The role of left ventricular reconstruction for cardiogenic shock.

Left ventricular remodeling after myocardial infarction is recognized as an early adaptive mechanism that later results in adverse physiologic changes. Surgical therapy for this condition includes exclusion of nonfunctional segments of ventricular wall and restoration of more normal ventricular geometry. The Dor procedure, or endoventricular patch plasty, is recognized as an excellent means of accomplishing this goal. Most series in regard to the Dor procedure report results in patients who electively come to surgery after developing global ventricular distension after an area of akinesia or dyskinesia. We report a small series of 6 patients who presented with acute myocardial infarction and who developed cardiogenic shock after ventricular dilation. Each patient underwent emergent revascularization and left ventricular reconstruction using the Dor technique. A seventh patient with akenesia, but without preoperative shock, required the Dor procedure to wean from cardiopulmonary bypass. There were no in-hospital deaths, and follow-up showed good outcomes. In certain select acute subsets (large anterior myocardial infarction, cardiogenic shock, and ventricular dilation), immediate revascularization and restoration of left ventricular size improves outcomes by changing left ventricular shape and thereby pre-empting remodeling and restoring blood flow to ischemic myocardium.     

Elective bridging to recovery after repair: the surgical approach to ventricular reverse remodeling

We described our "surgical approach to reverse ventricular remodeling" in advanced chronic heart failure, based on the unique idea that "downstaging" class IV heart failure by supporting patients with left ventricular assist devices (LVADs) allows treatments mainly indicated for class III patients. The types of surgeries include mitral valve repair, surgical ventricular remodeling, coronary artery bypass grafting, and cardiac resynchronization. This approach has been applied to two patients with class IV chronic heart failure due to idiopathic dilated cardiomyopathy who were supported with the magnetically levitated Levacor LVAD. These were the first in-human implantations of this device. Sustained short- to medium-term recovery has been achieved in both patients.     

Concomitant aortic root remodeling and coronary bypass in a patient with poor left ventricular function.

A 58-year-old man who had previously undergone rectal cancer surgery and who had poor left ventricular function underwent concomitant aortic root remodeling and coronary bypass for aortic root aneurysm with aortic regurgitation and severe coronary artery disease. Intermittent retrograde cold blood cardioplegia and leukocyte-depleted terminal blood cardioplegia were used for myocardial protection. Angiographic studies 1 month after surgery showed improved left ventricular function at an ejection fraction from 24 to 46%. During a 1-year follow-up, he has remained free of any cardiac event. Even though this report is limited to a case and follow-up, this technique is expected to be beneficial even in patients with severely depressed left ventricular function when the postoperative quality of life is considered.     

Long-term surgical results in sudden death syndrome associated with cardiac dysfunction after myocardial infarction.

To evaluate the surgical results in patients with inducible ventricular tachyarrhythmias due to coronary disease and left ventricular dysfunction, the authors reviewed their experience in 170 patients who had survived one or more cardiac arrests after myocardial infarction and were unresponsive to drug therapy based on electrophysiologic studies (EPS). There were nine operative deaths (5%). Based on intraoperative EPS, surgical remodeling of left ventricular dysfunction (aneurysm resection, infarct debulking, and septal reinforcement) with map-guided cryoablation and coronary artery bypass graft was performed in 34 patients (group A), and left ventricular remodeling and coronary artery bypass graft without guided endocardial resection was performed in 25 patients (group B). Forty-three patients (group C) had coronary artery bypass graft with implantation of an automatic implantable cardioverter defibrillator (AICD). Group D (68 patients) received AICD only. After operation, based on EPS results, four patients in group A (12%) and three patients in Group B (15%) required AICD implantation. Overall survival at 6 years was 65%, 48%, 85%, and 58% in patient groups A, B, C, and D, respectively (p = not significant). During follow-up in group A patients, none died suddenly and none needed AICD. In group B, two patients required AICD 3 and 5 years later, and five patients died suddenly. The incidence of sudden death was 2.3%/patient/year and 3.5%/patient/year after AICD implantation (groups C and D). At 6 years, cardiac-event-free survival was 80% and 70% for groups A and B and 38% and 24% for groups C and D, respectively (p less than 0.001). Patients receiving map-guided ablative procedures had significantly improved cardiac-event-free survival rates.     

