87% +/- 2%, respectively, for the AVR subgroup and 86% +/- 1% and 77% +/- 3%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from anticoagulant-related hemorrhage at 10 and 15 years were both 96% +/- 1% for the AVR subgroup and 93% +/- 1% and 90% +/- 2%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from valve-related mortality at 10 and 15 years were 86% +/- 1% and 78% +/- 3%, respectively, for the AVR subgroup and 84% +/- 2% and 70% +/- 4%, respectively, for the MVR subgroup (p = not significant). Multivariate analysis (Cox model) showed younger age, later year of operation, and valve site (MVR > AVR) to be significant risk factors for structural valve deterioration. Younger age, later year of operation, valve site (MVR > AVR), and renal insufficiency were the significant, independent risk factors for reoperation. Multivariate analysis revealed that higher New York Heart Association functional class, longer cardiopulmonary bypass time, congestive heart failure, renal insufficiency, and longer cross-clamp time were significant risk factors for valve-related mortality. Valve manufacturer did not emerge as a factor in any analysis. CONCLUSIONS: These long-term results with porcine bioprostheses were satisfactory, particularly in older patients and those undergoing AVR. As expected, younger age was a significant risk factor for structural valve deterioration and reoperation in both groups. Surprisingly, the durability of porcine bioprosthetic valves has not improved over time, which possibly can be attributed to more enhanced postoperative surveillance and earlier reintervention. These first-generation Hancock and Carpentier-Edwards porcine bioprostheses achieved similar long-term performance.

Porcine valves: Hancock and Carpentier-Edwards aortic prostheses.

Hancock and Carpentier-Edwards porcine bioprostheses are the two most widely implanted biological valves and have become the standard by which the performance of newer tissue valves are measured. New guidelines for reporting valve-related complications have provided more comprehensive evaluations and meaningful comparison of the long-term results of valve substitutes. Clinical investigations directly comparing the Hancock and Carpentier-Edwards bioprostheses have shown no significant differences in the long-term performance of these two valves. The incidence of structural valve deterioration for porcine bioprostheses begins to increase 5 to 6 years after implantation. For patients undergoing aortic valve replacement, estimates of freedom from structural valve deterioration at 10 and 15 years range from 76% to 91% and 37% to 63%, respectively. The incidence of structural valve deterioration may be offset by the limited survival of older patients; thus, the durability of a bioprosthesis may be sufficient for the majority of these patients. The long-term results of the porcine bioprosthesis have been satisfactory, particularly in older patients and those undergoing aortic valve replacement. The performance of the Hancock modified orifice (MO) bioprosthesis is comparable with that of other bioprostheses despite its more complex fabrication process. Although it does not offer any distinct advantages in terms of durability, the Hancock MO valve is associated with lower pressure gradients and larger calculated valve areas compared with other porcine valves in the smaller sizes. Based on currently available data, there are no distinct differences in the performance of the second-generation porcine bioprostheses compared with the first-generation valves, and any purported advantages need to be confirmed with long-term evaluations.

Surgical management of aortic dissection during a 30-year period.

