Amar Krishnaswamy

Transcatheter aortic valve replacement: current perspectives and future implications

Transcatheter aortic valve replacement (TAVR) or transcatheter aortic valve implantation (TAVI) has emerged as an attractive treatment strategy for the treatment of patients with severe symptomatic aortic stenosis (AS), particularly those who are inoperable or at high risk for surgical aortic valve replacement. Several multicentre registries and randomised trials have demonstrated the safety and efficacy of this technology in improving the survival as well as functional capacity of patients with AS. Most of the elderly patients with severe AS have multiple non-cardiac comorbidities, which might limit survival and impede the improvement in functional capacity afforded by TAVR. Therefore, optimal patient selection based on precise risk assessment is currently the cornerstone of evaluation of patients for TAVR. Due to the need for a multifaceted approach in patient evaluation, procedural conduct as well as postprocedure management, multidisciplinary heart valve teams have assumed a paramount role in the TAVR process. This review presents the current perspectives in patient selection, risk assessment, procedural considerations and outcomes following TAVR, along with implications for the future.

Three-dimensional computed tomography in the cardiac catheterization laboratory†

Objectives: To establish the feasibility of fusion of a 3‐dimensional computed tomography (3D CT) dataset to the routine fluoroscopic image in the cardiac catheterization laboratory. Background: Routine fluoroscopic imaging in the cardiac catheterization laboratory often does not provide adequate anatomic detail for structural cardiac interventions. The modern C‐arm is capable of acquiring CT‐like 3D images (Syngo DynaCT), and the overlay of CT‐acquired details on the fluoroscopic image may be useful. The feasibility of this new technology has not yet been reported. Methods: Three patients (presenting with three different clinical indications) were selected, all of whom had previously undergone contrast‐enhanced chest CT. Anatomic details of interest were marked on the preprocedural CT, and the CT was registered to a DynaCT acquired in the catheterization laboratory. The CT:CT registration was then fused to the “real‐time” fluoroscopic image. Results: Fusion of the CT to the fluoroscopic image was successful in these three patients and provided a substantial degree of anatomic guidance for catheter and device manipulation. Conclusions: We have demonstrated the ability to delineate cardiovascular structures of interest on the “real‐time” fluoroscopic image using CT fusion. Future studies should address whether this technology can reduce overall contrast administration and radiation dose.

Tricuspid Regurgitation in Patients With Pacemakers and Implantable Cardiac Defibrillators: A Comprehensive Review

Implantable cardiac devices, including defibrillators and pacemakers, may be the cause of tricuspid regurgitation (TR) or may worsen existing TR. This review of the literature suggests that TR usually occurs over time after lead implantation. Diagnosis by clinical exam and 2‐dimensional echocardiography may be augmented by 3‐dimensional echocardiography and/or computed tomography. The mechanism may be mechanical perforation or laceration of leaflets, scarring and restriction of leaflets, or asynchronized activation of the right ventricle. Pacemaker‐related TR might cause severe right‐sided heart failure, but data regarding associated mortality are lacking. This comprehensive review summarizes the data regarding incidence, mechanism, and treatment of lead‐related TR.

Manual, semiautomated, and fully automated measurement of the aortic annulus for planning of transcatheter aortic valve replacement (TAVR/TAVI): Analysis of interchangeability

BACKGROUND Preprocedural 3-dimensional CT imaging of the aortic annular plane plays a critical role for transcatheter aortic valve replacement (TAVR) planning; however, manual reconstructions are complex. Automated analysis software may improve reproducibility and agreement between readers but is incompletely validated. METHODS In 110 TAVR patients (mean age, 81 years; 37% female) undergoing preprocedural multidetector CT, automated reconstruction of the aortic annular plane and planimetry of the annulus was performed with a prototype of now commercially available software (syngo.CT Cardiac Function-Valve Pilot; Siemens Healthcare, Erlangen, Germany). Fully automated, semiautomated, and manual annulus measurements were compared. Intrareader and inter-reader agreement, intermodality agreement, and interchangeability were analyzed. Finally, the impact of these measurements on recommended valve size was evaluated. RESULTS Semiautomated analysis required major correction in 5 patients (4.5%). In the remaining 95.5%, only minor correction was performed. Mean manual annulus area was significantly smaller than fully automated results (P < .001 for both readers) but similar to semiautomated measurements (5.0 vs 5.4 vs 4.9 cm(2), respectively). The frequency of concordant recommendations for valve size increased if manual analysis was replaced with the semiautomated method (60% agreement was improved to 82.4%; 95% confidence interval for the difference [69.1%-83.4%]). CONCLUSIONS Semiautomated aortic annulus analysis, with minor correction by the user, provides reliable results in the context of TAVR annulus evaluation.

Ventricular septal rupture complicating acute myocardial infarction: a contemporary review.