Left ventricular aneurysm resection with port-access surgery: a new mini-invasive surgical approach

BACKGROUND: In recent years port-access and endovascular extra-corporeal circulation techniques have allowed valvular and coronary operations to be performed by mini-thoracotomy. Experience with the technique suggested application to resection of ventricular aneurysms, which are usually approached through a median sternotomy with the use of traditional cardiopulmonary bypass. METHODS: We performed a left port-access mini-thoracotomy, with 6 to 8 cm skin incisions, in 7 patients undergoing endoventricular pericardial patch repair for anterior left ventricular aneurysm. Cardiopulmonary bypass was effected using the Heartport system. The mean interval between myocardial infarction and operation was 60.4 +/- 57.7 months. Three patients developed sustained ventricular tachicardia. Mean preoperative ejection fraction was 34% +/- 11%. Associated procedures were coronary bypass grafting in 2 patients and cryosurgery in 3 patients. RESULTS: All patients survived to discharge and are alive and well after an average 14.5 months. They are all in NYHA class I-II. Postoperative echocardiograms revealed an average ejection fraction of 48.0% +/- 7.5% (p = 0.006 compared with preoperative value). The 3 patients who had cryosurgery did not demonstrate any recurrence of arrhythmias. CONCLUSIONS: Left ventricular aneurysm can be successfully treated through port-access mini-thoracotomy with endovascular cardiopulmonary bypass, avoiding median sternotomy. This mini-invasive approach allows effective ventricular remodeling. Revascularization and antiarrhythmia surgery can also be done at the same time. In case of severely reduced ventricular function this approach permits fibrillatory arrest without aortic cross-clamping. The results are also good in terms of hospitalization time and long-term survival.     

Ischemia of the interventricular septum. A mechanism of right ventricular failure during mechanical left ventricular assist.

Right ventricular failure has been noted in up to 25% of patients requiring a left ventricular assist device. Altered septal motion or function is one proposed mechanism of right ventricular failure during left heart bypass. We studied the effect of regional ischemia and reperfusion of the interventricular septum on right ventricular function during complete left heart bypass. In six calves the septal perforating branches of the proximal left anterior descending coronary artery were isolated for intermittent occlusion. Complete left heart bypass was established with a Pierce-Donachy left ventricular assist device. Right and left ventricular function were studied with two-dimensional echocardiography and with intraventricular pressure monitors. Establishment of left heart bypass did not significantly affect right ventricular developed pressure, right ventricular end-diastolic area, or right ventricular fractional change in area. Left heart bypass significantly (p less than 0.001) decreased percent systolic septal wall thickening. Septal ischemia during left heart bypass resulted in a decrease in right ventricular developed pressure (p = 0.09), significant increase in right ventricular end-diastolic area (p = 0.002) and significant decrease in right ventricular fractional change in area (p less than 0.001), and a further decrease in interventricular septal wall thickening (p = 0.016). The interventricular septum became thin with flattening of its normal contour. Septal reperfusion resulted in right ventricular recovery with significant improvement in all factors (p less than 0.02). Similar results were documented during a second episode of septal ischemia with recovery after septal reperfusion. In some cases, septal ischemia may be an important factor in the development of right ventricular failure during left heart bypass.     

