Frederick Y. Chen

Early and late outcomes of 1000 minimally invasive aortic valve operations.

OBJECTIVE Minimal access cardiac valve surgery is increasingly utilized. We report our 11-year experience with minimally invasive aortic valve surgery. METHODS From 07/96 to 12/06, 1005 patients underwent minimally invasive aortic valve surgery. Early and late outcomes were analyzed. RESULTS Median patient age was 68 years (range: 24-95), 179 patients (18%) were 80 years or older, 130 patients (13%) had reoperative aortic valve surgery, 86 (8.4%) had aortic root replacement, 62 (6.1%) had concomitant ascending aortic replacement, and 26 (2.6%) had percutaneous coronary intervention on the day of surgery (hybrid procedure). Operative mortality was 1.9% (19/1005). The incidences of deep sternal wound infection, pneumonia and reoperation for bleeding were 0.5% (5/1005), 1.3% (13/1005) and 2.4% (25/1005), respectively. Median length of stay was 6 days and 733 patients (72%) were discharged home. Actuarial survival was 91% at 5 years and 88% at 10 years. In the subgroup of the elderly (> or =80 years), operative mortality was 1.7% (3/179), median length of stay was 8 days and 66 patients (37%) were discharged home. Actuarial survival at 5 years was 84%. There was a significant decreasing trend in cardiopulmonary bypass time, the incidence of bleeding, and operative mortality over time. CONCLUSIONS Minimal access approaches in aortic valve surgery are safe and feasible with excellent outcomes. Aortic root replacement, ascending aortic replacement, and reoperative surgery can be performed with these approaches. These procedures are particularly well-tolerated in the elderly.

Early and late outcomes in minimally invasive mitral valve repair: An eleven-year experience in 707 patients

OBJECTIVE This study analyzes a single institution experience with minimally invasive mitral valve repair and evaluates long-term surgical outcomes of morbidity, mortality, and rates of reoperation. Late follow-up of mitral regurgitation and left ventricular function were also assessed. METHODS Between August 1996 and October 2007, minimally invasive mitral valve repair was performed in 713 patients (mean follow-up 5.7 years). Excluding 6 repairs with robotic assistance, an perspective analysis of the remaining 707 patients was carried forth. Mean age was 57 +/- 13 years. Mean preoperative ejection fraction was 60% +/- 10%. Surgical access was through a lower ministernotomy (74%), right parasternal incision (24%), right thoracotomy (1.4%), or upper ministernotomy (0.7%). Exposure of the mitral valve was through the left atrium in 58% of the cases and transeptal in 42%. A ring annuloplasty was incorporated into 680 (96%) of 707 repairs. The Kaplan-Meier and Student t test for paired samples were used for statistical analysis. RESULTS There were 3 (0.4%) operative deaths. Perioperative morbidity included new-onset atrial fibrillation (20%), reoperation for bleeding (2%), stroke (1.9%), permanent pacemaker implantation (1.7%), deep sternal wound infection (0.7%), and aortic dissection (0.4%). Median hospital stay was 5 days. Only 31% of patients required blood transfusion during the hospital course. There were 49 (6.9%) late deaths and 34 (4.8%) failed repairs necessitating reoperation. At 11.2 years, survival was 83% (95% confidence intervals, 76.5-88.1); freedom from reoperation was 92% (95% confidence intervals, 86.2-94.9). Nine (1.3%) patients were lost to follow-up. A total of 2369 patient-years of echocardiography time were obtained in 544 patients (mean 4.36 years, range 0.47-11.09). Mean grade of mitral regurgitation decreased from 3.80 to 1.42 (P < .0001) Mean left ventricular ejection fraction decreased from 60.7% to 56.3% (P < .0001). Combined risk of death, reoperation, and recurrence of moderately severe to severe mitral regurgitation was 7.7% (43/555). CONCLUSION Minimally invasive mitral valve repair is safe, with low perioperative morbidity, low rates of recurrent mitral regurgitation, and low rates of reoperation and death at late follow-up.

Real-time assessment of cardiac perfusion, coronary angiography, and acute intravascular thrombi using dual-channel near-infrared fluorescence imaging

