Katherine B. Harrington

Importance of Mitral Valve Second-Order Chordae for Left Ventricular Geometry, Wall Thickening Mechanics, and Global Systolic Function

Background—Mitral valvular–ventricular continuity is important for left ventricular (LV) systolic function, but the specific contributions of the anterior leaflet second-order “strut” chordae are unknown. Methods and Results—Eight sheep had radiopaque markers implanted to silhouette the LV, annulus, and papillary muscles (PMs); 3 transmural bead columns were inserted into the mid-lateral wall between the PMs. The strut chordae were encircled with exteriorized wire snares. Three-dimensional marker images and hemodynamic data were acquired before and after chordal cutting. Preload recruitable stroke work (PRSW) and end-systolic elastance (Ees) were calculated to assess global LV systolic function (n=7). Transmural strains were measured from bead displacements (n=4). Chordal cutting caused global LV dysfunction: Ees (1.48±1.12 versus 0.98±1.30 mm Hg/mL, P=0.04) and PRSW (69±16 versus 60±15 mm Hg, P=0.03) decreased. Although heart rate and time from ED to ES were unchanged, time of mid-ejection was delayed (125±18 versus 136±19 ms, P=0.01). Globally, the LV apex and posterior PM tip were displaced away from the fibrous annulus and LV base-apex length increased at end-diastole and end-systole (all +1 mm, P<0.05). Locally, subendocardial end-diastolic strains occurred: Longitudinal strain (E22) 0.030±0.013 and radial thickening (E33) 0.081±0.041 (both P<0.05 versus zero). Subendocardial systolic shear strains were also perturbed: Circumferential-longitudinal “micro-torsion” (E12) (0.099±0.035 versus 0.075±0.025) and circumferential radial shear (E13) (0.084±0.023 versus 0.039±0.008, both P<0.05). Conclusion—Cutting second-order chords altered LV geometry, remodeled the myocardium between the PMs, perturbed local systolic strain patterns affecting micro-torsion and wall-thickening, and caused global systolic dysfunction, demonstrating the importance of these chordae for LV structure and function.

Aortic valve and ascending aorta guidelines for management and quality measures: executive summary.

The Society of Thoracic Surgeons Clinical Practice Guidelines are intended to assist physicians and other health care providers in clinical decision making by describing a range of generally acceptable approaches for the diagnosis, management, or prevention of specific diseases or conditions. These guidelines should not be considered inclusive of all proper methods of care or exclusive of other methods of care reasonably directed at obtaining the same results. Moreover, these guidelines are subject to change over time, without notice. The ultimate judgment regarding the care of a particular patient must be made by the physician in light of the individual circumstances presented by the patient.

Cutting second-order chords does not prevent acute ischemic mitral regurgitation.

Background—Cutting anterior mitral leaflet second-order chordae has been proposed for repair in ischemic mitral regurgitation (IMR). We examined the efficacy of such chordal cutting in preventing acute IMR. Methods and Results—Six sheep underwent radiopaque marker placement (left ventricle, mitral annulus, papillary muscles [PMs], and leaflets). The largest second-order chord from each PM was encircled with exteriorized wire snares. Three-dimensional marker coordinates were obtained with biplane videofluoroscopy before and during acute ischemia (80 seconds of mid-circumflex occlusion). Color Doppler transesophageal echocardiography was used to grade MR on a 0 to 4+ scale. Data were acquired immediately before and after dividing second-order chordae. Slope of the end-diastolic volume–stroke work relationship (PRSW) was calculated to assess systolic function. Chordal cutting increased anterior leaflet inflection angle (155±12 versus 162±9 degrees; P=0.03), resulting in a flatter leaflet, but did not increase effective leaflet length (1.97±0.24 versus 2.08±0.23 cm; P=0.15); PRSW decreased (63±15 versus 56±12 mm Hg; P=0.008). Both before and after chordal cutting, ischemia caused: Septal–lateral annular dilation (P=0.005), posterior PM displacement away from the mid-septal annulus (P=0.06), increased leaflet tenting area (P=0.001), and increased leaflet tenting volume (P=0.002). Before chordal cutting, MR increased significantly during ischemia (0.5±0.3 versus 1.7±0.4; P<0.001), and IMR increased similarly even after the second-order chords were cut (0.7±0.4 versus 1.9±0.9; P<0.001). Conclusions—Cutting second-order chordae resulted in LV systolic dysfunction and neither prevented nor decreased the severity of acute IMR, septal–lateral annular dilation, leaflet tenting area, or leaflet tenting volume.

