LV reverse remodeling imparted by aortic valve replacement for severe aortic stenosis; is it durable? A cardiovascular MRI study sponsored by the American Heart Association.

BACKGROUND: In patients with severe aortic stenosis (AS), long-term data tracking surgically induced effects of afterload reduction on reverse LV remodeling are not available. Echocardiographic data is available short term, but in limited fashion beyond one year. Cardiovascular MRI (CMR) offers the ability to serially track changes in LV metrics with small numbers due to its inherent high spatial resolution and low variability. HYPOTHESIS: We hypothesize that changes in LV structure and function following aortic valve replacement (AVR) are detectable by CMR and once triggered by AVR, continue for an extended period. METHODS: Twenty-four patients of which ten (67 ± 12 years, 6 female) with severe, but compensated AS underwent CMR pre-AVR, 6 months, 1 year and up to 4 years post-AVR. 3D LV mass index, volumetrics, LV geometry, and EF were measured. RESULTS: All patients survived AVR and underwent CMR 4 serial CMR's. LVMI markedly decreased by 6 months (157 ± 42 to 134 ± 32 g/m2, p < 0.005) and continued trending downwards through 4 years (127 ± 32 g/m2). Similarly, EF increased pre to post-AVR (55 ± 22 to 65 ± 11%,(p < 0.05)) and continued trending upwards, remaining stable through years 1-4 (66 ± 11 vs. 65 ± 9%). LVEDVI, initially high pre-AVR, decreased post-AVR (83 ± 30 to 68 ± 11 ml/m2, p < 0.05) trending even lower by year 4 (66 ± 10 ml/m2). LV stroke volume increased rapidly from pre to post-AVR (40 ± 11 to 44 ± 7 ml, p < 0.05) continuing to increase non-significantly through 4 years (49 ± 14 ml) with these LV metrics paralleling improvements in NYHA. However, LVmass/volume, a 3D measure of LV geometry, remained unchanged over 4 years. CONCLUSION: After initial beneficial effects imparted by AVR in severe AS patients, there are, as expected, marked improvements in LV reverse remodeling. Via CMR, surgically induced benefits to LV structure and function are durable and, unexpectedly express continued, albeit markedly incomplete improvement through 4 years post-AVR concordant with sustained improved clinical status. This supports down-regulation of both mRNA and MMP activity acutely with robust suppression long term.

Preoperative statin is associated with decreased operative mortality in high risk coronary artery bypass patients.

BACKGROUND: Statins are widely prescribed to patients with atherosclerosis. A retrospective database analysis was used to examine the role of preoperative statin use in hospital mortality, for patients undergoing isolated coronary artery bypass grafting (CABG.) METHODS: The study population comprised 2377 patients who had isolated CABG at Allegheny General Hospital between 2000 and 2004. Mean age of the patients was 65 +/- 11 years (range 27 to 92 years). 1594 (67%) were male, 5% had previous open heart procedures, and 4% had emergency surgery. 1004 patients (42%) were being treated with a statin at the time of admission. Univariate, bivariate (Chi2, Fisher's Exact and Student's t-tests) and multivariate (stepwise linear regression) analyses were used to evaluate the association of statin use with mortality following CABG. RESULTS: Annual prevalence of preoperative statin use was similar over the study period and averaged 40%. Preoperative clinical risk assessment demonstrated a 2% risk of mortality in both the statin and non-statin groups. Operative mortality was 2.4% for all patients, 1.7% for statin users and 2.8% for non-statin users (p < 0.07). Using multivariate analysis, lack of statin use was found to be an independent predictor of mortality in high-risk patients (n = 245, 12.9% vs. 5.6%, p < 0.05). CONCLUSIONS: Between 2000 and 2004 less than 50% of patients at this institution were receiving statins before admission for isolated CABG. A retrospective analysis of this cohort provides evidence that preoperative statin use is associated with lower operative mortality in high-risk patients.

Preoperative clinical factors are important determinants of the inflammatory state before and after heart surgery.