OBJECTIVES We have developed an image-guided surgical system based on invisible near-infrared fluorescent light. Presently, the only clinically available near-infrared fluorophore is indocyanine green, which fluoresces at approximately 800 nm and is used for coronary angiography. Our objective was to determine whether methylene blue, already US Food and Drug Administration approved for other indications, has useful near-infrared fluorescence properties for image-guided cardiac surgery. METHODS The optical properties of methylene blue were measured after dissolution in 100% serum. Biodistribution and clearance were quantified in organs and tissue after intravenous bolus injection of 2 mg/kg methylene blue in 3 rats. Coronary arteriography and cardiac perfusion were imaged in real time after intravenous bolus injection of 1 mg/kg methylene blue in 5 pigs with coronary obstructions. Coronary angiography and acute thrombi were assessed by using 800-nm fluorophores, indocyanine green, and IR-786-labeled platelets, respectively. RESULTS The peak absorbance and emission of methylene blue as a near-infrared fluorophore occur at 667 nm and 686 nm, respectively. After intravenous injection, methylene blue provides highly sensitive coronary angiography. A lipophilic cation, methylene blue is extracted rapidly into tissue, with myocardium displaying unusually high uptake. Methylene blue permits real-time visualization and quantitative assessment of myocardial perfusion. Because of absent spectral overlap, use of 2 independent fluorophores in our imaging system permits simultaneous quantification of perfusion, venous drainage, and/or intravascular thrombi. CONCLUSIONS Methylene blue is an effective near-infrared fluorophore that provides direct visualization of coronary arteriography and cardiac perfusion. In conjunction with approximately 800-nm near-infrared fluorophores, important functional assessments during cardiac surgery are also possible.

Adjustable, Physiological Ventricular Restraint Improves Left Ventricular Mechanics and Reduces Dilatation in an Ovine Model of Chronic Heart Failure

Background— Ventricular restraint is a nontransplantation surgical treatment for heart failure. The effect of varying restraint level on left ventricular (LV) mechanics and remodeling is not known. We hypothesized that restraint level may affect therapy efficacy. Methods and Results— We studied the immediate effect of varying restraint levels in an ovine heart failure model. We then studied the long-term effect of restraint applied over a 2-month period. Restraint level was quantified by use of fluid-filled epicardial balloons placed around the ventricles and measurement of balloon luminal pressure at end diastole. At 4 different restraint levels (0, 3, 5, and 8 mm Hg), transmural myocardial pressure (Ptm) and indices of myocardial oxygen consumption (M&OV0312;O2) were determined in control (n=5) and ovine heart failure (n=5). Ventricular restraint therapy decreased Ptm and M&OV0312;O2, and improved mechanical efficiency. An optimal physiological restraint level of 3 mm Hg was identified to maximize improvement without an adverse affect on systemic hemodynamics. At this optimal level, end-diastolic Ptm and M&OV0312;O2 indices decreased by 27% and 20%, respectively. The serial longitudinal effects of optimized ventricular restraint were then evaluated in ovine heart failure with (n=3) and without (n=3) restraint over 2 months. Optimized ventricular restraint prevented and reversed pathological LV dilatation (130±22 mL to 91±18 mL) and improved LV ejection fraction (27±3% to 43±5%). Measured restraint level decreased over time as the LV became smaller, and reverse remodeling slowed. Conclusions— Ventricular restraint level affects the degree of decrease in Ptm, the degree of decrease in M&OV0312;O2, and the rate of LV reverse remodeling. Periodic physiological adjustments of restraint level may be required for optimal restraint therapy efficacy.

Is early antithrombotic therapy necessary in patients with bioprosthetic aortic valves in normal sinus rhythm

OBJECTIVE Current American Heart Association/American College of Cardiology guidelines recommend anticoagulation and antiplatelet therapy during the first 90 postoperative days; however, there is wide variability in the administration of antithrombotic therapy after bioprosthetic aortic valve replacement. We sought to determine whether early antithrombotic therapy was necessary in patients undergoing isolated bioprosthetic aortic valve implantation and who were discharged in normal sinus rhythm. METHODS From December 2001 to October 2008, 1131 patients underwent isolated bioprosthetic aortic valve implantation at Brigham and Womens Hospital. After exclusion of patients who underwent concomitant operations (n = 138, 12%), patients who were anticoagulated preoperatively (n = 4, 0.4%), and patients who experienced postoperative refractory atrial fibrillation requiring anticoagulation at discharge (n = 128, 11%), our study base consisted of 861 patients. Patients were followed for 90 days postoperatively for the occurrence of thromboembolism, including stroke, transient ischemic attack, or peripheral thromboembolic events and bleeding complications. RESULTS Of the 861 patients included in this study, 133 (15%) were anticoagulated with warfarin sodium (AC+) postoperatively and 728 (85%) were not (AC-). Patients who received postoperative anticoagulation were older; had a higher incidence of hypertension, cerebrovascular accident, and pulmonary vascular disease; and were more symptomatic at presentation. The 90-day risk of thromboembolism (cerebrovascular accident, transient ischemic attack, or peripheral thromboembolism) after surgery was 5% (n = 6) in those who were anticoagulated and 5% (n = 39) in those who were not (P = .67). Independent predictors of thromboembolism were found to be increasing age (odds ratio, 1.03; P = .03), female gender (odds ratio, 2.23; P = .005), short stature (odds ratio, 0.97; P = .002), smoking status (P = .05), New York Heart Association III/IV (odds ratio 1.77, P = .04), and a 19-mm bioprosthetic aortic valve prosthesis (odds ratio, 2.22; P = .03). Evaluation of each predictor with postoperative acetylsalicylic acid+ and AC+ interaction terms revealed that female patients (odds ratio, 0.75; P = .03 AC+; odds ratio, 0.66; P = .02 acetylsalicylic acid+) and patients with a 19-mm bioprosthetic aortic valve (odds ratio, 0.65; P = .02 AC+; odds ratio, 0.36; P = .01 acetylsalicylic acid+) had a reduction in the incidence of thromboembolism when administered acetylsalicylic acid or warfarin sodium. Patients who were in New York Heart Association III/IV also had a reduction of thromboembolism when given vitamin K antagonist (odds ratio, 0.73; P = .04); a similar trend was observed in patients given acetylsalicylic acid (odds ratio, 0.34; P = .06). CONCLUSION Early anticoagulation after isolated bioprosthetic aortic valve replacement in patients in normal sinus rhythm does not seem to reduce the risk of thromboembolism except in high-risk groups. Current recommendations should be revisited, because the only patients who may benefit from anticoagulation are female, those who are highly symptomatic, and those with a small aortic prosthesis.