Effects of milrinone versus epinephrine on left ventricular relaxation after cardiopulmonary bypass following myocardial revascularization: assessment by color m-mode and tissue Doppler

OBJECTIVE: The purpose of this study was to evaluate the left ventricular lusitropic effects of epinephrine versus milrinone after cardiopulmonary bypass. DESIGN: Prospective randomized study. SETTING: Single institution, university teaching hospital. PARTICIPANTS: Adult patients undergoing coronary artery bypass grafting under cardiopulmonary bypass. INTERVENTIONS: After separation from cardiopulmonary bypass, patients were randomized to receive intravenous epinephrine by continuous infusion (0.03 microg/kg/min) or milrinone (50 microg/kg followed by 0.5 microg/kg/min). Transesophageal echocardiographic evaluation of left ventricular diastolic function, with emphasis on relaxation, was performed before and after bypass and after the administration of either epinephrine or milrinone. MEASUREMENTS AND MAIN RESULTS: Measurements included pulse-wave Doppler analysis of mitral inflow and pulmonary vein and left ventricular outflow tract velocities. Left ventricular inflow velocity of propagation measured with color M-mode and tissue Doppler assessment of early mitral annulus velocity were used to evaluate left ventricular relaxation. Values of velocity of propagation and mitral annulus velocity improved significantly after bypass, suggesting improved relaxation. The administration of either epinephrine or milrinone did not result in further improvement in left ventricular relaxation. CONCLUSIONS: After cardiopulmonary bypass, left ventricular relaxation was significantly improved. Neither epinephrine nor milrinone exhibited favorable lusitropic effects after bypass.     

非体外循环下采用自制二尖瓣成形装置手术治疗轻至中度缺血性二尖瓣关闭不全

目的尝试在非体外循环冠状动脉旁路移植术(OPCAB)期间对轻至中度缺血性二尖瓣反流(IMR)患者采用自制二尖瓣成形装置进行外科处理,并评估其疗效。方法回顾性分析自2009年9月至2011年8月北京安贞医院6例轻至中度IMR患者(男4例、女2例,年龄52～73岁)在OPCAB期间采用自制二尖瓣成形装置进行二尖瓣成形的临床资料。在处理IMR前及处理后通过经食管超声心动图测定IMR程度、二尖瓣瓣环前后径、左心室短轴径、左心室长轴径、左心室球形指数(左心室短轴径/左心室长轴径)等;通过Swan-Ganz导管测量并记录主动脉平均压、肺动脉平均压和中心静脉压等。比较围术期相关心功能指标。结果无住院死亡。二尖瓣成形后IMR均消失、二尖瓣瓣环前后径[(3.43±0.08)cm vs.(3.68±0.08)cm;t=5.430,P=0.001]、左心室短轴径[(4.80±0.21)cm vs.(5.53±0.11)cm;t=7.530,P=0.001]和左心室球形指数(0.64±0.02 vs.0.74±0.01;t=11.110,P=0.002)均较处理前明显减小;左心室长轴径无明显变化(P>0.05);术中血流动力学指标无明显变化。术后3个月6例患者(随访率100%)均在门诊复查,均无自主临床症状,心功能均改善至Ⅰ级(NYHA)。超声心动图提示:二尖瓣无反流4例,有微量反流2例。结论在OPCAB期间采用自制二尖瓣成形装置成形治疗IMR,直接完成了左心室塑型,规避了体外循环风险,即刻疗效确切,对循环指标影响甚小,有一定的临床应用价值。     

Effects of left heart bypass on right ventricular performance. Evaluation of the right ventricular end-systolic and end-diastolic pressure-volume relation in the in situ normal canine heart

