Impact of aortic annular geometry on aortic valve insufficiency: Insights from a preclinical, ex vivo, porcine model.

OBJECTIVES: We sought to create a model of aortic insufficiency in a left heart simulator combined with 3-dimensional echocardiography and finite element modeling of the aortic valve. We examined the effects of aortic root geometry alteration on aortic insufficiency. METHODS: Porcine aortic roots were analyzed on a left heart simulator before (control, n = 8) and after intervention (n = 8). Intervention entailed 3 vertical incisions at the sinotubular junction with diamond-shaped patches incorporated into the defects to increase the sinotubular junction diameter. Hemodynamic parameters were assessed, including regurgitant volume and fraction. Video and echocardiography images evaluated aortic valve function, coaptation surface area, aortic insufficiency, and effective regurgitant orifice area. Finite element modeling corroborated relationships between root geometry and aortic insufficiency, and examined cusp stress. RESULTS: The intervention resulted in a sinotubular junction diameter increase of 55% ± 4%. The sinotubular junction to ventriculo-aortic junction diameter ratio was significantly higher in the intervention group (1.89 ± 0.16 vs 1.47 ± 0.04, P = .02). Increased sinotubular junction diameter resulted in aortic insufficiency assessed by regurgitant volume (28 ± 7 mL vs 5 ± 2 mL, P = .004), regurgitant fraction (36% ± 5% vs 7% ± 1%, P < .001), and effective regurgitant orifice (15 ± 5 mm(2) vs 0 mm(2), P = .016). Intervention coaptation surface area was smaller (1.03 ± 0.11 cm(2) vs 1.80 ± 0.08 cm(2), P < .001). There was a linear correlation between increased sinotubular junction/ventriculo-aortic junction ratio and regurgitant fraction (R(2) = 0.65, P = .003). The finite element modeling demonstrated a similar relationship between increasing sinotubular junction diameter and aortic insufficiency severity, and between end-diastolic cusp stresses and sinotubular junction diameters (R(2) = 0.98, P < .001). CONCLUSIONS: In this model, increasing sinotubular junction diameter is linearly related to reduced coaptation surface area and increasing aortic insufficiency severity. This model provides new insights into aortic insufficiency mechanisms and may be used to evaluate novel interventions for aortic valve repair.

Finding the ideal biomaterial for aortic valve repair with ex vivo porcine left heart simulator and finite element modeling.

OBJECTIVES: Aortic valve (AV) repair (AVr) has become an attractive alternative to AV replacement for the correction of aortic insufficiency; however, little clinical evidence exists in determining which biomaterial at AVr would be optimal. Cusp replacement in AVr has been associated with increased long-term AVr failure. We measured the hemodynamic and biomaterial properties using an ex vivo porcine AVr model with clinically relevant biomaterials and generated a finite element model to ascertain which materials would be best suited for valve repair. METHODS: Porcine aortic roots with intact AVs were placed in a left heart simulator mounted with a high-speed camera for baseline valve assessment. The noncoronary cusp was excised and replaced with autologous porcine pericardium, glutaraldehyde-fixed bovine pericardial patch (Synovis), extracelluar matrix scaffold (CorMatrix), or collagen-impregnated Dacron (Hemashield). The hemodynamic parameters were measured for a range of cardiac outputs (2.5-6.5 L/min) after repair. The biomaterial properties and St Jude Medical pericardial patch were determined using pressurization experiments. Finite element models of the AV and root complex were constructed to determine the hemodynamic characteristics and leaflet stresses. RESULTS: The geometric orifice areas after repair were significantly reduced in the Hemashield (P<.05) and CorMatrix (P=.0001) groups. Left ventricular work increased with increasing cardiac output (P=.001) in unrepaired valves, as expected, and was similar among all biomaterial groups. Finite element modeling of the biomaterials displayed differences in the percentage of changes in total Von Mises stress for both replaced (noncoronary cusp) and nonreplaced left and right cusps with the St Jude Medical pericardial patch (+4%, +24%) and autologous porcine pericardium (+5, +26%), with a lower percentage of changes than for the bovine pericardial patch (+12%, +27%), Hemashield (+30%, +9%), and CorMatrix (+13%, +32%). CONCLUSIONS: The present study has shown that postrepair left ventricular work did not increase despite a decrease in geometric orifice areas in the Hemashield and CorMatrix groups. The autologous porcine pericardium and St Jude Medical pericardial patch had the closest profile to normal AVs; therefore, either biomaterial might be best suited. Finally, the increased stresses found in the bovine pericardial patch, Hemashield, and CorMatrix groups might, after prolonged tensile exposure, be associated with late repair failure.

Atrial fibrillation therapies: lest we forget surgery.