Myofiber angle distributions in the ovine left ventricle do not conform to computationally optimized predictions

Recent computational models of optimized left ventricular (LV) myofiber geometry that minimize the spatial variance in sarcomere length, stress, and ATP consumption have predicted that a midwall myofiber angle of 20 degrees and transmural myofiber angle gradient of 140 degrees from epicardium to endocardium is a functionally optimal LV myofiber geometry. In order to test the extent to which actual fiber angle distributions conform to this prediction, we measured local myofiber angles at an average of nine transmural depths in each of 32 sites (4 short-axis levels, 8 circumferentially distributed blocks in each level) in five normal ovine LVs. We found: (1) a mean midwall myofiber angle of -7 degrees (SD 9), but with spatial heterogeneity (averaging 0 degrees in the posterolateral and anterolateral wall near the papillary muscles, and -9 degrees in all other regions); and (2) an average transmural gradient of 93 degrees (SD 21), but with spatial heterogeneity (averaging a low of 51 degrees in the basal posterior sector and a high of 130 degrees in the mid-equatorial anterolateral sector). We conclude that midwall myofiber angles and transmural myofiber angle gradients in the ovine heart are regionally non-uniform and differ significantly from the predictions of present-day computationally optimized LV myofiber models. Myofiber geometry in the ovine heart may differ from other species, but model assumptions also underlie the discrepancy between experimental and computational results. To test the predictive capability of the current computational model would we propose using an ovine specific LV geometry and comparing the computed myofiber orientations to those we report herein.

CASE 4—2014Ascending Aortic Pseudoaneurysm Repair With Deep Hypothermic Circulatory Arrest in an Adult Congenital Heart Disease Patient With Heparin-Induced Thrombocytopenia

Preoperative transthoracic echocardiography was notable for a mildly reduced left ventricular ejection fraction (47%), moderate stenosis of the mechanical valve in the pulmonic position (peak gradient 59 mmHg), and a well-seated mechanical prosthesis in the aortic position, without stenosis. Gated computed tomography angiography (Fig 1) showed the pseudoaneurysm and the proximity of the lesion to the coronary arteries. Multidisciplinary planning included the use of bivalirudin (The Medicines Company, Parsippany, NJ) at a targeted activated coagulation time (ACT) of 250-300 seconds to facilitate endovascular repair through the retrograde deployment of a stent from open access to the left common carotid artery through a neck incision. After uneventful initiation of general anesthesia and line placement (left radial arterial cannula, right internal jugular triple lumen, and introducer sheath catheters), the endovascular stent graft (Zenith TX2 36� 50 mm stent graft, Cook Medical, Bloomington, IN) was deployed but did not completely cover the pseudoaneurysm, so a second stent graft was inserted under a combination of fluoroscopic and transesophageal echocardiographic (TEE) guidance. However, adequate positioning could not be achieved during deployment of the second stent, and the device remained malpositioned in the arch. No hemodynamic changes occurred despite stent malposition. At the time, TEE did not show evidence of aortic dissection; left ventricular function remained at baseline (mildly depressed) without dynamic changes to suggest ischemia. Because the attempted endovascular repair had been performed in the cardiac catheterization suite (this institution does not have

OUTCOMES OF TREATMENT OF NONAGENARIANS WITH SEVERE AORTIC STENOSIS

With an increasingly aging population, examination of outcomes of the treatment options for elderly patients with severe aortic stenosis (AS) is relevant. Patients >90 years from 4/2007-4/2013 who underwent surgical aortic valve replacement (SAVR) or transcatheter AVR (TAVR) for severe AS were

Anesthetic management for reentry sternotomy in a patient with a full stomach and pericardial tamponade from left ventricular rupture

A 57-year-old man presented with chest pain and shortness of breath 1 month after left ventricular aneurysmectomy and ventricular septal defect closure for post-infarct left ventricular aneurysm and ventricular septal defect. Echocardiography revealed a large recurrent ruptured inferior left ventricular aneurysm with high-velocity flow into a 5 cm posterolateral pericardial effusion. Thirty minutes earlier, the patient had eaten a full meal. Rapid sequence induction was performed with midazolam, ketamine, and succinylcholine. Moderate hypotension was treated effectively and the patient tolerated controlled transition to cardiopulmonary bypass. The ventricular defect was oversewn and reinforced with bovine pericardium. The patient had a difficult but ultimately successful recovery. Options for anesthetic management in the setting of tamponade and a full stomach are discussed, with a brief review of the evidence relating to this clinical problem.