Although left heart bypass has gained popularity as a powerful technique to assist the severely failed left heart, apparent right heart failure has often developed during the bypass procedure. We investigated whether the coexisting right heart failure is attributable to the left heart bypass in 16 open-chest dogs. We evaluated the effects of left heart bypass on the right ventricular systolic properties by the slope of the end-systolic pressure-volume relation and its effects on the diastolic properties by chamber compliance. Overall right ventricular performance was assessed by the end-diastolic pressure versus cardiac output relationship. The left heart bypass decreased the slope slightly when the assisted flow ratio exceeded 75% (-14% +/- 8% at the assisted flow ratio of 100%, p less than 0.02) and thus had a deleterious influence on right ventricular performance. The left heart bypass, on the other hand, had a counteracting beneficial influence on right ventricular performance through the increase in chamber compliance (38% +/- 5%, p less than 0.01) and the decrease in pulmonary arterial input resistance (-15% +/- 12%, p less than 0.01). The net effect of the left heart bypass was the increase in cardiac output (20% +/- 2%, p less than 0.05) for any given right ventricular end-diastolic pressure. We conclude that in normal hearts the left heart bypass augments right ventricular performance. We ascribe these beneficial effects to diastolic ventricular interdependence and afterload unloading.     

Influence of Potassium Cardioplegia versus Ischemic Arrest on Regional Left Ventricular Diastolic Compliance in Humans

To compare the effects of hypothermic ischemic arrest versus hypothermic potassium cardioplegia, regional left ventricular performance was monitored in 20 adult male patients undergoing saphenous vein bypass operation. Twelve patients received ischemic arrest (Group 1), and 8 received potassium cardioplegia (Group 2). Groups 1 and 2 did not differ in left ventricular ejection fraction (0.62 versus 0.60), number of bypassed vessels (3.7 versus 3.4), mean cross-clamp time (75 versus 63 minutes), or mean cardiopulmonary bypass time (182 versus 170 minutes). Before cardiopulmonary bypass was begun, a pair of ultrasonic crystals was secured in the left ventricular anterior myocardium to measure segment motion and a micromanometer-tipped catheter was placed in the left ventricular chamber. All patients received a saphenous vein bypass graft to a vessel supplying the anterior left ventricular wall in the region of the ultrasonic crystals.Comparison of changes in systolic measurements revealed no significant differences between Groups 1 and 2. After saphenous vein bypass grafting, the left ventricular end-diastolic pressure (11.4 to 17.0 mm Hg) and modulus of left ventricular segment stiffness (0.37 to 0.67, p < 0.02) were elevated in Group 1 but no changes were observed in Group 2 (14.0 to 15.6 mm Hg, and 0.16 to 0.24, respectively).Compared with hypothermic ischemic arrest, hypothermic potassium cardioplegia is not associated with an increased left ventricular diastolic stiffness shortly after saphenous vein bypass grafting in humans.     

Surgical treatment of ischemic mitral regurgitation might not influence ventricular remodeling

OBJECTIVES: Surgical treatment for ischemic mitral regurgitation has become more aggressive. However, no clinical study has demonstrated that surgical correction of chronic ischemic mitral regurgitation improves survival. We used 4 well-developed ovine models of postinfarction left ventricular remodeling to test the hypothesis that ischemic mitral regurgitation does not significantly contribute to postinfarction left ventricular remodeling. METHODS: Infarction of 21% to 24% of the left ventricular mass was induced by means of coronary ligation in 77 sheep. Infarctions varied only by anatomic location in the left ventricle: anteroapical, n = 26; anterobasal, n = 16; laterobasal, n = 9; and posterobasal, n = 20. Six additional sheep had ring annuloplasty before posterobasal infarction. End-systolic and end-diastolic left ventricular volume, end-systolic muscle-to-cavity area ratio, left ventricular sphericity, ejection fraction, and degree of ischemic mitral regurgitation, as determined by means of quantitative echocardiography, were assessed before infarction and at 2, 5, and 8 weeks after infarction. RESULTS: All infarcts resulted in significant postinfarction remodeling and decreased ejection fraction. Anteroapical infarcts lead to left ventricular aneurysms. Only posterobasal infarcts caused severe and progressive ischemic mitral regurgitation. Remodeling because of posterobasal infarcts was not more severe than that caused by infarcts at other locations. Furthermore, prophylactic annuloplasty prevented the development of mitral regurgitation after posterobasal infarction but had no effect on remodeling. CONCLUSION: The extent of postinfarction remodeling is determined on the basis of infarct size and location. The development of ischemic mitral regurgitation might not contribute significantly to adverse remodeling. Ischemic mitral regurgitation is likely a manifestation rather than an important impetus for postinfarction remodeling.     