Recurrence of mitral regurgitation after partial versus complete mitral valve ring annuloplasty for functional mitral regurgitation.

OBJECTIVES Both partial and complete annuloplasty rings are used for mitral valve repair for patients with functional mitral regurgitation (FMR). We sought to determine if recurrence of mitral regurgitation (MR) is affected by the type of ring used. METHODS Five hundred forty-eight patients diagnosed with FMR underwent mitral valve repair with ring annuloplasty between 1998 and 2008 in our institution. Medical records were reviewed retrospectively for clinical and echocardiographic data to determine the presence of recurrent MR (defined as moderate or severe). RESULTS Among 479 patients for whom postoperative echocardiographic data were available, recurrent MR occurred less frequently in the complete versus partial ring group (20 of 209 [10%] vs 56 of 270 [21%] patients; P = .001), despite lower preoperative ejection fractions in the complete ring group (median, 35%; interquartile range, 25%-45% vs median, 40%; interquartile range, 30%-55%; P < .001). Kaplan-Meier analysis demonstrated greater freedom from recurrent MR in the complete ring group (108 vs 103 months; P = .001). Risk-matched propensity analysis of 102 patients per group (area under the curve, 0.824; 95% confidence interval, 0.788-0.861; P < .001) also demonstrated that complete ring recipients had greater freedom from recurrent MR than partial ring recipients by univariate analysis (7 [7%] vs 17 [17%] patients; P = .049), and a trend toward greater freedom by Kaplan-Meier analysis (110 vs 104 months; P = .068). CONCLUSIONS The use of complete mitral annuloplasty rings provides improved freedom from recurrent MR in patients with FMR.

Postoperative Recurrence of Mitral Regurgitation After Annuloplasty for Functional Mitral Regurgitation

BACKGROUND We investigated predictive factors of postoperative recurrence of mitral regurgitation (MR) after mitral valve annuloplasty for functional ischemic MR. METHODS This study was a retrospective review of patients with functional MR who underwent mitral ring annuloplasty at our institution from 1998 to 2008. Records were reviewed for perioperative variables, including echocardiographic measurements. Recurrence was defined as MR grade moderate (3+) or greater on any postoperative echocardiogram. RESULTS Of 548 patients who underwent mitral annuloplasty for functional MR, echocardiogram reports were available for review for 250. These patients comprised the study cohort. There were 154 patients with concomitant coronary artery bypass grafting. The left ventricular (LV) end-diastolic (LVED) index was calculated by dividing the LVED dimension by body surface area (BSA). A high LVED index (>3.5 cm/m2) was predictive of MR recurrence (p=0.047): the recurrence rate was 20.3% (13 of 64) in high-index patients and 10.2% (19 of 186) in low-index (<3.5 cm/m2) patients. Median recurrence-free survival was 35 months (range, 19 to 59 months) in high-LVED-index patients and 46.5 months (range, 22 to 75 months) in low-LVED-index patients (p=0.048). Preoperative MR severity and LV ejection fraction were not predictive of MR recurrence. CONCLUSIONS Careful analysis of the preoperative echocardiogram using a novel, easily calculated variable, the LVED index, may help identify patients who are at greater risk for MR recurrence and reduced survival. Such information could prompt consideration of alternative or additional interventions in these patients.