Ventricular septal rupture (VSR) after acute myocardial infarction is increasingly rare in the percutaneous coronary intervention era but mortality remains high. Prompt diagnosis is key and definitive surgery, though challenging and associated with high mortality, remains the treatment of choice. Alternatively, delaying surgery in stable patients may provide better results. Prolonged medical management is usually futile, but includes afterload reduction and intra-aortic balloon pump placement. Using full mechanical support to delay surgery is an attractive option, but data on success is limited to case reports. Finally, percutaneous VSR closure may be used as a temporizing measure to reduce shunt, or for patients in the sub-acute to chronic period whose comorbidities preclude surgical repair.

Predicting vascular complications during transfemoral transcatheter aortic valve replacement using computed tomography: a novel area-based index.

Computed tomography (CT) imaging has not been systematically studied for predicting vascular complications during transcatheter aortic valve replacement (TAVR).

The Use and Limitations of Unfractionated Heparin

Despite the development of newer anticoagulants, unfractionated heparin remains an indispensible agent in the treatment of thrombotic disorders. Heparin exerts its major effect via antithrombin, converting antithrombin to a more efficient inhibitor of circulating thrombin (factor IIa), factor Xa, factor IXa, factor XIIa, and kallikrein. However, due to the multiple anticoagulant mechanisms of heparin, differential molecular weight-based clearance, issues of heparin resistance, and patient-specific characteristics (age, weight, gender, and tobacco), attaining therapeutic anticoagulation is complicated. As a result, a minority of patients in major clinical trials achieve an activated partial thromboplastin time within the target window in an appropriate time-frame despite the use of weight-based titration nomograms. The resultant under- or over-therapeutic anticoagulation is associated with increased risks of ischemic and bleeding complications, suggesting the importance of maintaining heparin anticoagulation within a relatively narrow therapeutic range. In this review we discuss the mechanisms of heparin action, clinical ramifications of incorrect dosing in major trials, and attempts to improve the achievement of therapeutic anticoagulation.

Clinical cerebrovascular anatomy

Stroke is often the result of carotid atheroma, which may cause ischemia via progressive arterial narrowing or lead to superimposed thrombus formation and subsequent atheroembolism to the intracerebral vasculature. Revascularization through carotid endarterectomy or carotid artery stenting with embolic protection devices has produced favorable results in appropriately selected patients. In planning the percutaneous approach, an arch aortogram is first acquired to determine arch type and identify the presence of any anatomic variants which may affect the approach to the procedure and catheter selection. Subsequent imaging of the cerebral vasculature is performed to delineate the collateral circulation that is present, including an evaluation of the Circle of Willis. Although Doppler ultrasound, computed tomography (CT), and magnetic resonance angiography (MRA) may be useful in evaluating the presence of carotid or cerebrovascular disease, digital subtraction angiography is required prior to performance of a percutaneous intervention in order to create a procedural “roadmap”. Additionally, the comprehensive management of cerebrovascular disease requires a detailed knowledge of the specific clinical syndromes that result from ischemia in each vascular territory. This methodical review of cerebrovascular anatomy and stroke syndromes will provide the operator with the tools to conduct a thorough neurological assessment prior to revascularization, evaluate any periprocedural complications that may arise, and evaluate the patient with suspected stroke.

Integration of MDCT and fluoroscopy using C-arm computed tomography to guide structural cardiac interventions in the cardiac catheterization laboratory

Our study was aimed at evaluation of three‐dimensional (3D)‐CT overlay onto the catheterization laboratory fluoroscopy to guide structural cardiac interventions. Background: Current imaging for structural cardiac interventions (fluoroscopy, echocardiography) may not provide adequate guidance. The ability to integrate intracardiac 3D‐CT imaging data in the cardiac catheterization laboratory may be beneficial, but has not yet been systematically studied.

Update on Transcatheter Aortic Valve Implantation

Aortic stenosis affects a significant number of patients worldwide, and carries a dismal prognosis once symptoms develop. Unfortunately, a large number of patients present a prohibitive risk for surgical aortic valve replacement. Therefore, transcatheter aortic valve implantation has emerged as a promising technology for providing treatment to this group of patients. Currently available valves include the balloon-expandable Edwards SAPIEN valve (Edwards Lifesciences, Irvine, CA), which is usually implanted via a transfemoral or transapical approach, and the self-expanding CoreValve ReValving system (Medtronic, Minneapolis, MN), which uses only the transfemoral route. Early experience with the procedure performed on a compassionate-use basis was encouraging, and led to a number of first-in-man and feasibility studies. These trials demonstrated the safety and efficacy of valve implantation and led to CE (European Conformity) mark approval of both valves in Europe. Use of the SAPIEN valve in the United States is limited to the recently completed PARTNER (Placement of Aortic Transcatheter Valve) randomized trial comparing transcatheter and surgical aortic valve replacement in high-risk patients, and its post-trial registry. The CoreValve is not yet available in the United States. With improved device technology, better understanding of patient selection and pre- and periprocedural imaging, and greater procedural experience, widespread diffusion of transcatheter aortic valve implantation is expected.