Ischemic cardiomyopathy treated with overlapping ventriculoplasty

A 58-year-old man was admitted due to congestive heart failure. Left ventriculography showed end-diastolic volume index (EDVI) of 172 ml/m2 and ejection fraction (EF) of 16%. Coronary angiography showed severe double vessel disease (the left anterior descending artery and the right coronary artery). Echocardiography showed dilated heart [left ventricular end-diastolic diameter (LVDd) of 74 mm] and severe mitral regurgitation due to tethering of the leaflets. The patient underwent our original left ventricular volume reduction operation, termed overlapping ventriculoplasty (OLVP) combined with mitral annuloplasty, papillary muscles plication (PMP) and coronary artery bypass grafting (CABG). The postoperative course was excellent. Postoperatively, the EDVI decreased to 96 ml/m2, the LVDd diminished to 67 mm, and the EF improved to 34%. This case implies the role of left ventricular remodeling procedure of OLVP and PMP in the ischemic cardiomyopathy with ischemic mitral regurgitation.     

Circulatory support in infants with post-cardiopulmonary bypass left ventricular dysfunction using a left ventricular assist device

Extracorporeal membrane oxygenation has been advocated as the most appropriate mode of circulatory support in the paediatric age group for post-cardiopulmonary bypass ventricular dysfunction. The results in infants who have predominantly left ventricular failure, or who require such support in order to be weaned off bypass, have been disappointing. Three infants with severe left ventricular dysfunction following cardiopulmonary bypass for correction of congenital heart defects have been managed with a left ventricular assist device. Two required this form of circulatory support in order to be weaned from full bypass while in the third infant it was instituted for progressive left ventricular dysfunction postoperatively. All three were less than 10 kg in weight. Left atrial appendage to aortic bypass was effected using a closed loop circuit with a constrained vortex pump (Biomedicus). Duration of support ranged between 40 and 146 h. One infant made a complete recovery and was able to be discharged home 20 days postoperatively. Another made a circulatory recovery such that both mechanical and inotropic support could be discontinued but had sustained massive neurological damage. The third died of progressive left ventricular dysfunction. This experience with a left ventricular assist device demonstrates that it is technically feasible in small infants, and can be performed to good effect in infants with predominant left ventricular dysfunction following cardiac surgery. It may well be more appropriate than extracorporeal membrane oxygenation in this group of patients.     

Heparinless total left heart bypass with induced ventricular fibrillation

A new technic of extracorporeal total left heart bypass without anticoagulation is described. Left atrial and ventricular cannulas, coated with PPG, drain the blood into a bladder pump which returns blood into the descending thoracic aorta, thus establishing total left heart bypass. In acute experiments, ventricular fibrillation was electrically induced and total left heart bypass was continued for one hour (nine dogs) or four hours (one dog), after which the heart was successfully defibrillated. Near normal systemic circulation was maintained during bypass, although there was no active driving force through the pulmonary circulation except for right atrial contraction. In survival experiments ten dogs were subjected to the same procedure for one to three hours. After defibrillation they were allowed to survive for two to four weeks. Eight were long-term survivors. One died because of a technical error and the other of atelectasis. In four other dogs an autogenous saphenous vein was successfully implanted between the ascending aorta and the circumflex coronary artery using a nonthrombogenic left heart bypass with ventricular fibrillation technic. There was minimal blood loss due to elimination of anticoagulants, and the elimination of an artificial oxygenator simplified the extracorporeal circulation system. During total left heart bypass with ventricular fibrillation, inspiratory pressures were maintained at 10 mm Hg. This study indicates (1) that total left heart bypass can maintain normal systemic circulation in dogs for up to four hours during ventricular fibrillation, and (2) that this technic may be applicable to simplify coronary artery bypass surgery.     