BACKGROUND: Certain recent studies have demonstrated improved surgical outcome in patients with aortic dissection. We analyzed the surgical survival rates of patients with acute aortic dissections and the late prognosis of those with aortic dissection during a 30-year period. METHODS AND RESULTS: Between 1963 and 1992, 360 patients (256 men and 104 women; mean +/- 1 SD age, 57 +/- 14 years) underwent surgery for aortic dissection: 174 patients had an acute type A (AcA), 46 an acute type B (AcB), 106 a chronic type A (ChA), and 34 a chronic type B (ChB) aortic dissection. The overall operative mortality rate was 24 +/- 8% (26 +/- 3% for AcA, 39 +/- 8% for AcB, 17 +/- 4% for ChA, and 15 +/- 6% for ChB, [+/- 70% confidence limit]). The operative mortality rates for patients with acute aortic dissection (AcA or AcB) were assessed for five time "windows": 1963 to 1972 (42 +/- 8%), 1973 to 1977 (37 +/- 8%), 1978 to 1982 (15 +/- 6%), 1983 to 1987 (27 +/- 6%), and 1988 to 1992 (26 +/- 6%). Logistic regression analysis suggested that the low operative mortality rate during the 1978-to-1982 interval occurred by chance. Multivariate analysis showed earlier operative year, hypertension, cardiac tamponade, renal dysfunction, and older age were independent determinants of operative death. Actuarial survival rates (including early deaths) after 5, 10, and 15 years for AcA patients were 55%, 37%, and 24%; for AcB, 48%, 29%, and 11%; for ChA, 65%, 45%, and 27%; and for ChB, 59%, 45%, and 27%. Multivariate analysis revealed that older age and previous operation were significant predictors for late death. Freedom from reoperation for all patients was 84%, 67%, and 57% at 5, 10, and 15 years, respectively. CONCLUSIONS: Although the operative mortality rate decreased over time for patients with aortic dissection, the risk for those with acute aortic dissection during the last 10 years (1983 to 1992) is probably more realistic than that observed in the preceding 5-year interval (1978 to 1982). The operative mortality rates for patients with chronic aortic dissection have remained relatively static. Earlier diagnosis of acute aortic dissection before development of cardiac tamponade and renal impairment is critical to improve the operative salvage rate. Long-term outcome still is not optimal, which emphasizes the need for better serial postoperative aortic imaging surveillance and medical follow-up and blood pressure control.

Endovascular stent-grafting after arch aneurysm repair using the "elephant trunk".

A 68-year-old woman with severe chronic obstructive pulmonary disease, aortic valvular insufficiency, and diffuse thoracic aortic aneurysm underwent aortic valve replacement and separate Dacron graft replacement of the ascending aortic and arch aneurysms using the elephant trunk technique. She was discharged on the tenth postoperative day. Five months later, she underwent endovascular stent-graft repair of the descending thoracic aortic aneurysm. She recovered uneventfully, and was discharged on the third postoperative day. Follow-up computed tomography at 6 months demonstrated exclusion of all flow into the descending thoracic aortic aneurysm. The elephant trunk technique followed by endovascular stent-grafting of the descending thoracic component is a potential therapeutic option in selected high-risk patients with diffuse aortic aneurysmal disease.

A method to assess endocardial regional longitudinal curvature of the left ventricle.

Knowledge of the instantaneous geometry of the left ventricular (LV) chamber is necessary to calculate LV function and wall stresses. We describe a method utilizing myocardial markers that does not rely on any a priori assumptions of global LV geometry. Five dogs underwent placement of 25 endocardial and 3 epicardial miniature LV markers. Six weeks later, the animals were studied during conscious closed-chest conditions. The three-dimensional coordinates of the LV markers were used to compute longitudinal fitted curves for LV walls and septum during steady-state conditions; endocardial radii of curvature (rcurv) were then computed for each region at the midequatorial (rcurv-eq) and apical levels. There was a uniform decrease in rcurv in each LV wall during systole (compared with diastole, P < 0.01); at end systole, rcurv was regionally heterogeneous between opposing walls, e.g., anterior and posterior rcurv-eq values were 17.2 +/- 2.0 and 17.7 +/- 1.8 (SD) cm, respectively (P < 0.05). At end diastole, only septal-lateral rcurv-eq was different (16.9 +/- 2.1 vs. 18.7 +/- 1.3 cm: P < 0.05). Normalization of rcurv (to instantaneous LV volume) removed the systolic-diastolic differences, but a similar pattern of regional heterogeneity persisted. The data presented pertain to the LV endocardial surface, but the method described can be applied to the epicardial surface as well; this new method offers promise in assessing dynamic changes in longitudinal LV endocardial curvature.