Functional Mitral Regurgitation

Functional mitral regurgitation (MR) is a common clinical entity which will likely increase in the future due to predicted demographic changes. It is also associated with poor long-term survival. The anatomic structure of the mitral valve apparatus is complex and consists of several components, each of which can be affected by a variety of diseases resulting in MR. In primary MR, the valvular incompetence is caused by compromised or structurally disrupted components of the valve apparatus; the valve in functional MR is structurally normal, with the regurgitation resulting from failure of coaptation of the mitral valve leaflets without coexisting structural changes of the valve itself. Therefore, we defined functional MR as a systolic retrograde flow from the left ventricle into the left atrium due to reduction and/or elimination of the normal systolic coaptation of the mitral valve leaflets. A slow progression of the symptoms is typical for this valve disease and often ends in irreversible left ventricular dysfunction. The pathophysiology and treatment of functional MR are quite complex. This article reviews and summarizes the existing literature, with a focus on the pathophysiology and current treatment of functional MR.

Ventricular assist device in patients with prosthetic heart valves.

Ventricular assist device (VAD) support inpatients with a prosthetic heart valve had previously been considered a relative contraindication due to an increased risk of thromboembolic complications. We report our clinical experience of VAD implantation in patients with prosthetic heart valves, including both mechanical and bioprosthetic valves. The clinical records of 133 consecutive patients who underwent VAD implantation at a single institution from January 2002 through June 2009 were retrospectively reviewed. Six of these patients had a prosthetic valve in place at the time of device implantation. Patient demographics,operative characteristics, and postoperative complications were reviewed.Of the six patients,four were male.The mean age was 57.8 years (range 35–66 years). The various prosthetic cardiac valves included a mechanical aortic valve (n = 2), a bioprosthetic aortic valve (n = 3), and a mechanical mitral valve (n = 1).The indications for VAD support included bridge to transplantation (n = 2), bridge to recovery (n = 1), and postcardiotomy ventricular failure(n = 3). Three patients underwent left ventricular assist device placement and three received a right ventricular assist device. Postoperatively, standard anticoagulation management began with a heparin infusion (if possible)followed by oral anticoagulation.The 30-day mortality was50% (3/6). The mean duration of support among survivors was 194.3 days (range 7–369 days) compared with 16.0 days(range 4–29 days) for nonsurvivors. Of the three survivors,two were successfully bridged to heart transplantation and one recovered native ventricular function.Among the three nonsurvivors,acute renal failure developed in each case, and two developed heparin-induced thrombocytopenia. This study suggests that VAD placement in patients with a prosthethic heart valve, either mechanical or bioprosthetic,appears to be a reasonable option.

Hemodynamic Changes in a Model of Chronic Heart Failure Induced by Multiple Sequential Coronary Microembolization in Sheep

Although a large variety of animal models for acute ischemia and acute heart failure exist, valuable models for studies on the effect of ventricular assist devices in chronic heart failure are scarce. We established a stable and reproducible animal model of chronic heart failure in sheep and aimed to investigate the hemodynamic changes of this animal model of chronic heart failure in sheep. In five sheep (n = 5, 77 +/- 2 kg), chronic heart failure was induced under fluoroscopic guidance by multiple sequential microembolization through bolus injection of polysterol microspheres (90 microm, n = 25.000) into the left main coronary artery. Coronary microembolization (CME) was repeated up to three times in 2 to 3-week intervals until animals started to develop stable signs of heart failure. During each operation, hemodynamic monitoring was performed through implantation of central venous catheter (central venous pressure [CVP]), arterial pressure line (mean arterial pressure [MAP]), implantation of a right heart catheter {Swan-Ganz catheter (mean pulmonary arterial pressure [PAP mean])}, pulmonary capillary wedge pressure (PCWP), and cardiac output [CO]) as well as pre- and postoperative clinical investigations. All animals were followed for 3 months after first microembolization and then sacrificed for histological examination. All animals developed clinical signs of heart failure as indicated by increased heart rate (HR) at rest (68 +/- 4 bpm [base] to 93 +/- 5 bpm [3 mo][P < 0.05]), increased respiratory rate (RR) at rest (28 +/- 5 [base] to 38 +/- 7 [3 mo][P < 0.05]), and increased body weight 77 +/- 2 kg to 81 +/- 2 kg (P < 0.05) due to pleural effusion, peripheral edema, and ascites. Hemodynamic signs of heart failure were revealed as indicated by increase of HR, RR, CVP, PAP, and PCWP as well as a decrease of CO, stroke volume, and MAP 3 months after the first CME. Multiple sequential intracoronary microembolization can effectively induce myocardial dysfunction with clinical and hemodynamic signs of chronic ischemic cardiomyopathy. The present model may be suitable in experimental work on heart failure and left ventricular assist devices, for example, for studying the impact of mechanical unloading, mechanisms of recovery, and reverse remodeling.