Clinical and Experimental Evaluation of Left Ventriculoiliac Shunt Bypass during Repair of Lesions of the Descending Thoracic Aorta

Temporary ventriculoiliac bypass with a tridodecylmethylammonium chloride-coated shunt has been used routinely at the University of North Carolina for the past seven years for repair of lesions of the descending thoracic aorta. Although the technique appears to be safe and reliable, the hemodynamic effects of prolonged nonvalved apical diversion on left ventricular function are not defined. To evaluate left ventricular performance during ventriculoiliac shunt bypass, the procedure was investigated in adult sheep. Systolic flow through the shunt was pulsatile and accounted for approximately 35% of the total cardiac output. Reversed flow was minimal. No significant change occurred in cardiac output, left ventricular end-diastolic pressure, or left atrial pressure. Perfusion of the abdominal viscera through the shunt was sufficient to prevent intestinal and renal ischemia. Our results indicate that the shunt provides left ventricular decompression without evidence of deterioration in left ventricular performance for up to three hours of apical bypass and aortic occlusion.It is included that bypass with a left ventriculoiliac shunt provides safe and effective diversion during repair of lesions of the descending thoracic aorta and offers an excellent alternative to methods involving greater technical hazard or requiring systemic anticoagulation.     

Comparison of tidal ventilation and high-frequency jet ventilation before and after cardiopulmonary bypass in dogs using two-dimensional transesophageal echocardiography

This study compared the use of high-frequency jet ventilation (HFJV) and tidal ventilation (TV) in a group of dogs with induced global myocardial ischemia before and after cardiopulmonary bypass. Transesophageal echocardiography was used to determine whether HFJV with its lower airway pressures could improve cardiac performance. The surgical procedure was separated into four study periods: closed chest before bypass, open chest before bypass, open chest after bypass, and closed chest after bypass. During each of these study periods, the dogs were randomly ventilated with alternate periods of TV and HFJV to maintain the PaCO2 at 34.3 +/- 3.3 mm Hg (mean +/- SEM). Cardiac output, stroke volume, systemic mean blood pressure, left ventricular ejection fraction, left ventricular end-diastolic volume, left ventricular dP/dt, left ventricular stroke work, and expiratory volumetric flows were higher during HFJV, whereas airway pressures and pulmonary vascular resistance were lower. Increases in cardiac output and stroke volume during HFJV were due to a combination of improved left ventricular contractility indicated by increased LV dP/dt and increased left ventricular end-diastolic volume accompanying decreased airway pressures. These data indicate that HFJV with its lower airway pressure is associated with significantly less impairment of cardiovascular function than TV in dogs with induced global myocardial ischemia.     

Alterations in left ventricular torsion in tachycardia-induced dilated cardiomyopathy

OBJECTIVE: Left ventricular torsion reduces transmural systolic gradients of fiber strain, and torsional recoil in early diastole is thought to enhance left ventricular filling. Left ventricular remodeling in dilated cardiomyopathy may result in changes in torsion dynamics, but these effects are not yet characterized. Tachycardia-induced cardiomyopathy is accompanied by systolic and diastolic heart failure and left ventricular remodeling. We hypothesized that cardiomyopathy would alter systolic and diastolic left ventricular torsion mechanics, and this hypothesis was tested by studying sheep before and after the development of tachycardia-induced cardiomyopathy. METHODS: Implanted miniature radiopaque markers were used in 8 sheep to measure left ventricular geometry and function, maximal torsional deformation, and early diastolic recoil before and after rapid ventricular pacing was used to create tachycardia-induced cardiomyopathy. RESULTS: All animals had significant heart failure with ventricular dilatation and remodeling. With tachycardia-induced cardiomyopathy, maximum torsion relative to control conditions decreased (1.69 degrees +/- 0.61 degrees vs 4.25 degrees +/- 2.33 degrees ), and early diastolic recoil was completely abolished (0.53 degrees +/- 1.19 degrees vs -1.17 degrees +/- 0.94 degrees ). CONCLUSIONS: Cardiomyopathy is accompanied by decreased and delayed systolic left ventricular torsional deformation and loss of early diastolic recoil, which may contribute to left ventricular dysfunction by increasing systolic transmural strain gradients and impairing diastolic filling. Analysis of left ventricular torsion with radiofrequency-tagging magnetic resonance imaging should be explored to elucidate the role of torsion in patients with cardiomyopathy.     