Atrial fibrillation (AF) is a disease that causes a significant burden in a patient's life. It is a known risk factor for heart failure, stroke, and premature death. The classic therapeutic strategies include rate control, rhythm control, and prevention of stroke. Pharmacological rhythm control with antiarrhythmic drugs can only be achieved 50% of the time while simultaneously subjecting patients to deleterious adverse reactions. With recent advances in catheter ablation procedures, rhythm control can be safely attained anywhere from 57%-80% of the time, depending on the number of repeat catheter ablation procedures that are performed and concomitant use of antiarrhythmic drugs. The Cox-Maze procedure is a technically challenging cut-and-sew atrial lesion set with associated morbidity, yet is still considered the gold standard for rhythm control. Fortunately, this procedure has been modified in efforts to improve the safety profile (shorter cross clamp and cardiopulmonary bypass time), to simplify lesion set creation with newer energy sources, and to perform this operation in a minimally invasive setting. Minimally invasive surgical AF ablation techniques have excellent safety profiles and can achieve rhythm control in up to 90% of patients. In contrast, patients undergoing open heart surgery can undergo either concomitant endocardial or epicardial AF ablation procedures without jeopardizing the surgery along with success rates from 60% to 88%. Thus, there has been an increase in current surgical options for treating AF because of novel approaches and energy sources which yield effective long-term results in patient care and minimize perioperative complications and thereby optimize the risk/benefit ratio profile.

An update on mechanical circulatory support for heart failure therapy.

PURPOSE OF REVIEW: This article aims to review contemporary studies that utilized mechanical circulatory support (MCS) in the treatment of heart failure and to elaborate on prospective mechanical alternatives. RECENT FINDINGS: There is a growing need for a well-tolerated, durable and effective MCS option in patients with refractory heart failure. In previous years, the primary indication for MCS therapy supported bridge to transplantation. These early left ventricular assist devices (LVADs) suffered significant adverse events, thereby limiting their prolonged use. With the introduction of newer continuous flow LVADs, with lower morbidity, neurological events, pump failure and the expanded indication use (i.e. destination therapy), the overall number of implanted patients has grown. SUMMARY: There has been a dramatic advancement of durability found in the second and third-generation, continuous flow LVADs, along with improved survival rates in patients receiving these devices for destination therapy. MCS may soon become the treatment option of choice in refractory heart failure patients, especially with further evolution of less invasive approaches, smaller designs, and energy sources.

Left ventricular assist device outflow graft disconnection.

Although serious complications are becoming more rare with continuous-flow left ventricular assist devices such as the Heartmate II (Thoratec Corp, Pleasanton, CA), this case series discusses 2 patients with symptoms of bleeding and syncopal ventricular tachycardia associated with an outflow graft bend relief disconnection, which can be diagnosed by simple chest roentgenography.

Injectable small intestine submucosal extracellular matrix in an acute myocardial infarction model.

BACKGROUND: The mechanisms involved in myocardial regeneration and cardiac remodeling were examined by injecting porcine-derived small intestine submucosal extracellular matrix (SIS-ECM), with and without circulating angiogenic cells (CACs), in a mouse model of acute myocardial infarction (MI). METHODS: Nine- to 10-week-old female C57BL/6J mice had the left anterior descending (LAD) coronary artery ligated. Seven days after ligation, 38 randomly allocated animals received echocardiographically guided intramyocardial injections of phosphate buffered saline (PBS), CACs, SIS-ECM, or SIS-ECM + CACs. Repeated echocardiography and immunohistochemical analysis were performed at 28 days after ligation. RESULTS: Baseline postligation left ventricular ejection fraction (LVEF) was equivalent in all groups. Twenty-one days after treatment, ejection fraction improved in the SIS-ECM + CAC treatment group (by 38% ± 2.12%) and the SIS-ECM treatment group (by 36% ± 3.71%), compared with the CAC-alone and PBS treatment groups (p < 0.1). Masson's trichrome staining showed reduced infarct size in SIS-ECM + CACs (34.2% ± 3.1%) and SIS-ECM alone (34.5% ± 4.7%) compared with CACs alone (47.3% ± 6.0%) and PBS (61.9% ± 5.5%; p < 0.002). Arteriolar density in periinfarct regions was enhanced in both SIS-ECM-treated groups (by ≥ 78% ± 7%; p = 0.03). More GATA4- and ß-catenin-positive cardiac cells were found in the myocardium of SIS-ECM-treated animals. CONCLUSIONS: Intramyocardial delivery of SIS-ECM 7 days after MI in a mouse model reduced infarct size and improved myocardial vessel density and function; when combined with CACs it helped restore myocardial cellularity, suggesting a potential therapeutic role for SIS-ECM in cardiac regeneration.

Aortic valve cusp shearing and migration into the left main coronary artery during transcatheter aortic valve implantation.

In inoperable or high-risk patients with severe aortic stenosis, transcatheter aortic valve implantation (TAVI) provides an efficacious and safe alternative to surgical aortic valve replacement. In this case report, TAVI resulted in aortic valve cusp shearing and migration into the left main coronary artery, resulting in occlusion of coronary blood flow and cardiac arrest. The patient underwent immediate cardiopulmonary support and surgical intervention with a favourable outcome. With this case report, we illustrate the etiology and management of this complication, which can be recognized nonsurgically only if a high index of suspicion exists.

Left ventricular apical papillary fibroelastoma resection via mediastinoscope through the aortic valve.

This case report describes a novel minimally invasive technique for complete resection of a cardiac papillary fibroelastoma by directly visualizing the mass via an intraoperative mediastinoscope placed through the aortic valve. A 68-year-old man presented to the emergency department with two episodes of transient ischemic attack. Echocardiography demonstrated a pedunculated, mobile mass in the left ventricular apex. Cardiac surgery was consulted, and complete resection of the fibroelastoma was carried out by inserting a mediastinoscope through the aortic valve and into the left ventricle, whereby the mass was directly visualized and excised with biopsy forceps. There were no postoperative complications, and at 1-year follow-up, the patient had no further evidence of embolic events.