Postoperative inflammatory response is common in heart surgery patients, but less is known about variation in the baseline inflammatory state. This study characterizes the preoperative inflammatory profile in a group of high- and low-risk patients (n = 32; male 16, female 16; mean age, 70.3 +/- 1.8) and relates this to postoperative events. Interleukin-6 (IL-6), tumor necrosis factor (TNF)-alpha, TNF receptors (R1 and R2), and high-sensitivity C-reactive protein were measured before surgery and 4 hours after arrival in the intensive care unit. Considerable variability existed in all preoperative inflammatory mediators before surgery. Patients with an elevated baseline IL-6 level, (IL-6 >10 pg/mL) were older (73.5 +/- 2.2 vs. 67.9 +/- 2.6 years), had a lower ejection fraction (34 +/- 3.8% vs. 44 +/- 2.9%), a higher predicted risk score (10.3 +/- 1.2 vs. 5.9 +/- 1.1), and a higher baseline high-sensitivity C-reactive protein (65 +/- 10 vs. 24 +/- 6 mg/L), p < 0.05 for all. These patients had high morbidity and mortality rates after surgery. In addition, patients judged to be at high risk on clinical criteria were found to have consistent elevations in the baseline inflammatory state. All patients had a surge in inflammatory mediators after surgery, but those who started at a higher baseline reached a higher postoperative level than the others (IL-6 2023 +/- 561 vs. 361 +/- 47 pg/mL, p < 0.05). Many heart surgery patients, especially higher-risk patients, have a significant inflammatory state before surgery. These patients are at risk for high morbidity and mortality rates after surgery.

A femoral artery cannula that allows distal blood flow.

OBJECTIVE: A femoral artery cannula is used for certain types of circulatory support but can cause ischemia, especially during prolonged perfusion. This study tests the function of a femoral cannula designed to allow proximal and distal blood flow. METHODS: Five pigs were used in the study. In each animal a distal-flow cannula was implanted in the femoral artery of one leg, and the same-sized standard cannula was implanted in the other. Blood was drained from the left atrium and delivered to the femoral artery through the distal-flow cannula or standard cannula by using a centrifugal pump. An ultrasonic flow probe and microspheres were used to quantify flow and perfusion distal to the cannula. RESULTS: Distal femoral flow and tissue perfusion were present in all animals (5/5) with the distal-flow cannula but only in 1 of 5 animals with the standard cannula (P < .048). Distal flow did not change with pump flow. Mean distal flow at each level of pump flow was higher with the distal-flow cannula (P < .05). Tissue perfusion was also higher with the distal-flow cannula (0.052 +/- 0.028 vs 0.010 +/- 0.022 mL x min(-1) x g(-1), P < .03). CONCLUSIONS: In the swine model the distal-flow cannula allowed greater and more consistent distal flow than the standard cannula. The use of a distal-flow cannula for circulatory support might reduce the risk of distal limb ischemia.

Experimental and clinical studies with the Paracor cardiac restraint device.

Progressive cardiac enlargement is a consequence of congestive heart failure (CHF) and a cause of further deterioration. Cardiac restraint devices are intended to interrupt and reverse this process, thereby improving the natural history of CHF. The Paracor restraint device is made from a superelastic nitinol mesh that exerts a small but continuous epicardial force to relieve left ventricular (LV) wall stress and to limit LV dilation. Animal studies have used various heart failure models. The data show the device reduces LV dilation after infarction, preserves LV contractility with rapid pacing, and avoids diastolic constriction in the embolization model. Ten patients in Europe and 10 in the United States have been implanted through a small thoracotomy incision without the use of cardiopulmonary bypass. Changes in LV size, functional status, and exercise performance have been measured, but the detailed data have not yet been presented or published. The device remains experimental, pending completion of additional clinical trials.

Improvement of sternal closure stability with reinforced steel wires.