Use of the Alfieri edge-to-edge technique to eliminate left ventricular outflow tract obstruction caused by mitral systolic anterior motion

A 68-year-old woman with concentric left ventricular hypertrophy, prosthetic valve endocarditis with aortic root abscess, and sepsis had aortic root replacement with an aortic allograft. On weaning from cardiopulmonary bypass, she had hemodynamic instability caused by systolic anterior motion of the mitral valve, which resulted in a left ventricular outflow tract obstruction; the peak pressure gradient across the left ventricular outflow tract was 130 mm Hg, and there was moderately severe (3+) mitral regurgitation. After reinstitution of cardiopulmonary bypass, a central Alfieri edge-to-edge stitch was placed between the anterior and posterior leaflets of the mitral valve. This reduced the gradient across the left ventricular outflow tract to 10 mm Hg and eliminated the mitral regurgitation, which enabled successful separation from cardiopulmonary bypass.     

Atrophic degeneration and loss of myocytes of residual left ventricular myocardium after Dor operation for ischemic cardiomyopathy associated with left ventricular remodeling

A 32-year-old male with familial hypercholesterolemia suffered from severe left ventricular dysfunction caused by left ventricular remodeling after myocardial infarction (ischemic cardiomyopathy), and endoventricular circular patch plasty (Dor operation) was performed. The patient’s postoperative recovery was favorable. Postoperative left ventricular function was significantly improved and the patient was discharged from our hospital. However, about 5 months later, the patient developed congestive heart failure, which progressed rapidly and irreversibly, with death at postoperative month 6. At autopsy, atrophic degeneration and loss of myocytes of the residual left ventricular myocardium were suggested to be the cause of irreversible heart failure. The postoperative balance between function of the residual myocardium and reduced left ventricular volume should be considered in cases of Dor operation for ischemic cardiomyopathy with left ventricular remodeling.     

Evaluation of cardiac function during left ventricular assist by a centrifugal blood pump

In this study, the effects on varying cardiac function during a left ventricular (LV) bypass from the apex to the descending aorta using a centrifugal blood pump were evaluated by analyzing the left ventricular pressure and the motor current of the centrifugal pump in a mock circulatory loop. Failing heart models (preload 15 mm Hg, afterload 40 mm Hg) and normal heart models (preload 5 mm Hg, afterload 100 mm Hg) were simulated by adjusting the contractility of the latex rubber left ventricle. In Study 1, the bypass flow rate, left ventricular pressure, aortic pressure, and motor current levels were measured in each model as the centrifugal pump rpm were increased from 1,000 to 1,500 to 2,000. In Study 2, the pump rpm were fixed at 1,300, 1,500, and 1,700, and at each rpm, the left ventricular peak pressure was increased from 40 to 140 mm Hg by steps of 20 mm Hg. The same measurements as in Study 1 were performed. In Study 1, the bypass flow rate and mean aortic pressure both increased with the increase in pump rpm while the mean left ventricular pressure decreased. In Study 2, a fairly good correlation between the left ventricular pressure and the motor current of the centrifugal pump was obtained. These results suggest that cardiac function as indicated by left ventricular pressure may be estimated from a motor current analysis of the centrifugal blood pump during left heart bypass.