BACKGROUND: Sternal dehiscence occurs when steel wires pull through sternal bone. This study tests the hypothesis that closure stability can be improved by jacketing sternal wires with stainless steel coils, which distribute the force exerted on the bone over a larger area. METHODS: Midline sternotomies were performed in 6 human cadavers (4 male). Two sternal closure techniques were tested: (1) approximation with six interrupted wires, and (2) the same closure technique reinforced with 3.0-mm-diameter stainless steel coils that jacket wires at the lateral and posterior aspects of the sternum. Intrathoracic pressure was increased with an inflatable rubber bladder placed beneath the anterior chest wall, and sternal separation was measured by means of sonomicrometry crystals. In each trial, intrathoracic pressure was increased until 2.0 mm of motion was detected. Differences in displacement pressures between groups were examined at 0.25-mm intervals using the paired Student's t test. RESULTS: The use of coil-reinforced closures produced significant improvement in sternal stability at all eight displacement levels examined (p < 0.03). Mean pressure required to cause displacement increased 140% (15.5 to 37.3 mm Hg) at 0.25 mm of separation, 103% (34.3 to 69.8 mm Hg) at 1.0 mm of separation, and 122% (46.8 to 103.8 mm Hg) at 2.0 mm of separation. CONCLUSIONS: Reinforcement of sternal wires with stainless steel coils substantially improves stability of sternotomy closure in a human cadaver model.

Lower sternal reinforcement improves the stability of sternal closure.

BACKGROUND: This study uses a mechanical testing system to evaluate three methods of sternal closure. METHODS: Twelve sternal replicas composed of a polyurethane foam bone analogue were divided in the midline and reapproximated using three stainless steel wire techniques: six simple wires (6S), six figure-of-eight wires (6F8), or seven simple wires (7S), which included an extra wire at the lower sternum. The closures were subjected to increasing lateral distraction from 0 to 400 Newtons (N) (1 N = 0.224 lbs), and motion was measured using transducers stationed across the manubrium, midsternum, and lower sternum. RESULTS: With each method of closure, the manubrium was the most stable, the lower sternum the least stable, and the midsternum intermediate between the other two. There were also differences between sternal closure methods, but only at the lower sternum. Less sternal distraction was measured with the 7S than the 6S and 6F8 methods, starting at 100 N (0.20 +/- 0.06 mm vs 0.48 +/- 0.19 and 0.39 +/- 0.10, p = 0.003), and progressively increasing until the study was stopped at 400 N (1.64 +/- 0.39 mm vs 4.92 +/- 1.73 and 5.1 +/- 1.43 mm, p = 0.003). CONCLUSIONS: These data show that the lower sternum is the site of greatest instability and that reinforcement of this area with an additional wire effectively stabilizes the closure. Figure-of-eight wires are not superior to simple wires.

Validation of a bone analog model for studies of sternal closure.

BACKGROUND: The incidence of serious sternal wound complications may be reduced with improvements in closure methods. Biomechanical testing of median sternotomy closures in cadavers has proven useful but is limited by availability, high cost, and wide variations in the material properties of the sterna. This study tests whether artificial sterna can be used to replace whole cadavers in sternal closure testing. METHODS: Two common wire closure techniques were tested using both whole cadavers and artificial sternal models formed from bone analogue material. Sternal models were molded from polyurethane foam (20 lbs/ft3) to simulate the mechanical properties observed in human cadaveric sterna. The force vector previously identified as the most detrimental to sternal cohesion (lateral traction) was used to stress the closures. Separation of the incision site was measured at the manubrium, midsternum, and xiphoid and data were compared between cadaver and bench test groups. RESULTS: Sternal separations recorded in cadavers were found to be similar to bench test results for both closure types. Data variability within test groups was found to be consistently lower using artificial sterna, where peak standard deviations for sternal motion averaged less than half that measured in cadavers. CONCLUSIONS: Results suggest that anatomic sternal models formed from solid polyurethane foam can be used to approximate the biomechanical properties of cadaveric sterna and that reliable information regarding sternal closure stability can be secured through this means. Moreover, bench test data were shown to be less variable than cadaveric results, thus enhancing the power to detect small differences in sternal fixation stability.

Reverse remodeling and improved regional function after repair of left ventricular aneurysm.

BACKGROUND: Changes in regional left ventricular mechanics after anteroapical aneurysm repair in human subjects can be studied noninvasively by means of magnetic resonance tagging. We hypothesized that left ventricular intramyocardial function would improve throughout the left ventricle after repair. METHODS: We studied 6 male patients with a left ventricular anteroapical aneurysm (mean age +/- SD, 63 +/- 5 years) using magnetic resonance tagging 3 +/- 1 weeks before and 6 +/- 1 weeks after aneurysm repair, coronary artery bypass grafting, and mitral valve repair (n = 2). Breath-hold tagged imaging spanned the left ventricle in the short axis from apex to base. Left ventricular mass, end-diastolic and end-systolic volume, and ejection fraction were measured. Two-dimensional strain analysis was applied; averaged for the apical, middle, and basal left ventricle and the whole left ventricle; and expressed as greatest lengthening (similar to wall thickening), greatest shortening, and angular deviation of the lengthening strain from the radial direction. RESULTS: After aneurysm repair, left ventricular mass decreased from 373 +/- 27 to 333 +/- 25 g (P <.05), end-diastolic volume from 212 +/- 22 to 168 +/- 18 mL (P <.005), and end-systolic volume from 188 +/- 26 to 113 +/- 18 mL (P <.005); ejection fraction improved from 13% +/- 4% to 23% +/- 4% (P <.005). For the whole left ventricle, lengthening strain increased from before to after the operation (8% +/- 1% to 10% +/- 1%, P <.01). Most of the improved lengthening occurred at the middle left ventricle (8% +/- 1% to 11% +/- 1%, P <.01), in the base (8% +/- 1% to 10% +/- 1%, P <.05), and in the inferior wall (9% +/- 1% to 12% +/- 1%, P <.05). Lengthening tended to become more radially oriented, decreasing from 31 degrees +/- 3 degrees to 27 degrees +/- 3 degrees (P =.10). Shortening strain did not change (10% +/- 1% to 11% +/- 1%, P = not significant). CONCLUSIONS: Left ventricular aneurysm repair is associated with reverse remodeling and an improvement in the extent and orientation of intramyocardial function, especially at the middle and basal left ventricle and inferior wall.

Left pleural effusion after coronary artery bypass decreases with a supplemental pleural drain.

BACKGROUND: This prospective study was undertaken to determine the incidence of symptomatic left pleural effusion after coronary artery bypass grafting, and to determine if routine drainage of the pleural cavity with a supplemental flexible drain reduces this incidence. METHODS: The clinical course of study patients was prospectively recorded during the initial hospitalization and at 6-weeks after surgery. All patients had a mediastinal and a left pleural tube, which were removed on the 1st postoperative day. The supplemental drain system was implanted in a subset of patients and remained in place for 3 to 5 days. A symptomatic effusion was defined as one that required thoracentesis, tube thoracostomy, or readmission for treatment. RESULTS: A total of 460 patients were studied, of whom 115 had a supplemental drain. The two groups (supplemental drain versus control) were equivalent with respect to age, gender distribution, and comorbid diseases. The incidence of symptomatic left pleural effusion for the entire group was 9.8% (45 of 460). Symptomatic left pleural effusion occurred in 11.9% (41 of 345) patients when only chest tubes were used, and in 3.5% (4 of 115) when a supplemental drain was placed. This difference was significant (F ratio 7.583, p < 0.005). There were no complications from the supplemental drain. CONCLUSIONS: The incidence of symptomatic left pleural effusion can be greatly reduced with the use of a supplemental pleural drain that remains in place for several days after surgery.

Dynamic Cardiomyoplasty.

On January 8, 1985, Carpentier and his cardiovascular surgery group at the Broussais Hospital were the first to replace diseased human myocardium with a stimulated latissimus dorsi muscle flap. A few months later, Magovern and co-workers at Allegheny General Hospital in Pittsburgh were the first to repair a large left ventricular aneurysm with a latissimus dorsi cardiomyoplasty. Over the past six years, approximately 120 patients have undergone the operation throughout the world.